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276 Cards in this Set
- Front
- Back
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what are the three forces that are responsible for the venous movement of blood against gravity?
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1. valves
2. skeletal muslce 3. respiratory pump/cycle |
|
what is pulse pressure?
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difference between systolic and diastolic pressure
|
|
what percent of blood is found in the veins?
|
60%
|
|
what are the four factors that affect blood flow?
|
1. difference in pressure (pressure gradient)
2. length of vessel 3. diameter of vessel 4. viscosity (determined by concentration of RBC) |
|
what are the factors that affect blood pressure?
|
cardiac output
blood volume resistance (length, distance, viscosity) condition of arteries (arthrosclerosis) |
|
what are the two branches of the nervous system?
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Central
Peripheral |
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what does the CNS consist of?
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brain and spinal cord
|
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what does the PNS consist of?
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afferent (sensory) neurons and efferent neurons
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CNS neurons integrate information that arrives from the ________ branch of the ____.
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CNS neurons integrate information from the afferent branch of the PNS and determine whether a response is needed.
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efferent neurons are subdivided into what two divisions?
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somatic motor division and autonomic division
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what is the enteric nervous system?
|
a third division of the nervous system comprised of a network of neurons in the walls of the digestive tract.
|
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how is the enteric nervous system controlled?
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by the autonomic division of the PNS and autonomously
|
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what is the functional unit of the nervous system?
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the neuron
|
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what are the three functional classifications of neurons?
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sensory (afferent) neurons, efferent neurons, and interneurons
|
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which part of a neurons receives input?
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dendrite
|
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which part of a neuron is responsible for signal output?
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axon
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what is an interneuron?
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a neuron that lies entirely within the CNS (brain or spinal cord).
|
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what do sensory (afferent) neurons do?
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carry information about temperature, pressure, light, and other stimuli from afferent receptors to the CNS
|
|
what is the enteric nervous system?
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a third division of the nervous system comprised of a network of neurons in the walls of the digestive tract.
|
|
how is the enteric nervous system controlled?
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by the autonomic division of the PNS and autonomously
|
|
what is the functional unit of the nervous system?
|
the neuron
|
|
what are the three functional classifications of neurons?
|
sensory (afferent) neurons, efferent neurons, and interneurons
|
|
which part of a neurons receives input?
|
dendrite
|
|
which part of a neuron is responsible for signal output?
|
axon
|
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what is an interneuron?
|
a neuron that lies entirely within the CNS (brain or spinal cord).
|
|
what do sensory (afferent) neurons do?
|
carry information about temperature, pressure, light, and other stimuli from afferent receptors to the CNS
|
|
what is a nerve?
|
a bundle of axons form both efferent and afferent peripheral neurons.
nerves extend from the CNS to the targets of the component neurons |
|
what are the three types of neurons?
|
efferent, afferent (sensory) and interneurons
|
|
what is an interneuron?
|
a neuron that lies completely within the CNS (brain or spinal cord)
|
|
what are the 2 types of glial cells in the PNS?
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schwann cells and satellite cells
|
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what are the 4 types of glial cells in the CNS?
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oligodendrocytes, microglia, astrocytes, and ependymal cells
|
|
which glial cells produce myelin?
|
schwann cells in the PNS &
oligodendrocytes in the CNS |
|
what is the main function of glial cells?
|
to provide structural support to neurons since neurons do not have much ECM
|
|
what is a chief difference between myelin secreting schwann cells and oligodendrocytes?
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schwann cells are in the PNS and oligodendrocytes are in the CNS.
in the CNS, oligodendrocytes associate with several axons but in the PNS a single schwann cell myelinates a single neuron. |
|
what is a ganglion?
|
a cluster of nerve cell bodies found outside the CNS
|
|
what is a cluster of nerve cell bodies called when located within the CNS? Outside of the CNS?
|
within the CNS - a nucleus
outside the CNS -a ganglion |
|
what do satellite cells do?
|
they are nonmyelinating PNS glial cells that provide support to neural cell bodies in ganglia
(ganglia are clusters of nerve cell bodies found outside the CNS) |
|
what are astrocytes? what are their 4 primary functions?
|
nonmyelinating CNS glial cells found in the brain in high concentration! ~50% of brain cells
1) communicate thru gap junctions 2) take up and release chemicals 3) provide neurons with substrates for ATP production 4) participate in blood-brain barrier |
|
what are microglia?
|
CNS glial cells that serve an immune function
can be harmful to body by releasing ROS which form free radicals (implicated in ALS) |
|
what are ependymal cells?
|
CNS glial cells that create the selectively permeable epithelial layer called the ependyma that separates the fluid compartments in the brain and is a source of neural stem cells (which differentiate into glial cells or neurons)
|
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what are the two factors that influence RMP?
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1. concentration gradient of ions across membrane
2. membrane permeability to those ions |
|
what does the nernst equation determine?
|
the equilibrium potential of any one ion- that is, the membrane potential that a single ion would produce if the membrane were permeable only to that one ion
|
|
what does the GHK equation determine?
|
the resting membrane potential (RMP) that results from the contribution of all ions that can cross the membrane
|
|
RMP of living cells is primarily determined by what?
|
K+ concentration gradient and the cell's resting permeability to K+, Na+, and Cl-.
|
|
what affect does the addition of Na+ to the intracellular fluid have on the cell membrane?
|
the cell membrane is depolarized and an electrical signal is generated
|
|
if a cell membrane becomes more permeable to K+ what happens?
|
positive charge is lost from within the cell and the membrane is hyperpolarized (more negative)
|
|
when the cell membrane becomes more + and less - it is said to be what?
|
depolarized
|
|
when the cell membrane becomes more - and less + it is said to be what?
|
hyperpolarized
|
|
if a cell membrane increases permeability to Na+, what happens to the cell membrane?
|
the cell is depolarized
|
|
what are the four major selective ion channels in neurons?
|
1. Na+ channels
2. K+ channels 3. Ca2+ channels 4. Cl- channels |
|
what is threshold voltage?
|
minimum stimulus for channel opening
|
|
Both Na+ and K+ channels of axons are activated by what?
|
cell depolarization (more +, less -)
|
|
what are the two types of electrical signals?
|
1. graded potential
2. action potential |
|
what are the defining characteristics of graded potentials and action potentials?
|
1. graded potentials travel short distances, vary in strength, and lose strength as they travel.
2. action potentials travel long distances and do not lose signal strength as they travel |
|
what is the function of action potentials?
|
rapid signaling over long distances
|
|
what effect does the retention of K+ have on the cell membrane?
|
depolarizing
|
|
what are graded potentials?
|
depolarizations or hyperpolarizations that occur in the dendrites and cell body of a neuron ( & less frequently near the axon terminal)
size is proportionate to stimulus |
|
why do graded potentials lose strength as they move through the cytoplasm?
|
1. current leak
2. cytoplasmic resistance |
|
where is the trigger zone in efferent neurons and interneurons?
|
the axon hillock and the very first part of the axon called the initial segment
|
|
where is the trigger zone in sensory neurons?
|
immediately adjacent to the receptor, where the dendrite joins the axon.
|
|
an inhibitory graded potential is what?
|
hyperpolarizing (more -, less +) less likely to fire action potential
|
|
an excitatory graded potential is what?
|
depolarizing (more +, less -) more likely to fire an action potential
|
|
what must happen for an action potential to be initiated by a graded potential?
|
the graded potential must be strong enough to reach trigger zone of neuron and depolarize the membrane to threshold voltage, opening voltage-gated Na+ channels to initiate AP
|
|
what is the trigger zone of a neuron?
|
the integrating center of a neuron that contains a high concentration of voltage-gated sodium channels in membrane
|
|
what is a cell's excitability?
|
the ability of a neuron to respond rapidly to a stimulus and fire an action potential
|
|
does the strength of the graded potential affect the strength of the action potential it initiates?
|
no, as long as it is over threshold voltage!! action potential depolarization is always ~-100mV!! 'all or none phenomena'
|
|
what two types of gated ion channels are required to generate an action potential?
|
1. Na+ gated
2. K+ gated (plus some leak channels that help reset RMP) |
|
why/how do the sodium channels close while the cell membrane is depolarized during an AP?
|
they have two gates to regulate ion movement known as activation and inactivation gates
|
|
at RMP, what position are the activation and inactivation gates on the voltage gated sodium channel in?
|
activation -closed
inactivation- open |
|
what happens to the activation/inactive gates of the sodium channel when the cell membrane depolarizes?
|
activation gate opens allowing Na+ into cell, positive feedback keeps gates open until the time-delayed inactivation gates that were also stimulated, close and the AP peaks. the sodium channel gates reset themselves during re-polarization.
|
|
ultimately, what causes the refractory period to occur?
|
the double gating of sodium channels
|
|
what is the absolute refractory period?
|
the time required for the sodium channels to reset their gates to starting positions following AP.
|
|
what is the consequence of having double-gated sodium channels that result in an absolute refractory period in which no AP can be fired?
|
action potentials moving from trigger zone to axon terminal cannot overlap and cannot travel backwards.
|
|
what is the relative refractory period?
|
when not all of the sodium gates have reset
|
|
why do any action potentials that fire during the relative refractory period have a smaller amplitude than normal?
|
because although sodium can enter through the gates that are opened by the higher than normal depolarizing stimulus, K+ channels are also open and K+ is leaving cell, offsetting Na+ entry.
|
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if all action potentials are the same (which they are) then how does the neuron transmit information about the strength and duration of the stimulus that initiated the AP?
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increase in stimulus intensity (strength) is represented by an increase in frequency of action potentials
|
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what role does the sodium potassium pump play in nerve impulses?
|
restoration of ion concentrations (Na+ and K+) following an AP
|
|
what are the two physical parameters that influence speed of action potential?
|
1.) diameter of axon
2.) resistance of axon membrane to ion leakage (decreased in myelinated cells) larger, myelinated cells conduct AP fastest. |
|
what is saltatory conduction?
|
the "jump" from one node of ranvier to another in mylenated neurons
|
|
how are the enzymes needed for neurotransmitter release brought from the cell body where they are synthesized to the axon terminal?
|
slow axonal transport
|
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how are the neurotransmitters synthesized in the cell body brought to the axon terminal for release?
|
fast axonal transport
|
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how do neurotoxins that block the release of neurotransmitters (like botulinum and tetanus) work?
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by inhibiting specific proteins of the cell's exocytotic apparatus.
|
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what ion is required for neurotransmitter release into the synaptic cleft?
|
calcium! calcium gated ion channels open in response to depolarization and calcium enters neuron and initiates exocytosis of neurotransmitters
|
|
what are the seven classes of neurocrines?
|
acetylcholine
amino acids amines purines peptides lipids gases |
|
what are the three major neurocrines secreted by the PNS?
|
epinephrine, norepinephrine and acetylcholine
|
|
dopamine, norepinephrine and epinephrine, histamine and serotonin are what class of neurocrine?
|
amine
|
|
neurons that secrete ACh and receptors that bind ACh are called what?
|
cholinergic
|
|
neurons that secrete norepinephrine are called what?
|
adrenergic neurons
|
|
what are the four AA's that function as neurotransmitters in the CNS?
|
glutamate
asparate GABA glycine |
|
what is the primary excitatory neurotransmitter of the CNS?
|
glutamate
|
|
what is the primary inhibitory neurotransmitter in the brain?
|
GABA
|
|
what is the primary inhibitory n.transmitter of the spinal cord?
|
glycine
|
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opioid peptides (endorphins), vasopressin, substance p, etc. are examples of which class of neurocrine?
|
peptides
|
|
what are some examples of purine neurocrines?
|
AMP and ATP
(bind to purinergic receptors) |
|
what is the neural plate?
|
flattened region of cells destined to become the nervous system (in embryonic development)
|
|
what are the seven major divisions of the CNS present at birth?
|
1. the cerebrum
2. diencephalon 3. midbrain 4. cerebellum 5. pons 6. medulla oblongata 7. spinal cord |
|
the cerebellum, pons and medulla oblongata develop are divisions of what?
|
hindbrain
|
|
the cerebrum and pons develop from what?
|
the forebrain
|
|
what is the blood brain barrier?
|
a functional barrier between the interstitial fluid and the blood.
the barrier is made up of brain capillaries that are less permeable than other capillaries and protect the brain from exposure to pathogens in blood, changes in ions, hormones, and neurotransmitters. |
|
why are brain capillaries so much less permeable than other capillaries in the body?
|
because of tight junctions that prevent movement of solutes between cells
|
|
what causes tight junction formation in brain capillaries?
|
paracrine signals from adjacent astrocytes
|
|
where is dopamine formed?
|
area of the midbrain called substantia nigra
|
|
the blood-brain barrier will allow lipid soluble molecules or water soluble molecules to cross?
|
lipid soluble!
|
|
which parts of the brain lack the blood-brain barrier?
|
the hypothalamus and the vomiting center in the medulla oblongata
|
|
what are the metabolic requirements of the brain?
|
the neurons in the brain have an increased requirement for oxygen and glucose for the production of ATP for active transport of ions and neurotransmitters
|
|
why do the neurons in the brain have increased oxygen and glucose requirements?
|
to produce ATP needed for actiev transport of ions and neurotransmitters
|
|
how do the neurons of the brain meet their increased metabolic needs?
|
oxygen flows freely over blood-brain barrier, but glucose is transported across barrier by membrane transporters.
|
|
what is the spinal reflex arc?
|
sensory information passes from a sensory neuron through the gray matter to an efferent neuron (does not require input from the brain!)
|
|
what does the brain stem consist of?
|
medulla oblongata, pons and midbrain
|
|
crossing of corticospinal tracts in which part of the brain accounts for each side of the brain controlling the opposite side of the body?
|
a region called the pyramids in the medulla oblongata
|
|
what is the primary function of the pons?
|
to act as a relay station for information transfer between the cerebrum and the cerebellum
|
|
what two parts of the brain control breathing?
|
pons and medulla
|
|
what is the main function of the midbrain?
|
eye movement and to relay signals for auditory and visual reflexes
|
|
which part of the brain processes sensory information and coordinates the execution of movement?
|
the cerebellum
|
|
what makes up the diencephalon?
|
the thalamus and hypothalamus (and the pineal and pituitary endocrine glands)
|
|
what does the hypothalamus do?
|
it is the center for homeostasis; hunger and thirst drives, etc.
|
|
what does the thalamus do?
|
relays sensory information from the optic tract, ears, spinal cord, and motor info. from cerebellum to cerebrum where it is processed
|
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the cerebrum is comprised of two hemispheres connected primarily at the ...
|
corpus callosum (formed from axons passing from one side of the brain to the other)
|
|
what are the four lobes of the cerebrum?
|
occipital
frontal parietal temporal |
|
what are the three major regions in the gray matter of the cerebrum?
|
cerebral cortex
basil ganglia limbic system |
|
which regions of the brain is responsible for emotion and memory?
|
the amygdala and cingulate gyrus in the limbic system of the cerebrum
|
|
which region of the brain is responsible for learning and memory?
|
the hippocampus in the limbic system of the cerebrum
|
|
which part of the cerebrum controls movement?
|
basil ganglia
|
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which part of the cerebrum controls higher brain functions?
|
the cerebral cortex
|
|
what is the primary function of the limbic system?
|
to integrate/link higher thinking to primitive emotional responses like fear
|
|
what are the three parts of the limbic system?
|
amygdala, cingulate gyrus, and the hippocampus
|
|
what neurotransmitter is responsible for controlling motor function?
|
dopamine
|
|
the cerebral cortex in organized into three functional areas. what are they?
|
sensory areas (awareness)
motor areas (skeletal muscle movement) association areas (integrate sensory and motor areas to direct voluntary behaviors) |
|
what is cerebral lateralization?
|
left brain-right brain dominance: the fact that functional specialization is not symmetrical across the cerebral cortex
|
|
what is RAS?
|
reticular activating system: collection of neurons that determines consciousness/sleep wake cycle
|
|
regardless of whether someone is right-handed or left-handed, which side of the brain is most often used in language/speech?
|
left brain
|
|
what part of the brain controls speech?
|
cerebral cortex of cerebrum
(specifically, Wernicke's area and Broca's area) |
|
communicating through speech is divided into what two processes?
|
1. combination of different sounds to form words (vocalization) and
2. combination of words into grammatically correct/meaningful sentences |
|
what specific part of the brain controls the integration of spoken language?
|
Wernicke's area in the temporal lobe of cerebrum and Broca's area in the frontal lobe
|
|
what effect does damage to Wernicke's area have on language?
|
can not understand words of language (heard or read) called receptive aphasia
|
|
what effect does damage to Broca's area have on language?
|
can not use language effectively, but still understand it. called expressive aphasia
|
|
where are Broca's area and Wernicke's area?
|
in the cerebral cortex of cerebrum- usually in the left brain
|
|
what percent of blood pumped by heart ends up delivering oxygen to the brain?
|
15%
|
|
the ANS is made up of what?
|
the sympathetic and parasympathetic branches
|
|
what is an example of a key function of the sympathetic branch of the ANS?
|
regulation and control of blood flow to tissue
also, "fight of flight" response |
|
what three parts of the brain are most important in homeostatic regulation?
|
hypothalamus, pons, medulla
|
|
how does the ANS work in coordination with the brain to maintain homeostasis?
|
sensory information is sent from the somatosensory and visceral receptors to homeostatic control centers in the hypothalamus, pons and medulla initiating autonomic, endocrine, and behavioral responses
|
|
most organs in the body are regulated by dual antagonistic innervation. what are some exceptions?
|
sweat glands and smooth muscle of blood vessels is controlled only by sympathetic branch of ANS!
|
|
all autonomic pathways consist of how many efferent neurons in series?
|
two -the preganglionic and postganglionic neurons
|
|
what is a neuroeffector junction?
|
the synapse between a postganglionic autonomic neuron and its target cell
|
|
how do the two autonomic branches (sympathetic & parasympathetic) differ anatomically?
|
1. point of origin in the CNS
2. location of the autonomic ganglia |
|
most sympathetic pathways originate from where?
|
the thoracic and lumbar regions of the spinal cord
|
|
most pararsympathetic pathways originate from where?
|
the brain stem or the sacral region of the spinal cord
|
|
most sympathetic ganglia are found where?
|
in two chains on either side of the vertebral column
|
|
where are parasympathetic ganglia found?
|
on or near their target tissue
|
|
what is the anatomical consequence of parasympathetic ganglia being on or near their target tissue?
|
parasympathetic preganglionic neurons have long axons and parasympathetic postganglionic neurons have short axons
|
|
what is the anatomical consequence of sympathetic ganglia being close to the vertebral column/spinal cord?
|
sympathetic preganglionic neurons have short axons; sympathetic postganglionic neurons have long axons
|
|
parasympathetic innervations goes primarily to where?
|
the head, neck, and internal organs.
|
|
what is the major parasympathetic tract?
|
the vagus nerve, which carries both sensory information from the internal organs to the brain and parasympathetic output from the brain to organs.
|
|
both sympathetic and parasympathetic preganglionic neurons release ____________ onto _________ cholinergic receptors on the postganglionic cell.
|
both sympathetic and parasympathetic preganglionic neurons release acetylcholine onto nicotinic cholinergic receptors on the postganglionic cell.
|
|
what neurotransmitter do most postganglionic sympathetic neurons secrete? what receptor on target cell is involved?
|
norepinephrine is secreted by most postganglionic sympathetic neurons. norepinephrine binds to adrenergic receptors on target cell
|
|
what neurotransmitter do most postganglionic parasympathetic neurons secrete? to what receptor on the target cell does this chemical bind?
|
acetylcholine -binds to muscarinic cholinergic receptors on the target cell
|
|
what is the parasympathetic response on the bladder?
|
release urine
|
|
what is a varicosity?
|
a swelling at the end of a postganglionic autonomic axon that contains vesicles filled with neurotransmitter and mitochondria
|
|
what are the primary autonomic neurotransmitters? where are they synthesized?
|
ACh and NE -both synthesized in axon varicosities by cytoplasmic enzymes
|
|
how are NE and ACh released from varicosity in ANS?
|
in the typical fashion- AP arrives at the varicosity, voltage gated Ca+ channels open, Ca+ enters the neuron and synaptic vesicle contents (neurotransmitter) released by exocytosis and diffuse to receptors/away from synapse
|
|
how do muscarinic cholinergic receptors work?
|
G-protein coupled receptors that use second messenger pathways to K and Ca channels
|
|
give an example of where muscarinic receptors are utilized?
|
in the parasympathetic division of the ANS -the postganglionic neuron secretes ACh into neuroeffector junction where it binds to muscarinic cholingeric receptors on target tissue
|
|
what are the two types of adrenergic receptors?
|
alpha and beta
|
|
how do adrenergic receptors work?
|
through G protein coupled receptors and second messenger system
|
|
regarding autonomic neurons- does more neurotransmitter in the synapse mean a longer/stronger response? what is this dependent on?
|
yes!! dependent on the rate of breakdown or removal!
|
|
in ANS when is neurotransmitter activation of it's receptor terminated?
|
neurotransmitter either
1. diffuses away 2. is metabolized by enzymes in ECF 3. is actively transported into cells around synapse |
|
the uptake of neurotransmitter by varicosities allows what?
|
neurons to recycle chemicals
|
|
what is the main enzyme responsible for degradation of catecholamines? (NE)
Hint: inside the neuron, recycled NE is either repackaged in vesicle or broken down by .... |
monoamine oxidase
|
|
what type of transmitter binds to adrenergic receptors in sympathetic NS?
|
catecholamines -NE and E
|
|
which is the most common sympathetic receptor?
|
alpha adrenergic -responds strongly to NE but only weakly to E
|
|
how do the 3 subtypes of beta receptors differ?
|
in their affinity for catecholamines
|
|
which of the adrenergic beta receptors are found mostly on adipose tissue? do they respond better to NE or E?
|
B3- they are more sensitive to NE
|
|
which adrenergic beta receptor has no sympathetic innervation? more sensitive to NE or E?
|
B2- more sensitive to E
|
|
which adrenergic beta receptor is equally sensitive to both E and NE?
|
B1
|
|
is the adrenergic alpha receptor more sensitive to NE or E?
|
NE! !
|
|
what is the consequence of a receptor using a Gprotein/2nd messenger system instead of direct ion channel activation as seen in nicitonic cholinergic receptors?
|
Gprotein linked/2nd mess. receptors are slower to respond but the response lasts longer
|
|
binding to beta adrenergic receptors results in an increase in CAMP through second messenger. What is the overall effect?
|
phosphorylation of intracellular proteins
|
|
binding to alpha 1 adrenergic receptors activates phospholipase c via second messenger. What is the overall effect?
|
IP3 and DAG are created- IP3 opens Ca channels, DAG phosphorylates proteins
muscle contraction or exocytosis |
|
binding to adrenergic alpha 2 results in a decrease in CAMP via second messenger. What is the overall effect?
|
smooth muscle relaxation
|
|
binding to beta 1 has what effect? beta 2?
|
beta 1 increases cardiac muscle contraction
beta 2 relaxes smooth muscle of blood vessels |
|
tendons connect what?
|
muscle to bone
|
|
what is an antagonistic muscle group?
|
flexor-extensor pair (triceps-biceps)
|
|
what is the contractile structure of muscle fiber?
|
myofibril (highly organized bundle of contractile and elastic proteins responsible for contraction)
|
|
what is the sacrolemma?
|
cell membrane of muscle cell
|
|
what is the sarcoplasm?
|
cytoplasm of muscle cell
|
|
what is the sacroplasmic reticulum?
|
ER of muscle cell
|
|
what types of protein are within a myofibril?
|
myosin & actin (contractile proteins)
tropomyosin & troponin (regulatory proteins) titin & nebulin (accessory proteins) |
|
thick filaments are composed of -?
|
myosin
|
|
thin filaments are composed of -?
|
actin
|
|
what does a neuromuscular junction consist of?
|
axon terminals from somatic motor neuron, the synaptic cleft, and the motor end plate on the muscle fiber
|
|
what is a rigor state?
|
when myosin heads are tightly bound to actin
|
|
what is excitation-contraction coupling?
|
the electrical and mechanical events in a muscle fiber at the neuromuscular junction
|
|
what are the four main events of EC coupling?
|
1. ACh is released from somatic motor neuron
2. Ach initiates AP in muscle fiber 3. muscle AP triggers calcium release from sacroplasmic reticulum 4. calcium combines with troponin and initiates contraction |
|
what is the motor end plate?
|
region of muscle membrane that contains a high amount of ACh receptors (involved in neuromuscular junction)
|
|
what type of receptors are in the motor end plate?
|
nicotinic cholinergic receptors
|
|
what is the overall effect of EC coupling?
|
conversion of an electrical signal into a calcium signal
|
|
what is a muscle twitch?
|
a single contraction-relaxation cycle in skeletal muscle
|
|
what is a latent period?
|
the delay between the muscle AP and the beginning of muscle contraction -represents time it takes for EC coupling to occur!
|
|
where do muscles get the ATP they need?
|
phosphocreatine, carb and fatty acid metabolism
|
|
the speed that a muscle fiber can contract is determined by what?
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the isoform of myosin ATPase in the fiber's thick filaments and the rate at which Ca is removed from cytosol to reset for subsequent contraction
(fast-twitch fibers split ATP faster than slow twitch fibers and remove Ca from cytosol quicker) |
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what are the two main factors that differ between fast and slow twitch fibers?
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1. SPEED isoform of myosin ATPase in thick filaments (speed at which contraction cycles can be completed), how fast Ca is removed from cytosol in preparation for second contraction (determines the speed at which a second contraction can occur)
2. RESISTANCE TO FATIGUE -glycolytic fibers (fatigue quickly) vs. oxidative fibers ( resist fatigue ) |
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what does the sliding filament theory predict?
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that the tension a muscle fiber can generate is directly proportional to the number of crossbridges between thick and thin filaments
|
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what is occurring in a contraction that allows a single twitch to occur?
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the muscle relaxes completely between stimuli
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what is unfused or incomplete tetanus?
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stimuli are far enough apart to allow muscle to relax slightly between stimuli
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what is complete tetanus?
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stimulation rate is fast enough that muscle fiber does not have time to relax
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the force of contraction in a skeletal muscle can be increased how?
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recruitment! of additional motor units -weak stimulus selectively activates low-threshold neurons, and as stimulus increases, neurons with higher threshold are recruited accordingly
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in recruitment (increasing force of muscle contraction in a muscle composed of many motor units), what is the order of neurons/fibers recruited in order of increasing stimulus strength?
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weak stimulus= slow twitch oxidative (fatigue resistant slow twitch)
med. stim = fast twitch oxidative-glycoytic (fatigue restant fast twitch) max stim = fast twitch glycolytic (quick to fatigue, but provide max force) |
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any contraction that creates force and moves a load is called an
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isotonic contraction
|
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any contraction that creates force without moving a load is called an
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isometric contraction
|
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if a muscle contracts and does NOT shorten what type of contraction occurred?
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isometric
|
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if a muscle contracts and shortens what type of contraction occurred?
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isotonic
|
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what causes a muscle cramp?
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hyperexcitability of the somatic motor neurons controlling the muscle
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what is the action of botulinum toxin?
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decreases the release of ACh from somatic motor neuron
|
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what is muscle atrophy?
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after prolonged inactivity -blood supply to muscle diminishes and fibers shorten
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what is a tonically contracted muscle?
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muscles that maintain tension most of the time -they relax only to let something enter/exit organ (bladder, esophagus)
|
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what are some differences between smooth muscle and skeletal muscle?
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smooth muscle is mononucleated, skeletal is multinucleated
smooth fibers are smaller than skeletal smooth muscle does not have sacromeres smooth muscle lacks specialized receptor such as the motor end plate found in skeletal muscle- neurotransmitter just diffuses to find receptor in smooth smooth muscle contractions are slower |
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what is the difference in how contraction force is varied in muti-unit and single-unit smooth muscle?
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single-unit smooth muscle contraction force increases with increased Ca
multi-unit contraction force increases with recruitment of additional fibers (like in skeletal muscle) |
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are smooth muscle contractile proteins arranged in sacromeres?
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NO! reason for smooth appearance
|
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does skeletal or smooth muscle have longer actin/myosin filaments?
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smooth muscle has longer actin/myosin filaments
|
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what is the actin:myosin ratio in smooth muscle? skeletal muscle?
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smooth 10-15: 1 (actin: myosin)
skeletal 2-4: 1 (actin: myosin) |
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which has more actin, smooth or skeletal?
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smooth (10-15:1) actin:myosin
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smooth muscle lacks...?
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troponin
|
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what is myosin light chain?
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a small regulatory protein found in SMOOTH muscle that controls contraction and relaxation
|
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what is the primary source of calcium release in smooth muscle? skeletal?
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IP3 receptor channel -smooth
DHP-Ryr in skeletal |
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the calcium storage function of the SR may be supplemented in smooth muscle by what? (because smooth muscle has less SR)
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caveolae- small vesicles that cluster close to cell membrane
|
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name three ways smooth muscle myosin differs from skeletal myosin?
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smooth muscle myosin is longer, has myosin heads the entire length of the filament, and has slower ATPase activity
|
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name a way smooth muscle actin and its associated proteins differ in smooth and skeletal muscle?
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smooth muscle actin is longer and lacks troponin
there are more actin filaments in smooth muscle |
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are there more actin filaments in skeletal or smooth muscle?
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smooth
|
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in both smooth and skeletal muscle, what triggers contraction?
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Ca
|
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in skeletal muscle, the calcium signal that initiates an action potential comes from where? what always precedes the release of calcium?
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DHP/Ryr regulated release from sacroplasmic reticulum, preceded by an AP !!
|
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in smooth muscle, the calcium signal that initiates contraction comes from where? is an AP required for the release of calcium?
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Ca comes from IP3 regulated release from SR .. & from ECF!
|
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where does the Ca signal come from in smooth muscle? skeletal?
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smooth- SR and ECF (does not require AP)
skeletal- SR (requires AP) |
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smooth muscle contraction is primarily controlled through _______-linked regulatory processes, rather than troponin and tropomyosin (skeletal)
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myosin-linked regulation (Ca binding to calmodulin, activating myosin light chain kinase ...)
|
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what is myogenic contraction?
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contraction of smooth muscle in blood vessels with stretch activated Ca channels, to remain tone (causes contraction of self)
|
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how can a neuron alter the amount of neurotransmitter it releases?
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increase in frequency of stimuli = increase in strength of stimuli = increase in amount of neurotransmitter released
|
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does cardiac muscle have sacromeres?
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yes, not smooth
|
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which muscle types have sacromeres?
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skeletal and cardiac
|
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which muscle type is multinucleated?
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skeletal
|
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which muscle types are electrically linked to one another through gap junctions?
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cardiac and single-unit smooth muscle
|
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in cardiac muscle where are the gap junctions contained?
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intercalated discs
|
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which muscle types are subject to hormonal control?
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smooth and cardiac
|
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which muscle type is controlled by the somatic division of the PNS?
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skeletal
|
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which muscle types are controlled by the autonomic (sympathetic and parasympathetic) division of the PNS?
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cardiac and smooth
|
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what do reflex pathways in the nervous system consist of?
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networks of neurons that link sensory receptors to muscles or glands (effectors)
|
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reflexes that involves somatic motor neurons and skeletal muscles are known as ...
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somatic reflexes
|
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reflexes whose responses are controlled by autonomic neurons are called...
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autonomic reflexes
|
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what is a spinal reflex?
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a reflex that is integrated in the spinal column- can occur without input form brain
|
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what is a cranial reflex?
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a reflex integrated in the brain
|
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what is a monosynaptic reflex?
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composed of only an afferent neuron, single synapse in spinal cord, and an efferent neuron.
(the simplest reflex) |
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what two things are true of all autonomic reflexes?
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1) they are all polysynaptic
2) have at least one synapse in the CNS and another in the autonomic ganglion |
|
autonomic reflexes are AKA..
|
visceral reflexes
|
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skeletal muscle reflexes have what five components?
|
1. proprioceptors (sensory receptors)
2. sensory neurons 3. CNS (for integration) 4. somatic motor neurons 5. effectors (muscle fibers: extrafusal muscle fibers) |
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the somatic motor neurons that innervate skeletal muscle contractile fibers are called what?
|
alpha motor neurons
|
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what is the effector in a skeletal muscle reflex?
|
extrafusal muscle fibers (innervated by alpha motor neurons)
|
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which proprioceptors lie within skeletal muscle?
|
golgi tendon organs and muscle spindles
|
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what is a golgi tendon organ?
|
one of the three proprioceptors in skeletal muscle- found at the junction of tendons and muscle fibers and responds primarily to the tension that develops during isometric contraction, and they cause relaxation.
|
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what is a myotatic unit?
|
the collection of pathways controlling a single joint
|
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the knee jerk reflex is an example of what?
|
a monosynaptic stretch reflex
|
|
what are the three categories of movement?
|
reflex
voluntary rhythmic |
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where are reflex movements integrated?
|
spinal cord (knee jerk reflex)
|
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which type of movement requires integration in the cerebral cortex and basal ganglia?
|
voluntary movement
|
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what parts of the brain are responsible for voluntary movements?
|
cerebral cortex and basil ganglia (in cerebrum) and cerebellum
|
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what forms the extrapyramidal tract?
|
neurons from the basal ganglia
|
|
what is the pyramidal tract?
|
the corticospinal tract -group of neurons controlling voluntary movement that run from motor cortex to spinal cord
|
|
why does parkinson's disease arise?
|
loss of neurons in the basal ganglia that release the neurotransmitter dopamine
|
|
what are some treatments for parkinson's?
|
the precursor for dopamine (L-dopa) because dopamine can't cross blood-brain barrier. L dopa is metabolized to dopamine once it crosses BBB.
dopamine agonists are also used as are inhibitors of the enzymes that break down dopamine |
|
what do curare and metocurine do?
|
induce temporary paralysis by binding to ACh receptors on motor end plate and blocking binding of actual ACh.
|
|
what causes the AP of mycardial contractile cells to last longer?? (the plateau seen in AP plot)
|
1. decrease in K+ permeability
2. increase in Ca++ permeability during repolarization- |
|
increased permeability to Na and Ca has what effect of heart rate?
|
increase depolarization; increase heart rate
|
|
increased permeability to K or decreased permeability to Ca has what effect of heart rate?
|
decrease depolarization; decrease heart rate
|
|
what effect to catecholamines have on heart rate?
|
increase heart rate
|
|
what do catecholamines bind to on autorhythmic cells?
|
beta-1 adrenergic receptors
|
|
what effect does ACh have on heart rate?
|
slows it down -parasympathetic neurotransmitter
|
|
what would happen to AP if lidocaine or tetrodotoxin was applied to a myocardial contractile cell? autorhythmic cell?
|
(both block voltage gated sodium channels)
contractile- could not contract (no AP) auto- does not have voltage gated Na channels so AP would not be affected! |
|
what is atrial fibrillation?
|
arrhythmia that occurs when SA node loses control of pacemaking
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