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44 Cards in this Set
- Front
- Back
Dorsal Horn
Ventral Horn |
the spinal cord extends from the brain stem, enclosed in the vertebral canal -Inside of canal: gray matter (outside = white matter) Gray matter is arranged with a left & right dorsal horn, and a left & right ventral horn.
dorsal horn = sensory neurons ventral horn = motor neurons |
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Peripheral Nervous System |
Afferent (ascending) and Efferent (descending) nerves fibers relay info to and from CNS
Afferent: sensory receptors and nerves Cell bodies for nerves are in the dorsal root ganglian (Recall: sensory neurons are pseudo unipolar)
Efferent: divided into 2 branches -Autonomic motor nervous system -Somatic motor system
Afferent:(sends message to CNS) Efferent: (sends away from CNS to muscles/effector) |
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Somatic motor neurons |
always have cell bodies in the spinal cord and just one neuron traveling from spinal cord to effector (skeletal muscle tissue).
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The autonomic motor system |
has two sets of neurons in the PNS. 1. The first has cell bodies in the brain or spinal cord and synapses in an autonomic ganglion---(synapse between the pre and the post!)
2. The second has cell bodies in the ganglion and synapses on the effector (smooth & cardiac muscle). |
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Autonomic Nervous System |
A component of the peripheral nervous system
Control system functioning below the level of consciousness -Involuntary functions
Influences heart rate, digestion, respiratory rate, perspiration, pupil dilation, micturition rate, sexual arousal
Higher level interaction with CNS -Medulla oblongata (respirator centers and more) -Hypothalamus acts as an integrating center as well |
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Autonomic Motor Nerves |
Innervate organs not under voluntary control
Effectors include: -Cardiac muscle -Smooth muscle of visceral organs and blood vessels -Glands
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how is autonomic motor neurons different from somatic motor neurons |
Somatic: go from CNS directly to effector (cell bodies in spinal cord)
Autonomic: 2 neurons -Preganglionic: Cell body in gray matter of spinal cord Travels from CNS (spinal cord) to 2nd neuron Typically myelinated
Postganglionic: axon from 1stpreganglionic neuron to effector organTypically unmyelinated
Synapse: autonomic ganglion |
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Visceral Effector Organs |
Organs controlled by the autonomic NS
Somewhat independent of innervation and will not atrophy if a nerve is cut (unlike skeletal muscle) -Cardiac muscle and some smooth muscle contract rhythmically without nerve stimulation. Autonomic innervation can speed up or slow down intrinsic contractions.
(ex: heart can still operate without ANS: ANS can modify its activity tho)
Unlike somatic motor neurons (which are always stimulatory), autonomic motor neurons can stimulate or inhibit. |
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Autonomic Ganglia |
Located in the head, neck, and abdomen as well as in chains along either side of the spinal cord
Location of autonomic ganglia is a distinguishing feature between the Sympathetic & parasympathetic
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2 systems of the ANS |
Sympathetic: -Preganglionic neurons originate in thoracic and lumbar levels of spinal cord -Send axons to sympathetic gangliaParallel spinal cord
Parasympathetic: -Preganglionic neurons originate in brain and sacral region of spinal cord -Axons synapse to ganglia near or in effector organs
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Sympathetic Preganglionic Neurons |
Myelinatedaxons exit the spinal cord at ventral roots and diverge into white rami communicantes and then into autonomic ganglia at multiple levels.
White rami = entry point gray = exit point (for the chain ganglion)
(allows convergence & divergence ) |
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Sympathetic Postganglionic Neurons |
Unmyelinated axons of the postganglionic neurons form the gray rami communicantes, which return to the spinal nerve and travel with other spinal neurons to their effectors. |
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sympathetic divison |
Pregranglionic neurons come from the theoretic and lumbar regions of the spinal cord
(AKA thoracolumbar division)
See fig 9.5 |
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sympathetic chain of ganglia |
The presynaptic neurons synapse in sympathetic ganglia that run parallel to the spinal cord called paravertebral ganglia. These are Interconnected to form sympathetic chain of ganglia. |
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Divergence of neural pathways: |
Axons have collateral branches, so one presynaptic neuron can form synapses with several postsynaptic neurons.
-one single signal can influence many other neurons
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Convergence of neural pathways |
Several different presynaptic neurons (up to a thousand) can synapse on one postsynaptic neuron.
-tons of into projected on one single neuron |
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Sympathetic chain of ganglia |
can end up at many diff levels |
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convergence & divergence influence on Sympathetic Division |
Because preganglionic neurons can branch and synapse in ganglia at any level, there is: Divergence: One preganglonic neuron synapses on postganglionic neurons at different levels. Convergence: Several preganglionic neurons at different levels synapse on one postganglionic neuron. Allows the sympathetic division to act as a single unit through MASS ACTIVATION. -VERY IMPORTANT FOR FIGHT OT FLIGHT MECH. mass activation prepares you for fight/flight |
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Collateral Ganglia |
(synapse between pre & post neuron) Some sympathetic neurons that exit the spinal cord below the diaphragm do not synapse in the sympathetic chain of ganglia.
Instead, they form splanchnic nerves, which synapse in collateral ganglia. Collateral ganglia include celiac, superior mesenteric, and inferior mesenteric ganglia.
Postganglionic neurons innervate organs of the digestive, urinary, and reproductive systems. |
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The Adrenal Glands: a special case |
Composed of 2 very different parts: 1. Cortex (outer) -Derived from mesodermal tissue
2. Medulla (inner) -Derived from nueralcrest cells, ectoderm tissue |
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Adrenal Glands: cortex + medulla functions |
Cortex (outer) -Secretes steroid hormones
Medulla (inner) -Innervated by Sympathetic preganglionic neuron -Secretes epinephrine (adrenalin) into blood stream -Behaves like a postganglionic sympathetic neuron: NT release of norepinephrine at synapse |
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Adrenal gland |
-interface between blah and blah |
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Summary of the Sympathetic Division |
-table 9.2 -huge amount of reaching out, and diversity -mass action
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Parasympathetic Division |
Preganglionic neurons come from the brain or sacral region of the spinal cord. It is also called the craniosacral division.
They synapse on ganglia located near or in effector organs. -called terminal ganglia |
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Parasympathetic Division (diff from sympathetic?) |
Also called craniosacral division
Preganglionic neurons do not travel with somatic neurons in spinal nerves (as sympathetic postganglionic neurons do).
-Effectors in the skin and skeletal muscles (sweat glands, blood vessels) receive sympathetic but not parasympathetic innervation.
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PS: Cranial Nerves |
-form the top part of PNS (are coming right out of the brain)
Nerves emerge directly from the brain
12 pairs: 1 & 2 emerge from cerebrum (purely sensory) 3 –12 from brain stem
Cranial Nerve II: Optic nerve -Not truly peripheral, extension of diencephalon
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Cranial Nerves and the Parasympathetic Division |
The occulomotor(III) (focus on light), facial (VII), glosso-pharyngeal (IX) (salivation), and vagus(X) nerves carry parasympathetic preganglionic neurons. 1. Occulomotor: Preganglionic fibers exit midbrain and synapse on the ciliaryganglion. 2. Postganglionic fibers innervate the ciliarymuscle of the eye. Critical for accommodation (focusing) |
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Cranial Nerve X (10) KNOW THIS NERVE: |
aka Vagus nerve (wondering nerve)(starts high, ends low then intervates):
1. Provides major parasympathetic innervation to the thoracic and abdominal cavities
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Sacral Nerves |
Preganglionic nerves from the sacral region of the spinal cord provide innervation to the lower part of the large intestine, rectum, urinary and reproductive organs.
Terminal ganglia are located within these organs. |
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Summary of Parasympathetic Division |
table 9 . 3 eye system extension of nerve system |
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Comparison of the Sympathetic and Parasympathetic Divisions |
fig 9.5 (pg 249!!) -come together to form automatic nervous system |
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Sympathetic Functions |
The sympathetic division activates the body for “fight or flight” through the release of norepinephrine from postganglionic neurons and the secretion of epinephrine from the adrenal medulla.
-Prepares the body for intense physical activity in emergencies by increasing heart rate and blood glucose levels and by diverting blood to skeletal muscles
(Mass Action capability) |
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Parasympathetic Functions |
The parasympathetic division is antagonistic to the sympathetic division.
Allows the body to “rest and digest” through the release of ACh from postganglionic neurons. -Slows heart rate, dilates visceral blood vessels, increases digestive activities
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ANS Neurotransmitters |
Both Symp & Parasymp preganglionics release ACh: - called cholinergic synapses
Difference:
Most Symp post ganglia release Norepinephrin(noradenaline) -Called adrenergic synapses 1. A small number release ACh
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somatic vs autonomic |
type of neuron macular junction -lack of specialization |
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Varicosities: a different kind of synapse in the ANS |
Axons of postganglionic neurons have various swellings called varicosities that release neurotransmitter along the length of the axon.
(dumping out neurotransmitter in the smooth muscle)(as it moves through)
They form “synapses en passant” (in passing). |
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Antagonistic Effects: |
Fight or Flight vs. Rest and Digest
Sympathetic and parasympathetic neurons innervate the same tissue
Elicit opposite responses
Example: smooth muscle response 1. Sympathetic: norepinephrin/adrenergic receptors 2. Parasymp: acetylcholine/cholinergic receptors
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Complementary Effects |
Occur when both divisions produce similar effects on the same target
Example: -Salivary gland secretion: Parasympathetic division stimulates secretion of watery saliva; sympathetic constricts blood vessels so the secretion is thicker.
(Both made you salivate, but the end is different) |
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Cooperative Effects |
-Occur when both divisions produce different effects that work together to promote a single action: Example: 1. Erection and ejaculation: Parasympathetic division causes vasodilation and erection; sympathetic causes ejaculation 2. Urination: Parasympathetic division aids in urinary bladder contraction; sympathetic helps with bladder muscle tone to control urination. |
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ANS variability: to stimulate or to inhibit? |
Response to AP in visceral organ depends on whether its from a sympathetic or parasympathetic neuron -Sympathetic = norephinephrine(NE) -Parasympathetic = acetylcholine (ACh)
In many instances the same NT can elicit opposite responses
Due to different types of receptors responding to the same NTs (epinephrine/norepinephrine)
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Organs with Dual Innervation |
Most visceral organs are innervated by both sympathetic and parasympathetic neurons.
Most of the time these systems are antagonists: -Heart rate (PS down, S up) -Digestive functions (PS up, S decrease) -Pupil diameter (PS down, S up) |
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Organs Without Dual Innervation |
The following organs are innervated by the sympathetic division only: -Adrenal medulla -Arrector pili muscles in skin -Sweat glands in skin -Most blood vessels
Regulated by increase and decrease in sympathetic nerve activity
Important for body temperature regulation |
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Control of ANS by the Brain |
Many visceral functions are regulated by autonomic reflexes. 1. Sensory input is sent to brain centers (usually by the vagus nerve), which integrate the information and modify the activity of preganglionic neurons. 2. Medulla oblongata controls many cardiovascular, pulmonary, urinary, reproductive, and digestive functions. |
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Regulation of the Medulla |
Higher brain regions regulate the medulla.
1. Hypothalamus: major regulatory center of the ANS
2. Limbic system: responsible for autonomic responses during emotional states (blushing, pallor, fainting, sweating, racing heart rate) |