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47 Cards in this Set

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What is the most distinctive feature of a neuron?


Their shape; long branching extensions.



Motor neuron

Soma in the spinal cord; receives excitation through dendrites and conducts impulses along axon to a muscle.

Sensory neuron

Specialized at one end to be highly sensitive to a particular type of stimulation (light, sound, touch). Conducts touch information from skin to spinal cord.

Dendrites


Branching fibers with a surface lined with synaptic receptors responsible for bringing info into the neuron.


Greater surface area- more info can receive.

Cell body


Contains nucleus, mitochondria and ribosomes.


Responsible for metabolic work of neuron.


Covered with synapses on its surface in many neurons.


Axons

Thin fiber of a neuron responsible for transmitting nerve impulses toward other neurons, organs and muscles.


Myelin sheath- insulated material that contains interruptions known as nodes of Ranvier.


Presynaptic terminals at the end points of an axon release chemicals to communicate with other neurons.

Two kinds of cells in the nervous system:


Neurons and glia.

Structures of a neuron:


1. Membrane 2. Nucleus 3. Mitochondria 4. Ribosomes 5. Endoplasmic reticulum

Membrane


Separates the inside of the cell from the outside movement.
Nucleus

Contains the chromosomes.

Mitochondria
Performs metabolic activities and provides energy that the cell requires.

Ribosomes


Sites at which the cell synthesizes new protein molecules.




Endoplasmic reticulum


Network of thin tubes that transports newly synthesized proteins to their location.



Afferent axon


Bringing information into a structure.

Efferent axon

Carrying information away from a structure.

Interneurons/ intrinsic

Dendrites and axons are completely contained within a single structure.

Astrocytes

Type of glia that helps synchronize activity of an axon by wrapping around the presynaptic terminal and taking up chemicals released by the axon.

Microglia


Remove waste material, viruses and fungi from the brain.
A branching fiber that forms the information- receiving pole of the nerve cell.

Dendrite.

Name the correct order of transmission of information to a neuron?

Dendrite- cell body- axon
What does myelin cover?
Some axons in vertebrates; none in invertebrates.

Where do axons convey information?

Towards other neurons, an organ or a muscle.


(Away from their own cell body.)
The Blood- Brain Barrier


A mechanism that surrounds the brain and blocks most chemicals from entering.


-The immune system destroys damaged or infected cells throughout the body.


- Because neurons in the brain generally do not generate, it is vitally important for the blood brain barrier to block incoming viruses, bacteria or other harmful material from entering.


Which of the following is most likely to cross the cell membrane by simple diffusion?

Small, uncharged molecules.

Why do neurons rely so heavily on glucose as their source of nutrition?

Other fuels do not readily cross the blood-brain barrier.

Presynaptic neuron

sending signal; to presynaptic terminal (axon terminal)


-holds a bunch of tiny synaptic vesicle sacs- each loaded with thousands of molecules of a given neurotransmitter.

Postsynaptic neuron
receiving cell; accepts neurotransmitters in the receptor region usually on dendrite or cell body itself.
Why does the brain need thiamine (vitamin B1)?

As a building block for making proteins.
Resting Neuron

Outside the membrane contains positively charged sodium ions (more of these).


Inside contains positive potassium ions mingled with bigger negatively charged proteins.

Resting Membrane Potential

-70 mV
Polarized
Neuron has negative membrane potential.
Sodium Potassium Pump


For every 2 potassium ions pumps into, pumps out 3 sodium ions.




Different charges- electrochemical gradient- nature doesn't like this.

Ion channels


Large proteins provide safe passage across membrane.




1. Voltage gated channels


2. Ligand gated channels


3. Mechanically gated channels


Voltage gated channels

open and close in response to changes in membrane potential.

ligand gated channels

open with a neurotransmitter- latches onto receptor (serotonin, hormones)
Mechanically gated channels

open in response to physical stretching of membrane.
Graded potential


Small, localized.


Only a few channels open and only a little sodium enters the cell= little change in membrane.

Action potential


long distance signals down an axon.


depolarize resting neuron.


Repolarization

voltage gated potassium ions open up- potassium ions flow out to attempt rebalance charges.
Hyperpolarization

voltage briefly drops to -75mV before all gates close and sodium potassium pumps take over and bring things back to resting level.

Refractory period

an axon cannot respond to any other stimulus- prevent signals from traveling in both directions down axon at once.
Initial threshold

-55mV

Peak depolarization

40 mV

Conduction velocity

speed

Electrical synapses

immediate

Chemical synapses
More precise/ selective, take more time, used more often, more control, much more abundant. sends signals to certain recipients.