Ch 4 The Nervous System Flashcards Preview

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Flashcards in Ch 4 The Nervous System Deck (55)
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1

Astrocytes

Nourish neurons and form blood-brain barrier which controls the transmission of solutes from the bloodstream to the nervous tissue

2

Ependymal cells

Line the ventricles of the brain and produce cerebrospinal fluid which physically supports the brain and serves as a shock absorber

3

Microglia

Phygocytic cells that ingest and break down waste products and pathogens in the CNS

4

Oligodendrocytes
And Schwann cells

Oligodendrocytes in CNS
and Schwann cells in PNS produce myelin around the axons

5

Soma

Cell body of neurons

6

Dendrites

Receive incoming messages from other cells

7

Axon hillock

Integrates incoming signals
Next step down from soma
Plays an important role in action potentials or the transmission of electrical impulses down the axon

8

Axon

Next step after axon hillock Long appendage that terminates in close proximity to a target structure.

9

Myelin

Most axons are covered in this to prevent signal loss or crossing of signals

10

Myelin sheath

Insulation for the axon
Increases the speed of conduction in the axon

11

Nodes of Ranvier

Critical for rapid conduction
Small breaks in the myelin sheath

12

Nerve terminal or synaptic bouton (knob)

End of the axon
Enlarged to maximize neurotransmission to the next neuron and ensure proper release of neurotransmitters

13

Synaptic cleft

Small space between neurons into which the terminal portion of the axon releases neurotransmitters which bind to the postsynaptic neuron

14

Synapse

The nerve terminal, synaptic cleft and postsynaptic membrane together

15

Nerve

Multiple neurons bundled together in the PNS
Nerves may be sensory, mixed, or motor

16

Tracts

In the CNS, axons bundled together
Only carry one type of info
Cell bodies of neurons in the same tract are grouped into nuclei

17

Glial cells

Also called nueroglia
Often provide for support and myelination in CNS
Structural role

18

Action potentials

Neurons use all or nothing messages to relay electrical impulses down the axon to the synaptic bouton
Ultimately cause the release of neurotransmitters
Initiated at the axon hillock

19

Resting membrane potential

There is a an electrical potential (voltage) difference between the inside of a neuron and the extracellular space
Usually about -70mV with inside negative relative to outside

20

Na+/K+ ATPase

Neurons are selectively permeable to this and ions to maintain the relatively negative internal environment
Ex for every two K+ ions moved into the cell, 3 Na+ are moved out at expense of one ATP

Also works to restore sodium and potassium gradient (sodium outside, potassium inside) after action potential

21

Depolarization

Excitatory input causes this - it is the raising of the membrane potential (V m) from its resting potential
Makes neuron more likely to fire an action potential

22

Hyper polarization

Inhibitory input causes this
It’s the lowering of membrane potential from its resting potential
Makes neuron less likely to fire action potential

23

Threshold

If the axon hillock receives excitatory input to be depolarized to the threshold value (usually -55 to -40 mV) an action potential will be triggered

24

Summation

The additive effect of multiple signals - some excitatory and some inhibitory

25

Temporal summation

Multiple signals integrated during a relatively short period of time

26

Spatial summation

Additive effects are based on number and location of incoming signals

27

Electrochemical gradient

Promotes the migration of sodium into the cell
Interior is more negative and generally has more sodium ions than exterior

28

Summary of sodium channel process membrane potential

Migration of sodium ion into cell
Cell rapidly depolarizes (becomes positively charged)
Vm approaches +35 mV sodium channels are inactivated and brought back near resting potential to be deinactivated
Sodium channels- closed( before reaching threshold) open (from threshold to about +35 mV) inactive (from +35 back down) and back to closed (after inactivation has been reversed)

29

Path of potassium during membrane potential

Sodium depolarizes cell causing efflux of potassium from neuron
Positively charged K+ out of cell restores negative membrane potential called repolarization and then causes overshoot of resting potential called hyperpolarization

30

Refractory periods

Caused by hyperpolarization due to massive efflux of K+
Absolute refractory period - no amount of stimulation can cause another action potential to occur
Relative refractory period - must be greater than normal stimulation to cause action potential because membrane is more negative than resting