The Nervous System

Question 1

soma

Answer 1

cell body of neuron

Question 2

dendrites

Answer 2

projections from soma that receive incoming messages

Question 3

axon hillock

Answer 3

integrates incoming signals

Question 4

action potentials

Answer 4

transmission of electrical impulses down the axon

Question 5

axon

Answer 5

long appendage that terminates in close proximity to a target structure

Question 6

myelin

Answer 6

insulation that prevents signal loss or crossing of signals; also increases speed

Question 7

myelin sheath

Answer 7

maintains the electrical signal within one neuron

Question 8

oligodendrocytes

Answer 8

produce myelin in CNS

Question 9

Schwann cells

Answer 9

produce myelin in PNS

Question 10

nodes of Ranvier

Answer 10

small breaks in myelin sheath where there is exposed areas of axon; critical for rapid signal conduction

Question 11

nerve terminal (synaptic bouton/knob)

Answer 11

end of the axon; flattened and enlarged to maximize neurotransmission to the next neuron and ensure proper release of neurotransmitters

Question 12

synaptic cleft

Answer 12

space between axon and dendrite

Question 13

synapse

Answer 13

nerve terminal, synaptic cleft and postsynaptic membrane

Question 14

nerve

Answer 14

multiple neurons bundled together

Question 15

tracts

Answer 15

carry one type of information; cell bodies of neurons of same tract are grouped into nuclei

Question 16

glial cells (neuroglia)

Answer 16

play both structural and supportive roles to neurons

Question 17

astrocytes

Answer 17

nourish neurons and form blood brain barrier

Question 18

ependymal cells

Answer 18

line the ventricles of the brain and produce CSF

Question 19

microglia

Answer 19

phagocytic cells that ingest and break down waste and pathogens in CNS

Question 20

action potentials

Answer 20

all or nothing messages that really electrical impulses down the axon to the synaptic bouton

Question 21

resting membrane potential

Answer 21

net electrical potential difference that exists across the cell membrane, created by movement of charged molecules across that membrane

Question 22

potassium leak channels

Answer 22

allow slow leak of potassium out of the cell

Question 23

equilibrium potential of potassium

Answer 23

as one potassium is moved out, another is moved in

Question 24

sodium leak channels

Answer 24

allow slow leak of sodium out of cell

Question 25

equilibrium potential of sodium

Answer 25

sodium is moving into and out of cell at same rate

Question 26

NA/K ATPase

Answer 26

continually pumps sodium and potassium back to where they started (K into cell and NA out) to maintain gradients

Question 27

depolarization

Answer 27

raising the membrane potential from its resting potential, causing the neuron to be more likely to fire an action potential

Question 28

hyperpolarization

Answer 28

lowering the membrane potential from its resting potential, making it less likely to fire an action potential

Question 29

threshold

Answer 29

if this level is surpassed, an action potential will be triggered

Question 30

summation

Answer 30

additive effect of multiple signals

Question 31

temporal summation

Answer 31

multiple signals are integrated during a relatively short period of time

Question 32

spatial summation

Answer 32

additive effects are based on the number and location of incoming signals

Question 33

electrochemical gradient

Answer 33

promotes the migration of sodium into the cell

Question 34

states of sodium channels

Answer 34

closed: before cell reaches threshold and after inactivation has been reversed
open: from threshold to app. +35mV
inactive: from app. +35 to resting potential

Question 35

absolute refractory period

Answer 35

no amount of stimulation can cause another action potential to occur

Question 36

relative refractory period

Answer 36

must be greater than normal stimulation to cause an action potential

Question 37

impulse propagation

Answer 37

movement of an action potential down the axon to initiate neurotransmitter release

Question 38

saltatory conduction

Answer 38

signal “hops” from node to node

Question 39

effector

Answer 39

postsynaptic cell that is not another neuron

Question 40

supraspinal circuit

Answer 40

require input from brain or brainstem rather than only the spinal cord

Question 41

white matter

Answer 41

axons encased in myelin sheaths

Question 42

gray matter

Answer 42

unmyelinated cell bodies and dendrites

Question 43

monosynaptic reflex arc

Answer 43

single synapse between the sensory neuron and the motor neuron

Question 44

polysynaptic reflex arc

Answer 44

at least one interneuron between the sensory and motor neuons