The Nervous System

Question 1

neurons

Answer 1

specialized cells capable of transmitting electrical impulses, and then translating those electrical impulses to chemical signals
shape matches its function, dictated by the other cells with which it interacts

Question 2

cell body (soma)

Answer 2

where nucleus of neuron is located

location of the endoplasmic reticulum and ribosomes

Question 3

dendrites

Answer 3

appendages of neuron emanating directly from the soma

receive incoming messages from other cells

Question 4

axon hillock

Answer 4

integrates incoming signals
plays an important role in action potentials
sums signals in order to determine whether excitatory enough to initiate an action potential

Question 5

action potentials

Answer 5

transmission of electrical impulses down the axon
signals can be either excitatory or inhibitory–if excitatory enough, will initiate these
relay electrical impulses down the axon to the synaptic bouton
all-or-nothing messages
cause the release of neurotransmitters into the synaptic cleft

Question 6

axon

Answer 6

long appendage of neuron that terminates in close proximity to a target structure (a muscle, glad, or other neuron)

Question 7

myelin

Answer 7

insulates most mammalian nerve fibers to prevent signal loss or crossing of signals
increases the speed of conduction in the axon
produced by oligodendrocytes (CNS) or Schwann cells (PNS)

Question 8

myelin sheath

Answer 8

maintains the electric signal within one neuron

Question 9

oligodendrocytes

Answer 9

produce myelin in CNS

Question 10

Schwann cells

Answer 10

produce myelin in PNS

Question 11

nodes of Ranvier

Answer 11

at certain intervals along the axon, there are small breaks in the myelin sheath with exposed areas of axon membrane
critical for rapid signal conduction

Question 12

nerve terminal/ synaptic bouton (knob)

Answer 12

at the end of the axon

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

Question 13

neurotransmitters

Answer 13

chemicals that transmit information between neurons

Question 14

synaptic cleft

Answer 14

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

Question 15

synapse

Answer 15

collectively, the nerve terminal, synaptic cleft, and postsynaptic membrane

Question 16

nerve

Answer 16

multiple neurons bundled together in the PNS

may be sensory, motor, or mixed

Question 17

tracts

Answer 17

axons bundled together in CNS

Question 18

nuclei

Answer 18

how cell bodies of neurons in the same tract are grouped (CNS)

Question 19

glial cells/ neuroglia

Answer 19

play both structural and supportive roles

• astrocytes
• ependymal cells
• microglia
• oligodendrocytes (CNS) & Schwann cells (PNS)

Question 20

astrocytes

Answer 20

nourish neurons and form the blood-brain barrier, which controls the transmission of solutes from the bloodstream into nervous tissue

Question 21

ependymal cells

Answer 21

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

Question 22

microglia

Answer 22

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

Question 23

resting membrane potential

Answer 23

-70 mV
inside of neuron negative relative to outside
use selective permeability to ions and Na+/K+ ATPase to maintain this negative internal environment
electrical potential difference (voltage) between inside of the neuron and extracellular space

Question 24

Na+/K+ ATPase

Answer 24

maintains resting membrane potential at -70 mV by moving 3 Na+ ions out of the cell for every 2 K+ ions moved into the cell
important for restoring gradient after action potentials have been fired (energy necessary to move ions against their gradients)
active transport

Question 25

depolarization

Answer 25

caused by excitatory input (raises the membrane potential, Vm, from its resting potential
makes neuron more likely to fire an action potential

Question 26

hyperpolarization

Answer 26

caused by inhibitory input (lowers the membrane potential from its resting potential)
makes neuron less likely to fire an action potential

Question 27

threshold

Answer 27

usually in the range of -55 to -40 mV
if enough excitatory input to be depolarized to this point, action potential will be triggered (opening of voltage-gated sodium channels in membrane)
therefore, not every stimulus generates a response

Question 28

summation

Answer 28

additive effects of multiple signals

temporal and spatial

Question 29

temporal summation

Answer 29

multiple signals integrated during a relatively short period of time

Question 30

spatial summation

Answer 30

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

Question 31

electrochemical gradient

Answer 31

promotes the migration of sodium into the cell
interior of cell more negative than exterior of cell, which favors the movement of positively charged sodium cations into the cell
higher conc of sodium outside the cell than inside, which also favors movement of sodium into the cell

Question 32

depolarization

Answer 32

occurs when membrane potential becomes more positive as sodium passes through ion channels into the cell

Question 33

inactivated sodium channels

Answer 33

occurs when Vm approaches +35 mV

have to be brought back near the resting potential to be reversed

Question 34

closed sodium channels

Answer 34

before the cell reaches threshold, and after inactivation has been reversed

Question 35

open sodium channels

Answer 35

from threshold to approximately +35 mV

Question 36

inactive sodium channels

Answer 36

from approximately +35 mV to the resting potential

Question 37

repolarization

Answer 37

restoration of the negative membrane potential as positively charged potassium cations are driven out of the cell

Question 38

hyperpolarization

Answer 38

efflux of K+ causes an overshoot of resting membrane potential
serves an important function: makes the neuron refractory to further action potentials

Question 39

refractory periods

Answer 39

absolute and relative

Question 40

absolute refractory period

Answer 40

no amount of stimulation can cause another action potential to occur

Question 41

relative refractory period

Answer 41

there must be greater than normal stimulation to cause an action potential because the membrane is starting from a potential that is more negative than its resting value

Question 42

impulse propagation

Answer 42

for a signal to be conveyed to another neuron, the action potential must travel down the axon and initiate neurotransmitter release
information can only flow in one direction

Question 43

saltatory conduction

Answer 43

process by which an electrical signal jumps across the nodes of Ranvier to travel down the axon

Question 44

neurotransmitters

Answer 44

released into synapse at nerve terminal
when action potential arrives, voltage-gated calcium channels open
influx of calcium causes fusion of vesicles filled with these with the presynaptic membrane, resulting in exocytosis of these into synaptic cleft
bind to receptors on the postsynaptic cell, which may be ligand-gated ion channels or G protein-coupled receptors
must be cleared from postsynaptic receptors to stop the propagation of the signal
can be enzymatically broken down, can be absorbed back into presynaptic cell, can diffuse out of synaptic cleft

Question 45

reuptake channels

Answer 45

absorb neurotransmitters back into the presynaptic cell

Question 46

white matter

Answer 46

in CNS, consists of myelinated axons–in brain, deeper than grey matter; in spinal cord, grey matter deeper

Question 47

grey matter

Answer 47

in CNS, consists of unmyelinated cell bodies and dendrites

Question 48

somatic NS

Answer 48

voluntary

Question 49

autonomic NS

Answer 49

automatic

divided into parasympathetic NS and sympathetic NS

Question 50

parasympathetic NS

Answer 50

rest-and-digest

Question 51

sympathetic NS

Answer 51

fight-or-flight

Question 52

reflex arcs

Answer 52

use ability of interneurons in spinal cord to relay information to the source of stimuli while simultaneously routing it to the brain

Question 53

monosynaptic reflex arc

Answer 53

sensory (afferent, presynaptic) neuron fires directly onto motor (efferent, postsynaptic) neuron

Question 54

polysynaptic reflex arc

Answer 54

sensory neuron may fire onto motor neuron as well as interneurons that fire onto other motor neurons