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Animal Physiology > Exam 2: Ch 5 Book Background Info > Flashcards

Exam 2: Ch 5 Book Background Info Flashcards

1
Q

what is a neuron

A

a nerve cell that communicates information using a combination of electrical and chemical signals

convey electrical signals rapidly and accurately to organize and direct physiological responses

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2
Q

most neurons are ____ excitable

A

electrically

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3
Q

what does being electrically excitable mean

A

electrical signals can be generated across the plasma membrane

these signals are transmitted across the cell’s length without losing signal strength b/c of the movement of ions

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4
Q

glial cells

A

supportive cells of the nervous system that fill the spaces between neurons

10-50x more glia than neurons

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5
Q

what does the nervous system do

A

collects and processes information, analyzes it, and generates outputs to control responses

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6
Q

why is studying neurons useful

A

electrical properties easily studied with tools from the physical sciences

neurons function similarly in all animals so results from one species are applicable to many others

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7
Q

neurons process info in a complex manner but in doing so they rely on a surprisingly _____ number of basic physical and chemical properties

A

small

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8
Q

soma

A

cell body of a neuron

responsible for metabolic maintenance

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9
Q

nerve processes

A

thin fibers that arise from the soma

2 types: dendrites and axons

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10
Q

dendrites

A

branched nerve processes that extend from the soma and serve as receivers that gather signals from other neurons

transmit signals toward the soma

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11
Q

cells with a complex dendritic tree…

A

typically receive input from many other neurons

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12
Q

axons (nerve fibers)

A

a specialized nerve process that conducts signals away from the soma

may be very long (spine to muscles)

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13
Q

axon terminal

A

a region at the end of the axon that allows signals to be sent simultaneously to many other neurons (to glands, to muscle fibers)

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14
Q

many vertebrate axons are surrounded by supporting cells that provide an insulating layer called the ….

A

myelin sheath

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15
Q

during embryonic development and maintenance through life…

A

dendrites and the axon grow outward from the soma

maintenance of these fibers depends on a steady flow of proteins and other constituents that are synthesized in the soma and transported down the processes

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16
Q

what happens if an axon in an adult animal is severed?

A

degenerates back to the soma within days or weeks

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17
Q

regeneration of axons in mammals

A

limited to nerves in the periphery of the body

in cold-blooded vertebrates some regeneration may happen in the CNS

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18
Q

damaged neurons in invertebrates

A

many times they will regenerate and reestablish connections with their original targets

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19
Q

what does a spinal motor neuron do?

A

carries signals from soma in spinal cord to skeletal muscle fibers

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20
Q

spike-initiating zone

A

an area located at or near the junction between the axon and soma (axon hillock)

integrates signals from many input neurons to determine whether an action potential is created

actions potential originate in the spike-initiating zone

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21
Q

action potential (spike, nerve impulse)

A

voltage across plasma membrane rapidly rises then falls

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22
Q

where does the axon carry the action potential?

A

from the spike-initiating zone to the axon terminals, which transmit the signal to other cells

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23
Q

axon hillock

A

the junction between the axon and soma

the spike-initiating zone is often found here

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24
Q

much of the physiological behavior of the neuron depends on ______ _____ ____ such as ____ and _____

A

passive electrical properties

capacitance and resistance

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25
Q

neurons also possess active electrical properties that allow them to…

A

conduct electrical signals without loss of strength

depends on the presence of proteins in the plasma membrane called voltage-gated ion channels

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26
Q

voltage-gated ion channels

A

proteins in the cell membrane that allow ions to cross in a regulated fashion

located in regions of specialized signaling function

open when the plasma membrane is depolarized to make an AP

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27
Q

what voltage-gated ion channels are found in the axonal membrane

A

Na and K

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28
Q

what voltage-gated ion channels are found in the axon terminals

A

Ca

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29
Q

the axon of a sensory neuron is called?

A

an afferent fiber

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30
Q

what does afferent fiber mean

A

it conducts signals inward toward higher processing centers in the brain

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31
Q

interneuron

A

the most numerous type of neuron found only in the CNS

link and carry information between other neurons

32
Q

synapse

A

a specialized region between the axon of a neuron and the dendrites of another

33
Q

types of effector organ

A

muscles and glands

34
Q

efferent neuron

A

neurons that carry information from the processing regions of the CNS outward to effectors

35
Q

neuronal circuit

A

afferent neurons, interneurons, and efferent neurons

36
Q

a cell that passes information to a particular neuron is said to be _____

A

presynaptic

37
Q

a cell that receives information transmitted across a synapse is said to be _____

A

postsynaptic

38
Q

most synaptic transmission is carried by chemical _________

A

neurotransmitters

39
Q

neuronal circuit cockroach example

A

afferent neurons in the wind receptors in the tail contact large interneurons in the CNS

the interneurons contact efferent motor leg neurons

stimulus causes the cockroach to run away

40
Q

the plasma membrane of the postsynaptic neuron’s dendrites and soma contain…

A

ligand-gated ion channels that bind neurotransmitters

these cause the postsynaptic cell to respond to the presence of the chemical signal

41
Q

all or none signals

A

signals whose amplitude is invariant

APs

42
Q

graded signals

A

signals whose amplitude is variable

depends on stimulus strength or another variable

43
Q

sensory neruons

A

transmit info collected from external stimuli (sound, light, pressure) or respond to internal stimuli (blood oxygen level, the orientation of the head, position of a joint)

44
Q

motor neurons

A

carry signals to effector organs

cause contraction of muscles or secretion by gland cells

45
Q

central nervous system

A

brain and nerve cord

46
Q

ganglia

A

neuronal stomata distributed along the nerve cord

typically control local regions of the animal’s body

47
Q

vertebrate vs invertebrate spinal cord

A

vertebrate: located along dorsal midline
invertebrate: ventral midline

48
Q

oligodendrocytes

A

glia found in the CNS

49
Q

schwann cells

A

glia in the periphery that wrap axons in myelin

50
Q

myelin sheath

A

an insulating coating around axons that contributes to reliable and rapid transmission of APs

51
Q

functions of glial cells

A

regulate [K+], pH in fluid filled spaces

remove neurotransmitters from extracellular space

provide structural and metabolic support

52
Q

glial cell membranes are highly permeable to

A

K+

coupled by junctions that allow K+ to flow between

this flux allows glial cells to take up and redistribute extracellular K+, which could otherwise buildup

53
Q

voltage

A

electrical potential difference

54
Q

although a stable voltage exists across the plasma membranes of all cells, only the membranes of ______ ______ _____ can respond to changes in their transmembrane potential difference by generating APs

A

electrically excitable cells

ex. neurons, muscle fibers

55
Q

how are membrane potentials measured

A

as electrical current

detected directly by using two electrodes to measure change caused by current flow across the membrane

56
Q

where are the sensing electrodes placed

A

one in electrical contact with the cytosol

the other in contact with the extracellular medium

this is so any potential difference can be measured (membrane potential Vm) and amplified and displaced on a recording instrument like a computer or oscilloscope

57
Q

membrane potential Vm units

A

volts

58
Q

what did Hodgkin and Huxley study in the 40s and 50s

A

membrane potentials from squid giant axons

59
Q

resting potential (Vrest)

A

the steady inside-negative potential recorded when no APs or postsynaptic events are occurring

expressed in millivolts (usually between -20 - -100)

60
Q

the cytoplasm of the cell is ___potential

A

isopotential

61
Q

calculate the strength of the electric field across the plasma membrane

A

E = V/d

E = strength of electric field

V = volts

d = distance in meters (5nm b/c plasma membrane)

62
Q

how to measure passive electrical properties of the plasma membrane

A

put two microelectrodes into one cell

current delivered from a current generator to the current electrode

recording electrode records this effect on membrane potenetial

63
Q

current generator effects

A

current in form of migrating ions

flow if from positivity to negativity

if positive current, flows into cytosol and out the cell

if negative current, positive charge is drawn out of the cytosol and into the electrode

64
Q

hyperpolarization

A

when the interior of the cell becomes even more negative, which increases the size of the potential difference across the plasma membrane

ex. -60 mV to -70 mV

65
Q

depolarization

A

if the current electrode adds positive charge to the interior of the cell it diminishes the potential difference across the membane

ex. -60 mV to -20 mV

66
Q

as the amount of applied positive current increases, the ____ __ ________ also increases

A

degree of depolarization

67
Q

what can depolarization cause?

A

some voltage-gated Na+ ion channels to open

causes an AP

68
Q

threshold potential

A

the value of the membrane potential at which an AP is triggered 50% of the time

69
Q

ion selectivity in channels

A

most channels allow only one or a few ionic species to cross the membrane

movement driven by electrochemical gradient

70
Q

what is responsible for the dramatic depolarization during an AP

A

simultaneous opening of many voltage-gated Na channels when initial depolarization reaches the threshold potential

71
Q

what is responsible for the passive change in membrane potential in response to hyperpolarizing current?

A

K+ selective leak channels that are always open

maintain resting potential and are uniformly distributed in the plasma membrane

72
Q

ligand-gated channels

A

ion channels that open when messenger molecules like neurotransmitters bind to receptor proteins in the cell surgace

73
Q

electrochemical potential

A

the voltage difference across the plasma membrane described as Vm (the membrane potential)

74
Q

what does electrochemical potential depend on

A

concentrations of several ion species inside the cell being different than outside the cell (gradient)

ion channels being selectively permeable

75
Q

equilibrium potential

A

a potential difference across a membrane established by one ion being permeable vs. another impermeable ion

formed when a permeable ion diffuses down its concentration gradient until a repulsive electrical potential balances the concentration gradient

ex. Cl- impermeable and K+ permeable

76
Q

electromotive force (emf)

A

force due to electric potential difference across the membrane

can offset concentration gradient

77
Q

steady state

A

system remains invariant

maintenance requires no expenditure of energy

Animal Physiology (26 decks)

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