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Human Anatomy and Physiology > Exam 3 > Flashcards

Exam 3 Flashcards

1
Q

what causes muscle movement

A

stimulation which leads to contraction

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2
Q

what are the three types of muscle tissue

A

skeletal
cardiac
smooth

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3
Q

skeletal muscle tissue

A

long, cylindrical, stratified fibers arranged parallel and unbranched: fibers are multinucleated; fiber is under voluntary control

primarily responsible for moving skeleton and selected other components of the body

found attaches to bone and sometimes skin

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4
Q

cardiac muscle tissue

A

short, stratified cells typically branching; cells contain one or two centrally located nuclei; intercalated discs between cells; under involuntary control

pumps blood through heart

found in heart wall (myocardium)

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5
Q

smooth muscle tissue

A

nonstriated cells that are short and fusiform in shape; contain one centrally located nucleus; under involuntary control

moves and propel materials through internal organs, controls size of the lumen

found in walls of hollow internal organs such as intestines, stomach, airways, bladder, uterus, and blood vessels

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6
Q

what muscle tissues are involved in involuntary control

A

smooth and cardiac muscle

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7
Q

what are the functions of the skeletal muscle

A

body movement (move, facial expressions, speak, breathe)
maintenance of posture (stabilizes joints, maintain body position)
protection and support (package internal organs and hold them in place)
regulating elimination of material (circular sphincters control passage of material at orifices)
heat production (helps maintain body temp)

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8
Q

characteristics of skeletal muscle tissue

A

excitability
conductivity
contractibility
elasticity
extensibility

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9
Q

excitability

A

ability to respond to a stimulus by changing electrical membrane potential

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10
Q

conductivity

A

involves sending an electrical change down the length of the cell membrane

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11
Q

contractility

A

exhibited when filaments slide past each other which enables muscle to cause movement

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12
Q

elasticity

A

ability to return to original length following a lengthening or shortening

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13
Q

extensibility

A

ability to be stretched

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14
Q

muscle cells are called muscle fibers and are grouped together, each group of these is called a

A

facet

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15
Q

epimysium

A

a connective tissue layer that surrounds entirety of muscle

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16
Q

perimysium

A

boundary between each facet

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17
Q

endomysium

A

loose areolar connective tissue that surrounds individual muscle fibers

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18
Q

plasma membrane of muscle cells is called

A

the sarcolemma

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19
Q

sarcomeres consist of

A

bundles of contractile proteins called myofilaments

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20
Q

myofilaments are also called

A

contractile proteins

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21
Q

myofibrils

A

hundreds to thousands per cell that are bundles of myofilaments (contractile proteins) enclosed in the sarcoplasmic reticulum and make up most of cell’s volume

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22
Q

sarcoplasmic reticulum

A

internal membrane complex similar to smooth endoplasmic reticulum that contain terminal cisternae

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23
Q

terminal cisternae

A

blind sacs of sarcoplasmic reticulum
serve as resovioir for calcium ions
combine in twos with central T-tubule to form triads

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24
Q

Ca2+ pump in sarcoplasmic reticulum

A

has pumps that important calciu into sarcoplasmic reticulum where it binds to calmodulin and calsequestrin

has channels that allow Ca2+ to be released into surrounding sarcoplasm to trigger contraction

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25
Q

thick filaments

A

consist of bundle of many myosin protein molecules

each mysoin molecule has two heads and two intertwined tails
heads have binding site for actin of thin filaments and ATPase site
heads point toward ends of the filament

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26
Q

thin filaments

A

consist mostily of two twisted strands of filamentous actin (F-actin)
each strand is a necklace of hundredsd of actin globules (G-actin)
each G-actin has a myosin binding site to which myosin heads attach during contraction

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27
Q

tropomyosin

A

twisted string like protein covering actin in a noncontracting muscle

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28
Q

troponin

A

globular protein attached to tropomyosin

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29
Q

when Ca2+ binds to troponin…

A

it pulls tropomyosin off actin allowing contraction

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30
Q

what are the regulatory proteins of thin filament

A

tropomyosin and troponin

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31
Q

organization of a sarcomere

A

myofilaments are arranged in repeating units called sarcomeres which are subunits of myofilaments
they are composed of overlapping thick and thin filaments
delinated at both ends by Z dics
the positions of thin and thick filaments give rise to alternating I-bands and A-bands

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32
Q

z discs

A

specialized proteins perpendicular to myofilaments that serve as anchors for thin filaments

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33
Q

motor unit

A

a motor neuron and all the muscle fibers it controls

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34
Q

what determines motor unit size

A

location in the body and what is required of muscle

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35
Q

neuromuscular junction

A

found where motor neuron innervates muscle
usually mid-region of muscle fibers
has synaptic knob, synaptic cleft, motor end plate

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36
Q

motor end plate

A

refers to the segment of plasma membrane of muscle fiber that interacts where neuron meets

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37
Q

ACh

A

the specific neurotransmitter that is going to be released to kick off muscle contraction

diffuses from synaptic cleft into motor end plate

the gray bodies that line the sarcolemma are acetylcholine receptors that transfer it from the synaptic cleft into motor end plate

calcium allows for the exocytosis of ACh

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38
Q

muscle fibers exhibit

A

resting membrane potential (RMP) meaning that fluid inside cell is negative compared to fluid outside of cell

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39
Q

what is the RMP of muscle cells

A

-90mV

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40
Q

what sets RMP is skeletal muscle fibers

A

leak channels and Na+/K+ pumps
(voltage gated channels are closed)

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41
Q

where is calcium stored in muscle fibers

A

in sarcoplasmic reticulum

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42
Q

sodium potassium pump (Na+/K+)

A

ion pumps that actively transport sodium out of cell and actively transport potassium into the cell

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43
Q

what is the level of sodium when a muscle cell is at rest?

A

concentration of sodium is greater outside than in

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44
Q

what is the level of potassium when muscle cell is at rest

A

concentration of potassium is greater inside than outside

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45
Q

events in skeletal muscle contraction

A
  1. neuromusclar junction: excitation of skeletal muscle fiber
  2. sarcolemma, t-tubules, and sarcoplasmic reticulum: excitation-contraction coupling
  3. sarcomere: crossbridge cycling
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46
Q

neuromuscular junction: excitation of a skeletal muscle fiber

A
  1. calcium (Ca2+) enter the synaptic knob.
    - A nerve signal is propagated down a motor axon and triggers the energy of Ca2+ into the synaptic knob. Ca2+ binds to proteins in synaptic vessicle membrane
  2. release of ACh from synaptic knob
    -calcium binding triggers synaptic vessicle to merge with the synaptic knob plasma membrane and ACh is exocytosed into the synaptic cleft
  3. Binding of ACh receptor at motor end plate
    -ACh diffuses across the fluid filled synaptic cleft int he motor end plate to bind with ACh receptors
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47
Q

simple version of exciation of muscle fiber

A

neuron excites muscle fiber
ACh binds to its receptors at motor end plate
ACh diffuses across cleft, binds to receptors, excites fiber

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48
Q

sarcolemma, t-tubules, and sarcoplasmic reticulum: excitation contraction coupling

A
  1. development of an end-plate potential (EPP) at the motor end plate
    -binding of ACh to ACh receptors in the motor end plate triggers the opening of these chemically gated ion channels. Na+ (sodium) rapidly diffuses into and K+ slowly diffuses out of the muscle fiber
    -an end plate potential is produced when sufficient Na+ enters at the motor end plate and the membrane potential changes from -90mV to -65mV
  2. initiation and propagation of an action potential along sarcolemma and T-tubules
    - the EPP initiates an action potential to be propagated along the sarcolemma and t-tubules
    -first, voltage gated Na+ channels open and Na+ moves in to cause depolarization
    -second, voltage gated K+ channels open and K+ moves out to cause repolarization
  3. release of Ca2+ from the sarcoplasmic reticulum
    -the action potential is then propagated along the t-tubules to trigger the opening of Ca2+ channels located in the terminal cisternae of the sarcoplasmic reticulum.
    -Ca2+ diffuses out of the cisternae sarcoplasmic reticulum and into the sarcoplasm
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49
Q

events of action potential at the sarcolemma

A
  1. the sarcolemma of an unstimulated skeletal muscle fiber has a resting membrane potential of -90mV
  2. the threshold is reached when an end=plate potential (EPP) is produced as sufficient Na+ enters the motor end plate to change the RMP from -90mV to -65mV (threshold value)
  3. depolarization occurs as voltage-gated Na+ channels on the sarcolemma open and Na+ enters rapidly reversing the polarity from negative to positive
  4. repolarization occurs due to closure of voltage-gated Na+ channels and opening of voltage-gated K+ channels on the sarcolemma. K+ moves out of the cell and the polarity is reversed from positive to negative (+30mV to -90mV)
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50
Q

sarcomere: crossbridge cycling

A
  1. Ca2+ binding
    - Ca2+ binds to troponin’s calcium binding sites (regulatory proteins associated with thin filaments) causing a conformational change in troponin. Troponin changes shape and the entire troponin-tropomyosin complex is moved - this tropomyosin no longer covers the myosin binding site on actin
  2. Crossbridge Formation
    -myosin heads, which are in cocked position, bind to the exposed myosin binding site on actin forming a crossbridge between myosin and actin
  3. Power Stroke (“pull”)
    -the myosin head swivels toward the center of the sarcomere pulling along the attache thin filament. this motion is called a power stroke. ADP and inorganic P are released during this process. myosin head bends forward towards center of sarcomere attached to thin filament. ADP and P are released
  4. release of myosin head
    -myosin head released from actin. ATP binding site open so ATP binds to site which allows for release of myosin head from actin
  5. reset myosin head (“reset”)
    -ATP is split into ADP and P by myosin ATPase
    -provides the energy to reset the myosin head
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51
Q

crossbridge cycling

A

multiple repetitions of attach, pull, release, and reset lead to fully contracted sarcomere

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52
Q

as long as ______ and _____ are present cycling continues

A

Ca2+ and ATP

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53
Q

what does crossbridge cycling result in

A

sarcomere shortening as Z discs move closer together

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54
Q

events in muscle relaxation

A

-termination of nerve signal and ACh release from motor neuron
-hydrolysis of ACh by acetylcholinesterase
-closure of ACh receptor causes cessation of end plate potential
-no further action potential generation
-closure of calcium channels in sarcoplasmic reticulum
-return of Ca2+ to sarcoplasmic reticulum by pumps
-return of troponin to original shape
-return of tropomyosin blockade of actin’s myosin binding sites
-return of muscle to original position due to its elasticity

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55
Q

how much ATP do muscle cells store

A

only a small amount, after about 5 seconds of intense exertion stored ATP is spent

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56
Q

what are the 3 ways to generate ATP in skeletal muscle fiber

A

immediate supply via phosphate transfer
short term supply via glyoclysis
long term supply via aerobic cellular respiration

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57
Q

immediate supply of ATP: phosphate transfer

A

myokinase transfer inorganic phosphate from one ADP to another
creatine kinase transfers inorganic phosphate from creatine phosphate to ADP

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58
Q

short-term means of supplying ATP: glyoclysis

A

glucose forms into 2 pyruvate molecules and gives off ATP and NADH to regenerate NAD+

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59
Q

long-term means of supplying ATP: aerboic cellular respiration

A

pyruvate undergoes citric acid cycle and then into the ETC to give off ATP

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60
Q

what does the source of ATP depends on

A

insensity and duration of exercise

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61
Q

for a 50 meter sprint (less than 10 seconds) where is ATP coming from

A

primarily by phosphate transfer system

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62
Q

for a 400-meter sprint (less than a minute) where is ATP coming from

A

ATP supplied primarily by glycolysis after first few seconds

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63
Q

for a 1500 meter run (more than a minute) where is ATP coming from

A

primarily by aerobic processes after first minute

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64
Q

what are the two criteria that categorize muscle fibers

A

type of contraction
primary means used for supplying ATP

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65
Q

the type of contraction generated refers to differences in

A

power, speed, and duration

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66
Q

the larger a muscle fiber the …

A

more powerful

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67
Q

fast-twitch fibers

A

more powerful and have quicker and briefer contractions than slow-twitch fibers

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68
Q

oxidative fibers (fatigue resistant)

A

use aerobic cellular respiration
contains extensive capillaries, many mitochondria, and has a large supply of myoglobin (red fibers)

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69
Q

glycolytic fibers (fatiguable)

A

use anaerobic cellular respiration
contains fewer capillaries, fewer mitochondria, smaller supply of myoglobin (white fibers), and large glycogen reserves

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70
Q

hand muscles have a high percentage of what kinds of fiber types

A

fast glyoclytic fibers for quickness

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71
Q

back muscles have a high percentage of what kinds of fiber types

A

slow oxidative fibers to continually maintain postural support

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72
Q

what determines the distribution of muscle fiber types

A

primarily genes

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73
Q

in long distance runners you are more likely to find what kind of muscle fiber types

A

a higher proportion of slow oxidative fibers in legs

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74
Q

in sprinters you are more likely to find what kind of muscle fiber types

A

higher percentage of fast glyoclytic fibers

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75
Q

muscle twitch

A

a brief contraction to a single stimulus

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76
Q

periods of the twitch

A

latent period
contraction period
relaxation period

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77
Q

latent period

A

time after stimulus but before contraction begins
no change in tension

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78
Q

contraction period

A

time when tension is increasing
begins as power strokes pull thin filaments

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79
Q

relaxation period

A

time when tension is decreasing to baseline
begins when release of crossbridges
generally lasts a little longer than contraction period

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80
Q

as voltage increases more units are

A

recruited to contract

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81
Q

recruitment is also called

A

multiple motor unit summation

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82
Q

multiple motor unit summation

A

explains how muscle exhibit varying degrees of force

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83
Q

treppe

A

increase in twitch tension when stimuli occur 10-20 times per second
voltage is the same for each stimulus and relaxation is complete for each twitch

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84
Q

what causes twitches to get stronger

A

insufficient time to remove all Ca2+ between twitches
increased heat improves enzyme efficiency

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85
Q

wave summation (temporal summation)

A

if stimulus frequency set at about 20 per second..
-relaxation is not completed between twitches
-contractile forces add up to produce higher tensions

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86
Q

incomplete tetany

A

if frequency is increased further, myogram exhibits incomplete tetany
-tension increases and twitches partially fuse

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87
Q

tetany

A

if ferquency is increased further still (40-50 per second), myogram exhibits tetany
-tension trace is a smooth line without relaxation

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88
Q

high frequency stimuli leads to

A

fatigue or decreased tension production

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89
Q

isometric contraction

A

muscle tension is less than resistance
although tension is generated, the muscle does not shorten and no movement occurs.

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90
Q

isotonic contraction

A

muscle tension is greater than the resistance
the muscle shortens (concentric) or lengthens (eccentric) and movement occurs

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91
Q

the tension a muscle produces depends on

A

its length at time of stimulation

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92
Q

fibers at resting length generate

A

maximum contractile force
optimal overlap of thick and thin filaments

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93
Q

fiber at a shortened length generates

A

weaker force
filament movement is limited (actin already closer to opposite Z dics)

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94
Q

fiber at an extended length generates

A

weaker force
minimal thick and thin filament overlap for crossbridge formation

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95
Q

when a muscle contracts we create the

A

greatest amount of tension

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96
Q

cardiac muscle cells

A

short branching fibers with one or two nuclei that contain sarcomeres and many mitochondria for aerobic respiration

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97
Q

intercalated discs

A

join ends of neighboring fibers and contain desmosomes and gap junctions

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98
Q

desmosomes

A

cell-to-cell attachment

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99
Q

gap junctions

A

cell-to-cell communication

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100
Q

what starts contractions of the heart

A

autoryhtmic pacemaker cells, myogenic contraction

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101
Q

heart rate and contraction force is influenced by

A

autonomic nervous system

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102
Q

smooth muscle

A

have fusiform shape (wide in the middle with tapered ends), are smaller tahn skeletal muscle fibers, don’t contain transverse tubules, has a sparse sarcoplasmic reticulum, and lacks sarcomeres and Z discs

smooth

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103
Q

what increases the surface area of smooth muscle

A

caveolae (flask-like invaginations)

104
Q

smooth muscle fibers contrain ____,_____,____ but lack ______

A

actin, myosin, and tropomyosin …. troponin

105
Q

smooth muscle filaments have myosin heads along

A

their entire length meaning they can form many crossbridges

106
Q

calmodulin

A

protein that binds Ca2+ to trigger contraction

107
Q

myosin light-chain kinase (MLCK)

A

enzyme that phosphorylates myosin heads when activated by calmodulin

108
Q

myosin light-chain phosphate

A

enzyme that deposhporylates myosin head (required for relaxation)

109
Q

smooth muscle contraction

A
  1. opening of voltage gated Ca2+ channels
  2. binding of Ca2+ to calmodulin
  3. activation of myosin light chain kinase
  4. activation of myosin head
  5. crossbridge formation, power stroke, reattachment
110
Q

how is the nervous system organized structurally

A

structurally: CNS and PNS
functionally: SNS and MNS

111
Q

CNS contains

A

brain and spinal cord

112
Q

PNS consists of

A

nerves (fiber bundles) and ganglia (clusters of cell bodies along nerves)

113
Q

sensory nervous system

A

detects stimuli and transmits information from receptors to the CNS

114
Q

motor nervous system

A

initirates and transmits information from the CNS to effectors

115
Q

somatic sensory and visceral sensory are part of

A

the sensory nervous system

116
Q

somatic motor and autonomic motor are part of

A

motor nervous system

117
Q

somatic sensory

A

input that is consciously percieved from receptors (eyes, ears, skin)

118
Q

visceral sensory

A

input that is not consciously percieved from receptors of blood vessels and internal organs (heart)

119
Q

somatic motor

A

motor output that is consciously or voluntarily controlled; effector is skeletal muscle

120
Q

autonomic motor

A

motor output is not consciously or is involuntarily controlled; effectors are cardiac muscle, smooth muscle, and glands

121
Q

what are the three main pairs of a neuron

A

cell body (soma)
dendrites
axon

122
Q

cell body

A

plasma membrane encloses cytoplasm
contain nucleus
initiates some graded potentials, receives others from dendrites; conducts these potentials to axon
contains chromatophillic substance (Nissl bodies) made of ribosomes

123
Q

dendrites

A

short, unmyelinated processes branching off cell body
recieve input and transfer it to cell body

124
Q

axon

A

long process emanating from cell body
makes contact with other neurons, muscle cells, or glands
synaptic knobs house synaptic vessicles containing neurotransmitters
axons function to conduct action potentials and then release neurotransmitter at synaptic knobs

125
Q

where is action potential generated

A

in the axon hillock

126
Q

where do axons carry strong action potentials

A

away from cell body to either another neuron or an effector (like a muscle)

127
Q

myelin sheath helps enhance…

A

the conduction velocity of action potential down the length of axon

128
Q

the first neuron is refered to as

A

the presynaptic neuron

129
Q

the second neuron is referred to as

A

the postsynaptic neuron

130
Q

multipolar neuron

A

multiple processes extend directly from cell body; typically many dendrites and one axon; most common type of neuron

examples: all motor neurons; most interneurons

131
Q

bipolar neuron

A

two proesses extend directly from the cell body; one dendrite and one axon; relatively uncommon

examples: some special sense neurons (retina of eye, olfactory epithelium of nose)

132
Q

unipolar neuron

A

single short process extends directly the cell and looks like a T as a result of the fusion of two processes to look like one long axon

examples: most sensory neurons

133
Q

axinomic neuron

A

processes are only dendrites; no axon present
example: interneurons of the central nervous system (CNS)

134
Q

functional classification of neurons

A
  1. sensory neurons
  2. motor neurons
    3.interneurons
135
Q

sensory neurons (afferent neurons)

A

conducts input from somatic and visceral receptors to CNS
most are unipolar ( a few bipolar )

136
Q

motor neurons (efferent neurons)

A

conduct output from CNS to somatic and visceral effectors
all multipolar

137
Q

interneurons (association neurons)

A

receive process and integrate information from many other neurons
communicate between sensory and motor neurons
located within CNS; make up 99% of our neurons
generally multipolar

138
Q

nerve

A

a bundle of parallel axons in the PNS

139
Q

structural classification of nerves

A

cranial nerves : extend from brain
spinal nerves : extend from spinal cord

140
Q

functional classification of nerves

A

sensory nerves
motor nerves
mixed nerves

141
Q

sensory nerves

A

contain sensory neurons sending signals to CNS

142
Q

motor nerves

A

contain motor neurons sending signals FROM CNS

143
Q

mixed nerves

A

contain both sensory and motor neurons
most named nerves are in this category
individual axons in these nerves transmit only one type of information

144
Q

pumps

A

membarne proteins that maintain a concentration gradient by moving substances against their concentration gradient

require cellular energy

145
Q

what kind of pumps are present in neurons

A

sodium-potassium pumps and calcium pumps

146
Q

channels

A

protein pores in the membrane that allow ions to move down their concentration gradients (into or out of cell)
when open they allow a specific type of ion to diffuse

147
Q

leak channels

A

passive channels that are always open for continuous diffusion

148
Q

chemically gated channels

A

normally closed but open when neurotransmitter binds

149
Q

voltage gated channels

A

normally closed but open when membrane charge changes

150
Q

glial cells (neuroglia)

A

nonexcitable support cells found in both the CNS and PNS
smaller but outnumber neurons and account for half the volume of nervous system
capable of mitosis, protect and nourish neurons, provide physical scaffolding for nervous tissue and are critcial for normal function at neural synapses

151
Q

what are the different kinds of glial cells in the CNS

A

astrocytes
ependymal cells
microglial cell
oligodendrocytes

152
Q

astrocyte

A

helps form the blood brain barrier
regulates interstitial fluid composition
provides structural support and organization to the CNS
assists with neuronal development
replicates to occupy space of dying neurons

153
Q

ependymal cell

A

lines ventricles of brain and central canal of spinal cord
assists in production and circulation of cerebrospinal fluid

154
Q

microglial cell

A

phagocytic cells that move through CNS
protects the CNS by engulfing infectious agents and other potential harmful substances

155
Q

oligodendrocytes

A

myelinates and insulates CNS axons
allows faster action potential propogation along axons in the CNS

156
Q

glial cells of the PNS

A

satellite cells
neurolemmocytes

157
Q

satellite cells

A

arranged around neuronal cell bodies in a ganglion
electricity insulate and regulate the exchange of nutrients and wastes

158
Q

neurolemmocytes (schwann cells)

A

elongated flat cells that ensheath PNS axons with myelin which allows for faster action potential propagation

159
Q

myelination

A

process of wrapping an axon with myelin

160
Q

myelin

A

several layers of membrane of glial cells
contain a high lipid content which gives it a glossy white appearance and insulates axon

161
Q

myelination of PNS axons

A
  1. neurolemocyte starts to wrap around portion of axon
  2. neurolemmocyte cytoplasm and plasma membrane begin to form consecutive layers around the axon as wrapping continues
  3. the overlapping inner layers of the neurolemmocyte plasma membrane form the myelin sheath
  4. eventually the neurolemmocyte cytoplasm and nucleus are pushed to the periphery of the cell to form the neurilemma
162
Q

neurilemma

A

neurolemmocyte’s cytoplasm and nucleus are pushed to periphery

163
Q

neurofibril nodes (nodes of ranvier)

A

caps between neurolemmocytes

164
Q

myelination of CNS axons

A

one oligodendrocyte can myelinate 1mm of multiple axons, each at multiple spots
no neurilemma formed
neurofibril nodes between adjacent wrapped segments

165
Q

where are unmyelinated axons present

A

in both PNS and CNS

166
Q

unmyelinated axons in PNS

A

axon sits in depressed portion of neurolemmocyte
not fully ensheathed

167
Q

unmyleinated axons in CNS

A

not associated with oligodendrocytes

168
Q

synapse

A

place where neuron connects to another neuron or an effector

169
Q

chemical synapse

A

presynaptic neuron’s axon terminal produces signal
postsynaptic neuron recieves signal most commonly with dendrites

170
Q

synaptic cleft

A

small fluid filled gap between two neurons

171
Q

events in synaptic communication

A

neurotransmitter molecules released from vesicles of synaptic knob into cleft
transmitter diffuses across cleft and binds to postsynaptic receptors
binding of neurotransmitter to receptor initiates poststynaptic potential

172
Q

synaptic delay

A

time it takes for all synaptic communication to occur
usually between .3-.5 nanoseconds

173
Q

characteristics of resting neurons

A

ions are unevenly distributed across the plasma membrane due to the actions of pumps
gated channels are close in the functional segments of cell
there is an electrical charge difference

174
Q

in a resting neuron there is a higher concentration of K+ in

A

the cytosol versus interstitial fluid

175
Q

in a resting neuron there is a higher concentration of Na+, Cl-, Ca2+ in

A

interstitial fluid than in cytosol

176
Q

what is resting membrane potential in a resting neuron

A

-70mV

177
Q

what part of neurons is more negative

A

cytosol compared to IF

178
Q

what is the most important factor in setting RMP

A

K+ diffusion

179
Q

K+ diffusion

A

K+ diffuses out of the cell due to concentration gradient
K+ diffusion is limited by electrical gradient

180
Q

Na+ diffusion

A

diffuses into the neuron due to its concentration gradient and the electrical gradient

181
Q

role of Na+/K+ pumps

A

by pushing out 3 positive charges and pushing in only 2 negative, the pump contributes about -3 mV (of the -70 mV total)
more importantly it maintains the concentration gradients for these ions

182
Q

what triggers postsynaptic potential

A

reception of neurotransmitters

183
Q

what happens when a neurotransmitter binds to a chemically gated ion channel

A

it opens them

184
Q

what happens when a neurotransmitter binds to a chemically gated ion channel

A

it opens them allowing ions to flow through the membrane changing its electrical potential

185
Q

graded potential

A

the voltage change that can vary in size

186
Q

what does the direction of the potential depend on

A

what type of ion channel opens

187
Q

if na+ channels open…

A

na+ diffuses IN and membrane becomes LESS negative

188
Q

if Cl- channels open…

A

Cl- diffuses IN and membrane becomes MORE negative

189
Q

if K+ channels open…

A

K+ diffuses out and membrane becomes MORE negative

190
Q

depolarized

A

when a cell is less negative than RMP

191
Q

hyperpolarized

A

when a cell is more negative than RMP

192
Q

excitatory postsynaptic potentials (EPSPs)

A

depolarizations caused by cation entry

193
Q

generation of EPSP

A
  1. neurotransmitter released from presynaptic neurons binds to postsynaptic neuron receptors which are chemically gated caiton channels causing them to open
    2.na+ flows into neuron faster than K+ flows out
  2. inside of neuron becomes more positive (less negative); called EPSP (-68 mV)
  3. EPSP proopagates toward the initial segment
194
Q

inhibitory postsynaptic potentials (IPSPs)

A

hyperpolarizations caused by cation exit or anion entry

195
Q

generation of IPSP

A
  1. neurotransmitter released from presynaptic neurons binds to postsynaptic neuron receptors, which are either chemically gated K+ channels or chemically gated Cl- channels causing them to open
  2. either k+ flows out of, or Cl- flows into, the neuron, depending on the type of channel stimulated
  3. inside of neuron becomes more negative; called IPSP (-72 mV)
  4. IPSP propahates toward the initial segment
196
Q

initial segment

A

summation of EPSPs and IPSPs

197
Q

where does summation of EPSPs and IPSPs occur

A

at axon hillock

198
Q

the summation of EPSPs and IPSPs may or may not reach threshold membrane potential which initates

A

an action potential

199
Q

threshold

A

minimum voltage change required

200
Q

what is the typical threshold for an action potential

A

-55 mV

201
Q

if threshold is reached at axon hillock what happens

A

voltage gated channels open and an action potential is generated

202
Q

all or none law

A

if threshold is reached action potential is generated and propagated down axon
if threshold isn’t reached voltage gated channels stay closed but no action potential

203
Q

does the value of threshold reached show different intensity

A

no, once threshold is reached the response is the same

204
Q

conductive segment

A

the axon conducts action potentials

205
Q

action potential

A

involves depolarization and repolarization

206
Q

depolarization

A

gain in positive charge as Na+ enter through voltage gated Na+ channels

207
Q

repolarization

A

return to negative potential as K+ exits through voltage gated K+ channels

208
Q

action potential is propagated down

A

the axon to synaptic knob where voltage gated channels open sequentially down axolemma

209
Q

propagation

A

called an impulse or nerve signal

210
Q

action potential: steps in depolarization

A
  1. at RMP voltage gated channels are closed
  2. as Na+ enters from adjacent region, voltage gated Na+ channels open (changes MP to -55mV)
  3. Na+ enters the axon causing the membrane to have a positive potential
  4. Na+ channels close becoming inactive (unable to open) for a time
211
Q

steps in repolarization

A
  1. depolarization slowly opens K+ channels and K+ diffuses out causing negative membrane potential
  2. K+ channels stay open for a longer time, so K+ exit makes cell more negative than RMP (-80mV)
  3. K+ channels eventually close and RMP is reestablished
212
Q

events of action potential

A
  1. unstimulated axon has RMP of -70 mV
  2. graded potentials reach the initial segment and are added together (-70mV - -55 mV)
  3. depolarization occurs when the threshold (-55mv) is reached; voltage gated Na+ channels open and Na+ enters rapidly; reversing the polarity from negative to positive (-55mV - +30mV)
  4. repolarization occurs due to colsure of voltage gated Na+ channels (inactivation state) and opening of voltage gated K+ channels. K+ moves out of the cell and polarity is reversed from positive to negative (+30mV - -70mV)
  5. hyperpolarization occurs when voltage gated K+ channels stay open longer than the time needed to reach resting membrane potential; during this time the membrane potential is less than the resting membrane potential (-70mV - -80mV)
    6.voltage gated k+ channels are closed and the plasma membrane has returned to resting conditions by activity of Na+/K+ pumps
213
Q

refractory period

A

period of time after start of action potential when it is impossible or difficult to fire another action potential

214
Q

absolute refractory period (1ms)

A

no stimulus can initiate another action potential
na+ channels are open but are ianctive
ensures propagation goes toward synaptic knob; doesn’t reverse direction

215
Q

relative refractory period (just after absolute)

A

another action potential is possible (Na+ channels have reset) but the minimum stimulus strength is now greater
some K+ channels are still open cell is slightly hyperpolarized and further from threshold

216
Q

transmissive segment: release of neurotransmitter

A
  1. nerve signal reaches synaptic knob
  2. voltage gated Ca2+ channels open and Ca2+ enters the synaptic knob and binds with proteins associated with synaptic vessicles
  3. synaptic vessicles fuse with the synaptic knob plasma membrane and neurotransmitter is exocytosed
  4. neurotransmitter diffuses across synaptic cleft and attaches to receptors on a muscle
217
Q

where do graded potentials occur

A

in neuron’s receptive region due to ion flow through chemically gated channels

218
Q

graded potentials

A

can be positive or negative in charge
are graded: have larger potential change to stronger stimulus
are local (short distance)

219
Q

where do action potentials occur

A

on neurons conductive region (axon) due to ion flow through voltage gated channels

220
Q

action potentials

A

involve depolarization (Na+ in) and repolarization (K+ out)
all or none once threshold is reached
propagate down entire axon to synaptic knob

221
Q

what does conduction speed depend on

A

axon thickness and myelination

222
Q

what fibers are faster

A

thick axons because they offer less resistance to current flow down the axon

223
Q

where does saltatory conduction

A

on myelinated axons

224
Q

where does action potential occur

A

only at neurofibril nodes which is where axon’s voltage-gated channels are concentrated

225
Q

conductive segment

A

after na+ enters at a node it starts a rapid positive current down the inside of the axon’s myelinated region
the current becomes weaker with distance but still strong enough to open voltage-gated channels at the next node
full action potential occurs at the node and the process repeats : impilse seemingly jumping from node to node

226
Q

what are the four chemical classes of neurotransmitters

A

acetylcholine
biogenic amines (monoamines)
-catecholamines
-indoalmines
amino acids
neuropeptides

227
Q

what is an example of catecholamines

A

dopamine

228
Q

what is an example of indoalines

A

seratonin

229
Q

amino acids examples

A

glutamate glycine and GABA

230
Q

neuropeptides examples

A

endorphins

231
Q

functional classification of neurotransmitters

A

effect
action

232
Q

excitatory transmitters cause

A

EPSPs

233
Q

inhibitory transmitters cause

A

IPSPs

234
Q

classes by action

A

direct transmitters bind to receptors that are chemically gated channels (immediate postsynaptic potential)
indirect transmitters bind to receptors that involve G-proteins and second messengers in order to cause postsynaptic potential

235
Q

what is the difference between direct and indirect transmitters

A

indirect transmitter involve G-proteins and a secondary messenger to cause postsynaptic potential

236
Q

acetylcholine is used in the PNS to stimulate

A

skeletal muscle

237
Q

ACH is used in CNS to

A

increase arousal and attention, enhances memory

238
Q

what is ach synthesized from

A

acetate and choline which is stored in synaptic vesicles

239
Q

how is ach cleared from the cleft

A

by being broken down to acetate and choline by acetylcholinesterase

240
Q

what happens to acetate and choline after it has been used

A

it is taken up by presynaptic cell for recycling

241
Q

removal of neurotransmitter from the synaptic cleft can occur in varried ways. what are the 3 ways?

A

enzymes might degrade trasmitter
presynaptic transporters might important transmitter (“reuptake”)
some transmitter diffuses away from synapse reabsorbed by glia

242
Q

how do drugs influence transmitter removal

A

selecttive serotonin reuptake inhibitors treat depression
galantamine hydrobromide is an acetylcholinesterase inhibitor used to treat alzheimer disease

243
Q

what does ACH effect on target cell depend on

A

the receptor

244
Q

nicotinic receptor

A

directly causes EPSP

245
Q

muscarinic receptor

A

engages G protein and 2nd messenger and indirectly leads to EPSP or IPSP

246
Q

neuromodulators

A

chemicals that alter responses of local neurons

247
Q

faciliation

A

modulation that causes greater response in postsynaptic neuron
may increase amount of neurotransmitter in cleft or number of postsynaptic receptors

248
Q

inhibition

A

modulation that causes weaker response
may decrease amount of neurotransmitter in cleft or number of postsynaptic receptors

249
Q

neuronal pools (neuronal circuits)

A

groups neurons arranged in specific patterns

250
Q

what are the 4 types of circuits

A

converging
diverging
reverberating
parallel-after-discharge

251
Q

converging circuit

A

input converges at a single postsynaptic neuron

ex. multiple sensory inputs synapse on neurons in the salivary nucleus. sights, sounds, and smells, or cooking lead to one output: salivation

252
Q

diverging circuit

A

spreads information from one presynaptic neuron to several postsynaptic neurons

example: neurons in brain that control walking send commands to several different muscles for proper balance, posture, and motion

253
Q

reverberating circuits

A

use feedback to produce repeated cyclical activity
once started it stays active until there is an inhibitory stimulus or synaptic fatigue

example: circuits that keep us breathing regularly during sleep

254
Q

parallel-after-discharge circuits

A

input transmitted simultaneously along several paths to a postsynaptic cell
since paths vary in number of synapses, signal arrives at postsynaptic cell at various times

believed to be involved in higher-order thinking

255
Q

reflexes

A

a rapid involuntary response caused by a stimulus that is preprogrammed, involuntary, and always the same

256
Q

what is the importance of a reflex

A

we respond to a potentially detrimental stimulus immediately and awareness comes later

257
Q

steps of a reflex

A
  1. stimulus activates receptor
  2. nerve signal is propagated through sensory neuron to the spinal cord
  3. nerve signal is processed int the integration center by interneurons
  4. nerve signal is propagated by motor neuron to effector
  5. effector responds

Human Anatomy and Physiology (5 decks)

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