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Anatomy & Physiology 1 > Exam 3: Muscles, Intro to Nervous system > Flashcards

Exam 3: Muscles, Intro to Nervous system Flashcards

1
Q

What are the 3 types of muscles?

A

Skeletal muscle, smooth muscle, cardiac muscle

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2
Q

What are the functions of skeletal muscle?

A

locomotion (physical movement), posture, respiration

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3
Q

describe Skeletal muscle

A

voluntary (stimulated by motor neuron)

striated

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4
Q

What are the functions of smooth muscle?

A

contraction of hollow organs, vasoconstriction, vasodilation

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5
Q

describe smooth muscle

A

most widely distributed muscle type (in hollow organs & blood vessels)

involuntary (enteric and autonomic nervous system regulation - not controlled consciously)

Some are autorhythmic (initiate contraction w/o external nervous stimulation - muscles can self-contract)

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6
Q

what are the functions of cardiac muscle?

A

contraction of heart chambers

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7
Q

describe cardiac muscle

A

only found in heart

involuntary (regulated by autonomic nervous system)

Autorhythmic

striated

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8
Q

What are the connective tissues of muscles?

A

fascicles and coverings

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9
Q

what are fascicles?

A

bundles of muscle fibers

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10
Q

what are the coverings of muscles?

A

endomysium - around the fiber

perimysium - around the fascicle

epimysium - around the muscle

Muscular fascia - superficial to to the epimysium, separates/ compartmentalizes muscles

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11
Q

what do connective tissues of muscles do?

A

extend to form tendons

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12
Q

What are the parts of innervation and vasculature of muscles

A

nerve stimulation

blood vessels

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13
Q

how does nerve stimulation occur

A

motor neurons (like the sciatic nerve)

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14
Q

describe the blood vessels of muscles

A

capillary beds around muscle fibers

muscle blood vessels are supplied and drained by arteries and veins

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15
Q

what are the cells of muscles

A

myofibrils

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16
Q

Parts of myofibrils

A

actin myofilaments (thin)

myosin myofilaments (thick)

actin and myosin form sarcomeres

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17
Q

what are sarcomeres

A

functional unit of skeletal muscle

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18
Q

what do sarcomeres form

A

striations

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19
Q

Describe light bands

A

I bands (isotropic, uniform) that extends to ends of myosin myofilaments

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20
Q

Describe dark bands

A

A bands (anisotropic, not uniform) that extends the length of myosin

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21
Q

what do light and dark bands make

A

striations

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22
Q

Describe the H zone of striations

A

only myosin is present

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23
Q

describe m line of striations

A

holds myosin in place

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24
Q

Parts of Actin

A

F actin (“fibrous”) - forms “strands” of actin

Tropomyosin - dark line of actin

G actin (globular) - forms “beads” of actin: there are 2 strands of beads (proteins) twisted together in actin

Troponin - has 3 subunits
1. binds to G actin
2. binds to calcium ions (Ca++)
3. binds to tropomyosin

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25
Q

what is the function of myosin heads

A

binds to actin molecules = cross bridge

contraction of muscle (hinge region bends and straightens)

Have ATPase (enzyme) to break down ATP & power movement

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26
Q

Describe the sliding filament model

A

Actin myofilament sliding over the myosin myofilament:
-shortening of sarcomere
-shortening leads to muscle contraction

Relaxation=lengthening of sarcomere

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27
Q

Describe the resting membrane potential

A

Voltage (charge) difference across cell membrane when cell is at rest

(inside of cell is more negatively charged than outside of cell)

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28
Q

what is a resting membrane potential caused by

A

more positive (+) ions outside cell

fewer positive (+) ions inside the cell (some + ions leak out of cell)

so there is a negative charge inside the cell when at rest

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29
Q

How does membrane permeability occur?

A

Via channels in the plasma membrane

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30
Q

Describe how voltage-gated ion channels work

A

open or close in response to a certain membrane potential (charge in cell)

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31
Q

Describe how Ligand-gated ion channels work

A

open or close in response to presence/absence of a chemical signal

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32
Q

describe an inactive site of a ligand-gated ion channel

A

no ligand is present
channel is closed

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33
Q

describe an active site of a ligand-gated ion channel

A

ligand bound
channel is open
Sodium ions (Na+) enter cell

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34
Q

What is an action potential (AP)

A

temporary reversal of voltage (charge) inside cell —> voltage within cell becomes temporarily positive

“signal firing”

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35
Q

What are the stages of an action potential

A
  1. Resting Membrane Potential
    -no ion channels open

Stimulus
-some Na+ channels open
-Na+ starts to move into cell (start of depolarization)

  1. Depolarization (2nd part)
    -Voltage-gated Na+ channels are open
    -Na+ rushes into cell
  2. Repolarization
    -Na+ channels close
    -voltage-gated K+ channels open
    -K+ rushes out of cell
  3. Hyperpolarization
    -“undershoot”
    -excess K+ moving out of cell
  4. Back to resting membrane potential
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36
Q

what are some action potential concepts

A

all-or-nothing principle
-if threshold is reached (-55 millivolts), entire process of AP occurs
-if threshold is not reached, nothing happens

Propagation of AP
-triggers APs all along axon toward axon terminals

Strength of signal
-strong stimulus=increased AP frequency (not larger APs)

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37
Q

What do axon terminals do

A

will release neurotransmitter (chemical signal) —> stimulates muscle

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38
Q

What is a neuromuscular junction

A

site of transmission of action potential from motor neuron to muscle fiber

synapse of neuron on muscle fiber

Acetylcholine (Ach), important neurotransmitter released

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39
Q

describe what occurs at a neuromuscular junction

A
  1. Action potential arrives at axon terminal
  2. Voltage-gated calcium (Ca++) channels open
    -Ca++ rushes IN to axon terminal
  3. Calcium ions (Ca++) triggers vesicles to release acetylcholine (Ach) into synaptic cleft
  4. Acetylcholine (Ach) diffuses across synaptic cleft
  5. Acetylcholine (Ach) binds to receptors on muscle fiber
  6. Na+ (sodium) channels open
    -Na+ moves into muscle fiber
    -triggers action potential (AP) in muscle fiber

…. —-> Muscle contraction

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40
Q

How is acetylcholine rapidly cleared?

A

Acetylcholinesterase
-breaks down Acetylcholine (Ach) in synaptic cleft —>
-ensures Ach does not accumulate & constantly stimulate muscle
-Broken down parts are recycled within axon after metabolism

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41
Q

what is excitation-contraction coupling

A

conversion of neural signals into physical process of contraction

Neuron action potential —> Muscle action potential —> contraction

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42
Q

what are T-tubules

A

transverse tubules
-infoldings of sarcolemma

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43
Q

what is the sarcoplasmic reticulum

A

modified smooth ER
-stores Calcium ions (Ca++)
-releases Ca++ into sarcoplasm (muscle fiber cytoplasm) in response to muscle action potential

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44
Q

What is the sarcolemma

A

plasma membrane of muscle fiber

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45
Q

Describe the process of neurotransmitter release to muscle contraction

A
  1. Acetylcholine secretion from motor neuron, Ach binds to receptors on muscle fiber (detailed steps at neuromuscular junction)
  2. Increased influx of sodium ions (Na+) into muscle fiber —> triggers muscular action potential
  3. Propagation of action potential across muscle fiber
  4. Depolarization of membrane and release of calcium ions (Ca++) from sarcoplasmic Reticulum (SR)
    -due to: travelling of action potential into the inside of the fiber (T-tubules)
  5. Cross-bridge formation & sliding filaments (or muscle contractions)
    -due to: Ca++ binding to troponin
    -troponin-tropomyosin complex moves out of the way, revealing active (binding) sites for myosin to bind on actin
  6. Calcium ions (Ca++) goes back into sarcoplasmic reticulum (SR)
    -restoration of filaments to original positions
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46
Q

describe cross-bridge cycling

A

repeated interaction of myosin head & actin myofilament
-cross-bridge formation
-sliding myofilaments
-release…and repeat

Happens many times in a single muscle contraction

Needs ATP for movement/contraction to occur

47
Q

what does relaxation require

A

energy

48
Q

Describe muscle relaxation process

A

-No more release of acetylcholine (Ach) at neuromuscular junction —->
stops action potentials along sarcolemma —->
stops Ca++ release from Sarcoplasmic reticulum (SR)

-movement of Ca++ back into SR
—->
energy-dependent process
-Ca++ actively pumped back into SR (requires ATP)
-Restoration of membrane potential (negative charge) —->
Na+/K+ pumps to do this (requires ATP)

49
Q

What is a motor unit

A

motor neuron and ALL the muscle fibers it innervates (synapses to)

Allows muscles to contract as a single unit

50
Q

What is a muscle twitch

A

A single contraction of muscle in response to stimulus
-due to action potential in one or more muscle fibers from motor neuron

51
Q

what are the phases of muscle twitch

A

lag/latent - time between stimulus & start of contraction

contraction - start of contraction to peak of tension in muscle

Relaxation - from peak of muscle tension back to fully relaxed

NOT AN AP

52
Q

how do muscles respond

A

in a graded fashion=greater stimulus on muscles produces greater strength of contraction

53
Q

what is recruitment

A

increased number of motor units stimulated (produces higher force of contraction)

Number of fibers in motor unit vary based on motion generated

54
Q

Describe Recruitment example of playing banjo

A

delicate, precise movement –> more motor units –> but fewer fibers per motor unit

55
Q

Describe recruitment example of kicking something big over

A

large, less precise movement –> fewer motor units –> but lots of fibers per motor unit

56
Q

Define summation

A

additional twitches before muscle has fully relaxed (also produces higher force of contraction)

57
Q

Define Incomplete Tetanus

A

partial relaxation of muscle between contraction

58
Q

Define complete tetanus

A

no relaxation of muscle
*rapid frequency of stimuli
*sustained contraction!

59
Q

what leads to tetanus

A

high frequency stimulation
-this can cause fatigue, Additional Ca++ in muscle fiber causes greater force of contraction

60
Q

Define treppe

A

“staircase” of increased frequency of stimulation
-increasing force of contraction in response to same level of stimulation
-eventually reach the maximum level

Think of warming up before full exercise/workout
-increases muscle efficiency with progressive force

61
Q

Describe isometric contraction

A

no change in muscle length, no movement of limbs

increase of tension/force in muscle during contraction

62
Q

what is an example of isometric contraction

A

maintenance of posture

63
Q

Describe Isotonic contraction

A

change in muscle length, movement of limbs

tension produced by muscle is constant

change in length of muscle

64
Q

Example of isotonic contraction

A

moving arms or fingers like when doing a bicep curl

65
Q

what are the 2 types of Isotonic contraction

A

concentric contraction
eccentric contraction

66
Q

define concentric contraction

A

working muscle shortens

tension of muscle great enough to overcome the weight load

(ex. curling bicep up)

67
Q

define eccentric contraction

A

working muscle lengthens

Tension being maintained against the load

(ex. releasing bicep curl down with control)

68
Q

define muscle tone

A

constant tension produced by muscles for long periods
-small percentage of motor units contracting asynchronously

Maintenance of posture

69
Q

define fatigue

A

the diminished ability for muscles to generate force

psychological leads to physiological effect

physiologically: accumulation of metabolites & lack of glycogen may interfere with Ca++ release from Sarcoplasmic Reticulum

70
Q

Describe slow twitch/ Type I muscle fibers

A

-smaller fiber diameter

-slower response to nervous stimulation

-extensive vasculature

-higher mitochondria & myoglobin (oxygen storing molecule) concentrations
——>darker red appearance due to myoglobin

-slow ATP breakdown

-good for long sustained movements, not great for big powerful movements

71
Q

Example of when slow twitch fibers are used

A

ultramarathon running

72
Q

Describe fast twitch/ Type II fibers

A

-larger fiber diameter

-faster response to nervous stimulation

-less vasculature

-less myoglobin & mitochondria
—->lighter (pink) color

-Fast ATP breakdown

-higher glycogen (reserve of glucose) content

-more susceptible to fatigue, but good for large powerful movements

73
Q

Example of when fast twitch fibers are used

A

Olympic powerlifting

74
Q

What are the 2 major subdivisions of the nervous system

A

Central Nervous System (CNS)
Peripheral Nervous System (PNS)

75
Q

What are the parts of the central nervous system

A

brain
spinal cord

76
Q

functions of central nervous system

A

-integration of information
-generate memories
-control of various system
-mentation (thinking, learning, understanding)

77
Q

what 2 kinds of nerves have we discussed?

A

cranial
spinal nerves

78
Q

where do cranial nerves originate from

A

the brain

79
Q

where do spinal nerves originate from

A

spinal cord (they then extend laterally)

80
Q

how many pairs of cranial nerves do humans have

A

12 pairs

81
Q

how many pairs of spinal nerves do humans have

A

31 pairs

82
Q

What are the parts of the peripheral nervous system

A

-sensory receptors
-nerves
-ganglia
-plexuses

83
Q

What is the function of sensory receptors

A

detection of various sensations

84
Q

what is the function of nerves

A

links between sensory receptors and central nervous system

85
Q

what are ganglia

A

cluster of neuron cell bodies located outside of the central nervous system

86
Q

what are plexuses

A

“braids” of neurons and axons located outside of the central nervous system

87
Q

what are the subdivisions of the peripheral nervous system?

A

Afferent (sensory) division
Efferent (motor) division

88
Q

What does the afferent (sensory) division of the PNS do

A

-transmission of signals from sensory receptors TO the CNS via sensory neurons

-entry point to the CNS (dorsal horn of the spinal cord)

89
Q

what does the efferent (motor) division of the PNS do

A

-transmission of signals AWAY from the CNS to the organs via motor neurons

-exit point from CNS (ventral horn of the spinal cord)

90
Q

What is the division of the efferent (motor) division of the PNS

A

Autonomic Nervous System (ANS)

91
Q

what is the function of the autonomic nervous system (ANS)

A

involuntary regulation of functions in the body

Ex: heart rate, pupil diameter, blood pressure, blood vessel diameter, etc.

92
Q

what are the 2 branches of the Autonomic Nervous system

A

sympathetic branch (“fight-or-flight”)

parasympathetic branch (“rest-and-digest”)

93
Q

what does the enteric part of peripheral nervous system do

A

regulation of the GI tract function
*plexuses on walls of GI tract

94
Q

What neural tissue exists in nervous system

A

neuron
neuroglial cells

95
Q

what is the function of a neuron

A

generate, send, and receive neural signals

96
Q

What is the function of neuroglial cells

A

support and protection for neurons/nervous system

97
Q

what are the parts of a neuron

A

neuron cell body
dendrites
axon
axon terminals
myelin sheaths
nodes of Ranvier

98
Q

what is the function of dendrites

A

receive signals from other neurons

99
Q

what is the function of axons

A

transmit signals

100
Q

what is the function of axon terminals

A

send signals to other neurons (or organs like the muscles)

101
Q

how does transmission of neural signal occur

A

across the entire length of the axon
-only moves from trigger zone to axon terminals, not backwards

102
Q

what are the neuroglia of the CNS

A

Oligodendrocytes

103
Q

what are the neuroglia of the PNS

A

Schwann cells

104
Q

what is the function of Oligodendrocytes and Schwann cells

A

produce myelin sheaths that surround axons of some neurons

105
Q

what is myelin

A

lipid-rich insulation

106
Q

does myelination of axon speed up action potential function

A

yes

107
Q

how does myelination of axon speed up action potential function

A

Saltatory conduction

108
Q

what is saltatory conduction

A

it means “jump”
-APs only occur at node of Ranvier
-voltage-gated Na+ and K+ channels concentrated at the nodes; myelinated regions of axon have almost no channels

-unmyelinated axons have channels along its length —> slower propagation of APs

109
Q

Myelinated axons=

A

faster conduction

110
Q

thicker myelin sheaths=

A

faster conduction

111
Q

greater axon diameter=

A

faster conduction bc there is a greater surface area for Na+ channels

112
Q

Large myelinated axons conduct at

A

120 m/s (ex. skeletal muscle neuron)

113
Q

small unmyelinated axons conduct at

A

0.7 m/s (ex. GI tract neuron)

114
Q

what is AP speed of conduction related to

A

urgency of information
Ex. response for digestion vs. tripping and falling

Anatomy & Physiology 1 (8 decks)

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