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A&P Lecture Exam 2 > CH 9 > Flashcards

CH 9 Flashcards

1
Q

7 functions of the Muscular System

A 
bodily movement
maintenance of posture
production of body heat
heart beat
respiration
communication
constriction of organs
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2
Q

Muscular System: Functions: Bodily movement

A

contraction of skeletal m. is responsible for overt movements of the body

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3
Q

Muscular System: Functions: maintenance of posture

A

skeletal m. constantly maintains tone and keeps us up right

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4
Q

Muscular System: Functions: production of body heat

A

when skeletal m. contract, heat is released as a byproduct

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5
Q

Muscular System: Functions: heart beat

A

contraction of cardiac m. results in the heart beat and allows blood to be pumped to the rest of the body

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6
Q

Muscular System: Functions: respiration

A

skeletal m. of the thorax responsible for the movements necessary for respiration

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7
Q

Muscular System: Functions: communication

A

skeletal m. are involved in all aspects of communication (writing, speaking, facial expression)

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8
Q

Muscular System: Functions: constriction of organs and vessels

A

contraction of smooth m. within the walls of organs and vessels causes constriction

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9
Q

4 functional characteristics of muscle

A

contractility
extensibility
excitability
elasticity

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10
Q

Functional Characteristics of Muscle: Contractility

A

-the ability to shorten forcibly

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11
Q

muscular contraction is an active process in which…

A

muscle cells generate the forces causing muscle to shorten

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12
Q

muscular relaxation is a passive process and results….

A

from forces outside of the muscle itself

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13
Q

Functional Characteristics of Muscle: Excitability

A

the ability to receive and respond to stimuli

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14
Q

muscles normally contract as a result of…

A

stimulation by nerves

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15
Q

Functional Characteristics of Muscle: Extensibility

A

-the ability to be stretched or extended

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16
Q

T/F: Muscles cannot stretch beyond their normal resting length and still contract

A

False, muscles CAN stretch beyond their normal resting length AND STILL contract

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17
Q

Functional Characteristics of Muscle: Elasticity

A

the ability to recoil and resume original resting length after being stretched

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18
Q

Skeletal, cardiac and smooth m. differ in terms of their:

A

structure
location
function
means of activation

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19
Q

Each muscle is a discrete organ composed of…

A

muscle tissue, connective tissue, blood vessels, nerve fibers

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20
Q

Skeletal m. is responsible for…

A

most body movements (locomotion, facial expression, posture, respiratory movements)

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21
Q

Skeletal muscle stabilizes…

A

joints and generates heat

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22
Q

skeletal muscle is under what kind of control?

A

voluntary

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23
Q

smooth muscle is found in…

A

the walls of hollow organs and tubes, interior of the eye, and the walls of blood vessels
ex: eye, skin (arrector pili)

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24
Q

smooth m. contracts…

A

involuntarily (under unconscious control)

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25
Q

smooth m. regulates…

A

flow through blood vessels

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26
Q

what type of muscle helps maintain blood pressure?

A

smooth

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27
Q

what type of muscle squeezes or propels substances through organs?

A

smooth

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28
Q

cardiac m. contractions provide the force to…

A

move blood through the vascular system

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29
Q

Muscle tissue: Cardiac: Autorhytmic

A
  • contracts spontaneously at somewhat regular intervals

- nervous or hormonal stimulation isn’t always required for contraction

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30
Q

function of smooth m:

A 
moving food through digestive tract
emptying urinary bladder
regulating blood vessel diameter
changing pupil size
contracting many gland ducts
moving hair
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31
Q

function of cardiac m:

A

pumping blood

contractions provide force to propel blood through blood vessels

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32
Q

Nucleus # in skeletal m:

A

multiple nuclei, peripherally located

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33
Q

Nucleus # in smooth m:

A

single, centrally located

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34
Q

Nucleus # in cardiac m:

A

single, centrally located

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35
Q

T/F: Skeletal muscle is striated

A

True

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36
Q

T/F: cardiac muscle is not striated

A

false, it is striated

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37
Q

Skeletal m is composed of…

A

skeletal muscle cells fibers called myocytes

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38
Q

Myocytes

A
  • elongated cells
  • multiple nuclei located of the fiber near the PM
  • individual fibers can extend from one end of the muscle to the other
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39
Q

striations in skeletal m are due to…

A

the arrangement of actin and myosin myofilaments

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40
Q

skeletal muscle contracts…

A

rapidly, but tires easily

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41
Q

3 types of muscular fascia:

A

epimysium
perimysium
endomysium

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42
Q

muscular fascia

A

sheets of CT that separate and compartmentalize muscles

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43
Q

epimysium

A
  • Most superficial

- dense collagenous CT that surrounds the ENTIRE muscle

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44
Q

perimysium

A

fibrous CT that surrounds groups muscle fibers known as fascicles

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45
Q

endomysium

A

fine sheath of CT composed of reticular fibers that surrounds each individual muscle fiber

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46
Q

CT connects muscles to…

A

other structures

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47
Q

CT provides a pathway for…

A

nerves and blood vessels to reach individual muscle cells/fibers

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48
Q

sacrolemma

A

PM of a muscle cell

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49
Q

sacroplasm

A

cytoplasm of a muscle cell

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50
Q

myofibrils

A

densely packed, rod-like contractile elements that extend from one end of the muscle fiber to the other

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51
Q

what makes up most of the muscle volume?

A

myofibrils

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52
Q

myobfibrils are composed of…

A

actin and myosin

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53
Q

Actin and Myosin form…

A

highly ordered units called sarcomeres

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54
Q

sarcomeres are joined…

A

end to end to form myofibrils

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55
Q

Myofilaments: Actin: Thin Myofilament

A

consist of 2 helical polymer strands of F actin, tropomyosin and troponin

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56
Q

Myofilaments: Actin: G (globular) actin

A

contains the active sites to which myosin heads attach during contraction

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57
Q

Myofilaments: Actin: Troponin

A

molecules are attached at the specific intervals along the actin myofilaments and have Ca2+ binding sites

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58
Q

troponin also attaches to…

A

tropomyosin

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59
Q

Myofilaments: Actin: Tropomyosin

A

-molecules located along the groove between the twisted strands of F actin

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60
Q

Tropomyosin covers the active sites on…

A

G actin when Ca2+ is not bound to troponin

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61
Q

Myofilaments: Myosin

A

-thick myofilament, composed of myosin molecules

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62
Q

A crossbridge is formed when…

A

a myosin head binds to the active sites on G actin

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63
Q

Myosin Head

A

contains ATPpase which breaks down ATP

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64
Q

Hinge Region

A

enables the head to move

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65
Q

Rods

A

-attach to each other and are arranged so that the heads of the myosin molecules are located at each end of the myofilament

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66
Q

Sarcomere

A

smallest individual contractile unit within a muscle

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67
Q

Sarcomeres are bound on…

A

either end by Z disks; attach to actin myofilaments

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68
Q

how many actin myofilaments surround each myosin myofilament?

A

6

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69
Q

why do myofibrils appear to be striated?

A

Due to the organization of actin and myosin myofilaments within sarcomeres

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70
Q

A Band

A

-extends the length of the myosin myofilaments within a sarcomere

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71
Q

what gives A bands their dark appearance?

A

the overlapping of actin/myosin at both ends of the band

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72
Q

Z disk

A

coin shaped sheet of proteins (connectins) that anchors actin and connects sarcomeres to one another

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73
Q

H zone

A
  • center of each A band where the myofilaments DO NOT overlap
  • only myosin present
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74
Q

M line

A
  • dark line in the middle of the H zone

- delicate filaments that attach to the center of the myosin myofilaments (helps hold the myosin in place)

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75
Q

why does the M line appear darker?

A

due to the presence of the protein desmin

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76
Q

I band

A

only contains actin myofilament

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77
Q

during contraction, actin…

A

slides past myosin to shorten the sarcomeres

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78
Q

T/F: Actin and myosin change length during contraction

A

FALSE, they do not change length, only position

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79
Q

during relaxation, sarcomeres lengthen because…

A

of an external force, like contraction of antagonistic muscles (muscles that produce the opposite effect)

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80
Q

the nervous system stimulates muscles to contract through…

A

electrical signals called action potentials

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81
Q

Resting membrane potential:

A
  • charge difference across the PM

- must exist for APs to occur

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82
Q

The inside of the RMP is…

A

negative, compared to the outside in a resting cell

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83
Q

An action potential is a reversal of the…

A

RMP so that the inside of the PM becomes positive (depolarizes)

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84
Q

Ion channels assist with…

A

production/spread of action potentials

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85
Q

when a cell is stimulated, the permeability characteristics of the PM…

A
  • change as a result of the opening of certain ion channels

- diffusion cross these channels changes the charge across the PM and produces an AP

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86
Q

2 types of gated ion channels help produce APs:

A

voltage gated

ligand gated

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87
Q

Ligand

A

molecule that binds to a receptor located in the PM

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88
Q

Ligand gated channels: receptor

A

protein or glycoprotein with a receptor site to which a ligand can bind

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89
Q

Ligand gated channels: gates open in response to…

A

a ligand binding to a receptor that is part of the ion channel

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90
Q

Ligand gated channels: Step 1 of Gates opening:

A

motor neurons that supply skeletal m. release the neurotransmitter acetylcholine (ACh)

91
Q

Ligand gated channels: Step 2 of Gates opening:

A

ACh binds to ligand gated Na+ channels in the membranes of muscle fibers

92
Q

Ligand gated channels: Step 3 of Gates opening:

A

Na+ channels open, allowing Na+ to enter the cell

93
Q

gated channels open and close in response to…

A

small voltage changes across the PM

94
Q

Voltage-Gated Channels: Process of Gates opening

A
  1. ) when a nerve or muscle fiber is stimulated, the charge difference across the PM changes
  2. ) This produces a voltage change that causes voltage-gated ion channels to open/close
95
Q

what are important voltage-gated ion channels in muscles?

A

Na+
K+
Ca2+

96
Q

In RMP, voltage-gated Na+ channels and voltage-gated K+ channels are..

A

closed

97
Q

the outside of the PM is…

A

positively charged compared to the inside

98
Q

Depolarization results from…

A

an increase in the permeability of the PM to Na+

99
Q

if depolarization reaches threshold..

A

an AP is produced

100
Q

APs result from…

A

the opening of many Na+ channels

101
Q

the inward movement of Na+…

A

makes the inside of the membrane more positive

102
Q

re-polarization occurs when…

A

Na+ channels close and K+ channels open briefly

103
Q

re-polarization is caused when…

A

Na+ movement into the cell stops and K+ movement out of the cell increases

104
Q

APs occur in what kind of fashion?

A

all or none

105
Q

sub-threshold stimulus

A
  • produces no AP

- no contraction

106
Q

threshold stimulus

A
  • a stimulus at or above threshold will produce an AP
  • depolarization
  • contraction
107
Q

once an AP begins…

A

all of the ion channels changes proceed without stopping

108
Q

APs occur in…

A

a very small area of the PM

109
Q

APs do not affect…

A

the entire PM at once

110
Q

T/F: APs can’t propagate across PM

A

False, they can propagate/travel across PMs

111
Q

APs can stimulate the production of…

A

APs in an adjacent location

112
Q

skeletal m. are stimulated by…

A
  • motor neurons of the somatic nervous system

- axons of these neurons travel in nerves in nerves to muscle cells (branch profusely as they enter muscles)

113
Q

each axonal branch forms a…

A

neuromuscular junction with a SINGLE muscle fiber

114
Q

skeletal muscles are…

A

effector organs

115
Q

Neuromuscular Junction: presynaptic terminals

A

-axonal endings

116
Q

presynaptic terminals are located in an…

A

invagination of the sacrolemma (space between is the synaptic cleft)

117
Q

synaptic vesicles contain….

A

ACh

118
Q

Axons carry…

A

APs

119
Q

Neuromuscular Junction: Motor end plate

A
  • specific part of the sacrolemma in the area of synapse

- contains ACh receptors

120
Q

Neurotrasmitter = ?

A

ACh

121
Q

Excitation-contraction coupling

A

mechanism by which an AP in the sacrolemma causes the contraction of a muscle fiber

122
Q

IOT contract, a skeletal m must:

A
  1. be stimulated by a nerve ending
  2. propagate an electrical current, or AP, along its sarcolemma
  3. have a rise in intracellular Ca2+ levels
123
Q

what is Excitation-contraction coupling?

A

linking the electrical signal to the contraction

124
Q

the sarcolemma extends into…

A

the interior of the muscle via tube like invaginations called transverse tubules

125
Q

transverse tubules

A
  • allows tunnel for APs to depolarize

- wrap around the sarcomeres of the myofibrils in the A-band I-band junction

126
Q

Sarcoplasmic Reticulum (SR)

A
  • looks like webbing
  • an elaborate, highly specialized SER
  • runs longitudinally
127
Q

the SR surrounds…

A

each myofibril

128
Q

SR helps regulate…

A

intracellular Ca2+ levels; actively transports Ca2+ into its lumen for a 2000x greater Ca2+ concentration than in the sarcolemma

129
Q

The SR has a huge concentration of…

A

calcium ions

130
Q

Excitation-Contraction Coupling: Step 1

A
  • An AP (produced at presynaptic terminal) is propagated along the sarcolemma of the skeletal m.
  • this wave of depolarization also spreads along the membrane of the T-tubules
131
Q

Excitation-Contraction Coupling: Step 2

A
  • depolarization of the t-tubule causes gated Ca2+ channels in the SR to open, resulting in an increase in the permeability of the SR to Ca2+, especially in the terminal cisternae
  • Ca2+ then diffuse from the SR into the sacroplasm
132
Q

Excitation-Contraction Coupling: Step 3

A

Ca2+ released from the SR to bind to troponin molecules
-the troponin molecules that are bound to G actin are released, causing tropomyosin to move, exposing the active sites on G actin

133
Q

Excitation-Contraction Coupling: Step 4

A

once active sites on G actin are exposed, the heads of myosin bind to them to form cross-bridges

134
Q

what results in contraction?

A

the movement of the cross bridges

135
Q

what is required for cross bridge movement?

A

the energy from one ATP molecule

136
Q

During cross-bridge movement, the myosin head…

A

is in the cocked position and ADP/phosphate are attached to the head (from ATP breakdown)

137
Q

energy from the breakdown of ATP is stored in…

A

the myosin head

138
Q

Cross Bridge Movement: When Ca2+ binds to troponin…

A

tropomyosin moves to expose the active sites on the actin

139
Q

Cross Bridge Movement: Myosin heads bind to the…

A

active sites on the actin myofilaments and a cross-bridge is formed and the phosphate is released from the myosin head

140
Q

energy stored in the myosin head is used to…

A

move the head at the hinge region of the molecule

141
Q

powerstroke

A

movement at the hinge region

142
Q

movement of the head causes…

A

actin to slide past the myosin

143
Q

ADP is released from…

A

the myosin head

144
Q

Cross Bridge Movement: ATP binds to…

A

the myosin head and causes cross-bridge release

145
Q

Cross Bridge Movement: The myosin head separates from…

A

actin

146
Q

what is required to separate cross-bridges?

A

ATP

147
Q

Cross Bridge Movement: ATP is broken down by…

A

myosin ATPpase to ADP and phosphate which remain attached to the myosin head (hydrolysis reaction)

148
Q

when does the myosin head return to the cocked position?

A

after the recovery stroke

149
Q

If Ca2+ are still bound to troponin..

A

cross-bridge formation and movement are repeated

150
Q

how many times does cross bridge cycling occur?

A

many times

151
Q

Cross Bridge Movement: Muscular Relaxation

A

occurs as a result of active transport of Ca2_ back into the SR

152
Q

as the Ca2+ concentratoin decreases in the sarcoplasm…

A

Ca2+ diffuse away from the troponin

153
Q

Cross Bridge Movement: Tropomyosin move to…

A

cover the active sites on the actin molecules, preventing further cross-bridge formation

154
Q

T/F: Both relaxation and contraction do not require ATP

A

FALSE, relaxation does not occur without cross-bridge release, which requires ATP to bind to myosin heads

155
Q

muscle twitch

A

hypothetical contraction of a SINGLE muscle fiber in response to a SINGLE AP

156
Q

Phases of a muscle twitch

A

lag
contraction
relaxation

157
Q

Lag (latent) phase

A

time between application of the stimulus to the motor neuron and the muscle contraction

158
Q

contraction phase

A
  • contraction occurs

- formation/ cycling of cross-bridge

159
Q

relaxation phase

A

relaxation occurs

160
Q

muscle fibers are organized into..

A

motor units within a given muscle

161
Q

a motor unit consists of…

A

a single motor neuron and all of the muscle fibers that it innervates

162
Q

strength of contraction may vary from…

A

weak to strong based on the requirements

163
Q

Force of contraction may be increased in what 2 ways:

A

multiple motor unit summation

multiple wave summation

164
Q

multiple motor unit summation

A

increased strength of stimulus increases the # of muscle fibers that respond to contract

165
Q

multiple wave summation

A

increased frequency of stimuli increases the force of contraction as the muscle doesn’t have time to fully relax

166
Q

stronger than threshold stimulus

A
  • AP

- contraction equal to that with threshold stimulus

167
Q

whole muscles respond to stimuli in…

A

a graded manner

168
Q

whole muscles are composed of..

A

many motor units

169
Q

whole muscles will contract with…

A

small or large force depending on the # of motor units stimulated

170
Q

As more motor units are stimulated…

A

the force of the contraction increases

171
Q

do muscles always contain the same # of muscle fibers?

A

no, smaller muscle with delicate movements have few muscle fibers

172
Q

strength contraction of a whole muscle depends on…

A

recruitment of motor units

173
Q

maximal stimulus

A

all motor units respond

174
Q

stronger stimulus means recruitment of…

A

more motor units

175
Q

multiple wave summation: Stimulus frequency

A

-# of times a motor neuron is stimulated per second

176
Q

when stimulus frequency is low…

A

there is time for the complete relaxation of the muscle between twitches

177
Q

when stimulus frequency is high…

A

there isnt enough time for muscle fibers to relax completely

178
Q

Is relaxation required before a 2nd AP can stimulate a second contraction?

A

No, relaxation is NOT required

179
Q

incomplete tetanus

A

muscle fibers relax partially between the contractions

180
Q

complete tetanus

A

APs produced so rapidly that no relaxation occurs between them

181
Q

multiple wave summation: muscle tension increases as…

A

stimulation frequency increases

182
Q

cause of tetanus

A

force of contraction of a whole muscle increases with frequency of stimulation because of an increasing concentration of Ca2+ around the myofibrils

183
Q

Treppe

A

increase in the force of the contraction during the first few contractions of a rested muscle
ONLY in rested muscle

184
Q

isometric contractions

A

increase in muscle tension but no change in muscle length

185
Q

examples of isometric contractions

A

plank, walls sit, flexed arm hang

186
Q

isotonic contractions

A
  • change in muscle length, but no change in muscle tension

- has two types: concentric, eccentric

187
Q

examples of isotonic contractions

A

bicep curl
push up
back squat

188
Q

muscle tone

A

constant tension produced by muscles of the body over long periods of time

189
Q

concentric contractions

A

isotonic contractions in which muscle tension increases and the muscle shortens

190
Q

eccentric contractions

A

isotonic contractions in which tension is maintained as the muscle lengthens

191
Q

the # of cross-bridges that can form determines the…

A

force of contraction

192
Q

of cross-bridges that can form is dependent on…

A

muscle length

193
Q

muscle length determines…

A

sarcomere length, which determines the amount of overlap between actin and myosin

194
Q

maximal cross-bridge formation results in…

A

maximal contraction

195
Q

stretched muscle

A

not enough cross bridge formation

196
Q

crumpled muscle

A

cross bridges cant contract

197
Q

optimal length

A

ideal starting position for contraction because there is room to shorten and form cross bridges

198
Q

fatigue

A

decreased ability to do work/reduced effiiciency of performance that normally follow a period of activity

199
Q

psychological fatigue

A
  • most common

- muscles capable fo functioning but the person perceives that additional muscular work is not possible

200
Q

muscular fatigue

A
  • results from ATP depletion
  • without adequate ATP levels, cross bridges and ion channels do not function properly
  • muscle tension declines
201
Q

physiologic contracture

A

the inability of muscles to contract or relax due to extreme muscular fatigue

202
Q

rigor mortis

A

rigid muscles after death that result from inadequate amounts of ATP (cross bridges cannot release)

203
Q

immediate energy sources

A
  • creatine phosphate (PCr)

- ATP from this source provides energy for 0-10 seconds

204
Q

ATP is synthesized when ADP reacts with…

A

PCr to form both creatine and ATP

205
Q

Anaerobic Energy Sources

A
  • anaerobic glycolysis
  • ATP synthesized provides energy for 1-3 minutes
  • produces ATP less efficiently but more rapidly than aerobic respiration
206
Q

aerobic energy sources

A
  • aerobic glycolysis
  • requires oxygen
  • produces energy for muscular contraction under resting conditions or endurance exercises
  • 3 mins -hours
207
Q

muscle fiber types

A

SO
FG
FOG

208
Q

muscle fibers are what kind of fiber types?

A

Skeletal muscle fibers

209
Q

why can SO fibers contract more slowly than FG and FOG?

A

because they contain myosin ATPases that breakdown from ATP slower than FG and FOG fibers

210
Q

SO fibers

A
  • daily living, walking
  • fatigue resistant
  • use aerobic energy sources
  • high mitochondrial density
  • highly vascularized
  • contain myoglobin
211
Q

FG fibers

A
  • highly fatiguable
  • use anaerobic respiration
  • high glycogen concentration
  • contract with a lot of force
212
Q

FOG fibers

A
  • fatigue resistance intermediate between SO and FG fibers
  • low mitochondrial density
  • use aerobic and anaerobic respiration
213
Q

How do we determine fiber type?

A

-invasive muscle biopsy

214
Q

SO fibers maintain…

A

posture and are involved with prolonged exercise

-long distance runners generally have a higher % of SO fibers

215
Q

FG fibers produce…

A

powerful contractions of short duration

-sprinters usually have a higher % of FG fibers

216
Q

FOG fibers

A

support moderate intensity endurance exercise

217
Q

hypertrophy

A
  • increase in the size of muscle

- due to an increase in the size of muscle fibers or an increase in the number of muscle fibers

218
Q

Muscular Hypertrophy: Aerobic Exercise

A
  • increases the vascularity of muscle

- greater hypertrophy of slow twitch than fast twitch

219
Q

Muscular Hypertrophy: intense anaerobic exercise

A

greater hypertrophy of fast twitch (FG/FOG) than SO

220
Q

Atrophy

A
  • decrease in size of muscle
  • due to decrease in the size of muscle fibers or a loss of muscle fibers
  • could be from inactivity, bed rest, aging (sarcopena)
221
Q

Effects of Aging on Skeletal m: By 80 years of age…

A

-50% of the muscle mass is gone due to a loss of muscle fibers

222
Q

Effects of Aging on Skeletal m: Fast-twitch muscle fibers decrease in…

A

number more rapidly than SO fibers

223
Q

Effects of Aging on Skeletal m can be dramatically slowed if…

A

physical activity is maintained, particularly strength training activities

A&P Lecture Exam 2 (8 decks)

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