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
2
Q
Muscular System: Functions: Bodily movement
A
contraction of skeletal m. is responsible for overt movements of the body
3
Q
Muscular System: Functions: maintenance of posture
A
skeletal m. constantly maintains tone and keeps us up right
4
Q
Muscular System: Functions: production of body heat
A
when skeletal m. contract, heat is released as a byproduct
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
6
Q
Muscular System: Functions: respiration
A
skeletal m. of the thorax responsible for the movements necessary for respiration
7
Q
Muscular System: Functions: communication
A
skeletal m. are involved in all aspects of communication (writing, speaking, facial expression)
8
Q
Muscular System: Functions: constriction of organs and vessels
A
contraction of smooth m. within the walls of organs and vessels causes constriction
9
Q
4 functional characteristics of muscle
A
contractility
extensibility
excitability
elasticity
10
Q
Functional Characteristics of Muscle: Contractility
A
-the ability to shorten forcibly
11
Q
muscular contraction is an active process in which…
A
muscle cells generate the forces causing muscle to shorten
12
Q
muscular relaxation is a passive process and results….
A
from forces outside of the muscle itself
13
Q
Functional Characteristics of Muscle: Excitability
A
the ability to receive and respond to stimuli
14
Q
muscles normally contract as a result of…
A
stimulation by nerves
15
Q
Functional Characteristics of Muscle: Extensibility
A
-the ability to be stretched or extended
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
17
Q
Functional Characteristics of Muscle: Elasticity
A
the ability to recoil and resume original resting length after being stretched
18
Q
Skeletal, cardiac and smooth m. differ in terms of their:
A
structure
location
function
means of activation
19
Q
Each muscle is a discrete organ composed of…
A
muscle tissue, connective tissue, blood vessels, nerve fibers
20
Q
Skeletal m. is responsible for…
A
most body movements (locomotion, facial expression, posture, respiratory movements)
21
Q
Skeletal muscle stabilizes…
A
joints and generates heat
22
Q
skeletal muscle is under what kind of control?
A
voluntary
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)
24
Q
smooth m. contracts…
A
involuntarily (under unconscious control)
25
smooth m. regulates...
flow through blood vessels
26
what type of muscle helps maintain blood pressure?
smooth
27
what type of muscle squeezes or propels substances through organs?
smooth
28
cardiac m. contractions provide the force to...
move blood through the vascular system
29
Muscle tissue: Cardiac: Autorhytmic
- contracts spontaneously at somewhat regular intervals
| - nervous or hormonal stimulation isn't always required for contraction
30
function of smooth m:
```
moving food through digestive tract
emptying urinary bladder
regulating blood vessel diameter
changing pupil size
contracting many gland ducts
moving hair
```
31
function of cardiac m:
pumping blood
| contractions provide force to propel blood through blood vessels
32
Nucleus # in skeletal m:
multiple nuclei, peripherally located
33
Nucleus # in smooth m:
single, centrally located
34
Nucleus # in cardiac m:
single, centrally located
35
T/F: Skeletal muscle is striated
True
36
T/F: cardiac muscle is not striated
false, it is striated
37
Skeletal m is composed of...
skeletal muscle cells fibers called myocytes
38
Myocytes
- elongated cells
- multiple nuclei located of the fiber near the PM
- individual fibers can extend from one end of the muscle to the other
39
striations in skeletal m are due to...
the arrangement of actin and myosin myofilaments
40
skeletal muscle contracts...
rapidly, but tires easily
41
3 types of muscular fascia:
epimysium
perimysium
endomysium
42
muscular fascia
sheets of CT that separate and compartmentalize muscles
43
epimysium
- Most superficial
| - dense collagenous CT that surrounds the ENTIRE muscle
44
perimysium
fibrous CT that surrounds groups muscle fibers known as fascicles
45
endomysium
fine sheath of CT composed of reticular fibers that surrounds each individual muscle fiber
46
CT connects muscles to...
other structures
47
CT provides a pathway for...
nerves and blood vessels to reach individual muscle cells/fibers
48
sacrolemma
PM of a muscle cell
49
sacroplasm
cytoplasm of a muscle cell
50
myofibrils
densely packed, rod-like contractile elements that extend from one end of the muscle fiber to the other
51
what makes up most of the muscle volume?
myofibrils
52
myobfibrils are composed of...
actin and myosin
53
Actin and Myosin form...
highly ordered units called sarcomeres
54
sarcomeres are joined...
end to end to form myofibrils
55
Myofilaments: Actin: Thin Myofilament
consist of 2 helical polymer strands of F actin, tropomyosin and troponin
56
Myofilaments: Actin: G (globular) actin
contains the active sites to which myosin heads attach during contraction
57
Myofilaments: Actin: Troponin
molecules are attached at the specific intervals along the actin myofilaments and have Ca2+ binding sites
58
troponin also attaches to...
tropomyosin
59
Myofilaments: Actin: Tropomyosin
-molecules located along the groove between the twisted strands of F actin
60
Tropomyosin covers the active sites on...
G actin when Ca2+ is not bound to troponin
61
Myofilaments: Myosin
-thick myofilament, composed of myosin molecules
62
A crossbridge is formed when...
a myosin head binds to the active sites on G actin
63
Myosin Head
contains ATPpase which breaks down ATP
64
Hinge Region
enables the head to move
65
Rods
-attach to each other and are arranged so that the heads of the myosin molecules are located at each end of the myofilament
66
Sarcomere
smallest individual contractile unit within a muscle
67
Sarcomeres are bound on...
either end by Z disks; attach to actin myofilaments
68
how many actin myofilaments surround each myosin myofilament?
6
69
why do myofibrils appear to be striated?
Due to the organization of actin and myosin myofilaments within sarcomeres
70
A Band
-extends the length of the myosin myofilaments within a sarcomere
71
what gives A bands their dark appearance?
the overlapping of actin/myosin at both ends of the band
72
Z disk
coin shaped sheet of proteins (connectins) that anchors actin and connects sarcomeres to one another
73
H zone
- center of each A band where the myofilaments DO NOT overlap
- only myosin present
74
M line
- 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)
75
why does the M line appear darker?
due to the presence of the protein desmin
76
I band
only contains actin myofilament
77
during contraction, actin...
slides past myosin to shorten the sarcomeres
78
T/F: Actin and myosin change length during contraction
FALSE, they do not change length, only position
79
during relaxation, sarcomeres lengthen because...
of an external force, like contraction of antagonistic muscles (muscles that produce the opposite effect)
80
the nervous system stimulates muscles to contract through...
electrical signals called action potentials
81
Resting membrane potential:
- charge difference across the PM
| - must exist for APs to occur
82
The inside of the RMP is...
negative, compared to the outside in a resting cell
83
An action potential is a reversal of the...
RMP so that the inside of the PM becomes positive (depolarizes)
84
Ion channels assist with...
production/spread of action potentials
85
when a cell is stimulated, the permeability characteristics of the PM...
- 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
86
2 types of gated ion channels help produce APs:
voltage gated
| ligand gated
87
Ligand
molecule that binds to a receptor located in the PM
88
Ligand gated channels: receptor
protein or glycoprotein with a receptor site to which a ligand can bind
89
Ligand gated channels: gates open in response to...
a ligand binding to a receptor that is part of the ion channel
90
Ligand gated channels: Step 1 of Gates opening:
motor neurons that supply skeletal m. release the neurotransmitter acetylcholine (ACh)
91
Ligand gated channels: Step 2 of Gates opening:
ACh binds to ligand gated Na+ channels in the membranes of muscle fibers
92
Ligand gated channels: Step 3 of Gates opening:
Na+ channels open, allowing Na+ to enter the cell
93
gated channels open and close in response to...
small voltage changes across the PM
94
Voltage-Gated Channels: Process of Gates opening
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
what are important voltage-gated ion channels in muscles?
Na+
K+
Ca2+
96
In RMP, voltage-gated Na+ channels and voltage-gated K+ channels are..
closed
97
the outside of the PM is...
positively charged compared to the inside
98
Depolarization results from...
an increase in the permeability of the PM to Na+
99
if depolarization reaches threshold..
an AP is produced
100
APs result from...
the opening of many Na+ channels
101
the inward movement of Na+...
makes the inside of the membrane more positive
102
re-polarization occurs when...
Na+ channels close and K+ channels open briefly
103
re-polarization is caused when...
Na+ movement into the cell stops and K+ movement out of the cell increases
104
APs occur in what kind of fashion?
all or none
105
sub-threshold stimulus
- produces no AP
| - no contraction
106
threshold stimulus
- a stimulus at or above threshold will produce an AP
- depolarization
- contraction
107
once an AP begins...
all of the ion channels changes proceed without stopping
108
APs occur in...
a very small area of the PM
109
APs do not affect...
the entire PM at once
110
T/F: APs can't propagate across PM
False, they can propagate/travel across PMs
111
APs can stimulate the production of...
APs in an adjacent location
112
skeletal m. are stimulated by...
- 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
each axonal branch forms a...
neuromuscular junction with a SINGLE muscle fiber
114
skeletal muscles are...
effector organs
115
Neuromuscular Junction: presynaptic terminals
-axonal endings
116
presynaptic terminals are located in an...
invagination of the sacrolemma (space between is the synaptic cleft)
117
synaptic vesicles contain....
ACh
118
Axons carry...
APs
119
Neuromuscular Junction: Motor end plate
- specific part of the sacrolemma in the area of synapse
| - contains ACh receptors
120
Neurotrasmitter = ?
ACh
121
Excitation-contraction coupling
mechanism by which an AP in the sacrolemma causes the contraction of a muscle fiber
122
IOT contract, a skeletal m must:
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
what is Excitation-contraction coupling?
linking the electrical signal to the contraction
124
the sarcolemma extends into...
the interior of the muscle via tube like invaginations called transverse tubules
125
transverse tubules
- allows tunnel for APs to depolarize
| - wrap around the sarcomeres of the myofibrils in the A-band I-band junction
126
Sarcoplasmic Reticulum (SR)
- looks like webbing
- an elaborate, highly specialized SER
- runs longitudinally
127
the SR surrounds...
each myofibril
128
SR helps regulate...
intracellular Ca2+ levels; actively transports Ca2+ into its lumen for a 2000x greater Ca2+ concentration than in the sarcolemma
129
The SR has a huge concentration of...
calcium ions
130
Excitation-Contraction Coupling: Step 1
- 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
Excitation-Contraction Coupling: Step 2
- 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
Excitation-Contraction Coupling: Step 3
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
Excitation-Contraction Coupling: Step 4
once active sites on G actin are exposed, the heads of myosin bind to them to form cross-bridges
134
what results in contraction?
the movement of the cross bridges
135
what is required for cross bridge movement?
the energy from one ATP molecule
136
During cross-bridge movement, the myosin head...
is in the cocked position and ADP/phosphate are attached to the head (from ATP breakdown)
137
energy from the breakdown of ATP is stored in...
the myosin head
138
Cross Bridge Movement: When Ca2+ binds to troponin...
tropomyosin moves to expose the active sites on the actin
139
Cross Bridge Movement: Myosin heads bind to the...
active sites on the actin myofilaments and a cross-bridge is formed and the phosphate is released from the myosin head
140
energy stored in the myosin head is used to...
move the head at the hinge region of the molecule
141
powerstroke
movement at the hinge region
142
movement of the head causes...
actin to slide past the myosin
143
ADP is released from...
the myosin head
144
Cross Bridge Movement: ATP binds to...
the myosin head and causes cross-bridge release
145
Cross Bridge Movement: The myosin head separates from...
actin
146
what is required to separate cross-bridges?
ATP
147
Cross Bridge Movement: ATP is broken down by...
myosin ATPpase to ADP and phosphate which remain attached to the myosin head (hydrolysis reaction)
148
when does the myosin head return to the cocked position?
after the recovery stroke
149
If Ca2+ are still bound to troponin..
cross-bridge formation and movement are repeated
150
how many times does cross bridge cycling occur?
many times
151
Cross Bridge Movement: Muscular Relaxation
occurs as a result of active transport of Ca2_ back into the SR
152
as the Ca2+ concentratoin decreases in the sarcoplasm...
Ca2+ diffuse away from the troponin
153
Cross Bridge Movement: Tropomyosin move to...
cover the active sites on the actin molecules, preventing further cross-bridge formation
154
T/F: Both relaxation and contraction do not require ATP
FALSE, relaxation does not occur without cross-bridge release, which requires ATP to bind to myosin heads
155
muscle twitch
hypothetical contraction of a SINGLE muscle fiber in response to a SINGLE AP
156
Phases of a muscle twitch
lag
contraction
relaxation
157
Lag (latent) phase
time between application of the stimulus to the motor neuron and the muscle contraction
158
contraction phase
- contraction occurs
| - formation/ cycling of cross-bridge
159
relaxation phase
relaxation occurs
160
muscle fibers are organized into..
motor units within a given muscle
161
a motor unit consists of...
a single motor neuron and all of the muscle fibers that it innervates
162
strength of contraction may vary from...
weak to strong based on the requirements
163
Force of contraction may be increased in what 2 ways:
multiple motor unit summation
| multiple wave summation
164
multiple motor unit summation
increased strength of stimulus increases the # of muscle fibers that respond to contract
165
multiple wave summation
increased frequency of stimuli increases the force of contraction as the muscle doesn't have time to fully relax
166
stronger than threshold stimulus
- AP
| - contraction equal to that with threshold stimulus
167
whole muscles respond to stimuli in...
a graded manner
168
whole muscles are composed of..
many motor units
169
whole muscles will contract with...
small or large force depending on the # of motor units stimulated
170
As more motor units are stimulated...
the force of the contraction increases
171
do muscles always contain the same # of muscle fibers?
no, smaller muscle with delicate movements have few muscle fibers
172
strength contraction of a whole muscle depends on...
recruitment of motor units
173
maximal stimulus
all motor units respond
174
stronger stimulus means recruitment of...
more motor units
175
multiple wave summation: Stimulus frequency
-# of times a motor neuron is stimulated per second
176
when stimulus frequency is low...
there is time for the complete relaxation of the muscle between twitches
177
when stimulus frequency is high...
there isnt enough time for muscle fibers to relax completely
178
Is relaxation required before a 2nd AP can stimulate a second contraction?
No, relaxation is NOT required
179
incomplete tetanus
muscle fibers relax partially between the contractions
180
complete tetanus
APs produced so rapidly that no relaxation occurs between them
181
multiple wave summation: muscle tension increases as...
stimulation frequency increases
182
cause of tetanus
force of contraction of a whole muscle increases with frequency of stimulation because of an increasing concentration of Ca2+ around the myofibrils
183
Treppe
increase in the force of the contraction during the first few contractions of a rested muscle
ONLY in rested muscle
184
isometric contractions
increase in muscle tension but no change in muscle length
185
examples of isometric contractions
plank, walls sit, flexed arm hang
186
isotonic contractions
- change in muscle length, but no change in muscle tension
| - has two types: concentric, eccentric
187
examples of isotonic contractions
bicep curl
push up
back squat
188
muscle tone
constant tension produced by muscles of the body over long periods of time
189
concentric contractions
isotonic contractions in which muscle tension increases and the muscle shortens
190
eccentric contractions
isotonic contractions in which tension is maintained as the muscle lengthens
191
the # of cross-bridges that can form determines the...
force of contraction
192
of cross-bridges that can form is dependent on...
muscle length
193
muscle length determines...
sarcomere length, which determines the amount of overlap between actin and myosin
194
maximal cross-bridge formation results in...
maximal contraction
195
stretched muscle
not enough cross bridge formation
196
crumpled muscle
cross bridges cant contract
197
optimal length
ideal starting position for contraction because there is room to shorten and form cross bridges
198
fatigue
decreased ability to do work/reduced effiiciency of performance that normally follow a period of activity
199
psychological fatigue
- most common
| - muscles capable fo functioning but the person perceives that additional muscular work is not possible
200
muscular fatigue
- results from ATP depletion
- without adequate ATP levels, cross bridges and ion channels do not function properly
- muscle tension declines
201
physiologic contracture
the inability of muscles to contract or relax due to extreme muscular fatigue
202
rigor mortis
rigid muscles after death that result from inadequate amounts of ATP (cross bridges cannot release)
203
immediate energy sources
- creatine phosphate (PCr)
| - ATP from this source provides energy for 0-10 seconds
204
ATP is synthesized when ADP reacts with...
PCr to form both creatine and ATP
205
Anaerobic Energy Sources
- anaerobic glycolysis
- ATP synthesized provides energy for 1-3 minutes
- produces ATP less efficiently but more rapidly than aerobic respiration
206
aerobic energy sources
- aerobic glycolysis
- requires oxygen
- produces energy for muscular contraction under resting conditions or endurance exercises
- 3 mins -hours
207
muscle fiber types
SO
FG
FOG
208
muscle fibers are what kind of fiber types?
Skeletal muscle fibers
209
why can SO fibers contract more slowly than FG and FOG?
because they contain myosin ATPases that breakdown from ATP slower than FG and FOG fibers
210
SO fibers
- daily living, walking
- fatigue resistant
- use aerobic energy sources
- high mitochondrial density
- highly vascularized
- contain myoglobin
211
FG fibers
- highly fatiguable
- use anaerobic respiration
- high glycogen concentration
- contract with a lot of force
212
FOG fibers
- fatigue resistance intermediate between SO and FG fibers
- low mitochondrial density
- use aerobic and anaerobic respiration
213
How do we determine fiber type?
-invasive muscle biopsy
214
SO fibers maintain...
posture and are involved with prolonged exercise
| -long distance runners generally have a higher % of SO fibers
215
FG fibers produce...
powerful contractions of short duration
| -sprinters usually have a higher % of FG fibers
216
FOG fibers
support moderate intensity endurance exercise
217
hypertrophy
- 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
Muscular Hypertrophy: Aerobic Exercise
- increases the vascularity of muscle
| - greater hypertrophy of slow twitch than fast twitch
219
Muscular Hypertrophy: intense anaerobic exercise
greater hypertrophy of fast twitch (FG/FOG) than SO
220
Atrophy
- 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
Effects of Aging on Skeletal m: By 80 years of age...
-50% of the muscle mass is gone due to a loss of muscle fibers
222
Effects of Aging on Skeletal m: Fast-twitch muscle fibers decrease in...
number more rapidly than SO fibers
223
Effects of Aging on Skeletal m can be dramatically slowed if...
physical activity is maintained, particularly strength training activities
