Chapter 10 Flashcards
(128 cards)
1
Q
Functions of Muscle Tissue (4)
A
1) excitable/irratable →
2) **contractile **→ can shorten in length
3) **extensible **→ extend/stretch
4) **elastic **→ can return to original shape
2
Q
Other Functions of Muscle Tissue (5)
A
1) create motion
2) stabilize body positions & maintain posture
3) store substances within body using sphincters
4) move substances by contractions
5) generate **heat **through **thermogenesis **
3
Q
(3) types of muscular tissue
A
1) Skeletal
2) Cardiac
3) Visceral
4
Q
1) Skeletal muscle
- location
- function
- appearance
- control
A
- skeleton
- movement, heat posture
- striated, multi-nucleated (eccentric)
- fibers parallel
- voluntary
5
Q
2) Cardiac muscle
- location
- function
- appearance
- control
A
- heart
- pump blood continuously
- striated, 1 central nucleus
- involuntary
6
Q
3) **Visceral **muscle
- location
- function
- appearance
- control
A
- GI tract, uterus, eye, blood vessels
- peristalsis, BP, pupil size, erects hairs
- no striations, 1 central nucleus
- involuntary
7
Q
Organization of Muscle Tissue
A
epimysium, perimysium & endomysium
→ all continuous with CT that forms tendons & **ligaments **
**→ **extend from **fascia **
8
Q
Fascia
- function
A
dense sheet/broad band of irreg CT that lines body wall/limbs & supports/surrounds muscles/other organs
- holds muscles of similar functions together
- (connects muscles to other muscles to form groups)
9
Q
Epimysium
A
outermost layer of **dense irregular CT **
- encircles entire muscle
10
Q
Perimysium
A
layer of dense irregular CT surrounding groups of 10-100 muscle fibers seperating them in bundles (fascicles)
11
Q
Endomysium
A
mostly reticular fibers
- seperates individual muscle fibers
12
Q
What seperates muscle from skin?
A
Subcutaneous layer
13
Q
Tendon
A
ropelike structure that extends beyond muscle fibers to attach muscle to periosteum of bone
14
Q
Sarcolemma
A
plasma membrane of muscle cell beneath endomysium
- encloses sarcoplasm & myofibrils (striated)
15
Q
Sarcoplasm
A
**cytoplasm **of muscle fiber within sarcolemma
16
Q
Myofibrils
A
striated contractile organelles of skeletal muscle
(in the sarcoplasm)
17
Q
Transverse (T) Tubules
A
tiny invaginations of sarcolemma filled with interstitial fluid *(open to outside of fiber) *
- tunnel in from surface toward center of each muscle fiber
18
Q
Triad
A
T tubule + 2 terminal cisternae
19
Q
Sarcoplasmic Reticulum (SR)
A
fluid-filled system of membranous sacs
- encircles each myofibril
- has **terminal cisternae **
- stores Ca2+ in relaxes muscle fiber
20
Q
Terminal Cisternae
A
dilated end sacs of SR that butt against T tubule from both sides
21
Q
What triggers muscle contraction?
A
Release of Ca2+ from **terminal cisternae **of **SR **
22
Q
Sarcomere
A
basic functional units of myofibrils
- arrangement of thick & thin filaments sandwiched between 2 Z discs
23
Q
Myofibrils
- composed of?
A
filaments
- thick filaments (myosin)
- thin filaments (actin)
24
Q
Z disc
A
*narrow, plate-shaped region of dense protein material *
- seperates one sarcomere from the next
25
Sarcomere extends from?
one **Z disc** to the next **Z disc**
26
Extent of overlap of thick & thin filaments depends on?
whether muscle is **contracted, relaxed** or **stretched**
27
A band
**dark middle region**
- extends length of **thick** filaments
(includes part of **overlap** with thin filaments)
28
I band
lighter, less dense area
- contains **rest of thin filaments**
but **NO** thick filaments
- Z disc passes through center
29
Zone of overlap
Toward each **end of A band **
- where **thin & thick** filaments lie **side by side**
30
H Zone
**center of A band** containing **ONLY thick** filaments
31
M line
**center** of **H zone **
marks **middle of sarcomere**
formed by **supporting proteins** that hold thick filaments **together **
32
Z line is really __ \_\_ when considered in 3D
Z disc
33
**Muscle Proteins**
**Myofibrils **built from **(3) groups** of proteins
- **functions**?
1) **Contractile **→ generate force during contraction
2) **Regulatory**→ help switch contraction process on/off
3) **Structural**→ keeps thick & thin filaments in *proper alignment* & *links* myofibrils to sarcolemma & ECM
34
1) Contractile Proteins
Actin
Mysoon
35
2) Regulatory Proteins
troponin
tropomyosin
36
3) Structural Proteins
Titan
Dystrophin
Myomesin
37
**Myosin**
- parts
main component of **thick **filaments
## Footnote
-functions as **motor** protein in all 3 types of muscle tissue
**myosin tail → **twisted gold club handles
- **point toward M line** in center of sarcomere
- form **shaft **
**myosin head **→ 2 projections of each myosin molecule
38
Actin
main component of **thin filaments **(anchored to Z discs)
- bead of pearls twisted into helix
**myosin-binding site →** where myosin head attaches
39
Tropomyosin
strands of **tropomyosin **cover **myosin-binding site **on actin
- held together by **troponin **molecules
40
Troponin
hold **tropomyosin strands **in place
41
When Ca2+ binds to **troponin?**
**troponin **undergoes change in shape
→ moves **tropomyosin **away from **myosin-binding sites **on actin
- muscle contraction begnis as myosin binds to actin
42
**Structural** Proteins → functions? (4)
contribute to **alignment, stability, elasticity & extensibility **of myofibrils
43
Titin
**3rd most plentiful** protein in muscle (after actin & myosin)
- **extends** from **Z disc to M line** & accounts for much of the **elasticity** of myofibrils
44
Dystrophin
**links** filaments to **integral membrane proteins**
reinforces **sarcolemma & **transmits tension from **sarcomeres **to **tendons**
45
Myomesin
binds to **titin** & **links** adjacent **thick filaments**
- forms **M line **
46
Troponin-Tropomyosin Complex
can slide back & forth **depending on presence of Ca2+**
- slides down into "gutters" of actin molecules ot unblock **myosin-binding sites **on actin
47
**Levels** of **Organization **within Skeletal Muscle
skeletal muscle
fascicle
muscle fibers (cells)
myofibrils
filaments
48
Sliding-Filament Mechanism
muscle contraction occurs b/c myosin heads attach to & walk along thin filaments at both ends of sarcomere
- progressively pulling thin filaments towards M line
- thin filaments meet at center of sarcomere
49
What happens to each band/zone as muscle contracts?
**H Zone** → disappears (thin filaments overlap more & more)
**I Band → **shortens & disappears (Z discs come closer together)
**A Band →** does not shorten (extends length of thick filaments which does not shorten)
50
Contraction Cycle
repeating sequence of events that cause filaments to slide
51
Contraction Cycle
## Footnote
**at onset of contraction...**
**SR **releases **Ca2+** into **sarcoplasm**
→ bind to **troponin** → moves **tropomyosin** away from **myosin-binding sites** on actin
→ once binding sites are free - **contraction cycle **begins
52
Contraction Cycle
## Footnote
**- (4) steps **
1) **ATP hydrolysis**
2) **Attachment of myosin **to **actin **to form **cross-bridges**
3) **Power stroke**
4) **Detachment** of **myosin** from **actin**
53
1) ATP hydrolysis
myosin head include **ATP-binding site** & **ATPase**
**hydrolysis** rxn **reorients** & **energizes** myosin head
- ADP & P group **still attached** to myosin head
54
2) **Attachment** of **myosin **to** actin **to form c**ross-bridges**
**energized myosin head** attached to **myosin-binding site** on actin (**cross-bridge**)
- **releases** P group
55
3) Power stroke
after cross-bridges form, power stroke occurs
**during power stroke:**
- site on cross-bridge where ADP is bound **opens**
- cross-bridge rotates & **releases ADP**
- cross-bridge **generates force** as it **rotates towards center** of **sarcomere**, **sliding thin** filament **past thick** filament **toward M line**
56
4) Detachment of myosin from actin
at end of power stroke, **cross-bridges **remain **firmly attached** to actin **until it binds another ATP molecule **
- **as ATP binds** to **ATP-binding site** on **myosin head**, **myosin head detaches from actin**
57
Steps of Contraction Cycle (4)
- general concept
1) myosin heads **hydrolyze** ATP → become **reoriented** & **energized **
2) myosin heads **bind** to actin forming **cross-bridges**
3) mysoin cross-bridges **rotate toward center** of sarcomere (**power stroke**)
4) as myosin head **binds ATP,** cross-bridges **detach** from actin
58
Rigor Mortis
muscles remain in a state of rigidity because no ATP to bind to myosin head
- can't detach from actin
59
Length-Tension Relationship
indicates how **forcefulness** of muscle contraction **depends** on **length of sarcomeres** within muscle **before contraction begins**
## Footnote
*max tension occurs when zone of overlap b/w thick & thin extends from edge of H zone to 1 end of thick filament*
**understretched** - compressed thick filaments
**overstretched** - limited contact b/w actin & myosin
60
Neuromuscular Junction (NMJ)
**synapse** between **somatic motor neuron** & **skeletal muscle fiber **
61
Somatic motor neurons
neurons that stimulate muscle fibers to contract
62
Somatic Motor Neuron - **axon**
extends from brain/spinal cord to group of skeletal muscle fibers
63
Synapse
region where communication occurs between 2 neurons or between neuron & target cell
64
Synaptic cleft
small gap at most synapses that seperates the 2 cells
65
Neurotransmitter
**chemical** released that **transmit signals** across **synapse **
66
Axon Terminal
End of **motor neuron **at NMJ
67
Synaptic end bulbs
neural part of NMJ
## Footnote
* - axon terminal divides into cluster of synaptic end bulbs*
- expanded distal end of **axon terminal** that contains **synaptic vesicles **
68
Synaptic Vesicles
Hundreds of **membrane-enclosed sacs** in **synaptic end bulbs** that are **suspended** in the cytosol
- contain **Acetylcholine (ACh) **
69
Acetylcholine
**neurotransmitter** within **synaptic vesicles** that are **released** at NMJ
70
Motor End Plate
**muscle fiber part** of NMJ
region of **sarcolemma opposite** of **synaptic end bulbs**
**- **contain millions of **ACh receptors **(integral transmembrane proteins) - ***ligand-gated ion channels ***
* gated Na+ channels that respond to ACh
71
Nerve impulse (nerve AP) elicits muscle action potential in **(4) steps **
1) Release of ACH
2) Activation of ACh receptors
3) Production of muscle action potential
4) Termination of ACh activity
72
1) Release of ACh
(7)
nerve impulse arrives at **synaptic end bulbs**
stimulates **voltage‐gated channels** to **open **
b/c [Ca2+] is **higher** in ECF, Ca2+ flows **inward**
Ca2+ stimulates **synaptic vesicles** to undergo **exocytosis**
synaptic vesicles **fuse** with **motor neuron's PM**
**release ACh** into **synaptic cleft**
diffuses across synaptic cleft **b/w motor neuron & motor end plate.**
73
2) Activation of ACh receptors
2 ACh molecules bind to **receptor** on **motor end plate **→ ion channel **opens **
**Na+** flows inward
74
3) Production of Muscle AP
**inflow** of Na2+ → inside of muscle fiber **more (+) **
→**triggers** muscle AP
→**propogates** along **sarcolemma** into **T tubules**
→ causes **SR** to **release Ca2+** into **sarcoplasm**
muscle fiber **contracts**
75
4) Termination of ACh activity
ACh broken down by **acetylcholinesterase (AChE) **
- attached to collagen fibers in ECM of synaptic cleft
76
when APs in motor neuron stop...
ACh no longer released - broken down in synaptic cleft
**Ca2+ moves form sarcoplasm back into SR **
Ca2+ release channels in SR close
77
Where is NMJ?
usually near midpoint of skeletal muscle fiber
- muscle APs that arise at NMJ propogate towards ends of fiber
78
location of
1. Presynaptic membrane
2. postsynaptic membrane
1) on neuron
2) motor end plate on muscle cell
79
Conscious thought (to move muscle) causes?
**activation** of **motor neuron**
→ **release** of **neurotransmitter acetylcholine** (**ACh**) at NMJ
→ Enzyme **Acetylcholinesterase** breaks down ACh after short period of time
80
ACh Receptors
on **ligand-gated Na+ channels **on **motor end plate**
81
Muscle AP
- phases (3)
**Resting Potential** → (**-70 mV**)
ACh stimulus at motor end plate → **(-55 = Threshold)**
**Depolarizing **phase → (**+30**) - Na+ gates open → inflow
Action Potential
**Repolarizing **phase → back to (**-70**) - K+ gates open → outflow
(Na+ gates close)
**After-hyperpolarizing **phase → K+ channels take too long to close
82
**Generating AP** on **muscle** membrane involves **transfer of info from:**
**Electrical** signal (down **neuron**) → **chemical** signal (at **NMJ**) **→ electrical** signal (**depolarization** of sarcolemma)
83
**Excitation-Contraction Coupling**
(8) steps
1) AP at **axon terminal** of motor neuron **→ release** of **ACh**
2) **ACh **across synaptic cleft → **binds** to receptors in motor end plate → **triggers muscle AP**
3) AChE destroys ACh so only more ACh for AP
4) **muscle AP:** T Tubules → **opens Ca2+** release channels in SR → **Ca2**+ into **sarcoplasm**
5) Ca2+ binds to troponin
6) **Contraction Cycle**
7) Ca2+ release channels in SR **close **→ transport pumps restore low Ca2+ in sarcoplasm
8) **T-T complex** **back** into position
9) muscle **relaxes **
84
**Excitation-Contraction Coupling **
- general process (6)
1. **Thought** **process** going on in brain
2. **AP** arriving at **NMJ**
3. **Regeneration** of **AP** on **muscle membrane**
4. R**elease of Ca2+** from **SR**
5. **Sliding** of **thick** on **thin** filaments in **sarcomeres**
6. Generation of **muscle tension (work)**
85
Role Players in Excitation-Contraction Coupling
(16)
**brain **→**motor neuron **→ **ACh **→AChE
**ACh receptors** → **Na+/K+ channels ** → Na+ flow in → K+ flow out
**Regenerate AP** →T-Tubules → SR → Ca2+ release → T/T
ATP →myosin binding → filaments slide → muscles contract
86
Sources of Muscle Energy (4)
1) stored **ATP **→ 3 secs
2) Energy from **Creatine Phosphate →** 12 secs
3) **Anaerobic** Glucose Use (**Glycolysis**) → 30-40 s
4) Aerobic **ATP production** (**aerobic cellular resp**) → mins-hours
87
Creatine Phosphate
**relaxed muscle:**
## Footnote
Creatine + ATP → **Creatine Phosphate** + ADP
**contracting muscle:**
**Creatine Phosphate** + ADP → Creatine + ATP
ATP → **Energy for muscle contraction** + ADP
88
Anaerobic Glucose Use
**Anaerobic** Cellular Respiration = Anaerobic **Glycolysis**
**Muscle Glycogen** or **Blood Glucose**
Glucose → **2 ATP** + 2 Pyruvic Acid → 2 Lactic Acid (→ into blood)
89
Aerobic ATP production
**Aerobic Cellular Respiration **
**FAs** (from **adipose** cells)
**Pyruvic acid** (from **glycolysis**)
**Amino acids** (from **protein** breakdown)
**Oxygen** (from **hemoglobin** in **blood**/**myoglobin** in **muscle** fibers)
→ **36 ATP **+ CO2 + H2O + heat
90
Muscle Fatigue
**inability** of a muscle to **maintain force** of contraction **after prolonged activity**
91
Types of Fatigue (2)
1) Central
2) Peripheral
92
1) Central Fatigue
**before actual muscle fatigue begins **
- feeling tired & wanting to stop activity
- caused by changes in **CNS **
93
2) Peripheral Fatigue
**inability** to supply **sufficient energy** to contracting muscles to meet increased energy demands
94
**Sources** of Fatigue (6)
1. **Inadequate release** of **Ca2+** from ** SR**
2. Reduced **O2**
3. Reduced **Cr Ph**
4. Reduced **glycogen**
5. **Buildup** of **H+**
6. Problems with **Ach receptors** or **release**
95
Oxygen Debt (**Excess Post-Exercise Oxygen Consumption - EPOC) **
**amount of O2 repayment** required after exercise in skeletal muscle to:
**- replenish ATP, Creatine phosphate** & **myoglobin**
- convert **lactic acid** back into **purivate** (so it can be used for **CAC** to **replenish ATP**)
96
Motor Unit
composed of **motor neuron + all muscle cells it innervates **
97
Motor Units
1) high precision
2) low precision
1) **fewer **muscle fibers per neuron
- laryngeal & extraocular muscles (**2-20**)
2) **many **muscle fibers per neuron
- thigh muscles (**2,000-3000**)
98
Force of muscle contraction depends on (4)
**frequency of stimulation** - rate at which APs arrive at NMJ (# of impulses/second)
**size of motor units**
**# of motor units activated**
**type?**
99
Activities requiring extreme precision (subtle/rapid movements of eye) involve muscles with?
**small** motor units (**1-4** muscle fibers/neuron)
100
**All-or-none principle** of muscle contraction
(2)
When **individual muscle fiber** is stimulated to **depolarization** & AP propagates along its sarcolemma → **must contract to it’s full force**
Also, when **single motor unit** is **recruited** to contract, all muscle fibers in that motor unit **must all contract at the same time**
101
twitch contraction
the **brief contraction** of **all muscle fibers** in **motor unit** in **response** to **single AP** in **its motor neuron**
102
Latent period
**brief delay** as AP sweeps aover sarcolemma & Ca2+ released from SR (point of no return)
2 msec
- *delay between application of stimulus & beginning of contraction*
103
Contraction Period
**10-100 msec**
Ca2+ **binds** to troponin, myosin-binding site on actin exposed
**cross-bridges form**
peak tension develops in muscle fiber
104
Relaxation Period
**10-100 msec**
## Footnote
Ca2+ **actively transported **back in SR
myosin-binding sites **covered again** by tropomyosin
myosin heads **detach** from actin
tension in muscle **decreases **
105
Refractory Period
**5 msec** (skeletal) - **300 msec** (cardiac)
**temporary loss of excitability **
muscle fibers in motor unit won't respond to stimulus during this short time
106
Wave Summation
**phenomenon** in which **stimuli arriving at dif times** causes **larger contractions **
- **after refractory period** is over but **before skeletel muscle has relaxed **
(2nd contraction **stronger** than first)
107
**Unfused** (incomplete) Tetanus
skeletal muscle fiber is stimulated at rate of **20-30 times/sec **
**-** can only partially relax between stimuli
result is sustained but wavering contraction
108
Fused (Complete) Tetanus
when skeletal muscle fiber is stimulated at rate of **80-100 times/sec **
**- does not relax at all**
- result = **sustained contraction** in which individual twitches **can't be detected**
109
Applying **increased numbers **of APs to muscle fiber (or **fascicle**/**muscle**/muscle **group**) results in?
fusion of contractions (**tetanus**) & performance of **useful work**
110
Motor Unit Recruitment
process in which **# of active motor unit **increases
- allows muscle to **accomplish** increasing gradations of contractile strength
111
Muscle FIber Types by **appearance (2) **
1) **Red** Muscle Fibers
2) **White** Muscle Fibers
112
1) **Red** Muscle Fibers
high **myoglobin** content
more **mitochondria**
more **energy** stores
greater **blood** suppluy
(dark meat)
113
2) **White **muscle fibers
less **myoglobin**
less **mitochondria**
less **blood supply**
(white meat)
114
Types of Muscle Fibers by **function**
1) Slow Oxidative
2) Fast Oxidative-Glycolytic
3) Fast Glycolytic
115
1) Slow Oxidative
smallest, dark red
**least** powerful
**very fatigue resistant**
endurance (walking)
116
2) Fast Oxidative-Glycolytic
intermediate, red-pink
**moderately resistant** to fatigue
jogging/most weightlifting activities
117
3) Fast Glycolytic
large, white
powerful
intense anaerobic activity of short duration
118
Within a particular motor unit, skeletal muscle fibers are...
all the same type
119
Different motor units in muscle are recruited depending on?
task being performed
120
Muscle Contractions
(2) types
1) Isotonic
2) Isometric
121
1) Isotonic Contraction
**tension** (force of contraction) developed in muscle remains **constant** while muscle **changes length**
- results in **movement**
122
2) Isometric Contraction
tension generated not enough to exceed resistance of object being moved
**tension = resistance**
muscle does NOT change length
123
(2) types of **Isotonic Contraction**
1) Concentric
2) Eccentric
124
1) **Concentric **Isotonic Contraction
**tension** generated **\>** **resistance** of object
muscle **shortens** while generating force
125
2) **Eccentric **Isotonic Contraction
**length** of muscle **increases **
contraction in which muscle **tension \< resistance**
126
Aging - Muscle
partly due to **decreased** levels of physical activity...
humans undergo **slow, progressive loss of skeletal muscle mass** that is replaced largely by **fibrous CT & adipose tissue**
127
Muscle Strength
age 85 **vs **age 25
muscle fiber types
Muscle strength at **85** is about **1/2** that at age **25**
Compared to other 2 fiber types, relative # of **slow oxidative** fibers appears to **increase**
128
Sarcopenia
**degenerative loss** of skeletal muscle **mass**, **quality**, and **strength** associated with aging
(**0.5–1%** loss per year after age **25**)
