Chapter 8-muscle Physiology Flashcards
(73 cards)
0
Q
Skeletal muscle
A
Striated and voluntary
Attached to bone
1
Q
Functions of muscle
A
Generate force
Produce movement
Produce heat
2
Q
Smooth muscle
A
No striated and involuntary
Ex. Peristalsis, vasodilation
3
Q
Cardiac muscle
A
Striated and involuntary
4
Q
Muscle consists of a number of muscle fibers lying parallel to one another held together by _________
A
Connective tissue
5
Q
Muscle fiber
A
Single muscle cell
6
Q
Multinucleated
A
May have >100
Formed from my oblasts (embryonic cells)
7
Q
Sarcoplasmic
A
Cytoplasm within muscle cell
8
Q
Sarcoplasmic reticulum
A
- Modified Endoplasmic reticulum
- Ends of segments expand to form saclike regions - terminal CISTERNAE
- System of tunnels
9
Q
Transverse tubules
A
Penetrate into muscle fiber from sarcolemma
- action potential on surface membrane spreads down into t-tubule
10
Q
Transverse tubules - spread of AP down a t tubule triggers ________________
A
Release of calcium from SR into Sarcoplasm
11
Q
Myofibrils
A
Contractile elements of muscle fiber
Contains the myofilaments
12
Q
Thick filaments
A
Myosin
13
Q
Thin filaments
A
Actin
14
Q
Sarcomere
A
Functional unit of skeletal muscle
- found between two z-lines (connects thin filaments of two adjoining sarcomeres)
15
Q
A band
A
Made up of thick filaments along with portions of thin filaments that overlap on both ends of thick filaments
16
Q
H zone
A
Lighter area within middle of A band where thin filaments do not reach
Myosin only
17
Q
M line
A
Extends vertically down middle of A band within center of H zone (middle)
18
Q
I band
A
Consists of remaining portion of thin filaments that do not project into A band (actin only )
19
Q
Proteins in muscle (list 3)
A
Contractile
Regulatory
Structural
20
Q
Myosin
A
- golf club
- component of the thick filament
- tails oriented toward center of filament and globular heads protrude outward at regular intervals
- heads form cross bridges between thick and thin filaments
- has two important sites critical to contractile process
21
Q
Two critical sites for contractile process of myosin
A
- actin binding site
- myosin ATPase site
22
Q
ATPase of myosin
A
- splits ATP into ADp and Pi
- energy released is transferred to the myosin head
- this causes the myosin head to be cocked
- analogy - pulling back a rubber band
23
Q
Actin
A
- spherical in shape
- contains two other regulatory proteins
- each actin molecule has special binding site for attachment with myosin cross bridge (actin active site)
24
regulatory proteins - found on _______
thin filament
25
tropomyosin
- thread-like molecules that lie end to end alongside groove of actin spiral
- regulatory protein
- covers actin active sites blocking interaction that leads to muscle contraction
26
troponin
- thumb tack
- regulatory protein
- made of three polypeptide units:
* binds to tropomyosin, actin, and calcium
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troponin - when not bound to _____, troponin stabilizes tropomyosin in blocking position over actin's cross-bridge binding sites
calcium
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when calcium binds to _____, ________ moves away from blocking position
troponin
| tropomyosin
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with tropomyosin out of the way, _____ and ______ are free to interact
actin
| myosin
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structural protein - ______
titin
| extends in both directions from M line along length of thick filament to Z lines at opposite ends of sarcomere
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two important roles of titan
1. stabilize myosin
| 2. acts like a spring to provide elasticity
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excitation - contraction coupling
how APs cause contraction
33
sliding filament mechanism
how the sarcomere shortens
| - how do myosin and actin interact to have this happen
34
muscle contraction steps
1. AP travels down motor neuron to NMJ where synaptic transmission occurs
2. AP travels down T tubules
3. Ca+ released from SR
4. Ca+ binds with troponin and tropomyosin moves away from actin
5. Actin active sites binding sites are exposed
6. myosin crossbridges bind with actin
7. ADP and Pi are released from myosin to change myosin's shape
8. myosin head bends toward center of sarcomere = power stroke
9. actin slides over myosin
10. new ATP binds to myosin to detach it from actin
11. cycle is repeated
35
contraction continues if ____ is available and ____ level in sarcoplasm is high
ATP
| Ca+
36
during shortening: Z lines ________
get closer
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during shortening: H zone ______
shortens
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during shortening: A _____
same
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shortening: I band _____
shortens (only actin)
40
muscle relaxation steps
1. motor neuron AP stops
2. AChE breaks down ACh at NMJ
3. muscle fiber AP stops
4. reuptake of Ca+ into SR
5. TT complex cover actin active sites
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rigor mortis
state of muscle rigidity post death
- there is no ATP being produced
- Ca+ leaks out of SR
- sliding filament mechanism begins
- no ATP to break crossbridges
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length tension relationship
sarcomeres can generate the most tension when the overlap of filaments is optimal
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tension generated is determined by _______
the number of crossbridges that can be formed
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finely controlled movement
contain fewer fibers per motor unit
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coarsely controlled movement
have larger number of fibers per motor unit
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twitch
- brief, weak contraction
- produced from single AP
- too short and too weak to be useful
- normally does not take place in body
- ex. gastrocnemius in frogs
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twitch summation
if the muscle fiber is stimulated before it has completely relaxed
- results from sustained elevation of cytostolic calcium
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tetanus
sustained contraction
- occurs if muscle fiber is stimulated so rapidly that it does not have a chance to relax between stimuli
- contraction is usually 3 to 4 times stronger than a single twitch
- caused by greater crossbridge cycling
- maximum calcium release and prolonged removal
49
what causes power stroke?
when ADP and Pi leave
50
isotonic muscle contraction
muscle tension remains constant as muscle changes length
| ex. angle changes
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isometric contraction
muscle length remains constant to generate force
| ex. when you plant your foot
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steps requiring ATP
splitting of ATP by myosin
binding of ATP to myosin
active transport of Ca+
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steps requiring ATP: splitting of ATP by myosin
provides energy that leads to power stroke (cock the head)
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steps requiring ATP: binding of ATP to myosin
to detach from actin
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steps requiring ATP: active transport of Ca+
back into SR during relaxation depends on energy derived from breakdown of ATP
56
3 biochemical pathways: transfer of high-energy phosphate from ______ to ADP
PC
- < 1 minute (amount of ATP that lasts)
- first energy at onset of x - used for short-burst, high-intensity x
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creatine
molecule capable of storing ATP energy
| - creatine + ATP --> PC + ADP
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creatine phosphate
molecule with stored ATP energy
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3 biochemical pathways: oxidative phosphorylation
(CAC and ETC)
- takes place within muscle mitochondria IF sufficient O2 is present
- fuel from glucose/glycogen or fatty acids
- relatively slow to generate ATP
- aerobic exercise - sustainable, non-fatiguing, system working most to produce ATP
60
3 Biochemical pathways - Glycolysis
- supports high-intensity exercise, burst of power, quick to fatigue (anaerobic exercise)
- much faster than oxidative phosphorylation
61
muscle fatigue
when exercising muscle can no longer respond to stimulation
- defense mechanism that protects muscle from reaching point at which it can no longer produce ATP
- underlying causes of muscle fatigue are unclear
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slow oxidative fibers (type 1)
dark (red meat)
- low myosin ATPase activity
- slow
- high to fatigue
- high oxidative phosphorylation
- many mitochondria
- many capillaries
- high myoglobin content
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fast oxidative fibers (type IIa)
- high myosin ATPase activity
- fast
- high oxidative phosphorylation capacity
- many mitochondria
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fast glycolytic fibers (type II x)
- high myosin ATPase activity
- fast
- low to fatigue
- few mitochondria
- few capallaries
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produce ATP by ________
oxidation phosphorylation
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smooth muscle: found in ______
walls of hollow organs and tubes
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smooth muscle characteristics
- spindle shaped cells
- no sarcomeres
- circular and longitudinal fibers to allow for peristalsis
- thin filaments contain tropomyosin, but lack troponin
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smooth muscle: Ca+ binds to _______
calmodulin
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smooth muscle: muscle contractions are _______
slow and sustained
70
2 types of smooth muscle: multiunit
- in large blood vessels
- in large airways to lungs
- function independantly
- must be stimulated by nerves
- in order to get contraction, a nerve has to talk to it
71
2 types of smooth muscle: single unit
- visceral smooth muscle (in guts)
- contract as a single unit
- exhibit pacemaker activity
- arranged in sheets
- will still contract if no nerves stimulate it
72
steps in smooth muscle contraction
1. AP causes voltage gated Ca+ channels to open
2. Ca+ in the cell interacts with calmodulin
3. Ca+ calmodulin complex activates enzymes
4. causes myosin head to be phosphorylated
5. myosin interacts with actin
6. contractions are slow and sustained
