Physiology Flashcards
(73 cards)
1
Q
Skeletal muscle
- description
- type of control
- when does it contract
A
- somatic effector
- striated
- generally voluntary control
- normally does not contract w/o nervous stimulation
2
Q
Major diff between connectivity of skeletal m compared to cardiac m
A
lacks anatomical and functional connections between individual muscle fibers
3
Q
Describe a muscle cell
A
- aka muscle fiber
- arranged end to end
- grouped into parallel bundles
- derived from myodermal myoblasts (remain in tissue to replace cells)
4
Q
Satellite cells
- describe
A
- small, little cytoplasm
- can give rise to more satellite cells OR differentiate to muscle fiber
5
Q
Proliferation of satellite cells influenced by what
A
- IGF-1 (insulin like growth factor)
- proliferations to provide growth and repair
6
Q
Three layers of skeletal muscle tissue
A
- epimysium
- Perimysium
- Endomysium
7
Q
Epimysium
A
- external sheath
- septa carry vessels and nerves inward
8
Q
Perimysium
A
- thin
- wraps bundles of muscle fibers to form fascicles (the functional unit)
- penetrated by vessels and nerves
9
Q
Endomysium
A
- very thin
- surrounds each muscle fiber
10
Q
Define:
- sarcolemma
- sarcoplasm
- sarcoplasmic reticulum
A
- plasma membrane
- cytoplasm
- like endoplasmic reticulum
11
Q
What is contained in the sarcoplasm
A
myoglobin which holds O2
12
Q
Describe the sarcoplasmic reticulum
A
- elaborate
- surrounds myofibrils
- contains Ca2+ pumps
13
Q
Terminal cisterna
A
- part of the sarcoplasmic reticulum
- sac-like junctions of SR
- release calcium
14
Q
T-tubule
A
- folds of sarcolemma (increases surface area)
- encircle myofibrils near A-I junctions
- depolarization wave runs through t-tubules deep into cell
15
Q
What is the “triad”
A
- aka sarcotubular system
- 2 terminal cistern (sarcoplasmic reticulum) and 1 T-tubule (sarcolemma)
- links calcium release and depolarization
16
Q
define myofibril
A
- filament bundle
17
Q
A band and I band
A
A band
- anisotropic
- thick filaments, myosin
I band
- isotropic
- thin filaments, actin
18
Q
Z band
A
- region of I band w/o A band overlap
- appears to bisect I band
- where actin attach, allows shortening of fiber
- edge of sarcomere
19
Q
Sarcomere
A
- functional unit of myofibril
- Z band to Z band
20
Q
Thick filament
- fiber type
- which band
- describe
A
- myosin
- A bands
- rod like tail
- two globular heads
- head contains ATP binding site and actin binding site
21
Q
M Line
A
- in the H zone
- reversal of polarity of cross bridges
- she didn’t seem to care much about this…
22
Q
Thin filament
- fiber type
- which bands
A
- actin, tropomyosin, and troponin
- I bands
23
Q
Actin
- describe
A
- composed of G actin subunits
- 2 strands coil to form actin helix
24
Q
tropomyosin
- describe
A
long filaments that spiral around actin
25
Troponin
- describe
- three types
- located at intervals along tropomyosin
- TnI: binds actin
- TnT: binds tropomyosin
- TnC: binds calcium
26
Name four additional structural proteins
- Actinin
- Titin
- Creatine kinase
- Myoglobin
27
Actinin
- binds actin to Z lines
28
Titin
- connects Z lines to myosin
- provides structure, stretch, and resistance
- can coil and stretch
29
Creatine Kinase
- at M line
- phosphorylation of ATP from phosphocreatine (holds phosphate so can turn ADP into ATP when needed)
- provides contractile E source
30
myoglobin
- holds on O2
- higher affinity for O2 than hemoglobin
- O2 will transfer from hemoglobin to myoglobin dt Bohr effect
31
Bohr affect - three factors that affect O2 dissociation
will dissociate when:
- heat
- low pH
- increased DPG
*and opposite
32
Very basic overview of muscle excitation
- somatic motor nerve is depolarized
- releases Ach
- Ach binds to nicotinic receptor on motor end plate of resting cell (muscle)
33
What is the resting potential of a muscle cell?
| What is depolarized membrane potential?
-90 mV
| 30 mV
34
Muscle cell excitation steps
- Ach triggers opening of voltage gated Na+ channels
- sodium influx
- local depolarization in all directions along sarcolemma and into T tubules
- voltage gated calcium channels on SR open, calcium not sarcoplasm
- contraction of muscle
35
action potential of muscle cells
- how long does it last
- can it be partial?
- 1-2 milliseconds
| - no, is all or none, once action potential is initiated, full contraction of stimulated cell occurs
36
What happens to calcium after it is released into the sarcoplasm?
- ATP dependent calcium pumps return calcium to sarcoplasmic reticulum
* another reason muscle contraction is ATP expensive
37
Repolarization
- returns sarcolemma to resting state
- Na+ gates close
- K+ gates open, K+ efflux
38
What is the name for the period of time during repolarization
refractory period - cannot depolarize
39
When/what returns
- electrical resting state
- ionic resting state
- electrical: during repolarization
| - ionic: via Na/K pump
40
what is the resting blockade?
Myosin binding site on actin is blocked by tropomyosin
41
What happens when calcium binds troponin
- binds to TnC
- conformational change in tropomyosin
- myosin binding site on actin exposed
42
Describe steps after myosin binding site of actin is exposed
- myosin head binds myosin binding site on actin (cross bridge attachment)
- powerstroke
- repeat until calcium concentration decreases
43
Powerstroke steps
- release of ADP = myosin head pivots (release of energy)
- draws actin toward
center of sarcomere
- head binds ATP, releases actin
- ATP hydrolysis cocks head to attachment position
44
About how many power strokes per head
5
45
What is a motor unit
- motor neuron and all the muscle fibers it supplies
- one motor nerve has 100s of axons branching to many axonal terminals
- when nerve fires, all fibers served are stimulated
46
What does it mean that the fibers served by a motor neuron are not clustered?
stimulation of a single motor unit causes weak contraction of the entire muscle
47
About how many fibers per motor unit?
average is 150 fibers/motor unit
48
Muscle twitch
- single action potential causes brief contraction followed by relaxation
- there is a small latent period between action potential and start of contraction
- duration of twitch varies with muscle type
- can trace on myogram
49
Slow twitch fibers
- myoglobin
- cell description
- myosin ATPase
- contraction
- primary E source
- metabolism type
- length of contraction
- abundant myoglobin = red
- thin cells
- slow acting myosin ATPase (allows for globular head to move, allows contraction)
- slow contraction
- fat is primary E source
- aerobic metabolism
- can contract for long periods
50
fast twitch fibers
- myoglobin
- cell description
- myosin ATPase
- contraction
- primary E source
- metabolism type
- length of contraction
- less myoglobin = white
- large cells
- fast acting myosin ATPase
- quick, powerful contraction
- abundant glycogen reserve
- glucose is primary fuel
- anaerobic pathway, lactic acid production
- quickly fatigued
51
What does graded muscle responses mean?
variations in degree of contraction. Depends on
1. rate at which firing (increased rapidity of stimulus to create contraction)
2. recruiting increased number of motor units
*muscle contractions are smooth and prolonged, not a muscle twitch
52
Wave summation
- subsequent impulses create a stronger contraction that appears to build on prior contractions
- when second contraction is stimulated before muscle has completely relaxed
- creates smooth, continuous muscle contraction
53
Tetany
- no muscle relaxation
- wave summation results in continue contraction
- nerve stimulus is in rapid succession
- fatigue of m eventually occurs (run out of O2, ATP, etc.)
54
Treppe
- staircase effect in contraction, subsequent contractions are greater strength despite same stimulus
- activity produces heat = enzymes more efficient
- increases avail of calcium for contraction
* why warm up before exercise
55
How is force of contraction increased?
increased number of motor units stimulated
56
Delicate touch vs. strong grip
- delicate: few motor units
- Grip: many motor units
*still all or none!!
57
Muscle tone
- relaxed m exhibits certain amt of contraction (tone)
- involuntary
- d/t spinal reflexes in response to stretch receptors in muscle/tendon
- provides joint stability, maintains posture, readiness for stimulation
58
Describe muscle tension
- force exerted by a contracting muscle
59
Describe load
- weight or reciprocal force exerted by objection on muscle
- thing muscle is trying to move
- influences velocity and duration of muscle work
60
Describe movement
tension overcomes load
| - greater the load, longer the latent period, slower the contraction and shorter duration of contraction
61
Isotonic contraction
- tension exceeds load
- muscle shortens
- load is moved
* movement of body
62
Isometric contraction
- tension equals load
- muscle does not shorten
- load is not moved
* posture and balance
63
what type of contraction (isotonic vs. isometric) are most movements?
combo of both :)
64
Describe length-tension relationship
- ideal stretch that produces maximal force of contraction (resting length)
- related to sarcomere length and overlap of myofibrils
- skeletal m are attached to bones at optimum length, slightly stretched to voice max movement
65
What is required for all muscle contractile events
ATP
* crossbridge stroke and detachment
* calcium pump, returns calcium to SR
66
How does muscle get ATP?
little stored in muscle, most must be generated
67
List two sources of energy for muscle
1. Glucose
| 2. Fatty Acids
68
Glucose energy source for muscles (2)
- via circulation
| - glycogenolysis (from glycogen stored in m tissue)
69
Fatty acid energy source for muscles
- TG in muscle cells and circulation
- lipolysis from adipose, release FA to circulation, 2 carbon bodies enter Krebs cycle as acetylene-coA
*muscle loves fat as an E source
70
Anerobic respiration for muscle metabolism
- glucose into glycolysis
- pyruvate is oxidized to relish NADH
- ATP and lactic acid are produced
- lactate converted to pyruvate once O2 is available
71
Creatine phosphate
- liver produces creatine from arg, gly, meth
- creatine kinase phosphorylates creatine into phosphocreatine which is stored in muscle cells
- CK-MB acts at junction of myosin head/actin to provide phosphate to generate ATP from ADP for contraction
- can be regenerated
72
what is creatinine
- breakdown product of creatine phosphate
| - marker for renal function :)
73
List the energy sources from shortest to longest duration
- ATP
- creatine phosphate (4 sec)
- anaerobic glycolysis (2-3 min)
- aerobic glycolysis (1-2 hours)
- fatty acid oxidation (many hours)
