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Physiology > L17, L18, L19, L20 Muscles (not all info! - see drawings) > Flashcards

L17, L18, L19, L20 Muscles (not all info! - see drawings) Flashcards

1
Q

what is isometric contraction?

A

muscle develops tension, but DOES NOT SHORTEN
cannot lift objective
example - pushing palms of hands together

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2
Q

what is isotonic contraction?

A

muscle SHORTENS while pulling a constant LOAD (AFTERLOAD)

weight of load unchanged, muscle tension is constant!

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3
Q

define preload

A

the muscle resting length prior to contraction

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4
Q

what is preload determined by

A

stretch of the muscle

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5
Q

when you increase length, what happens to preload

A

increase

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6
Q

what is the length tension relationship

A

amount of tension a muscle generates depends on how stretched it is before it is stimulated to contract

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7
Q

what are the 3 measurements of tension that can be made as a function of resting length (preload)

A

passive tension
active tension
total tension

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8
Q

what does the speed of shortening depend on?

A

afterload

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9
Q

what is passive tension?

A

tension developed by stretching muscle to different lengths

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10
Q

what is active tension?

A

active force developed when muscle contracts

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11
Q

what is total tension

A

active + passive

tension when muscle is stimulated to contact at different preloads

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12
Q

active tension is proportional to what

A

the number of cross bridges formed

*it is max tension when there is an max overlap of thick and thin filaments = max crossbridging!

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13
Q

what happens to active tension when you increase passive tension?

A

decrease

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14
Q

when are maximal muscle contractions achieved?

A

when muscle fiber is at optimal length

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15
Q

what is the velocity of shortening affected by

A

load

resting muscle length (preload)

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16
Q

what happens to velocity when you increase preload to optimum

A

increase

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17
Q

what happens in a muscle contraction

A

a single AP
release calcium
a single twitch

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18
Q

if a muscle fiber is restimulated after it has completely relaxed, the second twitch is the ___ magnitude as the first twitch

A

same

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19
Q

if a muscle fiber is restimulated before it has completely relaxed, the second twitch is _____ which results in___

A

added to the first twitch

summation

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20
Q

is a muscle fiber is stimulated so rapidly that it does not have an opportunity to relax at all between stimuli, _____ occurs

A

tetanus - max sustained contraction

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21
Q

what happens to relaxation time as stimuli are repeated at rapid interval?

A

shorter and shorter until tetanus = no relaxation time!

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22
Q

what is muscle fatigue

A

loss ability for muscle to generate force

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23
Q

what can cause muscle fatigue?

A 
nerve (nerve fatigue)
muscle cells (metabolic fatigue)
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24
Q

what happens with nervous fatigue

A

after a period of max contraction, nerve signal reduce in frequency and the force generated by contraction diminishes - no pain = muscle “stops listening” and stops moving

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25
an increase in tension reflects accumulation of what
calcium in cytosol
26
what is the major mechanism for adjusting strength of contraction in skeletal muscle?
adjust frequency of AP traveling down motor neurons to muscle fibers
27
what is another way to control muscle contraction besides adjusting frequency of AP?
recruitment of motor units and fibers
28
what is muscle force dependent on
number of contracting fibers
29
what are the similarities between skeletal and cardiac muscle?
- both have sarcomeres with z disks - sarcomeres made of thick and thin filaments (iwth tropomyosin and troponin) - sliding filament model + crossbridging - T tubules - excitation contraction coupling (AP --> tension)
30
what are the major differences between skeletal and cardiac muscle?
- sarcoplasmic reticulum is not as well developed in cardiac cells - t tubule system runs in both transverse and longitudinal directions - cells function as a syncytium - cell joined at intercalated disks - cells held together by desmosomes - cell connected by gap junctions - cells are branches to form a network - muscle fibers are morphologically different in different areas of the heart
31
where does most of the Ca2+ come from if the sarcoplasmic reticulum isn't well developed?
extracellular
32
what is calcium induced calcium release?
a biological process whereby extracellular calcium is able to activate calcium release from intracellular Ca2+ stores (e.g. endoplasmic reticulum or sarcoplasmic reticulum) occurs in cardiac muscle cells
33
why can the heart never develop tetany?
the long refractory period will not allow for it | - still can get treppe and summation though
34
what is the resting length/left ventricular end diastolic volume (preload)?
length of muscle fibers at end of diastole just before contraction
35
what is starlings law of the heart?
the greater the end diastolic volume (preload), the greater the ventricular pressure that can be developed ==> greater the contraction!
36
cardiac muscles is less ___ than skeletal muscle
distensible | when stretched extensively = damage to tissue
37
how do you change the strength of contraction?
1. change EDV (preload) | 2. change cytosolic [Ca2+] = cardiac contractility (inotropism)
38
what is contractility?
intrinsic ability of myocardial cells to develop force at a given muscle length - correlated directly with [Ca2+] - without changing the muscle length
39
how do you change contractility?
1. neurohumoral factors - NE increases sarcolemma permeability to Ca2+ 2. increasing the frequency of contraction = treppe
40
what does the tension generated by a skeletal muscle depend on?
1. properties of individual muscle fibers 2. properties of motor units 3. recruitment of motor units
41
what are the different types of muscle fibers?
``` slow oxidative (type 1) - red - marathon fast oxidative-glycolytic (type IIa) - red fast glycolytic (Type IIb) - white - sprints ```
42
what does muscle fiber type depend on?
the nerve the innervates the fiber muscles are a mix of fiber types but one type dominates over others
43
how do you increase the strength and speed of contraction?
increase the amount of Ca2+ change the length of muscle fibers change the frequency of stimulation (intra Ca2+) size of muscle fibers (hypertrophy) number of muscle fibers in motor unit (hyperplasia) recruitment of motor units ADJUST THE FREQUENCY OF AP TRAVELING DOWN A MOTOR NEURON TO A MUSCLE FIBER
44
what systems supply ATP energy for muscle contraction?
phosphocreatine glycogen glucose, fatty acids, amino acids
45
what is an immediate source of ATP for muscle
creatine phosphate
46
what is the main source of ATP when O2 is absent?
anaerobic metabolism - glycolysis ==> pyruvate -> lactic acid
47
what is the main source of ATP when O2 is present?
aerobic metabolism - oxidative phosphorylation - fueled by glucose, FA, aa from food!
48
when does oxygen debt remain until?
until excess lactic acid is metabolized into CO2 and H2O or converted to glucose in liver
49
are there actin and myosin filaments in smooth muscle?
yes
50
what layers do smooth layers generally present in?
circular layer - squeeze/dilate | longitudinal layer - stretch or shorten
51
how are the actin and myosin filaments arranged in smooth muscle?
actin filaments radiate from dense bodies | myosin filaments between actin - look at picture!
52
how are dense bodies in smooth muscle attached to one another?
by intracellular protein bridges - serves as Z disks
53
what appearance does smooth muscle take on once it is contracted?
globular appearance
54
what muscles are examples of multiunit smooth muscle
iris ciliary m. vas deferens piloerector m.
55
are AP common in multiunit smooth muscle?
no - fibers are too small
56
how do multiunit smooth muscles contract?
ANS stimulation - varicosities - which hold NT ACh and NE = local depolarization ("junctional potential" => spreads over fibers = contraction
57
what muscles are examples of unitary smooth muscle?
``` Gi tract bile ducts bladder ureter uterus blood vessels ```
58
do AP occur in unitary smooth m.?
yes - muscle fibers depolarize simultaneously before AP occurs - nerve impulses spread via gap junctions
59
describe a spike smooth muscle action potential
typical- elicited by an external stimulus (electrical stim, hormones, stretch, spontaneously)
60
describe a plateau smooth muscle action potential
uterus, ureter, vascular smooth. repolarization delayed up to 1 sec due to Ca2+ channels self excitatory - AP elicited without extrinsic stimulation (GI wall)
61
describe a slow wave smooth muscle action potential
(pacemaker waves) = low oscillation of RMP - do not reach threshold unless strong enough if slow wave potential reaches threshold trains of action potential are generated - rhythmical contractions interstitial cells of Cajal - pacemakers for the electrical and contractile activity of smooth muscle
62
where does Ca2+ come from in smooth muscle contractions?
extracellular!
63
what does Ca2+ bind to in smooth muscle?
calmodulin
64
describe a phasic contraction
twtich like shortening followed by relaxation
65
describe a tonic contraction
force is sustained for long periods - ability to maintain force of contraction with decreased numbers of activated crossbridges greatly reducing levels of energy consumption (ATP turnover)
66
what type of contractility or tone does smooth m. exhibit (important)
continuous low level
67
arteriole contract ____ throughout life
tonically - sustained contraction of a muscle
68
how is the length tension relationship in smooth muscle different from skeletal muscle?
smooth m. - can develop tension over a greater range of lengths - allows smooth m. to develop tension even with relatively large increases in organ volume - stomach, bladder etc.
69
what channels are involved in smooth m. that increase cytoplasmic Ca2+ and promote contraction?
v-g- Ca2+ channels - opens with AP depolarization L-g Ca2+ channels - receptor mediated - hormones, NT IP3-gated SR Ca2+ channels- receptor mediated - hormones, NT stretch-activated channels leak channels
70
what processes of smooth m. decreased internal Ca2+ and promote relaxation?
Ca ATPase pump - 2 Ca2+/Na+ exchanger Na+/K+ ATPase pump
71
what is Raynaud's phenomenon?
skin discoloration (upon temp or emotional changes) due to abnormal spasm of vascular smooth muscle in peripheral tissues - diminished blood supply to local tissues turn white - dimished blood supply turn blue - prolonged lack of oxygen turn red - blood vessels reopen = flushing

Physiology (16 decks)

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