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KP222 > Quiz #4 > Flashcards

Quiz #4 Flashcards

(54 cards)

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1
Q

What is a muscle twitch?

A

a single contraction-relaxation cycle

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2
Q

Describe the phases of a muscle twitch.

A

latent period
- time before Ca2+ has bound to troponin

contraction phase

  • muscle tension increases to a maximum value
  • crossbridge interactions

relaxation phase
- tension decreases

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3
Q

What are series elastic elements?

A

connective tissue, tendons

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4
Q

What is an isometric muscle contraction?

A

length remains constant

contractile elements contract and create tension

load is greater than tension, stretches series elastic elements

only sarcomeres shorten, muscle does not shorten, load not lifted

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5
Q

What are the 2 types of forces in muscle contraction?

A

tension - force exerted by contracting muscle

load - force opposing contraction

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6
Q

What is an isotonic muscle contraction?

A

constant tension

when tension is greater than load

  • concentric contraction
  • muscle shortens, load is lifted

when load is greater than tension

  • eccentric contraction
  • muscle lengthens, weight is lowered
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7
Q

What is a motor unit?

A

a motor neuron and all the fibers it innervates

of muscle fibers in unit varies according to degree of fine control capability of muscle

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8
Q

What is the innervation ratio?

A

motor neurons:muscle fibers

ex. gastrocnemius has about 2000 fibers/MU
- gross movement

extraocular has about 3-5 fibers/MU
- fine movement

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9
Q

What are the muscle fiber types?

A

slow twitch (I)

  • fatigue resistant
  • lower force/power

fast twitch (IIA)

  • more fatigue resistant than IIB but less than I
  • intermediate force/power

fast fibers (IIB)

  • powerful
  • easily fatigued
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10
Q

What makes muscle contractions vary?

A

type of active motor units

of active motor units

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11
Q

What are the 2 types of twitch summation?

A

temporal

  • frequency of MU activation
  • more forceful contraction

spatial

  • # of MU recruited
  • sustained tension less than maximal, lets MU to rest in rotation
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12
Q

What happens if time between APs is too long?

A

complete recovery in between

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13
Q

What is unfused/incomplete tetanus?

A

stimuli far enough apart to allow slight relaxation

fiber not firing at max rate

wavy curve

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14
Q

What is complete tetanus?

A

muscle never beings to relax inbetween stimuli since there is no time

continuous contraction and steady tension at maximum force

at fatigue, tension decreases rapidly

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15
Q

How does resting fibre length affect muscle twitch?

A

twitch force depends on length of individual sarcomeres before contraction

optimal overlap of filaments = optimal force

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16
Q

What is the sliding filament theory?

A

tension that a muscle fiber generates is directly proportional to the number of crossbridges formed between filaments

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17
Q

Describe the principle of asynchronous recruitment.

A

MUs take turns firing/relaxing so they have time to rest and can consistently maintain uniform tension across a muscle

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18
Q

How can motor unit sizes vary?

A

size of unit
- small for delicate movements, large for strength movements

fiber diameter
- small for weaker movements, large for stronger movements

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19
Q

What is the size principle?

A

the order of motor unit recruitment is related to their size

small units recruited before large units

larger neurons are more difficult to depolarize, they require more excitatory input to reach threshold

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20
Q

What is the relationship between load and velocity of shortening?

A

inverse relationship

for a muscle to shorten, it must generate force greater than the load

when load is greater than maximum tension, velocity of shortening is zero because the load cannot be lifted

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21
Q

What differs in the contraction of fast and slow twitch muscle fibers?

A

fast fibers contract and relax 2-3x faster than slow fibers

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22
Q

What are muscle spindles? What are the fibers that compose it?

Study These Flashcards
A

detect changes in length

intrafusal fibers

  • contractile cells of spindle
  • innervated by gamma (slow) MU
  • adjust sensitivity of muscle to stretch

extrafusal fibers

  • contractile cells of muscle
  • responsible for contraction
  • innervated by alpha (fast) MU
23
Q

What are golgi tendon organs?

Study These Flashcards
A

detect changes in tension

inhibits muscle to protect against overactivity

sensory neurons from GTOs synapse on interneurons that make inhibitory synapses on motor neurons to prevent excessive contraction

24
Q

What would happen to muscle if gamma neurons did not fire?

Study These Flashcards
A

alpha MU would fire, muscle contracts but intrafusal fibers dont, less stretch experienced on centres, decreases firing rate of afferent neurons

25
What is reciprocal inhibition?
in a monosynaptic reflex, neuron synapses with antagonist muscle to inhibit activity at the same time as it activates the agonist allows for reflex to occur
26
Where are some of the locations smooth muscle exists in?
``` vessels gastrointestinal tract urinary tract respiratory tract reproductive organs ocular muscles ```
27
What are some differences smooth muscle contraction has compared to skeletal muscle?
``` can sustain contractions for longer periods of time filaments run oblique not parallel contractile fibers not in sarcomeres controlled by ANS Ca2+ comes from both ECF and SR Ca2+ does not bind to troponin ```
28
Describe smooth muscle contraction cycle.
``` voltage-gated Ca2+ channels in plasma membrane open Ca2+ triggers release of Ca2+ from SR Ca2+ binds to calmodulin Ca2+-calmodulin activates MLCK MLCK phosphorylates myosin crossbridge cycling occurs ``` relaxation: phosphotase removes phosphate from myosin Ca2+ removed from cytoplasm by Ca2+-ATPase and Ca2+-Na countertransport
29
Describe the neural regulation of smooth muscle.
innervated by ANS - both SNS and PNS may be excitatory or inhibitory NT released from varicosities
30
What are the 3 main components of the cardiovascular system?
the heart blood vessels blood
31
What are the 2 circuits of blood flow through the heart?
right = pulmonary circuit = to lungs and back for gas exchange left side = systemic circuit = to all of the tissues of the body and back for off-loading of oxygenated blood
32
What is the pericardium?
membranous sac surrounding the entire heart lubricates the heart to decrease friction
33
What are the true definition of arteries and veins?
``` arteries = vessels that travel away from the heart veins = vessels that travel to the heart ```
34
What is the SA node?
natural pacemaker of the heart
35
What are the layers of tissue of the heart?
epicardium - outer layer covering the heart for protection myocardium - middle muscular wall of the heart - contractile, concentric layers of muscle tissue endocardium - inner layer protecting valves and heart chambers
36
Which ventricle is thicker and why?
left because it has to push a stronger force of contraction to push blood to the entire body not just the lungs
37
What drives the blood flow through the heart?
pressure in different chambers
38
What are atrioventricular valves?
separate atria and ventricles right side: tricuspid left side: bicuspid/mitral
39
What are chordae tendinae?
attach to papillary muscles on muscular wall of ventricles, keep a level of tension between AV valve and papillary muscles to ensure valves close when ventricles contract prevents backflow
40
What are semilunar valves?
between left ventricle and aorta (aortic valve) and right ventricle and pulmonary veins (pulmonary valve) open with ventricular contraction, remaining blood pushes valve shut during relaxation to prevent backflow
41
What are the 2 types of myocardial cells?
contractile - 99% of cells ``` autorhythmic - can generate AP spontaneously - pacemaker cells initiates APs and establishes heart rate - conduction fibers transmits/spreads generated APs ```
42
What are some similarities of cardiac muscle to skeletal muscle?
striations | sarcomeres
43
What are some differences of cardiac muscle to skeletal muscle?
less SR, no terminal cisternae under ANS control intercalated discs to connect cells single nucleus
44
What are the 2 components of intercalated discs that connect cells together?
gap junctions - direct electrical connection of adjacent cells to make them a functional unit desmosomes - "glue" that holds cells together - proteins binding adjacent cells to allow for chemical communicatoin
45
What are the pacemaker cells of the myocardium?
SA node - where APs originate AV node - slower, but still capable of generating APs
46
What are the conduction fibers of the myocardium?
internodal pathways bundle of His Purkinje fibers
47
Describe the initiation and conduction pathway of an impulse through the heart.
AP initiated in SA node, travels through atria AV node, conduction slows (delay) bundle of His splits into left and right bundle brances Purkinje fibers travels back upwards through ventricles heart eventually returns to rest until SA node regenerates
48
What cells have the highest firing rates at rest?
SA node fastest depolarizing cells set the rate for the rest of the heart (pacemaker)
49
What is an ECG?
composite of all APs generated by nodal and contractile cells
50
What are the components or a normal ECG wave?
P wave - atrial depolarization, initiated by SA node delay at AV node QRS complex - ventricular depolarization - and atrial repolarization but this is covered up by QRS T wave - ventricular repolarization
51
What are T-type and L-type channels?
T = transient, slow depolarization L = long-lasting, rapid depolarization
52
What are funny channels and their role?
open up right after repolarization (unlike other ionic channels), lead to Na+ flow in making it less negative at -55mV, Ca2+ channels open and funny channels close T-type channels open at -50mV, L-type channels open and Ca2+ rushes in causing full depolarization and action potential K+ channels start opening, exiting the ICF and making it more negative until it is at -70mV again (resting state) and funny channels reopen never a resting phase
53
What are the 5 phases of ionic activity in the hearT?
phase 0 - membrane depolarizes - Na+ channels open phase 1 - depolarization - open Na+ channels start to close - drop in membrane potential - but Ca2+ channels start to open and K+ channels start to close, results in only small drop phase 2 - plateau - most K+ channels closed, most Ca2+ channels open - keeps membrane depolarized phase 3 - repolarization - opening K+ channels take effect, make cell more negative - Ca2+ channels close phase 4 - rest
54
What things are not possible in myocardial cell activation that are in skeletal cell activation?
twitch summation and tetanus due to long absolute refractory period

KP222 (7 decks)

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