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S1 BIO 100 A&P 1 > Muscle contraction > Flashcards

Muscle contraction Flashcards

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1
Q

General functions

A

Movement, heat production, and posture

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2
Q

Functions of skeletal muscle

A
  1. Excitability: ability to be stimulated 2. Contractibility: ability to contract or shorten 3. Extensibility: ability to extend or stretch and return to resisting length after contraction
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3
Q

Myoctes

A

Muscle fibers. Each fiber is made of several cells combined into one and therefore having more than one nucleus

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4
Q

Satellite cells

A

Stem cells that can fuse with myocites during strength training to make bigger muscle fibers - can become active post injury to produce more muscle fibers

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5
Q

Sarcolemma

A

Plasma membrane of a striated muscle fiber - transeverse T tubules

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6
Q

Sarcoplasm

A

Cytoplasm of muscle fibers

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7
Q

Sarcoplasmic reticulum

A

Network of tubules and saves in muscle fiber; smooth endoplasmic reticulum of muscle cells

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8
Q

Transverse T tubule

A

Transverse tubules unique to muscle cells; formed by inward extensions of the sarcolemma that allows electrical impulse to move deeper into the cell

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9
Q

Myofibrils

A

The cytoplasm skeleton of the muscle fiber. Very fine longitudinal fibers found in skeletal muscle cells composed of thick and thin filaments - extend lengthwise

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10
Q

Myofilaments

A

Ultramicroscopic, threadlike structures found in myofibrils; composed of myosin (thick) and actin (thin)

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11
Q

Sarcomere

A

Contractile unit of muscle cells; length of a myofibrils between two z disks

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12
Q

Myoglobin

A

Large protein molecule in the sarcoplasm of muscle cells that attracts oxygen and holds it temporarily

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13
Q

3 types of myobilaments

A
  1. Contractile: myosin (thick) and actin (thin) 2. Regulatory: tropomyosin and troponin 3. Structural: several kinds that assist to stabilize the position of thick and thin myofilaments
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14
Q

Actin

A

Thin, twisted protein strands that have sites that attract myosin heads

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15
Q

Myosin

A

Thick fibers that have “heads” that cross bridge to actin active sites

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16
Q

Tropomyosin

A

Thin strands that block actin active sites

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17
Q

Troponin

A

Globular proteins that hold tropomyosin in place

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18
Q

Excitation of sarcolemma

A

Motor neuron-specialized nerve cells that release ACh - motor endplate: folded aspect of searcolemma where motor neuron connects - ACH binds to receptors on mm fiber - neuromuscular junction - junction (synapse) between motor neuron and motor endplate - signal travels down motor neuron - signal travels down motor neuron - ACh released from end of motor neuron into synaptic cleft - ACh binds to receptors on motor endplate - electrical impulse is transmitted to the sarcolemma

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19
Q

Contraction

A
  1. impulse travels through T tubules to save of SR 2. Ca2+ released into sarcoplasm and binds to troponin (resting mm troponin holds tropomyosin in place) 3. tropomyosin molecules shift and expose active actin sites 4. myosin cross bridges and binds to actin to pull actin filaments toward center of sarcomere 5. myosin heads release and bind to next active site and pull again which results in shortening of mm fiber 6. sliding-filament model or mechanism
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20
Q

Relaxation

A
  1. SR starts pumping back Ca2+ into its sacs immediately after releasing them 2. Ca2+ removed from troponin molecules shutting down contraction 3. If no nerve impulse follows, the muscle relaxes
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21
Q

Energy sources for muscle contraction

A
  • skeletal muscle fibers fluctuate between low and high levels of activity based on relaxation and exercise/activity - a small amount of ATP is present inside resting uscle fibers (enough to power contraction for a few seconds) - if more ATP is needed, the muscle has 3 ways to produce it 1. From creatine phosphate 2. Anaerobic glycolysis 3. Aerobic respiration
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22
Q

Sources of ATP

A
  • small amount stored in mm cell- enough for a few seconds of mm activity - creatine phosphate (CP)- enough for 15-20 seconds of mm activity - glycolysis- enough for 15-60 seconds of mm activity (glycogen=glucose stored in mm) - citric acid cycle and ETC- enough for hours of activity
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23
Q

Aerobic respiration

A

Key components are oxygen and glucose

24
Q

Anaerobic respiration

A
  • pyruvate from glycolysis is converted into lactic acid - lactic acid dissociates H+ decreasing mm pH causing the burn or ache in mm
25
Q

Muscle fatigue

A

An inability of a muscle to maintain force of contraction after prolonged activity - even before true mm fatigue occurs an individual has the sensation or desire to stop activity

26
Q

Actual muscle fatigue

A
  • failure of the Na/K pumps to maintain ion concentration - inadequate calcium release from the sarcoplasmic reticulum - depletion of creatine phosphate - insufficient oxygen - depletion of glycogen - build up of lactic acid and ADP - failure of neuron to release enough acetylcholine
27
Q

Motor units

A

-consist of a somatic motor neuron and all the skeletal muscle fibers it stimulates - a single somatic motor neuron comes in contact with an average of 150 skeletal muscle fibers - all of the muscle fibers in 1 motor unit contact at the same time - typically, the muscle fibers in 1 motor unit are dispersed throughout a muscle (not clustered)

28
Q

Fine motor

A

Only a few muscle fibers per neuron - eye movements 10-2- muscle fibers per motor unit - voice box/larynx movement 2-3 fibers per motor unit

29
Q

Gross motor

A

Large scale and powerful movements have many fibers per neuron - biceps and gastroc have 2000-3000 fibers per motor unit

30
Q

Twitch contraction

A

Brief contraction of all muscle fibers in a motor unit in response to a single impulse - latent phase - relaxation phase

31
Q

Twitch contraction

A

Brief contraction of all muscle fibers in a motor unit in response to a single impulse - latent phase - contraction phase - relaxation phase

32
Q

Latent phase

A

Nerve impulse to SR to trigger release of Ca++

33
Q

Contraction phase

A

Ca++ bind to troponin and sliding of filaments occurs

34
Q

Relaxation phase

A

Sliding of filaments ceases. Ca++ is actively transported back to SR, myosin binding sites are covered by tropomyosin

35
Q

Treppe

A

Gradual, steplike increase in strength of contraction when series of twitch contractions occur about a second apart - this means a muscle contracts with more force after it has contracted a few times

36
Q

Tectonic contractions

A

tetanus - smooth, sustained contractions - muscle doesn’t have time to relax fore the next contraction starts - also calle multiple wave summation

37
Q

Incomplete tetanus

A

Tension is not sustained at a constant level

38
Q

Tonic contraction

A

Continual, partial contraction in a muscle organ - a small number of fibers in a muscle contract to produce tautness - motor units fire in relays to achieve this tone

39
Q

Muscle tone

A

Small amount of tautness due to weak, involuntary contraction of motor units - hypertonic - spastic - flaccid

40
Q

Graded strength principle

A

Skeletal muscles contract with varying degrees of strength at different times - allows us to match force with demand - factors 1. Metabolic condition 2. Recruitment of motor units 3. Effect of muscle length on strength 4. Effect of load on strength

41
Q

Metabolic condition

A

It is helpful to think of metabolism as its own system - metabolic activity is separate from muscle contraction but can positively and negatively effect contraction - if some fibers are not able to keep up with metabolic requirements to generate force the entire muscle suffers

42
Q

Recruitment of motor units

A

The more intense and frequent the stimulus, the more motor units recruited - once maximum contraciton is reached, regardless of strength or frequency of stimulus, the muscle cannot contract more strongly - motor units fire in revolving sequence

43
Q

Length-tension relationship

A

Maximal strength in mm can develop bears a direct relationship to the initial length of its fibers

44
Q

Load on strength

A

The heavier the load the stronger the contraction

45
Q

Isotonic contraction

A

Concentric and eccentric - muscle contraction in which the muscle sustains the same tension or pressure and a change in the distance between two bones occurs

46
Q

Isometric contraction

A

Muscle contraction in which muscle does not alter the distance between two bones

47
Q

Slow twitch fibers

A

Slow oxidative fibers (red fibers) - relies on oxygen to produce ATP - high concentration of myoglobin (stores O2) - highly vascular - myosin (type I) is slow acting so ATP production is able to keep up - fatigue resistant - found in postural and endurance type mm

48
Q

Intermediate twitch fibers

A

Fast oxidative-glycoytic fibers - rely on oxygen and glycogen to produce ATP - some myoglobin - some vascularity - myosin (type IIa) is moderately fast but more fatigue resistant than fast twitch fibers - found in gastrocnemius mm - sprint muscles

49
Q

Fast twitch (white fibers)

A
  • relies on glycogen to produce ATP (anaerobic process) - low concentration of myoglobin - decreased vasculatity - myosin (type IIb) is fast so rapid depletion of ATP - short duration contractions - found in muscles of fingers and eyes
50
Q

Endurance training

A

Results in a switch to oxidative, slow-twitch muscle fibers

51
Q

Resistance training

A

Increase te proportion and cross sectional area of glycolysis muscle fibers

52
Q

PGC-1alpha and PGC-1beta

A

Potent chemicals that assist in transformation of fibers, regulate metabolic disease

53
Q

Sedentary lifestyle

A

A lack of or irregular physical activity - one of the leading causes of preventable deaths worldwide - associated with: DMII, cardiovascular pathologies, obesity, postmenopausal breast cancer and other tumor types, dementia, depression, neurodegenerative events, chronic systematic inflammation

54
Q

Benies of exercise

A
  • increased lifespan - decreased hyperglycemia - decreased hypercholesterlemia - decreased HTN - improved kidney, heart, brain, and liver function - possible reduction in inflammation and circulating stress hormones
55
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56
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S1 BIO 100 A&P 1 (24 decks)

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