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First Semester: Physiology 1 > Lecture 10: Muscles 1 and 2 > Flashcards

Lecture 10: Muscles 1 and 2 Flashcards

1
Q

Three types of muscle

A

Skeletal
Smooth
Cardiac

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2
Q

Skeletal

A

Attached to bones, moves and supports the skeleton. Striated/voluntary

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3
Q

Cardiac

A

Muscle of the heart. Striated/involuntary

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4
Q

Smooth

A

Surrounds hollow cavities and tubes. Unstriated/involuntary

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5
Q

4 functions of muscle tissue

A
  1. Motion
  2. Movement of substances within body
  3. Stabilizes body position and regulates organ volume
  4. Thermogenesis
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6
Q

Motion

A

Movements like walking/running

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7
Q

Movement of substances in body

A

All three types of muscle help move substances like blood, food, sperm, ova, and urine

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8
Q

Stabilizing body position/regulate organ volume

A
  • Skeletal contractions maintain stable body positions and posture
  • Sustained contraction of smooth muscle block exit of food from the stomach and urine from the bladder for temporary storage
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9
Q

Thermogenesis

A

Skeletal muscle contractions generate heat to help maintain normal body temp

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10
Q

Five characteristics of muscle tissue

A
  • Excitability
  • Conductivity
  • Contractibility
  • Extensibility
  • Elasticity
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11
Q

Excitability

A

The property of responding to stimuli by producing action potentials

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12
Q

Conductivity

A

Ability of cell to conduct action potentials along plasma membrane

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13
Q

Contractibility

A

Ability to shorten and contract. The generation of force to do work.
Muscle contracts in response to action potential

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14
Q

Extensibility

A

Ability to be extended or stretch

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15
Q

Elasticity

A

The ability to return to its original shape after contraction of extension

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16
Q

An extensive vascular network

A
  • delivers oxygen and nutrients

- carries away metabolic waste generated by active muscles

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17
Q

Blood vessels usually enter muscle in company with

A

nerve supply

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18
Q

Once the vasculature is in the muscle tissue

A
  • the vessels and nerves branch through the muscle

- Arterioles supple blood to a capillary network that surrounds each individual muscle fiber

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19
Q

Skeletal muscles contract only under stimulation from

A

CNS

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20
Q

Axons penetrate muscle tissue to

A

innervate individual muscle fibers

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21
Q

Muscle fiber

A

muscle cells

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22
Q

Myofibrils

A

Threadlike parallel fibers of a muscle cells

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23
Q

Myofilaments

A

Thick and thin protein threads that makeup myofibrils

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24
Q

Myosin

A

Thick myofilaments

Contractile protein

25
Q

Thin myofiliments

A

Actin
Tropomysin
Troponin

26
Q

Sarcomere

A

Basic contractile unit

27
Q

Myosin (thick filament) composition

A
  • One pair of heavy chains and two pairs of light chains
  • Most of heavy chain has alpha-helical structure in which the two chains coil around each other to form the tail of the myosin molecules
  • Four light chaisn and the N-terminus of each heavy chain form two globular heads on the myosin molecule
28
Q

The myosin globular heads have

A
  • An actin binding site which is necessary for cross-bridge formation
  • A site that binds and hydrolyzes ATP (myosin ATP)
29
Q

Actin composition

A
  • Consists of globular protein called G-actin
  • Polymerization of G-actin to F-actin = two thin filaments twisted into an alpha-helical structure
  • Has myosin binding sites which are covered by tropomyosin in a resting muscle, thus preventing interaction between actin and myosin
30
Q

Tropomyosin is a ____ protein

A

regulatory

31
Q

Tropomyosin function

A

Filamentous, it runs along the groove of each twisted actin filament. At rest, it blocks myosin binding sites on actin
-If contraction occurs, it must be moved out of the way so that the actin and myosin can interact

32
Q

Troponin is a ___ protein

A

regulatory

33
Q

Three globular proteins of troponin

A
  1. Troponin T
  2. Troponin I
  3. Troponin C
34
Q

Troponin T

A
  • T for tropomyosin

- Attaches the troponin complex to tropomyosin

35
Q

Troponin I

A
  • I for inhibition
  • Binds troponin to actin
  • Along with tropomyosin, it inhibits the interaction between actin and myosin by covering the myosin binding site on actin
36
Q

Troponin C

A
  • C for calcium
  • A Ca binding protein that plays a central role in the initiation of contraction

-Increase in intracellular Ca concentration -> Ca binding to troponin C -> conformation change in the troponin complex -> moving of tropomyosin out of the way -> binding of actin to the myosin heads

37
Q

Sarcomere

A
  • Contractile unit of a striated muscle

- The area between two Z lines within a myofibril

38
Q

Sliding filament mechanism

A

All sarcomeres shorten simultaneously, so the entire fiber becomes shorter

39
Q

Actin and myosin are often referred to as ____ proteins

A

contractile

40
Q

Tropomyosin and troponin are often referred to as ____ proteins

A

regulatory

41
Q

Sliding filament mechanism

A
  • Thin filaments on each side of a sarcomere slide inwards towards the center of the A band
  • As they slide inwards, the thin filaments pull the Z lines to which they are attached closer together so the sarcomere shortens
42
Q

Sarcolemma

A
  • Cell membrane

- Has a characteristic transmembrane potential

43
Q

What is the first step that leads to contraction?

A

A sudden conducted change in the transmembrane potential

44
Q

Transverse tubules

A

Extensive network of sarcolemmel membranes that invaginates deep into the muscle fiber

45
Q

Transverse tubules are responsible for

A

Carrying depolarization from AP’s at the muscle surface to the interior of the fiber

46
Q

Transverse tubules make contact with the terminal cisternae of the sarcoplasmic reticulum via a voltage-sensitive protein called

A

the dhydropyridine receptor

47
Q

Sarcoplasmic reticulum

A

An internal tubular structure which is the site of storage and release of Ca for excitation-contraction coupling

48
Q

How is a high concentration of Ca maintained in SR?

A

Ca is bound to calsequestrin (a Ca binding protein)

49
Q

Ryanodine receptors

A

the Ca release channels in the SR

50
Q

How does the SR accumulate Ca?

A
  • Ca+ ATPase in the membrane
  • It pumps Ca from the ICF in the membrane fiber into the interior of the SR, keeping the intracellular Ca concentration low when the muscle fiber is at rest
51
Q

Why does the onset of the resultant contractile response lag behind the action potential?

A

The entire excitation contraction coupling process must take place before cross-bridge activity begins

52
Q

Three phases of excitation-contraction coupling

A
  • Latent period
  • Contraction time
  • Relaxation time
53
Q

Latent period

A

The time between stimulation and the onset of contraction

54
Q

Contraction time

A

The time from onset of contraction until peak tension is reached

55
Q

Relaxation time

A

The time from peak tension until relaxation is complete

56
Q

Mechanism of black widow spider venom at neuromuscular junction

A

Causes explosive releae of ACh from storage vesicles which results in prolonged depolarizarion; the most detrimental consequence is respiratory failure

57
Q

Mechanism of clostridium botulinum toxin at neuromuscular junction

A
  • Blocks release of Ach from the nerve terminal in response to an AP in the motor neuron
  • Prevents response to nerve impulses
  • Death due to respiratory failure due to inability of the diaphragm to contract
58
Q

Ach receptor blocker (Ex. Curare) mechanism of action at the neuromuscular junction

A
  • Binds irreversibly to the ACh receptor site at the neuromuscular junction (motor end plate)
  • Lack of stimulation of muscle and muscle paralysis
  • Primary use is to produce skeletal muscle relaxation
  • Ex. tubocurarine
59
Q

Organophosphates mechanism of action at the neuromuscular junction

A
  • A group of chemicals that irreversibly inhibit acetylcholinesterase
  • Inactivation of released ACh
  • Can lead to death due to respiratory failure because diaphragm is unable to repolarize and return to resting condition, then contract again to bring in a fresh breath of air
  • Found in pesticides and nerve gas

First Semester: Physiology 1 (34 decks)

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