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BIOL 436 > Ch. 20 > Flashcards

Ch. 20 Flashcards

1
Q

Define striated muscle

A

Muscle that consists of cells in which the thick myosin and thin actin filaments are arranged in sarcomeres (in vertebrates, skeletal and cardiac muscle)

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2
Q

Name and define the three muscle types

A

Skeletal - produces locomotory movements or other external movements of the body, attached to the endoskeleton within vertebrates

Smooth - consists of small, spindle-shaped uninucleate cells without any striations (myosin and actin present, but not organized into sarcomeres), found in hollow organs such as the intestine

Cardiac - forms the wall of the heart, consists of striated cells connected by intercalated discs

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3
Q

Define myofibril

A

Longitudinal component of a striated muscle cell that consists of a series of sarcomeres and extends the length of the cell

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4
Q

Define sacromere

A

The contractile unit of striated muscle that consists of contractile, regulatory, and cytoskeletal proteins running in series separated by Z discs

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5
Q

Define thin filament

A

Polymers of G-actin monomers in muscle cells

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6
Q

Define thick filament

A

Polymers of myosin molecules in muscle cells

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7
Q

Define cross bridges

A

The head of a myosin molecule interacting with actin molecules to produce muscle contraction

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8
Q

Define excitation-contraction coupling

A

The linkage of electrical excitation of the cell membrane with contractile activity facilitated by available Ca2+ in the cytoplasm

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9
Q

Define isometric contraction

A

A contraction in which a muscle does not shorten significantly as it exerts force (tension) against a load it cannot move

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10
Q

Define isotonic contraction

A

A contraction in which muscle force remains constant as the muscle changes length, rarely occurring in nature

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11
Q

Define intercalated disc

A

An intercellular contact between adjacent cardiac muscle fibers of vertebrates that contains desmosomes and gap junctions

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12
Q

Define motor unit

A

A motor neuron and all the muscle fibers it innervates

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13
Q

Name the order of muscle structure from largest to smallest.

A
  1. Muscle
  2. Muscle fiber
  3. Myofibril
  4. Sarcomere
  5. Myofilaments (actin and myosin)
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14
Q

What are Z lines?

A

Indicators of the start and finish of a single sarcomere

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15
Q

What are I bands?

A

Contain only thin filaments

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16
Q

What are A bands?

A

Contain thin and thick filaments

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17
Q

What is the H zone?

A

Contains only thick filaments

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18
Q

What is the M line?

A

Splits the H zone in half

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19
Q

What are the three key proteins within thin filaments?

A

Actin (g-actin), troponin, and tropomyosin

20
Q

How many binding sites does the myosin cross-bridge contain?

A

Two; one for ATP and one for actin

21
Q

Which bands shorten during a contraction?

A

I and H bands

22
Q

Define rigor

A

A state of constant contraction that occurs when there is no ATP available to release myosin from actin

23
Q

Describe the step at which the cross-bridge cycle is typically found.

A

ATP has been hydrolyzed, so myosin is loosely bound to actin and waiting for Ca2+ to continue the cycle

24
Q

What would happen to a muscle without ATP?

A

Stuck in rigor without ATP releasing cross bridge

25
Q

What would happen to a muscle without ATPase?

A

Stuck in relaxed state without ATP hydrolysis

26
Q

What would happen to a muscle without calcium ions?

A

Stuck in relaxed state without Ca2+ to initiate power stroke

27
Q

What does tropomyosin do?

A

Blocks myosin-binding sites in g-actin until moved by troponin-Ca2+

28
Q

What does troponin do?

A

When bound to Ca2+, it shifts tropomyosin to expose myosin-binding sites to initiate the power stroke

29
Q

________ is released by motor neurons in an action potential.

A

Acetylcholine

30
Q

How does initial sarcolemma depolarization occur?

A

Acetylcholine binds to its receptors, which opens Na+/K+ channels to depolarize the membrane

31
Q

How is DHPR activated?

A

DHPR is voltage-sensitive, so depolarization of the sarcolemma continues into the t-tubules to change its conformation

32
Q

How are RyR calcium channels opened in the SR?

A

Activated DHPR goes through a conformation change, which allows RyRs to open and release calcium ions into the cytoplasm

33
Q

Muscle contraction _________________ (uses/produces) a lot of energy.

A

uses

34
Q

What metabolic pathways are used to supply ATP for muscle contraction? (3)

A
  1. Creatine phosphate to creatine
  2. Glycolysis
  3. Oxidative phosphorylation
35
Q

Define tonic muscles

A

Postural muscles that can stay “on” for long periods of time, also found in fish, no action potentials

36
Q

Define a twitch

A

The mechanical response of a muscle to a single action potential

37
Q

Name the three types of twitch muscles

A
  1. Slow oxidative
  2. Fast oxidative glycolytic
  3. Fast glycolytic
38
Q

Define muscle antagonism

A

One muscle shortens and an opposed muscle lengthens

39
Q

Define load

A

The object muscle exerts force onto

40
Q

Define tension

A

The force exerted on a load by muscle

41
Q

Describe isometric contraction

A

Elastic components remain the same, and sarcomeres contract

42
Q

Describe isotonic concentric contraction

A

Elastic components stretch inward, shortening sarcomeres

43
Q

Describe isotonic eccentric contraction

A

Elastic components stretch outward to prevent damage from heavier loads

44
Q

Describe load scaling

A

The same amount of force is not going to be used for the same two objects (i.e., 200-pound weight vs phone)

45
Q

Cardiac muscle cells are separated by what?

A

intercalated disc

BIOL 436 (11 decks)

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