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Human Biology > Chapter 13 > Flashcards

Chapter 13 Flashcards

1
Q

Types of muscles

A
  • skeletal muscle: striated, voluntary, multiple nuclei
  • Cardiac muscle: striated, involuntary, intercalated disks
  • smooth muscle: nonstriated, involuntary, visceral
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2
Q

General functions of muscles

A

Movement: production movement of the body as a whole (locomotion) or its parts
Thermogenesis: Heat production
Posture: maintains body position through partial contractions

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3
Q

Skeletal muscle function

A

Excitability: “irritability” the ability to respond to regulatory mechanism, such as a nerve signal
Contractibility: the ability to contract or shorten “pulling the ends together”
Extensibility: the ability to extend or stretch

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4
Q

Muscles are named according to what?

A

Location
Function
Shape
Direction of fibers
Number of heads
Points of attachment
Size of muscle

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5
Q

Skeletal muscle structure

A
  • the structure called skeletal muscles are considered organs
  • six muscles shaped are often used to describe and categorize skeletal muscle
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6
Q

Parallel

A
  • long strap-like muscle with parallel facials
  • most typical
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7
Q

Convergent

A

Fascicles that radiate out form a small to a wider point of attachment

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8
Q

Pennate

A
  • “feather-like”
  • unipennate -> have fascicles that anchor to only one side of the connective tissue shaft
  • bipennate -> have a double-feathers attachment point
  • multipennate -> have numerous interconnective quill-like fascicles converging on a common point of attachment
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9
Q

Fusiform

A

Have fascicles that may be close to parallel in the center or “belly”, of the muscle but converge to a tendon at one or both ends

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10
Q

Spiral

A

Have fibers that twist between their points of attachment

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11
Q

Circular

A

“Orbicular”/“sphincters”
Circle body tubes or openings

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12
Q

Origin

A

The point of attachment that odes not move when the muscle contracts

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13
Q

Insertion

A
  • the point of attachment the moves when the muscle contracts
  • The insertion bone therefore moves along a “line of force” toward the origin bone when muscle shortens
    • although the origin and insertion are convenient terms, the do not always provide the necessary information needed to understand the full functional potential of muscle action
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14
Q

Skeletal muscles almost always do what

A

Almost always act in groups rather than singly

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15
Q

Agonist

A

“Prime mover”
- used to describe a muscle that directly performs a specific movement

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16
Q

Antagonist

A
  • muscles that, when contracting, directly oppose the agonists
    • important in providing precision and control during contraction of the prime mover
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17
Q

Synergists

A
  • muscle that contract at the same time as the prime mover
    • assist the agonist in to produce a more effective movement
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18
Q

Fixator muscles

A
  • generally, function as joint stabilizers
  • maintains posture or balance during contraction or prime movers acting on joints in the arms or legs
    - assist the agonist, which classify them as a type of agonist
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19
Q

Myocytes

A

Muscle cells
Often called muscle fibers
These cells are long, thin, thread-like shaped
Multi mucleated

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20
Q

Sarcolemma

A

Plasma membrane of a muscle fiber

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21
Q

Sarcoplasm

A

The cytoplasm of a muscle fiber

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22
Q

Sarcoplasmic reticulum

A
  • network of tubules and sacs that temporarily store and release calcium ions (Ca++)
    • “muscle cell smooth ER”
23
Q

T-tubules

A
  • a system of transverse tubules that cover sarcoplasm, at a right angle to the long axis of the cell
  • the tubules allow electrical signals to travel along the sarcolemma and deep into the muscle fiber
24
Q

Triad

A
  • structure that allows electrical impulses traveling along a T-tubule to stimulate the membranes of adjacent sacs of the SR
  • at rest calcium ion pumps in the SR pump Ca++ into the SR
  • during activation after an electrical impulse travels along the sarcolemma and down the t-tubule, the Ca++ gates open in the SR in response to the voltage fluctuation
    - flowing the sarcoplasm with Ca++
25
Q

Actin

A

“Thin filament”
- protein molecules (G-actin) that are strung together like beads to form two fibrous strands (F-actin) that twist around each other to form a thin myofilament

26
Q

Myosin

A

“Thick filament”
- myosin proteins that are bundles together with doubled “heads” what protrude out of the
- Actin and myosin are chemically attracted to each other, when they are joined together, they form cross-bridges

27
Q

Troponin

A
  • protein molecules attached to tropomyosin, spaced at intervals along the thin filament
  • the protein molecule chemically bonds with Ca++
28
Q

Tropomyosin

A
  • protein molecule that forms a very thin string along the active site of the actin
  • blocking the chemical bond with myosin
29
Q

Myofibrils

A

Bundle of very fine myofilaments

30
Q

Myofilaments

A
  • the smallest fibers contained in muscle cells
  • the contractile units of the muscle cell
31
Q

Thick and thin filaments

A

Overlapping thick and thin filaments create sarcomeres

32
Q

Types of sarcomeres

A
  • Z-line: zigzag shape, a dense disk that anchors actin filaments together (one sarcomere = Z-line to Z-line)
  • M-line: M-protein molecule in the middle of the sarcomere, anchors and stabilizes myosin filaments together
  • A-band: the segment that runs the entire length of the myosin filaments (“anisotropic band”) ONLY MYOSIN
  • I-band: the segment that includes the Z-disk and the ends of the actin filaments where they do not overlap the myosin filaments (“isotopic filaments”) ONLY ACTIN
  • H-band: the middle region of the myosin filament where they do not overlap the actin filament (“heller” = bright)
33
Q

Elastic filaments

A
  • composed of a protein called titan (connection)
  • anchor the myosin filaments to the Z-disk
  • believed to give myofibrils elasticity
34
Q

Dystrophin

A
  • a protein that holds the actin filaments to the sarcolemma
    - plays a significant tole in muscular dystrophy
35
Q

Motor unit

A
  • composed of a motor neuron and the skeletal muscle fibers innervated by the motor neurons atonal terminals
36
Q

Motor neuron

A
  • specialized type of nerve cells
  • connected to the sarcolemma of a muscle fiber at the folded motor endplate
37
Q

Neuromuscular junction (NMJ)

A
  • type of connection called a synapse and is characterized by a narrow gap or synaptic cleft, across with neurotransmitter molecules transit signals
38
Q

Acetylcholine (Ach)

A
  • a neurotransmitter, which is a release via vesicles into the synaptic cleft
  • diffuse across the microscopic gap to contact the sarcolemma of the adjacent muscle fiber
  • stimulating/signaling the T-tubules to “trigger” the SR release CA++
39
Q

Sliding filament theory

A
  • theory that explains how muscles contract to produce force
  • actin and myosin filaments within the sarcomeres of muscle fibers bind to create cross-bridges and slide past one another, creating a contraction
40
Q

Step by step sliding filament theory

A

1) an electric signal (action potential) down the motor neuron
2) stimulating the motor unit
3) Ach is release within the NMJ
4) depolarizing the sarcolemma
5) action potential travels down the t-tubule
6) stimulating the sarcoplasmic reticulum
7) releases Ca++ ions
8) Ca++ binds with troponin
9) displacing tropomyosin
10) allowing actin and myosin to form a cross-bridge
11) myosin pulls actin down the length of myosin
12) drawing the Z-line, closer to the M-line
- when this happens within sarcomeres the entire muscle belly can contract and shorten

41
Q

Cardiac and smooth muscles have special features

A
  • involuntary
  • able to contract entirely on their own in absence of nerve stimulation
  • cardiac muscle cells are joined by intercalated disks
    • have gap junctions allowing cells to electrically stimulates the next one
  • smooth muscle cells joined by gap junctions, allowing cells to activate each other
  • cardiac and smooth muscle cells spend to stimulation from autonomic nervous system, which can modify the degree of contraction
42
Q

Muscle fibers types

A

Type 1: slow twitch, oxidative, aerobic in nature, red in color, endurance type fibers
Type 2: fast-twitch, nonoxidative, anaerobic in nature, pink or white in color, white meat, can be separated into Type IIa (oxidative) and type IIx (glycotic), power type fibers
Type IIA: fast twitch, oxidative/glycolytic
Type IIX: fast twitch, glycolytic

43
Q

Muscle fibers

A
  • most skeletal muscle simultaneously contains all three types of fibers - but motor units only contain one type
  • this means there are actually Type I, IIA, and IIX motor units, not just muscle fibers
  • each fiber type has different structural, functional, and metabolic aspects
    • type 1: small motor unit, oxidative, slow contraction
    • type 2: large motor unit, glycolytic, fast contraction
44
Q

Hennemen’s size principle:

A
  • “under load, motor units re recruited from smallest to largest”
    • in practice, this means that slow-twitch, low-force, fatigue-resistant muscle fibers are activated before fast-twitch, high-force, less fatigue-resistant muscle fibers
45
Q

Muscle fiber type can be assessed in two ways:

A
  • muscle needle biopsy
  • nuclear magnetic resonance spectroscopy
    • taking a “snapshot” of the fibers
  • by counting the fibers we can estimate a % balance between the fast twitch and the slow twitch. We could also attempt to estimate the diameter of the fibers
46
Q

Fiber typing differences

A

The fast twitch to slow twitch ratio varies between muscles within individuals and between individuals
Highly dependent on genetics
Average Person:
- typically 50:50 between type 1 and type 2
- no difference between sex
- large variation between individuals

47
Q

Muscular dystrophy

A
  • genetic disease
  • modified dystrophy protein enable leakage of Ca++ into cells
  • extra Ca++ activates enzymes that destroy muscle proteins
  • muscle weakening and wasting
  • muscle mass is replaced with fibrous connective tissue
  • life expectancy is approximately 30 years
48
Q

Tetanus

A
  • infection of deep wound by bacteria, Clostridium tetani
  • bacteria produce tetanus toxin, which causes muscles to contract forcefully
  • death due to respiratory failure
  • preventable to tetanus vaccine
49
Q

Muscle cramps

A

Often caused by dehydration and ion imbalances

50
Q

Pulled muscles

A

Result from overstretching of a muscle, fibers then tear apart

51
Q

Fasciitis

A

Inflammation of the fascia
- Plantar fasciitis: sole of the foot

52
Q

What is the primary purpose of the Z-line? Of the M-line?

A

The z-lines primary purpose is to anchor actin
The m-lines primary purpose if to anchor myosin

53
Q

Why is calcium important for the body

A

Calcium initiates muscle contractions

Human Biology (25 decks)

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