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A and P Exam 2 > muscles > Flashcards

muscles Flashcards

1
Q

Types of Muscle

A
  • Skeletal muscle
  • Cardiac muscle
  • Smooth muscle
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2
Q

Skeletal muscle tissue

A
  • attached to bones and skin
  • striated
  • voluntary
  • powerful
  • multinucleate
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3
Q

Cardiac muscle tissue

A
  • only in heart
  • striated
  • involuntary
  • uni or binucleate
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4
Q

Smooth muscle tissue

A

in walls of hollow organs(stomach, urinary bladder, airways

  • not striated
  • not uninucleate
  • involuntary
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5
Q

Common Features

A
  • Elongated cells
  • myofilaments
  • —actin
  • –myosin
  • Terminology
  • –myo and sacro
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6
Q

Special characteristics of muscle

A
  • Excitability
  • –ability to receive and respond to stimuli
  • Contractility: ability to shorten when stimulated
  • extensibility: ability to be stretched
  • Extensibility: ability to be stretched
  • Elasticity: ability to recoil to resting length
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7
Q

Muscle Functions

A
  1. Movement of bones or fluids (e.g. blood)
  2. Maintaining posture and body position
  3. Stabilizing joints
  4. Heat generation (especially skeletal muscle)
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8
Q

How many arteries and nerves are in each muscle?

A

Each muscle is served by one artery, one nerve, and one or more veins

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9
Q

What is connective tissue sheaths called?

PICTURE BECCA

A
  • Epimysium:
  • —dense regular connective tissue surrounding entire muscle (groups of perimysium)
  • Perimysium
  • —fibrous connective tissue surrounding fascicles (groups of muscle fibers)groups of endomysium
  • Endomysium: fine areolar connective tissue surrounding each muscle fiber
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10
Q

Muscles attach 2 ways. What are they?

PICTURE 9.1

A
  • Directly
  • —epimysium of muscle is fused to periosteum of bone or perichondrium of cartilage
  • Indirectly
  • —connective tissue wrappings extend beyond the muscle as a replica tendon or sheetlike aponeurosis
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11
Q

What is Sarcolemma?

A

plasma membrane surface

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12
Q

What is sarcoplasm?

A

cytoplasm of muscle cells

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13
Q

What is myofibrils?

A

contractile elements of skeletal muscle

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14
Q

What is in s skeletal muscle fiber (cell)

A
  • cylindrical cell 10 to 100 in diameter up to 30 cm long
  • multiple peripheral nuclei
  • many mitochondria
  • numerous glycosomes for glycogen storage and myoglobin for 02 storage
  • also contain highly specialized organelles: myofibrils, sarcoplasmic reticulum, and T tubules
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15
Q

Myofibrils

PICTURE OF Myofibril

A
  • Densely packed, rodlike elements
  • –80%of cell volume
  • Exhibit striations: perfectly aligned repeating series of dark A bands and light I bands
  • Composed of contractile proteins
  • —Thick filaments - myosin
  • —Thin filaments - actin
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16
Q

Sarcomere

A
  • Smallest contractile unit (functional unit) of muscle fiber
  • Region of myofibril between two successive Z discs
  • Composed of thick and thin myofilaments made of contractile proteins
17
Q

Features of a Sarcomere

PICTURE OF A SARCOMERE

A
  • Thick filaments: run the entire length of A band
  • Thin filaments: run the length of I band and partway into the A band
  • Z disc: coin-shaped sheet of proteins that anchors the thin filaments and connects myofibrils to one another
  • H zone: lighter mid region where filaments do NOT overlap
  • M line: line of protein myosin that holds adjacent thick filaments together
18
Q

Ultrastructure of thick filament

A

Composed of the protein myosin

  • –1. myosin tail forms central part of dark band
  • –2. myosin heads contain:
  • —–binding sites for actin of thin filaments
  • —–during contraction forms a cross bridge with actin
  • —-binding sites for ATP
  • —-ATPase enzymes
19
Q

Regulatory Proteins of Actin

A
  1. Tropomyosin

2. Troponin - polypeptide complex

20
Q

What does tropomyosin do?

A
  • Spirals around actin

- Block myosin head binding sites during relaxed state

21
Q

What is troponin?

A
  • binds Ca2
  • binds tropomyosin (TnT)
  • Inhibitory protein that binds actin (Tnl)
22
Q

Elastic filament

PICTURE 9.3

A
  • composed of protein Titin
  • Extends from Z disk to the run within the thick filament to the M line
  • Helps to resist excessive stretching
23
Q

Intracellular tubules in muscles

A
  • sarcoplasmic reticulum

- T-tubules

24
Q

Sarcoplasmic Reticulum (SR)

A
  • Network of smooth endoplasmic reticulum surrounding each myofibril
  • Pairs of terminal cistern form perpendicular cross channels
  • Stores Ca2+
  • Functions in the regulation of intracellular Ca2+levels
25
Q

T Tubules

PICTURE OF TUBULES WITH SARCOLEMMA

A
  • Continuous with the sarcolemma
  • Penetrate the cell’s interior at each A band - I band junction
  • Associate with the paired terminal cistern to form triads that encircle each sarcomere
26
Q

Triad Relationship

A
  • T tubules conduct impulses deep into muscle fiber
  • Integral proteins protrude into the inter membrane space from T tubule and SR cisternae membranes
  • T tubule proteins: voltage sensors
  • SR foot proteins: gated channels that regulate Ca2+ release from the SR cisternae
27
Q

Contraction

A
  • The generation of force
  • Does not necessarily cause shortening
  • Shortening occurs when tension generated by cross bridges on the thin filaments exceed forces opposing shortening
28
Q

What is the sliding filament model of contraction?

PICTURE 9.6

A

States that during contraction, the thin filaments slide past the thick filaments. Overlap between myofilaments increases and the sarcomere shortens

  • –in the relaxed state, thin and thick filaments overlap only slightly
  • –during contraction, myosin heads bind to actin, detach, and bind again, to propel the thin filaments toward the M line and the H zone to shorten as well as each sarcomere
29
Q

Events at the neuromuscular junction

A
  • Skeletal muscles are stimulated by somatic motor neurons
  • Axons of motor neurons travel from the central nervous system via nerves to skeletal muscles
  • Each axon forms several branches as it enters a muscle
  • Each axon ending forms a neuromuscular junction with a single muscle fiber
30
Q

What is in the Neuromuscular Junction

A
  • synaptic cleft-gell filled space that separates axon terminal and muscle fiber
  • synaptic vesicles of axon terminal contain the neurotransmitter acetylcholine (ACh)
  • Junctional worlds of the sarcolemma contain ACh receptors
31
Q

Events at the Neuromuscular Junction

PICTURE 9.8

A
  • Nerve impulses arrive at axon terminal
  • ACh is released and binds with receptors on the sarcolemma
  • Electrical events lead to the generation of the action potential
32
Q

Destruction of ACh

A
  • ACh effects are quickly terminated by enzyme acetychonineterase
  • Prevents continued muscle fiber contraction in the absence of additional stimulation
33
Q

Events in generation of action potential

A
  1. local depolarization (end plate potential)
  2. Generation and propagation of an action potential
  3. Repolarization
34
Q

What is Local depolarization?

A
  • ACh binding opens chemically (ligand) gated ion channels
  • Simulataneous diffusion of Na+ inward and K+ outward
  • More NA+ diffuses, so the interior of the sarcolemma becomes less negative
  • Local depolarization - end plate potential
35
Q

Events in Generation of Action Potential

A
  • Local depolarization wave continues to spread, changing permeability of the sarcolemma
  • Voltage-regulated Na+ channels open in adjacent patch, causing it to depolarize to threshold

A and P Exam 2 (3 decks)

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