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BMSC 207 > BMSC 207 Muscles 1 > Flashcards

BMSC 207 Muscles 1 Flashcards

1
Q

Primary Function of ALL muscles

A

Generate Force
Body Movement
Maintenance of Posture
Respiration
Production of Body Heat
Communication
Constriction of Organs and Vessels
Heartbeat

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2
Q

Skeletal Muscles

A

Primarily Voluntary by Somatic motor neurons
Striated & Multinucleated

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3
Q

Cardiac Muscle

A

Primarily Involuntary: Spontaneous electrical activity
Can be altered by autonomic NS, hormones
Striated & Uninucleated

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4
Q

Smooth Muscle

A

Primarily Involuntary: Autonomic control, Spontaneous, Hormones, Paracrines or autocrines
Nonstriated & uninucleate

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5
Q

Smooth Muscles Provide mechanical control of:

A

Digestive tract
Urinary tract
Reproductive tract
Blood vessels
Airways

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6
Q

Skeletal Muscle Function

A

Usually Attached to Bones by tendons
Origin: Closest to trunk or to more stationary bone
Anatagonisic muscle group: Flexor-extensor pair
Flexor: brings bones together
Extensor: Moves bones away.

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7
Q

Differentiate different levels of organization of skeletal muscle

A

Skeletal muscle -> Muscle Fascicles -> Muscle Fibers -> Myofibrils -> Contractile Filaments (Myosin and Actin)

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8
Q

Myofilaments (Thin filaments)

A
  • F-Actin: Back bone of thin filaments, double stranded alpha helical polymer of g-actin molecules.
    Contains: binding site for think filaments (Myosin)
  • Tropomyosin: two identical alpha helices that coil around each other and sit in the two grooves formed by actin strands, regulates binding of myosin to actin.
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9
Q

Troponin complex

A

[1] troponin T (TnT): binds to a single molecule of tropomyosin
[2] troponin C (TnC): Ca2+ binding site
[3] troponin I (TnI): under resting conditions is bound to actin inhibiting contraction

Situated ~ every 7 actin molecules

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10
Q

Thick Filaments

A

Consists of a bundle of Myosin molecules
Myosin head contains a region for binding actin as well as a site for binding and hydrolyzing ATP (ATPase)
Regulatory light chain regulates ATPase activity of myosin
Essential light chain stabilizes myosin head

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11
Q

Titin

A

A very large protein extending from M line to Z line, appears to be involved in stabilization of Thick filaments and the elastic recoil behavior of muscle.

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12
Q

Nebulin

A

Large protein that interacts with the thin filaments, believed to regulate the length of thin filaments and contribute to the structural integrity of myofibrils

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13
Q

Sarcomere

A

Z-disk - Zigzag protein structure that is the attachment site for the thin filaments
I Bands - Lightest band of sarcomere, region occupied only by thin filaments.
A Bands - Darkest band of sarcomere, encompasses entire length of the thick filament, including very dark area where thin and thick filaments overlap
H Zone - Central region of A band, consists only of Thick Filaments.
M Line - Proteins form the attachment site for the thick filaments, equivalent to Z disk for thin filaments

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14
Q

The Sliding FIlament Theory

A

The sarcomere shortens during contraction. As contraction takes place, Actin and Myosin do not change length but slide past another.

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15
Q

Muscle Tension

A

The force generated by a contracting skeletal muscle

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16
Q

Brain regions involved in voluntary movement

A

Primary motor cortex:
Basal ganglia
Premotor cortex (motor association)
Thalamus
Cerebellum
Midbrain

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16
Q

Initiation of skeletal muscle contraction

A

Neuromuscular junction: Point of synaptic contact between somatic motor neuron and Individual muscle fibre.

Excitation-Contraction coupling: an action potential initiated in the skeletal muscle fibre results in an increase in Intracellular (sarcoplasmic) Ca2+

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17
Q

Corticospinal Tract

A

Descending tract (ventral and interior lateral white matter)

Controls voluntary motor functions (moving limbs)

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18
Q

Upper motor neuron

A

Brain to brainstem or spinal cord

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19
Q

Alpha (lower) motor neuron

A

Spinal cord to muscle

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20
Q

Motor Unit

A

A single motor neuron and all the muscle fibres it innervates.

21
Q

Neuromuscular Junction

A

The area where the lower motor neuron makes synaptic contact with the muscle fibre.

22
Q

________ muscle fibres receives input from _______ motor neurons

A

1 muscle fiber receives input from 1 motor neuron

23
Q

_____ Motor neurons receives input from ______ Muscle fibres

A

1 motor neuron receives input from LOTS of muscle fibers

24
Q

Alpha- motor neuron

A

Large
Myelinated 15-120 m/sec
All muscle fibers respond simultaneously
<10 delicate precise work
>100’s for powerful, less precise contractions

25
Q

Amyotrophic Lateral Sclerosis (ALS)

A

Neurodegenerative motor neuron disease,
Upper and/or lower motor neurons degenerate leading to muscle atrophy and weakness from disuse
10% genetically

26
Q

3 Components of Neuromuscular Junction

A
  1. Presynaptic motor neuron filled with synaptic vesicles
  2. Synaptic Cleft
  3. Postsynaptic membrane of the skeletal muscle fiber
27
Q

Motor End Plate

A

Region of sarcolemma at the Neuromuscular junction

28
Q

Junctional folds

A

On sarcolemma increase surface area.

29
Q

Motor neuron vesicles contain _______?

A

Acetylcholine

30
Q

Muscle sarcolemma contain _____?

A

Nicotinic acetylcholine receptors

31
Q

Nicotinic Acetylcholine Receptors

A

They are found in sarcolemma of muscle fibers.
Member of Cys-loop receptor family of ligand gated ion channels;
Classified as a MONOVALENT CATION CHANNEL.

32
Q

Stages to Ceasing Neural Transmission

A
  1. APs stop firing from alpha motor neuron
  2. Acetylcholine from synaptic cleft will diffuse away or be broken down to acetate and choline by the enzyme acetylcholinesterase
  3. Choline is transported back to the motor neuron
  4. it is combined with Acetyl CoA produced from mitochondria by the enzyme choline acetyltransferase to make Acetylcholine
33
Q

Action potentials spread from the sarcolemma to ________?

A

Interior of muscle fibers along the transverse tubule network

34
Q

Sarcoplasmic Reticulum

A

Specialized Ca2+ storaage organelles.
They are strategically organized with the T-Tubules

35
Q

Excitation-contraction coupling

A
  • The intracellular signal that contracts in all muscle types is a rise in intracellular calcium [Ca2+]
  • Ca2+ can enter the sarcoplasm from the extracellular space via voltage gated Ca2+ channels
    or
  • It can be released into the sarcoplasm from the intracellular Ca2+ storage reservoir of the SR
  • The process which electrical excitation of the surface membrane triggers an increase of [Ca2+] in muscle.
36
Q

DHP Receptor

A

L-type Ca2+ channel
-Voltage sensitive

37
Q

RyR

A

Ryanodine Receptor
-Ca2+ release channel on SR

38
Q

Initiation of Muscle Action Potential

A
  1. Somatic motor neuron release ACh at neuromuscular junction
  2. Net entry of Na+ through ACh receptor-channel initiates a muscle action potential
39
Q

Excitation-Contraction Coupling

A

3.Action Potential in t-tubule alters conformation of DHP receptor
4. DHP receptor opens RyR Ca2+ release channels in sarcoplasmic reticulum, and Ca2+ enters Cytoplasm

40
Q

Cross-bridge cycle

A
  1. ATP binds to myosin, Myosin releases Actin.
  2. Myosin hydrolyzes ATP. Energy from ATP rotates the myosin head to the cocked position. myosin binds weakly to actin (Myosin has ADP and Pi)
  3. Power stroke begins when Pi is released (Release of Pi strengthens bond between actin and Myosin)
  4. Myosin releases ADP at the end of the power stroke.
    THEN IT CYCLES BACK
41
Q

Does the sarcomere shorten during Contraction?

A

Yes but Myosin and Actin dont.

42
Q

Termination of contraction requires removal of___?

A

Ca2+
Ca2+ can be removed to the extracellular space.
Na-Ca exchanger or by the Ca2+ pump
Would eventually deplete the cell of any Ca2+ leaving the SR empty.

43
Q

Sliding Filament theory

A

The sarcomere shortens during contraction
H zone and I band both shorten
A band remains constant

44
Q

Rigor Mortis

A

Development of Rigid muscle several hours after death.
Ca2+ leaks into sarcoplasm and binds troponin

45
Q

ATP production stops:

A
  • Ca2+ cannot be removed (SERCA pump is ATP powered)
  • ATP needed to release myosin head from actin
  • Remains latched cross bridge formation until muscles begin to deteriorate
46
Q

Muscles need a steady supply of ATP to function.
ATP needs for: _____?

A

Myosin ATPase (contraction)
Ca2+ ATPase: SERCA (Relaxation)
Na+/K+ ATPase (after AP in muscle fibre)

47
Q

Anaerobic Metabolism

A

Absence of Oxygen and Pyruvate is further converted to lactate
Takes place in Sarcoplasm

48
Q

Oxidative (aerobic) Metabolism

A

Oxygen and Mitochondria are present

49
Q

4 sources

A

ATP
Creatine Phosphate
Aerobic metabolism
Anaerobic Metabolism

50
Q

When oxygen is available we rely on _______?

A

Carbs and Fats

BMSC 207 (5 decks)

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