Muscle Test

Question 1

Define myology

Answer 1

study of muscles

Question 2

Know the 3 types of muscle tissue and all of their characteristics

Answer 2

• Cardiac- found in heart, has some striations, involuntary, pumps blood, able to regenerate sometimes
• Smooth- not striated, involuntary, found inside hollow organs and blood vessels, high capability of regeneration, function depends on location
• Skeletal- most striated, voluntary, attach to bones, function- help with movement, have limited regeneration capacity (because most cells are post mitotic)

Question 3

Total Body Weight

Answer 3

Total body weight: 40-50%

Question 4

5 functions

Answer 4

Produce heat by contractions
Produces movement
Regulates organ volume
Stabilizes body position
Moves substances through body

Question 5

Know what type of tissue makes up muscle.

Answer 5

Connective tissue, areolar CT, adipose CT, dense irregular CT, dense regular CT (in collagen fibers)

Question 6

Define all parts of a muscle and know the tissues that make them up if we discussed it. Ex: fascia, epimysium, etc.

Answer 6

• Fascia- a sheet of CT found beneath the skin and around muscles and organs
  
  • Superficial: right under the skin: made up of areolar and adipose CT
  • Deep: holds muscle together: separates into functional groups (bundles): dense irregular CT
• Epimysium- covers entire muscle cell
• Perimysium- surrounds bundles of 10-100 muscle fibers called fascicles
• Endomysium- wraps around each individual muscle fiber
• Tendon- connects muscle to bone
• Collagen fiber: cord of dense reg. CT

Question 7

Muscle fiber

Answer 7

100s to 1000s make up skeletal muscles, arranged parallel to each other

Question 8

Sarcolemma

Answer 8

plasma membrane around each muscle fiber

Question 9

Transverse (T) tubules-

Answer 9

tunnel-like extensions of sarcolemma that pass through muscle fibers from side to side

Question 10

Sarcoplasm

Answer 10

muscle fibers cytoplasm, contains many mitochondria for ATP during muscle contractions

Question 11

Sarcoplasmic reticulum

Answer 11

network of fluid filled membrane enclosed tubules
- Store Ca ions for contraction
- Similar to smooth ER

Question 12

Myoglobin

Answer 12

red pigment in sarcoplasm
- Gives color to skeletal muscle
- Stores O2 until used by mitochondria

Question 13

Myofibrils

Answer 13

cylinder structure found in inside muscle fibers

Question 14

Filaments

Answer 14

overlap in specific patterns to form sarcomeres

Question 15

Sarcomere

Answer 15

basic functional unit of striated muscle fiber

Question 16

Z disc

Answer 16

zig zagging zones on dense proteins; separates sarcomeres from each other

Question 16

A Band

Answer 16

dark area in sarcomere

Question 17

H zone-

Answer 17

narrow part of thick filament

Question 18

I band

Answer 18

light are on each side of A band

Question 19

Thick filaments

Answer 19

made up of protein myosin, looks like 2 golf clubs twisted together, myosin heads and tails

Question 20

Thin filaments

Answer 20

made up of protein actin; actin molecules join to form an actin filament- twisted into a helix
- Brown spots: myosin binding site
- 2 other proteins- tropomyosin and troponin: cover up myosin binding sites when muscle relaxes

Question 21

Know what a motor unit is and everything that makes it up.

Answer 21

• Motor unit- 1 neuron + muscle cells stimulated
  
  • Axon- extension of neuron
  • Axon terminal- end of axon
  • Synaptic cleft- space between neuron and muscle fiber
  • Acetylcholine (ACh)- neurotransmitter
  • Motor neuron- 1 nerve cell

Question 22

Define neuromuscular junction and everything that makes it up.

Answer 22

• Neuromuscular junction- where axon terminal meets muscle fiber
  - Consists of axon terminals resting in folds of sarcolemma of a muscle fiber
  
  • Presynaptic terminal- motor neuron axon terminal
    - Postsynaptic membrane/motor end plate- sarcolemma of muscle fiber that’s stimulated
  • Synaptic cleft- between presynaptic terminal and muscle fiber

Question 23

Define cross-bridge

Answer 23

• when myosin heads bind to active sites on actin
• Cross-bridge cycling- during a single contraction, each myosin molecule undergoes repeated cycles of:
  
  • Cross-bridge formation
  • Movement (actin slides over myosin myofilament)
  • Release
  • Return to original position

Question 24

Explain how the sliding filament model works

Answer 24

During contraction, thin filaments slide past thick ones Myosin heads latch onto active sites– called cross bridge Attachments made and broken propel the thin filaments which then slide

Question 26

Explain the roles of Calcium and acetylcholine in muscle contraction and relaxation

Answer 26

Calcium Ca2+ moves back into sarcoplasmic reticulum by active transport Requires energy Ca2+ moves away from troponin- tropomyosin complex Complex re-establishes its position and blocks active sites of actin molecule

Question 26

Know what an action potential is

Answer 26

Action potential- electrical signals Nervous system controls muscle contractions through action potentials Travel from brain/spinal cord along axons to stimulate muscle fibers

Question 26

Explain how depolarization and repolarization work, including hyperpolarization.

Answer 26

- Depolarization- inside of plasma membrane becomes more positive - Na+ gates open - Na+ enters cell - If change in charge reachers threshold, action potential triggered - Repolarization- return of resting membrane potential - Na+ gates close - Membrane potential drops lower than its original resting potential then rebounds - This is because K+ gates open, K+ leaks out, but then Na/K pump restores resting membrane potential

Question 26

The the steps in muscle contraction

Answer 26

1. Action potential travels down sarcolemma along T-tubules 2. Calcium released from sarcoplasmic reticulum 3. Calcium binds to troponin which changes shape then myosin binding sites are exposed on actin 4.Myosin cross– bridge forms with actin 5.Myosin head pivots and pulls actin filament to m line 6.ATP attaches to myosin and cross bridge detaches 7.Myosin can be reactivated (keep contracting)

Question 26

Be able to explain the membrane potential difference in a cell

Answer 26

Resting membrane potential- membrane voltage difference across plasma membrane Inside cell is more negative, accumulation of large protein molecules; more K+ on inside than outside; some K+ leaks out (-70 to -90 mV) Outside cell more positive; more K+ Na+/K+ pump maintains this ion difference: pumps out Na+, moves in K+ Must exist for action potential to occur

Question 26

Know the steps of the excitation of a muscle cell

Answer 26

1. Activation potential travels down axon and arrives at NMJ 2. Release of acetylcholine into synaptic cleft 3. ACh diffuses across cleft and attaches to ACh receptors on sarcolemma of muscle fibers 4. Rush of Na+ into sarcoplasm produces action potential in sarcolemma 5. ACh broken down

Question 26

Explain why a muscle relaxes.

Answer 26

- Ca2+ moves back to sarcoplasmic reticulum by active transport (requires energy) - Ca2+ moves away from troponin to