ch 10 muscle physiology

Question 1

types of muscles

Answer 1

• skeletal: voluntary, striated
• cardiac: involuntary, striated
• smooth: involuntary

Question 2

skeletal muscles structure

Answer 2

• muscle: muscle body bc its made of numerous fascicles held together by connective tissue. each fascicles contains several muscle fibers
• muscle fiber is a single muscle cell that contains numerous nuclei bc muscle cells make up a lot of protein nucleus directs protein synthesis
• muscle cells do not divide. more myofibrils are made. this is why gym people drink protein shakes bc protein is needed to make myofibrils
• muscle cell: connective tissue –> fascicle –> fiber
• multiple protein filaments: make up a muscle cell are called myofibrils

Question 3

skeletal muscle structure

Answer 3

• one muscle fiber = one cell
• a cell can have more than one mucleus bc the nucleus does not define a cell
• a cell membrane defines a cell: one membrane = single cell
• one muscle fiber has many nuclei: multinucleate (several nuclei)
• muscle fibers contain myofibrils - rod like elements that contain contractile machinery

Question 4

skeletal muscle fiber structure

Answer 4

• axon of motor neuron: tells muscle to contract
• sarcoplasmic reticulum (SR): SR is filled with calcium (sarco = muscle)
• t tubule: part of muscle cell membrane that extends deep into muscle fiber
• neuromuscular junction; where a motor neuron communicates with muscle cell
• motor end plate: part of skeletal muscle cell mem where all acetylcholine receptors are found
• diffusion only happens over short distances so, receptors need to be concentrated in one place for neurotransmitters to be able to bind to them

Question 5

neuromuscular junction

Answer 5

• the most well-studied & well-understood synapse on earth
• synapse between a motor neuron and muscle cell
• acetylcholine binding to nicotinic receptor opens the ion channel that is permeable to both Na and K so, Na goes in and K goes out
  FINISH

Question 6

sarcomere components

Answer 6

slide 8-10

Question 7

sarcomere components

Answer 7

• thin filaments: made up of two strands of F actin that form double helix
• thick filaments: made up of myosin dimers bound together at tails, binding sites on heads (cross bridges) for actin, ATPase site
• tropomyosin: extends along thin filaments, masks myosin binding site in absence of calcium
• troponin: calcium brining site, actin binding site, tropomyosin binding site

Question 8

steps in muscle contraction (excitation-contraction coupling)

Answer 8

1. motor neuron AP
2. end plate potential (excitation)
3. increase in muscle cell calcium levels
4. troponin and tropomyosin conformational changes
5. crossbridge cycling –> sliding filaments (contraction)

Question 9

review slide 13-16

Answer 9

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Question 10

how is muscle contraction terminated

Answer 10

• motor neuron input terminates
• EPPs terminate
• high myoplasmic calcium concentration shuts SR calcium channels
• active calcium uptake through SERCA pumps on SR
• calcium dissociated from troponin
• tropomyosin covers myosin binding sites on actin

Question 11

the twitch

Answer 11

• the mechanical response or change in force/tension (measured in grams) of an individual muscle fiber, motor unit, or whole muscle to a single action potential

Question 12

isometric vs isotonic twitches

Answer 12

• isotonic twitch: muscle-generated force causes muscle shortening and lifts a load (load must be less than or equal to muscle tension)
• isometric twitch: muscle generates force but does not shorten (load/force opposing muscle shortening greater than muscle tension)

Question 13

slow twitch vs fast twitch fibers

Answer 13

• slow twitch: contain slow myosin, hydrolyses ATP to ADP and P slower, myosin head cocking slower)
• fast twitch: contain fast myosin, hydrolyzes ATP to ADP and P faster, myosin head cocking faster)
• skeletal muscles can contain slow twitch fibers

Question 14

glycolytic vs oxidative fibers

Answer 14

• glycolytics (anaerobic): generates more ATP through glycolysis:
• high cytosolic concentration of glycolysis enzymes
• contain few mitochondria
• large diameter
• lighter in color
• oxidative (aerobic): generate more ATP through Oxidative phosphorylation:
• low concentration of glycolysis enzymes
• contain lots of mitochondria
• possess myoglobin (oxygen storage molecules)
• small diameter (surrounded by capillaries)
• darker in color

Question 15

types of skeletal muscle fibers and exercise

Answer 15

• low intensity exercise:
• increases oxidative capacity
• increases size and # of mitochondria
• decrease in fiber diameter
• increase in # of capillaries surrounding fibers
  conversion of some