Lecture 14: Muscle Physiology

Question 1

3 phases of muscle contraction

Answer 1

1. ) latent period
2. ) period of contraction
3. ) period of relaxation

Question 2

latent period

Answer 2

first few milliseconds (exictiation-contraction-coupling)

- time it takes before the AP in the muscle and actin-myosin reaction

Question 3

Period of contraction

Answer 3

cross bridge cycling, tension increases

- when the muscle is actually responding

Question 4

period of relaxation

Answer 4

calcium transported back into SR

- cross bridge cycling ends, tension decreases

Question 5

what is an isotonic contraction

Answer 5

muscle contracts (produces constant tension) and the length of the muscle gets smaller

ex. ) lifting weights
- saromere shortens , muscle length shortens

Question 6

isometric muscle contracts

Answer 6

produces tension but the length of the muscle does not change (constant)

ex) trying to lift something that is too heavy
- sarcomere shortens. length doesn’t change

Question 7

properties of muscle cells that influence tension

Answer 7

1. ) muscle fiber diameter
   
   • size of the muscle fiber—> exercise
2. ) recruitment
   
   • number of motor units
3. ) summation (and tetany)
   
   • frequency of AP in a motor neuron
4. ) length- tension
   
   • overlap of actin and myosin

Question 8

muscle fiber diameter

Answer 8

increased diameter= more actin and myosin can generate more force

Question 9

recruitment

Answer 9

activate more motor units–> generate more force

• more motor units–> more muscle fibers= stronger contraction

Question 10

summation

Answer 10

increasing frequency of action potentials in motor neurons cause increase muscle contraction

Question 11

3 different types of summation

Answer 11

• treppe
• summation
• tetany

Question 12

treppe

Answer 12

slow frequency of action potentials, stronger independent–> muscle contractions

caused by
( warming of the muscle fibers, increased Ca)

Question 13

tentany

Answer 13

high frequency of stimulation –> Ca2+ levels are high in the cell so the muscle remains contracted (cant move)
- saromere doesn’t return to normal strength

caused by neurotoxin

Question 14

how does length tension relationship increase muscle strength

Answer 14

the tension a muscle can produce is determined by the length of the muscle —> degree of overlap between actin and myosin

Question 15

three ways that muscles get ATP

Answer 15

1. ) direct phosphorylation: fast way to making ATP
2. ) aerobic metabolism: process of cell metabolism (requires oxygen)
3. ) anaerobic metabolism: just glycoloysis—> produces lactic acid

Question 16

why do muscles need ATP

Answer 16

• myosin can interact with actin

- myosin can change its shape

Question 17

what form of glucose is formed in muscle cells

Answer 17

glycolysis

Question 18

how can muscles store oxygen

Answer 18

through myoglobin

• pigment found in muscles, what gives the muscles its reddish color
• binds oxygen in muscles

Question 19

muscle fatigue

Answer 19

muscles feel week/ overuse

• causes is
  lactic acid build up, depletion of ACh, depletion of energy reserves

Question 20

why do skeletal muscles have different contraction speeds

Answer 20

due to the type of fibers present (fast or slow)

Question 21

muscle fiber types

Answer 21

1. ) slow oxidation: slow contractions, (requires oxygen)
2. ) fast oxidation: medium contractions (requires oxygen)
3. ) fast glycolytic–> fast contractions no oxygen, fatigues easily