skeletal muscle function

Question 1

hyperkalemia

Answer 1

high amount of k+ in the blood

prevents proper repolarization

Question 2

what is HYPP aka impressive syndrome

Answer 2

Mutation in Na+ channel
Disrupts membrane voltage
triggered by stress and kyperkalemia

Question 3

Myasthenia Gravis

Answer 3

an autoimmune disease that attacks ACh receptors in the NMJ

• no muscle contraction
• weakness

Question 4

what is tensilon test?

Answer 4

its a test to diagnose myasthenia gravis

• works by inhibiting acetylcholinesterase
• accumulated ACh prolongs muscle stimulation and increases muscle strength temporarily

Question 5

muscle twitch definition

Answer 5

mechanical response resulting from a single AP

Question 6

speed of twitch depends on

Answer 6

muscle fiber type and load

Question 7

isometric twitch

Answer 7

muscle contraction- no change in length

Question 8

concentric twitch

Answer 8

subtype of isotonic twitch

-muscle shortens during contraction

Question 9

eccentric twitch

Answer 9

subtype of isotonic twitch

-muscle lengthening during contraction

Question 10

Force generated in muscle fiber depends on

Answer 10

• exposed myosin-binding site
• # of crossbridges

more crossbridges= more force

Question 11

how could a muscle cell increase # of crossbridges?

Answer 11

increase AP frequency

Question 12

Hypertrophy

Answer 12

increase the size of the muscle fiber/cell - this can be achieved through training

Question 13

hyperplasia ?

Answer 13

this is an increasing number of muscle cells/fiber
not common in mature muscle

maybe in pathology?

Question 14

what does myostatin do?

Answer 14

inhibits differentiation of myoblast into muscle fibers

• prevents hyperplasia
• controls down regulation of new myofibrils

Question 15

what is active tension ?

Answer 15

contraction due to myosin and actin interactions

Question 16

what is series elastic component of passive tension

Answer 16

tendons for whole muscles or titan for sarcomere

Question 17

what is parallel elastic component of passive tension

Answer 17

plasma membrane or CT

Question 18

what happens to passive and active tension when a muscle fiber is stretched out?

Answer 18

decrease active tension

increase passive tension

Question 19

what activates force production ?

Answer 19

Ca2+

Question 20

factors affecting velocity of contraction

Answer 20

1. load
2. muscle fiber type
3. muscle fiber length

Question 21

magnitude of load

Answer 21

bigger load- slower contraction

load influences kinetics of crossbridging

Question 22

muscle fiber length

Answer 22

aka #of sarcomere

long muscle fibers have a larger shortening range and faster shortening rates

Question 23

muscle fiber type

Answer 23

the velocity of contraction is dependent on myosin ATPase activity

Question 24

since ATP has to be replenished- where does it come from?

Answer 24

1. creatine phosphatase
2. Carbs
3. fatty acids and triglycerides

Question 25

creatine phosphate

Answer 25

provides ATP to skeletal muscles

dephosphorylation of creatine phosphate into creatine

this reaction is reversible- it can also go from creatine to creatine phosphate

Question 26

carbohydrates for ATP replenishment in skeletal muscles

Answer 26

provide a quick source of energy

muscle cells store glycogen

Question 27

what enzyme do skeletal muscles lack ?

Answer 27

glucose-6- phosphatase

Question 28

what is significant about glucose 6-phosphatase in relation to skeletal muscles

Answer 28

• not present in skeletal muscles
  -skeletal muscles can not make glucose from their stored energy (glycogen)
  skeletal muscle do not contribute to regulating blood glucose

all glycogen storage is used for its own need!

Question 29

how do muscle cells uptake glucose?

Answer 29

insulin receptors, exercise ( muscle contraction removes glucose from blood)

exercising allows uptake of glucose- this is insulin-independent

Question 30

fatty acids used as energy source of ATP in skeletal muscle

Answer 30

-provides more energy than one molecule of glucose
source: fatty acids in blood or stored trygliceride
used during prolonged exercise

Question 31

can a muscle fiber increase # of sarcomeres?

Answer 31

yes, during eccentric contraction. where the muscle is being stretched

Question 32

how are skeletal muscles classified?

Answer 32

maximum velocity

primary pathway to produce ATP

Question 33

what are 3 major skeletal muscle fiber types

Answer 33

slow oxidative I
fast oxidative-glycolytic IIA
fast glycolytic IIB

Question 34

maximum velocity of contraction is dependent on

Answer 34

rate of myosin ATPase activity and maybe myosin isoform?

Question 35

how do glycolytic fibers generate ATP

Answer 35

glycolysis

anaerobic

Question 36

how do oxidative fiber generate ATP?

Answer 36

through oxidative phosphorylation

aerobic

Question 37

oxidative fibers characteristics

Answer 37

have more mitochondria than glycolytic fibers
darker- b/c of myoglobin
smaller- allows for accessibility to blood

Question 38

Can primary mode of ATP production be altered?

Answer 38

Yes! through training/exercise

Question 39

can slow oxidative and fast glycolytic fibers alternate their mode of ATP generation?

Answer 39

YES- through training the pathway can shift to the other type

Question 40

can a muscle change from fast to slow twitch with training?

Answer 40

No. B/C slow and fast-twitch fibers are dependent on myosin isoform

myosin isoforms are genetically influenced- so it wont change
EXCEPTION: a muscle contain both types of myosin isoforms

Question 41

what pathway do fast twitch fiber primarily use

Answer 41

primarily use anaerobic pathway to generate ATP

but could use oxidative pathway

Question 42

fast twitch

Answer 42

myosin isoform and ATPase is fast acting
its glycolytic because it primarily uses anaerobic processes

fewer mitochondria- bulkier, lighter, more glycogen