muscle physiology

Question 1

Ca induced Ca release is unique to which type of muscle?

Answer 1

cardiac myocytes

Question 2

How does Ca enter cardaic cells?

Answer 2

L type channels

Question 3

How is contraction initiated in skeletal muscle?

Answer 3

Motor neuron releases Ach will depolarizes cell and leads to calcium outflix from SR

Question 4

How do cardiac myocytes increase contractility?

Answer 4

Allow more calcium in ‘increased calcium transient’

Question 5

how do non-dihydropyridine ca channel blockers work?

Answer 5

Block L type ca channels in heart

Question 6

How does the SNS increase activity in the heart?

Answer 6

• work via g proteins in cardiac myocytes
• increase caMP which activates PKA
• PKA phosphorylates Ca channels –> more Ca entry

Question 7

B1 receptors in the heart are linked to what?

Answer 7

Adenylyl cyclase

Question 8

Lusitropy meaning

Answer 8

rapid relaxation of heart (allows to rapidly relax and fill with blood to pump more out)

Question 9

Lusitropy MOA

Answer 9

Via beta receptors
Phospholambin iis regulatory protein that inhibits SERCA and when its phosphorylated by PKA it stops inhibiting SERCA and SERCA can take up calcium again

Question 10

How is contraction regulated in smooth muscle cells?

Answer 10

Myosin-light chain kinase phosporylates myosin -> contraction
Myosin-light chain phosphatase dephosphorylates myosin -> relaxation

Question 11

What activates myosin light chain kinase?

Answer 11

The Ca-calmodulin complex after Ca influxes through L–type Ca channels

Question 12

What activates myosin light chain phosphatase?

Answer 12

NO –> cGMP

Question 13

What inhibits myosin light chain kinase?

Answer 13

cAMP

Question 14

What is NO synthesized from?

Answer 14

arginine

Question 15

What increases the production of NO?

Answer 15

Binding of Acetylcholine, bradykinin to endothelial cells, which then produced NO which diffuses into smooth muscle cells which them make cGMP

Question 16

Nitroglycerine MOA

Answer 16

Converted to NO in SM cells

Question 17

Nitroprusside MOA

Answer 17

Donates NO in SM cells

Question 18

Gs protein effect on SM

Answer 18

Gs proteins are coupled to Adenylyl cyclase –> cAMP production –> inhibition of MLCK –>relaxation

Question 19

Gi effect on SM

Answer 19

Gi proteins inhibit Adenylyl cyclase activity –> decreased cAMP –> activation of MLCK –> contraction

Question 20

Gq effect on SM

Answer 20

Gq coupled to IP3 –> Ca increase –> contraction

Question 21

What senses the speed of stretch in muscles?

Answer 21

Muscle spindles - prevent overstretching

Question 22

What senses the tension in muscles?

Answer 22

Golgi tendon organs - promote muscle relaxation

Question 23

Type I muscle fibers are fast or slow, and red or white?

Answer 23

slow twitch, red

Question 24

type II muscle fibers are fast or slow and red or white?

Answer 24

fast twitch, white

Question 25

Characteristics for type I muscle fibers?

Answer 25

slow twitch and red because they have abundant mitochondria and myoglobin – good for endurance

Question 26

Characteristics for type II muscle fibers?

Answer 26

fast twitch and white because they have low mitochondria and myoglobin (increased anaerobic glycolysis) - good for weights/resistance