Cardiac Muscle Physiology

Question 1

Is cardiac muscle striated??

How does cardiac muscle function as a syncytium?

Answer 1

DUHH!!

• A single depolarizing stimulus results in contraction of the entire myocardium.

Question 2

In Cardiac muscle the SR is more ___, it has a ___, located at the ___ line. The t-tubules are much ___ in cardiac tissue.

Answer 2

1) sparse (less developed)
2) Diad, Z line (A-I band in skel.)
4) larger

Question 3

Name the Receptors in the Sarcolema, on the SR?

Answer 3

1) Dihydropyridine (DHPR) - Cal. (L)

2) Ryanodine (RYR)

Question 4

Explain excitation coupling in each muscle type?

Answer 4

Cardiac - (Voltage Dependent Calcium Release)

Skeletal - Cal. binds DHPR, which activates RYR (CICR)

Question 5

Name the pumps that re-sequester Ca++ into SR, and Extracellular space

Answer 5

1) Ca++ pump; SERCA –> SR (think SER_ like sarcoplasmic)

2) Na-Ca (atpase) Pump
& Ca++

Question 6

Skeletal muscle operates at peak of length tension curve. Cardiac tissue does not. What does this allow? what is it called

Answer 6

Allows for increased force when more blood enters ventricle and stretches c. muscles further – Franks Sterling Effect

Question 7

Define:

Pre-Load & Post-Load

Answer 7

Pre-Load: blood F on ventricles

After-Load: Resistance ventricles must overcome.

Question 8

Contractility (ionotropic) is a function of ______,

Answer 8

cross bridge cycling.

more cycling = more contraction

Question 9

How molecules (3) affect contractility?

Catecholamines

Answer 9

Catecholamines (E, NE)
Ca++ Blockers
Cardiac Glycosidases

Question 10

How does __ affect contractility?

Catecholamines

Answer 10

E, NE, increase Ca++ influx

Question 11

How does __ affect contractility?

Catecholamines
Cardiac Glycosidases
Ca++ Blockers

Answer 11

Inhibit Na/K pump, increasing intracellular Na; Na-Ca pump reverses to remove Na, increasing intracellular Ca++. They bind to RyR, releasing more Ca++

Question 12

What physical/properties work simultaniously to determine contractility

Answer 12

increase or decrease in force due to stretching (SL) & amount of Ca++ released into myoplasm

Question 13

In the Ventricular Pressure vs Time Graph, the slope gives you what value?

Answer 13

Contractility - closer to y axis means higer

Question 14

What two sympathetic effects shortens contraction or action potential

Answer 14

1) decreased sensitivity of contractile macheneriy to Ca++

2) Facilitation of delayed rectifiers, Cl- channels that shorten duratino of AP