Cardiovascular Physiology(autorhythmic Cells And Contractile Cells)

Question 1

What are autorhythmic cells?

Answer 1

• generates action potentials spontaneously

- W/ unstable membrane potential

Question 2

What are the 4 autorhythmic cells locations

Answer 2

Sa node

Av Node

Av bundle

Purkinje fibers

Question 3

Which node is the “leader”?

Answer 3

-Sa node: also called the pacemaker

Question 4

What is the membrane potential of autorhythmic cells?

Answer 4

• 60 mV membrane potential

- Heart doesn’t stop beating so it doesn’t have a resting membrane potential

Question 5

What happens during the pacemaker potential?

Answer 5

• I (f) channels open and Ca++ channels open (permeable to Na+/K+) > membrane potential depolarizes
  
  • predominate entry of Na+ ions into autothythmic cells
  • voltage sensitive (-60 mV)

-graded potential

Question 6

During the action potential production of autorhythmic cells, what happens during a steep depolarization?

Answer 6

-additional Ca++ channels open

Question 7

What happens during the repolarization phase in the autorhymic cells?

Answer 7

-K+ channels open

Question 8

What is the natural rhythm of a SA node? (Beats/minute)

What is the resting heart beat?

Answer 8

• 100 beats per minute

- 70 beats/minute)

Question 9

When the sympathetic nervous system is activated, what happens to heart rate?

Answer 9

-increases

Question 10

When the sympathetic nervous system is activated, what happens so that heart rate increases?

Answer 10

• norepinephrine binds to ‘Beta 1’ adrenergic receptor
• keeps I(f) channels and Ca++ channels open longer
• reach threshold quicker

Question 11

What is the effect of Parasympathetic on the heart (rate)?

Answer 11

-slows down heart rate

Question 12

What happens when parasympathetic system slows down heart rate?

Answer 12

-ACh binds to muscarinic receptor

-opens K+ channels > hyperpolarizes cell
And decreases Ca++ ion permeability

-lengthen time to reach threshold

Question 13

Where do the processes of the Sympathetic and parasympathetic effects occur normally?

Answer 13

-Sa nodes of the autorhythmic cells

Question 14

What is the function of autorhythmic cels

Answer 14

-serves as the pacemaker to initiate the cardiac cycle

(determines the amount of contractions that will occur)

Question 15

Once the autorhythmic cells determines the number of contractions, the cells of the Sa nodes send their signals to what structures?

Answer 15

-contractile nodes

Question 16

Contractile cells are excited by the action potential of what cell?

Answer 16

-autorhythmic cells

Question 17

Where is the action potential produced on contractile cells?

Answer 17

-sarcolemma

Question 18

Do contractile muscle cells have a resting membrane potential?

Answer 18

• yes, because they need to rest so blood can return to the chambers
  
  • -90mv

Question 19

How long is the plateau period of the contractile cells?

Answer 19

-between 100-200 msec

Question 20

What is the point of the plateau period of the action potential in the contractile cell

Answer 20

-so the beats wont overlap

Question 21

What is the difference of the excitation-contraction coupling process of the skeletal and cardiac muscle

Answer 21

Skeletal muscle: complete tetanus

Cardiac. Muscle: need rest period so blood can return;unfused tetanus

Question 22

What does the sarcoplasmic reticulum store?

Answer 22

-Ca++ ions

Question 23

What is the function of the long refractory period on cardiac muscle?

Answer 23

• no summation of cardiac contraction cells

- muscle prevents tetanus

Question 24

Comparison chart of action potentials in Cardiac and skeletal muscle

Answer 24