Phys Lecture I Cardiac excitation

Question 1

Where does sympathetic stimulation to the heart originate?

Answer 1

Medulla Oblongata

Question 2

What nerve carries the parasympathetic innervation to the heart?

Answer 2

Vagus Nerve.

Question 3

Is there parasympathetic innervation to the ventricles?

Answer 3

No

Question 4

Where do the parasympathetic branches go to?

Answer 4

SA and AV node

Question 5

What structure in the heart is the main pacemaker i.e spontaneously generates action potentials which cause cardiac excitation/contraction?

Answer 5

SA node

Question 6

How does electrical activity travel from SA to AV node?

Answer 6

Internodal pathways

Question 7

How long does it normally take for a complete ventricular electrical cycle?

Answer 7

200msec

Question 8

What channel maintains the cells in a highly polarized state?

Answer 8

Ik1

Question 9

At what voltage do the sodium channels get activated?

Answer 9

-60mv

Question 10

How is the Ca2+ channel activated?

Answer 10

Voltage activated channel

Question 11

What channelis responsible for PHASE 1? The transient repolarization?

Answer 11

Ito. This is called the transient outward channel and is responsible for the transient outward flow of K+ ions

Question 12

How is the Potential maintained during PHASE 2?

Answer 12

Outward flow of K+ and inward flow of Ca2+

Question 13

What is significant about the If channel?

Answer 13

It is a Na channel which becomes activated while the cell is polarized and turn off when the cell is depolarized

Question 14

What ion is responsible for the post threshold polarization of SA nodal cells?

Answer 14

Influx of Ca2+

Question 15

What tissues have the fastest conduction rates?

Answer 15

Bundle of HIS and Purkinje cells

Question 16

What is the intrinsic rate of the SA node absent any neuro influence?

Answer 16

100-120 beats per minute

Question 17

What two sets of tissues can under pathological states develop their own spontaneous activity and serve as pacemakers?

Answer 17

1. Atrial Muscle

2. Ventricular muscle

Question 18

What are the effects of parasympathetic activity on the heart?

Answer 18

1. Decreases Heart rate
2. Decreases conduction velocity particularly in the AV node
3. Decreases excitability of latent pacemakers

Question 19

What are the effects of Sympathetic activity on the heart?

Answer 19

1. Increases HR
2. Increases conduction velocity (particularly in the AV node)
3. Decreases the threshold of Ca channels:Increases excitability of Latent pacemakers nd other cells

Question 20

What is the neurotransmitter of the parasympathetic activity?

Answer 20

Acetylcholine

Question 21

What is the neurotransmitter of cardiac sympathetic activity?

Answer 21

Norepinephrine

Question 22

Which activity prevails when it comes to the SA node?

Answer 22

Paraympathetic