CARDIOVASCULAR 7

Question 1

Two types of Cardiac AP

1) Type 1: Non-pacemaker cell (myocyte) action potentials: 2 things?

Answer 1

a) “Fast response” action potentials - rapid depolarization

b) Muscle cells -“soldier”- need instruction to fire

Question 2

2) Type 2: Pacemaker (autorthymic) cell: 2 things?

Answer 2

a) “Slow response” action potential - slower rate of depolarization
b) Found in the sinoatrial and atrioventricualr nodes

Question 3

Why is the underlying reason that hearts spontaenously contract?

Answer 3

Electrical initator cells termed”pacemakers”

Question 4

Autorhythmic nature of cardiac tissue: 4 steps

Answer 4

1) Unstable membrane potentials
2) Polarized to -55 TO 62Mv VS -85 TO 90mV
3) Slow depolarizing membrane potential
compared to resting potential in muscle cells
4) Due to “funny current” [If} channels active during resting phase

Question 5

I(f)channels are permeable to?
What does HCN stand for?
Steps: (6)

Answer 5

Both K+ and Na+ ions
Hyperpolarization-activated cyclic nucleotide gated channel
1) I(f) channels open
2) Some Ca2+ channels open I (f) channels close 
3) Lots of Ca2+ channel open
4) Ca2+ channels close, K+ channels open
5) K+ channels close
6) I(f) channels open

Question 6

Cardiac AP (roles of NA+ and CA+): Depolarization

1) Role of Na+
2) Role of Ca+

Answer 6

1) In most nerve + muscle cells

2) Cardiac pacemakers: initial depolarization and cardiac muscle (non-pacemaker): influx prolongs the duration of the AP

Question 7

How so autorhythmic signals reach muscle cells?

Pass through 3 different ways:

Answer 7

1) Cells of SA node
2) Intercalated disk with gap junctions
3) Depolarization of autorhythmic cells rapidly spread to adjacent contractile cells through gap jucntions

Question 8

Which cells have the ability to generate spontaneous APs?

Answer 8

All cells of the intrinsic conduction system

Question 9

Four parts involved in electrical conduction in the heart:

Answer 9

1) SA node
2) AV node
3) Purkinje fibers
4) Branches of atrioventricular bundle

Question 10

Electrical conduction in the heart: 5 steps

Answer 10

1) SA node depolarizes
2) Electrical activity goes rapidly to AV node via intermodal pathways
3) Depolarization spread more slowly across atria. Conduction slows through AV node
4) Depolarization moves rapidly through ventricular conduction system to the apex of the heart

Question 11

Overview of transmission

Answer 11

1) AP generated by SA mode
2) Spread throughout the atria
3) Causing atrial contraction
4) Impulse travels into the ventricles via AV node
5) Specialized conduction pathways (bundle branches and purkinjie fibers) within the venrticle
6) Ventricular contraction

Question 12

What is controlled by normal cardiac rhythm?

Answer 12

Pacemaker activity of the SA node

Question 13

Nodes and Internodal Pathways: control points

1) SA node
2) AV node

Answer 13

1) Sets pace for heartbeat at ~70bpm and AV node (50 bpm) and purkinje fibers (25-40 bpm) can act as pacemakers under some conditions
2) Routes the direction of electrical signals and delays the transmission of APs

Question 14

Conductive fibers are often ?

How atrial and ventricular myocyte syncytia are separated?

Answer 14

a) Sheathed (separated from myocyte connections)

b) Inert fibrous tissue barrier

Question 15

What regulated the heart rate?

Answer 15

Sympathetic and Parasympathetic nervous systems

Question 16

Parasympathetic control of Heart rate?
2 Main characteristics:
What is resting heart rate?
Name a M2R antagonist and state its effect?

Answer 16

Activity lower heart rate
1) Activated the vagus nerve that innervates the SA node
2) Release the neurotransmitter Ach bind to M2R in SA node cells
60 to 80 beats/min
Atropine: increases the hert rate by 20 to 40 beats per min

Question 17

Effector pathways of parasympathetic signalling: 4 steps

Answer 17

1) GIRK activation by Gbetagamma
2) Galpha-mediated inhibition of Adenyly cyclase 3) Decease of cAMP/PKA activation of Cav
4) Decrease cAMP activation of HCN

Question 18

Control of Heart rate: increasing heart rate:

Requires 2 things:

Answer 18

1) Withdrawal of vagal tone

2) Activation of sympathetic nerves

Question 19

Sympathetic signalling:
Which neurotransmitter is released ?
What does it bind to?
Another form of stimulation?

Answer 19

Norepinephrine
Adrenergic receptors on SA nodes
Circulating catecholamines released form the adrenal gland during a sympathetic response

Question 20

Sympathetic signalling:

1) Activity results in?
2) Which channels show increased activity?

Answer 20

1) Increased cAMP and PKA activity

2) Cav (L-type Ca2+ channels) and HCN (funny current) channel activity

Question 21

Contraction strength

1) Parasympathetic fibers
2) Sympathetic fibers

Answer 21

1) Cannot change the force of contraction – only intervate the SA node and AV node
2) Can increase force of contraction – intervate with atria and ventricles themselves

Question 22

Einthoven's triangle?
Charged nodes:
1) Right arm 
2) Left leg 
3) Left arm

Answer 22

For complex signals

1) Negative
2) Positive
3) Positive/Negative

Question 23

The Electrocardiogram: Three major waves

Answer 23

1) P wave
2) QRS complex
3) T wave

Question 24

Electrical Activity:

1) P wave
2) PQ or PR segment
3) Small dip
4) Large spike
5) Small dip
6) ST segement
7) T wave

Answer 24

1) Atrial depolarization
2) Conduction though AV node and AV bundle - atria contract
3) Q wave
4) R wave
5) S wave
6) Ventricles contract
7) Ventricular repolarization

Question 25

Abnormal electrocardiograms

1) 3rd degree block
2) Atrial fibrillation
3) Ventricular fibrillation
4) 2nd degree heart block: AV node

Answer 25

1) Normal P, wide QRS
2) ‘no P’, Irregular QRS
3) ‘no P’, no QRS
4) Normal P, normla QRS