the hearts eletrical system

Question 1

what is the SAN beats per minutiae

Answer 1

The SA node has an intrinsic rate of approximately 100 beats per minute and can initiate
cardiac contraction in the absence of any external control (hormonal or nervous)

Question 2

pace maker potential

Answer 2

SA node cells initiate an action potential due to an unstable membrane potential that is continuously drifting towards threshold

Question 3

Rate of firing from the cells of the SA node(sympathetic)

Answer 3

Sympathetic stimulation to the SA-
node leads to an increase in the slope
of the drift due to an increase of the
permeability of the Na +f current

Question 4

Rate of firing from the cells of the SA node(parasympathetic)

Answer 4

Parasympathetic stimulation to the SA-node leads to a decrease in the
slope of the drift due to an overall decrease of the inward current, and to
hyperpolarisation of the membrane due to increased K + permeability

Question 5

pathway of electrical stimulus

Answer 5

Stimulus spreads through the muscle fibres and stimulates both atria almost simultaneously.

• The AV-node and the bundle of His are the only pathway of the electric stimulus to travel from the
  atria to the ventricles and the signal is delayed at the AV-node in order to allow the atria to empty
  before ventricular contraction begins.
• The signal travels down the interventricular septum via the two bundle branches.
• The ventricles begin to contract as the stimulus spreads upwards depolarising muscle fibres via the Purkinje fibres.

Question 6

what is the p wave

Answer 6

small wave, contraction of the atria

Question 7

what is the q wave

Answer 7

ventrciles relax and fill up with blood

Question 8

what is the rs complex

Answer 8

ventricles contract

Question 9

what is the t wave

Answer 9

ventricle relaxation

Question 10

what is the tricuspid valve

Answer 10

Separates R atrium and R ventricle
Open when R atrial pressure > R ventricular pressure
Closed when R atrial pressure < R ventricular pressure

Question 11

what is the Pulmonary valve

Answer 11

Separates R ventricle and pulmonary artery (PA)
Open when R ventricular pressure > PA pressure
Closed when R ventricular pressure < PA pressure

Question 12

what is the Mitral (bicuspid) valve

Answer 12

Separates L atrium and L ventricle
Open when L atrial pressure > L ventricular pressure
Closed when L atrial pressure < L ventricular pressure

Question 13

what is the Aortic valve

Answer 13

Separates L ventricle and aorta
Open when L ventricular pressure > Aortic pressure
Closed when L ventricular pressure < Aortic pressure

Question 14

what is ventricle systole 1 stage(isovolumetric ventricle contraction)

Answer 14

AV VALVES CLOSED
AROTIC AND PULMONARY VALVES CLOSED due to the pressure not being high enough

Question 15

2nd stage of ventricle systole(ventricular ejection)

Answer 15

AV VALVES CLOSED

AORTIC AND PULMANORY VALVES OPEN

Question 16

diastole(isovolumetric ventricular relaxtaxtion)

Answer 16

all 4 valves close

Question 17

ventricular filling

Answer 17

atria relax and fill with blood

they then contract forcing blood to the ventricles as the AV valves open

Question 18

what happens at point A

Answer 18

Atrium and ventricle relaxed.
Mitral valve opens

Question 19

between a and b

Answer 19

Atrial contraction

Question 20

at point B

Answer 20

Ventricle begins to contract.
Mitral valve shuts (lub)

Question 21

between b and c

Answer 21

isovolumetric contraction

Question 21

at point c

Answer 21

ventricle pressure exceeds
aortic pressure.
Aortic valve opens

Question 22

at point D

Answer 22

Ventricle begins to relax, pressure
falls below aortic pressure.
Aortic valve shuts (dub)