week 7 the heart

Question 1

how many circuits does the cardiovascular system have?

Answer 1

2 - pulmonary and systemic

Question 2

which system has the highest pressure

Answer 2

systemic

Question 3

how many chambers does the heart have

Answer 3

4 - two atria 2 ventricles

Question 4

which chamber is most muscular

Answer 4

left ventricle

Question 5

why are the valves important

Answer 5

prevent backflow

Question 6

what are the 3 layers of the heart walls

Answer 6

outer layer = epicardium (simple squamous epithlium + loose connective tissue + adipose layer)

middle layer = myocardium (cardiac muscle layer)

Inner layer = endocardium (simple squamous epithlium) smooth layer to minimise friction)

Question 7

what are the cardiac muscles layer a combination of

Answer 7

99% contractile muscle cells

1% autorhythmic cells (generate action potential

Question 8

what structure do the cardiac muscle cells have to allow them to contract simultaneously

Answer 8

gap junction which allows the ions to travel from cell to cell transmitting action potentials

Question 9

what are autorhythmic cardiac muscle cells

Answer 9

have pace making potential

control influx of NA, efflux of K and CA influx

Question 10

what are the pace making potentials (autorhythmic cells) of the different tissues/structures in the heart

Answer 10

SA node - 70-80
AV node - 40-60
bundle of his and Purkinje fibres - 20-40

Question 11

what is the role of the heart conduction system

Answer 11

coordinate contraction of the heart chambers and when route/timing of action potentials

Question 12

what are the 3 criteria of the spread of excitation through the heart must meet (EXAM IMPORTANT)

Answer 12

1. each heart chamber must pump as a unit
2. atria should contract together; ventricles should contract together
3. atrial excitation and contraction must complete before ventricle contraction

Question 13

what is the first sound of the heart contraction

Answer 13

closure of the AV valve

beginning of ventricular systole

Question 14

what is the second sound of the heart contraction

Answer 14

closure of the semilunar valves

ventricular diastole

Question 15

what is the cardiac cycle (EXAM IMPORTANT)

Answer 15

1. ventricle and atrial diastole
   - blood entering atrium AV opens passive and blood moves into ventricles passively
2. atrial contraction
   - atrial pressure increases and ventricle volume increases until end diastole volume EDV
3. isovolumetric ventricular contraction
   - ventriclar pressure is larger then atrial pressure = AV valve to close (1st sound)
   - ventricular pressure is less less then aortic pressure = semi-lunar vallves to close
4. ventricular ejection
   - pressure is greater in ventricles over aortic pressure
   - semi lunar valves open
   - ventrcular pressure decreases until end systolic pressure (ESV)
5. isovolumetric ventricular relaxtion
   - semi lunar valves close (2nd sound)