Heart

Question 1

list the order of blood flow starting from the vena cava

Answer 1

Superior, inferior vena cava
right atrium
right ventricle
pulmonary artery
lungs pulmonary vein
left atrium
left ventricle
aorta

Question 2

what is the definition of cardiac output?

Answer 2

total volume of blood pumped through the heart in one minute

Question 3

what is the average cardiac output?

Answer 3

5L/min

Question 4

how do you calculate cardiac output?

Answer 4

heart rate x stroke volume

Question 5

how long does the average cardiac cycle less if HR is 70bpm?

Answer 5

850ms

Question 6

what is the average EDV of the ventricle?

Answer 6

120ml

Question 7

what is the avenge ESV of the ventricle?

Answer 7

70ml

Question 8

how do you calculate Stoke volume?

Answer 8

EDV-ESV

Question 9

what parasympathetic nerve innervates the heart and where does it innervate?

Answer 9

vagus nerve, mainly the SAN and AV node

Question 10

where does the vagus nerve arise from?

Answer 10

brain stem

Question 11

where do the sympathetic nerves innervate the heart?

Answer 11

SAN, AVN and ventricles

Question 12

where do the sympathetic nerves that innervate the heart arise from?

Answer 12

thoracic spinal cord region

Question 13

what effect does sympathetic stimulation of the SAN have?

Answer 13

positive chronotropic effect
heart rate is increased by making it easier for the SAN to reach threshold
this is achieved by altering membrane potentials, the membrane is made more permeable to Na and Ca

Question 14

what effect does stimulating the vagus nerve have on the SAN?

Answer 14

negative chronotropic effect
(vagal tone)
harder for the SAN to reach threshold, reducing permeability to Na and Ca and increasing K+ leak channels (more hyperpolarisation)

Question 15

what determines EDV?

Answer 15

venous return which is determines by central venous pressure

Question 15

what effects central venous pressure?

Answer 15

contraction of large muscle surrounding veins
ventilation (breathing decrease thoracic pressure increasing blood flow)
decrease in total blood volume, dehydration, haemorrhage
Increase in total blood volume due to renal failure, or fluid retention due to activation of renin- angiotensin system
gravity
venous tone (sympathetic stimulation vasoconstriction)

Question 15

what will increase SV?

Answer 15

increasing EDV or decreasing ESV

Question 16

why does increasing EDV increase SV?

Answer 16

larger EDV = more tension = longer muscle fibres = more actin myosin cross bridges in sarcomere = stronger contraction
(frank starling mechanism)

Question 17

what is the frank starling mechanism?

Answer 17

force of ventricular contraction is dependent on the length of ventricular muscle fibres in diastole

Question 17

what other effect does increasing length of sarcomere’s have?

Answer 17

increase sensitivity to calcium

Question 18

what is the definition of an increase in contractility?

Answer 18

increase in contraction force at any given EDV

Question 19

what does an increase in contractility lead to?

Answer 19

decreased ESV, therefore an increase SV

Question 20

how is an increase in contractility achieved?

Answer 20

stimulating the parasympathetic nerves that innervate the ventricles
this increase the amount of Ca in heart cells leading to an increased contraction force

Question 21

what effects other than EDV and ESV effect the SV?

Answer 21

Afterload or blood pressure that the ventricle is pumping into
it must overcome this pressure in order to eject the stroke volume
therefore if blood pressure increase surpasses the contractility properties of the heart SV will decrease

Question 22

what are the 3 layers of the heart wall starting from the innermost?

Answer 22

(endocardium)
(myocardium)
(epicardium)

Question 23

what are the 3 layers of blood vessels starting from the innermost?

Answer 23

tunica intima
tunica media
tunica externa / adventitia

Question 24

what does the endocardium contain?

Answer 24

heart endothelium (squamous cells)
subendothelial layer of connective tissue e.g. collagen fibres

Question 25

what does the myocardium contain?

Answer 25

cardiac muscle cells therefore
* Striated, involuntary, intercalated discs
* Central nuclei, elongated and branched
* Intercalated discs contains gap junctions and desmosomes

Question 26

what does the epicardium contain?

Answer 26

adipose tissue, collagen and lymphatic vessels

Question 27

what layer are heart valves made up of?

Answer 27

folds in the endocardium

Question 28

what is the right AV valve called?

Answer 28

tricuspid

Question 29

what is the left AV valve called?

Answer 29

bicuspid

Question 30

what is the general histology of the heart valves?

Answer 30

dense irregular connective tissue core surrounded on each side by endocardium

Question 31

explain the tunica intima of the arteries?

Answer 31

squamous epithelial cells, basement membrane, underlying connective tissue and internal elastic lamina

Question 32

explain the tunica media of the arteries?

Answer 32

thickest layer, lots of elastic laminae and some smooth muscle cells

Question 33

explain the tunica externa of arteries

Answer 33

loose irregular connective tissue, collagen
most elastic arteries have vasa vasorum small nutrient blood vessels (capillaries lymphatics)

Question 34

give examples of muscular arteries

Answer 34

femoral and coronal

Question 35

explain what distinguishes muscular arteries?

Answer 35

smaller TM than elastic arteries
only 2 layer of elastic lamina, interanl and external
can tell this as they are easily distinguishable from the TM