UNIT 4 REVISION Flashcards

Question

ejection fraction

Answer 1

fraction of the EDV ejected in one storke volume, storke volume divided by EDV

Answer 2

total volume ejected by the ventricle per unit time, equal to venous return

Answer 3

prelaod contractility and afterload

Answer 4

`- Changes in stroke volume occur following changes in resting ventricular muscle fibre length (preload) - Mechanism intrinsic to the heart

Answer 5

- Inotropic effect - Changes in stroke volume without changes in resting ventricular muscle fibre length (no change in preload) - Mechanism extrinsic to the heart

Answer 6

- Changes in aortic pressure

Answer 7

- closure of inactivation gates of sodium channel in response to depolarisation - gates closed position until cell is depolarised back to resting membrane potential and Na+ have recovered to closed but available state

Answer 8

- action potential can be elicited - only if a greater than usual depolarisation current - higher K+ conductance than is present at rest - membrane potential is closer to K+ equilibrium potential - more inwards current needed to bring membrane to threshold for next action potential to be initiated

Answer 9

occurs when there is movement of an ion across the cell membrane

Answer 10

when there is 1. driving force on the ion 2. membrane has conductance to the ion

Answer 11

Phase 0: upstroke, rapid depolarisation, Na+ influx Phase 1: initial repolarisation, Na+ influx stops, K+ efflux Phase 2: plateau, stable depolarisation, Ca2+ influx via L-type calcium channels, k+ efflux Phase 3: repolarisation, Ca2+ influx stops, K+ efflux Phase 4: resting membrane potential, close but not equal to K+ equilibrium potential

Answer 12

Phase 0: upstroke, rapid depolarisation, Ca2+ influx Phase 3: repolarisation, Ca2+ influx stops and K+ efflux Phase 4: influx of Na+ through funny channels which is turned on by repolarisation from previous AP, gradient restored

Answer 13

Features of SAN action potentials: 1. automaticity: spontaneous AP generation without neural input 2. unstable resting potential 3. no sustained plateau

Answer 14

effects on autonomic nervous system on the heart rate , increase is sympathetic

Answer 15

: effects on the autonomic nervous system on conduction velocity, increase is the increase in conduction velocity through AV node

Answer 16

intrinsic ability of myocardial cells to develop force at a given muscle length, increase will increase contractility

Answer 17

1. size of inward Ca2+ current 2. amount of Ca2+ previously stored in the SR for release

Answer 18

isovolumetric contraction is 1 to 2 ventricular ejection is 2 to 3 isovolumetric relxation is 3 to 4 ventircular fillng is 4 to 1

Answer 19

pressure during ventricular relaxation, lowest pressure

Answer 20

: highest pressure, pressure after the blood has been ejected

Answer 21

when aortic valve closes, brief period of retrograde flow towards valve, briefly decreasing aortic pressure below systolic

Answer 22

difference between diastolic and systolic

Answer 23

Pa, average pressure over complete cardiac cycle, DP + 1/3 pulse pressure, 70-100 mmHg

Answer 24

Q= different in pressure / resistance

Answer 25

resistance of entire systemic vasculature (TPR) or systemic vascular resistance (SVR) R a 1/r4 (remember this!)

Answer 26

carotid sinus aortic arch

Answer 27

glossopharyngeal nucleus tractus solitarus cardiac decelerator parasympathetic SAN

Answer 28

vagus nucleus tractus solitarus decreases careidac acceleratory and vasoconstriction increases SAN, contractility, arterioles and venous vasodilation

Answer 29

- Massage carotid sinus distends the barorecpetors - Increases vagal outflow to the heart - Slows SA firing and AV conduction - AVN conducts fewer action potentials through ventricles - Less QRS complexes, ventricular rate slows from dangerously high rates

Answer 30

- Cold water stimulates the sensory receptors of the trigeminal nerve and receptors in the nasopharynx and oropharynx - Resulting in: 1. Apnoea 2. Bradycardia 3. Peripheral vasoconstriction

Answer 31

1. Inhale deeply and then hold the breath. 2. Imagine that the chest and stomach muscles are very tight and bear down as though straining to initiate a bowel movement. 3. Hold this position for a short time, usually about 10 seconds. 4. Breathe out forcibly to release the breath rapidly. 5. Resume normal breathing

Answer 32

1. Increased intrathoracic pressure increases blood flow from the pulmonary circulation into the left atrium. This increases left ventricular EDV and SV. There is also compression of the aorta, increasing blood pressure. 2. High intrathoracic pressure impedes venous return, decreasing SV and therefore also blood pressure. During this period, there is a baroreceptor-mediated increase in heart rate. 3. When the manoeuvre is released, compression on the aorta is stopped and left ventricular filling pressures are reduced temporarily as the pulmonary vessels re-expand. This causes a drop in blood pressure. 4. VR is restored, increasing cardiac filling pressures and SV. This increases BP, resulting in a baroreceptor reflex-mediated bradycardia and subsequent fall in BP to normal levels.