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Cardiology SB > Physiology > Flashcards

Physiology Flashcards

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1
Q

what is the spread of excitation in the heart

A

1 - Across the atria mainly cell-to-cell conduction via gap junctions
2 - From SA node to AV node: mainly cell-to-cell conduction via gap junctions; but there is also some internodal pathways
3 - The conduction is delayed in the AV node.
4 - The Bundle of His and its branches and the network of Purkinje fibers allow rapid spread of action potential to the ventricles
5 - Ventricular muscle: cell-to-cell conduction
Diastole

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2
Q

what stimulation decreases the HR

A

Parasympathetic

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3
Q

what is classified as bradycardia

A

HR less than 60

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4
Q

what is classified as tachycardia

A

HR more than 100

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5
Q

what does a negative chronotropic effect do

A

slows down HR (parasympathetic)

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6
Q

what does a positive chronotropic effect do

A

increases HR (sympathetic)

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7
Q

what is an ECG a record of

A

depolarization and repolarization cycle of cardiac muscle obtained from the skin surface

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8
Q

what values shut together

A

Tricuspid and Mitral

Pulmonary and aortic

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9
Q

how long does diastole and systole last for

A

diastole - 0.5sec

systole - 0.3sec

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10
Q

what happens in systole

A

the heart ventricles contract and pump blood into the: aorta (LV) and pulmonary artery (RV)

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11
Q

what happens in diastole

A

the heart ventricles are relaxed and fill with blood

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12
Q

what is the process of Isovolumetric Ventricular Contraction

A
  • Ventricular pressure rises
  • When ventricle pressure exceeds atrial pressure the AV values shut
  • produces first heart sound (‘lub’)
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13
Q

when does the aortic/pulmonary value open

A

When the ventricular pressure exceeds aorta/pulmonary artery pressure

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14
Q

what does the T wave on an ECG represent

A

ventricular repolarisation

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15
Q

what happens after the aortic/pulmonary value open

A

Ventricles relax

ventricular pressure start to fall

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16
Q

what happens when the ventricular pressure falls below aortic/pulmonary pressure

A

aortic/pulmonary valves shut

this produces the second heart sound (dub)

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17
Q

what does the Closure of aortic/and pulmonary valves signal

A

isovolumetric ventricular relaxation

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18
Q

what happens when the ventricular pressure falls below atrial pressure

A

AV valves open and the heart starts a new cycle

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19
Q

what are the 5 stages of the cardiac cycle

A 
1 - Passive Filling
2 - Atrial Contraction
3 - Isovolumetric ventricular Contraction
4 - Ventricular Ejection
5 - Isovolumetric ventricular Relaxation
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20
Q

how does arterial pressure not fall to zero during diastole

A

elastic tissue

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21
Q

when does JVP appear

A

after right atrial pressure waves

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22
Q

what is the a wave on the JVP

A

atrial contraction

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23
Q

what is the c wave on the JVP

A

bulging of tricuspid valve into atrium during ventricular contraction

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24
Q

what is the v wave on the JVP

A

rise of atrial pressure during atrial filling: release as AV valves open

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25
what happens in diastole (in relation to ions)
sodium enters the cell Calcium exits the cell Calcium enters the SR
26
what does stretch do in relation to calcium
increases the affinity of troponin for Ca++
27
when is the optimal length in cardiac muscle achieved
by stretching the muscle
28
what happens if venous return to right atrium increases
EDV of right ventricle increases | Starling’s Law leads to increased SV into pulmonary artery
29
when does EDV of left ventricle increase and what does this cause
Venous return to left atrium from pulmonary vein increases | Starling’s Law leads to increased SV into aorta
30
what does sympathetic stimulation do
increases the force of contraction (positive inotropic effect)
31
what is the effect of sympathetic stimulation on ventricular contraction
1 - Force of contraction increases 2 - peak ventricular pressure rises 3 - Rate of pressure change (dP/dt) during systole increases 4 - reduced the duration of systole 5 - Rate of ventricular relaxation increases 6 - reduces duration of diastole
32
how is force of contraction increased in sympathetic stimulation and what mediates it
activation of Ca++ channels - greater Ca++ influx | cAMP
33
how is the rate of ventricular relaxation increased in sympathetic stimulation
increased rate of Ca2+ pumping
34
what does the Frank-Straling curve shifted to the right
heart failure
35
what should systolic and diastolic BP not exceed
s - 140mmHg | d - 90mmHg
36
what is the effect of the parasympathetic stimulation on the heart
decreases HR decreases CO decreases MAP
37
what is the effect of the sympathetic stimulation on the heart
increases HR-increases CO-increases MAP | increases contractile strength of heart-increases SV-increases CO-increases MAP
38
what is the effect of the sympathetic stimulation on the arterioles
increases vasoconstriction-increases TPR- increases MAP
39
what is the effect of the sympathetic stimulation on the veins
increases vasoconstriction-increases Venous return-increases stroke volume-increases cardiac output- increases MAP
40
what causes postural hypotension
failure of Baroreceptor responses to gravitational shifts in blood, when moving from horizontal to vertical position
41
what are the two main factors affect Extracellular Fluid volume
Water excess or deficit | Na+ excess or deficit
42
what affect does angiotensin II have on the systemic system and how does it achieve this
vasoconstriction -increases TPR and BP | increases ADH and thirst -increases Plasma Volume and BP
43
what does aldosterone do
acts on the kidneys to increase sodium and water retention increases plasma volume therefore, increases BP
44
where does aldosterone come from
adrenal cortex
45
where does ACE come from
lung vascular endothelium
46
what stimulates the release of rennin from the juxtaglomerular apparatus in the kidneys
1 - Renal artery hypotension -caused by systemic hypotension (↓ blood pressure) 2 - stimulation of renal sympathetic nerves 3 - Decreased [Na+] in renal tubular fluid
47
where is ADH synthesised and where is it stored
hypothalamus | posterior pituitary
48
what is ADH also known as
vasopressin
49
what is plasma osmolality monitored by
osmoreceptors in the brain in close proximity to hypothalamus
50
when is the release of ADH stimulated
when there is an increased plasma osmolality
51
mechanism of action of ADH
1 - increase reabsorption of water 2 - increase extracellular and plasma volume 3 - increases CO and BP
52
affect of ADH on blood vessels
vasoconstriction - increase TPR and BP | important in hypovolaemic shock e.g. haemorrhage
53
what does contraction and relaxation of vascular smooth muscle cause
vasoconstriction - increases TPR and MAP | vasodilatation - decreases TPR and MAP
54
what is the effect of increase sympathetic discharge on vascular smooth muscle
vasoconstriction
55
what factors causes relaxation of arteriolar smooth muscles resulting in VASODILATATION
``` Decreased local PO2 Increased local PCO2 Increased local [H+] (decreased pH) Increased extra-cellular [K+] Increased osmolality of ECF Adenosine release (from ATP) ```
56
where is NO produced and from what
vascular endothelium from the amino acid L-arginine through enzymatic action of Nitric Oxide Synthase (NOS)
57
what is the mechanism of action of NO
1 - diffuses from the vascular endothelium into the adjacent smooth muscle cells 2 - activates the formation of cGMP 3 - serves as a 2nd messenger for signalling smooth muscle relaxation
58
what causes increased venous return
increase venomotor tone increased skeletal muscle pump increased resp pump increased blood volume
59
what does increased venous return causes
increased atrial pressure-increase EDV-increased SV
60
what does increased venomotor tone causes
increased venous return, SV and MAP
61
what does increased vasomotor tone causes
increases TPR and MAP
62
how does contraction of muscles aid venous return
large veins lie in between skeletal muscle One-way venous valves allow blood to move towards the heart Muscle Activity increases VENOUS RETURN to heart
63
how does sympathetic stimulation increase HR
INCREASING THE RATE OF FIRING OF SA NODE and DECREASES AV NODAL DELAY Increases force of contraction
64
what happens when slope of pacemaker potential increases
pacemaker potential reaches threshold quicker | frequency of action potentials increases
65
what does adequate tissue perfusion depend on
adequate blood pressure and adequate cardiac output
66
where do the right and left coronary arise from
the base of the aorta
67
what is the mechanism of adenosine
potent vasodilator cause vasodilation of coronary arteries increase blood flow to cardiac muscle
68
what does shortening diastole cause
very fast heart rate ↓ coronary flow

Cardiology SB (15 decks)

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