Cardiophysiology

Question 0

In diastole, coronary blood flow is highest in…

Answer 0

Left ventricular subendocardial region

Question 1

In systole, Coronary vascular resistance is highest in…

Answer 1

Left ventricular subendocardial region (due to heavy compression—vasodilator build-up)

Question 2

Resting heart rate is influenced by…

Answer 2

Parasympathetic/vagal nerve innervation of the heart, dependent in atropine sensitive cholinergic receptors in SA node.

Question 3

3 actions of pressor center in baroreceptor reflex consist of…

Answer 3

Heart: HR, contractility increase
Resistance vessels: TPR increase
Capacitance vessels: CVP/SV increase

Question 4

Explain autoregulation of a vascular bed.

Answer 4

Local metabolites and VSM myogenic responses to a change in local perfusion pressure. c.f. Lungs, brain

Question 5

Explain Reactive hyperemia

Answer 5

The local effect of metabolites in response to inadequate blood flow relative to local metabolism.

Question 6

How will leaky aortic valve (aortic insufficiency) affect LV coronary blood flow?

Answer 6

During diastole, blood will leak back to LV, increasing preload and increasing the work needed to be done by LV (flow will go up). But work by pressure is MUCH more important.

Question 7

Direct effects of sympathetic nerves on VSM fibers consist of…

Answer 7

Vasoconstriction via alpha adrenoceptors (adrenergic receptors) and vasodilation via beta adrenoceptors. This is NOT autoregulation.

Question 8

What does Atropine do?

Answer 8

Blocks muscarinic (cholinergic) receptors for Ach released by parasympathetic nerves to the heart.

Question 9

What does Propanolol do?

Answer 9

Blocks beta-adrenergic receptors for norepinephrine released by sympathetic nerves to the heart.

Question 10

What are intrinsic regulations of the heart?

Answer 10

Heterometric/starlings law of heart

Homometric/Treppes mechanism

Question 11

Why does athletes have slow heart rate?

Answer 11

Increased vagal tone

Slow intrinsic SA node firing rate

Question 12

Name humoral factors that lead to vasoconstriction of VSM in resistance vessels.

Answer 12

Predominantly NE
HIGH dosage of E
ADH
Angiotensin II
Endothelin

Question 13

Name humoral factors that lead to vasodilation of VSM in resistance vessels.

Answer 13

Histamine
LOW dose of E (via beta adrenergic receptors)
Bradykinin
Endothelium Derived Relaxing Factor (EDRF); NO

Question 14

Describe chemoreceptor reflex effects.

Answer 14

The carotid body detects low O2 and pH. TPR is directly increased as a result, HR more complicated; MAP increased.
Breathing is induced and arousal stimulated during sleep.

Question 15

Name four mechanisms that aid Venous Return.

Answer 15

Muscle pump
Respiratory pump
Cardiac suction
Valves in vein

Question 16

Explain five ways Blood Volume regulation works when discharge rate of low baroreceptor reflex is increased.

Answer 16

Decreased renal sympathetic nerve activity-> increased renal filtration pressure
Increased filtration pressure (stretch) also results in Decreased renin release
Decreased ADH
Increased HR by reflex
Blood Volume increase in atria result in Release of Atrial Natriuretic Peptide (ANP)—helps excrete sodium and salt

Question 17

At a capillary level, what three factors will increase in Blood Volume? Think of arterial/venous end pressure.

Answer 17

Decreased MAP
Decreased venous end pressure
Increased TPR/arterial end pressure
All these three result in decreased capillary pressure and helps the interstitial fluid to flow in vascular urge

Question 18

Explain autotransfusion.

Answer 18

This is the effect to restore BV by increasing sympathetic outflow to precapillary end of VSM in arterioles, decreasing capillary pressure. Interstitial fluid flood in. Hematocrit decreases as a result. Think of one of five BV regulation.

Question 19

Explain blood flow regulation in skin during exercise.

Answer 19

As body temperature increases, sympathetic nerves controlling cutaneous blood flow are inhibited, leading to vasodilation and dissipation of heat. Local vasodilator has little effect.

Question 20

In the exercising skeletal muscle, what is the status of sympathetic activity in the arterioles?

Answer 20

Although TPR increases as a result of sympathetic controller turned up, local vasodilator override such effects. Vasodilation occurs. Same applies in brain and heart.

Question 21

What initiates sympathetic outflow during the exercise?

Answer 21

Efferent reflex of skeletal muscles turn on the central sympathetic command in the brain, I.e. anticipation of exercise.

Question 22

Explain Cushing’s Reflex

Answer 22

Brain Swelling (edema) or an intracranial mass increases intracranial pressure->presses brainstem controller->blood pressure increases and HR slows down (BRR turnt down!)

Question 23

Describe the effects of hyperventilation on cerebral blood flow.

Answer 23

It lowers CO2 partial pressure in the arteries (hypocapnia) resulting in vasoconstriction of cerebral vessels. Cerebral blood flow decreases.

Question 24

Describe Acute Hypertensive Encephalopathy and two hypotheses for its pathophysiology.

Answer 24

Sustained or sudden increase in MAP to high levels, resulting in vascular cerebral crisis. 1. Vasospasm (Excessive Autoregulation): intense vasoconstriction leading to cerebral ischemia. 2. Forced Vasodilation (Failed Autoregulation): higher capillary pressure forces fluid leak into tissues.

Question 25

What should happen if the breaking point in MAP to maintain a steady flow via Autoregulation were to shift to right? I.e. Be able to Autoregulate at high MAP?

Answer 25

Turn on sympathetic nerve activity.

Question 26

How does standing and walking for a few minutes every hour during prolonged sitting help prevent edema?

Answer 26

Muscle pumps operate to send blood from the dependent venous toward the heart and use the valves in the leg veins to keep venous blood flowing back.

Question 27

What could result in very low blood pressure and a slightly below normal heart rate?

Answer 27

Overdosing with a drug causing blockage of sympathetic actions?

Question 28

How do you explain an increased pulse pressure in toxic shock syndrome?

Answer 28

Decreased TPR due to leaky capillaries -> decreased MAP -> decrease in afterload and end-diastolic pressure. Systolic pressure may go up as a reflex, resulting in an increased pulse pressure.

Question 29

What happens to pulmonary vascular resistance during heavy exercise?

Answer 29

Falls as pulmonary arterial pressure and flow increase as a result of increased need to oxygenate the blood.