Cardiovascular Physiology

Question 1

Cardiac Output

Answer 1

CO= heart rate x stroke volume

Question 2

Factors affecting cardiac output heart rate

Answer 2

Autonomic innervation
hormones
fitness levels
age

Question 3

Factors affecting cardiac output stroke volume

Answer 3

Heart size
Fitness level
Gender
Contractility
Duration of contraction
Preload (EDV)
Afterload (resistance)

Question 4

Contractility of Heart

Answer 4

Modifiable, sympathetic nervous system controls

Question 5

Preload (EDV)

Answer 5

EDV = end diastolic volume
Amount of blood in ventricle at rest.
More blood in more blood out

Question 6

Afterload

Answer 6

Resistance.
Blockages heart has to work against, so pumps harder.
Pulmonary embolism, blood clot.

Question 7

Factors that affect blood flow through vessel

Answer 7

Poiseuille’s Law
Radius of vessel (increase with ballooning of tear)
driving pressure
viscosity
length of tube

Question 8

Poiseuille’s Law

Answer 8

Flow = (Pi.R^4/8n)x(dp/L)

Pi the constant
R=radius
n=viscosity
dP=driving pressure
L=length of tube

Question 9

How kidneys regulate own blood flow?

Answer 9

Afferent arteriole being larger than efferent arteriole creates filtering pressure forcing fluid through endothelium of capillaries into capsular space

Question 10

Filtration in kidneys.

Answer 10

1. 20% of fluid (plasma) from glomerulus capillaries to Bowmans space then proximal tubule.
2. Reabsorption of filtered material through the peritubular capillaries.
   3.Material leaves capillaries into the tubular fluid.
3. Urinary excretion. filtered + secreted - reabsorbed.

GFR=120-125 ml/min

Question 11

Location of juxtaglomerular apparatus (JGA)

Answer 11

Where distal convoluted tubule folds back contacting glomeruli, between afferent and efferent arterioles. At the outside walls of afferent arteriole.

Question 12

Where are macula densa cells?

Answer 12

In the wall of the distal convoluted tubule.

Question 13

Purpose of macula densa cells?

Answer 13

Release prostaglandin E2 when they sense low sodium.

Question 14

JGA purpose.

Answer 14

Release renin when acted upon by prostaglandin E2 form macula densa cells when they sense low sodium.

SNS activation, have B adrenoceptors?

Question 15

Significance of low sodium

Answer 15

Low sodium=low glomerular filtration rate (thinks Low blood flow)
vasoconstriction to increase blood flow.
From distal convoluted tubule perspective.

Question 16

Renin Function

Answer 16

Renin (in venous blood) meets angiotensinogen from liver enzymatically splits off peptide angiotensin 1

Question 17

Angiotensin 2 formation

Answer 17

In lungs angiotensin 1 is converted by local enzyme angiotensin-converting-enzyme (ACE) into angiotensin 2.

Question 18

Angiotensin 2 function in arterial blood

Answer 18

Triggers constriction of smooth muscle of systemic arterioles. Raises BP by increasing total peripheral resistance.

Question 19

Angiotensin 2 and adrenal cortex

Answer 19

Angiotensin 2 receptors found on adrenal cortex, stimulates release of aldosterone.

Question 20

Aldosterone function

Answer 20

Acts on channel proteins of distal convoluted tubule. [Inserts epithelial sodium channels]

Increases sodium reuptake from tubular fluid, pumping into intestinal fluid and then blood.

Increased sodium reabsorption, increased water absorption through osmosis. Increasing circulating blood volume, increasing systemic blood pressure.

Question 21

Angiotensin 2 and posterior pituitary gland

Answer 21

Acts on receptors in posterior pituitary gland. Activates release of anti diuretic hormone in circulation.

Question 22

ADH Function

Answer 22

Conserves water stimulates receptor on kidney that releases aquaporins (AQPZ).