CS: Blood Pressure

Question 1

What is stroke volume?

Answer 1

Stroke volume is the volume of blood pumped from the left ventricle per beat

Question 2

How can stroke volume be increased?

Answer 2

Ventricles never fully empty following ventricle contraction, therefore, stroke volume can be increased by increased contraction by sympathetic (adrenergic) input or increased ventricular filling due to increased blood in ventricles prior to contraction.

The volume of blood that flows into the atria during atria diastole is known as the venous return. Increased venous returns will increase ventricular filling, and ultimately stroke volume, and greater ventricular filling will also increase ventricular muscle stretch.

Question 3

What is the venous return?

Answer 3

The volume of blood that flows into the atria during atria diastole

Question 4

What is Starlings law?

Answer 4

Increase in preload causes an increase in muscle fibre stretch, leading to increased force of ventricular contraction, resulting in a greater stroke volume. Decrease in preload causes a decrease in muscle fibre stretch, leading to decreased force of ventricular contraction, resulting in a reduced stroke volume.

Question 5

What are baroreceptors?

Answer 5

Pressure sensitive mechanoreceptors that respond to changes in arterial pressure and stretch

Question 6

Where are baroreceptors located?

Answer 6

Located in the aortic arch and the carotid sinus, and are connected to centres in the medulla oblongata by afferent neurons.

Question 7

How is blood pressure regulated by the medulla oblongata?

Answer 7

Cardiac feedback in response to information from baroreceptors via the sympathetic and parasympathetic afferent neurons of the ANS.

Question 8

What is the short-term regulation of rising blood pressure?

Answer 8

1. Rising blood pressure
2. Stretching of arterial walls
3. Stimulation of baroreceptors in the carotid sinus and aortic arch
4. Increased impulses to the medulla oblongata of the brain
5. Increased activity of the vagus nerve (parasympathetic) and decreased activity of sympathetic cardiac nerves.
6. Decreased cardiac output.
7. Increased arterial diameter
8. Lower blood pressure.

Question 9

What is the short-term response to falling blood pressure?

Answer 9

1. Falling blood pressure
2. Baroreceptors inhibited
3. Decreased impulses to the medulla oblongata of the brain
4. Decreased parasympathetic activity and increased sympathetic activity
5. Blood vessels constrict
6. Adrenal glands stimulated to release adrenaline and noradrenaline into the blood which causes an increase in heart rate, contractility and vasoconstriction.
7. Increased blood pressure

Question 10

How is long-term regulation of blood pressure accomplished?

Answer 10

Long term regulation of blood pressure is primarily accomplished by altering blood volume. Long term regulatory processes promote the conservation of body fluid via renal mechanisms and stimulate intake of water to normalise blood volume and pressure.

Question 11

What incidents can cause a fall in blood pressure?

Answer 11

Loss of blood through haemorrhage, accident, or donation will lower the blood pressure and trigger processes to restore blood volume and pressure back to normal.

Question 12

Describe the renin-angiotensin pathway?

Answer 12

Juxtaglomerular cells, found in the afferent arterioles of the glomerulus of the kidneys, are specialised smooth muscle cells with b1 receptors that respond to (Nora)adrenaline. They release renin into the blood which binds to angiotensinogen and converts it to angiotensin I. Angiotensin I is converted to angiotensin II by angiotensin converting enzyme (ACE) in the lung capillaries.

Question 13

What cells release renin?

Answer 13

Juxtaglomerular Cells in the afferent arterioles of the glomerulus of the kidney nephrons

Question 14

What cells release ACE?

Answer 14

Lung capillary cells

Question 15

What is ACE?

Answer 15

Angiotensin Converting Enzyme

Question 16

What are the actions of angiotensin II?

Answer 16

1. Potent vasoconstrictor that causes blood pressure to rise in the body’s arterioles.
2. Stimulates release of aldosterone from the adrenal cortex that targets cells of the distal convoluted tubules.

Question 17

What is the role of aldosterone?

Answer 17

Promotes the retention of sodium ions and water, in exchange for potassium ions. Movement of sodium ions back into the blood creates an osmotic gradient which forces the reabsorption of water, from the urine, to increase blood volume.

Question 18

What is osmolarity?

Answer 18

Osmolarity is the total concentration of all solutes in a solution

Question 19

What causes dehydration?

Answer 19

Dehydration can be due to sweating, diarrhoea, or excessive urine flow

Question 20

What are the short-term effects of increased osmolarity?

Answer 20

Increased osmolarity excites the ‘thirst centres’ in the hypothalamus and triggers the individual to drink more water to rehydrate the blood and extracellular fluid; blood pressure and volume restored.

Question 21

What is the action of the hypothalamic thirst centres?

Answer 21

Send signals to the posterior pituitary gland to release ADH which stimulates the kidneys to reabsorb water through aquaporin water channels in the distal convoluted tubule and the collecting ducts.

Question 22

What is ADH?

Answer 22

Anti diuretic hormone

Question 23

What is the role of aquaporins?

Answer 23

Aquaporins aid in the movement of water from the urine to the bloodto decrease osmolarity and increase blood pressure and volume.

Question 24

What is the effect of caffeine and alcohol on ADH levels?

Answer 24

Decreased levels of ADH resulting in less water reabsorption and more dilute urine; excessive urination is seen.

Question 25

What happens when a RBC is placed in a isotonic solution?

Answer 25

Remains normal. No net flow of solutes.

Question 26

What happens when a RBC is placed in a hypertonic solution?

Answer 26

Water will leave the RBC and enter the hypertonic solution; will result in RBC crenation

Question 27

What happens when an RBC is placed in a hypotonic solution?

Answer 27

What will enter the RBC from the hypotonic solution; will cause RBC s to swell with water and eventually lyse.