The Peripheral Circulation 2

Question 1

Describe the role of arterioles controlling peripheral circulation.

Answer 1

Arterles, not capillaries, play a crucial role in controlling peripheral circulation due to their smooth muscle that allows for regulation of blood flow.

Question 2

Define Poiseuille’s law and its significance in blood flow regulation.

Answer 2

Poiseuille’s law states that resistance in a tube is proportional to the viscosity, length, and inversely proportional to the radius to the power of four. It highlights the significant impact of arteriolar radius on blood flow and mean arterial pressure.

Question 3

How does changing the radius of arterioles affect blood flow according to Poiseuille’s law?

Answer 3

Altering the radius of arterioles has a substantial effect on blood flow, as even small changes in radius can lead to significant changes in resistance and consequently, blood flow.

Question 4

Describe the two levels of control in regulating peripheral circulation.

Answer 4

Peripheral circulation is regulated through local control, involving factors within the tissue, and central control, which is governed by the nervous and endocrine systems.

Question 5

Explain the concept of viscosity in the context of blood flow.

Answer 5

Viscosity refers to the thickness or stickiness of blood, with higher viscosity making it harder for blood to flow. Changes in blood viscosity can impact resistance and flow in the circulatory system.

Question 6

How does Darcy’s law relate to blood flow through a tube?

Answer 6

Darcy’s law states that flow is equal to the pressure difference divided by resistance. It emphasizes the necessity of a pressure gradient for flow through a tube and the role of resistance in determining the ease of fluid movement.

Question 7

Describe the relationship between mean arterial pressure flow through vascular beds.

Answer 7

A in mean arterial pressure leads to decreased flow through vascular beds, as per Darcy’s law which states that pressure difference equals flow times resistance.

Question 8

Define arteriolar radius and its significance in blood flow regulation.

Answer 8

Arteriolar radius refers to the size of arterioles, which impacts flow through vascular beds and mean arterial pressure, crucial for regional blood redirection and overall perfusion.

Question 9

How does the body regulate blood flow through vascular beds and maintain mean arterial pressure?

Answer 9

The body controls blood flow and mean arterial pressure through resistance adjustments in arterioles, utilizing both local (intrinsic) mechanisms for individual tissue needs and central (extrinsic) mechanisms for overall body perfusion.

Question 10

Describe active or metabolic hyperaemia in blood flow regulation.

Answer 10

Active or metabolic hyperaemia refers to increased blood flow due to heightened metabolic activity in tissues, leading to the release of metabolites that trigger vasodilation and increased perfusion.

Question 11

Explain the role of endothelium in response to increased metabolite concentration.

Answer 11

When metabolite concentration rises, the endothelium lining capillaries releases local chemical signals, such as paracrine signals, to regulate vasodilation and enhance blood flow.

Question 12

What is the significance of resistance juggling in blood flow regulation?

Answer 12

Resistance juggling involves adjusting smooth muscle around arterioles to balance individual tissue needs and overall mean arterial pressure, ensuring sufficient perfusion through all vascular beds.

Question 13

Describe the process of arteriolar dilation in response to increased local metabolism.

Answer 13

Endothelial derived relaxing factor (EDRF) or nitric oxide is released from the endothelium, causing the arteriole to dilate, leading to increased blood flow.

Question 14

Define EDRF and its role in vascular regulation.

Answer 14

EDRF, later discovered to be structurally nitric oxide, is a paracrine signal released from the endothelium that causes arteriolar dilation, increasing blood flow to match metabolic needs.

Question 15

How does increased blood flow help regulate metabolite concentration in tissues?

Answer 15

Increased blood flow washes metabolites away more quickly, reducing their concentration and reaching a new steady state in the tissue.

Question 16

Do arterioles dilate in response to a decrease in perfusion pressure?

Answer 16

Yes, a decrease in perfusion pressure triggers the release of local signaling molecules like EDRF, causing arteriolar dilation to maintain blood supply despite changes in mean arterial pressure.

Question 17

Describe reactive hyperaemia and its trigger.

Answer 17

Reactive hyperaemia involves arteriolar dilation in response to occlusion of blood supply, such as using a sphygmomanometer cuff, leading to increased blood flow once the occlusion is removed.

Question 18

Explain the concept of local control mechanisms in vascular regulation.

Answer 18

Local control mechanisms like arteriolar dilation in response to increased metabolism, decreased perfusion pressure, or occlusion of blood supply help tissues regulate blood flow to match their metabolic needs.

Question 19

How does arteriolar dilation contribute to maintaining tissue blood supply during changes in arterial pressure?

Answer 19

Arteriolar dilation in response to decreased perfusion pressure ensures that tissues receive adequate blood flow by compensating for changes in mean arterial pressure.

Question 20

What is the role of EDRF in regulating blood flow in tissues?

Answer 20

EDRF, a paracrine signal released from the endothelium, causes arteriolar dilation, leading to increased blood flow and helping to match blood supply with tissue metabolic needs.

Question 21

Describe the process of arteriolar dilation in response to a paracrine signal like nitric oxide.

Answer 21

Endothelium releases nitric oxide, causing arterioles to dilate, leading to increased blood flow.

Question 22

Define pressure autoregulation in the context of blood flow.

Answer 22

Pressure autoregulation refers to the ability of tissues to maintain a relatively constant blood flow despite changes in perfusion pressure.

Question 23

How does the injury response lead to redness at the site of injury?

Answer 23

Activation of C-fibres triggers the release of substance P, which leads to histamine release, arteriolar dilation, increased blood flow, and increased permeability, causing redness.

Question 24

Describe the role of noradrenaline in the fight or flight response.

Answer 24

Noradrenaline, released from sympathetic nerves, binds to alpha 1 receptors on smooth muscle, causing arteriolar constriction and decreased blood flow.

Question 25

What is the impact of adrenaline release on arterioles in the body?

Answer 25

Adrenaline binding to alpha 1 receptors on smooth muscle leads to arteriolar constriction, decreased blood flow, increased total peripheral resistance, and mean arterial pressure.

Question 26

Explain the effect of parasympathetic nerves on blood vessels.

Answer 26

Parasympathetic nerves have minimal effect on blood vessels as they do not innervate most of them, except for notable exceptions like the genitalia and salivary glands where they cause increased blood flow.

Question 27

Describe the role of beta 2 receptors in the arterioles of the heart.

Answer 27

Beta 2 receptors in the arterioles of the heart lead to smooth muscle relaxation and arteriolar dilation when adrenaline binds to them.

Question 28

How does the cerebral circulation demonstrate pressure autoregulation?

Answer 28

The arterioles in the cerebral circulation dilate in response to a decrease in mean arterial pressure to maintain perfusion and ensure stable oxygen and glucose supply to the brain.

Question 29

Define the mechanism of ventilation-perfusion matching in the lungs.

Answer 29

Ventilation-perfusion matching is the process where arterioles in the lungs constrict in response to a decrease in oxygen partial pressure, redirecting blood flow to regions with better ventilation to optimize oxygen uptake.

Question 30

What is the main function of pressure autoregulation in the kidney’s renal circulation?

Answer 30

The main function of pressure autoregulation in the kidney’s renal circulation is to maintain a relatively constant glomerular filtration rate despite fluctuations in mean arterial pressure, protecting the glomeruli from damage caused by high blood pressures.

Question 31

Describe the response of arterioles in the pulmonary circulation to a decrease in oxygen partial pressure.

Answer 31

A decrease in oxygen partial pressure in the pulmonary circulation causes arteriolar constriction, contrary to most tissues, to optimize blood flow to lung regions with better ventilation for increased oxygen uptake.

Question 32

How does the body ensure stable oxygen and glucose supply to the brain in case of decreased mean arterial pressure?

Answer 32

The body ensures stable oxygen and glucose supply to the brain by allowing arterioles in the cerebral circulation to dilate in response to decreased mean arterial pressure, maintaining perfusion and preventing light-headedness or fainting.