Lecture 32

Question 1

what is Local Control of Blood Flow

Answer 1

refers to the regulation of blood flow within specific tissues or organs

typically in response to changes in their metabolic needs.

Question 2

why are Local mechanisms considered selfish

Answer 2

because it ensures that specific organ receives sufficient blood flow (doesn’t care where it comes from)

Question 3

what are the “intrinsic” regulatory mechanisms of Local Control of Blood Flow

Answer 3

Active hyperemia/reactive hyperemia
Flow auto-regulation

Question 4

what is Hyperemia

Answer 4

increased blood flow

refers to an increase in blood flow due to the dilation of arterioles and increased metabolic activity of the tissue

Question 5

what is Active hyperemia

Answer 5

immediate increase in metabolic activity

Question 6

Hyperemia is ______________ dependent

Answer 6

Metabolite dependent

Question 7

what is Reactive hyperemia

Answer 7

a temporary reduction in blood flow to a tissue or organ, followed by a sudden and marked increase in blood flow when the obstruction is relieved.

Question 8

explain active hyperemia’s negative feedback loop

Answer 8

Increased metabolic demand: The tissue or organ experiences an increase in metabolic demand, which leads to the production of metabolites such as adenosine, carbon dioxide, and hydrogen ions.

Vasodilation: The metabolites produced in the first step cause vasodilation of the arterioles supplying blood to the tissue or organ, increasing blood flow to the affected area.

Increased oxygen and nutrient delivery: The increased blood flow delivers more oxygen and nutrients to the tissue or organ, supporting its increased metabolic activity.

Decreased metabolite production: As the tissue or organ’s metabolic needs are met, the production of metabolites decreases, leading to a reduction in arteriolar dilation and subsequent decrease in blood flow to the affected area.

Return to baseline: The decrease in blood flow leads to a return to baseline blood flow, ensuring that the tissue or organ receives adequate blood flow without excess.

Question 9

explain Reactive hyperemia’s negative feedback loop

Answer 9

Temporary reduction in blood flow: Blood flow to a tissue or organ is temporarily reduced due to a blockage or constriction of a blood vessel.

Accumulation of metabolic waste products: The reduced blood flow leads to the accumulation of metabolic waste products such as carbon dioxide, adenosine, and hydrogen ions.

Vasodilation: The accumulation of metabolic waste products causes the arterioles supplying blood to the affected tissue or organ to dilate, increasing blood flow to the area once the obstruction is removed.

Increased oxygen and nutrient delivery: The increased blood flow delivers more oxygen and nutrients to the affected area, supporting its metabolic activity.

Metabolic waste product removal: As the tissue or organ’s metabolic needs are met, the accumulation of metabolic waste products decreases, leading to a reduction in arteriolar dilation and subsequent decrease in blood flow to the affected area.

Return to baseline: The decrease in blood flow leads to a return to baseline blood flow, ensuring that the tissue or organ receives adequate blood flow without excess.

Question 10

what is Flow auto-regulation

Answer 10

the ability of certain organs, tissues, or systems in the body to maintain a relatively constant blood flow despite changes in blood pressure or other factors that could affect blood flow

This process allows these organs or tissues to receive a consistent supply of oxygen and nutrients and maintain their normal function.

Important in the kidney and brain

Question 11

how is flow auto-regulation achieved

Answer 11

Myogenic response = reflex response of arterioles to changes in blood pressure

Question 12

explain Flow auto-regulation’s negative feedback loop

Answer 12

A stimulus, such as a change in blood pressure or metabolic activity, affects blood flow to a particular organ or tissue.

This stimulus is detected by sensors, such as baroreceptors or chemoreceptors, located in the blood vessels or tissues.

The sensors send signals to the control center, such as the brain or the local tissue, to initiate a response to the stimulus.

The control center processes the signals and sends out signals to effectors, such as smooth muscle cells in the blood vessels or the heart, to produce a response that counteracts the initial stimulus.

The response of the effectors produces a change in blood flow that opposes the initial stimulus, returning the blood flow to its normal level.

The sensors detect the change in blood flow and send signals to the control center to stop the response, completing the negative feedback loop.

Question 13

Vasoconstriction caused by:

Answer 13

Increase in myogenic activity
Increase O2
Decreased CO2 and other activities
Increased endothelin
Increased sympathetic stimulation

Question 14

Vasodilation caused by:

Answer 14

Decreased myogenic activity
Decrease in O2
Increase in CO2 and other metabolites
Increase in nitric oxide
Decrease in sympathetic stimulation/histamine release

Question 15

what are the 2 ways systemic control of blood occurs

Answer 15

Neural (SNS)
Hormonal:
epinephrine, angiotensin II, and vasopressin are
hormones that influence blood flow in body

Help regulate mean arterial pressure

Question 16

how do Sympathetic nerves affect regulation of blood flow

Answer 16

When sympathetic nerves are activated, they release the neurotransmitter norepinephrine, which binds to adrenergic receptors on smooth muscle cells in the walls of blood vessels.

The binding of norepinephrine to these receptors causes the smooth muscle cells to contract, leading to vasoconstriction, or narrowing of the blood vessels. This reduces blood flow to the affected area and increases blood pressure.

Question 17

Sympathetic Influences on Vasculature:

Answer 17

SNS (norepinephrine)—-> vasoconstriction via α- adrenergic receptors

Epinephrine——-> vasodilation via β-adrenergic receptors