Physio: Special Circulations 1 & 2

Front 1

As a human begins to exercise, do each of the following increase or decrease:
A. cerebral blood flow
B. coronary blood flow
C. skeletal muscle blood flow
D. skin circulation
E. splanchnic circulation
F. renal circulation

Back 1

Cerebral blood flow = no change (stays pretty steady)
Coronary blood flow, skeletal m., skin circulation = increase
Splanchnic and renal circulations = decrease

Front 2

True or False:
The intact autonomic nervous system appears to play a large role in coronary blood flow regulation when compared with local, metabolic factors.

Back 2

False!

Metabolic factors play a much larger role than ANS when it comes to regulation of coronary flow!

Front 3

True or False:
Histological studies have confirmed that adrenergic nerves innervate the coronary vessels.

Back 3

True.
Furthermore, there are both alpha and beta receptors in coronary blood vessels.
p. 367

Front 4

The dominant factor that controls coronary blood flow appears to be the ________ of the myocardium.

Back 4

metabolic rate.
increase in metabolic activity = increase in coronary blood flow
(per metabolic hypothesis!)
p. 368

Front 5

Coronary blood flow is closely linked to the metabolic needs of the myocardium with oxygen and adenosinen playing key roles in the chain of events that bring about blood flow regulation. What other vasodilator substances , though not as potent, have been considered? (3)

Back 5

H+, K+, prostaglandins.

p. 368

Front 6

Regarding the anatomy of the brain for cerebral circulation, blood is supplied to the brain by which two arteries?

Back 6

carotid artery (feeds the circle of Willis) and the basilar artery (feeds the vertebral arteries)
p. 368

Front 7

The capillaries of the brain have a unique feature. What is this feature and what's it referred to as?

Back 7

The walls of brain capillaries exhibit a low permeability that prevents the passage of most substances. This is called the blood-brain barrier. Gases and certain nutrients can pass with little difficulty.
p. 368

Front 8

Regarding regulation of cerebral blood flow's neural/ extrinsic control, maximal stimulation of the sympathetic nerves reduces CBF by...

A. 5-10%
B. 10-15%
C. 15-20%

Back 8

A. 5-10% .... very minimal! The cerebral veins also receive a sympathetic nerve supply and constrict 10-20% at max stimulation. Parasympathetic fibers elicit only a modest repsonse. Thus, more research is needed to determine functional importance of the ANS in regulating cerebral blood flow. p. 369

Front 9

The rate of cerebral blood flow is regulated primarily by the concentration of ________ in cerebral tissues.

A. carbon dioxide
B. metabolites
C. oxygen

Back 9

A. carbon dioxide

Small increases in CO2 = marked vasodilation and increase in CBF!
p. 369

Front 10

True or False:
Research shows that changes in CO2, rather than CO2 itself, lead to changes in pH in the fluid that bathes the vessels and it is this change in pH that elicits alterations in smooth muscle tone.

Back 10

True.

p. 369

Front 11

Research shows that changes in CO2, rather than CO2 itself, lead to changes in ______ in the fluid that bathes the vessels and it is this change that elicits alterations in smooth muscle tone.

Back 11

changes in pH!

p. 369

Front 12

Hypocapnia causes a(n) [ decrease / increase ] in cerebral blood flow ; hypercapnia causes a(n) [ decrease / increase ] in cerebral blood flow.

Back 12

Hypocapnia --> decrease in CBF

Hypercapnia --> increase in CBF

p. 370

Front 13

Carbon dioxide is carried in blood 3 ways. Name them and the respective breakdown by percentage.

Back 13

Dissolved: 5%
Bound: 5%
HCO3 - : 90%

notes, p. 370

Front 14

True or False:
Alterations in the normal O2 tension of arterial blood never cause significant changes in CBF since cerebral is regulated by [carbon dioxide] in the cerebral tissues.

Back 14

FALSE IN WHOLE. Yes, [CO2] is what the CBF rate is regulated by primarily, and usually small O2 tension changes don't do much, but if PO2 drops dramatically ( <50 mmHg) , CBF increases dramatically.
p. 370

Front 15

True or False:
In the intact animal, the effects of hypoxia are felt to be less pronounced than effects of CO2 on the CBF.

Back 15

True. This is due to the hyperventilation following hypoxia that in turn results in hypocapnia. Hypocapnia would inhibit the vasodilatory actions of hypoxia.
p. 371

Front 16

In both coronary circulation and cerebral circulation, autoregulation occurs over a wide range of arterial blood pressure, _____________.

Back 16

60-180 mmHg
p. 371

Front 17

Regarding skeletal muscle circulation anatomy, small arteries enter muscles and subsequently branch into smaller vessels called arterioles, of which there are two groupings based on size. What are those?

Back 17

> 50 micrometers in diameter = flow-controlling arterioles
<25 micrometers in diameter = arterioles that determine the # of capillaries with blood flow
p. 372

Front 18

Capillaries have an average diameter of ____ micrometers and tend to become slightly [ larger / smaller ] at the venular end ( ____ micrometers).

Back 18

4.7 micrometers , larger, 5.9 micrometers
p. 372

Front 19

Sympathetic fibers innervate most of the arterial network of skeletal muscle. The smooth muscle cells have two diff receptor types. Name them and their respective effects.

Back 19

alpha and beta2-adrenergic receptors.
alpha receptor causes constriction , beta2 receptor causes dilation.
p. 373

Front 20

What happens to blood vessels when an alpha-adrenergic blocking agent like phentolamine is administered?

Back 20

The vasodilator influence of beta2- receptors goes unmasked and vasodilation occurs. (Normal response of blood essels to sympathetic activity NE is generally vasoconstriction since alpha receptor's vasoconstriction overpowers beta2's effect.) p. 374

Front 21

[ Phentolamine / Propranolol ] is an alpha-adrenergic blocking agent; [ Phentolamine / Propranolol ] is a beta2-adrenergic blocking agent.

Back 21

Phentolamine is alpha (vasoconstricting) -blocking; propanolol is beta2 (vasodilating)- blocking
p. 374

Front 22

Name the alpha-adrenergic blocking agent and the beta2-adrenergic blocking agent.

Back 22

Alpha = phentolamine
Beta2 = propanolol
p. 374

Front 23

True or False:
Blood flow through skeletal muscle is autoregulated in the pressure range between 20-160 mmHg.

Back 23

True
p. 374

Front 24

True or False:
For local/intrinsic control of skeletal muscle blood flow, the myogenic mechanism is the mechanism responsible for the maintenance of blood flow despite changes in perfusion pressure.

Back 24

FALSE. It is not exactly known for sure though it seems likely that both myogenic and metabolic hypothesis hold true fairly equally and when the ratio of metabolism:flow is high, the metabolic mechanism seems to dominate. p. 374

Front 25

In resting skeletal muscle, a decrease in the arterial perfusion pressure leads to [ constriction / dilation ] of the arterioles.

Back 25

Dilation!
Interestingly, this dialtion can be abolished if more oxygen is supplied to the muscle. These results suggest that hypoxia plays an integral role in the autoregulatory response. p. 374

Front 26

In exercising skeletal muscle, the local increase in blood flow is caused by three simultaneous factors. Name em.

Back 26

- Amount of O2 decreases leading to a switch from oxidative metabolism of glucose to glygolytic degradation of glucose to lactic acid. Lactic acid changes pH in tissue that results in relaxation of vasculature.
- ATP --> ADP --> Adenosine, potent vasodilator
- exercising skeletal muscle cells release large quantities of K+ into extracellular fluid upon excitation of the cell membrane. K+ acts as vasodilator.
p. 375

Front 27

Circulatory apparatus of the skin is characterized by two major vessel types: (1) usually nutritive arteries, capillaries and veins and (2) ________.

Back 27

extensive subcutaneous venous plexus (holds large quantities of blood that can heat the surface of the skin) and in feet, hands, lipds, nose and ears, arteriovenous anastomoses exist.
p. 375

Front 28

True or False:
Subcutaneous venous plexus and arteriovenous anastomoses serve in the regulation of body temperature by conducting heat from the internal structures of the body to the skin.

Back 28

TRUE. p. 376

Front 29

Blood flow through the skin is principally regulated by [ local regulation / the nervous system ].

Back 29

the nervous system.
The principal function of blood flow thru skin is to control body temperature. The control center doing so is located in the anterior hypothalamus. p. 377

Front 30

The control center for body temperature is located
A. anterior hypothalamus
B. anterior thalamus
C. cerebellum
D. midbrain

Back 30

A. anterior hypothalamus

is where the temperature control is located
p. 377

Front 31

Vasoconstriction of skin blood vessels is brought about by stimulation of sympathetic vasoconstrictor fibers which release _____ .

Back 31

Norephinephrine.
p. 377

Front 32

When the body becomes overheated, sympathetic input is greatly [ increased / reduced ] and blood flow to the skin is greatly increased.

Back 32

reduced!
p. 377

Front 33

Regarding the response of skin to trauma, when the skin is stroked firmly with a pointed object, what three local reactions (termed "the triple response") occur?

Back 33

1. a red line (caused by local damage to tissue, release of histamines from damaged cells)
2. a red flare (develops in 20-40 seconds after trauma and is caused by an axon reflex
3. a raised wheal (up to 1 cm on each side of line within 1 minute of injury) p. 377-8