Physiology of Circulation Study Guide

Question 1

How does blood flow along a pressure gradient?

Answer 1

Blood flows from high to low pressure against resistance
(always moves DOWN the pressure gradient)

Question 2

Blood flow

Answer 2

the volume of blood flowing through a vessel, organ, or circulation system in a period of time - remains fairly constant, and relatively equivalent to CO

Question 3

Blood pressure

Answer 3

the force per unit area exerted on a vessel wall by the contained blood, typically measured in the largest arteries near the heart
- The hydrostatic pressure gradient – the difference in blood pressure within the vascular system – provides the driving force to keep blood moving

Question 4

Resistance

Answer 4

opposition to flow, the amount of friction that blood encounters
- Most friction is encountered well away from the heart – total peripheral resistance (TPR)

Question 5

3 sources of resistance

Answer 5

blood viscosity, vessel length, and vessel diameter

Question 6

source of resistance that is the most important in determining blood flow

Answer 6

Vessel diameter is the most important in determining blood flow because a change in diameter = a change in TPR, the more the resistance increases, the more the blood flow decreases (resistance occurs as a result of the diameter decreasing / vice versa)

Question 7

How blood pressure differs in arteries, capillaries, and veins

Answer 7

Blood pressure in the arteries is highest, followed by the capillaries, and lastly the veins

Question 8

In the process of moving from the aorta to the right atrium, where does blood pressure decrease the most?

Answer 8

The arterioles – resistance is highest here

Question 9

average blood pressure in the right atrium

Answer 9

0mmHg

Question 10

Systolic blood pressure

Answer 10

blood is expelled into the aorta, the walls are stretched, aortic pressure peaks (average = 120 mmHg)

Question 11

Diastolic blood pressure

Answer 11

aortic walls recoil, aortic valve closes, and pressure drops (average = 80 mmHg)

Question 12

Pulse pressure

Answer 12

the difference in systolic and diastolic pressure (Increased SV and contractility can temporarily increase PP, Atherosclerosis chronically increases pulse pressure)

Question 13

Mean arterial pressure (MAP)

Answer 13

the pressure that propels blood into the tissues – useful tool for determining tissue perfusion

Question 14

Why is MAP not just SBP averaged with DBP

Answer 14

Because diastole lasts longer than systole, MAP is NOT simply the halfway point between SBP and DBP (both MAP and pulse pressure decrease as you get further from the heart)

Question 15

Sounds of Korotkoff

Answer 15

heard when taking blood pressure, typically measured in the brachial artery, when a practitioner uses a sphygmomanometer and a stethoscope to listen to them. These sounds detect SBP and DBP

Question 16

What is it more difficult for blood to make its return trip to the heart via the veins?

Answer 16

The blood flowing through veins has to fight against gravity, and the pressure in veins is much less than arteries

Question 17

3 functional adaptations for assisting blood to return to the heart via the veins

Answer 17

• Muscular pump (skeletal muscles squeeze veins and propel blood to heart)
• Respiratory pump (breathing causes pressure changes in ventral cavity that propels blood to heart)
• Sympathetic vasoconstriction (during SNS firing veins constrict, venous volume is reduced, and blood goes toward heart)

Question 18

relationships between CO, TPR, and blood volume

Answer 18

• Blood Pressure (BP) varies directly with CO and TPR
• Anything that increases CO or TPR will increase BP
• Anything that increases HR or SV will increase BP
• Any change that threatens BP homeostasis will be compensated for

Question 19

Baroreceptors

Answer 19

pressure-sensitive mechanoreceptors that respond to changes in arterial pressure and stretch, whose inputs are integrated into the cardiovascular center of the medulla oblongata. The outputs travel via autonomic fibers to the heart and the vascular smooth muscle
- Ex – rising arterial BP activates baroreceptors in the carotid sinuses, aortic arch, and walls of nearly every large artery of the head and neck. They will then send impulses to the cardiovascular center – cardioinhibitory center is stimulated; vasomotor and cardioacceleratory centers are inhibited
- Orthostatic hypotension is a failure of the baroreceptor reflex

Question 20

Chemoreceptors

Answer 20

receptors that respond to changes in levels of CO2, H+, and O2 in the blood. They stimulate the cardioacceleratory center to increase CO and the vasomotor center to increase vasoconstriction when: CO2 level rises, pH level falls, O2 level falls. Located close to baroreceptors, the most prominent chemoreceptors are the carotid bodies and the aortic bodies. They also play a role in regulating respiratory rate

Question 21

Higher brain centers

Answer 21

modify arterial pressure via relays to the brain stem – like fight or flight response, redistribution of blood flow by the hypothalamus
- Reflexes regulating blood pressure are integrated into the medulla oblongata of the brain stem – the cerebral cortex and hypothalamus are not involved in routing regulation of BP

Question 22

Cardiovascular center

Answer 22

• cardioacceleratory center – sympathetic
• Cardioinhibitory center – parasympathetic
• Vasomotor center: transmits impulses along sympathetic efferent fibers called vasomotor fibers, which exit the spinal cord and innervate the smooth muscle of the blood vessels – mainly arterioles
• Increased sympathetic activity will cause vasoconstriction and raise BP, decreased sympathetic activity will decrease vasodilation and lower BP

Question 23

Vasomotor tone

Answer 23

arterioles are almost always moderately constricted resulting in a baseline vasomotor tone

Question 24

Epinephrine/Norepinephrine

Answer 24

released in response to stress, enhance sympathetic response by increasing CO and promoting vasoconstriction

Question 25

Angiotensin II

Answer 25

Renin (generates angiotensin II) is released by the kidneys when blood pressure or volume are lowk, promotes intense vasoconstriction to rapidly increase blood pressure, stimulates release of ADH and Aldosterone, which both participate in longer term BP regulation

Question 26

Atrial Natriuretic Peptide (ANP)

Answer 26

produced by the atria of the heart to reduce blood volume and pressure, antagonizes aldosterone, promotes vasodilation, stimulates excretion of sodium and water

Question 27

Antidiuretic Hormone (ADH)

Answer 27

also called vasopressin, produced by the hypothalamus, stimulates the kidneys to conserve water and widespread vasoconstriction

Question 28

neural methods of short term regulation of blood pressure

Answer 28

baroreceptors, chemoreceptors, brain’s cardiovascular centers, vasomotor tone, effects of higher brain centers

Question 29

hormonal methods of short term regulation of blood pressure

Answer 29

Epinephrine, norepinephrine, renin, angiotensin II, ADH, aldosterone, and ANP.

Question 30

long term regulation of blood pressure

Answer 30

renal mechanisms (direct and indirect)

Question 31

Direct renal mechanism

Answer 31

when BV or BP rise, fluid is filtered from the bloodstream to the kidneys more rapidly -> increased urine -> decreased BV and BP (opposite also occurs)

Question 32

Indirect renal mechanism

Answer 32

when BP declines, kidneys release enzyme renin into blood, renin splits the plasma protein angiotensinogen to make angiotensin I, angiotensin I is converted to angiotensin II by angiotensin converting enzyme (ACE) , ACE is found in the capillary endothelium of various body tissues – especially the lungs

Question 33

The 4 actions of Angiotensin II

Answer 33

• Stimulates the adrenal cortex to secrete aldosterone
• Stimulates the pituitary gland to secrete ADH
• Triggers the sensation of thirst
• Vasoconstriction to increase TPR

Question 34

Hypertension (HTN)

Answer 34

chronically elevated blood pressure – SBP > 130 mmHg, DBP > 80 mmHg, strains heart and damages the blood vessels

Question 35

Hypotension

Answer 35

blood pressure < 90/60 mmHg, usually harmless / healthy
Can be a sign of serious underlying condition:
- Addison’s disease
- Hypothyroidism
- Severe malnutrition

Question 36

Primary hypertension

Answer 36

hypertension without a specific cause, environmental factors that contribute to it are:
- Heredity, diet, obesity, age, diabetes mellitus, stress, and smoking
- Can be controlled with improved diet, exercise, -stopping smoking, managing stress, and taking anti HTN meds
- HTN meds include diuretic, beta blockers, calcium channel blockers, ACE inhibitors, and angiotensin II receptor blockers

Question 37

Secondary Hypertension

Answer 37

less common, has identifiable cause –
- Obstructed renal arteries
- Kidney disease
- Endocrine disorders – hyperthyroidism or cushing’s disease

Question 38

dangers of prolonged hypertension

Answer 38

major cause of heart failure, vascular disease, renal failure, and CVA

Question 39

dangers of prolonged hypotension

Answer 39

Circulatory shock – blood vessels are filled inadequately; blood cannot circulate normally – body tissues are not adequately perfused

Question 40

3 types of circulatory shock

Answer 40

Hypovolemic Shock
Vascular Shock
Cardiogenic Shock

Question 41

Hypovolemic Shock

Answer 41

blood volume is too low
- Results from large scale blood or fluid loss
- HR will increase in response to a dramatic drop in blood volume
- Intense vasoconstriction will shift blood out of reservoirs
- Treatment: replace fluid volume ASAP

Question 42

Vascular Shock

Answer 42

blood volume is normal; poor circulation because of extreme vasodilation and lost TPR
- Anaphylactic: lost vasomotor tone in response to an allergic reaction
- Neurogenic: failure of the autonomic nervous system
- Septic: severe systemic bacterial infection

Question 43

Cardiogenic Shock

Answer 43

pump failure
- Results from extensive myocardial damage – an inefficient heart