Lecture 7

Question 1

Overall function of cardiovascular
system and blood flow in
general is affected by

Answer 1

Blood Pressure
Resistance
Venous Return
Velocity and Volume

Question 2

definition blood pressure:

Answer 2

force exerted by circulating blood on the walls of blood vessels

Question 3

Systolic pressure:

Answer 3

BP during ventricular systole

Question 4

Diastolic pressure:

Answer 4

BP during ventricular diastole

Question 5

Normal value:

Answer 5

young adult: 120/75 mm Hg

Question 6

Pulse pressure:

Answer 6

systolic - diastolic

important measure of stress exerted on small arteries

Question 7

Resistance

Answer 7

Factors that determine systemic vascular resistance
Blood viscosity
Vessel length
Radius – subject to change = changes in flow
Laminar flow

Question 8

Venous Return

Answer 8

Pressure gradient 
7-13 mm Hg venous pressure towards heart
venules (12-18 mm Hg) to central venous pressure (~5 mm Hg) 
Gravity drains blood from head and neck
Skeletal muscle pump in the limbs
Thoracic pump (respirator)
inhalation - thoracic cavity expands (pressure ) abdominal pressure , forcing blood upward
central venous pressure fluctuates
2mmHg- inhalation, 6mmHg-exhalation
blood flows faster with inhalation

Question 9

Exercise increases venous return in many ways

Answer 9

heart beats faster, harder - increases cardiac output (CO) and BP
vessels of skeletal muscles, lungs and heart dilate increases flow
increases respiratory rate increases action of thoracic pump
increases skeletal muscle pump

Question 10

Venous pooling occurs with inactivity

Answer 10

venous pressure not enough force blood upward
with prolonged standing, CO may be low enough to cause dizziness or syncope
prevented by tensing leg muscles, activate skeletal m. pump
Jet pilots wear pressure suits

Question 11

It is important to adjust blood flow to organ needs

Answer 11

Flow of blood to

particular organ can be regulated by varying resistance to flow

Question 12

Vasoconstriction of blood vessel smooth muscle is controlled

Answer 12

both by the

autonomic nervous system and at the local level

Question 13

Four factors control arterial flow at the organ level

Answer 13

change in metabolic activity

	- changes in blood flow
	- stretch of arterial smooth muscle
	- local chemical messengers

Question 14

Importance of BP:

Answer 14

is a key factor for providing blood (thus oxygen
and energy) to organs. Systolic pressure must be at least 70 to sustain kidney
filtration and adequate blood flow to the brain

Question 15

Role of Cardiovascular center

Answer 15

Collection of nuclei that affect rate, force, vessel diameter
help regulate heart rate & stroke volume
specific neurons regulate blood
 vessel diameter - sympathetic 
 vasomotor nerves
Signals sent out through vagus 
     (parasympathetic) – 
       lowers heart rate

Question 16

Baroreceptors:

Answer 16

carotid and aortic sinuses sense the blood pressure in the aortic arch and internal carotid then send signal to the vasomotor center in the medulla oblongata
Other information are sent from the hypothalamus, cortex

Question 17

Chemoreceptor Reflexes

Answer 17

activated by hypoxia, hypocapnia, and acidosis are located in the aortic arch and carotid sinus.

Question 18

chemoreceptor reflexes Stimulated during

Answer 18

asphyxia and severe hypotension.

Question 19

chemoreceptor reflexes changes

Answer 19

breathing, and include sympathetic constriction of (mainly skeletal muscle) arterioles and tachycardia resulting indirectly from the increased lung inflation.

Question 20

chemoreceptor reflexes effects help maintain

Answer 20

the blood flow to the brain at arterial pressure too low to activate the baroreceptors.

Question 21

The Kidney

Answer 21

Monitor blood pressure and take corrective action if it should drop.
Leads to a cascade of events eventually producing angiotensin II

Question 22

Angiotensin II

Answer 22

constricts the walls of arterioles closing down capillary beds;
stimulates the proximal tubules in the kidney to reabsorb sodium ions;
stimulates the adrenal cortex to release aldosterone. Aldosterone causes the kidneys to reclaim still more sodium and thus water
stimulates the pituitary to release the ADH

Question 23

The Heart

Answer 23

A rise in blood pressure stretches the atria of the heart, triggers release of atrial natriuretic peptide (ANP).
ANP lowers blood pressure
The effects on the kidney reduce the reabsorption of water = increase flow of urine - the net effect = reduce blood pressure by reducing the volume of blood in the system.

Question 24

The Adrenal Glands

Answer 24

Epinephrine & norepinephrine
increases heart rate & force of contraction
causes vasoconstriction in skin & abdominal organs
vasodilation in cardiac & skeletal muscle

Question 25

Autoregulation of Blood Pressure

Answer 25

Physical changes and chemical mediators that induce responses through vascular smooth muscles in various tissues
Local factors cause changes in each capillary bed
autoregulation is ability to make these changes as needed by demand for O2 & waste removal
important for tissues that have major increases in activity (brain, cardiac & skeletal muscle)
Local changes in response to physical changes
warming & decrease in vascular stretching promotes vasodilation
Vasoactive substances released from cells alter vessel diameter
(K+, H+, lactic acid, NO)
systemic vessels dilate in response to low levels of O2
pulmonary vessels constrict in response to low levels of O2

Question 26

Hypertension

Answer 26

Constriction of arterioles leading to resistance in blood flow and strain on the heart
chronic resting BP > 140/90
consequences
can weaken small arteries and cause aneurysms
Increased heart size, lower blood volume, chest pain

Question 27

Hypotension

Answer 27

chronic low resting BP

caused by blood loss, dehydration, anemia

Question 28

Shock and Homeostasis

Answer 28

Any state where cardiac output insufficient to meet metabolic needs (inadequate cardiac output = not enough O2 to meet metabolic needs)
cardiogenic shock - inadequate pumping of heart
low venous return (LVR) shock - 3 principle forms
1. hypovolemic shock - most common
loss of blood volume: trauma, burns, dehydration
2. obstructed venous return shock
tumor or aneurysm
3.venous pooling (vascular) shock

Question 29

Venous pooling (vascular) shock

Answer 29

long periods of standing, sitting or widespread vasodilation
neurogenic shock - loss of vasomotor tone, vasodilation
causes from emotional shock to brainstem injury

Question 30

Septic shock

Answer 30

bacterial toxins trigger vasodilation and increases capillary permeability

Question 31

Anaphylactic shock

Answer 31

severe immune reaction to antigen, histamine release, generalized vasodilation, increases capillary permeability

Question 32

Signs and Symptoms of Shock

Answer 32

An extremely low blood pressure
Fast but weak pulse
Dizziness, faintness or 
      light-headedness
Moist, clammy skin
Profuse sweating
Unconsciousness
Rapid, shallow breathing 
Chest pain
Blue lips and fingernails