T3: Circulatory System (cont.)

Question 1

What is the normal blood flow rate of humans?

Answer 1

5L/min

Question 2

What is the vital function of the cardiovascular system?

Answer 2

Chemical and gaseous exchange between blood and interstitial fluid.

across capillary walls

Question 3

What is the function of capillaries?

Answer 3

transport gases, nutrients and waste products.

Question 4

What are the three types of capillaries?

Answer 4

• continuous
• fenestrated
• discontinuous

Question 5

What is the function of continuous capillaries?

Answer 5

• permit diffusion of water, small solutes and lipid soluble materials into the surrounding interstitial fluid
• prevent the loss of blood and plasma cells

Question 6

What is the function of fenestrated capillaries?

Answer 6

Exchange of water and solutes (as large as small peptides) between plasma and interstitial fluid.

Question 7

Where are continuous capillaries located?

Answer 7

all tissues except:
- epithelia
- cartilage

Question 8

Where are fenestrated capillaries located?

Answer 8

• Kidneys: glomerulus
• GI tract: gut

Question 9

Where are sinusoidal capillaries located?

Answer 9

• liver
• bone
• spleen
• endocrine glands (pituitary, adrenal glands)

Question 10

What is microcirculation comprised of?

Answer 10

• arterioles
• capillaries
• venules
• terminal lymphatic vessels

Question 11

What is a precapillary sphincter? What is its function?

Answer 11

• a circular band of smooth muscle at the entrance to the capillary
• regulates number of perfused capillaries

Question 12

How do substances pass through the capillary wall?

Answer 12

• diffusion (O2, CO2)
• filtration
• osmosis

Question 13

What is fluid movement across capillary walls determined by?

Answer 13

• hydrostatic pressure
• osmotic pressure

Question 14

What is an arteriovenous anastomose? What is its function?

Answer 14

• direct connections between arterioles and venules
• allows blood to bypass the capillary bed and flow directly into the venous circulation

Question 15

What is the function of capillary beds?

Answer 15

allow gas, nutrient and waste exchange

Question 16

What is the function of arterioles (in relation to capillaries)?

Answer 16

• regulate capillary hydrostatic pressure
• influence capillary fluid exchange

Question 17

How do venules play a role in regulating capillary hydrostatic pressure?

Answer 17

Sympathetic innervation of larger venules can alter venular tone which plays a role in regulating capillary hydrostatic pressure.

Question 18

What is the function of valves?

Answer 18

• keep blood flowing towards the heart
• allow blood flow against the force of gravity

Question 19

What is the colour of blood flowing through veins? Why?

Answer 19

deep red colour <– lacks oxygen

Question 20

What is turbulance?

Answer 20

The upset of smooth blood flow caused by:
- high flow rates,
- irregular surfaces
- sudden changes in vessel diameters
which increases resistance and slows the flow of blood.

Question 21

Where does turbulance usually occur?

Answer 21

• between atria and ventricles
• between ventricles and the aortic/pulmonary tunk
• aorta (high flow rates)
• small vessels (unless the wall is damaged–>plaque –> restricts blood flow)

Question 22

Is arterial pressure stable?

Answer 22

No!
- rises during ventricular systole
- falls during ventricular diastole

Question 23

What is a pulse?

Answer 23

The rhythmic pressure oscillation that accompanies each heartbeat.

Question 24

What is pulse pressure?

Answer 24

The difference between systolic and diastolic pressures.

Question 25

What is used to report a single blood pressure value?

Answer 25

a MAP (mean arterial pressure)

Question 26

What is hypertention?

Answer 26

abnormally high blood pressure

Question 27

What is hypotention?

Answer 27

abnormally low blood pressure

Question 28

What instrument is used to measure blood pressure?

Answer 28

**sphygmomanometer** (around arm)

Question 29

What factors are involved in the regulation of cardiovascular function?

Answer 29

- **local factors** (AUTOREGULATION: **chemical** changes in interstitial fluid) - **neural mechanisms** (*pressure* changes or blood *gas* level changes) - **endocrine mechanisms** (releases *hormones* enhancing short term adjustments and direct long term changes)

Question 30

What is autoregulation? What does it cause?

Answer 30

causes immediate, localized homeostatic adjustments

Question 31

State examples of factors promoting autoregulation.

Answer 31

- decreased O2 levels - increased CO2 levels - generation of lactic acid - release of nitric oxide (known as EDRF) - increased K+ - increased H+ - release of histamine - elevated local temperatures | EDRF- endothelium derived relaxation factor

Question 32

What neural centers are responsible for regulatory activities of the cardiac output?

Answer 32

*Medulla Oblongata*: - **cardiac** centers - **vasomotor** centers

Question 33

What does each cardiac center consist of? What are they innervated by?

Answer 33

- cardioacceleratory center (sympathetic innervation) - cardioinhibitory center (parasympathetic innervation)

Question 34

What does the neurotransmitter norepinephrine (NE) cause?

Answer 34

- stimulation of smooth muscle cells (arteriole walls) - vasoconstriction

Question 35

What neurotransmitter causes vasoconstriction?

Answer 35

norepinephrine (NE)

Question 36

How do vasodilator neurons function?

Answer 36

- innervate blood vessels in skeletal muscles and brain - stimulation of vasodilator neurons relaxes smooth muscle cells (arteriole walls)

Question 37

What is vasodilation triggered by?

Answer 37

appearance of NO in the surroundings

Question 38

What are the most common vasodilator synapses? What do they release? What does it cause?

Answer 38

**Cholinergic**: - releases *ACh* - *ACh* stimulates *NO* release - local vasodilation achieved **Nitroxidergic**: - release *NO* - local vasodialtion

Question 39

What do baroreceptor reflexes respond to?

Answer 39

changes in blood pressure

Question 40

What do chemoreceptor reflexes respond to?

Answer 40

changes in the chemical composition of arterial blood

Question 41

What are baroreceptor and chemoreceptor reflexes regulated through?

Answer 41

negative feedback loop

Question 42

Where are baroreceptors involved in cardiovascular regulation located?

Answer 42

- carotid sinuses (regulate blood flow to the brain) - aortic sinuses (regulate blood flow through the systematic circuit)

Question 43

What happens when blood pressure falls below normal?

Answer 43

- cardiac output increase (stimulation of heart sympathetic innervation) - widespread peripheral vasoconsriction (stimulation of sympathetic vasoconstrictor neurons (by vasomotor centers))

Question 44

What is the function of the antidiuretic hormone (ADH)?

Answer 44

- stimulates water conservation at the kidneys - prevents a reduction in blood volume (which would reduce blood pressure)

Question 45

What is the function of the angiotensin II?

Answer 45

- stimulates ADH secretion, Na+ retention, K+ loss, aldosterone production - stimulates thirst (increased fluid consumption) - stimulates cardiac output - triggers vasoconstriction of arterioles **Elevates systemic blood pressure.** - 4-8x more than norepinephrine

Question 46

What does venous return depend on?

Answer 46

- skeletal muscle action - respiratory movements - constriction of smooth muscle in venous walls

Question 47

Compare the "laminar" and "turbulent" blood flow.

Answer 47

Laminar flow is linear flow, mainly found in the middle of the vessel. Turbulent flow is any disruption in the laminar flow.