Lecture 27: The Venous System

Question 1

Is BP higher or lower in the venous system

Answer 1

lower

Question 2

Do veins have a lot of myogenic tone?

Answer 2

Nope

Question 3

Since veins don’t have a lot of myogenic tone?

Answer 3

• Highly stretchable
• Have little elastic recoil
• Easily distend to accommodate add. volumes of blood with only a small increase in venous pressure

Question 4

Venous return

Answer 4

The volume of blood entering each atrium per min from the veins

Question 5

Venous return is influenced by (9)

Answer 5

1. Venous capacity
2. Bulk flow across capillary walls
3. Renin-anggiotensin-aldosterone system (hormones)
4. Sympathetic nervous system
5. Gravity
6. Skeletal muscle pump
7. One way valve
8. Respiratory pump
9. Cardiac suction

Question 6

Venous capacity

Answer 6

Volume of blood the veins can accommodate

Question 7

Venous capacity is influenced by

Answer 7

1. Distensibility of vein walls

2. Externally applied pressure squeezing inwardly on the veins

Question 8

Sympathetic nervous system - Arteriolar vasoconstriction

Answer 8

reduced flow through vessels because of their increased resistance

Question 9

Sympathetic nervous system - Venous constriction

Answer 9

Increases blood flow through these vessels because of their decreased capacity

Question 10

Moving from a lying down to an upright position

Answer 10

1. Decreases the cardiac output
2. Decreases the MAP
3. Sympathetically induces venous constriction

Question 11

The respiratory pump

Answer 11

• During inspiration, there is a decrease in the pressure in the thoracic cavity and an increase in abdominal pressure
• Increase in gradient between abdomen and the thorax forces venous blood from the ab area to the thorax

Question 12

Cardiac suction

Answer 12

• Caused by rapid expansion of the ventricular chambers during ventricular relaxation
• Increases venous return