Cardiovascular System Lecture 8

Question 1

What changes as Blood exits capillaries and enters Venules and Veins?

Answer 1

Blood Pressure:
* Minimal pressure; enough for venous return to right atrium of heart.

Total cross-sectional area:
* Branches rejoining – decreasing cross sectional area – lowering resistance.

Velocity of blood flow:
* Increasing as heading back to heart.

Question 2

What is a “blood reservoir”?

Answer 2

volume of blood held in veins and venules

Question 3

What nerves/centers supply Veins and Venules?

Answer 3

The vasomotor center (sympathetic) sends nerve signals to venous system vessels

Question 4

What is “Compliance” in venous blood vessels?

Answer 4

Question 5

In what ways is the Skeletal Muscle Pump altered to return Venous Blood back to the heart? (3)

Answer 5

1. Contracting skeletal muscles create local pressure changes which squeeze compliant venous and increase venous pressure locally.
2. Aid pressure gradient for blood flow back to the heart.
3. Valves to prevent backflow

Question 6

In what ways is the Respiratory Pump altered to return Venous Blood back to the heart? (3)

Answer 6

1. Breathing
   - diaphragm movement creates torso pressure changes.
2. Inspiration:
   - abdominal pressure > thoracic pressure.
   - Pressure changes squeeze compliant venous bv and increase venous pressure in abdominal cavity while lowering venous pressure in thoracic cavity.

This creates a pressure gradient for blood flow back to ♥️

3. Expiration:
   - abdominal pressure < thoracic pressure.
   Pressure gradient reversed, but valves to prevent backflow.

Question 7

In what ways is the Blood Volume altered to return Venous Blood back to the heart?

What Influences this? (2)

Answer 7

Alter blood volume (BV):
Part of MAP – longer term regulation

Influences:
Hormones and Arterial Pressure:
- alter kidney water reabsorption
- alter urinary excretion.

Hypothalamus thirst center
- alter water consumption.

Question 8

where is the vast majority of the blood in the CVS?

Answer 8

61% of blood in the venous system

Question 9

How does an increase in activity/exercise affect the signals sent from the Vasomotor Center? (7)

Answer 9

As Activity Increases,
1. Sympathetic Nerve Signals to Venous Vessels Increases,
2. This Causes Stronger Venoconstriction ->
3. Venous Pressure Increases ->
4. Venous Return Increases ->
5. EDV and SV Increase ->
6. Cardiac Output (Q) increases ->
7. Results in Higher Mean Arterial Pressure

Question 10

How does an increase in activity/exercise affect the Skeletal Muscle Pump and the Respiratory Muscle Pump? (6)

Answer 10

As Activity Increases,
1. Skeletal/Respiratory Muscle Pump Increases,
2. Venous Pressure Increases ->
3. Venous Return Increases ->
4. EDV and SV Increase ->
5. Cardiac Output (Q) increases ->
6. Results in Higher Mean Arterial Pressure

(same effect for both pumps)

Question 11

How do Hormones, Arterial Pressure and the Hypothalamus Thirst Center ultimately affect the venous return?

Answer 11

Increase Water Consumption and Urinary Absorption (decreases urinary secretion),

this increases plasma and blood volume, causing:
- Venous Pressure to Increase
- Venous Return to Increase
- EDV and SV to Increase
- Cardiac Output (Q) to
Results in Higher Mean Arterial Pressure