Chapter 2: Form and Function

Question 1

Purpose of cardiovascular controller

Answer 1

Maintain blood pressure and flow at a homeostatic level (a level sufficient to supply the body’s needs under various conditions of activity and posture)

Question 2

Sensing components of the cardiovascular controller

Answer 2

1. Stretch sensitive nerve endings (arterial baroreceptors)

Question 3

Location of arterial barorecptors (2)

Answer 3

Embedded in the walls of:

a) the aorta
b) the carotid

Question 4

Importance of arterial baroreceptors being in this location

Answer 4

Allow the baroreceptors to sense the stretch associated with acute changes in blood pressure

Question 5

MOA arterial baroreceptors

Answer 5

• change in stretch in blood vessel due to increased pressure of blood on them
• change in stretch transduced into a change in firing frequency of the nerves within the baroreceptors which are then relayed to the brain for processing

Question 6

Region of the brain that receives imput

Answer 6

Medulla

Question 7

Effectors of the cardiac controller

Answer 7

-sympathetic and parasympathetic limbs of the ANS

Question 8

Describe sequence of events if blood pressure goes up acutely

Answer 8

1)Stretch receptors activated
2) Send signal to brain
3) Brain increases the activity of the PSNS and decreases the activity of the SNS
Net result:
-slowing of HR
-less forceful contraction of heart muscle
-dilation or widening of arteries
Leading to a fall in the resistance to flow in blood vessels throughout the body (systemic vascular resistance) are restoration of elevated blood pressure to normal levels

Question 9

Receptors located adjacent to the baroreceptors in the carotid artery and aorta

Answer 9

Chemoreceptors

Question 10

Chemoreceptors

Answer 10

Specialized nerve sensors
Monitor:
a) partial pressure of O2 and CO2 in blood
b) blood pH
-key component n control of respiratory system (just as baroreceptors are controllers of the cardiovascular system)

Question 11

Other cortical influences on blood pressure

Answer 11

• mediated via the cortical and/or limbic structures
• hypothesis that psychological stress (transformed at higher cortical levels to a neurological signal sent to the cardiovascular controller) can lead to a sustained increase in bp

Question 12

Importance/repercussion of position of heart

Answer 12

-located to the left of the midline and more anterior than posterior (closer to the sternum than the vertebrae)
Importance:
1) sternum and ribs can protect the heart
2) Afffects the filling of the heart /how much work must do to pump oxygenated blood: chest wall moves with each breath = changes in pleural pressure which is transmitted to great vessels and heart –> cyclical swings in pressure alter flow of blood from the vessels outside the thorax to those inside the chest

Question 13

Explanation for difference in thickness of heart muscle on the left and right side

Answer 13

• pulmonary circuit into which right ventricle pumps = high capacitance and low resistance
• systemic circuit = high capacitance (requires higher pressure to pump and consequently more muscular)

Question 14

High capacitance

Answer 14

Can absorb large changes in blood flow without significantly increasing pressure

Question 15

Type of blood flow through valves (normally)

Answer 15

Laminar blood flow
-all molecules of the liquid moving in paths parallel to the direction of flow (should not hear any sound made by this type of flow)

Question 16

Cause of turbulent flow in valvular disease + what hear

Answer 16

• valves dysfunctional (too narrow, too stiff, or too floppy)
• blood flow becomes turbulent - molecules move in paths at angles to the direction of flow
• turbulent blood produces a vibration leading a murmur

Question 17

Mechanism of whezing

Answer 17

Turbulent low of airway due to narrowing of airways –> increases the velocity of air flowing through them –> produces turbulence and sound = wheeze

Question 18

Pericardial sac

Answer 18

• tri-layered sac surrounding the heart
  1) Fibrous pericardium (outer layer)
  2) Parietal pericardium (middle layer)
  3) Serous or visceral pericardium (layer closest to the heart)

Question 19

Attachments of pericardial sac

Answer 19

• outer fibrous layer has physical attachments to the diaphragm and sternum
• helps hold heart in place

Question 20

Explanation influence of respiration on heart during inspiration

Answer 20

1. When intrathoracic pressure becomes more negative during inspiration, the return of venous blood to the right side of the heart increases (drawn in by the more negative intrathoracic pressure relative to the positive pressure n the extremities and abdomen or pushed in by the higher intra-abdominal pressure)
2. Increased venous return stimulates stretch-sensitive baroreceptors in the heart and the result is an increase in heart rate

Question 21

Explanation influence of respiration on heart during expiration

Answer 21

The volume of the chest wall decreases and the intrathoracic pressure becomes greater (less negative)
The stimulus is removed and the heart rate returns to its normal level

Question 22

Sinus arrhythmia

Answer 22

Change in heart rate with respiration

A normal phenomenon

Question 23

Conduit vessels

Answer 23

• part of the arterial system

- first vessels that carry blood immediately after it leaves the heart

Question 24

Arterioles

Answer 24

• further downstream
• much smaller (<100 um)
• aka resistance vessles because provide bulk of resistance to flow in circulatory system

Question 25

Compliance of arteries vs. veins

Answer 25

Veins have a greater compliance relative to arteries of a comparable size

Question 26

Meaning of compliance

Answer 26

Can hold on to a lot of blood without causing pressure to rise significantly in the vessel

Question 27

Consequence of relationship between left side of the heart and pulmonary veins

Answer 27

Pulmonary veins form a direct connection between pulmonary capillaries in the lung and the left atrium of the heart into which they empty
Clinical consequences = if pressure in the left atrium is elevated then will be felt by pulmonary veins and pulmonary capillaries
Under pressure fluid can leave the capillaries and enter the air sacs =pulmonary edema

Question 28

Valves in veins

Answer 28

• unidirectional valves
• present in veins located anatomically below heart level but not in those returnin blood from structures above heart level (do not have to contend with gravity!)

Question 29

Clinical consequences absence of valves in veins of head

Answer 29

Increases risk of infection spreading from outside to inside the cranial cavity via the blood stream

Question 30

Reason why there is decreased resistance to flow in the pulmonary circulation

Answer 30

• shorter length of the vascular tree
• high compliance of the vessels
• vasular recruitment

Question 31

Vascular recruitment in the pulmonary circulation

Answer 31

-at rest most of blood pumped from heart goes to the base of the lungs
-with exercise/conditions that increase the amount of blood pumped each minute these unfilled vessels in the upper zones of the lung are recruited (now receive blood)
By bringing new bv into the circ under conditions of high flow the overall resistance of the pulmonary circulation remains low

Question 32

Function of lymph vessels

Answer 32

To remove fluid that leaks out of the capillaries int the interstitial space and return it to the veins

Question 33

Relation flow through the coronaries and cardiac cycle

Answer 33

-small branches of coronary arteries within heart muscle
-arteries supplying the left ventricle are squeezed shut when the heart muscle contracts
Therefore left ventricle receives arterial blood flow primarily during relaxation
Consequently during tachycardia heart may not receive enough oxygen