Chapter 2: Form and Function Flashcards
Purpose of cardiovascular controller
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)
Sensing components of the cardiovascular controller
- Stretch sensitive nerve endings (arterial baroreceptors)
Location of arterial barorecptors (2)
Embedded in the walls of:
a) the aorta
b) the carotid
Importance of arterial baroreceptors being in this location
Allow the baroreceptors to sense the stretch associated with acute changes in blood pressure
MOA arterial baroreceptors
- 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
Region of the brain that receives imput
Medulla
Effectors of the cardiac controller
-sympathetic and parasympathetic limbs of the ANS
Describe sequence of events if blood pressure goes up acutely
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
Receptors located adjacent to the baroreceptors in the carotid artery and aorta
Chemoreceptors
Chemoreceptors
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)
Other cortical influences on blood pressure
- 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
Importance/repercussion of position of heart
-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
Explanation for difference in thickness of heart muscle on the left and right side
- 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)
High capacitance
Can absorb large changes in blood flow without significantly increasing pressure
Type of blood flow through valves (normally)
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)
Cause of turbulent flow in valvular disease + what hear
- 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
Mechanism of whezing
Turbulent low of airway due to narrowing of airways –> increases the velocity of air flowing through them –> produces turbulence and sound = wheeze
Pericardial sac
- 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)
Attachments of pericardial sac
- outer fibrous layer has physical attachments to the diaphragm and sternum
- helps hold heart in place
Explanation influence of respiration on heart during inspiration
- 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)
- Increased venous return stimulates stretch-sensitive baroreceptors in the heart and the result is an increase in heart rate
Explanation influence of respiration on heart during expiration
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
Sinus arrhythmia
Change in heart rate with respiration
A normal phenomenon
Conduit vessels
- part of the arterial system
- first vessels that carry blood immediately after it leaves the heart
Arterioles
- further downstream
- much smaller (<100 um)
- aka resistance vessles because provide bulk of resistance to flow in circulatory system
