Regulation of the CVS 1 Flashcards
What is cardiac output?
Volume of blood pumped out of the left ventricle into the aorta per unit time
Cardiac output is a key indicator of heart function and overall cardiovascular health.
What is venous volume?
Volume of blood returned to right atrium per unit time
Venous volume is crucial for understanding the balance between venous return and cardiac output.
In a normally functioning heart, what is the relationship between venous return and cardiac output?
Venous return is equal to cardiac output
This balance is essential for maintaining adequate blood circulation.
What leads to heart failure?
Heart cannot maintain normal cardiac output at normal filling pressures
Heart failure results in under-filling of arterial circulation and can have many causes.
How is cardiac output related to metabolism?
Cardiac output of a normal animal is proportional to the overall metabolism of its whole body
This indicates that higher metabolic rates require greater cardiac output.
What factors can influence cardiac output?
Physiological and pathological factors
Understanding these factors is vital for diagnosing and treating heart conditions.
What is the formula for cardiac output?
Cardiac output = stroke volume x heart rate
This formula highlights the two main components that determine cardiac output.
What determines heart rate in mammals?
Pacemaker cells (SAN)
The sinoatrial node (SAN) is crucial for initiating the heartbeat.
What role does the autonomic nervous system (ANS) play in altering heart rate?
ANS can alter heart rate through sympathetic and parasympathetic innervation
The ANS adjusts heart rate based on the body’s needs.
Which nerve innervates the SA and AV nodes parasympathetically?
Vagus nerve
The vagus nerve decreases heart rate when activated.
What effect does sympathetic innervation have on heart rate?
Increases heart rate
Sympathetic stimulation is associated with ‘fight or flight’ responses.
What is the primary pacemaker of the heart?
Sinoatrial node (SAN)
The SAN sets the rhythm for the heart’s contractions.
How does sympathetic innervation affect action potential generation at the SAN?
Releases noradrenaline, increases action potentials
This leads to a faster heart rate.
True or False: At rest, parasympathetic effects dominate heart rate.
True
This reflects the body’s resting state and energy conservation.
Fill in the blank: Parasympathetic (vagal) innervation releases _______ which binds to muscarinic (M2) receptors.
ACh
Acetylcholine (ACh) slows down the heart rate by reducing action potentials.
What happens to the ‘f’ channels during sympathetic stimulation?
More ‘f’ channels open, leading to faster If
This results in more action potentials per unit time, increasing heart rate.
What effect does parasympathetic stimulation have on ‘f’ channels?
Fewer ‘f’ channels open, leading to slower If
This results in fewer action potentials per unit time, decreasing heart rate.
What is the role of the AV Node in cardiac function?
It serves as a secondary pacemaker under autonomic control.
What neurotransmitter is released by sympathetic innervation at the AV Node?
Noradrenaline
What receptors does noradrenaline bind to in the AV Node?
β1-adrenoreceptors
What effect does sympathetic stimulation have on the AV refractory period?
Decreases AV refractory period
What neurotransmitter is released by parasympathetic innervation at the AV Node?
ACh
Binding of ACh to which receptors increases the AV refractory period?
Muscarinic (M2) receptors
What is myocardial contractility?
A measure of the force generated by cardiac myocytes.
Which myocytes have β1 and some M2 receptors?
Atrial myocytes
What effect does sympathetic innervation have on myocardial contractility?
Increases contractility
How does sympathetic innervation increase contractility?
Ultimately through Ca2+ effects.
What effect does parasympathetic innervation have on contractility?
Decreases contractility
What is preload in cardiac physiology?
Filling pressure of the heart.
What is an indicator of preload in a live animal?
Central venous pressure
What happens to stroke volume when filling pressure is increased?
Stroke volume increases.
What effect does increasing diastolic volume have?
Increasing end diastolic volume increases strength of subsequent systolic contraction.
What is the relationship between venous return and cardiac output?
Venous return equals cardiac output.
List three factors that affect venous return.
- Displacement of blood from veins (sympathetic vasoconstrictor fibers)
- Skeletal muscle contractions
- Changes in intra-thoracic pressure (thoracic pump)
What is afterload?
Resistance to ejection of blood from the heart.
How does increased afterload affect stroke volume and cardiac output?
Decreases both stroke volume and cardiac output.
What must the heart do to maintain cardiac output when faced with increased afterload?
Increase contractility.
True or False: Sympathetic stimulation of myocytes decreases contractility.
False
What is the consequence of a 1% imbalance in right and left ventricular output?
Pulmonary edema due to increased hydrostatic pressure.
What is the primary driving force for blood returning to the heart?
Ventricular contraction.
