L20 - Sensory regulation of CV

Question 1

Role of CV centre in the brain

Answer 1

• Located in medulla oblongata
• Regulation of heart rate + stroke volume (regulation of cardiac output)
• Control of neural, hormonal + local negative feedback systems – to regulate BP + blood flow to specific tissues
• ANS neurons regulate HR, contractility of ventricles + blood vessel diameter.

Question 2

Cardio-stimulatory centre

Answer 2

Stimulates cardiac function by regulating heart rate and stroke volume via sympathetic stimulation from the cardiac accelerator nerve.

Question 3

Cardio-inhibitory centre

Answer 3

Slows cardiac function by decreasing heart rate and stroke volume via parasympathetic stimulation from the vagus nerve.

Question 4

Vasomotor centre

Answer 4

Controls vessel tone or contraction of the smooth muscle in the tunica media.

• basically control of blood vessel diameter

Question 5

What are the sensory inputs to the CV centre? (afferent)

Answer 5

• From higher brain centres:
• cerebral cortex
• limbic system
• hypothalamus
• Proprioceptors => monitor joint + muscle movement to provide input during physical activity
• Baroreceptors => monitor BP changes + stretch in blood vessel walls
• Chemoreceptors => monitor concentration of various chemicals in blood (acidity via blood CO2 level)

Question 6

What are types of reflexes used in the negative feedback loop?

Answer 6

• Baroreceptor reflexes
• Chemoreceptor reflexes

Question 7

How does the baroreceptor reflex ensure negative feedback loop?

Answer 7

• Baroreceptors (pressure-sensitive) located in internal carotid arteries + other large arteries in neck and chest
• Carotid sinus reflex – regulation of BP in brain
• Aortic reflex – regulation of systemic BP
• ↓ BP => stretch sensed less by baroreceptors => slower rate of impulses to CV centre
• CV centre – ↓ parasympathetic stimulation and ↑ sympathetic stimulation

Question 8

How does the chemoreceptors reflex ensure negative feedback loop?

Answer 8

• Chemoreceptors located close to baroreceptors of carotid sinus (carotid bodies) and aortic arch (aortic bodies)
• Detection of: (leading to sending signal to CV)
• hypoxia (low O2)
• hypercapnia (high O2)
• acidosis (high H+ due to high CO2)
• CV centre - increases sympathetic stimulation causing vasoconstriction + increase in BP
• Chemoreceptors also provide input to respiratory centre to adjust breathing rate.