• Ca2+ influx , [Ca2+ ]i , contractility
Cardiac effect of parasympathetic stimulation
Interaction of sympathetic and parasympathetic nerves
Predominance of autonomic nerves
sympathetic constrictor nerve, vagus nerve • Effector: heart & blood vessels
Baroreceptor neurons function as sensors in the homeostatic maintenance of MAP by constantly monitoring pressure in the aortic arch and carotid sinuses.
Cardiovascular Center
A collection of functionally similar neurons that help to regulate HR, SV, and blood vessel tone
Vasomotor center
Located bilaterally mainly in the reticular substance of the medulla and of the lower third of the pons
180 mmHg ➢Receptors within the aortic arch are less
sensitive than the carotid sinus receptors
The action potential frequency in baroreceptor neurons is represented here as being directly proportional to MAP.
Cardiovascular Physiology
Regulation of Cardiovascular Activities
Lecture Outline
•Nervous Regulation •Humoral Regulation •Autoregulation
Nervous Regulation
• If , phase 4 spontaneous depolarization, autorhythmicity
• Ca2+ influx , phase 0 amplitude & velocity , conductivity
• Ca2+ influx , Ca2+ release , [Ca2+ ]i , contractility
– Vasoconstrictor area – Vasodilator area – Cardioinhibitor area – dorsal nuclei of the
vagus nerves and ambiguous nucleus – Sensory area – tractus solitarius
Asymmetrical innervation of sympathetic nerve
Cardiac mechanisms of acetylcholine
Mechanisms of acetylcholine —increase K+ & decrease Ca2+ permeability
Baroreceptor Reflexes
• Arterial baroreceptors – Carotid sinus receptor – Aortic arch receptor
• Afferent nerves (Buffer nerves) • Cardiovascular center: medulla • Efferent nerves: cardiac sympathetic nerve,
Innervation of cardiovascular system
Nervous regulation of the circulaephrine
Mechanisms of norepinephrine
—increase Na+ & Ca2+ permeability
• K+ outward , |MRP| , phase 4 spontaneous depolarization , autorhythmicity
• Inhibition of Ca2+ channel, phase 0 amplitude & velocity , conductivity
Characteristics of baroreceptors:
➢Sensitive to stretching of the vessel walls ➢Proportional firing rate to increased
stretching ➢Responding to pressures ranging from 60-
Vasomotor center
Higher cardiovascular centers
– Reticular substance of the pons
– Mesencephalon – Diencephalon – Hypothalamus – Cerebral cortex – Cerebellum
i.e., MAP is above
homeostatic set point
i.e., reduce cardiac output
Baroreceptor neurons deliver MAP information to the medulla oblongata’s cardiovascular control center (CVCC); the CVCC determines autonomic output to the heart.