regulation of the cardiovascular activity -- nervous regulation -- humoral regulation --...

Regulation of the cardiovascular activity

-- Nervous regulation

-- Humoral regulation

-- Autoregulation

Nervous regulation

• The role of nervous regulation : -- redistributing of blood flow

-- increasing of heart activity -- providing very rapid control of arterial

pressure

-- realized by autonomic nervous system

Anatomy of sympathetic and parasympathetic nervous control of the circulation

Autonomic nervous system • Sympathetic nervous system

• sympathetic innervation of the blood vessels

-- small arteries and arterioles: increase the resistance decrease the blood flow

-- vein: increase the venous return

• sympathetic innervation of the heart -- artium and ventricles : increasing the heart activity

Sympathetic stimulation

Heart

Heart rate

Contractile strength of heart

SV

CO BP

arterioles vasoconstriction Total peripheral resistance

BP

vein Vasocon-striction

Venous return

SV CO BP

Summary of the effects of the sympathetic nervous systems on cardiovascular system

Autonomic nervous system

• Parasympathetic nervous system• parasympathetic innervation on the atrium• -- control the heart rate

Cardiovascular center

• A collection of functionally similar neuron that help to regulate the HR, SV and blood vessel tone

Cardiovascular center

cardioacceleratory and cardioinhibitory centers , vasoconstrictor and vasodilator areas

The cardiovascular reflex

• Baroreceptor reflex

• Cardiopulmonary reflex

Baroreceptor reflex

• The baroreceptor reflex includes

• Receptor • Afferent pathway

• An integrating center• Efferent pathway• Effector organs

Baroreceptor reflex

• Receptor: carotid sinus and aortic arch baroreceptors, they are mechanoreceptors

• Sensitive to the stretching of vessel wall (not directly to the blood pressure change)

• Afferent pathway: for carotid sinus (Hering’s nerve) for aortic arch baroreceptors (vagus nerve)

Location of the arterial baroreceptors

Afferent pathway: for carotid sinus (Hering’s nerve)for aortic arch baroreceptors (vagus nerve)

Baroreceptor reflex

• Baroreceptor continuously generate AP in response to the ongoing pressure within the arteries (constantly provide information about BP to the center)

• BP increase, the receptor potential of the Baroreceptor increase, the rate of firing in the afferent neurons increase

Firing rate in the afferent neurons from the carotid sinus baroreceptor in relation to the magnitude of mean arterial pressure

Baroreceptor reflex

• The integrating center : cardiovascular control center (cardioacceleratory and cardioinhibitory centers , vasoconstrictor and vasodilator areas) located in the medulla within the brain stem

• The efferent pathway : the autonomic nervous system (sympathetic nerve and parasympathetic nerve)

• Effectors : heart and blood vessels

Reflex pathway

The process of baroreceptor reflex• When arterial pressure becomes elevated above normal

BP becomes above normal

Carotid sinus and aortic arch receptor potential

Rate of firing in afferent nerves

Cardiovasc-ular center

Sympathetic cardiac nerve activity

Sympathetic vasoconstriction nerve activity

Parasympathetic nerve activity

HR

SV

and arteriolar and venous vasodilation

CO

Total peripheral resistance

Blood pressure decreased toward normal

The process of baroreceptor reflex

• When arterial pressure becomes below normal

BP becomes below normal

Carotid sinus and aortic arch receptor potential

Rate of firing in afferent nerves

Cardiovasc-ular center

Sympathetic cardiac nerve activity

Sympathetic vasoconstriction nerve activity

Parasympathetic nerve activity

HR

SV

and arteriolar and venous vasoconstriction

CO

Total peripheral resistance

Blood pressure increased toward normal

baroreceptor reflex

• The feature: 1. sensitive to stretching of vessels wall 2. firing rate is directly proportional to the extend

of stretch 3. response to BP ranging from 60 - 180 mm Hg 4. receptor within the aortic arch are less sensitive

than the carotid sinus receptor

•The significance: Maintenance of the relatively constant of blood pressure

• If clamp both common carotid ,how does BP change?

Typical carotid sinus reflex

Humoral regultaion

• Vasoconstrictor agents

• Vasodilator agents

1. Renin - angiotensin system

1. Renin - angiotensin system

Juxtaglomerular cell

renin

nephron

Physiological role of Angiotensin

(NE )

2. Epinephrine and norepinephrine

• Epinephrine : adrenal medulla binding toβ1 and β2 receptor (usage: strengthening the heart activity)

• Norepinephrine : adrenal medulla and sympathetic nerve terminal binding the α receptor (usage: increasing the BP)

+++ －

3.Vasopressin (antidiuretic hormone, ADH)

4. Atrial natriuretic peptide (ANP)

• Physiological role : produces natriuresis and diuresis

－ Decrease renin release

－ Reduce total peripheral resistance via vasodilatation

－ Decreases HR, CO

5. Kinin and Histamine• Bradykinin, Kallidin– plasma• Histamine – mast cells

Similar effects:• Causes vasodilatation• Increases capillary permeability

Autoregulation • Definition: intrinsic ability of an organ to maintain a c

onstant blood flow despite changes in perfusion pressure, independent of any neural or humoral influences

• Possible mechanism:

-- myogenic mechanism -- metabolic mechanism