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