Download realized by autonomic nervous system

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
Heart rate
Sympathetic
stimulation
Heart
arterioles
vein
Vasoconstriction
CO
Contractile
strength of heart
SV
vasoconstriction
Total peripheral
resistance
Venous
return
SV
CO
BP
BP
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)
stem
located in the medulla within the brain
• 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
Cardiovascular center
HR
Sympathetic cardiac nerve activity
SV
Sympathetic vasoconstriction nerve activity
and arteriolar and
venous vasodilation
CO
Total peripheral resistance
Parasympathetic nerve activity
Blood pressure decreased
toward normal
The process of baroreceptor reflex
BP becomes
below normal
Carotid sinus and aortic
arch receptor potential
Rate of firing in
afferent nerves
Cardiovascular center
HR
Sympathetic cardiac nerve activity
SV
Sympathetic vasoconstriction nerve activity
and arteriolar and
venous vasoconstriction
CO
Total peripheral resistance
Parasympathetic nerve activity
Blood pressure increased toward
normal
• When arterial pressure becomes below 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
constant blood flow despite changes in perfusion
pressure, independent of any neural or humoral
influences
• Possible mechanism:
-- myogenic mechanism
-- metabolic mechanism