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

sympathetic fibers from the thoracic and lubar regions of the spinal cord; the parasympathetic fibers from the brain and the sacral portion of the spinal cord. sympathetic ganglia lie close tho the spinal cord and form the two chains of ganglia-one on each side fo the cord. celiac 腹部的，腹的 ACh is thethe major neurotransmitter released between pre- and postgangllionic neuronsin autonomic ganglia. 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 CO BP Contractile strength of heart SV 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 cranial nerve

Cardiovascular center cardioacceleratory and cardioinhibitory centers , vasoconstrictor and vasodilator areas located in the medulla within the brain stem. the center alters the ratio between sympathetic and parasympathetic activity to the effector organs.

The cardiovascular reflex Baroreceptor reflex Cardiopulmonary reflex

The baroreceptor reflex includes 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 HR SV and arteriolar and venous vasodilation Sympathetic cardiac nerve activity Sympathetic vasoconstriction nerve activity Parasympathetic nerve activity CO Total peripheral resistance 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 Cardiovasc-ular center HR SV and arteriolar and venous vasoconstriction Sympathetic cardiac nerve activity Sympathetic vasoconstriction nerve activity Parasympathetic nerve activity CO Total peripheral resistance 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 Both common carotid clamp Typical carotid sinus reflex

Vasoconstrictor agents 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)

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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 bradykinin:缓急跆 kallidin：. 胰激肽

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