38 - . Control of circulation. Localization and characteristics of receptors. Vasomotor centre. Supramedular control of circulation.

sections

blood flow

short term regulation

long term regulation

baroreceptors

chemoreceptor

vasomotor centre

important areas in vasomotor centre

blood flow

• Blood flow through tissues is needed for delivery of oxygen, nutrients, and hormones, to carry away metabolic waste products.

• long-term homeostasis requires that the quantity of blood flow to a particular tissue is precisely matched to and does not unnecessarily exceed its metabolic and functional requirements.

• Some organs receive blood flow but is in excess of its own metabolic needs- however such volume is required for further specialised functions.

short term regulation

• Short-term changes in blood flow is achieved by arterioles and pre capillary sphincters found further upstream the capillary bed

• By contracting or dilating,

long term regulation

• Long-term increases or decreases in blood flow are usually the result of changes in tissue vascularity.

• changes in vasculature are coordinated by complex networks of growth factors.

baroreceptors

• stretch receptors in the walls of the carotid sinus

• regulation of arterial blood pressure

• produces vasoconstrictor activity tonically, which accounts for vasomotor tone.

chemoreceptor

• Are located near the bifurcation of the common carotid arteries and along the aortic arch.

• are very sensitive to hypoxia.

• Sends info to the vasomotor area of the brain

vasomotor centre

• The vasomotor centre is organised into different parts.

• One is Located in medulla and one in pons

• This centre transmits parasympathetic impulses through the vagus nerves to the heart

• transmits sympathetic impulses through the spinal cord and peripheral sympathetic nerves to virtually all arteries, arterioles, and veins.

important areas in vasomotor centre

• The vasomotor center in the medulla controls blood vessel tone and blood pressure.

It has three main areas:

1. Vasoconstrictor area

   • Sends signals through the spinal cord to activate sympathetic preganglionic neurons, causing vasoconstriction.

2. Vasodilator area

   • Inhibits the vasoconstrictor area, leading to vasodilation.

3. Sensory area

   • Gets input from the vagus and glossopharyngeal nerves (from baroreceptors).

   • Sends signals to control both vasoconstrictor and vasodilator areas.

   • Involved in reflex control of blood pressure (e.g., baroreceptor reflex).

Role of the medulla in cardiovascular function:

• Sends constant (tonic) excitatory signals to sympathetic neurons.

• Integrates cardiovascular reflexes.

• Processes input from higher brain areas (supramedullary networks), hormones, and drugs.

• These higher centers include the limbic system, amygdala, and hypothalamus.

• They adjust heart and vessel responses based on emotions and behavior.