cardiovascular week 2 Flashcards
What is the function of the arterial system?
to distribute blood from the heart to the capillary beds throughout the body
What are the three types of arteries?
elastic
muscular
arterioles
Describe elastic arteries
major distributing vessels including the aorta, brachiocephalic trunk, common carotid and subclavian arteries and most of the large pulmonary arterial vessels
Describe muscular arteries
main distributing branches of the arterial tree - radial, femoral, coronary and cerebral arteries
Descrive arterioles
the terminal branches of the arterial tree which supply the capillary beds
Describe the general trends in the structure of arteries
there is a gradual transition in structure and function between the three types of arterial vessel rather than an abrupt demarcation.
In general, the amount of plastic tissue decreases as the vessels become smaller and the smooth muscle component assumes relatively greater prominence
What is blood pressure?
the force exerted by the blood against any unit area of the vessel wall
What does blood pressure depend on?
cardiac output X total peripheral resistance
Describe the roll of the autonomic nervous system of controlling BP
the sympathetic is most important in controlling circulation
the parasympathetic contributes importantly to regulation of heart function
What does innervation of the small arteries and arterioles allow?
sympathetic stimulation to increase resistance to blood flow to the tissues
What does the innervation of the large vessels (particularly veins) allow?
sympathetic stimulation decreases the volume of the vessels. This can push more blood to the heart
what action does the sympathetic NS have on the heart?
increased heart rate and contractility
What action does the parasympathetic NS have on the heart?
decreased heart rate and contractility
Where is the vasomotor centre located?
bilaterally mainly in the reticular substance of the medulla and the lower third of the pons
Where are parasympathetic impulses carried?
Through the vagus nerve
Where are sympathetic impulses carried?
through the spinal cord and peripheral sympathetic nerves to virtually all arteries, arterioles and veins of the body
What is sympathetic vasoconstrictor tone?
continuous partial constriction of the blood vessels
What role does the hypothalamus have on regulating BP?
it can exert powerful excitrory or inhibitory effects on the vasomotor centre
Simulation of the motor cortex, for example, excites the vasomotor centre
What effect does sympathetic stimulation have on the adrenal medullae?
causes the medullae to secrete both adrenaline and noradrenaline into the circulating blood.
What are the actions of adrenaline and noradrenaline?
they act directly on all blood vessels, usually to cause vasoconstriction.
In a few types of tissue adrenaline causes vasodilation because it also has a beta adrenergic receptor stimulatory effect, which dilates rather than constricts certain vessels
How is blood pressure raised rapidly?
most arterioles of the systemic circulation are constricted, which greatly increases the TPR
The veins are especially strongly constricted to displace blood back to the heart, thus increasing the volume of blood in the heart chambers. the stretch of the heart then causes the heart to pump with increasing force and increases arterial pressure.
Strong sympathetic stimulation also increases heart rate and contractility of the heart, thereby increasing cardiac output and therefore increasing BP.