Blood Pressure Flashcards
Blood pressure
Lateral pressure exerted by flowing blood on the walls of the arteries
How is blood pressure determined?
Force with which heart pumps the blood, resistance offered by the vessels ( BP=Cardiac output xPeripheral Resistance)
What is short term control of blood pressure mediated by?
Nervous system - sympathetic and parasympathetic, chemicals - sensitive to changes in pH, O2, and CO2 levels
Why does the nervous system mediate short term blood pressure?
Changes blood distribution in the body and by changing blood vessel diameter. Sympathetic and parasympathetic activity will affect veins, arteries and heart to control HR and force contraction
The Vasomotor center
Cluster of sympathetic neurons found in the medulla, sends efferent motor fibres that innervate moth muscles of blood vessels
Sympathetic activity
Vasoconstriction (fight or flight)
Parasympathetic activity
Vasodilation (rest and digest)
Sympathetic stimulation
Impulses sent from accelerator center and medulla travel along sympathetic fibres.
Primary neurotransmitters; Neurotransmitters that increase the force of ventricular contraction, heart rate, blood pressure, and cardiac output. Norepinephrine, epinephrine
Chronotropic
Affects heart rate
Dromotropic
Enhances conduction velocity
Inotropic
Enhances strength of contraction
Parasympathetic stimulation
Primary neurotransmitter; acetylcholine. Main effect; slowing heart rate. Decreases the strength of contraction and can cause a small decrease in the force of ventricular contraction
What are baroreceptors and where are they found?
Stretch receptors found in carotid sinuses and aortic arch
Baroreceptors
Detect stretch changes in blood pressure, cause a reflex response in either the sympathetic or parasympathetic divisions of the autonomic nervous system
What happens to the Baroreceptor reflex if systolic blood pressure decreases?
Peripheral vasoconstriction, increased heart rate (chronotropic effect), increased myocardial contractility (inotropic effect), increased electrical conduction (dromotropic effect)