Phsiology Flashcards
What is blood pressure?
Blood pressure is the outwards pressure exerted by blood on the wall of the blood vessel
What is Systolic and Diastyolic blood pressure?
Systolic - The pressure that blood exerts on the aorta and systemic arterial walls during a contraction of the heart ( < 140 mm Hg )
Diastolic - the pressure on the walls of the aorta and systemic arteries during the relaxation of the heart ( < 90 mmHg)
What is the Systemic Arterial Blood pressure?
Systolic / Diastolic
What is the Mean Arterial Blood Pressure?
The average arterial blood pressure during a single cardiac cycle ( contraction and relaxation of the heart)
It is calculated by MAP = (2D + S) / 3
What is the normal range for MAP?
70 - 105 mmHg
Must be over 60 to allow blood to perfuse brain, heart and kidneys
What is pulse pressure?
The difference between systolic and diastolic blood pressure. Should between 30-50 mmHg and is an important indicator that someone may be in shock
What are Baroreceptors?
A type of mechanoreceptor that act as sensors in the negative feedback mechanism for the regulation of blood pressure. The most important are the baroreceptors located in the carotid sinus and the aorta.
How do Baroreceptors work?
Baroreceptors are sensitive to changes in arterial blood pressure. They can cause the wall of the aorta to passively relax or expand in response to a change in blood pressure. When the MAP rises they increase their firing rate
How does the control centre for the cardiovascular system work?
The NTS recieves CVS afferent information as it is the site of the 1st synapse in the medulla. The information supplied will be relayed to other areas of the brain e.g hypothalamus. Activity in the NTS can regulate vagal (parasympathetic) outflow to the heart and regulate spinal sympathetic neurons.
What is the cardiac output, stroke volume and heart rate?
Cardiac Output- The volume of blood pumped by each ventricle of the heart in one minute
Stroke Volume - The volume of blood pumped by each ventricle of the heart per beat
Cardiac Outpute = Stroke Volume X Heart Rate
What is the Systemic Vascular Resistance?
The sum of all resistance of vasculature in the systemic circulation
What can regulate MAP?
Heart rate, stroke volume and systemic vascular resistance
What is the Autonomic nervous system?
The Autonomic nervous system is the involuntary nervous system. It is split into tqo divisions the Sympathetic and Parasympathetic
How can the Sympathetic Nervous System regulate a change in blood pressure?
It can accelrate the haert rate (tachycardia)
It can innervate the ventricular myocardium and stimulate an increase in the force of contraction which increases stroke volume
Decreased sympathetic discharge can cause vasodilation (decreases SVR and MAP) and increased sympathetic discharge can cause vasoconstriction (incraesing SVR and MAP)
What is the Vasomotor tone?
The tonic discharge of sympathetic nerves resulting in a continour release of noradrenaline
