feedback control of cardiovascular system

Question 1

what is blood pressure?

Answer 1

the outwards (hydrostatic) pressure exerted by the blood on blood vessel walls

Question 2

what is Systemic Systolic Arterial Blood Pressure?

Answer 2

the pressure exerted by the blood on the walls of the aorta and systemic arteries when the heart contracts

Question 3

what is Systemic Diastolic Arterial Blood Pressure?

Answer 3

the pressure exerted by the blood on the walls of the aorta and systemic arteries when the heart relaxes

Question 4

what is ideal normal systolic arterial blood pressure?

Answer 4

between 90-120mmHg

Question 5

what is ideal normal diastolic arterial blood pressure?

Answer 5

60-80 mmHg

Question 6

define hypertension

Answer 6

Clinic blood pressure of 140/90 mmHg or higher and day time average of 135/85 mmHg or higher

Question 7

what is pulse pressure?

Answer 7

difference between systolic and diastolic blood pressures

Question 8

what is mean arterial blood pressure (MAP)?

Answer 8

the average arterial blood pressure during a single cardiac cycle, which involves contraction and relaxation of the heart

Question 9

why is MAP value not obtained by simply averaging diastolic and systolic values?

Answer 9

because during a normal cardiac cycle:
The relaxation (Diastolic) portion of the cardiac cycle is about twice as long as the contraction (Systolic) portion of the cardiac cycle

Question 10

what is the formula for MAP value?

Answer 10

[(2xdiastolic) + systolic] divided by 3
OR
diastolic blood pressure + 1/3 of difference between DBP and SBP
OR
Stroke Volume x Heart Rate x Systemic Vascular Resistance
OR
CO x SVR

Question 11

what is normal MAP range?

Answer 11

70-105 mm HG, minimum of 60 mm Hg is needed to perfuse every vital organ

Question 12

why must MAP be regulated in narrow range?

Answer 12

to ensure pressure is high enough to perfuse all vital organs but not too high that it causes damage to blood vessels or puts strain on heart & other organs

Question 13

what are baroreceptors?

Answer 13

they are mechanoreceptors
(sensors) which are sensitive to stretch, they have nerves which take impulses to control centre (aortic arch has high sensitivity baroreceptor)- they detect changes in blood pressure & send signals to brain

Question 14

what are afferent neurons?

Answer 14

also called sensory neurons, are the nerve fibers responsible for bringing sensory information from the outside world into the brain.

Question 15

what do barorecpetors do?

Answer 15

send afferent impulses to Cardiovascular Control Centre in the Medulla of the Brainstem

Question 16

what is nucleus tractus solitarius (NTS)?

Answer 16

The visceral sensory part of the brainstem has a single nucleus found in the medulla oblongata, the nucleus solitarius, which is located lateral to the motor nucleus of the vagus nerve. At the center of the nucleus, a bundle of nerve fibers runs through it to innervate the nucleus, which is the tractus solitarius.
= it’s site of 1st synapse for all CVS (cardiovascular system) afferents in the medulla

Question 17

what does NTS do?

Answer 17

integrates and relays information to other regions that control the pathways of the two divisions (parasympathetic and sympathetic) of the autonomic (“involuntary”) nervous system to heart and blood vessels i.e. helps control involuntary nervous system

Question 18

what is cardiac output?

Answer 18

the volume of blood pumped by each ventricle of the heart per minute

Question 19

how to calculate cardiac output?

Answer 19

Stroke volume (SV) x Heart Rate (HR)

Question 20

what is stroke volume?

Answer 20

the volume of blood pumped by each ventricle of the heart per beat

Question 21

what is systematic vascular resistance?

Answer 21

the sum of resistance of all vasculature in the systemic circulation

Question 22

how could MAP be regulated?

Answer 22

heart rate, stroke volume, systematic vascular resistance

Question 23

what is autorhythmicity?

Answer 23

it’s the hearts capability of beating rhythmically in the ABSENCE of external stimuli (controlled by electric signals from within the heart)

Question 24

what is heart rate modified by?

Answer 24

autonomic nervous system (ANS). involuntary
(sympathetic like noradrenaline, adrenaline, dopamine and parasympathetic like acetylcholine)

Question 25

what does parasympathetic division do to heart rate?

Answer 25

stimulation of the vagus nerve (10th cranial nerve) slows the heart rate (bradycardia). acetylcholine acts on muscarinic (M2) receptors

Question 26

what does sympathetic division do to heart rate?

Answer 26

stimulation accelerates the heart rate (tachycardia). noradrenaline acts on receptors

Question 27

when does stroke volume increase?

Answer 27

when contractile strength of heart increases
-Sympathetic nerves innervate (supply) the ventricular myocardium, and stimulation increases the force of contraction and increases Stroke Volume
-ANS regulates SV

Question 28

what regulates the SVR?

Answer 28

regulated by vascular smooth muscles

Question 29

what is main site of SVR and what regulates it?

Answer 29

arterioles are main site = regulated by vasoconstriction and vasodilation

Question 30

what are vascular smooth muscles supplied by?

Answer 30

SYMPATHETIC nerve fibers. The neurotransmitter is NORADRENALINE acting on B1 receptors

Question 31

what is vaso motor tone?

Answer 31

when Vascular smooth muscles are partially constricted at rest

Question 32

what is vaso motor tone caused by?

Answer 32

by tonic (continuous) discharge of sympathetic nerves resulting in continuous release of noradrenaline