cardiovascular compensations

Question 1

what is the heart innervated by

Answer 1

autonomic nervous system

Question 2

what does the sympathetic nervous system arise from

Answer 2

thoracolumbar spinal segments

Question 3

where does the parasympathetic nervous system arise from

Answer 3

brainstem and sacral spinal segments

Question 4

what does the sympathetic NS do in the cv system

Answer 4

acts to increase cardiac output - flight or fight response

Question 5

what does the parasympathetic NS to do the cv system

Answer 5

lowers cardiac output when animals are resting = rest and digest system

Question 6

what does the alpha adrenergic receptor cause

Answer 6

constriction of the arterioles of the non-essential organs and venoconstriction of the abdominal organs to maximise preload to the heart and hence increase cardiac output

Question 7

what does the beta 1 receptor do to the heart

Answer 7

increase cardiac output leading to increased heart rate and conduction, reduced refractory period and stronger cardiac contractions.

Question 8

what is increased during exercise

Answer 8

body’s requirement for oxygen delivery and removal of waste products
heat production by the tissues

Question 9

what are the 5 systems that manage the CVS during exercise

Answer 9

metabolic autoregulation
psychogenic response
exercise reflex
baroreflex
skeletal muscle and respiratory pumps.

Question 10

what happens during metabolic autoregulation

Answer 10

increased skeletal muscle causes vasodilation as metabolic waste products build up in the interstitial fluid.
reduced arterial pressure

Question 11

what happens in psychogenic response

Answer 11

increases sympathetic activity to the heart and decreases parasympathetic activity
increased cardiac output
CO increased further by increased preload (increases SV) as venous return to heart increases due to vasoconstriction in non-essential organs.
vasoconstriction increases TPR

Question 12

what does hypovolaemic mean

Answer 12

decreased volume of circulating blood

Question 13

what causes hypovolaemic shock

Answer 13

haemorrhage
severe dehydration
sequestration of blood

Question 14

what is the CV response to hypovolaemia

Answer 14

baroreflex provides the the first immediate compensations
increase in sympathetic stimulation to the heart causing increased contractility heart rate and conduction speed.
vasoconstriction to the non-essential organs.
venoconstriction of abdominal veins to increase TPR to increase blood available to perfuse essential organs (severe case)
splenic contraction to replace lost volume and cells.

Question 15

why does pulse pressure remain low when CVS is responding to hypovolaemia

Answer 15

due to persistently low stroke volume

Question 16

what activates if hypovolaemia persists

Answer 16

RAAS

Question 17

what are the 2 types of heart failure

Answer 17

forward (systolic) or backward (congestive)

Question 18

what is forward heart failure

Answer 18

failure of the systolic pumping action of the heart resulting in reduced cardiac output and reduced mean arterial pressure

Question 19

signs of forward heart failure

Answer 19

reduced perfusion, slow capillary refill time, pale mucous membranes, weak pulse and cold extremities.

Question 20

presentation of animals with forward heart failure

Answer 20

unable to exercise
weak and lethargic
exhibit vasovagal syncope when under distress. (faint)

Question 21

what is dilated cardiomyopathy (initially presented as forward heart failure)

Answer 21

muscle wall of heart very thin and stretched so ventricles unable to contract properly so SV low.

Question 22

what is backward heart failure

Answer 22

blood backs up in the venous circulation
=heart unable to cope with preload

Question 23

what does backward heart failure cause

Answer 23

increased atrial pressure, increased venous pressure and leakage of fluid into the ISF due to increased hydrostatic pressure in the capillaries.

Question 24

what is mitral valve disease (presented as left-sided CHF)

Answer 24

mitral valve becomes incompetent and allows blood to flow back into the left atrium during ventricular systole.
increases left atrial pressure and reduces pulmonary venous drainage into the atrium which increases pulmonary venous pressure

Question 25

what does left sided CHF lead to

Answer 25

pulmonary oedema causing increased respiratory rate and respiratory difficulty

Question 26

what does right sided CHF lead to

Answer 26

increased systemic venous pressure - distention of jugular veins and enlargement of liver and spleen
fluid leakage leads to effusion

Question 27

what does the body use to compensate for forward heart failure

Answer 27

starlings mechanism, baroreflex and the RAAS