short term control of BP

Question 1

how is MAP calculated

Answer 1

MAP = CO x TPR

Question 2

what can occur is MAP is too low

Answer 2

syncope

Question 3

what can occur if MAP is too high

Answer 3

hypertension

Question 4

where are the arterial baroreceptors located

Answer 4

aortic arch
carotid sinuses
carotid arteries

Question 5

what type of receptors are the baroreceptors and what do they detect

Answer 5

mechanoreceptors

arterial wall stretch –> activation of receptors

Question 6

which nerve to the carotid sinus baroreceptors travel in

Answer 6

glossopharyngeal

Question 7

which nerve to the aortic arch baroreceptors travel in

Answer 7

vagus

Question 8

where do the nerves in the baroreceptor reflex synapse and what happens in this area

Answer 8

medullary cardiovascular centre
looks at info from baroreceptors, MAP
controls firing rate of parasymp/symp nerves if MAP gets too high/low

Question 9

parasympathetic aspect of baroreceptor reflex

Answer 9

via vagus nerve 
innervates SAN 
release of ACh to act on muscarinic receptors 
pacemaker cells reach threshold later
reduced HR

Question 10

sympathetic aspect of baroreceptor reflex (HR)

Answer 10

innervate SAN 
release of NA onto beta 1 receptors
modification of ion channels 
quicker depolarisation of pacemaker cells 
increased HR

Question 11

adrenal medulla involvement in baroreceptor reflex

Answer 11

release of adrenaline
binds to B1 receptors
increased HR

Question 12

veno and arteriolar constriction in baroreceptor reflex

Answer 12

sympathetic innervation of vessels
NA acts on alpha 1 receptors
increased contraction of smooth muscles
altered TPR and VR to heart

Question 13

sympathetic aspect of baroreceptor reflex (myocardium)

Answer 13

NA and adrenaline bind to B1
increased Ca coming in from outside and released from SR
more cross bridges
increased strength of contraction 
increased SV and BP

Question 14

short term control of BP can be via

Answer 14

baroreceptor reflex
posture
valsalva manoeuvre

Question 15

how is BP controlled in the long term

Answer 15

revolves around blood vol
sensed by cardiopulmonary baroreceptors
effects tend to be hormonal and act on blood vessels and kidneys

Question 16

name 5 inputs to the medullary cardiovascular centres

Answer 16

cardiopulmonary baroreceptors
arterial baroreceptors
chemoreceptors in the muscle 
joint receptors
higher centres

Question 17

cardiopulmonary baroreceptors feedback effect

Answer 17

in the walls of the vessels in the heart and lungs
mainly in low pressure areas
activated by increased blood vol and increased BP

Question 18

central chemoreceptors feedback effect

Answer 18

detect blood [CO2]
increase RR if CO2 conc becomes too high
stimulate increased SV and increased HR when activated

Question 19

chemoreceptors in the muscle feedback effect

Answer 19

respond to [K] and low pH (increased metabolic rate)
stimulated during exercise
more blood sent to these areas

Question 20

joint receptors feedback effect

Answer 20

detect movement in the joints and are activated

allows more blood to be sent to these areas

Question 21

higher centres and medullary CV centre

Answer 21

feed forward effect

consciousness tells medullary CV centres to increase HR

Question 22

what is the effect of standing on blood in the legs

Answer 22

increased hydrostatic pressure

pooling of blood in veins/venules of the feet/legs

Question 23

what effect does posture have on MAP and why

Answer 23

reduced VR
reduced EDV
reduced preload
reduced SV
reduced CO 
reduced MAP (less efficient cross bridge formation, reduced strength of contraction, less blood in arteries)

Question 24

what effect does posture have on baroreceptor firing

Answer 24

reduced MAP
reduced baroreceptor firing rate
lack of AP sent to medullary CV centre indicates reduced MAP

Question 25

reflex response to posture

Answer 25

reduced vagal tone, increased HR and CO
increased sympathetic tone, increased HR and CO
increased contractility, increased SV and CO
increased venoconstriction, VR, EDV, SV, CO
increased arteriolar constriction, increased TPR

Question 26

what is the valsalva manoeuvre

Answer 26

forced expiration against a closed glottis

Question 27

how does the valsalva manoeuvre affect MAP

Answer 27

increased thoracic pressure transmitted through to aorta
increased thoracic pressure results in reduced VR, EDV, SV, CO, MAP
reduced MAP detected by baroreceptors (initiate reflex, increase CO, TPR)

Question 28

how does MAP change when the valsalva manoeuvre is stopped

Answer 28

reduced thoracic pressure transmitted through to aorta
VR restored
increased SV
reflex effects not yet worn off