autonomic reflexed

Question 1

bp =

Answer 1

CO/TPR

Question 2

CO=

Answer 2

HR*force of contraction

Question 3

resting heart rate

Answer 3

70bpm

Question 4

intrinsic rate

Answer 4

100-110bpm

Question 5

what can be inferred by the difference between resting and intrinsic heart rate

Answer 5

autonomic ns is controlling rate

PNS influence - because resting is lower than intrinsic and pns reduces heart rate

Question 6

what does the atrial baroreceptor do

Answer 6

sense pressure and relay it to the brain by afferent nerve
brain determines level of autonomic activation
activates the PNS
inhibits the SNS

Question 7

describe the signals in the normal baroreceptor response

Answer 7

signal generated in response to pressure 
sent to brain (afferent nerve) 
PNS proportionately activated 
SNS inhibited 
at rest - PNS is dominant

Question 8

what happens to the baroreceptor reflex when the blood pressure increases

Answer 8

firing signal increases
increase PNS stimulation 
Increase SNS inhibition 
greater -ve effect on the heart
reduce HR 
bring CO down 
normalise bp

Question 9

what happens to the baroreceptor reflex when the blood pressure decreases

Answer 9

reduced signal down the afferent nerve 
reduced PNS activation 
reduced SNS inhibition - becomes dominant 
increase HR 
vasoconstrict to increase TPR

Question 10

what is a major daily problem for blood pressure

Answer 10

moving from lying to standing

Question 11

what contributes to the pressure in a standing position

Answer 11

usual pressure from cardiac contraction

effect of gravity pushing the column of blood down

Question 12

when standing what dos pressure depend on

Answer 12

where in the body
eg in foot 25mmHg from heart plus 80mmHg because of gravity - total of 105mmHg
ih heart bp 120/80, above is lower because the blood is pushed down, belwo is lower because trying to get blood back to heart

Question 13

describe the bp when lying down

Answer 13

it is the same across the whole body

Question 14

affect of standing on veins

Answer 14

increased hydrostatic pressure in bv of legs
veisn expand - distension
increased blood in the venous system
reduced blood in arteries - reduce arterial pressure (which is just bp)
this is blood pooling

Question 15

what is the effect of increased hydrostatic pressure in leg vessels

Answer 15

more fluid forced out of the vessels and into the tissues by the additional pressure from gravity

Question 16

why does standing cause a hypotensive effect

Answer 16

more venous distension and capillary fluid loss
so smaller venous return and by the Starling mechanism small CO because smaller EDV and so contractility of the heart
therefore drop in bp so CO reduced

Question 17

how does the body attempt to increase CO

Answer 17

from the thoracic and lumbar spinal levels the sympathetic neurons are activated
NA is released at the NMJ as a NT
adrenaline is released from adrenal medulla - has a hormonal effect on heart - adrenoreceptors
increase heart rate an force of contraction

Question 18

relationship between adrenaline and NA

Answer 18

similar

but NA gets about by the bloodstream

Question 19

how does the body attempt to increase TPR

Answer 19

the sympathetic nerves from the thoracic and lumbar spinal levels innervate bv (and adrenal medulla which releases adrenaline that acts on the bv)
increase vasoconstriction
increase TPR
increases BP

Question 20

summarise the baroreceptor reflex from changing posture

Answer 20

gravity force blood to pool in legs 
less venous return 
lower CO 
lower arterial pressure 
reduced firing by barorecepotors 
increased sympathetic activity 
reduced parasympathetic activity 
increase contractility and HR 
vasoconstriction - improves venous return, contract veins to return blood

Question 21

what happens if you have postural hypotension

Answer 21

baroreceptor reflex normally kick in quickly - so you don’t notice the hypotesion
but in postural hypotension reflex not working properly, bp remain low, don’t get enough perfusion to the brain because autonomic doesn’t work effectively. baroreceptors respond but ANS doesn’t work

Question 22

how does the body compensate for postural hypotension

Answer 22

if perfusion of the brain is ineffective, the brain switches off - faint
this removes the effect of gravity so the Bp can return to normal

Question 23

what is in control of the iris muscle

Answer 23

the autonomic system

Question 24

where is th postganglionic neuron in the eye

Answer 24

it is part of the PNS

goes around the iris and controls the pupil

Question 25

affect of PNS being switched on, on the pupil

Answer 25

constricts

Question 26

effect of pilocarpine

Answer 26

act like ACh

pupil constricts

Question 27

effect of tropicamide

Answer 27

block PNS

massive dilation

Question 28

what is the normal effect of the PNS on the pupil

Answer 28

keeps it mildly constricted

Question 29

describe the papillary light reflex

Answer 29

light activates the optic nerve - afferent nerve
signal received in the pretectal nucleus - kick starts the efferent nerve
synapse in the Edinger Westphal nucleus to oculomotor nerve which travels into the ciliary ganglion (parasympathetic)

Question 30

effect of the oculomotor nerve being activated by light

Answer 30

pupil constricts

Question 31

effect on other eye to the one stimulated by light

Answer 31

both pupils constrict

optic nerve activates both parasympathetic nerves

Question 32

clinical benefit of both eyes constricting

Answer 32

can detect lesions

Question 33

what is the fact that both eyes called

Answer 33

consensual light reflex

Question 34

if light in R eye, R eye constrict L eye doesn’t where is the problem

Answer 34

efferent supply to L eye

Question 35

if shine in R, nothing in R AND shine in L and response in both where is the problem

Answer 35

r optic nerve