Autonomic reflexes

Question 1

What do baroreceptors do

Answer 1

Senses pressure

Afferent nerve relays the info to the brain to stimulate both parasympathetic and sympathetic nerves

Question 2

How is blood pressure calculated

Answer 2

CO/ total peripheral resistance

Question 3

Describe the control of heart rate at rest

Answer 3

Parasympathetic nerve is activated to slow the heart to 70bpm
Sympathetic nerve is inhibited reducing response
Vagal nerve is dominant

Question 4

Describe the response of baroreceptors to an increase in blood pressure

Answer 4

1. Baroreceptors firing rate increases
2. Larger signal to the CNS
3. parasympathetic nervous system activated much more
4. Sympathetic nervous system inhibited more
5. Heart rate decreases to decreases blood pressure

Question 5

Describe the response of baroreceptors to a decrease in blood pressure

Answer 5

1. Reduced signal from baroreceptors in the brain
2. Less stimulation of the parasympathetic nervous system
3. Less inhibition of the sympathetic nervous system (dominant)
4. Increase in heart rate + vasoconstriction

Question 6

Describe blood pressure in the body while standing up

Answer 6

Usual pressure from cardiac contraction
Effect of gravity on the blood
Pressure is greater below the heart than above

Question 7

What is the usual capillary pressure and when does it change

Answer 7

25-30mm Hg

when standing up another 18mm Hg is added

Question 8

Describe what happens to blood pressure when one stands up

Answer 8

Hydrostatic pressure in the vessels of the leg increases and blood pools in the veins. A volume of protein-free plasma filters out of the capillary and mixes with the interstitial fluid.
Additional pressure due to gravity forces fluid out and so less blood returns to the heart and the heart pumps less blood

Question 9

What are the three goals of the nervous system when blood pressure decreases

Answer 9

Increase cardiac output
Increase total peripheral resistance
Increase blood pressure

Question 10

Describe the pupillary light reflex

Answer 10

Driven by autonomic response of the iris muscle (both sympathetic and parasympathetic) with parasympathetic being dominant.

Question 11

Describe the neurotransmitter release during the pupillary light reflex

Answer 11

Sympathetic - ACh -> NA

Parasympathetic - ACh -> ACh

Question 12

What muscle is innervated in the eye for the light reflex

Answer 12

circular muscle/ sphincter pupillae

Question 13

What is the effect of pilocarpine on the eye

Answer 13

blocks the sympathetic system and stimulates the parasympathetic system causing the pupils to contract

Question 14

What is the effect of tropic amide on the eye

Answer 14

Blocks the parasympathetic nervous system causing pupils to dilate a lot

Question 15

Explain the process involved in the pupillary light reflex

Answer 15

1. Light activates the optic (afferent) nerve - cranial II sensory
2. Receiving the signal in the pretectal nucleus
3. Pre-ganglionic neurone in Edinger-Westphal nucleus
4. Oculomotor nerve (cranial nerve III, motor)
5. Ciliary ganglion
6. Pupil constriction

Question 16

what is the effect of both parasympathetic nerves being activated for the pupillary light reflex

Answer 16

Both eyes respond independent of which optic nerve is activated by light