Autonomic Reflexes Flashcards Preview

LCRS - Neuroscience - Laz > Autonomic Reflexes > Flashcards

Flashcards in Autonomic Reflexes Deck (9)
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1
Q

What are the main effects of the sympathetic nervous system on the CO = MABP/TPR equation?

A

Sympathetic has an inotropic and chronotropic effect thus SV and HR are increased so CO is increased. Sympathetic firing also causes generalised vasoconstriction so TPR increases.

2
Q

Describe the response to a decrease in blood pressure.

A

Decrease in blood pressure causes a decrease in baroreceptor firing so there is a decrease in the inhibition of the SNS. The SNS activity increases so you get an increase in CO and TPR.

3
Q

Describe the changes that take place when you stand up.

A

Gravity pushes a column of blood towards your toes so the blood pools in the distensible veins. This means that there is less venous return to the heart and so a lower force of contraction (Starling’s Law). This means that there is a drop in blood pressure when you stand up.

4
Q

What causes postural hypotension?

A

Impaired sympathetic nervous system response to transient hypotension

5
Q

Describe the effects of the sympathetic and parasympathetic nervous system on the eye muscles.

A

Sympathetic - contracts radial muscles and dilates the pupil
Parasympathetic - contracts circular muscle and contracts ciliary muscles so you get pupil constriction and lens thickening to allow near vision

6
Q

State two drugs that affect the eye muscles and how they work.

A

Pilocarpine - acetyl choline drug - causes MIOSIS (constriction)
Atropine - blocks the parasympathetic nervous system - causes MYDRIASIS (dilation)

7
Q

Describe the pupillary light reflex.

A

Afferent information goes via the optic nerve to the pretectal nucleus. From here, the impulses travel to the Edinger-Westphal nucleus where there parasympathetic neurons begin. The preganglionic parasympathetic neuron goes to synapse in the ciliary ganglion. There is a short postganglionic neuron that goes to the iris.

8
Q

What is the consensual reflex and what causes it?

A

When you shine a light in one eye, both eyes constrict.

This is caused by the afferent information converging on the pretectal nucleus.

9
Q

If you achieve a direct response in the right eye with no consensual response in the left eye, where does the problem lie?

A

There is a problem with the parasympathetic nerves in the left eye.