240923 INTRO TO THE AUTONOMIC NERVOUS SYSTEM

Question 1

What are the two anatomical & functional divisions of the autonomic nervous system and how do they differ?

Answer 1

Sympathetic and parasympathetic nervous systems

While your sympathetic nervous system carries signals that put your body’s systems on alert (“fight or flight”), your parasympathetic carries signals that relax those systems (“rest and digest”).

Question 2

Describe the cyclical homeostatic pathway through which the ANS controls pretty much all bodily functioning

Answer 2

Control Centre (i.e. brain) > [autonomic efferent/outgoing pathway] > Effector System, e.g. heart (alters variable)&raquo_space; Homeostatically controlled variable, e.g. arterial blood pressure&raquo_space; Sensor, e.g. afterial baroreceptors > [sensory/afferent nerve] > (back to Control Centre)

Question 3

How are incoming and outgoing ANS nerves referred to?

Answer 3

Incoming = afferent
Outgoing = efferent

Question 4

Describe the generalised efferent pathway

Answer 4

CNS > [preganglionic neuron] > Autonomic ganglion > [postganglionic neuron] > Target tissue

Question 5

What is an autonomic ganglion?

Answer 5

An autonomic ganglion is a cluster of nerve cell bodies (a ganglion) in the autonomic nervous system. The two types are the sympathetic ganglion and the parasympathetic ganglion.

Question 6

Which organs do the following nerves innervate?
III Oculomotor
VII Facial
IX Glossopharyngeal
X Vagus nerve

Answer 6

III Oculomotor – (eye movements), pupil constriction, lens shape

VII Facial – (facial expression, sensory for taste), tear & salivary glands

IX Glossopharyngeal – (sensory mouth, blood vessel pressure changes, swallowing), parotid salivary gland secretions

X Vagus nerve - supplies thoracic and abdominal organs

Question 7

What is the difference in distribution between the sympathetic and parasympathetic nervous system?

Answer 7

The parasympathetic nervous system has a more restricted distribution that the sympathetic. Some organs/tissues have only sympathetic supply, others have both (i.e. dual control). e.g. no parasympathetic supply to limbs, skin, blood vessels, muscles.

Question 8

What neurotransmitters are used by sympathetic vs. parasympathetic pathways?

Answer 8

Symp pathways use acetylcholine and norepinephrine

Para pathways use acetylcholine

Question 9

Where are the SNS’ preganglionic neurones located?

Answer 9

In the thoracic (T) and upper 2-3 lumbar (L) segments of the spinal cord

Question 10

What factor crucially determines the effect a neurotransmitter has on a tissue?

Answer 10

Which receptors are present

Question 11

What are the 2 ways in which ANS signals are turned off?

Answer 11

enzyme destroys transmitter

transmitter is ‘re-captured’ by presynaptic nerve terminals (carrier/uptake transporter) for re-use or destruction

Question 12

What are the classes and subtypes of receptors for norepinephrine/epinephrine (i.e. noradrenaline/adrenaline) in tissues, and do the subtypes differ in their response to the different subtypes?

Answer 12

The two classes are α (alpha) β (beta). They are G-protein coupled receptors (GPCRs), which are intracellular messengers.

The four subtypes are α-1, α-2, β-1, β-2

NAdr stimulates α Rs more than β Rs whereas Adr stimulates both approximately the same.

Question 13

What is dysautonomia and name a few things that can cause it

Answer 13

inappropriate activation of PNS or SNS.

Can be caused by neurodegenerative diseases, drugs etc.