Week 1- Autonomic Nervous System

Question 1

What is the autonomic nervous system?

Answer 1

A subdivision of the peripheral nervous system, not under conscious control, controls heart, smooth muscle, internal organs and skin

Question 2

How does the autonomic nervous system work?

Answer 2

Via visceral motor effects which can be parasympathetic or sympathetic: both part of EFFERENT arm of nervous system

Question 3

What does the parasympathetic system do?

Answer 3

Rest and digest ie routine maintenance/ basal control

TIP: P for potato couch

Question 4

What does the sympathetic system do?

Answer 4

Fight or flight ie mobilisation and increased metabolism

TIP: S for Spider-Man

Question 5

How do parasympathetic and sympathetic work together?

Answer 5

They innervate the same tissue but often have opposing effects

Question 6

What do the parasympathetic and sympathetic do to the pupil?

Answer 6

Sympathetic: dilates it to allow as much visual info to come in as possible
Parasympathetic: constricts pupils

Question 7

What do the parasympathetic and sympathetic do to the stomach?

Answer 7

Parasympathetic: increases motility and secretions
Sympathetic: decreases motility

Question 8

How does autonomic control affect blood vessels?

Answer 8

Only sympathetic nerves, they can both dilate and constrict vessels as they go to different receptors

Question 9

What are baroreceptors and what do they do during high/low BP?

Answer 9

They measure blood pressure in blood vessels, sending info to the brain.
High BP: high parasympathetic activity to reduce BP, negatively affects sympathetic nervous system
Low BP: Baroreceptors fire a lot less, less signal to brain, less parasympathetic stimulation and less surpression of sympathetic

Question 10

What is the main integrating center of the autonomic nervous system?

Answer 10

The hypothalamus (receives all the signals)

Question 11

Where are visceral motor neurons found?

Answer 11

They project to the brainstem or spinal chord where they synapse with autonomic neurons

Question 12

What is the structure of autonomic neurons?

Answer 12

There are 2 neurons: pre ganglionic and post ganglionic neuron
PNS: longer pre fibers, shorter post
SNS: short pre, long post

In both cases, pre ganglionic fibres are close to or embedded within effector tissues

Because sympathetic responses are a lot more co ordinated so pre ganglionic synapse near spine

Question 13

What is the exception to the two neuron rule?

Answer 13

The adrenal gland- there is just one nerve, no pre or post, adrenal gland almost acts as the post

Question 14

What neurotransmitters are involved?

Answer 14

Acetylcholine is released from: pre ganglionic parasympathetic, pre ganglionic sympathetic, post ganglionic parasympathetic

Noradrenaline is released from: post ganglionic sympathetic

Difference in release from post ganglionic is why para and symp work differently

Question 15

How does the adrenal gland work?

Answer 15

Secretes a hormone (adrenaline) not a neurotransmitter, into bloodstream not synapse

Question 16

What is the enteric nervous system?

Answer 16

Has a lot of influence on gut function, more than parasympathetic and sympathetic systems

Question 17

How does the lung work?

Answer 17

Only receives parasympathetic neurones, sympathetic function is carried out via a hormone (adrenaline release causes dilation)

Question 18

What is the micturition reflex?

Answer 18

Controls the bladder- parasympathetic innervates the detrusor muscle (during constriction forces urine out of the bladder) and sympathetic innervates the sphincter muscle (stops urine flowing out of bladder). As urine fills bladder, the pressure increases and this is relayed to the brain so parasympathetic increases and sympathetic falls

Question 19

What type of receptor would you want at an autonomic ganglia?

Answer 19

Acetylcholine receptor and a receptor that mediates a v fast response- use an ion channel linked receptor

Question 20

What receptors are required post ganglion?

Answer 20

There are new neurotransmitters e.g. noradrenaline for sympathetic so we need a G protein coupled receptor (much slower in response and gives more control) either muscarinic (for acetylcholine) or adrenergic (for noradrenaline).

Question 21

How are neurotransmitters produced?

Answer 21

1. A precursor (often from diet) is enzymatically covered to transmitter
2. Packaged into vesicles
3. Ca 2+ influx causes release

Question 22

How are neurotransmitters removed?

Answer 22

1. Metabolise transmitter in synapse

2. Remove via transport protein then break it down

Question 23

How is acetylcholine removed from synapses?

Answer 23

Acetylcholinesterase metabolises ach and breakdown products are taken to glial cells (if enzyme is blocked there is over accumulation/stimulation)

Question 24

How is noradrenaline produced?

Answer 24

Tyrosine is converted to DOPA (by tyrosine hydroxylase) then to dopamine (by DOPA decarboxylase), this is packed into vesicles with dopamine beta hydroxylase allowing it to become noradrenaline

Question 25

How is noradrenaline removed from synapses?

Answer 25

1. Can be taken into presynaptic terminal via transport proteins and converted by mono-amine oxidase
2. Taken into glial cell and converted via COMT

Question 26

How would adrenaline have an effect?

Answer 26

4 enzyme conversions to create it, released directly into blood then removed by adrenal gland from bloodstream