Autonomic Nervous System

Question 1

What is the difference between somatic and autonomic?

Answer 1

Somatic = voluntary 
Autonomic = automatic

Question 2

What is different about the enteric system compared to the sympathetic and parasympathetic systems?

Answer 2

It can function fairly independently

Question 3

Generally, what happens in the autonomic nervous system?

Answer 3

Neuronal fibres leaving the CNS make a synapse in the autonomic ganglion. Postganglionic neurons send these fibres to the target tissues

Question 4

Is it the PNS or SNS that is responsible for fight or flight situations?

Answer 4

SNS

Question 5

What neurotransmitter do both the PNS and SNS preganglionic neurons release into the synapse?

Answer 5

Acetylcholine

Question 6

What receptors are at the postganglionic neurons?

Answer 6

Nicotinic

Question 7

What is the neurotransmitter for the somatic motor system and how does it reach muscle?

Answer 7

Acetylcholine, it travels down a single motor neuron to the skeletal muscle where it reaches the neuromuscular junction

Question 8

What are the 3 transmitters released form the post ganglionic neurons in the sympathetic pathway?

Answer 8

Noradrenaline (to organs), adrenaline (to sweat glands) and acetylcholine (to organs)

Question 9

What is the transmitter released from the post ganglionic neuron in the parasympathetic pathway?

Answer 9

Acetylcholine

Question 10

What is different about the pathway that has adrenaline released from the post ganglionic neuron?

Answer 10

The Ach at the synapse is released onto the adrenal medulla which technically isn’t a neuron

Question 11

Describe the difference in relative location of the ganglia for the sympathetic and parasympathetic pathways

Answer 11

Sympathetic = closer to the spinal chord since preganglionic neurons are along the entire length
Parasympathetic = closer to the organs since preganglionic neurons only leave from the brain

Question 12

In the sympathetic pathway, what is the most common transmitter released from the postganglionic neuron?

Answer 12

Noradrenaline

Question 13

Why are autonomic synapses less direct than somatic synapses?

Answer 13

They affect the overall tone of the whole body rather than affecting a specific muscle fibre

Question 14

What range of heart rate is common if the body is in the parasympathetic tone?

Answer 14

<100 bpm

Question 15

What system is responsible for stopping the dizziness that happens when you stand up suddenly?

Answer 15

Sympathetic, it triggers the blood flow to be increased to counter the effects of gravity by constricting muscles in the legs

Question 16

What are the main functions of the parasympathetic system?

Answer 16

Rest and digest, it increases digestion, slows down heart rate and constricts bronchioles in the lungs

Question 17

What type of receptors are the main target for the parasympathetic system?

Answer 17

Muscarinic (acetylcholine)

Question 18

What type of receptors are muscarinic receptors?

Answer 18

GPCRs

Question 19

Describe M2 receptors

Answer 19

Cardiac, they slow the heartbeat and decrease the cardiac output

Question 20

Describe M3 receptors

Answer 20

Spread in target tissues, increase contraction of lung and GI tract muscles and relax smooth muscles

Question 21

What is the difference between the synapses in the autonomic nervous system and the neuromuscular junction?

Answer 21

Autonomic synapses tend to be in the middle of the axons rather than at axon terminals like in the neuromuscular junction

Question 22

Which neuron in the autonomic nervous system is myelinated?

Answer 22

Preganglionic neuron

Question 23

Give 5 things that happen in the parasympathetic system?

Answer 23

Pupils constrict, heart rate decreases, increased GI tract activity (dilation of sphincters), bronchoconstriction, bladder contraction

Question 24

Give a non-selective agonist for the parasympathetic pathway

Answer 24

Acetylcholine

Question 25

Give a selective muscarinic agonist for the parasympathetic pathway

Answer 25

Muscarine

Question 26

Give a muscarinic antagonist

Answer 26

Atropine

Question 27

Give a selective nicotinic agonist

Answer 27

Nicotine

Question 28

Give a selective nicotinic antagonist

Answer 28

Hexamethonium

Question 29

What are the main functions of the sympathetic nervous system?

Answer 29

Fight or flight, blocks the parasympathetic pathway

Question 30

What is the role of Alpha-2 receptors in the sympathetic pathway?

Answer 30

To ensure that too much noradrenaline is not produced, it negatively feeds back into the axon to reduce production

Question 31

Where are alpha2 receptors located?

Answer 31

At presynaptic terminals

Question 32

What receptors are activated in the heart by sympathetic neurons?

Answer 32

Beta-1

Question 33

How does adrenaline released from the adrenal medulla reach beta-2 receptors?

Answer 33

Via the blood stream

Question 34

What receptors are activated by acetylcholine in the sympathetic pathway?

Answer 34

M3

Question 35

Give 5 effects of the sympathetic pathway

Answer 35

Pupil dilation, increased heart rate, decreased GI activity, blood vessel dilation, sweating

Question 36

Give a beta-1 adrenergic agonist that is in our formularies

Answer 36

Atenolol

Question 37

Give a beta-2 agonist that is in our formularies

Answer 37

Salbutamol

Question 38

Give 2 non-selective agonists of the sympathetic pathway

Answer 38

Adrenaline, pseudoephedrine

Question 39

Give a non-selective antagonist for the sympathetic pathway

Answer 39

Propranolol

Question 40

Where is the enteric nervous system located?

Answer 40

In the lining of the gut

Question 41

What is the role of the enteric nervous system?

Answer 41

To regulate the activity of the intestines (move food towards rectum), local blood flow and glands

Question 42

Why is the gut sometimes referred to as the second brain?

Answer 42

The enteric nervous system contains more neurons than the spinal cord

Question 43

What are the names of the 2 clusters of enteric neurons?

Answer 43

Submucosal (inner) | Myenteric (outer)

Question 44

How does the enteric nervous system work?

Answer 44

Sensory neuron detects stretch of muscle due to bolus. Interneurons report this to neighbouring neurons. Neurons behind the bolus contract smooth muscle (Ach) and neurons ahead relax smooth muscle

Question 45

What hormone is released by the ENS that increases ACh and other NTs to help bolus movement?

Answer 45

Serotonin

Question 46

When is dopamine released by the ENS and what does it do?

Answer 46

In response to sympathetic activity, it reduces ACh release, stopping the movement of food

Question 47

How does the ENS respond to opioids?

Answer 47

Opioids activate mu opioid receptors which stop ACh signalling in the ENS = less smooth muscle contraction.

Question 48

Loperamide is an opioid agonist, what does this help to treat

Answer 48

Severe diarrhoea, it slows down the contractions in the gut

Question 49

Why do many drugs cause side effects impacting the gut?

Answer 49

The ENS uses many neurotransmitters and so many drugs will have some sort of effect on the ENS

Question 50

What are general visceral afferents (GVAs)?

Answer 50

Fibres that relay sensory information e.g blood pressure and stretches in the GI tract, back to the CNS

Question 51

Why is pain often difficult to locate in the gut?

Answer 51

Information passing through GVA fibres can enter the spinal cord one or two vertebra above/below where expected