Structure of the Autonomic Nervous System

Question 1

Autonomic Nervous System

Answer 1

Parts of the Nervous System under Involuntary control

Question 2

Examples of autonomic functions

Answer 2

Secretion of saliva
Heart Function
Eye focus
Pupillary dilation

Question 3

Which muscles are controlled by the Somatic NS and ANS

Answer 3

SNS - Skeletal

ANS - Smooth and Cardiac muscle

Question 4

Divisions of ANS

Answer 4

Sympathetic - Involved in stress (fight or flight)
Thought of as an accelerator

Parasympathetic - Rest, growth, maintenance (Rest and Digest)
Thought of as ‘break’

Question 5

Biological responses to fight or flight sympathetic NS response

Answer 5

Positive cardiac inotropy and chronotropy

Vasoconstriction in gut

Vasodilation in SkM

Increased sensory awareness

Sweat secretion

**Also I think bronchodilatation

Question 6

Compare the neurons of the somatic nervous system and the autonomic nervous system

Answer 6

Question 7

Compare the neurons of the sympathetic and parasympathetic nervous systems

Answer 7

Question 8

Paravertebral Column

Answer 8

Nerves innervating the area between T1 and L3 of the spine

Question 9

Area of nerves above the T1 vertebra

Answer 9

Pre-vertebral column

Question 10

Where do pre-ganglionic fibres of the sympathetic NS emerge from in the spinal cord

Answer 10

T1-L2

note that they innervate paravertebral or prevertebral ganglia

Question 11

Describe the structure of the paravertebral chain relative to each vertebra

Answer 11

Direct association with the specific ganglia and the spinal cord at each spinal segment

Question 12

Compare the Somatic NS to the Sympathetic (structure)

Answer 12

Afferent nerve passes through dorsal horn before entering the spinal column

In intermediolateral column, there are cell bodies of pre-ganglionic fibres which leave the cord via the ventral horn; they synapse with the sympathetic ganglia in the paravertebral column with a post-ganglionic fibre which leaves and the efferent nerve then controls its target tissue

**The pre-ganglionic fibre synapses with more than one post-ganglionic fibre in another spinal segment (could be at next segment down/up or further)

Question 13

How does the sympathetic outflow from the spinal cord work

Answer 13

The efferent nerve leaves via the ventral horn; it reaches the para-vertebral horn via the white ramus (myelinated) where it synapses with the post-ganglionic fibre

The post ganglionic fibre leaves via the grey ramus (unmyelinated) where it then goes to the target tissue

Alternatively, the post ganglionic fibre moves up the para-vertebral chain

Question 14

How is the eye innervated via the sympathetic nervous system

Answer 14

The preganglionic NS synapses with the post-ganglionic fibre at another part of the paravertebral column

Question 15

Midline plexus

Answer 15

Paravertebral chain is on either side of the spinal column - each pre-ganglionic fibre moves down para-vertebral chain, exits down and synapses with post ganglionic fibres at the splanchnic nerves

Question 16

Cranio-Sacral outflow

Answer 16

Exits of the parasympathetic NS from the spine - From the top of the spinal cord or the base of the spinal cord

Question 17

Functions of 3rd, 7th, 9th and 10th Cranial Nerves

Answer 17

III: Oculomotor (Eye)
VII: Facial (Lacrimal and salivary Glands)
IX: Glossopharyngeal (same as VII)
X: Vagus (Heart, Lungs, Upper GI Tract)

Question 18

What tissue do Sacral Parasympathetic nerves control

Answer 18

Lower GI Tract
Bladder
Genitalia

Question 19

Which neurotransmitters are used by Sympathetic Nerves

Answer 19

ACh in pre
Noradrenaline/Adrenalin in post
nACh-R in pre-post synapse
α or β adrenoceptor in neuromuscular junction

Question 20

Which neurotransmitters are used by Parasympathetic Nerves

Answer 20

ACh in pre and post
nACh-R in pre-post synapse
mACh-R in NMJ

Not ionotrotropic receptors - metabotropic/G-protein coupled receptors

Question 21

Exceptions to ANS Neurotransmission

Answer 21

ACh acts on metabotropic ACh receptor in sympathetic NS and Post NT is ACh

Question 22

Tissues with only sympathetic Innervation

Answer 22

Adrenal Medulla
Pilorector muscles (hair follicles)
Sweat Glands
Spleen
Many Blood vessels (especially in skin)

Question 23

Tissues with only parasympathetic Innervation

Answer 23

Ciliary muscle (eye)
Constrictor pupillae (eye)

Question 24

Autonomic innervation of the eye

Answer 24

Controls the pupillary size and shape of the lens

Question 25

How is dilation of the eyes controlled

Answer 25

Radial muscles controlled by the Sympathetic ANS that pull open the pupil during contraction to increase diameter

**Remember sympathetic because in fight or flight the body has to let as much light in

Question 26

How is the constriction of the eyes controlled

Answer 26

Circular muscle that contracts the pupil; supplied by the parasympathetic NS

Question 27

Describe the Autonomic Innervation of pupillary muscles

Answer 27

Question 28

How is focus of the eye controlled (accommodation)

Answer 28

Long pre-ganglionic fibre synapses in ciliary ganglion with post ganglionic fibre - its activation causes the synapse with ciliary muscles to change lens shape. This happens through the ciliary muscles connecting to suspensory ligaments at top and bottom of lens, making it reduce in diameter and get fatter. This allows near vision.

Reducing PS outflow causes relaxation, allowing far vision

Question 29

Direct and Consensual Pupillary reflex

Answer 29

Shine a light into an eye; in a healthy person there should be pupillary constriction. The optic nerve is responsible for this converting light into AP, sending it to a nucleus in the brain (Pretectal)

It is synapsed to an intermediary neuron though - the two branches interface with another nucleus (E W), which reaches both sides, contracting both the eyes

Basically, pupillary constriction in one eye should cause constriction in the other

Question 30

Parasympathomimetics and Effects on Eye

Answer 30

Agonists of parasympathetic systems

e.g. physiostigmine (Anti AChE), pilocarpine (mACh)

Cause miosis (constriction of pupil)
Decrease in near point (I think ability to focus on near objects)
Decrease in Intraocular Pressure

Question 31

Parasympatholytics and Effects on Eye

Answer 31

Blockers of parasympathetic systems

e.g. Muscarinic Receptor Antagonists - tropicamide

Causes:
Mydriasis (pupillary dilation)
Cycloplegia (loss of accommodation)
Increase IOP

Question 32

Sympathomimetics

Answer 32

Agonists of sympathetic system

e.g. Adrenaline, Amphetimine

Causes
Mydriasis (pupillary dilation)
Increased IOP

Question 33

Sympatholytics

Answer 33

Antagonists of sympathetic systems

e.g. Adrenoceptor antagonists - phentolamine

Causes miosis (pupillary constriction)