Principal Efferent Outputs of the CNS:

Somatic nervous system:

links the central nervous system to various peripheral organs directly via nerve

The main tissue innervated by the somatic nervous system is

system involves nerve fibres but the efferent way into the body is via hormones (e.g. hypothalamo-adenohypophysial axis)

Autonomic nervous system is working all the time in the body without us realising - it is continually trying to maintain

There are two branches of autonomic:

- activated during a threatening (fight or flight) situation in which you need to be really active

- you don't need to be active so you're allowing various other activities to take place

Principal targets and functions of the autonomic nervous system

Sympathetic: Pupil dilation, trachea and bronchiole dilation, glycogenolysis and gluconeogenesis, lipolysis, renin secretion, relaxes detrusor, thick viscous secretion from salivary glands, piloerection, sweating, heart rate,

Parasympathetic: Pupil constriction, ciliary muscle contraction, trachea constriction, contraction of detrusor, copious water secretion form salivary glands etc

The trachea and bronchioles are NOT actually innervated by sympathetic fibres - the SNS influences the smooth muscle in these tissues via the release of

if you denervated the heart, the heart rate would

- the normal influence on the heart rate is very much parasympathetic dominated

Blood Vessels - in skeletal muscle, the SNS is associated with dilatation which is unusual and it isn't associated with innervation but more likely due to circulating catecholamines

In the skin, there is sympathetic innervation that goes to the sweat glands - but in this case, the post-ganglionic sympathetic fibres that innervate the sweat glands

release noradrenaline. They instead release

so they are cholinergic sympathetic fibres.

Parasympathetic Nervous System:

From the lower part of the brain/ spinal cord there are two main outflows

The top outflow consists of

of the cranial nerves: Oculomotor Nerve (CN III), Facial Nerve (CN VII), Glossopharyngeal Nerve (CN IX), Vagus Nerve (CN X)

They contain parasympathetic nerve fibres

Facial Nerve - innervates glands that are high up in the body e.g. tears and

Glossopharyngeal Nerve - influences activity in the tissues that are higher up

Vagus - outflow from the CNS via the Vagus goes to an array of organs (lung, heart, stomach, pancreas, small intestine)

There is also an outflow at the bottom in the

region where you have an outflow mainly via the splanchnic nerve - the nerves go to the

organs and there is another outflow to the lungs and intestine

Some organs receive both cranial AND sacral influence via the parasympathetic nervous system

Sympathetic nervous system:

There is

cranial outflow

The sympathetic nervous system has

thoracolumbar

outflows (T1-L3)

The pre-ganglionic fibres tend to leave the spinal cord and join together in a row of linked ganglia called the

in a sympathetic chain that lies adjacent to the spinal cord

It is possible that when one part of the sympathetic nervous system is activated, the effect can spread across the whole of the sympathetic chain

Some tissues and organs are innervated by both the sympathetic and parasympathetic (lacrimal glands, salivary glands, heart and lung)

The adrenal medulla only receives pre-ganglionic fibres and instead of activating a post-ganglionic fibres (like all other sympathetic pathways), in this case

cells are stimulated to release catecholamines into the general circulation

sympathetic ganglia send fibres off to the skin and blood vessels in the region of innervation

Parasympathetic and sympathetic tend to oppose each other and innervate the same organs and tissues but their outflows are very different

Summary: Parasympathetic =

Sympathetic:

The parasympathetic outflow is pre-ganglionic

The pre-ganglionic parasympathetic fibres go close to or actually in to the tissue that it is innervating so the pre-ganglionic fibres of the parasympathetic nervous system tend to be

Post-ganglionic fibres are short - they tend to be very near or actually in the tissue that it is innervating

Sympathetic has a

pre-ganglionic fibre and a

post-ganglionic fibre which goes to the innervated tissue

The adrenal medulla only receives pre-ganglionic fibres and it releases

Control of the cardiovascular system:

CO is directly proportional to MABP/TPR where CO is

MABP is

TPR is

TPR is associated with the radius of the blood vessels - inverse of the radius^4

Control of Cardiac Output:

CO=SVxHR. Sympathetic stimulation of the heart increases the force of contraction which increases

and heart rate

When the sympathetic nervous system is activated, the heart will be stimulated in 2 ways:

Increase in heart rate-

effect

Increase in force of contraction-

effect

The SNS increases heart rate and stroke volume hence increasing cardiac output

Control of Total Peripheral Resistance:

There is a certain degree of contraction of vascular smooth muscle (particularly in the arterioles) brought about by a basal activity of the SNS There is a certain degree of sympathetic

When the SNS is fired, there is an increase in the activity of the post-ganglionic fibres going to the smooth muscle

This leads to generalised

The decrease in the radius leads to a large

in TPR. Because there is always some basal activity maintaining sympathetic tone, you can reduce sympathetic activity to cause vasodilation leading to decreased TPR

Control of Arterial Blood Pressure:

Increased sympathetic activity results in: Increased cardiac output (increase HR (chronotropic) + increased SV (inotropic)) and increased total peripheral resistance

therefore increased arterial blood pressure

Vasodilation - Decreased Sympathetic Tone:

Exceptions: Increased sympathetic activity to some blood vessels in skeletal muscle causes vasodilation (either cholinergic fibres or adrenergic beta-receptors)

This skeletal muscle vasodilation is mediated essentially by circulating

and NOT by direct innervation of the smooth muscle of the blood vessels in the skeletal muscle

Local Vasodilators - release of various substances such as CO2, increased [H+], nitric oxide, histamine etc. can cause vasodilation. Many of these molecules are released as a result of increased activity in the tissues.

Autonomic Innervation of the Gastrointestinal Tract:

At a time of fight or flight, you don't want to waste time and energy digesting food so the

activity slows everything down in the gut (sphincters close, motility decreases, blood flow decreases - everything shuts down because you don't want to worry about digesting a meal if you're in a fight or flight situation)

activity increases motility of the gut and stimulates secretory activity

Increased Sympathetic Activity to the Lungs:

Causes bronchi and bronchioles to

This isn't brought about by direct sympathetic activity, it is the circulating catecholamines

Dilation of bronchi and bronchioles leads to increased

to the lungs.

Autonomic Innervation of Eye Muscles:

SYMPATHETIC: Contract radial muscle (pupil dilation)

PARASYMPATHETIC: Contracts pupillary

Contracts ciliary muscle - lens bulges for near vision

Regulation of the Bladder:

The role of the bladder is to gather and hold the urine coming from the kidneys before expelling the urine from the body

Parasympathetic Innervation of the Bladder: the pre-ganglionic fibres go to the

and the post-ganglionic fibres innervate the muscle around it

The internal sphincter is under sympathetic control. The external sphincter can be controlled voluntarily to override any autonomic effects

Regulation of the Bladder:

The bladder can go up to a capacity of around 450-500 mL

Regulation of the bladder is associated with the

inside the bladder.

receptors in the wall have an influence on afferent pathways along the pelvic nerve which is part of the micturition reflex

There is parasympathetic control of the muscle in the bladder wall - this starts making the bladder wall contract

There is sympathetic control over the internal sphincter via the

nerve.

As the parasympathetic nervous system starts increasing activity, the sympathetic nervous system starts decreasing activity

On top of that you have voluntary control of the external sphincter via the efferent fibres running along the

nerve.

Neurotransmitters used by the Autonomic Nervous System:

Two major neurotransmitters used by the autonomic nervous system:

Acetylcholine and

Adrenaline is a hormone produced by the

nervous system. So there are two neurotransmitters and one hormone

Acetylcholine: Produced from

(from metabolic pathways) and choline (largely coming from the diet and delivered to the nerve terminal via the blood)

Noradrenaline, Adrenaline and Dopamine are

They are all derived from the amino acid

They have the basic structure of a hydroxylated phenyl ring

Catechole Ring = hydroxylated phenyl ring and then modifying the side chain accordingly

The parasympathetic nervous system only has one configuration. - the only thing released by pre-ganglionic and post-ganglionic nerves is

The sympathetic nervous system consists of short pre-ganglionic neurons and long post-ganglionic neurons

All pre-ganglionic fibres in the autonomic nervous system release

The vast majority of sympathetic post-ganglionic fibres release

: the adrenal medulla only receives one nerve (pre-ganglionic) and this nerve releases acetylcholine. The cells in the adrenal medulla act sort of like a post-ganglioinic fibre - they mainly released adrenaline and a bit of noradrenaline

The adrenal medulla releases the catecholamines into the blood

There are a few sympathetic post-ganglionic fibres which release acetylcholine

SUMMARY of neurotransmitters released: ALL PNS nerves =

ALL pre-ganglionic SNS nerves =

Majority of post-ganglionic SNS nerves =

Few post-ganglionic SNS nerves (e.g. sweat glands) =

Adrenal Medulla =

post-ganglionic nerves - releases mainly adrenaline (80%) and noradrenaline (20%)

Questions: If you could block Acetylcholine action in autonomic ganglia, what effect would this have on the heart?

If you block the acetylcholine in autonomic ganglia you interfere with

So to know the overall effect, you need to know which system is predominant at that point

If you are idle - the

should be dominant - so if you block acetylcholine action the effect will decrease causing an increase in heart rate

If you are exercising - the

should be dominant - the effect would be lost and you would get a decrease in heart rate.

Transmission in the Parasympathetic Nervous System:

There are TWO important receptors in the parasympathetic nervous system: Nicotinic and

Nicotinic Acetylcholine Receptor:

on channel linked receptor - when acetylcholine binds to the receptor, the ion channel opens and you get

influx causing depolarisation of the post-ganglionic neuron

Found in the autonomic ganglia. FAST transmission from pre-ganglionic to post-ganglionic

Muscarinic Acetylcholine Receptor:

G-protein coupled receptor. It is

than nicotinic receptor transmission

Transmission in the Sympathetic Nervous System:

In terms of pre-ganglionic neurones,

release acetylcholine, you get nicotinic acetyl choline receptors on all post-ganglionic neurons

Post-ganglionic neurons, particularly those that release

need a noradrenaline receptor which is a type of adrenergic receptor

Adrenergic receptors are

coupled receptors. Nicotinic acetylcholine receptors are in all

Noradrenaline acts on adrenergic receptors

Some post-ganglionic neurons of the sympathetic nervous system release acetylcholine (e.g. to sweat glands) so you need a

acetylcholine receptor to recognise the acetylcholine

Adrenal Medulla - the pre-ganglionic neuron releases acetylcholine so you find nicotinic acetylcholine receptors in the adrenal medulla

Binding of acetylcholine to the nicotinic acetylcholine receptors in the adrenal medulla causes subsequent release of

The adrenaline is delivered to effectors via the bloodstream and adrenergic receptors across the body recognise the adrenaline

Synthesis, Metabolism and Release of Amine Transmitters:

This is the general pattern of synthesis for amine transmitter synthesis

A precursor is generated within the

some aspects from the mitochondria and some aspects from the

The precursors are then converted to a neurotransmitter of choice

The neurotransmitter is then packaged into

and sit near the cell surface and await an

to stimulate calcium influx. Calcium influx stimulates

- vesicles fuse with the plasma membrane and release neurotransmitter into the synaptic cleft

There are around 1000 neurotransmitter molecules per vesicle

The neurotransmitter bounces around the synaptic cleft and eventually binds to a receptor then unbinds quickly - one neurotransmitter can interact with several receptors

Eventually all the neurotransmitter will be removed from the synaptic cleft by

Synthesis, Release and Metabolism of Acetylcholine:

Precursors of acetylcholine: Acetyl-CoA (from glucose metabolism) and Choline (from diet)

Acetyl CoA and choline is converted into acetylcholine by

The acetylcholine is then packaged into vesicles and awaits calcium influx

After it has been released into the synapse and had its effect, the acetylcholine will be broken down by

This breaks acetylcholine really fast into choline and

which are then reabsorbed into the neuron

QUESTION: What would happen if you blocked acetylcholinesterase?

Acetylcholine will build up in the synaptic

and so it will have a prolonged effect on the post-ganglionic neuron. If you block acetylcholinesterase (e.g. with syrine gas) over time, the responsiveness of the receptors at neuromuscular junctions decreases and you'll become paralysed

Synthesis, Release, Reuptake and Metabolism of Noradrenaline:

The precursor for the catecholamines is

Tyrosine Hydroxylase is the rate limiting enzyme which generates

from tyrosine

DOPA Decarboxylase converts DOPA to

The dopamine is then packaged into vesicles containing Dopamina b hydroxylase which converts dopamine to

Breakdown of noradrenaline

take place in the synapse . It is removed by

There are TWO mechanisms of uptake of noradrenaline: Uptake 1 - taken back up into the pre-synaptic nerve terminal Uptake 2 - taken up by extra neuronal tissue

Uptake 1 - taken back up into the pre-synaptic nerve terminal Monoamine Oxidase A (MAO-A) - breaks down the noradrenaline into the metabolites

Uptake 2 - taken up by extraneuronal tissue Catechole-O-methyl transferase (COMT)

The Adrenal Medulla:

Adrenaline is different because it comes from the

Chromaffine cells produce

Sympathetic pre-ganglionic neurons innervate the adrenal gland and release acetylcholine which acts on the nicotinic receptors that stimulate the Chromaffine cells to produce adrenaline

The catecholamines from the adrenal medulla are released straight into the bloodstream - they are

Synthesis, storage and release of adrenaline in adrenal chromaffin cells:

Synthesis is similar to noradrenaline but there is an extra step. Noradrenaline is methylated by

to convert it to adrenaline

Everything produced in the adrenal cortex flood into the adrenal medulla (all the corticosteroids pass through the adrenal medulla) . The production of PNMT is increased by

As the corticosteroids pass through the adrenal medulla, cortisol upregulates the medulla's ability to produce adrenaline

The noradrenaline produced in the vesicle must leave the vesicle and bind with

to generate adrenaline. The adrenaline is then reinserted back into the vesicle .

Activation by the nicotinic acetylcholine receptor stimulates

Instead of the adrenaline being released into the synapse, it is released into the extracellular space and eventually enters the bloodstream

Principal Metabolites of Adrenaline and Noradrenaline:

Monoamine Oxidase (MAO-A)

Catechole-O-methyl transferase (COMT) removes one of the

groups. MAO-A does most of the metabolism in neurons - therefore, if you look at the CSF, then all the metabolites you're going to see are the metabolites produced by MAO-A

MAO-A produced

If you want to look at the peripheral metabolism of catecholamines you need to look at the enzyme activity of COMT. Product of COMT breakdown is VMA.

By looking at the levels of the two metabolites in the

- MOPEG levels give an idea of the

activity in the brain (in the neuronal production of noradrenaline)

VMA levels give an idea of the peripheral production of noradrenaline

So by looking at the levels of the two different metabolites in the urine you can get information about the noradrenaline activity in the brain and in the periphery

The Fight-Flight Response:

mass

discharge in response to alarm or stress'

Results in: Increased arterial blood pressure Increased blood flow to active muscles (and decreased blood flow to other areas such as the splanchnic bed) Increased blood glucose concentration Increased respiration Increased awareness

The Sympathetic Nervous System: The Acute Stress Response

Any stress will eventually converge on the

From the hypothalamus it is relayed down to the sympathetic nervous system

There is a mass discharge of sympathetic

The links between the sympathetic ganglia allow mass discharge so all the post-ganglionic fibres can fire together to all the targets

You also get sympathetic stimulation of the adrenal medulla to cause adrenaline discharge

Autonomic Nervous System - Control of Cardiac Output :

The ANS affects both cardiac output and

CO = SV x HR

Sympathetic stimulation of the heart causes: Inotropic Effect -increased

Chronotropic Effect -increased

Release of noradrenaline which then binds to the

receptors in the cardiac muscle causes an increase in the force of contraction of the cardiac muscle

Sympathetic nerves also innervated the SAN and release

to the adrenergic receptors in the SAN which causes an increase in heart rate

Total Peripheral Resistance:

The sympathetic nervous system tends to cause mass

Increased sympathetic activity leads to vasoconstriction

This causes an increase in total peripheral resistance

The Baroreceptor Reflex:

The baroreceptor reflex makes the sympathetic

its firing rate There are baroreceptors in the carotid sinus and aortic arch

You also have cardiopulmonary volume receptors which respond to changes in volume and pressure in the system

The more pressure and volume there is, the faster the neurons from the baroreceptors and volume receptors fire

If there is a DECREASE in blood pressure: Firing rate from the baroreceptors

There is less stimulus to the brain

You get a decrease in the

of the SNS. Sympathetic activity increases

Normally, the baroreceptors and volume receptors act on the brain and stimulate the brain to switch

the sympathetic nervous system

If there is a normal rate of firing - this tells the brain that the blood pressure is

A fall in pressure brings about reflex activation of the sympathetic nervous system to bring the blood pressure back up

The reverse is also true if you get an increased blood pressure - this works both ways

People with hypertension - over time there becomes a bit of a disconnect between the baroreceptors and the regulation of blood pressure

Normal Cardiovascular Response to Gaining an Upright Posture :

When you stand up you are bringing GRAVITY into play - gravity tries to push the blood down to your feet

As the veins are distensible, you can get blood

in the lower limbs If you have more blood pooling in the veins, then there is reduced venous return meaning that there is a lower blood pressure

in the lower limbs If you have more blood pooling in the veins, then there is reduced venous return meaning that there is a lower blood pressure -

law

This decrease in blood pressure causes activation of the baroreceptor reflex

Decreases stimulation of the baroreceptors means that less stimulus is delivered to the brain to switch off the sympathetic nervous system so there is an

in activity of the sympathetic nervous system and so blood pressure

Postural Hypotension:

Most people suffer with transient postural hypotension at some point in their lives -more likely if you're

Some people suffer a more clinical postural hypotension

You can get

failure where the autonomic nervous system doesn't act the way it should - so people struggle to maintain blood pressure when they stand up

When you stand up, there will be a pooling of blood in the lower limbs --> reduced venous return --> decreased cardiac output --> decreased

This will cause decreased stimulation of the baroreceptors and (in people with clinical postural hypotension) there is an impaired

nerve response. This means that the baroreceptor reflex has little effect on the heart and particularly on the TPR and, therefore, your ability to maintain arterial blood flow is diminished

This will lead to less blood flow to the brain resulting in

Fainting is a way of getting you on the floor so that the blood flow to your brain can return to normal and you remove the effect of gravity in causing pooling of blood in the veins of the lower limbs

Autonomic Control of the Eye:

The parasympathetic nerve that we're looking at is the

(CN III)

This nerve goes to the ciliary

and there is a short post-ganglionic nerve fibre going to the ciliary muscle

Parasympathetic and sympathetic act in opposition

The iris is under control of

control(s) of the ANS

Parasympathetic will cause pupil constriction Sympathetic will cause pupil dilation

Effect of pilocarpine on pupil diameter:

Pilocarpine is an acetylcholine drug- If you insert pilocarpine into the eye, you get miosis -pupillary

By inserting pilocarpine into the eye, you activate the muscarinic acetylcholine receptors in the iris and make the iris contract inwards thus narrowing the pupil

Blockage of the Parasympathetic System:

If you block the parasympathetic with atropine, the only thing that's left is the sympathetic control of the iris so you get massive pupil

This is called

The Pupillary Light Reflex:

This is the machinery controlling the pupil's response to light

Light comes through the pupil, reaches the retina and information is relayed to the brain via the

The efferent control of pupil diameter originates in the

nucleus which is relayed to the Edinger-Westphal nucleus - from here, the parasympathetic neurons originate

These parasympathetic neurones

start from where the optic nerve ends The short post-ganglionic parasympathetic neuron innervates the iris and causes pupil constriction and decreases the amount of light coming to the eye

So pupil constriction is mediated by a

reflex

The Consensual Reflex:

if you shine light in one eye,

pupil(s) will contract

This happens because the afferent information

on the pretectal nucleus

If you shine light in the right eye, the information is relayed to the pretectal nucleus which activates

parasympathetic nerves to the right and left eye Even though the stimulus only comes through one eye, you get activation of both efferent nerves

Parasympathetic nerves release acetylcholine which acts on

receptors to make the pupils smaller

Acetylcholine is first released in the ciliary ganglion to bind to the nicotinic receptors on the post-ganglionic fibre. Acetylcholine is then released by the post-ganglionic fibre which goes on to bind to the muscarinic receptor

The autonomic nervous system is responsible for involuntary control of the

Divisions: Sympathetic, Parasympathetic, Enteric - intrinsic nervous system of the gut

Autonomic Nervous System Schema: The body contents receive parasympathetic and sympathetic inputs which balance each other to maintain

Alongside the spinal cord you find the sympathetic

which are a collection of cell bodies immediately beside the spinal cord

Physiological Actions of the Autonomic Nervous System:

Parasympathetic- this response is

Sympathetic - this response is

Mobilises body energies for increased activity

Higher brain centres and homeostatic changes stimulate the

which stimulates the medulla to activate autonomic response

The biggest drive is

The higher functions of the brain (cerebral cortex) can initiate an autonomic response (e.g. if you're scared of something and you come across it again) so the higher centres do have an effect on the autonomic nervous system

Recap of Autonomic Pathways:

Both parasympathetic and sympathetic have

fibres which start in the CNS

It sends out fibres towards the periphery and somewhere along this path you'll find an autonomic ganglion

Each of the cell bodies in the ganglion will send axons out to various places

Sympathetic =

preganglionic fibre. Ganglia are found in the

trunk which is closer to the spinal cord than the organ/viscera being innervated

Parasympathetic =

preganglionic fibre

Definitions: Afferent Nerves - coming

the CNS

Efferent Nerves- coming

the CNS

Sympathetic Nervous System:

Preganglionic efferent fibres arise from: Thoracic Nerves and Upper Lumbar Nerves

The sympathetic nervous system is the

division of the ANS

SNS consists of:

sympathetic trunks

Nerve plexuses (e.g. cardiac plexus - dense innervation of sympathetic fibres)

Subsidiary ganglia - there are some specialist ganglia that are little bit further out in the body

Innervates: Sweat Glands - usually the parasympathetic has the localised function but the exception is the sweat glands

and Arrector pili muscle of hair follicles

Preganglionic neurons are in the lateral column grey matter of spinal cord T1 to

IMPORTANT: normally you just have the ventral horn and the dorsal horn of the grey matter but in thoracolumbar spinal cord you get a

horn of grey matter which is where you find the preganglionic sympathetic neurons

The fibres emerge from the spinal cord via the

root of the spinal nerve

Passes through the ventral

to the white rami communicantes to the sympathetic ganglion

Connection between the ventral ramus and the sympathetic ganglion is via: white ramus- fibres go

the ganglion

GREY ramus = fibres

the ganglion

Sympathetic ganglia are right next to the vertebral column

The fibres going to the sympathetic ganglia can synapse within the ganglion or it can send fibres up and down to other ganglia

The postganglionic fibres are distributed to the effector organ via

rami communicantes

It then travels in the dorsal or ventral rami

Circuitry of the Sympathetic Nervous System:

All around the outside you get

matter - the tracks where the other neurons are ascending towards the brain or descending away from the brain

The distribution of grey and white matter here is the

of what you find in the brain where you have grey matter around the outside

There is a

horn of grey matter in this cross-section which defines it as thoracic spinal cord

Normally you have a dorsal horn (sensory processing) and a ventral horn (where you have motor neurons) but here you alsohave a lateral horn of grey matter which is where you find the preganglionic sympathetic neurons

The axon of the neuron is sent out through the

root and then it gets into the spinal nerve where the ventral and dorsal roots meet

Ventral =

Dorsal=

At the spinal nerve, where the ventral and dorsal roots meet, information is going in both directions

The spinal nerve then splits into the ventral ramus and the dorsal ramus

The preganglionic fibre passes through the white rams communicates and from here, you can get

types of circuitry: Simplest-

the preganglionic fibre synapses in that sympathetic ganglion staight away. The postganglionic fibre then goes out to the spinal nerve via the

ramus communicantes at the same level and then it goes out to the viscera

The fibre can come into the sympathetic ganglion and then go up or down the sympathetic chain and synapse in any of the other ganglia so the postganglionic neurons are then distributed at the level of that ganglion

The third option is to go straight through the ganglion without synapsing and then to synapse in one of the subsidiary ganglia which are a little bit further out such as the coeliac ganglion and the superior mesenteric ganglion

Sympathetic Trunks:

Base of the skull to the

Ganglia by region:

Cervical-

Thoracic = 11 or 12

Lumbar=

Pelvis = 4 or 5

preganglionic fibres do NOT come out in the

region.

Sympathetic fibres pass from the spinal nerves to the sympathetic trunk via the

ramus communicantes

Distribution of Sympathetic Fibres in the Cervical and Thoracic Regions :

Plexuses: Around the pharynx Cardiac plexus Thyroid plexus Pulmonary plexus Around the thoracic aorta Splanchnic nerves

The three cervical sympathetic ganglia

immediately next to the cervical spinal cord

The sympathetic trunk is distributed around the body alongside major vessels Cervical ganglia are closely associated with the

The three ganglia are classed as: superior, middle and inferior

Splanchnic Nerves:

There are three types: Greater, Lesser and Least The splanchnic nerves arise in the

then they pierce the diaphragm and go down into the abdominal cavity

The greater follows the thoracic

supply and pierces the diaphragm and enters the abdomen plexus around great blood vessels supplying the gut

Lesser Pierces the diaphragm and enters the abdomen plexus around the aorta

Least Pierces the diaphragm and enters the abdomen plexus around the

Distribution of Sympathetic Fibres in the Lumbar Region:

There are

lumbar ganglia

Lumbar splanchnic nerves take part in all plexi of sympathetic nerves in the abdominal and pelvic regions

It pierces the thorax and surrounds the vasculature and the GI contents of the abdomen

Sympathetic Actions:

Blood vessels-

Sweat glands (secretomotor), Hairs (motor), Sympathetic nerves accompany nerves to voluntary muscles but they DO NOT innervate the voluntary muscle, they innervate the blood supply to the voluntary muscles ,Viscera - dilation of pupils, dilation of arterioles, movement of alimentary tract and urinary bladder (i.e. relaxes walls, constricts sphincter)

Parasympathetic Nervous System:

Preganglionic efferent fibres arise from: Cranial Nerves and Sacral (spinal) Nerves

The parasympathetic ganglia are no where near the CNS - they are very close to what is being innervated - there is a

postganglionic neuron

Sacral Outflow

Via the anterior rami of spinal nerves S2-S4 from the sacral spinal cord It goes directly to the pelvic viscera via the pelvic

Pelvic Splanchnic Nerves:

Motor fibres to the rectum Motor fibres to the bladder wall (makes it contract so the bladder empties) Inhibitory fibres to the bladder sphincter (opens the sphincter) Penis/Clitoris - causes erection via vasodilator fibres

Fibres also pass superiorly to supply large parts of the gut with visceromotor innervation

Cranial Outflow :

There are

pairs of cranial nerves Cranial nerves are pretty much the same as spinal nerves but they also have the fibres underlying all the specialist functions in the head and neck

Oculomotor Nerve (CN III): Supplies all the extrinsic muscles in the eye - helps with coordinated eye movements Ganglion for the oculomotor nerve is directly behind the eye ball - the

Postganglionic fibres go to the sphincter pupillae and ciliary muscle inside the eye and causes

Facial Nerve (CN VII): Main function is to the supply the

of the face If you tell someone to look up and you see creasing of the forehead then the muscles are working fine

It supplies via the

ganglion

It supplies

of the 3 salivary glands - submandibular and sublinguinal salivary glands

Postganglionic fibres to the paranasal sinuses and lacrimal glands

Glossopharyngeal Nerve (CN IX):Supplies the THIRD salivary gland -

The parotid gland is just in front of your

The ganglion is the otic ganglion which is very close

Vagus Nerve (CN X) : Enters the neck and goes down in the neck in the

Within the carotid sheath you find the carotid artery and the internal jugular vein

It goes into the thorax where it sends branches to the lungs, heart, stomach, oesophagus and GI tract

Enteric System: This is the intrinsic nervous supply of the gut and it falls into

layers: Myenteric (Auerbach's) Plexus - associated with the musculature of the gut: Submucous (Meissner's) Plexus - in the submucosal layer

Sensory - it monitors mechanical, chemical and

activity of the gut Motor - gut motility, secretion and

Structural divisions: CNS-

PNS-

Functional divisions: Somatic- controls

function for body wall

Autonomic- Controls

CNS consists of cerebrum, cerebellum, brain stem and spinal cord

The CNS carries out “

" y processing sensory and motor information and maintaining the internal environment. It also supports higher functions such as perception, cognition, emotion and memory

The

regulates/controls internal organs, blood vessels, glands, structures in the eye and genitalia

To a large extent, there is localisation of function within the NS, but a functional system may consist of several structures at some distance from each other, connected by pathways

Each cerebral hemisphere has a

relationship with the side of the body it controls

Some higher functions, such as language, are represented in one

Neurones are the functional units of the nervous system. They have a cytoplasmic process, called an

which conducts impulses away from the cell body towards other neurones or muscle fibres.

The point of contact with other cells is called a

The resulting network contains many pathways that usually consist of multiple neurones. A neural pathway is usually represented diagrammatically

Axons that are grouped together in peripheral nerves regenerate after injury, although functional recovery is often compromised by non-specific target

Axons within the CNS do not generally regenerate over long enough distances to be useful. This appears to be due to the presence of inhibitory factors and the absence of some guidance cues in the mature CNS environment, but also may involve

neuronal differences

Diagnostic methods:

Patient history- symptoms, their

other illnesses, social situation etc

Good opportunity for

of patient to find abnormalities

Neurological examination - Level of

speech, mental state and cognitive function, sensory function, motor function and cranial

Specific methods-

Neurophysiology/electrophysiology:

(EEG)- Measures electrical potentials at

generated by underlying neurones. Particularly useful at diagnosing

(EMG) and nerve conduction studies (NCS)- Examines integrity of

, peripheral nerve and lower motor neurones

Imaging- Computerised Tomography (CT)

Uses

source, high concentration of ionising radiation

Shows hard tissues well, but not good for

Magnetic resonance imaging:

Based on the behaviour of hydrogen protons in the tissues to a strong, externally applied

Good for differentiating soft tissues. Does not use

e.g. Multiple sclerosis- MRI shows

which shows degeneration of white matter

e.g Migraine-

demonstrates cerebral vessels radiographically after injection of contrast medium

Asymmetry of brain activity and dampening of activity seen during migraine

The deep folded area of the brain is the

The bendy bit of white matter in the middle is the

It interconnects corresponding areas of the two hemispheres so there is constant conversation between the two hemispheres

The area under the corpus callosum which looks a bit like an anteater is the

Functions:

Cerebellum-

Motor function (it doesn't initiate movement but it does coordinate it) - important for learning motor skills such as playing the piano or riding a bike

Brain stem-

Contains a number of nuclei (nuclei as in a group of

There are lots of ascending and descending pathways that go through the bran stem

Ascending - takes

information up to the brain

Descending - comes down from the motor cortical areas down the brain stem and stimulate neurons in the spinal cord which then produce movement

There are a number of cranial nerves attached to the brain stem - these provide sensory and motor innervation for the head region

Diencephalon-

Thalamus -

area of the diencephalon - this is a relay station for information going between the cerebral cortex and other parts of the CNS in both directions

Hypothalamus - found inferior to the thalamus and is important in coordinating

Cerebral Cortex:

Deep inside the cerebral cortex you find lots of nuclei. One of the main nuclei is the

which is a group of nuclei which produce the pattern of movement and work together with the motor cortex

Divisions of the Brain:

Diencephalon is strongly attached to both hemispheres. Just below the diencephalon, you get the

The pons is inferior to the midbrain and is recognisable because it has a characteristic

Attached to the bottom of the pons is the

which merges with the top of the spinal cord as it goes through the hole in the base of the skull

The brain first develops into three main parts: Forebrain, Midbrain and Hindbrain

The cerebral hemispheres and the diencephalon develop from the

The pons, medulla and cerebellum develop from the

and the

stays relatively the same.

Cortical areas:

This is the left side of the

hemisphere. There are two types of cortex in the hemisphere: Primary cortical areas and

Primary cortical areas are usually quite

Primary Motor Cortex - the cells of this cortex send axons down through the descending pathway to stimulate motor neurons in the

which then stimulate the muscle via the peripheral nervous system. The primary motor cortex has a

arrangement.

Somatotopic = arranged like a body map - area at the bottom controls movement of the head, middle is movement of the arms and top is movement of the legs

So depending on where the damage is to the primary motor cortex you'd expect to have loss of voluntary movement in a particular place

the cerebral hemisphere relates to the

side of the body

Primary Somatosensory Cortex is adjacent to the primary motor cortex and is also has somatotopic arrangement

The primary somatosensory cortex received general sensory information coming from the body

Association cortex is where much of the higher functions take place e.g. learning, perception, thinking etc.

Wernicke's Area = important for understanding

Broca's Area = important for

Ventricular System:

There are two large

shaped ventricles with a spur at the back

These are the lateral ventricles. There is a lateral ventricle in each hemisphere

The two lateral ventricles, via a tiny foramen, join up with a single midline ventricle called the

The 3rd ventricle lies in the middle of the

At the base of the third ventricle there is narrowing to form a fine channel called the

The aqueduct passes through the midbrain and at the top of the midbrain it opens up again into a

shaped fourth ventricle.

The pons and medulla is in front of the fourth ventricle and the cerebellum is behind it

At the lower part of the medulla the fourth ventricle narrows again to form a very fine channel called the

which goes down into the spinal cord

The lateral ventricle can't be seen because it is in the hemisphere

Cerebrospinal Fluid:

Produced by a special type of ependymal cell which are found in the ventricles called the

It filters the blood, takes most of the cells out and then secretes it

CSF circulates through the ventricular system and gets to the

which has holes in it so the CSF can exit and spread round the brain

The CSF circulates in the sub-arachnoid space between the

It is reabsorbed into the venous system by

In the space between the brain and the bone you get the

(dura, arachnoid and pia mater)

Between the arachnoid and the pia you have the

space where CSF can circulate

There are venous sinuses over the surface of the brain

There are some out-pockets of the arachnoid membrane which pushes through the walls of the venous sinus and allows reabsorption of CSF - these are

Sometimes you can get a blockage causing a build up of CSF in the brain - this is

Demonstration Notes:

Some of the sulci are fairly constant - they are in the same place in all brains

Most sulci are quite variable but the sulci which are constant are used as a means of dividing the cortex into lobes

Central Sulcus = separates the

lobe from the parietal lobe

Sulcus = separates the parietal lobe from the occipital lobe

Lateral Fissure/Lateral Sulcus = separates the

lobe from all the other lobes

Looking at the inferior surface of the brain:

Optic chiasm lies at the base of the

Next to the optic chiasm you find the

More on the ventricular system:

Posterior horn of the lateral ventricle goes into the

The largest part of the brain is the

On the outside of the lateral ventricles you find the basal ganglia

Basal Ganglia are a group of nuclei which act together and are involved in the regulation of voluntary movements

Functions the ventricular system: Mechanical protective role

It's sort of like the foetus being held in the amniotic sac

Spinal Cord:

The spinal cord is a column of neural tissue which is

Each segment has a pair of spinal nerves attached to it . The core consists of

which mainly contains neuronal cell bodies

There is a wrapping around of the white matter containing axons

The grey matter is divided into

Dorsal horns of the grey matter are

The cell bodies of the sensory axons are in the

The axon then continues via the dorsal root and enters the dorsal horn

The sensory information is then carried up ascending pathways in the white matter to the brain for analysis

The ventral part of the grey matter consists of

Axons of the motor neurones go out via the

roots and to the muscles

Dorsal -

the CNS

Ventral-

from the CNS

CNS is brain and spinal cord. The brain developed from the

then has three main divisions, each consisting of different separate structures: forebrain, midbrain and

The brainstem consists of Midbrain, Pons and the

These lay between the two hemispheres and share a lot of similar functions.

The brain stem is also the part of the brain that joins with the

The two hemispheres are divided by the

with the diencephalon sitting between the two hemispheres

Each hemisphere is covered in a folded cortex consisting of folds/elevations-

and grooves/depressions-

The groove that runs between the two hemispheres is called a

Each of the main divisions is large and consists of different structures with different functions: Forebrain-

Cerebral hemispheres: Cerebral cortex- involved in a wide range of functions: consist of functional cortical areas known as

and associated ares. These areas are discrete areas with specific functions, therefore a deficit as a result of any damage to these areas can be predicted:

Primary motor cortex – involved in effector/motor functions

Primary somatosensory cortex – receives

input from the body.

Primary visual cortex – first location to receive input from the

Primary auditory cortex- first location to receive input from inner ear

Associated cortical areas- areas primarily involved in higher function of brain but more unpredictable

Broca's area- involved in

area- involved in comprehension of language . These areas are much better represented in left hemisphere

Cortical lobes- each hemisphere consists of gyro and sulk which come together to form 4 lobes which then in turn contain the functional cortical areas:

Frontal lobe- most anterior, Parietal lobe,

lobe- most posterior and temporal lobe

Two hemispheres divided by deep longitudinal fissure but 3 main grooves can be thought to divide each cerebral hemisphere:

Central sulcus- runs medially through the lateral aspect of the hemisphere, with the frontal lobe just anterior and the parietal lobe just posterior to the sulu

Lateral fissure- anterior to and below the central sulcus, the lateral fissure separates the frontal and

lobe

Parietal-occipital sulcus- posterior to central sulcus, it runs posterior to parietal lobe andd anterior to occipital lobe

Corposus

- interconnects corresponding parts of 2 hemispheres across the midline (C shaped structure seen if the brain is cut in the mid-sagittal plane

Basal ganglia- groups of neurones referred to as nuclei within each hemisphere that are responsible for the control of

Diencephalon:

Lies between the two hemispheres, consists of two main structures: the thalamus and hypothalamus

Thalamus is involved in relax of

between brain stem/lower structures and cerebral cortex

Hypothalamus is below and anterior to the thalamus and involved in coordination of

mechanisms- interface between CNS, autonomic nervous system and endocrine system

There are also related structures which lie in the diencephalon:

Optic chiasma/nerve and infundibulum which is the stalk of the

and lies just below the hypothalamus

Brain stem:

Ascending and descending tracts connect spinal cord to the brain. Controls vital functions e.g. respiration, consciousness, sleep cycle and blood pressure. It also controls cranial nerve functions. It consists of: