L1- Homeostasis and the autonomic nerouvs system

Features of homeostasis (4)

• the control of the internal environment (ECF)

• The maintenance of equilibrium through compensation

• The maintenance of variables within limited ranges

• Involves the integrated function of different organ systems

What is significant about the fact that the digestive, reproductive, urinary and respiratory systems are open to external environemtns at at least o ne end

Need good immune response

What does the term pathophysiology summarise

the fact that a failure to maintain homeostasis will result in disease

What does negative feedback result in

A decrease of the stimulus

Describe how changes in pupil diameter occur

• Changing light levels are detected via ganglia within the retina

• Response via the autonomic nervous system to iris muscles

• Are either the circular, constrictor and sphincter pupillae when in bright. Light or the radial, dilator and dilator pupillae in darkness

What are the control centres of the ANS

Hypothalamus, brain stem, spinal cord

What is an examples of sensory afferent nerve fibres in the ans

BaroReceptors for blood pressure → afferent finish in the brain

What are the efferent pathways of Thr ANS

Sympathetic and parasympathetic nervous systems

What are the common features of the 2 efferent pathways in the ANS (4)

• 2 neurons in series

• Preganglionic neurons originate in the CNS

• Postganglionic neurons originate in autonomic ganglia

• 1 preganglionic neuron can sysnapse with many postganglionic neurons (on avergae 8-9) meaning the signal is amplified

Where on the spinal column do most Parasympatehrci NS triggers come form

Higher upon the spinal column

How does the sympathetic nervous system have ganglia extending from

Has a column of sympathetic ganglia on either side of the spinal cord

Along with the releases of adrenaline, noradreline and cortisol what is a recently evidenced compound that also has a role

Osteocalcin

How does osteocalcin play a orle in the fight or flight system

The amygdala centre in the brain releases bone osteoblasts→ osteocalcin→ inhibition of the PS NS so the sympathetic nervous system is unopposed

Where are the preganglionic origin is in the parasympathetic NS (5)

• crainial nerve III (ocuulomotor)

• Cranial nerve VII(facial)

• Cranial nerve IX(glossopharyngeal)

• Cranial never X(vagus)

• Pelvic nerve (rectum, bladder)

Where aare the postganglionic origin of the PS NS

Ganglia on or near the target organ

What are the relative length of each ganglia in the PS NS

Pre= long, post= short

Where ae the preganglionic origins of the S NS (2)

• thoracic 1

• Lumbar 2/3

Where are the postganglionic origins of the S NS

2 paravertebral sympathetic chains close to the spinal cord

What are the relative lengths of each ganglia in teh S MS

Pre= short, post = long

What is another part of the S NS that acts as a ganglion

The adrenal medulla

Features of the adrenal medulla in teh S NS (3)

• directly innervated (supplied with nerves) by the preganglionic neurons of the S NS

• Secretes adrenaline and noradrenaline into the bloodstream

• Has no postganglionic neurone

What are the types of neurotransmitters of the ANS (4)

• Ach

• Noradrenaline

• Adrenaline

• Non adrenergic, no cholinergic (NANC) neurotransmitters

What are NANCs often

Amino acids

What are the types of synapses in the ANS (2)

• cholinergic (NIcotinic or muscarinic)

• Adrenergic (alpha or beta)

What neurotransmitter do cholinergeric synapses use

Ach

What neurotransmitter do adrenergic synapses use

Adrenaline or noradrenaline

In the nicotinic cholinergic receptor are the ganglia the same ein the S NS and PS NS

Yes

What blocks the nmj in the nicotinic cholinergic synapse

Curare

What is the target organ in the PS NS

The muscarinic receptor

What is the neurotransmitter in both nicotinic and muscarinic receptors

Ach

What blocks the muscarinic receptor

Atropine

Where is atropine found (2)

• Fly agaric (amanita muscaria)

• Deadly nightshade (atropa belladonna)

Why is the deadly nightshade cales belladonna

Some. Used to apply it to their eyes to cause the pupils to dilate due to the action of atropine making them appear more attractive

In alpha adrenoreceptors what aare the 2 neurotransmitters and which is more effective

Noradrenaline and adrenaline but noradreline stimulates more then adrenaline

What happens at the alpha 1 postsynaptic receptors

Vasoconstriction and smooth muscel contration

What happens at the alpha 2 presynaptic receptor

Reduction in adrenergic and cholinergic transmission

What blocks the alpha adrenoceptors

Phentolamine

Where is the b1 adrenoceptor

The heart

What is the relative effect of both Adr and NAdr in the b1 adrenoceptors

Adr and NAdr have the same level of effectiveness

What happens at the b1 adrenorecpotrs

Casues an increase in heart rate an force of contraction

What is the relative effectiveness of Adr and NAdr in the b2 adrenoceptors

Adr>NAdr

What happens at the b2 adrenoceptors

Vasodilation and smooth muscel relaxation

What blocks the beta adrenoceptors

Propanolol

Why is propanolol used as a treatment for high BP

Blocks the b2 receptors so heart rte slows

What happens in the postganglionic neurons of adrenergic receptor

• postganglionic neurone is in target organ

• Noradrelanie released

• Binds to adrenergic receptor bound to the G protein

What is different abut the sometimes motor pathway and the autonomic pathways (PS NS and S NS and adrenal medulla pathay )

• synapses directly with muscle

• Has no ganglia

Why is atropine used by opticians

Stops the effect of the PS NS so only the S NS is active leading to pupil dilation so retina can be studied