Session 4 - The Autonomic Nervous System and the CVS Flashcards by Matt Quinn

Give two factors which are under the control of the autonomic nervous system

Heart rate

Blood pressure

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What three physiological features does the autonomic nervous system control to have an effect?

Smooth muscle
Exocrine secretion
Rate and force of contraction in the heart

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What are the two sections of the autonomic nervous system?

The sympathetic and the autonomic

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What are the two series of neurones in the ANS called?

Pre-ganglionic and post-ganglionic

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What is a ganglion?

A collection of nerve cell bodies in the PNS

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What is a nuclei?

Collection of nerve cell bodies in the CNS

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Describe the structure of the autonomic nervous system

Pre-ganglion with nerve cell body in CNS

Post-ganglion with nerve cell body in PNS

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What is the outflow of the sympathetic nervous system?

Thorcolumbar outflow

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What are the spinal roots of the sympathetic nervous system?

T1 - L2

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What is the structure of a sympathetic pathway?

Short pre-ganglionic, long post-ganglionic neurone

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What are the three places a sympathetic outflow may synapse?

At the same level as origin
At different level to origin
May not synapse in paraverterbral chain

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What neurotransmitter is used by pre-ganglionic neurones in sympathetic outflow?

Acetycholine for cholinergic receptors

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What receptors do post ganglionic neurones express?

Nicotinic receptors

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What type of neurotransmission do most sympathetic post-ganglionic neurones use?

Noradrenergic (secret noradrenalin

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What classes of adrenoreceptors exist?

a 1 & a 2

b 1 & b2

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What are the exceptions to the noradrenergic rule of sympathetic outflow?

Some sympathetic synapses, such as those in perspiration and ejaculation pathways are cholinergic

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What type of outflow is used by the parasympathetic nervous system?

Cranio-sacral outflow

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What is the structure of a parasympathetic pathway?

Long pre-ganglionic nerve fiber - short post-ganglionic nerve fibre

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What type of neurones are parasympathetic pre-ganglionic?

Cholinergic

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What receptors do post-ganglionic neurones express?

Nicotinic receptors

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What type of neurones are post-ganglionic parasympathetic?

Cholinergic

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What type of receptors do parasympathetic work on on cells?

Muscarinic, G-protein coupled

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For each organ, name the sympathetic receptor 
Heart
Airways
Pupil
Sweat Glands

Heart - B1
Airways - B2
Pupil - A1
Sweat Glands - A1 (M3)

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For each organ, name the sympathetic effect
Heart
Airways
Pupil
Sweat Glands

Heart - Increase rate/force of contraction
Airways - Relax
Pupil - Dilation
Sweat Glands - Localised secretion (a1), general secretion (m3)

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``` For each organ, name the parasympathetic receptor Heart Airways Pupil Sweat Glands ```

Heart - M2 Airways - M3 Pupil - M3 Sweat glands - None

How does adrenaline/noradrenaline interact with b - adrenoreceptors?

Activates G protein S Stimulates Adenylyl Cyclase Activates glycogenolysis, lipolysis

How does Acetylcholine interact with M3 receptors?

Gq Stimulates Phospholipase C Causes smooth Muscle Contraction

How does acetylcholine interact with M2 receptors?

Gi Inhibits Adenylyl Cyclase Stimulates K+ Channel, slowing of Cardiac Pacemaker

How does light interact with rhodopsin?

Gt Stimulates Cyclic GMP, Phosphodiesterase Visual Excitation

What happens when a1 receptors are stimulated by adrenaline?

Activates Gq Stimulates Phospholipase C Smooth Muscle Contraction

What happens when a2 receptors are stimulated?

G protein I activated | - Adenylyl Cyclase

What happens when M1 and M3 receptors are activated?

G protein Q activated | Activates phospholipase C

What happens when M2 receptors are activated?

G protein I activated | Inhibits adenylyl cyclase, stimulating K+ channel and causing slowing of Cardiac Pacemaker

What role does the sympathetic branch of the autonomic nervous system play control of blood vessels?

Innversates the smooth muscle in the walls of arteries, aterioles and veins. Causes vasoconstriction of arterioles via a1 receptors

What is the term for the constant control the sympathetic nervous system has over the vasculature?

Vasomotor tone

What is meant by saying vasomotor tone in skin is high?

arterioles, pre-capillary sphincters and arterio-venous anastomoses are generally shut down. Variation in sympathetic outflow produces large changes in skin blood for, for thermoregulation.

What is vasomotor tone in skeletal muscles?

high at rest, but in exercise is antagonised by vasodilator metabolites.

What is vasomotor tone in gut?

vasomotor activity is high until a meal is consumed, when various vasodilators produced in the gut tissue antagonise it.

What is the principal way in which distribution of flow around the body is controlled?

The interplay between sympathetic vasoconstrictor tone and the action of vasodilator substances

What can vascular tone in the skin and skeletal muscle also be used for?

Controlling peripheral resistance

Where is sympathetic outflow to blood vessels controlled from?

The brain, via vasomotorcentres in the medulla oblongata

What structures does the autonomic nervous system effect in the heart? (parasympathetic and sympathetic)

SA and AV nodes both affect heart rate

What does parasympathetic and sympathetic activity respectively?

Para - Slows heart | Symp - Speeds it up

What is the mechanism of control to decide whether heart should be slowed down or sped up?

Baroreceptors in arch of aorta and carotid sinuses detect pressure and feedback to the medulla oblongata, the control centre of autonomic activity

What is the hr if all autonomic inputs are pharmacologically blocked?

100 bpm

How is a normal resting heart rate of 60 bpm produced?

parasympathetic dominates the sympathetic at rest.

How are initial increases in heart rate determined?

Initial increases in heart rate are brought about by reduction in parasympathetic outflow. Increasing Sympathetic outflow makes further increases.

As well as speeding up heart rate, what is the other role of sympathetic nerve fibres?

Innervate ventricular cardiac myocytes, increasing force of contraction and cardiac output

What is the sympathetic pathway for control of the heart?

NA - B1 Receptors

What is the parasympathetic pathway for control of the heart

Ach - M2 receptors

If you gave someone an injection of adrenaline, what would happen?

There would be an increase in heart rate, stroke volume and therefore cardiac output The arterioles to the skin would vasoconstrict (action of adrenaline on α1 receptors) The airways would dilate (action of adrenaline on β2 receptors)

List the probable physiological effects of giving an individual a drug which antagonises the action of noradrenaline at a-adrenoreceptors.

Arteriolar vasodilation, reduces blood pressure and may cause postural hypotension Initial increase in heart rate mediated by baroreceptor reflex Relaxes GI and urinary sphincters

List the physiological effects of a poison | which inactivates acetylcholinesterase (such as a nerve gas or insecticide).

Ef fects on autonomic transmission: increased sal ivary, lacrimal , bronchial and G.I . secret ions, bronchoconstrict ion, reduced hear t rate and blood pressure, constr icted pupils Ef fects on neuromuscular junct ion: init ial ly muscular twitching then paralysis due to NMJ blockade Ef fects on the brain: init ial ly excitat ion causing convulsions, later depression of cerebral funct ion, unconsciousness and respiratory failure

Why would someone with inactivated acetylcholinesterase be paralysed?

The continued presence of ACh (the neurotransmi tter at the neuromuscular junct ion) wil l prevent subsequent contract ion of skeletal muscle due to depolar ising block via nicotinic ACh receptors

Parasympathetic control of the heart is via the ... nerve | Sympathetic control of the heart is via the ... nerves

Vagus Cardiac

What is vasoconstrictor tone due to?

The action of noradrenaline on a - adreno receptors

What is total peripheral resistance?

Blood pressure/ cardiac output

What are the sympathetic receptors of the heart?

What are the parasympathetic receptors of the heart?

What are the sympathetic receptors of the blood vessels to noradrenaline?

What are the receptors to adrenaline to the blood vessels within skeletal muscle? Whatdo they cause to happen?

B2 | Dilation

What are the sympathetic receptors of the liver and what do they stimulate?

a, b2 | Glycogenolysis and gluconeogenesis

What are the sympathetic receptors of the sweat glands? What do they cause to happen?

Ach, M | Secretion

What are the other proper sympathetic receptors of the sweat glands?

a, respond to circulating adrenaline