Flashcards in Session 4 - The Autonomic Nervous System and the CVS Deck (64):
Give two factors which are under the control of the autonomic nervous system
What three physiological features does the autonomic nervous system control to have an effect?
Rate and force of contraction in the heart
What are the two sections of the autonomic nervous system?
The sympathetic and the autonomic
What are the two series of neurones in the ANS called?
Pre-ganglionic and post-ganglionic
What is a ganglion?
A collection of nerve cell bodies in the PNS
What is a nuclei?
Collection of nerve cell bodies in the CNS
Describe the structure of the autonomic nervous system
Pre-ganglion with nerve cell body in CNS
Post-ganglion with nerve cell body in PNS
What is the outflow of the sympathetic nervous system?
What are the spinal roots of the sympathetic nervous system?
T1 - L2
What is the structure of a sympathetic pathway?
* Short pre-ganglionic, long post-ganglionic neurone
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
What neurotransmitter is used by pre-ganglionic neurones in sympathetic outflow?
Acetycholine for cholinergic receptors
What receptors do post ganglionic neurones express?
What type of neurotransmission do most sympathetic post-ganglionic neurones use?
Noradrenergic (secret noradrenalin
What classes of adrenoreceptors exist?
a 1 & a 2
b 1 & b2
What are the exceptions to the noradrenergic rule of sympathetic outflow?
Some sympathetic synapses, such as those in perspiration and ejaculation pathways are cholinergic
What type of outflow is used by the parasympathetic nervous system?
What is the structure of a parasympathetic pathway?
Long pre-ganglionic nerve fiber - short post-ganglionic nerve fibre
What type of neurones are parasympathetic pre-ganglionic?
What receptors do post-ganglionic neurones express?
What type of neurones are post-ganglionic parasympathetic?
What type of receptors do parasympathetic work on on cells?
Muscarinic, G-protein coupled
For each organ, name the sympathetic receptor
Heart - B1
Airways - B2
Pupil - A1
Sweat Glands - A1 (M3)
For each organ, name the sympathetic effect
Heart - Increase rate/force of contraction
Airways - Relax
Pupil - Dilation
Sweat Glands - Localised secretion (a1), general secretion (m3)
For each organ, name the parasympathetic receptor
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?
Stimulates Phospholipase C
Causes smooth Muscle Contraction
How does acetylcholine interact with M2 receptors?
Inhibits Adenylyl Cyclase
Stimulates K+ Channel, slowing of Cardiac Pacemaker
How does light interact with rhodopsin?
Stimulates Cyclic GMP, Phosphodiesterase
What happens when a1 receptors are stimulated by adrenaline?
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?
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?
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
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
Ef fects on neuromuscular junct ion: init ial ly muscular twitching then paralysis due to
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
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?
What are the sympathetic receptors of the liver and what do they stimulate?
Glycogenolysis and gluconeogenesis
What are the sympathetic receptors of the sweat glands? What do they cause to happen?