Autonomic NS :( Flashcards
What is the autonomic nervous system?
A component of the peripheral nervous system which controls involuntary processes.
What does the ANS control?
Smooth muscle in the following:
-blood vessels
-airways
-bladder
-eyes
-gut
-sex organs.
Also controls cardiac muscles and glands (salivary and sweat).
Name the three subdivisions of the ANS.
Sympathetic NS
Parasympathetic SN
Enteric NS
Where are the cell bodies of motor units found?
In the dorsal horn of the spinal cord.
Describe the role of motor units in the somatic nervous system.
Send axons through the ventral root all the way to the periphery where they meet their target- skeletal muscle.
In the ANS, how many fibres are used to get the axons to their target?
2
What is the ganglion?
Collection of neuronal cell bodies
Name the fibre before and after the ganglion in the ANS.
Before= pre-ganglionic fibre
After= post-ganglionic fibre
Briefly describe the structure of the pre-ganglionic fibre and the post-ganglionic fibre.
Pre-ganglionic fibre=small myelinated
Post-ganglionic fibre=unmyelinated
p.s. Myelinated axons are the neuron axons which are covered with myelin sheaths. Unmyelinated axons are the axons which are not covered with myelin sheaths.
List the different targets for the post-ganglionic fibres.
Smooth muscle, glands, cardiac muscle and GI neurons.
What is the target for the autonomic NS?
Skeletal muscle
Name the synapses of the somatic NS.
Highly specialised neuromuscular junction.
What is an endplate potential?
The voltages which cause depolarization of skeletal muscle fibres caused by neurotransmitters binding to the postsynaptic membrane in the neuromuscular junction
Where are neurotransmitters released in the ANS?
In the interstitial fluid- will bump around until it finds it’s receptors.
One post ganglionic fibre can innervate how much tissue?
A large area of tissue.
What kind of receptors are found in the somatic NS?
Ionotropic receptors.
What kind of receptors are found in the autonomic NS?
Metabotropic receptors.
The second messenger used in the ANS can influence?
If the receptor will excite or inhibit the target.
Sympathetic=?
Fight or flight.
Para sympathetic=?
Rest and digest
Where is the outflow for the sympathetic division in the spinal cord?
Between T1 and L2.
Thoracic 1-12, Lumbar 1-2.
Short preganglionic fibres=?
Ganglia are v close to the spinal cord.
For the sympathetic division, what do the very long post ganglionic fibres lead to?
The targets
Where is the outflow for the parasympathetic diviosn?
The cranial and sacral region of the spinal cord (craniosacral).
Cranial I-XII
Sacral S1-5
Describe the structure of pre ganglionic and post ganglionic fibres.
Pre ganglionic fibres are v long.
Post ganglionic fibres are v short.
Where do the short post ganglionic fibres lie in the parasympathetic division?
On the target or very close to the target.
Ganglia lie close to the spinal cord in which division of the ANS?
Sympathetic.
What does acetylcholine act on?
Cholinergic receptors- either nicotinic or muscarinic.
What does noradrenaline act on?
Adrenergic receptors- either alpha or beta
What does the sympathetic and parasympathetic preganglionic fibres release as their neurotransmitter?
What does it bind to?
Acetylcholine
Binds to nicotinic cholinergic receptors.
In the parasympathetic system, what neurotransmitters does the pre ganglionic fibres release?
Acetylcholine BUT binds to muscarinic cholinergic receptors.
In the parasympathetic system, what does the post ganglionic fibres release?
Noradrenaline which binds to alpha/beta adrenergic receptors.
There is a ganglionic fibre, both pre and post, which does not act as the rest. It is found in the adrenal medulla gland.
Where do they release the neurotransmitter?
Into the bloodstream and acts as a hormone.
When this neurotransmitter is in the bloodstream, what is released into the blood?
adrenaline and noradrenaline (~80%:20%)
Where will the neurotransmitters released into the blood stream (adrenal medulla gland) bind to?
Alpha or beta adrenergic receptors.
Name some features of a sympathetic response (think fight or flight/rest and digest).
-Airways dilated
-Heart rate faster
-Blood diverts to muscle
-Heart beats stronger
-Mouth becomes dry
-Hair stands on end
-Stored energy released
-Pupils dilated
Name some features of a parasympathetic response (think fight or flight/rest and digest).
-Airways constrict
-Heart beat slows down
-Pupils shrink
-Hair lies flat
-Blood diverts to gut
-Mouth drools
-Energy stored
What are the parasympathetic and sympathetic responses dependant on?
Which neurotransmitter is released and which receptor it binds to.
Describe the effect of a sympathetic response on the eye (pupil).
Pupils dilate to let in more light.
Radical muscles contract and pupil becomes darker as the alpha 1 receptors on radical muscle of the iris have been activated.
Describe the effect of a parasympathetic response on the eye (pupil).
Pupil constricts.
Muscarinic receptors on the sphincter muscle of the iris are activated.
Describe the effect of a sympathetic response on the eye (lens).
Beta 2 receptors on ciliary muscle around lens are activated.
Ciliary muscle relaxes and eye focuses far away.
Describe the effect of a parasympathetic response on the eye (lens).
Muscarinic receptors on ciliary muscle conracts.
Eye focuses close up.
Describe the effect of the sympathetic response on the heart.
Beta 1 receptors on the pacemaker cells are activated by noradrenaline and adrenaline.
Increases heart rate.
Beta 1 receptors on the myocytes are activated.
Increases strength of contraction.
Describe the effect of the parasympathetic response on the heart.
Muscarinic receptors on pacemaker cells are activated.
Decrease in heart rate.
Little effect on myocytes so little effect on contraction.
Describe the effect of the sympathetic response on the lungs.
Beta 2 receptors on smooth muscle of airways is activated.
Smooth muscle relaxes and airways become dilated.
Describe the effect of the parasympathetic response on the lungs.
Muscarinic receptors are activated.
Airways constrict.
Discuss why it is important that we know all the subtypes of adrenergic receptors?
Therapeutically useful-
β2 agonist- dilates airways, limited effect on the heart
β1 antagonist- decreases heart rate, limited effect on airways
Describe the effect of the sympathetic response on the blood vessels.
Alpha 1 receptors on smooth muscle of vessels are activated.
Smooth muscle contracts and blood flow decreases.
Activates Beta 2 receptors on smooth muscle of vessels.
Muscle relaxes and blood flow increases.
Describe the effect of the parasympathetic response on the blood vessels.
Usually no response.
Describe the effect of the sympathetic response on salivary glands.
Activates Beta receptors.
Stimulates thick secretion rich in enzymes.
Describe the effect of the parasympathetic response on salivary glands.
Activates muscarinic receptors.
Stimulates profuse watery secretion.
Describe the effect of the sympathetic response on the bladder.
Beta 2 receptors on the smooth muscle of bladder wall are activated.
Smooth muscle relaxes and pressure is reduced.
Activates α1 receptors on smooth muscle of sphincter
Contracts smooth muscle and stops urination
Describe the effect of the parasympathetic response on the bladder.
Activates muscarinic receptors on bladder wall.
Contracts smooth muscle and increases pressure.
Activates muscarinic receptors on sphincter
Relaxes smooth muscle and causes urination
Describe the effect of the sympathetic response on the reproductive tract.
Alpha 1 receptors on smooth muscle of urethra are activated.
Smooth muscle relaxes and causes ejaculation.
Describe the effect of the parasympathetic response on the reproductive tract.
Activates muscarinic receptors on smooth muscle of corpus cavernosum
Relaxes smooth muscle and causes erection.
Name two types of reflexes associated w the sympathetic and parasympathetic responses of the ANS.
Spinal reflexes
Learned reflexes
Give an example of a learned reflex.
Urinary control after learning as a baby, where it is a spinal control.
What do baroreceptors do?
Detect changes in blood pressure.
What muscle(s) does the ANS innervate?
Smooth and cardiac muscle.
What muscle(s) does the SNS innervate?
Skeletal muscle
What do muscle fibres regsiter?
Change of length and the difference in length between the start and end of a change in muscle length
