Lecture 15 - (ANS) Neuroanatomy And Divisions Flashcards
What functions does the Autonomic Nervous system do?
All involuntary/vegetative functions
Is the Autonomic Nervous System Afferent or efferent?
Entirely efferent but is regulated by afferent inputs
How does the ANS differ to the Somatic/voluntary system?
Somatic is responsible for voluntary actions like skeletal muscle contractions
ANS is completely separate, does involuntary actions
What are the 2 divisions of the (efferent) ANS?
Sympathetic
Parasympathetic
What does the sympathetic nervous system do?
Resonds to stressful situations
Fight or flight responses
What are some examples of responses the sympathetic nervous system may produce?
INC HR (+ve chronotropy)
INC Force of contraction (+inotropy)
INC BP
What is the parasympathetic nervous system responsible for?
Regulates basal activities
Rest and digest responses
Which part of the spinal column do the Preganglionic neurones of the SYMPATHETIC nervous system emerge from?
Thoracic
Lumbar
What key endocrine gland receives sympathetic stimulation from the AUTONOMIC nervous system?
Adrenal gland
(Adrenal medulla)
Where do the Preganglionic neurones of the Parasympathetic nervous system originate from?
Craniomedullary region
Sacral region
What is the main Cranial nerve which provides lots of Parasympathetic innervation?
Vagus Nerve/Cranial nerve X
Are the Preganglionic neurones of the ANS myelinated or unmyelinated?
Myelinated
Are the Postganglionic neurones of the ANS myelinated or unmyelinated?
Unmyelinated
What is the relative lengths of the Preganglionic and then postganglionic neurones in the parasympathetic nervous system?
Preganglionic neurones = Long
Postganglionic neurones = Short
What is the relative lengths of the Preganglionic and then postganglionic neurones in the sympathetic nervous system?
Preganglionic neurones = Short
Postganglionic neurones = Long
What neurotransmitter is used by all pre-ganglionic neurones?
ACh
They are cholinergic
What type of receptors are present at the synaptic junction between the pre and postganglionic neurone in the ANS (both the sympathetic and parasympathetic)?
Nicotinic Acetylcholine receptors (nAChr)
What type of receptor is the nAChr that is present between the pre and postganglionic neurones in both the sympathetic and parasympathetic NS?
Ligand gated ion channel
What type of receptor is present on the effector tissues following a postganglionic neurone in the PARASYMPATHETIC nervous system?
Cholinergic:
Muscarinic (ACh) receptors
What type of receptor is present on the effector tissues following a postganglionic neurone in the SYMPATHETIC nervous system?
Adrenergic receptor
In the SYMPATHETIC nervous system, what is the neurotransmitter which binds to the adrenergic receptor on the effector tissue?
Noradrenaline
What type of receptors are the Muscarinic and Adrenergic receptors found following the postganglionic neurones of the ANS on the effector tissues?
G-protein coupled receptors
Do action potentials get conducted at a higher velocity in the Parasympathetic nervous system or sympathetic nervous system?
Why?
Parasympathetic nervous system
The preganglionic neurone is the longer neurone, this neurone is myelinated, therefore theres more myelination in the parasympathetic nervous system
What is the exception to all sympathetic post-ganglionic neurones being adrenergic receptors?
Sweat glands and hair follicles
Releases ACh that acts on Muscarinic receptors (not noradrenaline)
What is the exception to all sympathetic post-ganglionic neurones being adrenergic receptors?
Sweat glands and hair follicles
Releases ACh that acts on Muscarinic receptors (not noradrenaline)
What other chemicals can act as neurotransmitters?
ATP
Nitric Oxide (NO)
What receptors are always found in the somatic nervous system at neuromuscular junctions?
Nicotinic ACh receptors
nAChr
What cells produce noradrenaline and adrenaline?
Chromaffin cells
Where are Chromaffin cells located?
Adrenal medulla
What type of cells are chromaffin cells?
Differentiated postganglionic sympathetic neurones
Where do chromaffin cells release adrenaline and noradrenaline?
Into blood (not onto a target tissue)
What receptors are affected by the parasympathetic release of ACh in the heart?
Where in the heart are they found?
M2
In SAN + AVN
What parasympathetic effect does ACh have on M2 receptors in the heart?
Bradycardia (-ve chronotropy, SAN)
Reduced cardiac conduction velocity (-ve dromotropy, AVN)
What receptors are affected by the parasympathetic release of ACh in smooth muscle?
M3
Where are M3 receptors located?
Smooth muscle in Bronchioles of lungs
What parasympathetic effect does ACh have on M3 receptors in the lungs/bronchioles?
Bronchoconstriction
How does the parasympathetic nervous system cause penile erection?
Nitric oxide stimulates gAMP production
gAMP allows blood vessels to open
What receptors are affected by the sympathetic release of Noradrenaline in the heart?
Where in the heart are they found?
B1
SAN + Ventricles
What receptors are affected by the sympathetic release of Noradrenaline in the heart?
Where in the heart are they found?
B1
SAN + Ventricles
What sympathetic effect does noradrenaline have on B1 receptors in the heart?
Tachycardia (+ve chronotropy in SAN)
Increased force of contraction (+ve inotropy, ventricles)
What receptors are affected by the sympathetic release of Noradrenaline in the lungs/bronchioles?
B2
What sympathetic effect does noradrenaline have on B2 receptors in the lungs?
Bronchiole dilation
Smooth muscle relaxes to dilate the airways
What adrenergic receptors are present in the blood vessels?
a1 and B2
What receptors are affected by the sympathetic release of Noradrenaline in the vasculature?
a1
B2 normally affected by adrenaline
What sympathetic effect does noradrenaline have on a1 receptors in the vasculature?
Mainly arteriolar and venous contraction
However arteriolar relaxation does happen in some vascular beds
Increased sympathetic activity, more adrenaline and noradrenaline causes what effects in the heart, most blood vessels and blood vessels in exercising muscles and airways?
Heart = +chrontropic and +ve inotropic
Most blood vessels = Vasoconstriction
Blood vessels in airways and exercising muscles = Vasodilation
What receptors are stimulated when there is increased sympathetic activity releasing more adrenaline and noradrenaline in the heart, most blood vessels and the blood vessels of the airways and exercising muscles?
Heart = B1
Most blood vessels = a1
Lung and exercising blood vessels = B2
How do you remember what GPCRs are present in the heart?
How do you remember what GPCRs are present in the lungs?
How do you remember what GPCRs are present in the vascular smooth muscle?
What can bind to the receptors in vascular smooth muscle?
Heart: B1 = sympathetic (Gs) since only 1 Heart M2 = parasympathetic since add 1 to number of B receptor B(1+1) = 2 so M2
Lungs: B2 = sympathetic (Gs) since 2 lungs. M3 = parasympathetic since add 1 to number of B receptor (B2+1) = 3 so M3
Vascular smooth muscle: only sympathetic A1 and B2. A1 = Gq vasoconstriction noradrenaline agonist. B2 = Gs vasodilation adrenaline agonist
Noradrenaline binds to A1 and normal levels of circulating adrenaline bind to B2
At very high concentration, adrenaline binds to A1 causing vasoconstriction
