Autonomic Physiology Flashcards
How does the nervous system branch out?
Central Nervous System
Peripheral Nervous System
How does the peripheral nervous system branch out?
Afferent Division - sensory
Efferent division - motor
Autonomic Nervous System
Somatic Nervous System
How does the autonomic nervous system branch out?
Parasympathetic nervous system: rest and digest
Sympathetic nervous system: fight or flight
Describe the length of parasympathetic neurons
Long preganglionic neurons
Short postganglionic neurons
What % of all parasympathetic outflow comes from the vagus nerve that supplies the thoracic and abdominal viscera?
75%
Describe the myelination in pre-ganglionic and post-ganglionic fibres in the autonomic nervous system
Pre-ganglionic fibre is small myelinated, post- ganglionic fibre is unmyelinated
Where do the ganglia lie in the sympathetic nervous system?
Paravertebral ganglia lie in the sympathetic trunk which is close to the spinal cord.
Prevertebral ganglia lie in the collateral ganglia
So trunk = paravertebral, anything else = prevertebral
What type of information does the ventral horn carry?
Neurons send fibres to the skeletal muscles, causing muscle contraction
What type of information does the dorsal horn carry?
Receive sensory information from all around the body
White ramus is what kind of ganglionic fibre and why?
Pre - ganglionic, because of the myelination
What is the grey matter made up of?
Cell bodies of the axons
What is white matter made up of?
Axons linking the different parts of grey matter together
Where do nerves leave the spine in the parasympathetic nervous system?
Cranial and sacral regions of the spine
Where do the ganglia lie in the parasympathetic nervous system?
Close to the target
How are sweat glands innervated?
Sympathetic cholinergenic fibers
What class of neurotransmitters are NO and peptides?
Nonchollinergenic and nonadregenic receptors
What does the autonomic nervous system control?
Things you don’t think about:
Blood vessels
Airways
Bladder
Eye
Sex organs
Cardiac muscle
Glands
How do the somatic and autonomic NS differ in their fibres?
Somatic NS: One fibre
Autonomic NS: two fibres
Preganglionic fibre
Post ganglionic fibre
Where are the cell bodies of motor neurons in the somatic nervous system?
Ventral horn of the spinal cord
What is the collection of cell bodies in the autonomic nervous system called?
Ganglion
What is the difference in the myelination of the pre and post ganglionic fibres of the autonomic nervous system?
The pre-ganglionic fibres are small and myelinated, whereas the post-ganglionic fibres are unmyelinated.
Describe the junction in the autonomic nervous system
Less specialised than the somatic nervous system
Metabotropic receptors
May excite or inhibit target cells
What does the sympathetic branch of the nervous system do?
Fight or flight
What does the parasympathetic branch of the nervous system do?
Rest and digest
What is the outflow of the sympathetic division of the autonomic nervous system?
Thoracolumbar outflow
T1-L5
What is the outflow of the parasympathetic division of the autonomic nervous system?
Craniosacral outflow
Cranial nerves (CN3.7,9,10)
Sacral spinal cord (S2-S4)
Discuss sympathetic fibre length
Short preganglionic
Long postganglionic
Discuss parasympathetic fibres
Long preganglionic
Short postganglionic
What do short preganglionic fibres indicate?
Ganglia are very close
What nerve represents the main components of the parasympathetic nervous system?
The vagus nerve oversees an array of bodily functions, including control of mood, immune response, digestion, and heart rate.
Where do sympathetic ganglia lie?
Close to spinal cord in sympathetic chain (paravertebral ganglia) or in (prevertebral) ganglia
What does the neurotransmitter acetylchloline act on?
Cholinergic receptors which can be:
- Nicotinic receptors (have integral ion)
- Muscarinic receptors (G protein-coupled)
Where do parasympathetic ganglia lie?
Close to target organ
What does the neurotransmitter noradrenaline act on?
Adrenergic receptors which can be:
α receptors - α1, α2
β receptors - β1, β2
Discuss parasympathetic neurotrasnmitter pathway
Acetylcholine neurotransmitter on the cholinergic nicotinic receptor of the autonomic ganglionic
Acetylcholine neurotransmitter on the cholinergic muscarinic receptor of target tissue
Discuss sympathetic neurotransmitter pathway
Acetylcholine neurotransmitter on the nicotinic receptor of the autonomic ganglionic
Norepinephrine neurotransmitter on the adrenergic receptor of target tissue - could be α receptors or β receptors
What do sympathetic postganglionic cells of the adrenal medulla release?
Adrenaline (80%) and noradrenaline (20%) into the blood which acts on α receptors or β receptors
What do sympathetic cholinergic fibres innervate?
Sweat glands
Sympathetic as they have a short pre-ganglionic fibre which synapses onto a long post-ganglionic fibre.
What do some postganglioinic fibres use?
Non-adrenergic non-cholernergic transmitters (NANC) eg peptides
How does the sympathetic nervous system work on the radial muscle of the eye?
Activates α1 receptors on radial muscle of the iris.
Radial muscle contracts, makes pupil wider.
How does the parasympathetic nervous system work on the radial muscle of the eye?
Activates muscarinic receptors on sphincter of the iris.
Contracts sphincter muscle, making pupil smaller.
How does the sympathetic nervous system work on the ciliary muscle of the eye?
Activates β2 receptors on ciliary muscle around lens.
Ciliary muscle relaxes and eye focuses far away.
How does the parasympathetic nervous system work on the ciliary muscle of the eye?
Activates muscarinic receptors on ciliary muscles around the lends.
Ciliary muscle contracts and eye focuses close up
How does the sympathetic nervous system work on the heart?
Activates β1 receptors on the myocytes.
Increases strength of contraction.
Activates β2 receptors on pacemaker cells.
Increases heart rate.
How does the parasympathetic nervous system work on the heart?
Activates muscarinic receptors on the pacemaker cells.
Decreases heart rate.
Little effect in myocytes and strength of contraction.
How does the sympathetic nervous system work on the lungs?
Activates β2 receptors on smooth muscle of airways.
Makes smooth muscle relax and dilates airways.
How does the parasympathetic nervous system work on the lungs?
Activates muscarinic receptors.
Makes smooth muscle contract and constricts airways.
How can adrenergic receptors be useful in clinic?
β1 antagonist (eg atenolol)
- decreases heart rate, limiting effect on airways
β2 agonist (eg salbutamol)
- dilates airways, limited effect on the heatr
How does the sympathetic nervous system work on the blood vessels?
Activates α1 receptors on smooth muscles of vessels
Makes smooth muscle contract and blood flow decrease
Activates β2 receptors on smooth muscle of vessels
Makes smooth muscle relax and blood flow increases
How does the parasympathetic nervous system work on the blood vessles?
Usually no effect
How does the sympathetic nervous system work on the salivary glands?
Activates β receptors
Stimulates thick secretion rich in enzymes
How does the parasympathetic nervous system work on the salivary glands?
Activates muscarinic receptors
Stimulates profuse watery secretion
What are salivary glands an example of?
Dual innervation with non-antagonistic actions
How does the sympathetic nervous system work on the bladder?
Activates β2 receptors on smooth muscle of bladder wall
Relaxes smooth muscle and reduces pressure
Activates α1 receptors on smooth muscles of sphincter
Contracts smooth muscle and stops urination
How does the parasympathetic nervous system work on the bladder?
Activates muscarinic receptors on bladder wall
Contracts smooth muscle and increase pressure
Activates muscarinic receptors on sphincter
Relaxes smooth muscle and causes urination
How does the sympathetic nervous system work on the reproductive tract?
Activates α1 receptors on smooth muscle of urethra
Contracts smooth muscle and causes ejaculation
How does the parasympathetic nervous system work on the reproductive tract?
Activates muscarinic receptors on smooth muscle of corpus cavernosum
Relaxes smooth muscle and causes erection
What is the reproductive tract an example of?
Dual innervation with complementary effects
What is the central control of the autonomic reflex?
Integrated in brain, mainly hypothalamus, thalamus and brainstem
eg baroreceptor
Integrating centre looks at the information
Coordinates a sympathetic and parasympathetic outflow to vary heart rate, strength of contraction and constriction of blood vessels accordingly
What do α1 receptors work on?
Radial muscle of eye
Blood vessels
Bladder
Reproductive tract
What do β1 receptors work on?
Heart - myocytes
What do β2 receptors work on?
Ciliary muscles of eye
Heart - pacemaker cells
Lungs
Blood vessels
Salivary glands
Bladder
