Neuro - Autonomic Nervous System Flashcards
What is the autonomic nervous system?
Motor sub division of the peripheral nervous system, concerned with subconscious control of the body (homeostasis)
What structures in the body are involved in the autonomic nervous system?
Cardiac muscle
Smooth muscle
Viscera
Skin
What 2 pathways form the afferent arm of the PNS?
Somatic sensory
Visceral sensory
What is the visceral motor?
Sub division of motor neurones, concerned with autonomic nervous system and contains sympathetic and parasympathetic arms.
What is the parasympathetic usually involved with?
Rest and digest (routine maintenance)
What is the sympathetic usually involved in?
Fight or flight (mobilisation and increases in metabolism)
Where are the parasympathetic and sympathetic arms usually found?
Usually found together apart from some exceptions e.g. the lungs
What is the parasympathetic effect on the heart?
Decreases heart rate and contractility
What is the parasympathetic effect on the stomach?
Increases gastric juice secretion and motility
What is the parasympathetic effect on the pupils?
Constriction
What is the parasympathetic effect on the liver?
Increase in bile secretion
What is the sympathetic effect on the heart?
Increase heart rate and contractility
What is the sympathetic effect on the stomach?
Decrease gastric juice secretion and motility
What is the sympathetic effect on the pupils?
Dilation
What is the sympathetic effect on the liver?
Increased hepatic glucose output
What controls the blood vessel tone - both vasoconstriction and vasodilation?
Sympathetic nervous system
What is the baroreceptor response to normal blood pressure?
Parasympathetic nervous system is promoted and sympathetic is inhibited, to decrease (maintain) heart rate
What happens to blood pressure when we stand up?
Blood pressure drops
What happens to baroreceptors following a fall in blood pressure?
Decrease in firing
What happens as a result of decreased baroreceptor firing?
Decreased parasympathetic activation/stimulation
What happens if the parasympathetic stimulation decreases?
Disinhibition of the sympathetic nervous system
What is the effect of the sympathetic nervous system on the heart?
Increase heart rate and contractility, to increase and correct the reduced blood pressure
Where do visceral motor nuclei originate?
Hypothalamus
Describe the course of autonomic nerves after they originate in the hypothalamus?
Continue down the brainstem and spinal cord, and eventually travel to their innervated tissue
Generally, what are the 2 parts of an autonomic nerve?
Pre ganglionic
Post ganglionic
What is a ganglion?
Cluster of nerve bodies
Describe the pre-ganglionic fibres of the parasympathetic nervous system
Long
Describe the post-ganglionic fibres of the parasympathetic nervous system
Short
Where do pre ganglionic parasympathetic neurones travel to/synapse?
Travel far to their respective organ and synapse close to the tissue that they innervate
Describe the pre-ganglionic fibres of the sympathetic nervous system
short
Describe the post-ganglionic fibres of the sympathetic nervous system
Long
Where do pre-ganglionic sympathetic neurones travel to/synapse?
Not very far - synapse in the sympathetic trunks close to the spinal cord
Why is the sympathetic nervous system usually more controlled?
To allow for mass activation of the fight or flight response when in danger thus increasing chances of survival
How is the sympathetic nervous system usually under tighter control?
Travel in sympathetic trunks which are close to the spinal cord and run parallel with it.
What neurotransmitters and receptors are found at the preganglionic sympathetic synapses?
ACh
Nicotinic
What neurotransmitters and receptor are found at the preganglionic parasympathetic synapses?
ACh
Nicotinic
What neurotransmitters and receptor are found at the postganglionic sympathetic synapses?
Noradrenaline
Adrenergic
What neurotransmitters and receptor are found at the postganglionic parasympathetic synapses?
ACh
Muscarinic
Where is there only one sympathetic (pre-ganglionic) fibre found as opposed to 2?
Adrenal gland
Where do post ganglionic fibres usually release neurotransmitters?
Into the tissue they innervate.
Along with the enteric system, how does the body regulate itself when we smell food?
Parasympathetic stimulation whereby gastric juice secretion increases and the stomach becomes more motile, ready for digestion
What happens when we are exposed to bright sunlight?
Parasympathetic stimulation whereby pupils constrict to reduce sunlight travelling through the pupil to the retina.
Where in the viscera are sympathetic neurones not found?
Lungs
How do we get bronchodilation in the lungs?
Hormonal control - adrenaline form the blood increases bronchodilation
How would you describe the effect of the autonomic nervous system?
Involuntary
What is the micturition reflex?
Sensory information in the bladder is relayed back to the CNS and the visceral motor then controls the release of urine.
What muscle does the parasympathetic nervous system control?
Detrusor muscle
What muscle does the sympathetic nervous system control?
Internal sphincter muscle
What happens when pressure builds up in the bladder ie from urine?
The sympathetic arm is still in charge while pressure is building up, therefore the internal sphincter is contracting and holding urine.
What happens when the bladder is full?
Sensory information is relayed to the brain and the parasympathetic arm is turned on, while the sympathetic arm is turned off. This means the internal sphincter relaxes and detrusor contracts to expel urine
Why do we not urinate involuntarily if the micturition reflex is under autonomic control?
We still have somatic control - the external sphincter is under GSE control so we can urinate as and when we want to.
What are nicotinic ACh receptors linked to?
Na+ channel
Where is nicotinic ACh found?
All autonomic intermediate ganglia for fast propagation
Where may we find slower muscarinic ACh receptors?
Parasympathetic post ganglionic synapses
How is Acetylcholine synthesised?
Choline combines with acetyl CoA under acetyl transferase to form acetylcholine.
How is acetylcholine broken down/taken back up?
Broken down to choline and Acetyl via acetylcholinesterase. Choline is take back into pre-synapse via choline re uptake protein.
How can we use acetylcholinesterase to treat Alzheimer’s?
AChE can be blocked to allow for a build up of ACh which therefore can have a powerful therapeutic effect.
What is step 1 of noradrenaline synthesis?
Tyrosine is converted to DOPA via tyrosine hydroxylase
What is step 2 of noradrenaline synthesis?
DOPA is converted to Dopamine via DOPA decarboxylase
What is step 3 of noradrenaline synthesis?
Dopamine is converted to noradrenaline via Beta-hydroxylase in vesicles
How is noradrenaline taken back up into the presynapse?
Via MOA-O (pre-synaptic cell) or COMT (glial cell)
How do we get adrenaline from noradrenaline?
Via phenylethanol methyl transferase
