The autonomic nervous system Flashcards
Semester 1 year 1
What is in the sensory part of the Peripheral Nervous System?
-somatic nervous system
-visceral nerves
What does the somatic nervous system do?
Gathers information from skeletal muscle and skin
What do the visceral nerves do?
Innervate the bladder +gastrointestinal tract
What is an afferent nerve fibre/neuron?
Anything going from the sensory part to the CNS
What makes up the CNS?
-brain
-spinal cord
What is in the motor part of the peripheral nervous system?
-somatic nervous system
-autonomic nervous system
What is the somatic nervous system involved in?
-involved in muscle contraction at skeletal muscle
-voluntary
What is the autonomic nervous system involved in?
-involved in smooth muscle and cardiac muscle contraction
-involved in gland secretion
-involuntary
What is an efferent nerve fibre/neuron?
Takes information from CNS into the periphery
What are the 2 major efferent pathways in the autonomic nervous system?
-sympathetic nervous system
-parasympathetic nervous system
When and how is the sympathetic nervous system activated?
when - exercise, excitement, emergency, embarrassment
how - co-ordinated, whole body response or discrete and organ specific
How and when is the parasympathetic nervous system activated?
when - digestion, defecation, urination (diuresis)
how - discrete and organ specific
What is stimulated by the parasympathetic nervous system?
-eyes
-heart –> decreases natural heart rate
-GI tract –> secretions + movement of smooth muscle
-bladder –> bladder wall relaxes + contraction of bladder sphincter
-reproductive organs
What is stimulated by the sympathetic nervous system?
-eyes –> pupil dilation + eyelid contraction to increase visibility
-heart –> increased rate + force of contraction
-blood vessels –> b.v to areas that don’t need blood constrict + b.v to important areas relax to increase blood flow
-lungs –> dilation of bronchioles so more oxygen in and more carbon dioxide out
-liver –> synthesises and releases glucose for muscle contraction
-adrenal medulla –> releases insulin
-bladder –> smooth muscle relaxes to prevent urination
-reproductive system –> prevent orgasm
How is the response from the 2 pathways of the autonomic nervous system balanced?
-generally innervate the same tissues but have opposing effects
-actions are antagonistic, but work synergistically
-allows for rapid, precise control of tissue function
Where does mainly sympathetic innervation occur, rather than a balance between the 2 pathways?
-sweat glands
-hair follicles
-blood vessel smooth muscle
-adrenal medulla
Describe preganglionic neurons
-always cholinergic fibres, so acetylcholine is its primary neurotransmitter
-acetylcholine activates the nicotinic acetylcholine receptor (ligand gated) on postsynaptic cell
What is the importance of the vagus nerve?
-carries roughly 80% of total parasympathetic outflow
-carries tonnes of visceral afferents
-important for internal state of the body
What does the spinal cord do?
-mediated autonomic reflexes
-receives sensory afferent + brainstem input
What does the brainstem nuclei do?
-mediate autonomic reflexes
-medulla contains vagus nerve + where a lot of autonomic output is
What does the hypothalamus do?
-involved in integration + coordination
-involved in: feeding, thermoregulation, circadian rhythms, water balance, sex drive, reproduction
What does the forebrain do?
-regulates ANS output
-minimal conscious cortical control but cortical processes do regulate autonomic output
What do the visceral afferents do?
-regulate ANS output
-sensory input from visceral afferent neurons takes priority over cortical function –> nothing else seems to matter
Describe the general organisation of the autonomic nervous system for both the parasympathetic and sympathetic?
-preganglionic neuron in CNS
-sends an axon into periphery + synapses with postganglionic neuron in peripheral ganglion
-postganglionic neuron sends axon out to target cell
What is a ganglion?
A group of neurons that have a similar function
Describe transmission via the sympathetic pathway
-short, cholinergic preganglionic neurons from thoracic + lumbar spinal cord
-long, adrenergic postganglionic neurons
-target tissues express alpha and beta adrenergic receptors
What are the neurotransmitters used in the sympathetic nervous system?
-acetylcholine between pre and postganglionic neuron
-noradrenaline from postganglionic to target cell (main neurotransmitter)
Describe transmission via the parasympathetic nervous system
-long, cholinergic preganglionic neurons from brainstem + sacral spinal cord
-short, cholinergic postganglionic neurons
-target tissues express muscarinic acetylcholine receptors
What are the main neurotransmitters in the parasympathetic nervous system?
Acetylcholine for pre + postganglionic neurons
