Autonomic ns Flashcards
Is the autonomic nervous system voluntary or involuntary?
Largely outside the influence of voluntary control
Define autonomic
Self-governing
What are the effectors of the autonomic nervous system?
Smooth muscle
Cardiac muscle
Glands
What does the autonomic nervous system receives info about?
The state of the body
What is the main function of the ans?
Maintaining homeostasis
Role of the sympathetic ns?
Fight or flight
When is the sympathetic ns activated?
Exercise
Excitement
Emergency
Embarassment
What causes the sympathetic ns to activate?
Coordinated whole body response or
Discrete and organ specific
What is the function of the parasympathetic ns?
Rest and digest
When is the pns activated?
Digestion
Defecation
Diuresis
How is the pns activated?
Discrete organ specific manner
What happens to the eyes in sns?
Pupils dilate to see as much visual field as possible
What happens to the heart in sns?
Heart rate and contractility increases
What happens to blood vessels in sns?
Dilation leading to heart and muscles,
Constriction to digestive system,
Blood redirection (via coupled receptors)
What happens to the lungs in sns?
Widening of bronchioles and bronchi
Breathing rate increases
What happens to the liver in sns?
Regulation of glucose
Liver is stimulated to release more glucose
Gluconeogenesis
Glycolysis
What are the discrete functions of the sns?
Reproductive systems cause a male and female orgasm
What happens to eyes in pns?
Pupil size decreases
What happens to the heart in pns?
Heart rate and contractility (in the atria) decreases
What happens to the GI tract in pns?
Increased secretion to aid digestion
What happens to the bladder in pns?
Voluntary control with the cortical system contracts the bladder to force urine out
What happens to reproductive organs in pns?
Maintenance of erection in males
What happens to blood vessels in sns as signal rate increases?
The blood vessels constrict
What happens to blood vessels in sns as signal rate decreases?
The blood vessel dilates
What is the organisation of ans? What is the exception?
CNS ->
Peripheral ganglion ->
Target cell
Exception of adrenal medulla in sns
What type of fibre is a preganglionic neuron?
Cholinergic fibres
What is a cholinergic fibre?
A fibre that releases ACh as their primary neurotransmitter
What does ACh activate?
Nicotinic acetylcholine receptors
Where do short, cholinergic preganglionic neurons come from?
The thoracic and lumbar spinal cord
What would the G-protein couple to on the heart?
Ga(s) and Gq for adrenergic receptors
What is the sympathetic pathway?
Preganglionic fibre ->
Short cholinergic preganglionic neurons from t and l spinal cord ->
Long adrenergic postganglionic neurons ->
Target tissues express alpha and beta adrenergic receptors
What is the adrenal medulla?
The adrenal gland on top of the kidney
How is the adrenal medulla different to other pathways?
Chromaffin cells release mainly adrenaline
Target tissues express alpha and beta adrenergic receptors
What is the parasympathetic pathway?
Long cholinergic preganglionic neurons from brainstem and sacral spinal cord ->
Short cholinergic postganglionic neurons ->
Target tissue expresses muscarinic ACh receptors
What is cranial nerve 10?
Vagus nerve
What % of parasympathetic flow does cranial nerve 10 outflow?
80%
What are the 2 main components of ANS?
Spinal cord
Brainstem nuclei
What are the 2 main components of ANS?
Spinal cord
Brainstem nuclei
Role of the spinal cord
Mediates autonomic reflexes
Receives sensory afferent and brainstem input
Role of the brainstem nuclei
Mediates autonomic reflexes
What does the hypothalamus coordinate?
Feeding
Thermoregulation
Circadian rhythms
Water balance
Sexual drive
Reproduction
How does the forebrain regulate ANS?
Cortical processes regulate output
e.g. anxiety and fear induce fight or flight
How do visceral afferents regulate ANS?
Sensory input from visceral afferent neurons take priority
e.g. bladder distension
