PHYS: Autonomic Nervous System Flashcards
how are somatic, sympathetic and parasympathetic nerves formed?
- somatic (monosynaptic): just one cholinergic nerve (N receptor)
- sympathetic (bisynaptic): cholinergic nerve (N receptor) > mostly adrenergic nerve (a/B receptor)
- parasympathetic (bisynaptic): cholinergic nerve (N receptor) > cholinergic nerve (M receptor)
which neurons in the ANS are myelinated/unmyelinated?
- pre ganglionic myelinated
- post ganglionic unmyelinated
location of nerves in the sympathetic vs parasympathetic nervous system
- parasympathetic: craniosacral, ganglia are close to target organs
- sympathetic: thoracolumbar, ganglia are close to spinal cord, forming sympathetic trunk
length of nerve fibres in the parasympathetic vs sympathetic nervous system
- parasympathetic: long pre-ganglionic, short post-ganglionic
- sympathetic: short pre-ganglionic, long post-ganglionic
how are ACh and NA synthesised and terminated?
- Ach: synthesised in axon terminals and broken down by anticholinesterases
- NA: synthesised in cell body and reuptaken into presynaptic neuron (also a2 receptor on presynaptic controls -ve feedback)
2 plexuses which innervate the enteric nervous system
- myenteric: controls velocity and intensity of contraction
- submucosal: secretion and absorption
in the ANS, are ACh and NA consistently excitatory or inhibitory?
- neither, depends on the type of receptor on the target organ
types of ANS receptors
CHOLINERGIC
- nicotinic
- muscarinic (M1-M5)
ADRENERGIC
- alpha: a1, a2
- beta: B1, B2, B3
role of the hypothalamus in controlling the ANS + what is its major input and output
- ‘the boss’ - receives info from visceral organs, overall integration of ANS info and decides how to maintain homeostasis
- inputs: amygdala
- output: limbic system
role of the brain stem in controlling the ANS
- (esp. medulla oblongata and reticular formation)
- autonomic functions e.g. HR, breathing, swallowing etc
role of the cortex in controlling the ANS
- no direct effect but influences ANS via the limbic system (emotional processing which can lead to fight/flight)
paraventricular nucleus location + function
- located in hypothalamus
- hormonal control: pituitary gland = fluid balance (ADH) + milk production (oxytocin)
- other ANS control
amygdala
- group of nuclei in medial temporal lobe (part of limbic lobe)
- role in emotional responses and memory
role of the medulla oblongata
- regulates BP, HR etc via cardioregulatory and vasomotor centres
- regulates respiration
- regulates reflexes e.g. coughing, sneezing, vomiting, gag
location and function of the nucleus tractus solitarius (solitary nucleus)
- part of brain stem
- receives sensory input re: BP and cardiac function
- output via sympathetic stimulation of CVS
diabetic neuropathy + Sx
- hyperglycaemia and hyperlipidaemia damage nerves
- Sx: erectile dysfunction, postural hypotension, urinary incontinence, impaired sweating
Raynaud’s disease
- exaggerated sympathetic vasoconstriction in response to cold/stress (vasospasm - a1)
- Sx: skin turning white, red, blue
- can be caused by lupus
autonomic dysreflexia
- uncontrolled activation of ANS
- usually seen in ppl w/ quadriplegia or spinal cord injury above T6
how does the ANS relate to the male sexual response?
- erection triggered by parasympathetic NS
- orgasm + ejaculation triggered by sympathetic NS
- therefore anxiety (sympathetic) > inhibit erection and cause premature ejaculation
which organs aren’t innervated by both the sympathetic and parasympathetic nervous system?
- lungs: parasympathetic only but have B2 receptors which CIRCULATING adrenaline can bind to = sympathetic effect
- blood vessels: sympathetic only (a1, a2, B2, some B3)
- sweat glands: sympathetic only but use ACh (M3) instead of NA
- adrenal glands: sympathetic only
describe how the pupil dilates/constricts
- pupil constriction: circular muscle contracts, radial muscle relaxes
- pupil dilation: circular muscle dilates, radial muscle constricts
