Wk8-9 AUTONOMIC NERVOUS SYSTEM Flashcards
Functions of hypothalamus
metabolism
Mediation of stress
reproductive behaviour and growth
body temperature
ANS + endocrine function
2 important regions of hypothalamus
Paraventricular nucleus
Median eminence
Paraventricular nucleus
2 parts
lateral = magnocellular neurons
medial = parvocellular neurons
Median eminence
contains blood vessels that are striated
This is part of the BBB still allowing movement of hormones
2 main parts of pituitary gland
Anterior pituitary
Posterior pituitary
Anterior pituitary
master gland controlling other glands including, thyroid, adrenal and mammory glands.
Anterior pituitary pathway
Parvocellular neurosecretory cells produce neuro-hormones (releasing factors)
released into the vicinity of portal vessels in the median eminence cells,
transported to anterior pituitary
cause the release of hormones from specialised secretory cells
Paraventricular nucleus neuro-hormones
Gonadotropin releasing hormone (GnRH), pre optic area
Thyrotropin releasing hormone (TRH), magnocellular (for body), parvocellular (for brain)
Corticotropin releasing hormone (CRH), parvocellular
Growth Hormone, Releasing Hormone (GHRH), parvocellular
Posterior pituitary pathway
vasopressin (also called anti diuretic hormone)
oxytocin release (magnocellular).
These are not released in portal system, they are neurotransmitters in brain.
Stress hormones is …. pituitary gland function
anterior
Stress hormone pathway
stress detected by brain
Corticotropin releasing hormone (CRH) released from nerves in PVN.
Transported to anterior pituitary by portal system
Acts on corticotrophs (type of cell) causing release adrenocorticotropic hormone
Acts on cortex of adrenal gland causing cortisol release into blood
Mobilises energy stores and suppresses immune system
Sex hormones are controlled by
hypothalamus and pituitary
Sex hormone pathway
Psychological and sensory influences detected by brain
Gonadotropin releasing hormone (GnRH) released from preoptic area of hypothalamus (not PVN).
Transported to anterior pituitary by portal system
Acts on gonadotrophs causing them to release folic stimulating hormone (FSH) + lutenising hormone (LH)
Acts on ovaries and testes
In females, causes estrogen release (cyclic release of hormones for menstrual cycle)
Vasopressin
Magnocellular neurons direct straight to the posterior pituitary gland, no portal systems in median eminence needed.
End in conjunction with fenestrated vessels, dumping their contents into them and therefore causing vasopressin release.
How is vasopressin release stimulated
by dehydration, changes in tonicity, detected by osmoreceptors in the forebrain and info sent to magnocellular neurons.
Hemorrhage (blood loss), detected by blood/ cardiac volume receptors in forebrain or recepotrs in kidney which release angiotensin.
Oxytocin
Stimulated by suckling of newborn babies, crying from mothers own or even unrelated babies.
oxytocin magnocellular neurons activated.
posterior pituitary release oxytocin
affects breasts releasing milk
leptin
Ob gene (obesity gene) product
circulates in the bloodstream in proportion to fat mass.
inhibits promoting neurons and excites inhibiting neurons.
2 types of neurons contained in arcuate nucleus
orexigenic
anorexigenic
orexigenic neurons
PROMOTE FEEDING
NeuropeptideY (NPY)
Agouti Related Peptide (AgRP)
axonal projections in paraventricular nucleus through dedicated NPY receptors
anorexigenic neurons
INHIBIT FEEDING
Proopiomelanocortin (POMC)
Cocaine Amphetamine Regulated Transcript (CART)
Active ingredient acts to inhibit effects of feeding in the paraventricular nucleus
Starvation response
Orexigenic neurons activated
Inhibited secretion of hypophysiotropic hormones in the paraventricular nucleus
promote energy expenditure (metabolism to lose weight gained by now eating)
Full response
Anorexigenic neurons activated
Promoted secretion of hypophysiotropic hormones in the paraventricular nucleus
inhibition energy expenditure (metabolism to halt losing energy as have stopped eating)
Short term food regulation
Ghrelin hunger hormone builds up in the brain before and reduced after a meal.
After a meal, satiety hormones increase to say you are not hungry anymore.
Gastric distension of stomach activates stretch receptors = Helps to say we are full.
Liking pathways
objective affective reaction that is mediated for taste in the brain by mu opoids at nucleus accumbens
Wanting pathways
an objective motivational process that is often termed “incentive salience”
mediated by dopamine
What is the function the the ANS
looks after the body as a whole, allowing the individual to survive and reproduce.
ANS in the spinal cord
coming out of the side and middle of the spinal cord (lateral, middle).
Sensory information comes in the dorsal root.
The ANS nerves function
uses nerves to enhance or suppress activity.
para and sympa are functionally opposing and will not work at the same time
Neurotransmitter pathway
Transmitter precursor taken up into nerve terminal
metabolising enzymes form neurotransmitter.
stored in vesicles so it doesn’t break down (Nitric oxide not stored as it is labile).
Exocytotic Vesicle release contents occurs due to AP.
Visceral efferent in the ANS spray neurotransmitter around in the effector tissue
These receptors are all metabotropic, which are sensitive to low doses all over the place. set up large numbers of second messengers within their cell.
Describe an ANS junction
Not a synapse, a junction
varicosities contain vesicles along axons
Every nerve that has it’s cell body in the CNS and comes out to become part of the ANS…
uses acetylcholine as its main neurotransmitter
Includes pre-ganglionic nerves
includes para postganglionic nerves
What is a NANC system
main transmitter neither ACh or NA.
non adrenergic non cholinergic
Sympathetic ANS
flight/fight response
brain (pre, myelinated) and spinal nerve (post, unmyelinated)
communicate in ganglion.
NORADRENILINE
SYMPATHETIC
Synthesised in vesicles
acts on alpha and beta adrenoceptors
ADRENOCEPTORS
Alpha:
noradrenaline potent excitatory/contraction
sit under nerve, most likely affected
Beta:
isoprenaline potent
inhibitory (except heart excitation)
away from nerves
ATP acts as a
co transmitter. It is released along with NA
Parasympathetic ANS
rest/digest response
preganglionic straight from brain, long neurons.
ganglion on edge of organ
pelvic organs at bottom of back nerves from end of spinal cord
ACETYLCHOLINE
PARASYMPATHETIC
synthesised in cytoplasm of a varicosity, transported to vesicles.
acts on muscarinic receptors
ACh removed by acetylcholinesterase, choline taken back up
Nicotinic receptors
acted on by ACh
terminals of preganglionic nerves coming from CNS of parasympathetic
NITRIC OXIDE
PARASYMPATHETIC
synthesised on demand, not stored in vesicles
increase in cytoplasmic calcium required
inhibits smooth muscle contraction
Outline the adrenal medulla
inner part of an adrenal gland,
hormones initiate the flight or fight response, adrenaline and noradrenaline.
Energy homeostasis
- ANS controls glucose conversion to glycogen in the liver and muscle.
isn’t working = diabetes
Leptin and Insulin from food intake = brain not hungry anymore
Brown and white fat
ANS controls interchange between white and brown fat by glitazones
Human sexual response: males
Penile artery:
Nitric oxide = vasodilator
Noradernaline = vasoconstrictor
Vas Deferens/Ejaculation :
ATP = 1st fast contraction
Noradrenaline = 2nd slow contraction
Erection: parasympathetic nervous system supplies arteries, it does not usually supply arteries. enzyme digests = stop erection
How does viagra work
Viagra inhibits enzyme breakdown so that cGMP lasts a bit longer and the erection remains.
Viagra cannot work if the nerves are totally severed no neurotransmitter is even produced for Viagra to inhibit.
Sexual response: Females
Vaginal secretion: CGRP – vasodilator (sensory)
Where do drugs NOT affect neurotransmission
Ion exchange pumps
ACh inhibition
Botox inhibits ACh, injected into specific muscles
Antichonilesterases can be targeted to help with myasthenia graves and alzheimers
NA inhibition
Blocked NA release by noradrenergic neuron blocking drugs, stop sympathetic responses
Activated NA release by drugs taken up into terminal causing NA release,
+ affect uptake 1 process leaving more NA enhance transmission
+ inhibit break down
what are activating NA drugs called
indirect sympathomimetics = mimic response indirectly
Targeting receptors
has more precise affects than targeting transmitters
Agonists
stimulate
suffix is mimetics
Antagonists
inhibit
suffix is lytics
Nictonic receptor drugs
too hard to target as they have complex systems and responses.
Muscarinic receptor drugs
muscarinic agonist = para response
muscarinic antagonist = oppose response
