CNS 3 Flashcards
where is the hypothalamus located?
below the thalamus
what is the hypothalamus involved in?
homeostatic control
by exerting control on pituitary gland
what does the hypothalamus regulate?
- hunger
- thirst
- temperature
- libido
what is the hypothalamus responsible for?
- fighting
- fleeing
- feeding
- sex
the hypothalamus links the nervous system to the endocrine system via the..
pituitary gland
what is the pituitary gland?
small pea sized gland of the endocrine system
hangs from hypothalamus
what does the anterior pituitary gland release?
- GH (growth hormone)
- THS (thyroid stimulating hormone)
- FSH (follicle stimulating hormone)
- LH (luteinising hormone)
- prolactin
- ACTH (adrenocorticotropic hormone)
what does the posterior pituitary gland release?
- ADH (aka vasopressin)
- oxytocin
what is the pineal gland?
small endocrine gland in vertebrate brain
what does the pineal gland do?
makes melatonin
where is the pineal gland located?
near epithalamus near centre of brain
between 2 cerebral hemispheres
where is NA a neurotransmitter?
PNS, CNS
what is the reticular formation composed of?
set of interconnected nuclei distributed throughout brainstem + into diencephalon
where is NA produced?
NA-ergic neurones
process starts with amino acid precursor of NA (tyrosine)
tyrosine is transported into the nervous system from the..
blood
once tyrosine is inside the neurone, it undergoes transformation by the action of 3 enzymes in what sequence?
- tyrosine hydroxylase converts tyrosine into DOPA
- DOPA decarboxylase converts DOPA into dopamine
- dopamine beta hydroxylase converts DA into NA
- phenylethanolamine-N-methyltransferase converts NA into adrenaline
which enzyme isn’t present in noradrenergic neurones?
phenylethanolamine-N-methyltransferase
NA and catecholamines are removed from the synapse by what?
amine pump on surface of presynaptic terminal
what is NA taken back and stored in vesicles / metabolised by?
monoamine oxidase (MAO)
the MAO form of uptake of NA is blocked by …
- cocaine
- amphetamines
- tricyclic antidepressants
progesterone increases..
MAO
estrogen inhibits…
MAO
the NA that diffuses away from the receptors is subjected to…. into the surrounding tissues and metabolised by…
extra-neuronal uptake
catechol-O-methyl-transferase (COMT)
what are the predominant alpha receptors?
where are they found and what are their effects?
- a1-adrenoreceptor
- smooth muscle, heart, liver
- vasoconstriction, intestinal relaxation, uterine contractions + pupillary dilation
what are alpha1 receptors linked to?
Gq proteins
activate smooth muscle contraction through IP3 signalling
where are alpha2-adrenoreceptors found
what are their effects?
platelets, vascular smooth muscle, nerve termini, pancreatic islets
platelet aggregation
vasoconstriction
inhibition of NE + insulin release
what are alpha2 receptors linked to?
Gi proteins
binding of alpha-agonist decreases intracellular cAMP—> smooth muscle contraction
what are selective alpha2-adrenoreceptor agonists used for?
treatment of hypertension
where are beta1-adrenoreceptors found and what are their effects?
myocardium
cause lipolysis + cardiac stimulation
inc intracellular cAMP
what are beta1-adrenoreceptors coupled to?
Gs proteins
where are beta2-adrenoreceptors found and what are their effects?
- lungs
- GI tract
- vascular smooth muscle
- skeletal muscle
- liver
- uterus
beta 2 agonists cause: bronchodilation
vasodilation
stimulation of adenylyl cyclase activity -> relaxes smooth muscles
what are beta2-adrenoreceptors coupled to?
Gs proteins
where are beta3-adrenoreceptors located, what are they coupled to and what are their effects?
adipose tissue
metabolism of lipids
Gs proteins
what is NE mostly used to treat?
low bp
what are beta blockers used to treat?
- glaucoma
- migraine
- cardiovascular problems
what are alpha1 blockers used to treat?
- high bp
- anxiety
- PTSD
what are alpha2 agonists used to treat?
have a sedating effect
what are the functions of NA?
- mood - deficiency of NA -> depression
- arousal - inc rel of NA -> wakefulness + alertness
- bp regulation - NA synapses form part of baroreceptor reflex pathway that regulates bp
clonidine and methyldopa are hypotensive
what does this mean?
cause hypotension when injected into medulla / 4th ventricle
dopamine is a neurotransmitter that …
plays role in pleasure, motivation, learning, memory, behaviour + movement coordination
DA is the major neurotransmitter of which 4 systems?
- mesolimbic
- mesocortical
- nigrostriatal
- tuberoinfundibulnar
nigrostriatal pathways
transmits DA from substantia nigra pars compacts to dorsal striatum
mesolimbic pathways
transmits DA from VTA (in midbrain) to ventral striatum
mesocortical pathways
transmits DA from VTA to prefrtonal cortex
tuberoinfundibulnar pathways
transmits DA from infundibular nucleus of hypothalamus to pituitary gland
what is DA metabolised by?
MAO and COMT
what are DA receptors members of?
G protein coupled receptors
what are the 5 subtypes of DA receptors
- D1-like
- D2-like
D1-like
D1 and D5
- coupled to G protein Gs-alpha
- activates adenylyl cyclase -> inc cAMP
D2-like
D2, D3 and D4
- coupled to protein Gi-alpha
- directly inhibits cAMP form by inhibiting adenelyl cyclase
what are the functions of dopamine?
- motor activity - deficiency —> Parkinson’s disease
- behavioural effects
- APG function: da inhibits prolactin
- vomiting - caused by da agonists
what are the 4 major diseases associated with dopamine?
- parkinsonism
- schizophrenia
- attention deficit hyperactivity disorder (ADHD)
- drug abuse + addiction
5-HT containing neurones in the brainstem are known as what?
raphe nuclei
the precursor in the biosynthesis of serotonin (5-HT) is ….. NOT tyrosine
tryptophan
5-HT is formed from dietary tryptophan, which is converted to ….. by ….
hydroxytryptophan by tryptophan hydroxylase
what do tricyclic anti-depressants do?
inhibit catecholamines
which then blocks neuronal uptake mechanisms of 5-HT
what are SSRIs?
selective serotonin reuptake inhibitors
constitute an imp group of anti-depressants + anxiolytics
what is 5-HT degraded by? and how?
MAO
5-HT -> 5-hydroxyindole acetaldehyde
dehydrogenated to 5-hydroxyindole acetic acid
excreted in urine
give the type, mechanism, and potential of the 5-HT3 receptor?
ligand gated Na+ + K+ cation channel
depolarising plasma membrane
excitatory
what are the functions of serotonin?
- mood - improves depressive states
- sensory transmission - inhibits pain impulse transmissions in spinal cord + brain
- temperature control
- APG function: influences release of gonadotrophins
- vomiting - 5-HT3 blocker used as anti-emetic
the site of greatest ACh synthesis in the brain is…
interpeduncular nucleus
what 2 precursors is ACh formed from?
- choline (comes from dietary + intraneuronal sources)
- acetyl coenzyme (made from glucose in mitochondria of neurones)
what enzyme is ACh synthesised from?
choline acetyl transferase (ChAT)
is a selective marker for cholinergic neurones
what are the 2 types of acetylcholine receptors (AChRs)?
- muscarinic receptors
- nicotinic receptors
both occur in CNS
muscarinic receptors
- found at NMJ of cardiac + smooth muscle
- glands
- post-ganglionic neurones of sympathetic nervous system
what is muscarine?
toxin produced by mushrooms
is AGONIST
what is atropine
antagonist
nicotinic receptors
- found at NMJ of skeletal muscles
- on post-ganglionic neurones of parasympathetic nervous system
what is nicotine?
agonist
what is curare?
antagonist
paralyses skeletal muscles
what are the 5 distinct subtypes of mACHRs?
- m2 + m4 : couple with Gi/Go (reduce intracellular cAMP)
- m1, m3 and m5 : couple with Gq / G11 (inc ca2+ via phospholipase C activation)
what are the functions of ACh?
- arousal
- learning
- short term memory
- motor control
loss of cholinergic neurones in the hippocampus is related to what?
Alzheimers disease
hyperactivity of cholinergic neurones in the corpus striatum leads to…
Parkinson’s disease
