Lec 15: Hormones & Brain Function Flashcards
what are the 2 types of communication that occurs in neurons?
electrical
chemical
what is electrical communication of neurons?
WITHIN the neurons
transmission along the axon
what is chemical communication of neurons?
BETWEEN neurons
transmission at the synapse
list 6 components of the definition of a NT
1) exists in presynaptic axon terminals
2) presynaptic cells contains enzymes for synthesizing substance
3) substance is released when AP reach terminals
4) specific rec recognise the substance
5) application of the substance produces changes in postsynaptic potential
6) blocking release of the substance prevents nerve impulses
2 types of receptors for ACh and are they metabotropic/ionotrophic?
1) muscarinic = metabotropic
2) nicotinic (ionotrophic)
- muscle contraction
- cholinergic transmission in cortex
what are the DA receptors?? are they metabotropic/ionotrophic?
D1-D5 = metabotropic
- complex behaviours, motor function, reward, higher cognition
name the NE receptors
are they metabotropic/ionotrophic?
a1, a2, b1, b2= metabotropic
- visceral organs
- sympathetic NS, fight or flight
what are the 5-HT receptors?
are they metabotropic/ionotrophic?
5-HT1, 2, 3
- all but one subtype of 5-HT3 = metabotropic
- mood, sleep, higher cognition
are GABA receptors ionotropic or metabotropic??
GABA-A and GABA-C= ionotropic
GABA-B= metabotropic
what are the glutamate receptors?
are they metabotropic/ionotropic?
AMPA, kainate, NMDA= ionotropic
mGluR= metabotropic
ionotrophic VS metabotropic
IONotropic= allow different kinds of ions to travel in and out of the cell.
metabotropic= do not have a “channel” that opens or closes. Linked to another small chemical called a “G-protein.”
glutamatergic transmission uses which 3 receptors???
AMPA
Kainate
NMDA
(all ionotropic)
name 2 inhibitory transmitters in the brain
GABA
glycine
name the 3 classes and characteristics of GABA receptors
GABA-A= ionotropic, produce fast inhibitory effects via Cl channel
GABA-B= metabotropic, slow inhibiting effects through neurogliaform interneurons
GABA-C= ionotropic with Cl channel
how do GABA agonists work?
- potent tranquillizers
- allow influx of Cl, hyper-polarization and inhibitory effects
how does alcohol work in relation to GABA rec
at GABA-A receptors
- ionotropic
- fast inhibitory effects
what is the cause of drug abuse?
how to reduce?
rebellion, money, boredom, experimentation, thrill-seeking, desperation, self-medication
- education, coercion, punishment, environmental change, maturation, pressure to strop, life events
what is the cause of drug dependence?
how to reduce
genetics, brain chemistry sensitivity, input from the environment
- treatment to positively affect abnormal brain function to reduce need for drug
name 4 effects of alcohol on the brain
- effect is biphasic (initial stimulant phase followed by more prolonged depressant phase)
- activated GABA-A rec (coupled to chloride channel, inc post synaptic inhibition, hyperpolarization)
- chronic abuse damages nerve cells, and frontal lobes
- binge= brain damage
FASD
fetal alcohol spectrum disorders
- distinctive changes in facial features, stunted growth, intellectual disability, irritability, tremors, hyperactivity
- neural crest cells affected by alcohol, failure of closing
- fewer cerebral cortices, sometimes absence corpus callosum
- thickening of cortical mass, small brain
explain what happens to migration of neurons due to alcohol
- slow movement to the right place
- migrating neurons are immature, lacking dendrites, with only a soma and immature axon at this point (in neocortex)
- undifferentiated at the start of migration
- differentiation begins as neurons migrate
- they develop NT making ability (AP)
what are neuroepithelial cells?
neural stem cells
neuroepithelial cells of the ventricular zone do what??
give rise to radial glial cells that further differentiate into neurons or glial cells
what do radial glial cells do?
act as guide wires for migration of neurons
what are 3 characteristics of migrating neurons?
immature
only soma
immature axon
what is aggregation?
cells that are done migrating align themselves with other cells and form structures
what is aggregation?
cells that are done migrating align themselves with other cells and form structures
how many layers of the cortex?
6
which type of cells are the largest in the cortex?
pyramidal cells
what are the 2 types of ACh receptors?
nicotinic
muscarinic
what are nicotinic receptors?
- most ionotropic, excitatory
- muscles (antagonist= paralysis)
what are muscarinic receptors?
metabotropic
excitatory/inhibitory
what is the function of ACh in the CNS and PNS?
- associated with motor functions (heart/muscles)
- learning
- memory
relation between ACh neurons and alzheimers
cholinergic neurons are depleted in AD
where is DA found in the brain???
in the mesostriatal pathway
- originates in the midbrain
- specifically the substantia nigra
- innervates the striatum
mesolimbocortical DA pathway originates ….
projects….
DA in this pathway is involved in…
abnormalities associated with…
originates in midbrain (VTA)
- project to limbic system and cortex
- reward, reinforcement, learning
- abnormalities= schizophrenia, addiction
NE released in which 3 brainstem regions?
Locus coeruleus (pons)
lateral tegmental system (midbrain)
dorsal medullary group
NE systems modulate….
processes including mood, arousal and sexual behaviour
where are serotonergic cell bodies found??
raphe nuclei
- fibers project widely
5-HT implicated in….
sleep, mood, sexual behaviour and anxiety
what hormone does antidepressants act on???
inc 5HT activity
depending on receptor subtype
what are endocrine glands?
release hormones within the body
what are the 9 general principles of hormone action
1) act in gradual fashion
2) act by changing probability/intensity of behaviour
3) reciprocal relationship between behaviour and hormones
4) multiple effects, one behaviour can be affected by several hormones
5) pulsatile secretion pattern (burst)
6) some controlled by circadian clocks
7) interact with other hormones and change their effects
8) across species, structure is similar, actions vary
9) only affect cells with a receptor protein for the hormone
list the 5 ways in which neural and hormonal communications differ
1) neural communication travels to precise destinations. Hormonal spread through body, picked up by cells with the proper rec (multiplicity of action)
2) neural= rapid, hormonal- slower
- neuromodulators can influence activity of synaptic transmitters
3) distance traveled varies
4) neural messages= digital, sequences of all-or-none potentials
- hormonal messages= analog/graded in strength
5) neural communications sometimes under voluntary control
- hormones= involuntary
what is the chemical structure of :
- protein hormone
- amine hormone
- steroid hormone
protein= string AA
amine= modified AA
steroid= 4 rings of C
hormones exert effects on cells and tissues by:
promoting proliferation, growth and differentiation of cells and modulating cell activity
how do protein and amine hormones function?
- act rapidly
- when bind to extracellular part of a receptor, the receptor changes shape
- intracellular part activates 2nd messenger
how do steroid hormones work?
act slowly
when steroid-receptor complexes form, they alter protein production
long-lasting effects
- pass through membrane of the cell, bind to receptor in cytoplasm
- rec chaparone these bound rec steroid into the nucelus AFTER dimerization
- binding= conformational change
- makes another protein binding domain available, and dimer of protein can go in to regulate gene expression
hormones are regulated by which feedback system??
negative
- output feeds back and inhibits further secretion
what is an autocrine response?
involved endocrine gland releasing hormone and feeding back onto itself
- accumulation of hormone prevents further release
what is target cell feedback?
hormone acts on its target cells, has biological effect
- biological effect is detected by endocrine gland, inhibits further release
which region drives the endocrine gland via either neural or hormonal signals?
hypothalamic region
describe the 5 steps in brain regulation (feedback control)
hypothalamus --> (-) endocrine cells --> (+) target cells --> (+) biological response
–> [negative feedback]
name 2 other hormones involved in feedback control in anterior pituitary
1) tropic hormones (affect other endocrine glands)
2) releasing hormones (used by hypothalamus to control pituitary release of tropic hormones)
- first releasing hormones act on cells to release tropic hormones
what is the pituitary gland?
small structure at base of brain
release hormones that control the activity of bodys other hormone glands
2 parts of the pituitary gland
anterior pituitary (adenohypophysis)
posterior pituitary (neurohypophysis)
what is the pituitary stalk??
infundibulum
connects pituitary to hypothalamus
- contains BV and axons
describe the hormone production by the posterior pituitary
- terminate in capillaries in posterior pituitary
- direct effect from activating neurons within PVN of hypothalamus that will result in the release of hormones in capillary blood network
which 2 hormones does post pit secrete?
vasopressin (AVP)
oxytocin
what is AVP/vasopressin
- aka ADH (antidiuretic)
inc BP
inhibit urine production
what is oxytocin?
involved in reproductive and parenting behaviour
uterine contraction
milk letdown reflex
describe the hormone release by the ant pit?
- hypothalamic neurons synthesize releasing hormones
- axons converge on median eminence
- releasing hormones secreted via hypophyseal portal system
- releasing hormones carried to ant pit, release tropic hormones
hypothalamus is influenced by _____ ____, such as other hormones, and by ____ ____ from other brain areas
circulating messages
synaptic inputs
characteristics of people wit tumours of the anterior pituitary
reason???
tall, pronounced foreheads
– high GH secretion
name the 6 tropic hormones the ANT PIT releases
1) ACTH
2) TSH
3) FSH
4) LH
5) Prolactin
6) GH
what is ACTH
ANT PIT
adrenocorticotropic hormone
controls adrenal cortex and steroid hormone release
CRH–> ACTH–> adrenal cortex (kidney)–> secrete corticosteroids
what is TSH?
ANT PIT
thyroid-stimulating hormone
increases thyroid hormone release
TRH–> TSH –> thyroid–> thyroid hormones
gonadotropins influence the _____
gonads
what is FSH?
ANT PIT
follice-stimulating hormone
stimulate egg-containing follicles or sperm production
GnRH/GNIH—> FSH–> testes/ovaries–> androgens/estrogens
what is LH
ANT PIT
luteinizing hormone
stimulate follicles to form the corpora lutea
GnRH/GNIH—> LH–> testes/ovaries–> androgens/estrogens
what is prolactin
ANT PIT
stimulates lactation in females
involved in parental behaviour
prolactin-releasing peptid/prolactin-inhibiting factor –> prolactin–> mammary glands –> milk production
what is GH?
ANT PIT
growth hormone- aka somatotropin or somatotropic hormone
influence growth (mostly during sleep)
- stomach hormone ghrelin evokes GH release
somatocrinin(+)/stomatostatin (-)–> GH –> bones–> bone growth
where are the adrenal glands located?
on top of each kidney
% of adrenal cortex/medulla
80% adrenal cortex
20% adrenal medulla
adrenal cortex secretes steroid hormone called….
adrenocorticoids (adrenal steroids)
what are glucocorticoids?
subgroup of adrenocorticoids
involved with glucose metabolism
what is cortisol?
cortisol= humans corticosterone= mice/rats
glucocorticoids stress hormone
- inc blood glucose, breaks down protein
