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Fundamental Neuroscience > Neuropeptides and Hormones > Flashcards

Neuropeptides and Hormones Flashcards

1
Q

What are neuropeptides?

(2 marks)

A
  • Small proteins produced by neurons
  • Act on GCPRs and responsible for slow onset, long lasting modulation of synaptic transmission
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2
Q

What are the two families of neuropeptides?

(2 marks)

A
  • Small molecule NT: GABA, glutamate etc,
  • Peptide NT: range of brain and gut peptides (in particular hypothalamus)
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3
Q

Name some of the mammalian neuropeptides:

(5 marks)

A
  • Opioids
  • Pituitary peptides
  • Hypothalamus releasing peptide
  • Peptide neurotransmitter
  • Brain-gut peptides
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4
Q

How is proopiomelanocortin (POMC) produced in the secretory granule?

(9 marks)

A
  • Made in humans on chromosme 2, coding in exons 2 and 3 give rise to production of pre-POMC
  • Signal peptide: instructs machinery of cell as to where to send product - to Golgi cortex & comes out secretory granule (only in POMC)
  • Signal peptide cleaved off and POMC enters granule whcih is then spliced by PC1 (pro-convertase enzymes)
  • Formation of PC1 forms ACTH and ß LPH
  • ^^ subject to PC2 to get γMSH and αMSH
  • Cleave off 5’ part and PC1 cleaves another structure forming ACTH and ßLPH
  • ßLPH cleaved by PC1 forming: γLPH and ßMSH & ßendoprhin
  • ACTH cleaved by PC2 forming αMSH and CLIP peptide
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5
Q

In cows, why does the relative expression of Kiss/Dyn change?

(2 marks)

A
  • Due to reporoductive cycle
  • BUT can be co-expressed in neurons and secretoru granules that contain both of them
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6
Q

What is the difference in function between G proteins GHRH and SRIF?

(2 marks)

A
  • GHRH:
    • ​Signals through Gαs which activates adenylate cyclase
  • SRIF:
    • ​Binds to SSTR1-5 receptor and activates Gαi which inactivates adenylate cyclase
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7
Q

What loop of the G-protein receptor interacts with the G-protein?

(2 marks)

A
  • 3rd intracellular loop
  • Binding to receptor causes α-subunit to dissociate and activate substrate molecule
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8
Q

What does the G protein OXY do?

(4 marks)

A
  • Binds to OTR
  • Causes dissociation of Gαq
  • Activates PLC and produces IP3 and DAG
  • IP3 increases intracellular Ca2+
  • DAG increases extracellular Ca2+
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9
Q

What is another word for the anterior pituitary?

A

Adenohypophysis (pars distalis)

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10
Q

What is another word for posterior pituitary?

A

Neurohypophysis (pars nervosa)

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11
Q

What is another name for intermediate lobe?

A

Pars intermedia

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12
Q
A
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13
Q

Outline the basis of posterior pituitary circulation.

(6 marks)

A
  • Pituitary sits in sella turcica
  • PP receive blood from inferior posterior artery by capillary plexus of infundibular process
  • Blood taken away from posterior hypophyseal veins
  • Pituitary gland contains neuron terminals with cell bodies in paraventricular nucleus and supraoptic nucleus
  • Neurons project down through pituitary stalk and terminate in posterior pit
  • So pituitary stalk acts as neuronal tract
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14
Q

Outline the blood supply for the anterior pituitary.

(6 marks)

A
  • Blood supply from superior hypophyseal artery
  • Enters primary plexus of hypophyseal portal system
  • Blood leaves via hypophosal portal veins (blood leaves secondary plexus by anterior hypophosal veins)
  • Which goes down pit stalk and into secondary plexus of hypophyseal portal system
  • Neuropeptides made in hypothalamus
  • Neurons release into primary plexus, go down pitutitary stalk by hypophyseal veins and activate/ inhibit cells in AP
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15
Q

Describe what the structures and their location in the picture.

A
  • Rostral end of hypothalamus indicated by anterior commissure and potic chiasm
  • Preoptic area on front wall of 3rd ventricle
  • Caudally find nuclei on either side of 3rd ventricle
  • Supraoptic nucleus (either end of optic chiasm)
  • Periventricular nuclei up against 3rd vwntricle wall, laterally and dorsally from that is paraventricular nucleus
  • Further back is arcuate nucleus has neurons projecting to median emminence and primary plexus
  • Completely caudally is posterior nuclei and mammillary body
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16
Q

What hormones are present in the posterior pituitary?

(2 marks)

A
  • Vasporession
  • Oxytocin
17
Q

What is the function of Vasopressin?

(2 marks)

A
  • Controls kidney at higher concentrations and can cause vasoconstriction
  • Associated with diabetes insipidus-receptor as isn’t responding so get lots of dilute urine
18
Q

What controls the levels of secretion of vasopressin?

A

Plasma osmality and blood volume

19
Q

What is the function of oxytocin?

(5 marks)

A
  • Milk ejectoin
  • Uterine contraction
  • Suckling:
    • information comes from spinal reflex arc to paraventricular nucleus. Stimulus is cholinergic and transmitted to nerve endings in PP
    • Causes Ca2+ uptake - depolarisation and exocytosis of oxytocin into circulation
20
Q

What are the different anterior-pituitary axes?

(5 marks)

A
  1. HP-thyroid
  2. HP-adrenal
  3. HP-Growth hormone
  4. HP-prolactin
  5. HP-Gonodal
21
Q

What is produced in the HP-thyroid axis and what does it do?

(5 marks)

A
  • Neurons at top produce TRH (thyrotropin releasing hormone)
  • Found in parvocellular portion of paraventricular nucleus
  • TRH - 3 AA peptides and therefore has short half life
  • TRH activates thyrotrophs which then release TSH - protein hormone
  • Thyrotophs under single positive regulation
22
Q

What is produced in the HP-adrenal axis and what does it do?

(5 marks)

A
  • Corticotrophs (placental hormones)
  • Controlled by positive regulation by 2 NP one being vasopressin which influences ACTH secretion
  • Corticotrophs found in anteriore pituitary and stimulate secretion of ß endorphins from anterior pituitary and other POMC derivatives
  • Corticotrophs give neuronal input to neurons from limbic system and brain stem areas for autonomic controls
  • CRH - important in stress response
23
Q

What is produced in the HP-growth hormone axis?

(3 marks)

A
  • Somatotrophs which are under negative and positive regulation
  • Positive regulation by GHRH - produced by neurons who’s cell bodies are in arcuate nucleus
  • Negative regulation by somatostatin (SRIF) - cell bodies of neurons that make this found in perventricular nucleus
24
Q

What is produced in the HP-prolactin axis and what factors affect its functionand expression?

(6 marks)

A
  • Lactotrophs which are under negative regulation
  • Secreted by neurons in dorsomedial area of arcuate nucleus and inferior ventromedial nucleus
  • Secretion is inhibted by DA neurons which inhibits the release of _prolactin from lactotrophs_
  • Damage to pit stalk prevetns DA coming down stalk and get Loss of secretion of all pit hormones bar prolactin which increases
  • Less intracellular Ca2+ causes reduced exocytosis of secretory resideus containing prolactin
  • Inhibition of adenyl cyclase further reduces Ca2+ (in cell) and causes decreased prolactin gene expression
25
Q

What is produced in the HP-gonodal axis?

(3 marks)

A
  • Gonadotrophs - under positive regulation by GnRH neurons
  • cell bodies in casculosom of lamina terminalis
  • Neurons project down to medium emminence and elicit secretion of LH and FSH to control reproductive
26
Q

How is GnRH stored and secreted?

(3 marks)

A
  • Primary signalling pathway is through activation of PLC which releases IP3 and DAG and activation of PKC
  • Signals transmitted through JNK pathway to activate transcription of gene for ß-subunit of either LH or FSH
  • Increase in cAMP and intracellular Ca2+ from activation of voltage sensitive Ca2+ channels
27
Q

What is the basic stages of GnRH migration during neurogenesis?

(5 marks)

A
  1. Neurogenesis
  2. Initiation
  3. Divergence
  4. Progression
  5. Arrest
28
Q

What is the developmental process of the GnRH system.

(9 marks)

A
  • Neurogenesis controlled by FGFs - GnRH neurons orginiate in late olfactory placode
  • Movement of GnRH neurons to prefrontal cortex, and adhesion to axons in vomero nasal organ
  • GnRH converge away from dorsal VMO across cribiform plate and into main part of brain. Controlled by Sema3A & Nrp1/2
  • @ same time as divergence, have proliferation of gonadotrophs in anterior pituitary controlled by GATA2 (TF)
  • Neurons progress down neuronal guides & controlled by some other proteins Acl, SDF-1, Nhlh2 and progressing down towards AV3v
  • Neurons interact with Kisspeptin (kp) neurons at specific region then terminate their migration and kp no longer expressed
  • GnRH neurons porject down to median emminence @ same time kp neurons and GnRH neurons begin to form their synaptic connections with other neurons
  • Leptin controls entry to pubity: need gd fat storage, activates neurons to activate kp neurons which activates GnRH neurons and BAM pubity
29
Q

What happens in the hypothalamic -pituitary circulatory system?

(4 marks)

watch video on this to clarify!!!

A
  • Hypothalamic neuron receives signal hormones go into primary plexus of closed portal system that connects hypothalamus with AP
  • Hormones then go down to portal vessel to secondary plexus and move via fenestrations into extracellular space in vicinity of AP cells containing AP hormones
  • GHRH binds to its receptor (GHRH-R) a GCPR on somatrophs of AP and increases cAMP which causes increased synthesis of GH
  • GHRH stimulates proliferation of these cells through activation of MAP kinase pathway

Fundamental Neuroscience (19 decks)

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