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Flashcards in Endocrinology Deck (659)
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241

Describe the steps toward spontaneous inhibition of PRL

  1. Spontaneous production of Ca2+ signal in the hypothalamus
  2. Dopamine synthesis in hypothalamus changes
  3. Levels of dopamine alter according to a tonic pattern
  4. Stimulation + suppression of adenohypophyseal PRL production + release

242

List the stimuli of PRL production

  • Pregnancy
  • Suckling
  • Stress
  • Sleep
  • Hypoglycaemia
  • Dopamine

243

List the inhibitors of PRL production

  • Dopamine
  • GABA
  • GAP
  • Drug: Bromocryptine

244

Positive physiological stimuli and negative effects

245

Serotonin opioids

246

Neurosecretion + Peripheral blood-derived signals

247

PRL

248

Trophormone

249

Udder:

  • Suckling
  • Maternal behaviour

Other: Increase of metabolism

250

'Tonic' central inhibition

251

  • Dopamine
  • GABA
  • GAP

252

PRL regulation by neurosecretion involves which hormones?

  • TRH
  • GnRH
  • VIP
  • Galanin

253

PRL regulation by peripheral blood involves which hormones?

  • Serotonin
  • Angiotensin-II
  • Oestrogens

254

MSH

  • Formed from ACTH
  • Stimulation of pigment granule production
  • Transport along the microtubule system → Decoloration of cells

255

Effect of MSH on pigment cells

  • Microtubule system from the nucleus
  • MSH causes:
    • Granules to migrate along microtubules
    • Even distribution of granules, darkening cell

256

Function of melatonin

Hormone:

  • Stimulates migration of scattered pigment granules
  • Back to the vicinity of the nucleus

257

Pineal gland produces

Produces serotonin + melatonin

258

Melatonin secretion

  • Circadian rhythm, affected by light
  • Decreased illumination acts positively
  • Increased daylight acts negatively

Some species:

  • Melatonin production positively influences sexual activity
  • In other species, it may have a negative influence

 

259

Describe the innervation of the pineal gland

  • Not directly connected to the CNS
  • Innervated by postganglionic sympathetic fibres

260

Describe the effect of decreased light intensity on the pineal gland

  1. Decreased illumination to retina → Sympathetic activity
  2. Suprachiasmatic nucleus (SCN) connection
  3. Excitation from cervical ganglion → CP
  4. Norepinephrine released here → NAT synthesis (used in melatonin synthesis)

261

Title the figure

Innervation of the pineal gland

262

Norepinephrine

263

Beta-receptor + Adenylate cyclase

264

AMP → cAMP

265

Give the steps of Melatonin production

266

Give the degradation of melatonin

267

How does melatonin have a counter-effect on MSH?

  1. It inducts concentration of pigment granules
  2. Skin becomes pale

268

Give the three effects of melatonin in mammals

  • Sexual function
  • Psychic effects
  • Defence against free radicals

269

(Mammals) Influence of melatonin on the sexual cycle

  • Termination of the production of:
    • GnRH
    • FSH
    • LH
  • Sheep - Initiates oestrous cycle
  • Horse - Inhibits estrous cycle

Relevance to seasonality

270

Describe melatonin levels at different human sexual maturation stages

Melatonin inhibits sexual maturation in humans

  • High in children between 1-6 years old
  • Decreases later during puberty: GnRH synthesis occurs
  • Decrease with age