Pituitary gland: 1. Weight 2. Diameter 3. Size

1. 0.5-1.0 g 2. 1 cm diameter 3. pea

Powerpoint 5 Flashcards by Sophie Theron

What 5 different hormones does the pituitary gland secrete and what sub-gland do each of these hormones act on?

Prolactin (PRL) –> lactation
Thyrotrophin / thyroid stimulating hormone (TSH) –> act on thyroid gland
Adrenocorticotrphin (ACTH) –> action on the adrenals
Luteinizing hormone (LH) and follicle stimulating hormone (FSH) –> act on the gonads (ovaries and testes)
GH

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What controls the pituitary gland?

The nervous system via the hypothalamus

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Pituitary gland:

Weight
Diameter
Size

0.5-1.0 g
1 cm diameter
pea

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By how much % does the pituitary gland increase in size during pregnancy?

30%

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The hypothalami-hypophyseal tract is derived from two different _______ components.

ectodermal (outermost layer of cells or tissue of an embryo in early development)

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What is the anterior pituitary derived from?

Rathke’s Pouch: outgrowth of the buccal cavity detaches itself and becomes anterior pituitary

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What is the posterior pituitary derived from?

The infundibulum develops from an outgrowth of the neuro-ectoderm from the floor of the 3rd ventricle. It gives rise to the pituitary stalk, the median eminence and the POSTERIOR PITUITARY

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The _______ pituitary is highly vascularized.

anterior: note capillary bed in median eminence connected to portal veins the a 2nd capillary bed in anterior pituitary - some retrograde flow to allow hormonal feedback from pituitary to hypothalamus (short loop)

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What hormones does the hypothalamus relay to the posterior pituitary?

vasopressin

oxytocin

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Which section of the neurosecretory neuron of the hypothalamus relays vasopressin to the posterior pituitary?

Pupraoptic

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Which section of the neurosecretory neuron of the hypothalamus relays oxytocin to the posterior pituitary?

Paraventricular nucleus

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The posterior pituitary is an _______ of the hypothalamus.

extension

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When using the term “Hypothalamic Nuclei” what does Nuclei refer to?

The cell bodies of the neurons which produce the hypothalamic hormones

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What two nuclei are associated with the posterior pituitary?

Supraoptic nuclei

2. Paraventricular nuclei

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What nuclei is associated with the anterior pituitary?

Hypothalamic-hypothysiotropic nuclei

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The hypothalamus receives signals from all areas of the brain - what do these signals trigger?

They trigger exocytosis of hormone vesicles from the axon terminal endings

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Which 5 neurotransmitters are involved in sending signals to hypothalamus?

neuro-epinephrine
epinephrine
dopamine
serotonin
acetylcholine

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How has the hypothalamus demonstrated some degree of autonomy (freedom from external control or influence)?

Via maintenance of VERY LOW levels of basal GH, FSH, and LH excretion from the anterior pituitary after surgical disconnection of the hypothalamus from the brain

What does the posterior pituitary control in the body?

Water balance (blood volume, intake - thirst, output - urine volume)

What does the anterior pituitary control in the body?

Metabolic rate, stress response, growth, reproduction, lactation

What are the 5 subgroups of cells located in the anterior pituitary? Pituitary population? Product? Target?

- corticotrophs
  - 15-20%
  - ACTH / betalipotropin
  - adrenal gland / adipocytes / melanocytes
- mammotrophs/lactotrophs
  - 10-15%
  - PRL
  - breasts / gonads
- thyrotrophs
  - 3-5%
  - TSH
  - thyroid gland
- gonadotrophs
  - 10-15%
  - LH / FSH
  - gonads
- somatotrophs
  - 40-50%
  - GH
  - All tissues, liver

Hypothalamic hormones controlling the anterior pituitary: How does TRH (Tyrotrophin-releasing hormone) control the anterior pituitary?

Stimulates release of TSH and PRL, minor stimulation of FSH release

Hypothalamic hormones controlling the anterior pituitary: How does GnRH (Gonadotrophin-releasing hormone) control the anterior pituitary?

Stimulates release of GH

Hypothalamic hormones controlling the anterior pituitary: How does GHRH (Growth hormone-releasing hormone) control the anterior pituitary?

Stimulates release of GH

Hypothalamic hormones controlling the anterior pituitary: How does Growth Hormone Release-Inhibiting Hormone or (SMS) Somatostatin control the anterior pituitary?

inhibits release of GH; also gastrin, VIP, glucagon, insulin, TSH, PRL,

Hypothalamic hormones controlling the anterior pituitary: How does CRH (corticotrophin-releasing hormone) control the anterior pituitary?

stimulates release of ACTH

Hypothalamic hormones controlling the anterior pituitary: How does Dopamine control the anterior pituitary?

inhibits release of PRL

What are two characteristics of hypothalamic hormones that act on the anterior pituitary?

1. short half life in circulation | 2. fast action

How do hormones from the hypothalamus trigger release of hormones in the anterior pituitary?

Hormones from hypothalamus bind to receptors of target cells in the anterior pituitary and trigger the release (exocytosis) of stored hormone granules.

Post-receptor intracellular signalling - trophic hormones (hormones that have other endocrine glands as their target) activate what segment of G-proteins causing what?

G(s)alpha & G(q)alpha proteins --> leads to increased Ca++ levels and exocytosis of hormone granules

Post-receptor intracellular signalling - inhibitory hormones activate what segment of G-proteins causing what?

Somatostatin and dopamine act vis G(i)alpha

Release of hormones from the hypothalamus to the anterior pituitary is _______.

pulsatile

What does the pineal gland do?

integrates information encoded by light into secretions that underline biological rhythmicity

What is the size and shape of the pineal gland?

Pine cone shaped about the size of a rice grain

What is the major hormone secreted by the pineal gland? What is this hormone synthesized by?

Melatonine synthesized by tryptophan

Pineal gland acts as link between __________ and __________.

1. external photoperiod | 2. internal milieu

The Pineal Gland controls:

Circadian rhythms

The Pineal Gland has neural connections with special receptors in the ______.

retina

What are the functions of melatonin?

1. cause other biological rhythms of the body (such as core body temperature) to hop on board with the dark-light cycle 2. induction of sleep 3. depression of reproductive activity, inhibition of ovulation and semen production in some animals 4. Seasonal fluctuations may affect the timing of breeding, migration, and hibernation in mammals 5. antioxidant 6. enhance immunity

Melatonin-receptors are found where in the body?

almost everywhere

What are some reasons people may buy and take melatonin as a pharmaceutical drug?

1. adjust jet lag | 2. sleeping aid in the elderly

What are 4 adverse side effects of melatonin?

1. daytime sleepiness 2. hypothermia 3. desensitization of melatonin receptors if doses too high 4. possible adverse events in people with seizure disorders 5. possible interaction with those taking Coumadin/warfarin

What is chronotherapy? Examples?

Timing of medication, surgery, and chemotherapy to maximize effectiveness relative to biological rhythms. Ex: Asthma early AM - Arthritis late in day - breast cancer surgery after ovulation