Physiology 1 - The Pituitary Flashcards Preview

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Flashcards in Physiology 1 - The Pituitary Deck (19):

Describe the anatomy of the pituitary gland?

Split into 2 parts:
Anterior Pituitary (Adenohypophysis) which is a true endocrine gland of epithelial origin

Posterior Pituitary (Neurohypophysis) which is derived from neural tissue


How is the pituitary gland related to the hypothalamus?

Its physically connected by:
1) Pituitary Stalk (of which the post. pituitary is an extension)
2) Hypothalamo-Hypophyseal portal system to the ant pituitary

The hypothalamus controls what hormones are released by the pituitary gland


What is another word for the pituitary stalk?

The Infandibulum


Whats the function of the hypothalamo-hypophyseal portal system?

Carried trophic hormones from the hypothalamus to the anterior pituitary


How do trophic hormones from the hypothalamus enter the hypothalamo-hypophyseal portal system?

Neurons of the hypothalamus release them at the median eminence into the bloodstream.


What is the function of the infandibulum?

It carries neurohormones from the hypothalamus to the posterior pituitary where they are stored before released into the general blood supply


What is a trophic hormone?

One which modulates the release of other hormones from its target tissue


What is a neurohormone?

Hormones produced by nerve axons and released into the blood


What hormones are released from the hypothalamus?

Trophic hormones that travel to the anterior pituitary

Non-trophic hormones released into the blood via the post. Pituitary


Specifically what trophic hormones are released from the hypothalamus?

- Thyrotrophin releasing hormone (TRH)
- Corticotrophin " (CRH)
- Growth Hormone " (GHRH)
- Gonadotrophin " (GnRH)
- Prolactin " (PRH)

- Growth Hormone Inhibiting Hormone (GHIH) aka somatostatin
- Prolactin Inhibiting Hormone (PIH) aka Dopamine


What physical class of hormone are the hypothalamic trophic hormones?

Entirely Peptide hormones
Except for dopamine (Prolactin Inhibiting Hormone) which is a catecholaamine


What hormones are released from the Adenohypophysis?

- Thyrotrophin (Thyroid stimulating - TSH)
- Corticotrophin (Adrenocorticotrophic - ACTH)
- Gonadotrophins (Follicle Stimulatin - FSH & Luteinising - LH)
- Growth Hormone (GH)
- Prolactin


What class of hormones are the Adenohypophysis hormones?

They're all peptides
5 Are trophic, only prolactin is non-trophic


So far the pituitary hormones are classed as:

- Excretes 5 releasing trophic hormones
- 2 Inhibiting Trophic hormones
- Some Non-trophic hormones

Ant. Pituitary:
- 5 Trophic hormones
- 1 (Prolactin) non-trophic hormone

All so far are peptides except for Dopamine (Prolactin inhibiting hormone) released from the hypothalamus


What -ve feedback mechanisms are involved in control of pituitary hormones?

Short Feedback Loop:
Trophic hormones released from the pituitary inhibit the hypothalamus

Long Feedback Loop:
Non-trophic hormones released from the final endocrine gland inhibit the ant pituitary

These mechanisms tightly control appropriate plasma levels of hormones


So far we know the posterior pituitary releases Neurohormones produced in the hypothalamus, how are they made and released?

Peptide Neurohormones produced in the magnocellular neurons of the hypothalamus.

They travel down axons in the infandibulum and are stored in the post pituitary.

Activity in these neurons releases them into the blood


What peptide neurohormones are released from the post. Pituitary?


Vasopressin (ADH)


Describe the mechanisms behind vasopressin?

Vasopressin or ADH regulates water balance.

Its released in response to low plasma volume, low BP and high plasma osmolarity.

It increases water reabsorption at the kidney collecting duct & vasoconstricts to raise BP


Describe the mechanisms behind Oxytocin?

Oxytocin triggers milk ejection & uterine contraction in response to suckling & labour respectively

It causes milk duct and uterine smooth muscle to contract