The Pituitary Gland Flashcards
(24 cards)
Is the pituitary neural tissue or glandular? The hypothalamus?
- The (ANTERIOR) pituitary is a true endocrine gland of epithelial origin
- The hypothalamus is part of the brain, therefore a neuroendocrine gland composed of neural tissue
What functions as the integration centre for endocrine systems?
The hypothalamus
What connects the hypothalamus and the pituitary?
- The infundibulum
It’s a stalk like structure
Describe the relationship between the neurones of the hypothalamus and the pituitary gland?
- Neurones have their cell bodies in the hypothalamus and their axons project down into the posterior pituitary
- Neurohormones released into blood by hypothalamic axons in the posterior pituitary
In which bone is the pituitary gland located?
- Sphenoid
How are the anterior pituitary and hypothalamus “connected”?
Via neurohormones
Another name for the anterior pituitary?
Another name for the posterior?
- Adenohypophysis
- Neurohypophysis
What lies between the anterior and posterior pituitary? Function?
- Pars intermedia (active in foetal stages)
- Secretes melanocyte stimulating hormone, controls the production of melanin
What is a tropic hormone?
- Tropic: A hormone that governs the release of another hormone
(have other endocrine glands as their target)
What are magnocellular neurones? What do they secrete?
- Neuroendocrine cells of the hypothalamus that secrete via the posterior pituitary
- Vasopressin (ADH) & Oxytocin
Functions of vasopressin and oxytocin? What type of hormones are they?
- Vasopressin (ADH): anti-diuretic hormone, maintains water balance
- Oxytocin: stimulates uterine contraction at parturition, and aides expression of milk in lactating breasts (also has role in social bonding)
- Peptide hormones (vesicles & receptors)
Examples of some tropic hypothalamic hormones that act on the anterior pituitary to stimulate hormone release?
Releasing:
- Thyrotropin releasing hormone (TRH)
- Corticotropin releasing hormone (CRH)
- Growth hormone releasing hormone (GHRH)
- Gonadotropin releasing hormone (GnRH)
- Prolactin releasing hormone
All peptide hormones
Examples of some tropic hypothalamic hormones that act on the anterior pituitary to INHIBIT hormone release?
- Growth hormone inhibiting hormone (GHIH) aka somatostatin (peptide)
- Prolactin inhibiting hormone aka Dopamine (catecholamine)
How do tropic hormones from the hypothalamus reach the anterior pituitary?
- Via the hypothalamo-hypophyseal portal system (capillaries)
- Hormones released at the “median eminence”
What controls the production of hormones in the anterior pituitary?
- Hypothalamic tropic hormones
How many hormones are released by the anterior pituitary? What types of hormones are they?
- 6 Hormones released from the ant. pituitary
- ALL Peptide hormones
- 5/6 are tropic hormones
Name the hormones of the anterior pituitary gland
- Thyroid stimulating hormone (TSH, aka thyrotropin)
- Adrenocorticotrophic hormone (ACTH, aka corticotropin)
- Follicle stimulating hormone (FSH)
- Luteinising hormone (LH)
- Growth Hormone (GH)
- Prolactin
1-5 ALL tropic
Which “integration centres” are involved in the feedback control of anterior pituitary hormones?
What is long / short loop feedback?
- Hypothalamus, anterior pituitary itself and the target endocrine cell
- Long-loop Feedback: feedback from endocrine target
- Short-loop Feedback: Feedback from anterior pituitary to the hypothalamus
How are endocrine disorders classified?
- Hypersecretion
- Hyposecretion
- 1 (primary) disorders
- 2 (secondary) disorders
- 3 (tertiary disorders)
- Hyporesponsiveness
- Hyperresponsiveness
What are primary, secondary and tertiary endocrine disorders?
- 1 (primary) disorders: defect in the cells that secrete the hormone
- 2 (secondary) disorders: too little or too much tropic hormone fro anterior pituitary
- 3 (tertiary disorders): hypothalamic defects
Causes of hyporesponsiveness?
- Alterations in receptor
- Disordered post receptor events
- Failure of metabolic activation of hormone
- Antagonistic effects
How can hypo/hyper-responsiveness originate?
- Prolonged exposure to low hormone concentration can cause up-regulation of receptor number (hyperresp)
- Prolonged exposure to high hormone concentration can cause down-regulation of receptor number (hypores)
What are permissive effects? Example?
- When the presence of one hormone enhances the effect of another
- Eg. Epinephrine alone causes modest lipolysis in adipose tissue, but in the presence of thyroid hormone there is lots of lipolysis. TH is permissive to epinephrine
What are antagonistic effects? Example?
- Presence of one hormone reduces the effect of another
- Eg. Growth hormone inhibits glucose uptake in response to insulin by decreasing receptor recruitment on cell muscle and adipose tissue cell surfaces
