Hypothalamus and Pituitary Flashcards
Give 3 examples of biological states which are controlled by the hypothalamus.
Any 3 of:
- Temperature
- Appetite
- Thirst
- Fatigue
- Behaviour
- Circadian rythm
- Blood pressure
- etc.
What inputs affect hypothalamic signalling? Give a few examples.
Light, smell, stress, immune system, neural inputs, endocrine inputs, etc.
What are the 2 types of hypothalamic output? What differentiates these?
Direct innervation: fast, often for fight/flight response
Neurosecretion: slow, releases hormones which can have varying effect
What is the function of hypophysiotropic hormone?
Regulates the release of anterior pituitary hormones.
What is the function of thyrotropin-releasing hormone (TRH)?
Stimulates the release of thyroid stimulating hormone (TSH) from the anterior pituitary.
What is the function of gonadotropin-releasing hormone (GnRH)?
Regulates luteinizing hormone and follicular stimulating hormone.
What is the function of somatostatin?
A general inhibitor. Acts on growth hormone, thyroid stimulating hormone, insulin, glucagon, etc.
What is the function of growth hormone-releasing hormone (GHRH)?
Stimulates the release of growth hormone (tropic), and helps growth of somatotrophs (trophic).
What is the function of prolactin-inhibiting hormone (PIH)? What is another name for this?
Also called dopamine, it inhibits the release of prolactin.
What is the function of corticotropin-releasing hormone (CRH)? What other hormones regulate it?
Regulates adrenocortical function, ACTH release, appetite, and sympathetic NS. Vasopressin positively regulates CRH while oxytocin acts as a negative regulator.
What category of cell types secrete growth hormone (GH)? How are they regulated?
Somatotrophs. Inhibited by somatostatin but also have autocrine signalling for negative feedback.
What category of cell types secrete prolactin (PRL)?
Lactotrophs.
What category of cell types secrete thyroid-stimulating hormone (TSH)?
Thyrotrophs.
What category of cell types secrete adrenocorticotropic hormone (ACTH)?
Corticotrophs.
What category of cell types release luteinizing hormone (LH) and follicular stimulating hormone (FSH)?
Gonadotrophs.
What kind of receptor does gonadotropin-releasing hormone (GnRH) bind to?
GPCRs.
What type of GPCR Galpha subtype activates phospholipase C?
Galpha-q.
How is the hypothalamic-pituitary-gonadal axis regulated?
The hormone products of the ovaries and the testis act on the hypothalamus and pituitary in a negative feedback loop.
Why must gonadotropin-releasing hormone be secreted in pulses?
Otherwise it would lead to the desensitization of luteinizing hormone (LH) and follicular stimulating hormone (FSH).
What kind of receptor does corticotropin-releasing hormone (CRH) bind to?
GPCRs.
How is the hypothalamus-pituitary-adrenal axis regulated? (Hint: think “short” and “long” feedback)
By negative feedback, either ACTH secreted by the pituitary inhibiting CRH (short) or cortisol secreted by the adrenal gland inhibiting the pituitary (long).
How can the negative feedback of cortisol on the release of ACTH from the pituitary have both fast and slow effects?
Fast: non-genomic, activates signalling pathways
Slow: genomic, alters transcription
At what point during the day do we experience a peak in cortisol levels?
Immediately prior to waking. Cortisol levels then decline as the day progresses.
What factors can influence the timing of the hypothalamus-pituitary-adrenal axis?
Stresses (physical, emotional, chemical) as well as the circadian rhythm.
What effect does increased prolactin (PRL) have on the prolactin axis?
Inhibits gonadotropin-releasing hormone, therefore inhibiting ovulation and spermatogenesis (don’t need to get prego if already prego). Also stimulates milk production and breast development.
How can prolactin (PRL) production in the anterior pituitary be upregulated?
Breastfeeding causes negative feedback on prolactin inhibitory hormone (aka dopamine) secreted by the hypothalamus. Inhibiting the inhibitor = upregulation!
