Neuroendocrinology revision Flashcards
By what 3 mechanisms does the hypothalamus maintain homeostasis?
Behavioural control (via communication with the limbic system to alter behaviour) Neuronal control (triggers parasympathetic or sympathetic response) Hormonal control (by stimulating release of hormones from anterior pituitary)
What are the 6 key functions of the hypothalamus?
BP + Electrolyte balance Body temperature Energy metabolism Reproduction and lactation Stress response Growth
What are the 4 main nuclei of the hypothalamus and their functions?
Preoptic = thermoregulation Anterior = stress, energy balance, osmoregulation/ BP and maternal control (oxytocin) Dorsomedial = reproduction, growth, lactation and diurnal rhythm Posterior = sleep-wake cycle (via mammillary body)
How does the hypothalamus communicate with the pituitary gland?
Via pituitary stalk and with the anterior pituitary via the hypophysial portal system (hormones released into blood supply from hypothalamus to stimulate release of hormones from anterior pituitary)
Where are the anterior and posterior pituitary derived from?
Anterior = pharyngeal epithelium Posterior = neuronal tissue
[Explains why anterior and posterior are so different and stimulated in different ways e.g. anterior by hormones and posterior neuronally]
What is the Hypothalamus - Pituitary - Adrenal Axis?
- Release of Corticotropin Releasing Hormone from Hypothalamus
- Stimulates release of Adrenocorticotropic Hormone from Anterior Pituitary
- Stimulates release of Cortisol from Adrenal Glands
[Cortisol levels act as negative feedback to inhibit further release of CRH and ACTH)
What is the Hypothalamus - Pituitary - Thyroid Axis?
- Release of Thyrotropin Releasing Hormone from Hypothalamus
- Stimulates release of Thyroid Stimulating Hormone from Anterior Pituitary
- Stimulates release of T3 and T4 from Thyroid Gland
[T3/T4 act as negative feedback to inhibit further release of TRH and TSH]
What is the Hypothalamus - Pituitary - Gonadal Axis?
- Release of Gonadotropin Releasing Hormone from Hypothalamus
- Stimulates release of FSH + LH from Anterior Pituitary
- Stimulates release of Oestrogen from Ovaries (or Testosterone from Testes)
[Negative feedback to inhibit further GRH/ FSH/ LH release]
How is Prolactin release regulated?
Short loop feedback - no releasing factor, instead regulates own secretion (keeps levels low)
[Nb. Dopamine has an inhibitory effect on Prolactin release so SE of dopamine antagonists can be increased Prolactin levels resulting in breast growth, lactation etc.]
How does the regulation of Prolactin release change in pregnancy?
The placenta produces lactogens which are a stimulating source outside of the normal short loop feedback (increases prolactin production)
What are the 6 key hormones released from the anterior pituitary?
Follicle Stimulating Hormone Leutinising Hormone Growth Hormone Thyroid Stimulating Hormone Adrenocorticotropic Hormone Prolactin
What are the functions of the posterior pituitary gland?
- Release of Oxytocin (increases uterine contractions)
2. Release of ADH (increases water reabsorption in kidneys)
Which neurones allow communication between the hypothalamus and the anterior and posterior pituitary gland?
Anterior = parvocellular (via hypophysial system) Posterior = magnocellular (extend from the hypothalamus directly to the posterior pituitary)
What region in the hypothalamus is responsible for controlling circadian rhythms?
Suprachiasmatic nucleus
How does feedback from baroreceptors in the heart/ aorta increase blood pressure?
- Low pressure detected by baroreceptors in the atria of the heart (e.g. due to major reduction in blood volume)
- Information relayed via CN IX and X to the Nucleus Tractus Solitarius (in brainstem)
- Brainstem sends stimulating signal to hypothalamus
- Signal sent to posterior pituitary which causes increase in Vasopressin (ADH)
- Vasopressin acts on V1 receptors to vasoconstrict blood vessels (and also increases water reabsorption in kidneys)
