What does the posterior pituitary release?
Vasopressin and oxytocin.
What does vasopressin do?
Increases collecting duct permeability, reducing urine volume.
What does oxytocin do?
Stimulates milk ejection from the breast and contraction of the uterus.
Where are posterior pituitary hormones synthesised?
In the hypothalamus and packaged in the cell body of the neuron.
Where are neurohormones synthesised and packaged?
In the cell body of the neuron.
What happens to neurohormones after synthesis?
- They are transported down to the posterior pituitary.
- The vesicles are stored in the posterior pituitary.
- Hormones are released into general circulation where they travel in tissues to where the receptors are.
Which neurons produce and control the posterior anterior pituitary?
Supraoptic and paraventricular nuclei.
Which neurons are concerned with the anterior pituitary?
Arcuate and other nuclei.
What is the hypothalamic-hypophyseal portal system?
The connection of the hypothalamus to the anterior pituitary.
- Neurons synthesising trophic hormones release them into capillaries of the portal system.
- Portal vessels carry the trophic hormones directly to the anterior pituitary.
- Endocrine cells release their hormones into the second set of capillaries for distribution to the rest of the body
Which hormones are in the hypothalamus?
Which hormones are in the anterior pituitary?
What is the pathway for IGF release?
Hypothalamus releases GHRH into the hypothalamic-hypophyseal portal system to the anterior pituitary, which release GH. GH travels via circulation to liver, inducing it to synthesise and release IGF.
How is thyroid hormone released?
TSH from anterior pituitary is released into circulation, it acts at the thyroid gland to release T3 and T4 thyroid hormones.
How is cortisol released?
ACTH is released from anterior pituitary and stimulates the adrenal cortex to release cortisol, which then modulates metabolic actions and stress responses.
What is the action of prolactin?
Stimulates mammary glands to increase breast growth and milk secretion.
How is the hypothalamus linked to the posterior pituitary gland?
Via a neural link
How is the hypothalamus linked to the anterior pituitary gland?
Via a vascular link - hypothalamic-hypophyseal system.
How does the final organ producing the hormone act on the structures stimulating it?
- It often feeds back onto the anterior pituitary and hypothalamus, via negative feedback.
- This allows for 2 layers of control.
What effect does somatotropin (GH) have on the liver?
Stimulates release of somatomedins, which stimulate bone and soft tissue growth, e.g. IGF-1.
Where are LH and FSH released from?
Where do LH and FSH act?
At the gonads (ovaries or testes)
What are the effects of LH stimulation of the gonads?
Sex hormone secretion (oestrogen and progesterone in females; testosterone in males).
What are the effects of FSH stimulation of the gonads?
Gamete production (ova in females; sperm in males)
What factors can influence hypothalamic regulation of the pituitary?
Neighbouring structures, such as the optic chiasm, pre-optic areas, areas for smell, etc.
What are the afferents for regulation of thyroid stimulating hormone (TSH) via TRH?
Temperature receptors in infants, perhaps others.
What is the integrating centre for regulation of thyroid stimulating hormone (TSH) via TRH?
Paraventricular nuclei and neighbouring areas
Where do ACTH and beta-lipotropin via CRH receive afferents from?
- Limbic system (emotional stimuli)
- Reticular formation (systemic stimuli)
- Hypothalamic and anterior pituitary cells sensitive to circulating blood cortisol level
- Suprachiasmatic nuclei (diurnal rhythm)
What is the integrating centre for afferents affecting ACTH and beta-lipotropin levels via CRH?
What are the afferents affecting FSH and LH via GnRH?
Hypothalamic nuclei sensitive to oestrogen, eyes, touch receptors and genitalia of reflex ovulating species.
What are the integrating centres for afferents affecting FSH and LH?
Pre-optic areas; other areas