7.4 Hypothalamus and Pituitary Flashcards
Draw a diagram of the hypothalamus, pituitary stalk, sphenoid bone, optic chiasm, and pituitary
Which of the anterior/posterior pituitary come from the roof of the mouth/floor of the diencephalon? Which division is endocrine, and which is nervous?
Anterior: Roof of mouth, endocrine
Posterior: Floor of diencephalon, nervous
Describe the mechanism by which hormones are released by the posterior pituitary
- Neurons synthesised in nuclei of hypothalamus
- Stored in neuron terminals
- Released into the blood as neurohormones during stimulation
Does the posterior pituitary synthesise hormones?
No. They are synthesised in the hypothalamus
Which hormones does the posterior pituitary secrete?
- ADH/Vasopressin
- Oxytocin
What are the names of the two nuclei in the hypothalamus associated with posterior pituitary secretion?
- Supraoptic (above eyes)
- Paraventricular (next to ventricles)
What three factors stimulate ADH release?
- Inc. blood osmolarity
- Decreased blood pressure
- Increased stressors (adrenergic response)
What are the two responses produced by ADH?
- Aquaporins added to collecting ducts in nephrons
- Vascoconstriction
Describe the signalling sequence associated with the affect of ADH on the collecting ducts of kidneys
- V2 receptors
- Increased cyclic AMP (cAMP)
- Aquaporins
- HJ20 Reabsorption increases
Describe the signalling sequence associated with the affect of ADH on blood vessels
- V1 receptors
- Increased IP3 (Inositol trisphosphate) and DAG (diacylglycerol) [both cause Ca2+ release]
- Increased vascular tone
- Vasoconstriction
What type of receptor responds to ADH? Therefore, what type of hormone is ADH likely to be?
- G-coupled receptors
- Likely to be peptide or catecholamine (not A, NA or D, so must be peptide hormone)
- Could technically be steroid hormone…
Describe the signalling sequence associated with the affect of ADH on the anterior pituitary
- V3 receptors on anterior pituitary corticotrophs
- Increased inositol trisphosphate and diacylglycerol
- Increases ACTH secretion
- Increases aldosterone secretion
- Increased sodium and water resorption
Draw a feedback loop of the action of oxytocin during childbirth
Draw a feedback loop of the action of oxytocin during breastfeeding
Recall the five types of pituitary cells in the anterior pituitary
- Corticotrophs
- Gonadotrophs
- Somatotrophs
- Thrytophs
- Lactotrophs
What type of hormone do thryotrophs release? What does this act on, and what is the response?
- Thyroid stimulating hormone
- Thryoid
- Stimulates T3 and T4 secretion
What type of hormone do corticotrophs release? What does this act on, and what is the response?
- Adrenocorticotrophic hormone (ACTH)
- Adrenal cortex
- Cortisol secretion
What type of hormone do somatotrophs release? What does this act on, and what is the response?
- Growth hormone (HG)
- Bone, tissues, liver
- Essential for growth
What type of hormone do gonadotrophs release? What does this act on, and what is the response?
- Follicle stimulating and leutinizing hormone (FSH, LH)
- Ovaries and testes
- Reproduction
What type of hormone do lactotrophs release? What does this act on, and what is the response?
- Prolactin
- Mammary glands
- Milk secretion
Describe the release of hormones from the anterior pituitary
- Hypophysiotropic hormones released into capillaries of hypothalamic-hypophyseal portal system by short-axon neurons
- Hypophysiotropic hormones carried to anterior pituitary
- Control the release of hormones from anterior pituitary
What type of neurohormones are hypophysiotropic hormones?
Peptide neurohormones
Why are hypophysiotropic hormones released in very small amounts?
- Released directly to target cells
- Not diluted throughout entire blood flow
What is the abbreviation for Thyrotropin-releasing hormone? What is its effect?
- TRH
- Stimulates TSH and prolactin release
What is the abbreviation for Corticotropin-releasing hormone? What is its effect?
- CRH
- Adrenocorticotropic hormone release
What is the abbreviation for Gonadotropin-releasing hormone? What is its effect?
- GnRH
- Follicle-stimulating hormone and leutinizing hormone release
What is the abbreviation for growth hormone-releasing hormone? What is its effect?
- GHRH
- Stimulates growth hormone release
What is the abbreviation for Growth hormone inhibiting hormone (somatostatin)? What is its effect?
- GHIH
- Inhibits release of growth hormone and TSH
What is the abbreviation for prolactin releasing hormone? What is its effect?
- PRH
- Stimulates prolactin release
What is the abbreviation for Prolactin inhibiting hormone? What is its effect?
- PIH
- Inhibits prolactin release
