Lecture 4- Hypothalamus And The Pituitary Flashcards
What structure connects the hypothalamus and the pituitary gland?
Infundibulum
What is the name of the depression in the sphenoid bone where the pituitary gland sits?
Sella turcica
What is the name of the vessel network connecting the hypothalamus and the pituitary?
Hypothalamus hypophyseal portal system
What are the 2 lobes of the pituitary?
Anterior and posterior pituitary
Where does the anterior pituitary develop from, embryologically?
Ectoderm of Rathke’s pouch
Where does the posterior pituitary develop from, embryologically?
Downward extension of neural ectoderm from the floor of the diencephalon
What are the 3 parts do the anterior pituitary?
- Pars tuberalis
- Pars intermedia
- Pars distalis
What are the 2 parts of the posterior pituitary?
- Infundibular stalk
2. Pars nervosa
What are the 5 subtypes of anterior pituitary cells?
- Lactotroph
- Somatotroph
- Thyrotroph
- Gonadotroph
- Corticotroph
What causes an increase in growth hormone-releasing hormone secretion from the hypothalamus?
Low blood glucose and stress
What is the result of growth hormone-releasing hormone secretion?
Human growth hormone secretion from the anterior pituitary
What are the 4 functions of human growth hormone in the target tissues?
- Increase protein synthesis
- Increase tissue growth
- Increase fat breakdown
- Spares glucose usage
What causes the release of corticotropin-releasing hormone ?
Stress and hypoglycaemia
What is the result of corticotropin-releasing hormone?
Adrenocorticotropin hormone is released from the anterior pituitary
What is the target tissue of adrenocorticotropin hormone?
Adrenal cortex
What hormone is released from the adrenal cortex in response to adrenocorticotropin hormone?
Cortisol
What part of the adrenal cortex is cortisol released from?
Zona fasciculata
What are the 3 effects of cortisol?
- Increase fat and protein breakdown
- Increase blood and glucose levels
- Anti-inflammatory effects
What feedback effect does cortisol have?
Negative feedback to the hypothalamus to inhibit corticotropin-releasing hormone release
What hormone from the hypothalamus is released to increase thyroid hormone production?
Thyrotropin-releasing hormone
What is the effect of thyrotropin-releasing hormone on the anterior pituitary?
Causes the release of thyroid stimulating hormone
What is the effect of thyroid stimulating hormone on the thyroid gland?
Causes the release of T3 and T4 from the thyroid gland
What feedback effects do T3 and T4 have?
Negative feedback on both the hypothalamus and anterior pituitary, inhibiting thyrotropin releasing hormone and thyroid stimulating hormone release
What are the cardiovascular effects of T3?
Increased heart rate and cardiac output
What are the effects of T3 on bone?
Increased bone resorption
What are the GI effects of T3?
Increased gut motility
What effect does T3 have on lipids?
Increased lipolysis
What effect does T3 have on the sympathetic nervous system?
Increased catecholamine sensitivity
Is T3 or T4 more potent?
T3
Which thyroid hormone is converted into the other that is released?
T3 is converted into T4
How do hypothalamic hormones reach the anterior pituitary?
Through the hypothalamus-hypophyseal portal system
How do hypothalamic hormones reach the posterior pituitary?
Through the hypothalamus-hypophyseal tract
What 2 hormones are released from the posterior pituitary?
- Oxytocin
2. Anti-diuretic hormone
Which 2 regions does oxytocin stimulate myoepithelial contractions?
- Uterus
2. Mammary glands
What is the main function of anti-diuretic hormone?
Conserve body water and regulate tonicity* of body fluids
- relative concentration of solutes dissolved in solution which determine the direction and extent of diffusion
What increases the osmolality of plasma?
Water deprivation
Increased osmolality of plasma activates which hypothalamic receptors?
Osmoreceptors
Activation of hypothalamus osmoreceptors leads to what?
Release of anti-diuretic hormone
