Hypathalamo-Adenohypophysial System 2 Flashcards
Describe the location and structure of the pituitary gland.
Pituitary is attached to the base of the brain, directly below the hypothalamus. The pituitary lies with a bone cavity known as the Sella Turcica. The gland is split into the adenohypophysis (anterior lobe) and neurohypophysis (posterior lobe)
What is the Median eminence
Area at the top of the pituitary stalk that is a mass of capillaries with blood from the superior hypophysial artery. Lots of neurones terminate on the walls of the Primary Capillary Plexus. this lies outside the blood-brain barrier so has holes e.g. fenestrated so leaky
Describe the hypothalmic control of the anterior pituitary
1) Hypothalmic nuclei are located in the hypothalamus.
2) these have neurones to the median eminence which secrete neurosecretions (hormones) into the blood
3) hormones travel in hypothalamo-adenohypophysial portal system to anterior pituitary
4) adenohypophysial cells stimulated to release hormones
Describe Adenohypophysial Cells
Somatotrophs = somatotropin (GH) Lactotrophs = Prolactin Thyrotrophs = Thyrotropin (TSH) Gonadotrophs = LH/FSH Corticotrophs = Corticotropin (ACTH) Other Cells = undefined function
Hypothalamus surrounds which ventricle?
3rd Ventricle
Describe Pituitary Development after Conception
Glandular tissue from the Buccal Cavity starts growing up while Nervous tissue from the developing hypothalamus grows down. These tissue fuse and lose contact with the buccal cavity. Anterior is derived from glandular and posterior from the neural.
Which brain areas are good from distinguishing from from back?
Front - optic chiasma
Back - Mammillary body
What are the Capillary Plexuses
Primary Capillary Plexus - in the median eminence
Secondary Capillary Plexus - in the anterior pituitary
Describe Adenohypophysial Hormones
They are protein, glycoprotein or polypeptide hormones. They are synthesised as prohormones e.g. POMC —-> ACTH + Pro-gammaMSH + betaLPH
Hypothalmic hormone Examples
- Somatotrophin Releasing Hormone controls Somatotrophin
- Dopamine controls Prolactin
- TRH controls thyrotropin
- Vasopressin controls ACTH
Describe Hormones + Target Cells
- Somatotrophin = General tissues and particularly Liver
- Prolactin = Breasts
- Thyrotrophin = Thyroid
- LH/FSH = Testes or Ovaries
- ACTH = adrenal complex
Describe the Action of Somatotrophin
1) synthesised by the adenohypophysis
2) Main target is the liver.
3) binds to receptors and causes synthesis of Insulin Like Growth Factors 1 and 2
4) these affect the body tissues and cause growth and change in metabolic rate
5) Somatotrophin can have a direct affect on the body tissues as by binding to somatotrophin receptors in cells
What are the metabolic actions of somatotrophin?
- stimulation of amino acid transport into cells
- stimulation of protein synthesis in cells
- Increased cartiligenous growth
- increased lipid metabolism and therefore, increased fatty acid
- decreased glucose utilisation and therefore higher blood glucose concentration
Describe Control of Somatotrophin
+ stimuli: growth hormone stimulating hormone, sleep, stress, oestrogens, exercise, hypoglycaemia, amino acids, ghrelin
- stimuli: Somatomedins e.g. IGF1 and GH
What are the effects of prolactin?
- Mainly breast lactogenesis
- inhibits LH release from pituitary
- increased LH receptors on ovaries/testes
- stimulates T cells
- potentially steroidogenesis?
- Renal Na+/H20 reabsorpotion
- Hypothalamus and decreased sexual behaviour
