The endocrine system (2) Flashcards
Week 6 (23 cards)
What is the Hypothalamus connected to?
The pituitary gland via stalk called infundibulum
What are the two major lobes of the pituitary gland ?
Posterior pituitary and Anterior pituitary
What is and what does the posterior pituitary/lobe do?
1- Composed of neutral tissue that secretes neurohormones
2- Composed of neutral tissue derived from a downgrowth of the brain, along with infundibulum makes up the neurohypophysis
What is the Anterior pituitary and what does it do?
- Consists of glandular tissue
-Adenohypopysis
Two major job roles of the Posterior lobe
1- Maintains neural connection to hypothalamus via hypothalamic-hypophyseal tract
2- Secretes two neurohormones (oxytocin and ADH)
What is the hypothalamic-hypophyseal tract and where is it?
1-Neurons in paraventrical and supraoptic nuclei in hypothalamus
2- Run through the infundibulum.
The steps taken (including action potentials) for oxytocin or ADH to be released into the blood. (4)
1- Hypothalamic neurons synthesise oxytocin or antidiuretic hormone (ADH)
2- Oxytocin and ADH are transported down the axons of the hypothalamic-hypophyseal tract of the posterior pituitary
3- Oxytocin and ADH are stored in axon terminals in the posterior pituitary
4- When associated hyppothalamic neurons fire, action potentials arriving at the axon terminals cause oxytocin or ADH to be released into the blood.
What is ADH’s role and how does it do this?
1-ADH’s role is to regulate water balance by increasing water reabsorption in the kidneys.
2- (a) When the body detects a low blood volume or high blood concentration, the hypothalamus signals the posterior pituitary gland to release ADH.
(b) ADH then travels to the kidneys, where it increases the permeability of the collecting duct to water by inserting aquaporins into the cell membrane.
What can be a cause of Diabetes insipidus, what must you do when you have it?
1-ADH deficiency due to damage to hypothalamus or posterior pituitary
2-Increased alcohol consumption which will interfere with the normal functioning of the pituitary gland.
-Stay well hydrated
How can alcohol interfere with the pituitary gland and the release of ADH?
Ethanol blocks voltage-gated calcium channels.
What does the Anterior pituitary consist of?
Glandular tissue derivved from an outpocketing of oral mucosa
What is the Anterior pituitary connected to?
The hypothalamus via hypophyseal portal system consisting of:
1- Primary capillary plexus
2- Hypophyseal portal veins
3- Secondary capillary plexus
1- When appropriately stimulated , hypothalamic neurons secrete releasing or inhibiting hormones into the primary capillary plexus
2- Hypothalamic hormones travel through portal veins to the anterior pituitary where they simulate or inhibit release of hormones made in the anterior pituitary.
3- In response to releasing hormones, the anterior pituitary secretes hormones into the secondary capillary plexus. This in turn empties into the general circulation. e.g growth hormone (GH), Thyroid-stimulating hormone (TSH), Follicle stimulating hormone (FSH)
What is a portal system and what is included in the hypophyseal system?
1- Two capillary plexus (beds) connected by veins.
2- Primary capillary plexus
-Hypophyseal portal veins
-Secondary capillary plexus.
What are the six anterior pituitary hormones?
1- Growth hormone (GH)
2.Thyroid-stimulating hormone (TSH - tropic)
3- Adrenocorticotropic hormone (ACTH - tropic)
4- Follicle-stimulating hormone (FSH - tropic)
5- Luteinizing hormone (LH- tropic)
6- Prolactin (PRL)
What type of hormones are the anterior pituitary hormones??
Peptide hormones
What do all hormones but growth hormone (tyrosine kinase receptor) activate?
Target cells via cAMP second-messenger system
What do tropic hormones (tropins) do?
Regulate the secretion of other hormones.
What is hypersecretion of Growth hormone caused by?
A tumor in the anterior pituitary
What can hypersecretion of Gh cause in children and in adults?
1- In children = Gigntism, can reach heights of 8 feet (2.4m)
2- In adults = Acromegaly, overgrowth of hands, feet and face
What does hyposecretion of GH casuse in children?
Pituitary dwarfism - may reachh heights of only 4 feet (1,2 m)
What is FSH and LH secreted by?
Gonadotroppic cells of the anterior pituitary
