Unit 2: Hormones (Lectures 1-2) Flashcards
What is a hormone ?
A substance secreted directly into the blood by discrete specialised cells in response to a specific stimulus.
What are the functions of the endocrine glands (2)?
- The production of hormones
- Secretion of hormones into the bloodstream
What are the 4 classes of hormone action ?
- Endocrine
- Paracrine
- Autocrine
- Neuroendocrine
What is an endocrine hormone action ?
Secreted directly into the bloodstream and transported to a distant target tissue to exert its actions
What is the paracrine hormone action ?
Released by a gland cell and diffuses through the extracellular space to its target cell with the same gland
What is the autocrine hormone action ?
When a hormone is released by cell and that exerts its actions on the same cell
What is the neuroendocrine hormone action ?
When a neuronal hormone is released into a synaptic cleft adjacent to where the neurone contacts the target cell
What are the 4 classes of hormones ?
- Protein and peptide hormones
- Steroid hormones
- Hormones derived from tyrosine
- Eicosanoids
What is the main category of glycoprotein peptide hormones ?
Gonadotrophins such as LH and FSH
Where are steroid hormones synthesised ?
Mainly in the adrenal cortex, testis, ovaries and placenta
What is the structure of a steroid hormone ?
3 six membered rings and 1 five membered ring
Are steroids hormones hydrophobic or hydrophilic and what does this mean for its transport ?
They are hydrophobic. This means they are transported in the blood stream to carrier proteins and can pass through the cell membrane
What is the structure of a catecholamine and give 3 examples
Structure = benzene ring with 2 adjacent hydroxyl groups and amine side chain
Examples = Adrenaline, noradrenaline and dopamine
How do catecholamines work ?
They are hydrophilic so bind to GPCRs on the plasma membrane
How do thyroid hormones work ?
They are hydrophobic and enter cell via transporter proteins and bind to nuclear receptors
What the the 2 classes of eicosanoid messengers ?
- Prostaglandins
- Leukotrienes
How do eicosanoids work ?
They bind to GPCRs on target cells
How are hydrophobic hormones generally transported ?
In the blood bound to carrier proteins
What 2 types of hormone does the hypothalamus release ?
- Releasing
- Inhibitory
What are the 5 main hormones found in the anterior pituitary ?
- Somatatroph
- Lactotroph
- Corticotroph
- Thyrotroph
- Gonadotroph
What vessels connect the hypothalamus to the anterior pituitary ?
Hypothalamic-hypophysical portal vessels
Where are hormones produced by neurones in the hypothalamus secreted ?
In the median eminence
What is the function of a hormone ?
To regulate the activity of its target cells in a specific manner
Where does the anterior pituitary receive feedback signals from ?
The target glands
