Endocrine System Flashcards
Hormones
Chemical messengers secreted into the bloodstream by a gland, which act to regulate processes in target cells and tissues
Endocrine Signalling
From one cell to another via the blood
Paracrine Signalling
From one cell to a neighbouring cell
Neurocrine Signalling
From the CNS to a cell
Autocrine Signalling
From a cell to itself
What is negative feedback and give an example
A mechanism which decreases a response to prevent a system from becoming overactive and returns it back to a set point
E.G. stress response, blood glucose levels, blood volume
What is positive feedback and give an example
Mechanism which amplifies a response by increasing levels further away from the set point
E.G. oxytocin secretion during childbirth or oestrogen secretion in menstruation cycle before ovulation
Describe the layout of the pituitary gland
Posterior and Anterior
Located at the inferior part of the hypothalamus
What does the posterior pituitary gland store and what are their functions?
Stores antidiuretic hormone (ADH)
- allows increased water reabsorption by increasing the permeability of the collecting duct
Stores oxytocin
- stimulates smooth muscle contraction
Doesn’t synthesise its own hormones
What does the anterior pituitary gland produce?
Receives neurohormone signals from the hypothalamus
Produces these hormones:
- follicle stimulating hormone (FSH) and luteinising hormone (LH)
- thyroid stimulating hormone (TSH)
- growth hormone (GH)
- prolactin
-adrenocorticotropic hormone (ACTH)
What are FSH and LH released by and what do they act on?
Released by gonadotropes
Act on testes and ovaries to stimulate sex steroid production
What is TSH released by and what does it stimulate?
Released by thyrotropes
Stimulates thyroid hormone production to control your metabolism
What is ACTH released by and what does it stimulate?
Released by corticotropes
Stimulates cortisol release
What is GH released by and what does it stimulate?
Released by soma tropes
Stimulates growth
What is prolactin released by and what does it stimulate?
Released by lactotropes
Stimulates milk production
Where are the adrenal glands located, what are they controlled by and what are they divided into?
Located above the kidneys
Controlled by the sympathetic nervous system
Controlled by the ACTH
Divided into the medulla and the cortex
What is the adrenal cortex split into and what do they produce?
Split into:
Zona glomerulosa
- produces mineralocorticoids which regulates blood volume
Zona fasciculata
- produces glucocorticoids which allows the stress response
Zona reticularis
- produces androgens for sexual development and glucocorticoids
What does the adrenal medulla produce?
Produces adrenaline and noradrenaline catecholamines for the stress response
What are steroid hormones synthesised by and describe their solubility in relation to how they’re released
Synthesised by cholesterol
Instantly released by diffusion due to their lipid solubility
Hydrophobic
Describe the reception and response of steroid hormones
Reception:
- diffuse across the cell membrane
- bind to intracellular receptors
- causes a conformational change which exposes the DNA-binding site
Response:
- bind to DNA
- alters transcription of specific genes into mRNA, which is translated into protein & alters cellular activity
How are non-steroid hormones produced, stored and synthesised?
Produced from polypeptides
Stored in secretory vesicles
Hydrophilic and lipophobic
Synthesised via transcription and translation
Describe the reception, transduction and response of non-steroid hormones
Reception:
- can’t diffuse across the cell membrane so binds to cell surface receptors
Transduction:
- G-protein coupled receptors
–> binds to effector protein & causes release of second messengers
- Tyrosine kinase receptors
–> autophosphorylate & activate relay proteins
Response:
- protein phosphorylation enzyme cascade to activate or inhibit proteins & alter cellular activity
