1a. Overview + Peptide hormones Flashcards
Definition of the endocrine system
a system that integrates and controls organ function via secretion of chemicals (hormones) from cells, tissues or glands
- works with the nervous system
Definition of endocrine hormones
chemicals secreted from cells, tissues or glands that are carried in the blood to target organs, distal from the site of hormone synthesis, where they influence the activity of that target organ
Definition of paracrine hormones
act locally at the site of synthesis, do not travel distal to sites, diffuse in ECF to affect neighbouring cells e.g. histamine
Definition of autocrine hormones
act on/in the same cell that synthesises the hormone e.g. cytokines
Definition of exocrine hormones
released from exocrine glands via ducts to the external environment including the GI tract e.g. saliva, sweat, bile
How does endocrine communication work
hormones travel in the blood to their target organs/tissues
- tissues detect hormones through specific receptors for that chemical on/in the cells
No receptor = No response
Definition of neurotransmitter
a chemical released by the neurone - acts locally within the synaptic cleft
How does neural communication work
neurotransmitters released from the presynaptic neutrons travel across the synaptic cleft to the postsynaptic cell to influence its activity
Definition of neuroendocrine
the combined endocrine and nervous systems
Definition of neuroendocrine hormones
chemicals released by nerves but entered into the blood to travel to their targets
What makes the response to hormones highly specific despite them travelling all throughout the body
the presence of highly specific receptors on target cells
How can the same hormone produce different effects in the body
when it interacts with a different target cell on a different target tissue
EXAMPLE:
insulin
1. skeletal muscle/adipose tissue - increased glucose uptake
2. liver - increased glycogenesis/decreased gluconeogenesis
What physiological systems are involved in the endocrine system
reproductive, renal, GI
what main glands are involved in the endocrine system
thyroid, adrenal, pituitary, hypothalamus
name the 6 features of an endocrine hormone
- produced by a cell or group of cells
- secreted from those cells into blood
- transported via the blood to distant targets
- exert their effects at very low concentrations
- act by binding to receptors on target tissues
- have their action terminated, often via -ve feedback looks
Why do hormones work at very low concentrations
hormone receptors have very high affinity to hormone - i.e. don’t need much of the hormone to create a large response
what are the three groups of endocrine hormones
- peptide/protein hormones (from chains of amino acids)
- steroid hormones (from cholesterol)
- amine hormones (from one of 2 amino acids - tryptophan or tyrosine)
when are peptide hormones synthesised and stored
synthesised in advance of need and stored in vesicles until required
What is the initial protein produced in peptide hormones
preprohormone - large and inactive, produced by ribosomes
what are preprohormones
initial protein - contain one or more copies of the active hormone in their amino acid sequence
what happens to preprohormones in the Rough ER
cleaved into smaller inactive units called prohormones
what happens to prohormones in the golgi apparatus
packaged into vesicles along with proteolytic enzymes
what do the proteolytic enzymes in the vesicles do
breaks down the prohormone into the active hormone and other fragments
what happens to the vesicles when release is triggered (co-secretion)
the vesicles in the endocrine cells release all contents (hormones and fragments) into the plasma
