What is an endocrine associated molecule?
A hormone that is secreted from a non-nueronal cell into the blood
What us a neuroendocrine cell?
A neuronal cell that releases hormone into the blood. An example is Growth Hormone Releasing Hormone. These hormones are made in the nerves.
What is a neurotransmitter?
A neurotransmitter is a chemical released from a neuronal cell to act locally on another cell, like acetylcholine.
What is a paracrine hormone?
A paracrine hormone is a hormone that acts on a neighbouring cell, like glucagon.
What is an autocrine hormone?
An autocrine hormone is a hormone that acts on the same cell, like insulin
Give an example of a molecule that is both a neuroendocrine hormone and a neurotransmitter.
Dopamine- it is a neuroendocrine hormone if released into the bloodstream by a neuronal cell. It is a neurotransmitter if dopamine is released into a synaptic cleft and it binds to an effect or a cell
Why do we need hormones?
Needed to enable communication between cells- they are essential
Name five roles of hormones
1) Growth and differentiation of cells 2) Regulate energy storage, metabolic rate and temperature 3) Reproduction 4) Pregnancy and Lactation 5) Osmotic level and blood pressure
Define a hormone
A hormone is a substance secreted by cells found in endocrine cells and endocrine glands. This includes neuronal and non neuronal cells.
How do hormones work ?
Hormaones released into the bloodstream and transported to target tissue in the blood. They act on target tissue through specific receptors - different tissues have different receptors
State and describe the 4 types of hormoes in the body
1) Steroid hormones - derived from Cholesterol. Pregnenolone is the precursor for all steroid hormones. 2) Derived from the amino acid (AA) - Tyrosine. Examples : Adrenaline, T3, T4, Melatonin. 3) Peptides - ADH and Oxytocin (<30 AA + 2D structure) 4) Polypeptides- larger than 3) and 3D structure. LH, FSH, Insulin, TSH
Why do polypeptide hormones have sugar residues on them?
1) Increase half life 2) Increase specificity for receptor binding
Give an example of 2 hormone from each of the four types
1) Steroid - Testosterone and Progesterone 2) Tyrosine based - Adrenaline and T3 3) Peptide based - Oxytocin and ADH 4) Polypeptide based - Insulin, FSH
Name the cell that secretes (poly)peptide hormones
(Poly)peptide secreting endocrine cell
How is a (poly)peptide endocrine cell suited for its role?
Has lots of RER to make proteins, Golgi to modify the protein
Describe the steps to make a peptide hormone
Initial peptide made much bigger via RER (Prohormone). Prohormone sent to the golgi - modified by cutting prohormone to form hormone. Hormone in vesicles in intracellular fluid and stored until depolarisation via Ca2+ influx
How is a steroid secreting cell suited for its role?
Has lots of lipid droplets containing cholesterol, several mitochondria and SER.
Describe how steroid hormones are made
Cholesterol (c27) converted to Pregnenolone (C21). This is then transferred to SER where decarbonating occurs to produce the desired hormone
Match the following numbers and letters and explain why this is the case: 1) Steroid hormone 2) Peptide hormone a) Short half life b) Long half life
1) Steroid hormone - b) Long half life - diffuses out of the cell quickly and binds to plasma poroteins 2) Peptide hormone - a) Short half life (no binding to plasma proteins - DOUBLE CHECK THIS)
Name examples of organs that secrete peptide hormones
Pancreas, Anterior pituitary and parathyroid gland
Name examples of organs that secrete steroid hormones
Adrenal cortex, testes and ovaries
How to peptide hormones work?
Bind to receptors as they cannot cross the membrane, also why they are released by exocytosis. Bind to receptor on cell surface - conformational change translated across membrane to change the inner part of the receptor conformation. This changes enzyme activity and messenger levels.
What are the different types of receptors?
1) Monomeric receptors- epidermal growth factor corsses plasma membrane 2) Multimeric receptors with membrane spanning and extraceullular subunits - Insulin binds to the alpha subunits- conformational change in beta units ---> activates tyrosine kinase ---> phosphorylates and changes activity of the cell 3) 7 transmembrane spanning receptors - beta receptors adrenergic AKA G- coupled receptors
What is the MOA of steorid hormones?
Cross the cell membrane via diffusion. The hormone binds to a receptor and the hormone receptor complex binds to a specific DNA sequence. It can interact with other transcription factors and enhance synthesis of specific proteins,
Describe negative feedback using Insulin as an example
1) An external Stimulus ( elevated plasma glucose levels) 2) Endocrine cell respons ( Beta cells increase insulin secretion) 3)Hormone in blood which are rapidly cleared by kidneys and liver (Plasma insulin conc increases) 4) Hormone binds to target cells - transports glucosefrom plasma to intracellular space 5)Response (plasma glucose back to normal)