Hormones - General introduction Flashcards
How are neural and endocrine communication different?
Neural communication is usually long distance and has specific targets which it reaches very quickly. Action is fast but stops acting just as fast. Neural communication is often specific to one organ only.
Endocrine communication also long distance, however it flows through the bloodstream and is composed of specific signalling molecules which bind to specific receptors on target cells. Action is more widespread and can act on several organs. Adaptation is slow and continues for a longer time.
How is the nervous system divided?
CNS -> brain + spinal cord
PNS -> sensory and motor divisions.
Sensory division is further divided into visceral and somatic sensory divisions
Motor division is further divided into visceral an somatic motor divisions.
Visceral motor division is even further subdivided into sympathetic and parasympathetic divisions
What are some molecules that act as both neurotransmitters and hormones?
Noradrenaline
Dopamine
ADH
What is neuroendocrine signalling?
Combined neural and endocrine signalling where a neuron secretes hormones into the blood.
Give an example of neuroendocrine signalling:
Adrenal medulla producing adrenaline into the blood
Posterior pituitary producing oxytocin into the blood
What makes studying hormones challenging? How is that problem accounted for?
They are produced in very small amounts so they are difficult to purify in appreciable quantity.
ELISA is a more sensitive way to measure hormones using radio-labelled antibodies
What is ELISA?
Enzyme-Linked Immunosorbent Assay.
Purified hormone injected into an animal
Animal makes antibody to hormone
Secondary antibody is purified and labelled with an enzyme
Substrate is added which produces a colored product
Quantity can be measured from colour
How is indirect ELISA conducted?
Sample coats the well
Sample (hormone) is incubated with primary antibody that binds to it
Secondary antibody binds to primary antibody - enzyme complex secondary antibodies contain HRPO which can be degraded into colour
Substrate added converts HRPO to detectable product
Hormone is then quantified
What are the broad classes of hormones?
Protein/peptide
Tyrosine-derived
Steroid
What are the characteristics of protein/peptide hormones?
They are a large group of hormones
Stored in excretory granules/vesicles and released via exocytosis
They are hydrophilic and bind to cell-surface receptors
They are rapid acting and short-lived
What are the features of steroid hormones?
Derived from cholesterol.
Lipophilic: Require transport proteins
Bind intracellular receptors
Stored in granules & present in free form in cytoplasm
What are some examples of steroid hormones?
Include: cortisol, aldosterone,
testosterone and
progesterone
Where are steroid hormones derived from?
Cholesterol
What are some examples of tyrosine-derived hormones?
Adrenaline and NA
Thyroid hormones - thyroxine and dopamine
Are tyrosine-derived hormones lipophilic or hydrophilic?
They can be either:
Catecholamines and dopamine are water soluble whereas thyroid hormones are lipophilic and require carrier proteins.
