Endocrine System and Cell Signalling Flashcards
What are the main functions of paracrine signalling?
- plays an important role in fetal development
- regulates gastrointestinal secretions and motility
What are hormones?
chemical messengers that are carried in the blood to reach target organs
Properties of hormones
- hormones act to enhance or inhibit cellular reactions
- hormones are present at low conc in blood
- hormones are specific
4 main functions of hormones
1) regulate internal environments
2) control growth and development
3) help establish circadian rhythm
4) regulate operation of reproductive system
3 structural classes of hormones and examples of them
1) amine - catecholamine, dopamine, thyroid
2) peptides and proteins - most hormones (eg insulin)
3) steroids - testosterone, aldosterone, estrogen`
What are the major organs which metabolize hormones
kidney, liver
What is the responsiveness of a target cell to a hormone dependent on? (3)
1) concentration of hormone in blood
2) the number of receptors available
3) the influence of other hormones
What is a permissive effect between hormones
- action of one hormone requires action from another hormone
What is the synergistic effect in hormones?
hormones have an accumulative effect on one another
what is the antagonistic effect of hormones
effect of one hormone opposes the effect of another q
What are the 3 main inputs which control hormone secretion?
- plasma concentration of ions or nutrients
- neural input to endocrine cells from the autonomic system
- other hormones (some hormones stimulate the secretion of another hormone )
What is a tropic hormone?
a hormone which stimulates the secretion of another hormone
in non-stressful situations, what is the role of cortisol? (3)
- regulate [hormones] involved in metabolic homeostasis
- change responsiveness of smooth muscle cells to epinephrine and norepinephrine
- has inhibition effects on inflammation and immune responses
In stressful situations, what does cortisol do?
- inhibit inflammation, immune responses and non-essential functions
- improves cardiovascular performance
- increase ventilation
- triggers the breakdown (catabolism) of substances
what substances are broken down during stressful situations
- protein is catabolised in liver, bones, lymph and others
- amino acids are broken down -> glucose @ liver (maintain plasma [glucose])
- lipids in adipose tissue -> fatty acid + glycerol
What is the function of IGF-1 in the liver?
- stimulates glycogenesis and glucaneogenesis
- glycogen -> glucose
- increases [glucose] in liver cells
- gluc is then secreted into blood and plasma [glucose] increases
What is the function of IGF-1 in adipose tissues?
- stimulates break down of lipids (triglyceride) -> fatty acids and glycerol
- provide a different energy source to cells
What is the function of IGF-1 in the skeletal muscles?
- stimulates glycogenesis and lypolysis in muscles
- provide energy for muscle metabolism
Describe Pathway of Thryroid Hormones
hypothalamus -> TSH
TRH -> anterior pituitary (portal vessel)
APG -> TSH -> thyroid glands
thyroxine + triiodothyronine produced
thyroxine (inactive )-> triiodothyronine (active)
Function of thyroid hormones
- normal development of brain
- work with GH to stimulate growth in children
- stimulate glycogenesis and gluconeogenesis
- stimulate lipolysis and fatty acid oxidation
- increase heart rate and cardiac contractability (allow for a greater cardiac output and blood flow to tissues)
- increase metabolic rate -> increase body temperature
- high levels -> anxiety and nervousness
Describe Pathway of cortisol
hypothalamus -> corticotropin releasing hormones (CRH)
CRH -> anterior pituitary (portal vessel)
APG -> adrenocorticotropin hormones -> adrenal cortex
cortisol is produced
What is the pathway of cortisol
what is the pathway of growth hormones
what is the pathway of prolactin
