Introduction to the Endocrine System Flashcards
What are the 3 points on the Endocrine system verses the Nervous system?
- 2 major communication systems which regulate activities of the body and maintain homeostasis
- Interact to co-ordinate activities of different organs and tissues in response to physiological needs
- Endocrine is linked to the external environment via the nervous system so can be affected by external conditions
Give 3 differences between nervous system and endocrine systems
- Nervous system is always working but endocrine often functions intermittently
- Nervous system is discrete and localised but endocrine exert diffuse control
- Nervous system has rapid control but endocrine is often prolonged control
Explain the general mechanism of the endocrine system
- Stimulus activated endocrine cell (stimulus is specific to each endocrine gland)
- Endocrine cell releases hormone into blood or intracellular space (hormones rapidly cleared from the circulation by liver
- The hormone targets the tissue and this leads to negative feedback (the incoming stimulus is reduced)
What are the 4 functions of hormones in the body?
- Development (proliferation, differentiation, organogenesis)
- Metabolism (carbohydrate, energy storage, metabolic rate, temperature)
- Reproduction (sexual maturation and behaviour, maintenance of pregnancy, lactation)
- Fluid balance (water balance, salt levels, blood volume, pressure)
List the 6 endocrine glands
- Pituitary (anterior and posterior)
- Thyroid
- Parathyroids
- Islets of langerhans
- Adrenals
- Gonads (produces male and female gametes)
What tissues of the body secrete hormones and which hormones?
Kidney = erythropoietin (production of red blood cells)
Heart = atrial natriuretic peptide (Na excretion by kidneys increases to decrease blood pressure)
Vascular endothelium = blood clotting factors
Gut cells = gastrin, secretin
Adipocytes = leptin (suppresses appetite)
Placenta = lactose, hCG
Thymus = thymosins
Explain the difference between the endocrine mechanism and the neuroendocrine one
Endocrine - hormones released from endocrine cell into blood
Neuroendocrine - hormone released from nerve cell into blood
Explain neuroendocrine secretion
Secretory Neurons have specialised nerve-endings that store hormones within vesicles.
Generation of action potentials in these neurone causes the hormones to be released into nearby capillaries.
e.g. in hypothalamus, posterior pituitary, adrenal medulla
What do the different biochemical structures of hormones determine?
- the mechanism of action at the target cell
- how the hormone is carries in the blood
- the circulating half-life
What are the 3 main groups of hormones?
PROTEINS
STERIODS
AMINES
Give the 3 types of protein hormones
- Small peptides
- ADH (9 amino acids)
- TRH (3 amino acids) - Long chain proteins
- e.g. GH and insulin - Glycoproteins
- LH
How do the peptide hormones work?
- Synthesis by DNA transcription and translation
- Mostly synthesised first as large preproxhormones, then cleaved by proteolytic enzymes to form prohormones
- Prohormones stored in cell are granules in secretory vesicles
- Release of active hormone by exocytosis stimulated by increase in cytosolic calcium
- After release, peptide hormones diffuse into ‘leaky’ capillaries
- Often circulate in blood unbound because water-soluble, so have short half-lives
- All hormones of hypothalamus, pituitary, parathyroids, GI tract, pancreas
How do steroid hormones structure and function?
Where are they produced?
How do they circulate?
How do they enter the membrane?
All structures bases on three 6 carbon rings and one 5 carbon ring.
Fat soluble lipids derived from cholesterol.
Synthesised in mitochondria and smooth ER.
Not stored in gland, so hormone release is dependent on rate of synthesis.
Able to diffuse across plasma membrane.
Circulate in blood bound to proteins e.g. albumin, therefore have long half-lives.
Produced by adrenal glands.
How do amines hormones structure and function?
Where are they produced?
How do they circulate?
How do they enter the membrane?
They are modified amino acids, derived from tyrosine.
Thyroid hormones:
- Lipid soluble, can cross cell membranes
- Circulate in blood bound to proteins, have long half-lives
- Stored in thyroid gland bound to thryoglobulin
Catecholamines:
- Water soluble, do not cross cell membranes
- Circulate unbound in blood, have short half-lifes
- Stores intracellularly in secretory granules e.g. adrenaline
Give the details on Eicosanoids
Local chemical messengers that exert a wide variety of effects in may different organs and tissues.
Autocrine or paracrine activity.
Derived from arachidonic acid (fatty acid present in plasma membrane phospholipids).
Effect of prostagladins include:
- Immune system: promotor inflammatory process
- Reproductive system: pray role in ovulation
- Digestive system: inhibit gastric secretion