Introduction To Endocrinology Flashcards
What is a paracrine hormone
Local chemical messenger distributed via simple diffusion not blood stream
Travel short distances only
Example histamine
What is neurotransmitter secretion
From nerve terminals rely on diffusion in response to electrical signal before act on target which is usually another neurone via synaptic cleft
What is hormonal secretion
Long range sec from gland into blood to the target cell need specific receptor in order to illicit a cellular response
What is neurohormone secretion
ADH syn in nerve cells and released from terminal in response to action potential with release of ADH in blood to target tissue
What are some functions of the endocrine system
Regulating the metabolism, water and electrolyte balance
Regulate nutrient supply insulin glucagon
Inducing adaptive changes to help the body cope with stressful situations adrenaline and cortisol
Promoting smooth and sequential growth and development form action of growth hormone
Controlling sexual differentiation and reproduction
Regulating RBC production
Controlling and integrating activities of both the circulatory and digestive systems
What are the complex factors of the endocrine system
A single endocrine gland may produce multiple hormones
A single hormone may be secreted form more than one gland
A single hormone has more than one type of target cell and therefore can induce more than one type of effect
Rate of secretion of some hormones can vary over time in cyclic pattern
A single target cell can be influenced by more than one type of hormone
The same chemical messenger may be either a hormone or neurotransmitter
Some organs are exclusively endocrine in function whereas some organs exhibit non endocrine functions also
How many hormones does the anterior pituitary produce
6
What cells produce somatostatin
D cells in the pancreas
Also
Neurones of hypothalamus
What does vasopressin do roughly
Increase renal rubble permeability of water
Also
Arteriolar vasoconstrictor
What is an example of the rate of secretion of some hormones can vary over time in cyclic pattern
Menstrual cycle
Give an example of an endocrine organ which has non endocrine qualities also
Testes
Testosterone etc
Sperm production
What is a tropic nourishing hormone
A hormone which has its primary function to regulate the secretion of another hormone form a different endocrine gland
What does a tropic hormone do
Stimulate and maintain their endocrine target tissue
Eg
TSH
Into blood to thyroid gland to release thyroid hormones but receptors on the gland which maintain tissue if TSH absent gland should shrink
What are some hydrophillic hormones
Hydrophillic - water loving low lipid sol
Catecholamines
Indoleamines
What are catecholamines
Derived form amino acid tyrosine
Adrenaline
Prod in adrenal medulla
What are indoleamines
Derived form amino acid tyroptohan
Melatonin
Prod by pineal gland
What are some lipophilic hormones
Lipid loving poorly sol in water
Thyroid hormone
Sex hormones
What are thyroid hormones
Amines derived from tyrosine add iodine - iodinated tyrosine derivative
What are steroid hormones
Derived from cholesterol
Sex hormones
Aldosterone
What does the solubility properties of a hormone determine
1) how hormone is processed (syn and sec) by the endocrine cell
2) how hormone is transported in blood (hydrophillic vs lipophilic)
3) how hormone exerts its effects at the target cell (hydrophilic can’t diffuse across PM where as lipophilic can)
What is the processing of hydrophilic peptide hormones (long answer)
1) large inactive precursor protein (preprohormone) are syn by ribosomes on RER
2) they then migrate to the golgi complex in transport vesicles form smooth ER
3) enzymes in the ER cleave the preprohormone to active hormones
4) the golgi complex packages the finished hormones into secretory vesicles that pinch off and store in the cytoplasm til a signal triggers for secretion
5) on stimulation the secretory vesciles fuse with PM and release contents by exocytosis
What is a common precursor for steroid hormones
Cholesterol
Are steroid hormones stored
No only the precursor cholesterol is
How are peptide hormones transported in the blood
As they are hydrophilic they are transported simpler diffused in blood
How are steroid hormones and thyroid hormone transported in the blood
Reversible bind to plasma proteins
Some plasma proteins are specific while others may carry more than 1 hormone - albumin
What lipophilic hormone is bio active
Only freely dissolved unbound
Where are the hormonal receptors for hydrophilic and lipophilic hormones
Hydrophilic - sp receptors on the outer PM
Lipophilic - bind with specific receptors located inside the target cell nucleus maybe
What are the two ways a hormone can alter the cells protein
1) surface Binding hydrophilic hormones function largely by activating 2nd messenger pathways within the cell by using a preexisting intracellular protein
2) lipophilic hormones function mainly by activating specific genes in the target cell to cause formation of new intracellular proteins enzymatic or structural
What su the effective plasma concentration dependant on
Hormones rate of secretion into the blood by the endocrine gland
For a few hormones its rate of metabolic activation or conversion
For lipophilic hormones its extent of binding to plasma proteins
It’s rate of removal form the blood by metabolic inactivation and excretion of urine
How is the effective plasma concentration usually regulated
By changes in the rate of its secretion
Do endocrine glands secrete at a constant rate
No secretion varies and is subject to control
What are some general mechanisms controlling secretion
Negative feedback
Neuroendocrine
Diurnal rhythm
What is an example of negative feedback
Control of free thyroid hormone circulating
What is an example of a neuroendocrine reflex
Increased sec of cortisol during stress
What is diurnal rhythm
Sleep/wake pattern
Cortisol greatest at morning and decreases throughout the day
What do endocrine disorders commonly arise form
Abnormal plasma concentrations of a hormone caused by inappropriate rates of secretion - too little/much
What occasionally causes an endocrine function
The sensitively of the target even if cooks Aconcagua of the hormone is normal
What is hypo secretion
Primary - abnormality in gland - factors such as disease, dietary, chemical, toxic, idiopathic ( spontaneous disease) , iatrogenic (disease form medical examination)
Secondary - endocrine gland is normal but is secreting too little as an issue with tropic enzyme
What is a treatmeant for hyposeceretion
Replacement therapy
What is hypersecrtion
Primary - defect in gland
Secondary - excessive stimulation form outside
Causes - tumour, immunological facctors( antibody mimic)
Treatment - removal of tumour or drugs to block Acton of hormone
What are the two body systems that have evolved which overlap and integrate at many levels
The nervous system rapid very precise interaction with the external environment
The endocrine system require duration rather than speed
