Intro to Endocrine system 1 Flashcards
What are glands?
They are epithelial tissue derivatives specialised for secreting.
What is epithelial tissue?
It is a functional grouping of cells specialised in the exchange of material between the cell and it’s environment, lines and covers various body surfaces and cavities and forms secretory glands.
What is secretion?
It is the release from a cell in response to appropriate stimulation of specific products that have been produced by the cell.
What is communication critical for in cells?
Communication is critical for cell survival and function
What are the 2 major communication systems?
Nervous system and endocrine system
What are the 4 types of chemical messengers?
Autocrine/paracrine, neurotransmitter, neurohormones and hormones
What are autocrine and paracrine chemical messengers?
They are local chemical messengers.
They exert effect on neighbouring cells - paracrine
or on the same cell - autocrine
What are neurotransmitters?
They are short range chemical messengers.
They diffuse across synapses (narrow spaces) to act on adjoining target cells such as other neurons, a muscle or a gland
What are neurohormones?
They are hormones released into blood by neurosecretory neurons.
They are distributed through the blood to distant target cells.
What are hormones?
They are long range hormones.
They are secreted into the blood by endocrine glands in response to appropriate signal and they act on distant target cells.
Where does autocrine act?
Autocrine can act on itself
Where does paracrine act?
Paracrine can act on another cell that is close by
Where are neurohormones released by and into and what do they act similar to?
Neurohormones are released from synaptic vesicles by neurons and they are released into the blood where they act in a similar way to hormones.
What are hormones? 3 points
They are messengers of endocrine system.
They’re released from endocrine glands into the blood where they are transported.
The target cell expresses specific receptors .
Structure and chemical messenger of nervous system:
Wired system of neurons
Neurotransmitter
What is the target site for the nervous system and the distance of action?
Very close and it acts across the synaptic cleft
Major function of the nervous system:
Fast precise responses
How long is the nervous system response and duration of action?
Milliseconds
What is the structure and chemical messenger of endocrine system?
Endocrine system is a wireless system of glands and hormones are the chemical messenger
What is the target site and the distance of action of the endocrine system?
Far away and it is carried by the blood
What is the speed of response and duration of action of the endocrine system?
Minutes to hours for response
Minutes to days for duration of action
What is the major function of the endocrine system?
For long duration responses
What are the 2 main differences between hormones and neurotransmitters?
- Neural messages can only travel along existing nerve tracts; hormonal messages can travel in the circulatory system; thus any cell receiving blood is potentially able to receive a message.
- Neural messages are digital, all-or-none events that have rapid onset and offset; neural signals can take place in milliseconds; plus, electrical signal can travel along myelinated axons at speeds up to 100 meters per sec
WhereasnHormonal messages are analog, graded events that can take seconds, minutes or hours to occur.
How does a hormone exert its influence?
Only cells with receptors for that hormone can be influenced and they are called target cells
The interaction of a hormone with its receptor leads to a genomic response whereby the hormone activates genes that regulate protein synthesis (e.g., up-regulation: synthesis of a receptor for that hormone).
What are the 4 types of hormones?
Peptide, catecholamine, thyroid and steroids
Do hormones change the function of a cell?
Hormones rarely change the function of a cell, rather they alter the rate of normal cellular function, thus hormones affect cell morphology and size. Although they can affect behaviour, behaviour can also influence hormonal levels and effects.
What are the most abundant type of hormones?
Peptide hormones
What are the hydrophilic hormones?
Peptide and catecholamines
Lipophobic they are water soluble
What are the hydrophobic hormones?
Thyroid and steroid hormones
Lipophilic, they are water insoluble
Hormones - Peptide:
1. Structure?
2. Solubility?
3. Receptors located?
4. Where are they made?
5. Stored in?
6. How are they secreted?
7. How are they transported in the blood?
8. Hormone locations?
- amino acids
- Hydrophilic, Lipophobic
- On the cell surface
- in ER
- Granules
- Exocytosis of granules
- Free Hormone
- Hypothalamic, pituitary, pineal, pancreas, parathyroid, GIT, kidney, liver heart
Hormones - Catecholamine:
1. Structure?
2. Solubility?
3. Receptors located?
4. Where are they made?
5. Stored in?
6. How are they secreted?
7. How are they transported in the blood?
8. Hormone locations?
- Tyrosine derivative
- Hydrophilic, lipophobic
- On cell surface
- In cytosol
- Granules
- Exocytosis of granules
- Plasma bound
- Adrenal medulla
Hormones - Thyroid:
1. Structure?
2. Solubility?
3. Receptors located?
4. Where are they made?
5. Stored in?
6. How are they secreted?
7. How are they transported in the blood?
8. Hormone locations?
- Iodinated tyrosine derivative
- Lipohilic, hydrophobic
- Inside cell
- Organelles
- Colloid
- Endocytosis of colloid
- Plasma bound
- Thyroid follicular
Hormones - Steroids:
1. Structure?
2. Solubility?
3. Receptors located?
4. Where are they made?
5. Stored in?
6. How are they secreted?
7. How are they transported in the blood?
8. Hormone locations?
- Cholesterol derivative
- Lipophilic hydrophobic
- Inside cell
- Intracell
- Lipid droplets
- Diffusion
- Plasma bound
- Adrenal cortex gonads, Vitamin D
What are steroid hormones derived from?
Cholesterol
Is the steroid hormone receptor intracellular or extracellular?
Receptor is intracellular
Steroid diffuses through?
Cell membrane
What type of molecules are steroid hormones?
They are small lipid-soluble molecules
GIVE 8 steroid hormones derived from cholesterol:
Progesterone, aldosterone, cortisol, testosterone, estrone, estradiol, estriol and Dehyroepiandrosterone (adrenal cortex hormone)
What receptors bind peptides and catecholamines at cell membrane (extracellularly)?
Surface receptors
What receptors bind thyroid and steroid hormones inside the cell?
Nuclear receptors
All cells maybe exposed to hormones via circulation but only cells with receptors
for hormone can respond, receptor activation alters what?
Channel function and 2nd messenger systems
Steroid receptors bind steroid hormones, what does this make and what does this alter?
A hormone-receptor complex that becomes a transcription factor (alters gene transcription)
Each steroid receptor binds a unique DNA sequence (response element within
an enhancer region), what does this alter?
This alters the rate of transcription
What are the 3 surface receptor structure domains?
Ligand binding domain - LBD
7 transmembrane domains - TMDs
G-protein coupled
Mechanism of surface receptor domains?
Peptide hormone binds to receptors on the surface of the cell which activates G-protein
and induces intracellular signals
Neuropeptide examples: 6
Prolactin, Adrenocorticotrophic hormone (ACTH), Antidiuretic hormone (vasopressin),
Oxytocin, Insulin, Somatostatin
Nuclear receptor domain structures? 3
- Hormone/Ligand binding domain (LBD)
- DNA binding domain binds steroid response element (SRE).
- Nuclear Localization Signal (NLS) covered by heat shock proteins (HSP)
Mechanism of nuclear receptor structure:
Binding of hormone induces detachment of HSP; uncovers NLS then the receptor+hormone enters nucleus and acts as a transcription factor
Examples of nuclear thyroid and steroid hormones? 5
Estrogen, Glucocorticoid (Cortisol), Mineralocorticoid (Aldosterone), Progesterone,
Androgen (Testosterone)
Why would a target cell be unresponsive?
Due to lack of receptors (physiological, genetic, disease)
One hormone can influence activity of another hormone by regulation of its receptor: give 3 and explain
1.Permissiveness: one hormone is required for another hormone to work
- Synergism: actions of several hormones are complimentary. The combined effect is greater than sum of separate effects
- Antagonism: one hormone inhibits another hormone’s receptors and reduces effectiveness of second hormone
Endocrine glands:
1. Derived from?
2. Made up of?
3. Surrounded by?
4. Do they have ducts?
5. Do they have a duct system?
- Derived from epithelial tissue
- Composed of clumps of secretory cells
- They are surrounded by capillaries (fenestrated)
- No exocrine glands have ducts
- Endocrine glands have no duct system
Primary endocrine glands:
1. Where in organs?
2. Main function?
3. Where?
- discrete organs
- Main function is endocrine hormone release
- Pituitary, thyroid, parathyroid, adrenal and
pineal glands
Secondary endocrine glands:
1. Where in organs?
2. Where?
3. Function?
- Dispersed in organs
- Heart, kidney, liver, etc
- have other major functions - they are 2ndary
What is neuro-endocrinology?
Nervous and endocrine systems co-regulate
many physiological functions
What does neuro-endocrinology study?
Neuro-Endocrinology studies how the brain
regulates Pituitary hormone secretion
Neuroendocrine cells can release neurohormones give 7 places where they can be found in for example:
- adrenal medulla
- thyroid
- Pancreas / islet of Langerhans
- pituitary cells
- renin-secreting cells
- gastro-intestinal tract
- lower respiratory tract
What is endocrine gland secretion triggered by?
Hormones, neurotransmitters and metabolic factors
What are the 2 types of feedback loops and can they be excitatory or inhibitory for the endocrine system?
The 2 types of feedback loops: long-loop and short-loop
The feedback can be: excitatory AND inhibitory
What do trophic hormones do?
They regulate secretion of other hormones (either releasing or inhibitory)
Example of a trophic hormone - what is it? where is it secreted? what does it stimulate? what function does it have, i.e. what does it maintain?
Thyroid-stimulating hormone (TSH)
Is secreted from anterior pituitary
It stimulates thyroid hormone secretion from
thyroid gland
Functions in maintaining structural integrity of thyroid gland
What is the disease hyposecretion primary due to and give 7 causes:
Due to abnormality within gland
Causes:
1. Genetic
2. Dietary (eg lack of iodine)
3. Chemical or toxic
4. immunologic (autoimmune diseases)
5. cancer
6. Surgery (removal / Iatrogenic)
7. Idiopathic (unknown)
Secondary hyposecretion is due to?
Deficiency of tropic hormone
2 Causes of hypersecretion?
Tumours continuously secrete hormone
and immune factors
Primary hypersecretion is?
2ndary hypersecretion is?
Too much hormone secreted due to
abnormality within gland
Excessive stimulation of gland causes
oversecretion
