Metabolism S7 - Endocrine System Flashcards
Define ‘Hormone’ and briefly describe the features of hormone control.
A hormone is a chemical messenger that travels via the bloodstream
Hormones are secreted from endocrine glands and travel in the bloodstream to target cells where they exert their effect.
What are the classes of Hormone?
Polypeptide
Glycoprotein
Amino acid derivatives
Steroids
Describe the physical features of polypeptide hormones and give some examples of polypeptide hormones
Short or long chain amino acids
Eg. Insulin, Glucagon, Growth hormone
Describe the physical features of glycoprotein hormones and give some examples of glycoprotein hormones
Large protein molecules with carbohydrate side chains
Eg. Luteinizing hormone, Follicle stimulating hormone, Thyroid stimulating hormone
(Notice these are all anterior pituitary hormones, good way to remember)
Describe the physical features of Amino acid derivative hormones and give some examples of amino acid derivative hormones
Small molecules synthesised from amino acids
Eg. Adrenaline, Thyroxine, Tri-iodothyronine
From what are steroid hormones derived?
Give some examples of steroid hormones
All derived from Cholesterol
Cortisol, Aldosterone, Testosterone, Oestrogen
What Hormones are hydrophilic and which are hydrophobic?
Why is this significant to their transport around the body?
Hydrophillic: Polypeptide hormones, Glycoproteins hormones and adrenaline
Hydrophobic: Steroids and thyroid hormones
Hydrophobic need special transport proteins to dissolve in blood (small amount dissolves in plasma) for transport whereas hydrophilic hormones can travel dissolved in plasma.
Why is transport method of hormones in blood relevant to their effect on target cells?
Bound hydrophobic proteins are not physiologically active, therefore only the concentration of free/unbound hormone matters.
Give an example of the physiological effects of hormone deficiency or excess of a particular hormone
Growth hormone
Excess leads to acromegaly
Deficiency leads to failure to grow properly
Your example may vary, Check it!
How is hormone binding to a target cell dependent on it’s chemical nature?
Hydrophobic hormones can cross the plasma membrane and bind to cytoplasmic or nuclear receptors
Hydrophilic hormones cannot cross the cell membrane readily so will bind to receptors on the cell surface
Give a brief description of a hormones binding and affect on a target cell
Will bind to a specific, high affinity receptor
This binding will trigger a change in the cell
Eg. Enzyme/protein activity, gene expression
When a hydrophilic hormone binds to the target cell, what process occurs before a change is cell activity is exerted?
Binding on the cell membrane will often trigger a secondary messenger within the cell which will in turn influence cell activity.
What is target tissue response time to a hormone dependent on?
Show an rough appreciation of the difference in response time.
Rapid response (seconds to minutes) is seen when hormone effect is altering the activity of functional proteins such as enzymes or transport proteins
Slower response (minutes to hours) time is seen to hormones that alter gene expression
Do hormones always have only one target tissue?
Give some examples of hormones and target tissues
No, they can hove one or multiple
For example:
TSH only affects thyroid gland
Insulin has effects on the Liver, Muscle and Adipose tissues
What are the 4 ways in which hormone secretion is controlled?
Negative feedback
One hormone controlling another
Releasing or inhibiting control hormones
Inactivation of Hormones
How is negative feedback used to control hormone secretion?
Secretion rate is affected by blood concentration.
As soon as blood concentration/the effect of a hormone decreases below critical level this stimulates secretion of the hormone until correct level is achieved.
Give an example of negative feedback hormone control.
Insulin secretion
Beta cells of the pancreas are sensitive to blood glucose concentration, when blood glucose rises above 5mM then this stimulates Insulin secretion
What are hormones that control other hormones called?
Where are they secreted from?
Hormones controlling another hormone are called trophic hormones
They are mostly secreted by the anterior pituitary gland.
Give the 6 main hormones secreted by the pituitary gland.
TSH - Thyroid stimulating hormone
ACTH - Adenocorticotrophic hormone
GH - Growth hormone
LH - Luteinizing hormone
FSH - Follicle Stimulating hormone
Prolactin
Give 4 examples of trophic hormones
Thyroid stimulating hormone
Adenocorticotrophic hormone
Luteinizing hormone
Follicle stimulating hormone
Give an example of a trophic hormone controlled by negative feedback and describe the process of negative feeback in this instance.
Thyroid stimulating hormone
When thyroid hormone concentration in the blood gets too high then TSH secretion falls, therefore thyroid hormone secretion falls
The opposite is true for a fall in thyroid hormone concentration
Your example may vary, check it!
Explain the action of Inhibiting or releasing hormones and give 4 examples
These hormones are secreted from nerve cells in the hypothalamus and travel to the gland via hypophyseal portal vessels.
This allows the brain to control hormone secretion
Thyrotrophin releasing hormone
Corticotrophin releasing hormone
Somatotrophin releasing hormone
Somatostatin
What organ does thyroid stimulating hormone affect?
Thyroid
What gland does Adenocorticotrophic hormone affect?
Adrenal glands
