Pharmacology Flashcards
what do endocrine glands do?
Secrete hormones into interstitial fluid. It is then taken up by the capillary circulation and taken to the site of action around the body.
How do exocrine glands differ from endocrine glands?
Exocrine glands release the hormones straight into the site of action whereas endocrine glands use the bloodstream.
Name the major endocrine organs
Pituitary gland Parotid Hypothalamous Thyroid gland Parathyroid Endocrine pancreas Adrenal gland Ovaries Testes Thymus
Describe the chemical nature of hormones
Hormones can be derived from amino acids e.g. tyrosine, thyroid hormones and adrenaline.
They can be steroids derived from cholesterol e.g. cortisol, progesterone and testosterone
They can be peptides derived from larger proteins e.g. ADH
Or they can be proteins e.g. insulin
Name the three types of chemical signalling
Autocrine
Paracrine
Endocrine
Autocrine
Signalling molecule/hormone released by a cell acts on that same cell
Paracrine
Signalling molecule/hormone acts locally on surrounding cells
Characteristics of endocrine hormones
Concentration of the hormone may be very low but the receptors for the hormone are highly specific.
Once bound, there is often an amplification reaction where more receptors are activated.
How are amines (amino acid derivatives) released into the blood?
A ligand binds to a receptor. This causes calcium influx which triggers pre-formed vesicles containing the amine to fuse with the membrane of the cell.
The amine is then released into the insterstitial fluid and then the blood stream.
Describe the process of storing peptides and proteins
They are from larger precursor protein molecules. They are enzymatically cleaved to produce smaller hormones by convertases. They are then packaged into storage vesicles.
How are peptides and proteins released into the blood?
A ligand binds to a receptor on the cell. This causes calcium influx causing the vesicle containing the peptides/proteins to fuse with the membrane. The peptides/protein is released into the interstitial fluid and then moves into the blood
Why do you not need a transporter to get the protein molecules into the blood?
Proteins are mainly hydrophillic and therefore can travel in the plasma.
How are steroid hormones synthesised and how are they released into the blood?
Steroid hormones are synthesised on demand (e.g. when the ligand binds to the receptor).
Cholesterol is imported into the cell and is converted to a different hormone via pregnenolone.
The hormone is released straight into the blood (no storage vesicles used for steroid hormones).
How are steroids carried in the blood?
The hormone is carried in the blood plasma bound to plasma proteins due to it being hydrophobic. When bound to plasma proteins- the hormone is pharmacologically inert.
Only the proportion of steroid unbound to plasma proteins will cause a biological action.
How do carrier proteins help with hormone function
They provide a reservoir of hormone and act as a buffer.
Explain the relationship between bound hormone and unbound hormone
There is an equilibrium set up between the proportion of bound hormone to plasma proteins and unbound. As the bound hormone cannot move across the capillary membrane to reach the target receptors, only the unbound hormone shifts across disturbing the equilibrium (decreasing the free concentration).
It therefore shifts to counteract this change and more of the hormone dissociates from the proteins.
Name some important carrier proteins
Cortisol binding globulin (CBG)- binds cortisol in a selective manner
Thyroxine binding globulin- binds thyroxine
Sex steroid binding hormone- binds testosterone and oestrial.
Albumin- binds many steroids
Describe the ways in which hormonal levels can be controlled
Negative feedback
Neuroendocrine- a sudden burst of secretion to meet a specific stimulus
Diurnal (circadian) rhythm- Secretion rate fluctuates in relation to time (day or night)
Three types of hormone receptors
G protein coupled receptors
Receptor kinases
Nuclear receptors
G protein coupled receptors
Bind mainly to amines and some peptides/proteins
Major signalling pathways are Gs, Gi or Gg
Receptor kinases
Activated by proteins/peptides
Nuclear receptors
Divided into three subtypes- class 1, 2 or hybrid class.
What type of receptors are G protein and receptor kinases?
Cell surface receptors
What type of receptors are nuclear receptors?
Intracellular receptors because the substance binding to them is lipophillic it can pass the cell membrane.
Class 1 nuclear receptor
Mainly binds steroid hormones.
In the absence of stimuli found in cytoplasm bound to inhibitory heat shock proteins.
When stimulated moves to nucleus.
Class 2 nuclear receptors
Activated mostly by lipids. Present in the nucleas
Hybrid class receptors
Bind to thyroid hormone (T3) and other hormones.
