The Endocrine System Flashcards
Exocrine glands
Secrete substances into a duct which then carries the secretion to the surface of the body or the secretion to the surface of the body or a body cavity. E.g. sweat glands and salivary glands.
Endocrine glands
Secrete substances directly into the extracellular fluid, that surrounds the cells which make up the gland. From here the secretion can then move into the blood capillary and be transported anywhere in the body by the blood.
Hormone
A substance secreted into the blood stream by an endocrine gland that affects the functioning organ organ or cell.
Hormones work to alter the activity of cells by
- Changing the permeability of the cell membrane
- Changing the rate of chemical reactions which occur in the cell.
Paracrines
(Local hormones) secrete chemicals to communicate with cells in the same tissue.
Types of hormones
- Proteins
- Amines
- Steroids
Action of protein and amine hormones - water soluble
Protein and amine hormones attach to a specific receptor molecule on the cell membrane. This causes a secretory messenger substance to diffuse through the cell and activate the required enzymes (insulin)
Action of steroid hormones lipid soluble
Steroid hormones enter inside the cell through the cell membrane and combine with a receptor protein. It then diffuses in the cell nucleus where it activates genes controlling the formation of specific enzymes (testosterone, oestrogen)
Protein and amine hormones generally end in
in or ine
Steroid hormones tend to end in
ole or one
What do the hormones do?
i) Activate the genes in the nucleus so that a particular enzyme or structural protein is produced (TYPE)
ii) Change the shape or structure of an enzyme so that it is turned ‘off or on’ (ACTIVATES)
iii) Change the rate of production of a enzyme or proteins by changing the rate of protein synthesis (QUANTITIES)
Note: Hormones are NOT enzymes
Enzyme application
Hormones are extremely potent
One hormone molecule can trigger the synthesis of many enzyme molecules. I.e. very small stimulus can produce very large effect.
Pituitary gland
Pituitary gland ( or hypophysis) regulates activity of other endocrine glands, therefore referred to as the master gland. Located below the hypothalamus.
Anterior and posterior lobes which each function separately.
Anterior lobe connection
Nerve centres in the hypothalamus are connected by a portal blood vessel (blood capillaries at both ends)
Anterior lobe stimulation
Hypothalamus releases hormonal releasing or inhibiting factors in to the portal vessel which takes them to the anterior lobe where they stimulate and release their hormones.
Posterior lobe connection
Nerve centres are connected by neurons
Posterior lobe stimulation
Hormones are manufactured in the dendrite ends of the neuron in the hypothalamus. Hormones travel down the neuron and are stored, in the axon terminal. A nerve impulse triggers their release into the bloodstream.
Posterior lobe
Does not produce hormones it only releases the hormones into the bloodstream (made by hypothalamus.)
