The classes hormones:
Proteins and Peptides – They are made of amino acids and are water soluble.
Steroids – They are made from cholesterol and are lipid soluble
Amines- They are made of small molecules made from tyrosine.
Proteins, peptides and the amines are polar and cannot penetrate the Lipid by-layer. They rely on a second messenger to get the message in the cell. They have to bind with a protein receptor on the cell membrane to get in the cell and bind to a protein receptor in the cell. They dissolve easily in the blood as they are water soluble.
Lipid soluble – They are non-polar and can easily pass through the phospholipid bilayer as they are fat soluble and do not require a second messenger. They rely on a protein carrier to move in the bloodstream.
Relationship between the endocrine system and homeostasis.
Homeostasis is the equilibrium within the body. Hormones play a major role in maintaining that. A stimulus triggers the release of a hormone through feedback regulation which can either cause an increase or decrease in the hormone secretion. A cell can only be changed if it has a receptor for a particular hormone (target cell).
Negative feedback reduces the original stimulus, while the positive feedback increases the original stimulus. Example of a negative feedback is durithe temperature regulation. In hyperthermia, the temperature which is the stimulus, triggers a command in the brain. The receptors on the skin senses the change in temperature. This causes the dilation of blood vessels near the skin to open, which causes sweating.
Example of positive feedback is the release of prolactin when a baby is nursing, which increases the milk let down.
Fight or flight is a division of the ANS, which is controlled by the hypothalamus. Body systems in an organism work together in order to maintain homeostasis. The pituitary gland, which is a part of the Endocrine system, secretes hormones which controls most of the systems in the body. In cases of fight or flight, a stimulus (fear) triggers the activation of the sympathetic system. Hormones are also released to prepare the body to either take action or to flee.
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