Chemical control in mammals
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Summary
Chemical control in mammals
In a nutshell
Chemical control in mammals is enabled by the endocrine system which secretes hormones into the bloodstream. Hormones can have widespread effects over the body following interactions with receptors.
Endocrine glands
Endocrine glands are a group of ductless glands that secrete hormones into the blood stream with the intent of inducing a change in a target organ. Hormones travel around the blood stream and interact with specific receptors. Hormones are metabolised in the liver and removed from the body through excretion. Hormones do not have long lasting effects.
The endocrine system is overseen by the "master gland" the pituitary gland. The pituitary gland operates closely with the hypothalamus. The hypothalamus releases hormones which control the function of the pituitary gland. The pituitary gland and the hypothalamus provide a vital link between the nervous and endocrine systems.
Mechanism of action
There are two distinct types of hormones. They interact with specific receptors ensuring their effects are only induced in target cells/organs.
Amides or peptides
Amides or peptide hormones interact with receptors presented on the surface of target cells inducing intracellular changes.
Example
Melatonin is an amide/peptide hormone. It is secreted by the pineal gland and regulates circadian rhythm.
Steroids
Steroid hormones are able to pass through cell membranes allowing them to interact with receptors presented in the cytoplasm and induce intracellular changes.
Example
Testosterone is steroid hormone produced in the testes, it is important to male sexual development.
Multiple effects
A benefit of hormonal control is that one hormone has the ability to induce widespread effects on different systems in the body. Receptors presented by cells are the only requirement to induce effects following hormone interaction.
Adrenaline
Adrenaline is a hormone released by the adrenal glands. It is responsible for overseeing the "fight or flight" response. When adrenaline is released it has widespread effects all over the body.
Part of the body | Effect of adrenaline |
| Heart | Increases heart rate so oxygen is readily available to the muscles. |
| Circulatory system | Induces vasoconstriction increasing blood pressure. |
| Liver | Induces the conversion of liver glycogen stores so glucose is readily available for respiration. |
| Lungs | Increases breathing rate so there is more oxygen taken into the blood stream for respiration. |
| Muscles | Increases the ability to contract quickly. |
FAQs - Frequently Asked Questions
How do hormones induce effects?
Hormones travel around the blood stream and interact with specific receptors.
What is the master gland of the endocrine system?
The endocrine system is overseen by the "master gland" the pituitary gland. The pituitary gland operates closely with the hypothalamus.
What are the endocrine glands?
Endocrine glands are a group of ductless glands that secrete hormones into the blood stream with the intent of inducing a change in a target organ.