Unit 3.2 The Endocrine System Flashcards
What is homeostasis?
The maintenance of dynamic equilibrium in the body.
For cells to function normally, what do they need?
They need stable conditions which fluctuate within very narrow ranges.
A number of different body systems work together (integrate) to maintain a dynamic equilibrium, which system plays an important part in maintaining homeostasis?
The endocrine system.
The nervous system is able to provide fast and effective control over a whole range of body function, Sometimes there is a need to provide a sustained long term control over a whole range of body functions, what is this the role of?
Hormones.
What do hormones act as?
Chemical messengers.
Where are hormones produced and released?
They are produced in specific glands and released directly into the blood stream to control a wide range of metabolic functions.
Which two systems act together to coordinate and regulate the functions of all of the body?
The nervous and endocrine systems.
What is the difference between the nervous system and the endocrine system?
The nervous system acts on specific muscles and glands while the endocrine system helps to regulate virtually every type of body cell.
The nervous system is the body’s fast acting electrical coordination system. Impulses travel around the nervous system in milliseconds but their effect is short lived.
The second control system in the body is chemical, the endocrine system.
What are the chemical messengers called?
In the endocrine system chemical messengers called hormones are produced.
Where and hormones produced and how do they travel?
Hormones are produced in one part of the body (end endocrine glands) and transferred to another, possibly distance site by the bloodstream.
Although the endocrine system is a much slower process than a nervous response, how are the effects different?
The effects of hormones can last a very long time.
What are the mediator molecules that are released in one part of the body but regulate the effect of cells in other parts of the body?
Hormones.
How long does it take for hormones to take effect?
They may take effect in seconds, over hours, days, months or even years.
What do hormones (chemical messages) control?
Our metabolic rate, the regulation of blood sugar, and the amount of salt and water in body fluids.
In what period of life are the effects of hormones on the body seen most dramatically?
During puberty - where dramatic changes occur in the physical appearance of boys and girls as they are transformed into men and women by the sex hormones released by the endocrine system.
What are the endocrine organs, where are they found? how much do they weigh combined?
The endocrine organs are small and scattered around the body. The combined weight is around 0.1kg.
What two type of molecules are hormones nearly all either?
Hormones are nearly all either amino acid based molecules (proteins) or steroids.
What are examples of steroid hormones?
Sex hormones made by the gonads and the hormones made in the adrenal cortex. most others are proteins or protein like molecules.
Most hormones circulate around the entire body - how do they do this?
Hormones pass form the secretory cells that make them directly into the bloodstream, where they affect target cells.
What happens to the hormones in time?
They are inactivated by the liver and excreted by the kidneys.m
What occurs if someone suffers from liver or kidney failure?
Excessive levels of hormones may build up in the blood.
What are local hormones?
Local hormones acts on nearby cells or on the same cell that produced them, without first entering the blood streams. Paracrines act on neighbouring cells and autocrines act on the same cell that secreted them.
What is interleukin-2 an example of?
A hormone that behaves as both a paracrine and autocrine hormone. Interleukin-2 regulates white blood cells
What is hormone production dependent on and usually controlled by?
Hormone production is dependent on the needs of the body and it usually controlled by a feedback system.
What is the level of hormone produced often linked to the level of?
Another chemical or metabolite in the body
What is the most common feedback system for hormone production?
A negative feedback control which allows the body to control the levels of many different substances very tightly.
What happens when the endocrine gland senses the levels of a metabolite increase?
More hormone is produced which reduces the metabolite levels.
Reducing the metabolite level in turn causes what?
A fall in the level of hormone production results in the metabolite level rising again.
What is an example of a negative feedback control system?
The control of insulin and glucagon secretion by the pancreas.
What are the main endocrine glands?
The pituitary, thyroid, parathyroid, adrenal and the hypothalamus and pancreas.
As hormones are secreted directly into the blood stream, the endocrine glands do not possess what?
Ducts - for this reason the endocrine glands are also called ductless glands.
What are known as exocrine glands?
Glands that produce non-hormonal secretions like enzymes usually do possess a duct.
What 3 ways can endocrine glands be stimulated?
- Hormonal = endocrine glands can be stimulated by other hormones.
- Humoral = stimulation by changes in the levels of certain ions and nutrients in the blood.
- Neural = In some cases nerve fibres stimulate hormone release, for example adrenaline.
Where is the pituitary gland found?
The pituitary gland is a small gland found just below they hypothalamus
What is a major link between the nervous system and the endocrine system?
The hypothalamus.
The pituitary has 2 lobes, what are these called?
The anterior and posterior lobes - these control much of the activity of the cells of the body.
Where is the growth hormone produced, what is its action?
Produced by the anterior lobe of the pituitary gland, also known as somatotrophic hormone because it stimulates the somatic cells. It stimulates growth, especially of bones and muscles.
Where is the Thyroid stimulating hormone (TSH) produced, what is its action?
Produced by the anterior lobe of the pituitary gland, This stimulates the thyroid gland to secrete the hormone thyroxine (T4)
Where is the Adrenocorticotrophic hormone (ACTH) produced, what is its action?
Produced by the anterior lobe of the pituitary gland, ACTH stimulates the adrenal cortex to produce glucocorticoid hormones.
Where is the Follicle stimulating hormone (FSH) produce, what is its action?
Produced by the anterior lobe of the pituitary gland, it controls the maturation of the ovarian follicles and oestrogen production in females and the production of sperm in males.
Where is the Luteinising hormone (LH) also known as interstitial cell stimulating hormone (ICSH) produced, what is its action?
Produced by the anterior lobe of the pituitary gland. In women, LH stimulates the ovaries and leads to the formation of corpus luteum which produces the hormone progesterone.
In men ICSH causes the interstitial cells between seminiferous tubules to secret androgens (male hormones)
Where is prolactin hormone produced, what is its action?
Produced by the anterior lobe of the pituitary gland, it controls the production of milk from the mammary glands.
Some hormones are stored in the posterior pituitary until they are needed, where are these made?
In the hypothalamus.
What are the hormones released from the posterior lobe of the pituitary gland released in response to?
Nervous impulses from the hypothalamus.