Endocrine System

Question 1

What does endocrine control provide?

Answer 1

Endocrine control provides a chemically mediated control system in the body alongside the nervous system.

Question 2

How is the control exerted by the endocrine system different to that of the nervous system?

Answer 2

• Nature of the control system - Endocrine exerts control by releasing chemicals where as the nervous system uses electrical control.
• Rapidity of the control system- Endocrine control responses may last for weeks, months or years. (e.g. growth) compared to the nervous system which has very short lived responses. (e.g. reflexes)
• Duration of the controlling signal - endocrine signals may take hours or days to initiate responses (e.g. steroid hormone action) in contrast with the rapid duration of neural signals e.g. action potentials.

Question 3

How is endocrine control characterised?

Answer 3

Endocrine control is characterized by the release of chemical substances - hormones - which interact with target cells to produce biological responses.

Question 4

Endocrine control can be considered to consist of 3 categories.
What are they?

Answer 4

• Autocrine control
• Paracrine control
• Classical endocrine control

Question 5

What is autocrine control?

Answer 5

Autocrine control is characterized by the release from a cell of a chemical which interacts with and influences the activity of the cell from which it was released.

Question 6

What is paracrine control?

Answer 6

Paracrine control is characterized by the release of a hormone from a cell into the interstitial fluid surrounding the cell.
The hormone remains in the interstitial fluid and diffuses a short distance where it influences the activity of a target cell.

Question 7

What is classical endocrine control?

Answer 7

Classical endocrine control is the most common form of control.
In this case, a hormone is released from a cell, enters the circulatory system, and travels some distance to influence biological activity in a target cell.

Question 8

Endocrine organs are composed of what?

Answer 8

Endocrine organs may be composed of epithelial tissue and form classic endocrine organs (e.g. pancreas, thyroid)
Alternatively endocrine organs may be composed of neural tissue (e.g. posterior pituitary gland.) In this case the hormone is released from the axon terminals of neurons. This is termed neuroendocrine control.