Endocrine System Flashcards
What is homeostasis?
The maintenance of a relatively stable internal environment despite continuous changes outside
What does the endocrine system do?
It releases chemicals called hormones that regulate complex body processes
What do hormones do?
Travel through the blood and alter activity of target cells
What processes does the endocrine system regulate?
Complex processes such as growth and development, metabolism, reproduction
What other system does the endocrine system act with?
It acts with the nervous system to coordinate and integrate activity of cells
What is Endocrinology
Study of hormones and endocrine organs
What does the endocrine system control?
Reproduction, growth and development, maintenance of electrolyte and water and nutrient balance of blood, regulation of cellular metabolism and energy balance, mobilisation of body’s defenses
What are hormones?
Long distance chemical messengers
Secreted by endocrine glands
Modify physiological activity of target cells
Travel in blood or lymph
What are the characteristics of endocrine glands?
They produce hormones
They lack ducts
What are the characteristics of exocrine glands?
They produce non hormonal substances (e.g sweat or saliva)
Have ducts to carry secretion to membrane surface
What is a hormone receptor?
Protein located in target cell (cytoplasm, nucleus, cell membrane)
Binds to hormone and activates changes leading altered activity
Different tissues have different combinations of receptors, presence or absence of specific receptor determines hormonal sensitivity of cell
Which three factors does activation of target cell depend on?
- Blood levels (concentration) of hormone
- Relative number of receptors in/on target cell
- Affinity (strength) of binding between receptor and hormone
What is up-regulation?
When target cells form more receptors in response to low hormone levels
What is down-regulation?
When target cells lose receptors in response to high hormone levels
Why is down-regulation important?
It desensitises target cells to prevent them from overreacting to persistently high hormone levels
