Endocrine system Flashcards
Endocrine system definition
All tissues or glands that secrete hormones
Homeostasis definition
Any self-regulating process by which biological systems tend to maintain stability while adjusting to conditions that are optimal for survival
Why is homeostasis so important
- If homeostasis is successful, life continues
- If unsuccessful, disaster or death ensues
Homeostasis feedback loop
To make sure the body maintains homeostasis the endocrine system uses feedback mechanisms, which are responses that trigger specific activities or processes
Positive feedback loop
The product of a reaction enhances the reaction producing the product
Negative feedback loop
The product of a reaction leads to down regulation of the reaction producing the product
Hormones definition
Chemical messengers that are secreted directly into the blood, which carries them to organs and tissues of the body to exert their functions and processes
Hypothalamus
Production of ADH
Pineal gland
Melatonin
Pituitary gland
Release of oxytocin and ADH
Thyroid gland
Thyroxine
How does the endocrine system work
Endocrine gland secretes the hormone into the bloodstream until it reaches the target cell due to having a specific receptor
Hormone-receptor complex
The combination of a hormone and its bound receptor
2 chemical classifications of hormones
- Steroid hormones
- Non-steroid hormones
Steroid hormones
A chemical structure like cholesterol, meaning they are soluble in lipids, so they diffuse easily through cell membranes
- Reproductive hormones
Non-steroid hormones
- Are not lipid soluble, so they cannot easily cross cell membranes
- Can be subdivided into 2 groups: protein or peptide hormones and amino acid-derived hormones
What determines the level of activation
- Hormone concentration
- Number of target cell receptor sites
- Hormone receptor sensitivity
Hormone concentration
Depends on intensity/duration of initial stimulus
Number of target cell receptor sites
Up/down regulated
Hormone receptor sensitivity
Different tissues have a different number of receptors – not all equally sensitive to same hormone
Up and down regulation
The number of receptors on target cells can be altered to increase or decrease that cells sensitivity to the hormone
Anterior pituitary gland
- Controlled by the hypothalamus
- 6 anterior pituitary hormones
Thyroid gland
- 2 important non-steroid hormones which regulate metabolism in general
- Increase protein synthesis/increase cell size/promote rapid glucose uptake/enhance glycolysis and gluconeogenesis.
Adrenal glands
- Epinephrine and norepinephrine
- Increases heart rate and force of contraction, metabolism, release of glucose, redistribution of blood
