A concise, bullet-pointed summary on the Endocrine System. Covers strictly what you need to know for all tests and assessments (as dictated by the SAGS guidelines). Includes annotated diagrams and images to illustrate points mentioned, as well as additional research, helpful when understanding the ...
- Uses chemical messengers called hormones to send information from one body part to another
- Endocrine system consists of endocrine glands and hormones (and blood for transporting
hormones)
- Several different endocrine glands in your body
- The endocrine and nervous system work together in co-ordinating different parts of the body
- However, the endocrine system works more:
- Slowly
- Has longer lasting responses
- Is controlled by the pituitary
- Targets a wider range of organs
Histology and Functioning of Endocrine Glands
- Endocrine glands are made up of secretory cells
- Hormones are made by these secretory cells and are secreted directly into the blood
- This is different to exocrine glands which secrete their substance into the blood via a duct
- The salivary glands are an example of an exocrine gland which secrete saliva containing an
enzyme via a duct into the mouth
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, Chloë van Beukering Life Sciences Notes 2020
- Hormones: organic substances (contain carbon) made from either proteins e.g. insulin or lipids/
steroids e.g. testosterone
- Travel in the blood to other parts of the body that are called target organs
- Each hormone has a specific target organ where it creates an effect
- It can either stimulate or inhibit this target organ
- Too much or too little of a hormone leads to various problems
- Each hormone will only affect one type of target cell
- These hormones can be released in small amounts and are rather slow to start working but
their effects last much longer than the nervous system
- Some hormones can be broken down in the cells or blood very quickly though and lost in the
urine
Hypothalamus
- This part of the brain links the nervous system with the endocrine system
- When it receives a signal from the nervous system, it produces hormone that stop or start the
production of other hormones
- e.g. produces gonadotropin — releasing hormone which stimulates the anterior pituitary gland
to release follicle stimulating hormone and luteinising hormone which work on the ovaries and
testes
- Produces many other trophic hormones
- In addition, produces the important Anti-Diuretic Hormone (ADH) which acts on the kidneys
by increasing water reabsorption
- Functions:
- Helps to conserve water in the loop of Henle
- Reduces amount of urine produced, so urine is more concentrated
- Therefore, controls blood water content
- Also raises blood pressure by allowing blood vessels to constrict
- Hyper secretion:
- Stimulus: vomiting, diarrhoea, exercise, pain
- Response: less urine, more concentrated urine
- Effect: amount of water in the blood increases
- Hypo secretion:
- Stimulus: high intracellular fluid volume, decreased osmotic pressure
- Response: more urine and more dilute urine produced
- Effect: amount of water in blood decreases
Pituitary Gland (situated below brain)
- Attached to the hypothalamus
- Called the master gland because hormones it secretes control the activities of many other
endocrine glands
Hormones secreted by the pituitary gland:
Growth hormone:
- Function:
- Promotes skeletal and muscular growth by increasing mitosis and differentiation
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