What are hormones? Briefly describe how they come about and what they do...
- hormones are chemical substances which can either be proteins or steroids
- they are produced by specialised glands called endocrine glands
- they are transported in the blood and they alter the activity of one or more organs called target organs
- once the hormone has performed its function it is then destroyed by the liver
What does the endocrine system do?
It is a communication system which transports messages around the body by chemicals called hormones
What are the endocrine glands?
- the endocrine glands make up the endocrine system
- they are organs made of specialised secretory cells - their function is to produce hormones then secrete them into the blood stream
- they contain a dense network of blood capillaries to secrete the hormones into
What hormone is produced by the endocrine gland called the 'adrenal' gland and what is its function?
- the adrenal gland produces adrenaline
- it prepares the body for physical activities which require energy and quick reflexes
What hormone is produced by the endocrine gland the 'pancreas' and what is its function?
- the pancreas produces insulin and/or glucagon
- if blood sugar levels are high then insulin reduces blood glucose levels at the liver and the sugar is stored in liver and muscle cells as glycogen
- if blood sugar levels are low then glucagon increases blood sugar levels at the liver by converting the liver glycogen into sugar and releasing it into the blood stream
What hormone is produced by the endocrine gland the 'testis' and what is its function?
- the testis produces the hormone testosterone
- it controls the development of the male secondary sexual characteristics
What hormone is produced by the endocrine gland the 'ovary' and what is its function?
- the ovary produces the hormone progesterone
- this regulates the female menstrual cycle and maintains pregnancy
What is the function of adrenaline?
Adrenaline prepares the body for stressful situations where lots of energy and fast reflex actions may be needed - "fight or flight"
What are some of the symptoms of adrenaline in the blood stream and why/how do they happen?
- increased heart rate
- blood flowing quickly in veins
- deep / fast breathing
- when you are in a stressful situation your brain sends nerve impulses to the adrenal glands and stimulates them to produce and secrete the hormone adrenaline into the blood stream
What actually happens when adrenaline reaches the heart?
It causes the heart muscle to contract and relax faster, which in turn makes sure that oxygen and glucose reach the muscles of the body at a quicker rate.
How does adrenaline affect breathing?
- it causes the diaphragm and intercostal muscles to contract and relax faster which increases the rate of breathing
- these changes in breathing bring about an increase in the respiratory rate so that increased amounts of energy are produced
What does adrenaline do when more sugar is required?
It converts the liver and muscle stores of glycogen into glucose and the glucose is secreted into the blood to be used in respiration