B1a 1 (AQA Core Biology)

• co-ordination of what happens inside your body and how your body responds to change is managed by the nervous system and hormones
• the nervous system is made up of neurones and impulses
• a reflex is an automatic response to a stimulus
• internally controlled conditions include:
  • water levels
  • ion content
  • temperature
  • blood sugar levels
• hormones are produced by glands and carried in your blood stream
• the menstrual cycle is controlled by three hormones
  • follicle stimulating hormone (FSH)
  • oestrogen
  • luteinising hormone (LH)
• these hormones can be used for the artificial control of fertility

control of the body's functions and responses involves

• hormones (chemical messangers)
• the nervous system (electrical impulses)

hormones...

• are produced by glands
• are transported around the body in the blood stream

electrical impulses.....

• pass through the nervous system

remember: hormones are chemicals passed through the blood stream, but electrical impulses are passed through the nervous system.

• Reflex actions are so quick that the brain is not used
• Here is the process of a reflex action:
  • A receptor detects a stimulus
  • A sensory neurone transmits an impulse
  • A relay neurone passes it on
  • A motor neurone is stimulated
  • The impulse is sent to a muscle/gland
  • The action is performed 

• The average cycle is 28 days long and ovulation happens on day 14
• The cycle is controlled by three hormones:
• FSH:

•  
  • Made by the pituitary gland
  • Causes the eggs in the ovaries to mature
  • Stimulates the production of oestrogen
• Oestrogen:
  • Produced in the ovaries
  • Prevents more FSH production
  • Stimulate the production of LH
  • Stimulates the build up of the womb lining
• LH:
  • Made by the pituitary gland
  • Stimulates the mature egg to be released into the womb 

The contraceptive pill contains oestrogen to prevent the production of FSH and so no eggs are matured

Pills for encouraging pregnancy contain FSH to stimulate the start of the menstrual cycle

IVF (in vitro fertilization)

1.Fertility drugs (FSH) are used to induce eggs to mature
2.The eggs are collected and placed in a Petri dish with a sample of semen
3.The eggs are checked to find out if they are fertilized and developing properly
4.One or two embryos are placed inside the mother in the hope that at least one will develop into a healthy baby 

The internal conditions of the body have to be carefully controlled

Some internal conditions include:

• Water content
• Temperature
• Ion content
• Blood sugar level

Water content is controlled by sweat, water droplets in breath, excess water in urine (controlled by kidneys)

Ions are also lost in sweat and urine

If our internal temperature is not kept constant the enzymes in our body may not work properly

Sugar is the energy source for our cells so the level must be controlled carefully.