B5

Homeostasis

Maintaining a stable internal environment

Negative Feedback

• Receptor detects a stimulus

  -level is too low/high

• The coordination centre receives and processes the information, then organises response
• Effector produces a response, which counteracts the change and restores

Effectors will just carry on producing the responses for as long as they’re stimulated by coordination centres.

Synapses

-Connection between two neurones

• Chemicals released between the gap of neurones which then triggers another electrical impulse this process happens until it goes through the whole nervous system

Nerve cells

• long
• thin
• branched connections
• carries electrical impulses

Central Nervous system

Sensory neurones (type of nerve cell) sends information from receptors around about the conditions in the body such as changes in temperature and CO2 levels to the central nervous system.

 The CNS (brain and spinal cord) sends out orders to the rest of the body through motor neurones (another type of nerve cell) to effectors (glands and muscles)

Reflex arc

Nerve pathway of our unconscious reflexes

-rapid

-automatic

-avoids harm

-bypasses CNS

Sensory neurone

Carry information as electrical impulses from the receptors to the CNS

Motor neurones

The neurones that carry electrical impulses from the CNS to effectors

Relay neurone

located in the CNS receives the impulses from a sensory neurone and which causes chemicals to be released and sends impulses to the motor neurone

The pituitary gland

secretes many hormones that regulate body conditions and is often called the ‘master gland’ as it releases hormones which act o other glands to release hormones that bring about change.

Located in the brain

Thyroid

This produces Thyroxine which is involved in regulating things like the rate of metabolism, heart rate and temperature

Located in the neck and body

adrenal gland

This produces adrenaline which is used to prepare the body for a ‘fight or flight’ response

the pancreas

Produces insulin which is used to regulate the blood glucose level

Testes (male only)

Produce testosterone, which controls puberty and sperm production in males

Ovaries (Female only)

Produce oestrogen, which is involved in the menstrual cycle

Pancreas (effects of insulin and glucagon): Negative feedback

If blood glucose level is too high insulin is added which stimulates excess glucose in the blood to be stored in thee muscles and liver as glycogen

If blood glucose level is too low then glucagon is secreted from the pancreas which stimulates the liver to turn glycogen back into glucose

Type 1 diabetes

Where the pancreas produces little or no insulin which means a person’s blood sugar lever can rise to a level which can kill them

People with type 1 diabetes need insulin therapy which involves several injections of insulin throughout the day, most likely at meal times.

This makes sure glucose is removed from the blood quickly once the food has been digested preventing the level from getting too high.

The amount of insulin needed to be injected depends on the persons diet and how active they are.

People with type 1 diabetes must be mindful of limiting the consumption of food rich in simple carbohydrates e.g. sugars and should take regular exercise to help remove excess glucose from the blood

Type 2

Where a person becomes resistant to their own insulin (insulin is still produced by the body but the body’s cells don’t respond properly to the hormone).

This can also cause a persons blood sugar levels to rise to a dangerous level.

Being overweight can increase your chance of developing Type 2 diabetes, as obesity is a major risk factor in the development of this disease.

Can be controlled by a carb controlled diet and regular exercise

Hormone inhibits release of FSH

Oestregen

What inhibits the release of LH and FSH

Progesterone

What stimulates the release of LH

Oestrogen

Contraceptives (hormonal)

• Oestrogen can be used as it stops the release of an egg as high dosages regularly inhibits FSH and eventually production of eggs stays stopped
• Progesterone reduces fertility by producing thick mucus which prevents any sperm reaching an egg
• The pill contains both progesterone and oestrogen (combined oral contraceptive pill)
  • It is over 99% effective at preventing pregnancy however its side effects can be nausea and headaches and doesn’t protect from STDs
• There is a progesterone-only pill and it has fewer side effects and is just as effective
• The contraceptive patch contains oestrogen and progesterone. It is 5 cm x 5cm patch that is stuck to the skin. Each patch lasts a week
• The contraceptive implant is inserted under the skin of the arm, releasing a continuous amount of progesterone, which stops the ovaries releasing eggs, sperm getting to the egg and the egg implanting in the uterus. It lasts 3 years
• The contraceptive injection contains progesterone. Lasts 2-3 months
• Intrauterine device (IUD) is a T shaped device that is inserted into the uterus to kill sperm and prevent implantation of a fertilised egg. Plastic ones produce progesterone and copper IUDs prevent sperm form surviving

Contraceptives (non hormonal)

Non hormonal forms of contraception stop sperm from getting to the egg.

• Condoms are worn around the penis. There are also female condoms worn inside the vagina. Condoms are the only form of contraceptive that protect against STDs
• A diaphragm is a shallow plastic cup that fits over cervix (the entrance to the uterus) to form a barrier it has to be used with spermicides
• Spermicides can be used as contraceptive but is only about 70-80% effective

Other forms of contraception

Sterilisation involves cutting or tying the fallopian tubes or sperm duct this is a permanent procedure but sometimes tubes can rejoin.

Definition of homeostasis

An organisms ability to regulate/control it's internal conditions so crucial reactions can happen at an optimal rate. (blood glucose levels, internal temperature, water levels