Biology - B5

Homeostasis - the regulation of the conditions inside your body (and cells to maintain a stable internal environment)

- thebody has lots of automatic control systems that maintain body temperature, blood glucose and water content

There are three components - receptors                                                                                                                                            - coordination centres (brain, spinal cord, pancreas)                                                                            - effectors

Counteracts changes in the body

1. Receptor detects - level is too high or too low

2. Coordination centre organises a response

3. Effector produces a response - the level decreases or increases

Central Nervous System (CNS) - vertebrates = brain and spinal cord - mammals = sensory neurones and motor neurone

Sensory Neurone - carry information as electrical impulses from receptors to the CNS

Motor Neurones -carry electrical impulses from the CNS to the effectors

Effectors - muscles and glands which respond to nervous impulses

Receptors - cells that detect stimuli - taste/sound receptors - can form larger, comples organs (like a retina)

Effectors - respond to nervous impulses and bring about a change - muscles and glands

Stimulus -> Receptor -> Sensory Neuron -> CNS -> Motor Neurone -> Effector -> Response

- The connection between two neurones

- Nerve signal is transferred by chemicals which diffuse across the gap

- These chemical set off a new electrical signal in the next neurone

- Reflexes are rapid, automatic responses to certain stimuli that don't involve the conscious part of the brain - reduce chance of injury

- example = someone shining a bright light at someone's eyes

1. Cheeky be stings finger

2. Stimulation of the pain receptor

3. Impulses travel along the sensory neurone

4. Impulses are passed along a relay neurone, via a synapse

5. Impulses travel along a motor neurone, via a synapse

6. When impulses reach muscle, it contracts

Pituitary gland - regulates body conditions

Thyroid - produce thyroxine

Adrenal gland - produces adrenaline

Ovaries - produce oestrogen

Testes - produce testosterone

Pancreas - produce insulin

Thyroxine - regulate metabolism, heart rate and temperature

Adrenaline - 'fight or flight' response

Oestrogen - menstrual cycle

Testosterone - controls puberty and sperm production

Insulin - regulate the blood glucose level

Nerves - very fast action                                                                                                                                  - act for a very short tim                                                                                                                        - act on a very precise area     

Hormones - slower action                                                                                                                                      - act for a long time                                                                                                                              - act in a more general way

Glucagon by pancreas

- Blood glucose level TOO HIGH - INSULIN is ADDED

- Blood glucose level TOO LOW - GLUCAGON is ADDED

TYPE 1 - pancreas produces little or no insulin - blood glucose can rise to a dangerous level - insulin injected = depends on diet and activeness

TYPE 2 - resistant to their own insulin - blood sugar level can rise to a dangerous level - obesity is a risk factor

STAGE 1 - Day 1 - menstruation starts - uterus lining breaks down - 4 days

STAGE 2 - Day 4 to 14 - the uterus lining builds up again

STAGE 3 - Day 14 - an egg develops and is released - ovulation

STAGE 4 - Until day 28 - the uterus is maintained until a fertilised egg lands there

FSH - causes the egg to mature - produced in the pituitary gland - stimulates ovaries to produce oestrogen

Oestrogen - produced in the ovaries - causes lining of the uterus to grow

LH- produced by the pituitary gland - stimulates release of an egg (day 14)

Progesterone - produced in the ovaries - maintains lining of the uterus

Oestrogen - inhibits the production of FSH - stops egg development and production

Progesterone - stimulating the production of thick mucus - prevents sperm

The pill - oral contraception containing oestrogen and progesterone

- Contraceptive patch, implant and injection

Non-hormonal forms of contraception

Include

-condoms

-diaphragm

-spermicide

Sterilisation - cutting or tying the fallopian tubes or the sperm duct

'Natural' methods - looking at the menstrual cycle in advance

Abstinence - to not have intercourse

Lower levels of FSH - fertility drugs - stimulate ovulation

PROS - help a lot of women to get pregnant

CONS - It doesn't always work and can result in multiple pregnancies

In Vitro Fertilisation - in a lab

PRO - can give an infertile couple a child

CONS - multiple births, low success rate and emotional/physical stress

A hormone released by the adrenal glands

Released in respone to stressful or scary situations

'fight or flight'

A hormone released by the thyroid gland

It regulates the basal metabolic rate

Released in response to thyroid stimulating hormone, released from the pituitary gland