B5- Homeostasis and response

What is homeostasis?

the regulation of the conditions inside your body to maintain a stable internal environment

what happens when your receptor detects a stimulus- level is too high?

- coordination center receives and organizes a response

- effector produces a response which counteracts the change and restores the optimum level——> the level decreases

what does the nervous system consist of?

- central nervous system

- sensory neurons

- motor neurons

- effectors

what is the order of response to a stimulus?

1) stimulus (change in environment)

2) receptor (detects the change)

3) sensory neuron

4) CNS

5) motor neuron

6) effector (muscles)

7) response (movement)

what are synapses?

They are connections between two neurones

The nerve signal is transferred by chemicals which diffuse across the gap - the chemicals then set off a new electrical signal to the next neurone

what are reflexes?

rapid, automatic repossess to certain stimuli that don't involve the conscious part of the brain

measuring reaction time practical:

- sit on table with adm resting on table

- hold ruler vertically between thumb and forefinger ——> mark a starting point that should be kept the same

- drop ruler and record

-repeat test several times with different caffeine intakes (INDEPENDENT VARIABLES) —-> keep the time intervals the same (CONTROL VARIABLE)

why is reaction time recorded better on a computer?

computers give a more precise reaction time because they remove the possibility of human error + record in milliseconds for more accurate results

What are the hormones?

Chemical messengers that control the growth, differentiation, and metabolism of specific target cells

What does the pituitary gland do?

Secretes hormones to regulate other glands.—-> knows as the master gland

what do the thyroid glands do?

- produces thyroxine

- regulating things like the rate of metabolism, heart rate and temperature

what does the adrenal glands do?

regulate responses to stress, cortisol, adrenaline.

what does the pancreas do?

produces insulin which is used to regulate the blood glucose level

how do neves carry messages?

-very fast action

- act for a very short time

- act on a very precise area

how do hormones carry messages?

- slower action

- act for a longer time

- act in a more general way

what is metabolism?

sum of all chemical reactions in the body

what happens if the blood glucose level is too high?

Insulin is added, which is secreted by pancreas , which makes the glucose move from the blood into liver and muscle cells and converted into glycogen. This makes the glucose level fall.

what is Type 1 diabetes?

- the body's immune system destroys cells in the pancreas that produce insulin

- treatment = insulin therapy

- depends on a persons diet and how active they are

what is Type 2 diabetes?

- It occurs when the body does not properly use insulin

- can cause blood sugar levels to rise a lot

- obesity is a risk factor

-controlled by a carbohydrate- controlled diet and getting regular exercise

what are the four stages of the menstrual cycle?

1) Menstruation-the uterus lining breaks down

2) The uterus lining builds up again

3) Ovulation-Around day 14 a egg is released from an ovary.

4) The wall is maintained for about 14 days until day 28. If the egg has not been fertilised and implanted into the uterus lining it breaks down.

what is FSH?

-produced in pituitary gland

-causes egg to mature

- stimulates the ovaries to produce oestrogen

What is oestrogen?

- produced in ovaries

- causes lining of uterus to grow

- stimulates the release of LH and inhibits release of FSH

what is LH?

-produced by pituitary glands

- stimulates the release of an egg at say 14 (ovulation)

What is progesterone?

- produced in ovaries

- maintains lining of the uterus

- inhibits release of LH and FSH

how can hormones reduce fertility?

- oestrogen used to prevent the release of the egg

- progesterone produces a thick mucus which prevents sperm from getting to an egg

what are other method of contraception?

- condoms

- diaphragm (shallow plastic cup covered in spermicide —-> kills the sperm)

- contraceptive pill

what other methods help reduce pregnancy?

- sterilization —-> cutting or tying the fallopian tubes (permanent procedure)

-natural methods —-> avoiding sexual intercourse

what are the cons of using hormones to increase fertility?

It doesn't always work, some women may have to do it many times which can be expensive. Too many eggs could be stimulated, resulting in unexpected multiple pregnancies.

what are the cons of IVF?

- multiple births can happen

- success rate of IVF is low - stressful and upsetting

- emotionally stressful on the couple

What is adrenaline?

- A hormone that prepares the body to react

- increase the supply of oxygen and glucose to cells in the brain and muscles

what is thyroxine important for?

- regulating basal metabolic rate (the speech at which chemicals reactions in the body occur while the body is at rest)

- made from iodine and amino acids in the thyroid gland

what is genome?

all genetic material in an organisms

disadvantages of asexual reproduction of plants

-no genetic variety

-plants are genetically identical and more susceptible to the same diseases/ pathogens

Two parents do not have any alleles for polydactyly in their ordinary body cells.

These parents produced a child with polydactyly.

Explain how polydactyly suddenly occurred in this family.

caused by mutation during meiosis

causing a change in amino acid sequence

polydactyl is a dominant allele

Describe how the hormones given to women during IF treatment interact with other hormones to prepare the body for pregnancy.

FSH and LH are used in IVF -cause an increase in progesterone and oestrogen

—> maintains lining of uterus

—> lining is prepared for embryo to be inserted

what is used in IVF?

FSH and LH

Explain how the thyroid gland controls the response to a decrease in body temperature by negative feedback.

- releases thyroxine

- increases metabolic rate

- increase body temp. which decreases the release of thyroxine

what are the stages of IVF

1) Mother given FSH and LH to stimulate maturation of several eggs

2) Eggs collected from the mother and fertilised by the father outside of the body

3) Fertilised eggs develop into embryos

4) Some embryos inserted back into the mother