Homeostasis (merged)

What is homeostasis?

The state of balance in the body when the temperature and other conditions are stable for cells and enzymes to work.

The regulation of internal conditions of a cell or organism to maintain optimum conditions for function in response to internal and external changes.

What should a runner do to reduce dehydration?

Drinks lots of water

To replenish water lost through sweating

What are the main internal conditions?

• Body temp

• Water levels

• Blood glucose levels

What are the features of the automatic control system?

What is a reflex arc?

1. Stimulus is detected by receptor

2. Electrical impulses travel along sensory neurones to the CNS

3. Reaches the synapse where a chemical is released

4. Diffuses to a relay neurone and triggers an electrical impulse which travels across relay neurone.

5. Reaches another synapse & another chemical released

6. Chemical triggers an electrical impulse in a motor neurone.

7. Electrical impulse travels down motor neurone to an effector

8. E.g. hand touches heat, skin (receptor) senses heat, effector (muscle) contracts and pulls hand away from heat (response).

What is a reflex?

• No decision making from the conscious part of the brain

• Automatic & rapid

• Protect us from danger

• E.g. removing hand from heat, protect face from object in flight

Reaction time Required Practical method

1. Person 1 sits on stool with dominant hand over table

2. Person hold meter ruler with 0 mark between P1 thumb and first finger

3. P2 drops ruler at random time

4. P1 must catch the ruler as fast as possible

5. Measure cm spot that the ruler was caught

6. Record on a table and repeat 10 times to calculate mean

7. Repeat with different people

What is the function and name of the master gland in the brain?

Pituitary gland - coordinates many hormones

What is the Endocrine system?

• Number of glands which secrete hormones into blood stream. Blood carries hormones around body.

• Slower and longer lasting effect than nervous system

Label this Endocrine system diagram

What are the functions of the glands?

• Pancreas - Blood glucose concentration

• Ovaries & Testes - Puberty & reproduction

• Thyroid - Growth & Basal metabolic rate (How fast chemical reactions happen)

• Adrenal glands - release adrenaline when stressed

• Pituitary gland - Releases different hormones depending on conditions and act on other glands.

How is blood glucose concentration controlled?

• Carbs cause blood glucose concentration to rise.

• Pancreas senses this and produces hormone insulin.

• Triggers body cells to take glucose from blood.

• Triggers liver and muscle cells to store it as glycogen

• If blood glucose concentration falls too low, glucagon triggers liver cells to turn glycogen back into glucose into blood.

What is diabetes? Describe the types.

Type 1 - Pancreas doesn’t produce enough insulin. When carbs are consumed, the blood glucose rises but doesn’t go back down as far as it needs to

Type 2 - Body stops responding to the insulin produced. Must avoid carbs and exercise.

Explain this diagram

From kidneys to bladder

1. Blood passes through capilleries

2. Small molecules are filtered out (Urea, ions & water, glucose)

3. Pass into tube (yellow)

4. (Green arrows) Some of the molecules (not urea) are reabsorbed into blood (Selective reabsorption)

5. Urea, excess ions & excess water are released as urine.
   

How does the body deal with excess amino acids?

• Amino acids go into blood during digestion

• Liver breaks down excess amino acids into ammonia (Deamination)

• Ammonia is toxic so it it converted into urea

The menstrual cycle

1. Ovulation (release of egg) every 28 days

2. To prepare, uterus lining becomes thick and spongy

3. Egg goes to uterus and can be fertilised if sperm is present, then implant into uterus wall, develop into a baby

4. If not fertilised, egg and uterus lining is released (period)

Hormones during the menstrual cycle

1. Follicle stimulating hormone (FSH) causes egg to mature in ovary

2. Luteinising hormone (LH) causses ovulation

3. Oestrogen (Produced by ovary) and progesterone maintain uterus lining incase egg is fertilised and implants.

How do the hormones interact with the menstrual cycle?

1. Pituitary gland releases FSH

2. FSH travels in blood to ovaries, causing egg to mature

3. FSH triggers ovaries to produce oestrogen, causing lining to become thick & stops pituitary gland releasing FSH

4. Pituitary gland release LH, triggers ovulation

5. Ovaries now produce progesterone, stops pituitary gland releasing LH and FSH to stop anymore eggs maturing or being released.

6. Progesterone also causes lining to become thick. progesterones falls if not fertilised, uterus lining and egg are released (period)

How does the pill work?

The pill - contains hormones which prevent the production of FSH which stops any eggs maturing. Highly effective if taken correctly (everyday)

Side effects: Risk of breast cancer, blood clots

What other hormone methods can a woman use for contraception?

Implant / Skin Patch / Injection, contains progesterone stopping the egg maturing or being released.

More convenient than taking a daily pill, has side effects

These don’t prevent STI’s or STD’s

What barrier methods are there?

Condom/Diaphragm: Barrier method stops sperm reaching egg, effective if used correctly.

Adv: no side effects

Disadv: condoms can break or slip off

More effective if used with a spermicide gel which kill or disable sperm.

What are surgical forms of contraception?

• Sterilisation

• Prevent women’s eggs reaching uterus

• Men: Prevents sperm leaving the penis.

• Difficult to reverse, be certain they don’t want children.

• Don’t protect against STI’s

What is the natural form of contraception?

• Abstain from sex after ovulation

• Hard to tell when ovulation occurs

• Doesn’t protect against STI’s

Opinions on contraception

• Some religions see it as unethical

• Some people think everyone should be able to choose for themselves.

• Condoms reduce risk of STI’s

What options are there to treat infertility?

• Fertility drug - injection of LH & FSH, ovulate more than usual

• IVF - fertilisation outside of body. First administer FSH & LH, eggs mature, collected, collect sperm and fertilise eggs in lab. Develop into embryos which are inserted into the womb.

• Not high success rates

• Emotionally stressful & Physically demanding on mum

• Lead to multiple births (risky for mum and babies)

• Ethical views: Destroying unwanted embryos

• Expensive

What is adrenaline?

Adrenal glands (On top of kidneys) release adrenaline in fear or stress. Released into blood. Increases heart rate to deliver more oxygen and glucose to body (Fight or flight)

What is thyroxine?

Thyroid gland in base of neck

Releases Thyroxine

Stimulates the basal metabolic rate (makes bodys chemical reactions take place faster)

Role in growth and development

What is a negative feedback loop?

What is phototropism, how was it investigated?

When plants grow towards the light.

1. Shine light onto shoots from one side

2. The shoots lean towards the light

3. When the tips of the shoot were cut off, they didn’t grow towards the light.

4. Suggested that the tips produce plant hormone auxin

5. Covered tips with foil, again didn’t grow to light so the tips are sensitive to light.

6. Covered bottom with foil and the tip still grew towards the light, so the bottom isn’t sensitive to light

WHat other chemical are used in plants?

• Gibberellins - germination of seeds

• Ethene - controls cell division and fruit ripening

Plant Response RP (light) and variables

Investigate light intensity on height of seedlings

IV - light intensity

DV - Height

CV - Water volume

The full and partial light seedlings have similar heights because the chlorophyll is very efficient at absorbing light energy. They don’t need full light to grow

They tilted towards the light - phototropism

Darken ess - grew longest, when the seeds germinate, they grow rapidly to reach the light and in the darkness they continued grow rapidly to try and reach the light. Small yellow leaves, no energy for photosynthesis

How are hormones used in agriculture and horticulture?

Auxins - weed killers, rooting powders, promoting growth in tissue culture

Gibberellins - Force a seeds to germinate before it normally would (end seed dormancy), encourage plants to flower, make fruit grown larger

Ethene - Ripen fruits just before sale.

Homeostasis

The maintenance of a constant internal enviro ment in response to environmental changes

Thermoregulation

Maintain and regulate internal body temperature at 36-37c as enzymes work best at their optimum temperature.

Osmoregulation

Maintain and regulate water content from exhalation, sweating, and urine

Endocrine gland

Releases hormone to maintain homeostasis

Hormone

A chemical substance (protein) produced by a gland and carried in the bloodstream which alters the activity of specific target organs and brings about a change in other cells.