Biology Paper 1 Topic 3 - Organism Level Systems

What is the nervous system composed of?

the central nervous system (brain and spinal cord) and the peripheral nervous system- all the other nerve cells that connect to the CNS

How does the CNS coordinate a response?

It receives stimuli from the environment via receptors in sense organs

How are messages carried to different parts of the body?

As electrical impulses via neurones

What do sensory neurones do?

Carry impulses from receptors to the CNS

What do relay neurones do?

Pass the impulse to a motor neurone

What do motor neurones do?

Send the impulse to an effector which is a muscle or a gland which produces a response

What is the connection between two neurones called?

A gap called a synapse

What happens when the impulse reaches the synapse?

It stimulates the release neurotransmitter chemicals from the neurone

What do the chemicals then do?

They diffuse across the gap and bind to receptors on the next neurone

What happens next at the synapse?

A new electrical impulse is triggered, and at the synapse the message goes from electrical to chemical and back to electrical.

What are reflexes?

Automatic responses to certain stimuli. You do not think about them.

What is the function of a reflex?

To protect the body

What is the pathway of a reflex?

Not the brain - it goes via the spinal cord so it is quicker

Do reflexes happen faster than a coordinated response?

Yes

What happens when touching a hot object?

1. Receptors in the hand detect pain, 2. Impulse sent via sensory neurone to CNS, 3. Impulse crosses synpase to relay neurone, 4. Impulse crosses synapse and is passed along motor neurone, 5. Response by effector muscle is to move hand away

What happens to the eye in dim light?

Increased pupil size, Radial muscles contract, Circular muscles relax

What happens to the eye in bright light?

decreased pupil size, radial muscles relax, circular muscles contract

What are hormones?

Chemical messengers produced by glands

Where are hormones released and where do they travel?

released directly into the blood and travel to target organs

What do the cells of the target organ contain?

Receptors to which the hormone can bind

What hormones do the pituaitary gland produce, and what are their functions?

LH,FSH: Involved in reproduction, ADH: Controls water content of blood, Growth hormone: Stimulates growth

What hormone does the thyroid gland produce, function?

Thyroxine: controls metabolism

What hormones does the pancreas gland produce, function?

Insulin and glucagon: controls blood glucose levels

What hormones does the adrenal gland produce, function?

Adrenaline: fight or flight

What hormones does the ovaries produce, function?

Oestrogen and progesterone: reproduction and secondary sexual characteristics

What hormone does the testes produce, function?

testosterone: secondary sexual characteristics

What is hormone production often controlled by?

Negative feedback

What would happen if there was a rise or drop in hormone levels?

Rise: reduce hormone production, Drop: increase hormone production

Where is thyroxine produced, what does it do?

Produced in the thyroid gland, regulates metabolism

What happens when the level of thyroxine drops?

The pituitary gland produces thyroid stimulating hormone (TSH)

What does TSH do?

stimulates the thyroid gland to produce thyroxine

What happens when thyroxine levels increase?

Production of TSH decreases so thyroxine levels return to normal (negative feedback)

Where is adrenaline produced, and why?

Adrenal gland in response to exercise, anxiety or fear

What does adrenaline do to our bodies?

Increases heart and breathing rates

Increases rate of blood supply to the muscles

Raises blood glucose levels in preparation for fight or flight

What does oestrogen do?

Stops FSH being produced, causes the build up of the uterus wall, stimulates pituitary gland to release LH

What does progesterone do?

maintains the lining of the womb, inhibits LH production

what does follicle stimulating hormone do?

causes an egg to mature in an ovary and stimulates the ovaries to release oestrogen

What does LH do?

triggers ovulation (the release of a mature egg)

What happens at the stages of the menstrual cycle? 1. uterus lining breaks down (period), 2. repair of the uterus wall. Oestrogen causes the uterus lining to gradually thicken, 3. egg released by the ovary, 4. progesterone and oestrogen make the lining stay thick, waiting for a fertilised egg, 5. No fertilised egg so the cycle restarts

What happens when oestrogen is taken daily as a form of contraception?

The high levels produced inhibit production of FSH so egg development and production eventually stop

How does progesterone reduce fertility?

It causes a thick sticky mucus to be produced at the cervix, which prevents sperm from reaching the egg

Is the pill effective?

Very effective, but can cause side effects and do not protect against sexually transmitted infections (STIS)

Are barrier forms of contraception e.g. condoms effective?

Yes as they may protect against STDS, however they cam be less reliable than hormone methods if they aren't used correctly

Advantages and disadvantages of the contraceptive pill?

Advantages- more than 99% effective, can reduce the risk of getting some types of cancer, Disadvantage- does not protect against STDS, can have side effects

Advantages and disadvantages of condoms

Advantages- 98% effective, protect against STD, Disadvantage- can only be used once

What can be given to women who have low levels of FSH?

They can be given drug containing FSH or LH to stimulate the release of eggs

Why are fertility drugs given to couples undergoing in vitro fertilisation?

to stimulate egg production to allow several eggs to be collected at one time, and those eggs are fertilised outside the body, the cells divide to form an embryo which is inserted into the women's uterus

What are ethical issues of IVF

Who has the right to decide which embryos live or are destroyed

Economic issues of IVF

is the costs of development worth the rewards?

Social issues of IVF

the effect on people

Limitations of IVF

we still don't know why incidence of failure in IVF is so high, also don't know when an embryo is a person, and if destroying an embryo is the same as taking a life, different people have different opinions

What is homeostasis?

Keeping the internal body environment constant

What does the body need to control levels of and why?

Water, glucose and salts to ensure chemicals can be transported effectively into and out of cells by osmosis and active transport

Why does the body need to maintain a constant temperature?

Since chemical reactions in the body are catalysed by enzymes that function best at their optimum temperature

Where does sugar in the blood come from?

What we eat

What are blood sugar (glucose) levels controlled by?

The pancreas

what happens if blood glucose concentration is too high?

the pancreas releases insulin, glucose is converted into insoluble glycogen stored in the liver, glucose is removed from the blood and blood glucose concentration returns to normal

Why does the pancreas produce insulin?

it causes cells to become more permeable to glucose. Glucose moves from blood into cells

What does does insulin cause the liver to do?

turn excess glucose into glycogen

When does the pancreas produce the hormone glucagon?

when blood glucose levels fall e.g. during exercise

What does glucagon cause the liver to do?

Convert glycogen into glucose and release it into the bloodstream

What happens if blood glucose concentration is too low?

the pancreas releases glucagon, insoluble glycogen from the liver is then converted into glucose, which is released into the blood, the blood glucose concentration returns to normal

What is diabetes?

A condition that causes a persons blood sugar level to become too high.

Is type 1 and type 2 diabetes common?

Type 1 is less common, Type 2 is most common

When does type 1 and type 2 diabetes develop?

Type 1 - develops suddenly often at a young age, Type 2 - develops gradually often in people in 40 who may be overweight

What are the causes of type 1 and type 2 diabetes?

Type 1 - pancreas does not produce insulin, Type 2 - not enough insulin is produced or cells are not affected to insulin

What are treatments for type 1 and type 2 diabetes?

Type 1 - insulin injections for life, plus eating sensibly, Type 2 - Healthy eating, exercise, possible medication