Biology paper 2

What is homeostasis?

Homeostasis is the regulation of the conditions in your body (and cells) to maintain a stable internal environment, in response to changes in both internal and external conditions.

Homestasis also maintains optimal conditions for enzyme action and cell functions.

What 3 factors does homeostasis control?

• Blood glucose concentration

• Body temperature

• Water levels

Why does your body use negative feedback?

If the level of something (e.g water or glucose) gets too high or too low, your body uses negative feedback to bring it back to normal.

What happens during negative feedback?

1. Receptors detect a stimulus (change in environment)

2. Co-ordination centre receives and processes the information then organises a response.

3. Effectors produce a response which reduces the change and restores the optinum levels.

What does the nervous system do?

Allows humans to react to their surroundings and coordinate their behaviour.

Where is the sensory nervous system?

The brain and spinal cord.

What do sensory neurones do?

Neurones that carry information as electrical impulses from the receptors to the central nervous system.

What do motor neurones do?

Motor neurones carry information as electrical impulses from the central nervous system to effectors.

What are effectors? And how do they respond

All your muscles and glands, which response to nervous impulses.

Muscles contract in response to nervous impulses. Glands secrete (produce and release) hormones.

What is a synapse? And how do they work?

The connection between two neurones is called a synapse.

When the nerve impulse reaches the end of the first neurone, it releases neurotransmitters. These chemicals diffuse across the synapses and attach to the receptors of the next neurone → triggering a new electrical impulse

What are reflexes?

Reflexes are rapid, automatic responses to certain stimuli that don’t involve the conscious part of your brain. → prevents risk of injury

What is a reflex arc? And where do neurones in a reflex arc go through?

The passage of information in a reflex. (From receptor → effector)

Neurones in a reflex arc go through the spinal cord or the unconscious part of the brain .

What happens during a reflex?

1. When a stimulus is detected by a receptor, impulses are sent along a sensory neurone to a relay neurone in the central nervous system.

2. When impulses reach the synapse between the sensory neurone and the relay neurone, they trigger chemicals (neurotransmitters) to be released. These chemicals cause impulses to be sent along the relay neurone.

3. When impulses reach the synapse between the relay neurone and the motor neurone, they trigger chemicals to be released. These chemicals cause impulses to be sent along the motor neurone.

4. The impulses then travel along the motor neurone to the effectors .

5. Lastly, the muscle contracts and moves your hand away from the (stimulus) .

What are hormones?

Hormones are chemical molecules released into the blood and carried to other parts of the body, but only affect particular cells in target organs (particular organs). Hormones control things in cells and organs that need constant adjustment.

hormones also have long-lasting effects

Where are hormones produced (and secreted by)?

Endocrine glands → which make up your endocrine system.

What happens in the pituitary gland? (Master gland)

Produces many hormones that regulate body conditions because some of these hormones stimulate other glands to release their own hormones , in response to changes in the body.

What happens in the thyroid gland?

Produces thyroxine and regulates the rate of metabolism, heart rate and temperature.

What happens in the ovaries gland?

Produces oestrogen which is involved in the menstrual cycle. (In women)

What happens in the testes?

Produces testosterone which controls puberty and sperm production in men.

What happens in the adrenal gland?

Produces adrenaline which prepares the body for a ‘fight or flight’ response.

What happens in the pancreas gland?

Produces insulin which regulates blood glucose levels.

Whats the difference between nerves and hormones?

Nerves :

• very FAST action

• Short-lasting effects

• Acts on a precise area

Hormones :

• SLOWER action

• Long lasting effects

• Acts in a more general way

Where is the pituitary gland, pancreas, thyroid, adrenal gland, ovary and testes found?

What is blood glucose monitored and controlled by?

The pancreas.

What happens when the blood glucose concentration is too high?

What happens when the blood glucose concentration is too low?

The pancreas releases glucagon → liver and muscle cells convert glycogen into glucose

Explain how insulin controls blood glucose (sugar) levels in the body.

Eating foods with carbohydrates puts glucose (sugar) into the blood from the gut.

cells use glucose for respiration

What are diabetes?

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

What are type 1 diabetes and how are they treated?

Type 1 diabetes is when the pancreas produces little to no insulin. The lack of insulin leads to uncontrolled high blood glucose levels.

Treated with insulin injections throughout the day.

The amount of insulin injected deoends on the persons diet and how active they are.

What are type 2 diabetes and how are they treated?

When the body cells no longer reacts to insulin produced by the pancreas.

Obesity is a risk factor for type 2 diabetes.

Treated by eating a carbohydrate-controlled diet and getting regular excercise.

What happens during puberty?

Your body starts releasing sex hormones that cause secondary sex characteristics to develop and causes eggs to mature in women.