OCR Gateway GCSE Biology: B3.1 The Nervous System and B3.2 The Endocrine System

From Physics and Maths Tutor

What is the difference between the central nervous system and the peripheral nervous system?

The central nervous system is the brain and the spinal cord; the peripheral nervous system is every other part of the nervous system.

What is a stimulus?

A stimulus is a change in the environment.

What type of neurone connects a receptor to the CNS?

A sensory neurone.

What is an effector?

A part of the body that brings about the response to a stimulus, like a muscle or a gland.

What type of neurone connects the CNS to an effector?

A motor neurone.

Describe the reflex arc.

Stimulus detected by a receptor; impulse passed along sensory neurone to CNS; impulse passed along motor neurone to effector; effector brings about the response.

What is the cornea and what is its function?

The cornea is the transparent layer in front of the eye that protects the eye from damage.

What is the iris and what is its function?

The iris is the coloured ring around the pupil that controls its diameter.

What is the pupil and what is its function?

The pupil is the hole in the middle of the iris that lets light into the eye.

What is the optic nerve and what is its function?

The optic nerve is the nerve coming out the back of the eye that sends signals to the brain.

What is the function of the lens?

The lens focuses the light rays onto the retina.

What is the retina and what is its function?

The retina is the back part of the eye that converts visual stimuli into electrical impulses.

What do the ciliary body and suspensory ligaments do?

They control the shape of the lens (accommodation).

What defect in the eye causes short sightedness?

The lens focuses light rays in front of the retina, making far away objects appear blurry.

How is short sightedness corrected?

By wearing glasses that have concave lenses.

What defect in the eye causes long sightedness?

The lens focuses light behind the retina, making nearby objects appear blurry.

How is long sightedness corrected?

By wearing glasses that have convex lenses.

What is colour blindness?

It is an inherited condition where people find it difficult to tell the difference between colours, caused by a defect in the retina, and there is currently no cure.

Where is the cerebrum located and what is its function?

The cerebrum is located at the front of the brain and controls conscious functions, memory, and language.

Where is the cerebellum located and what is its function?

The cerebellum is located at the back bottom of the brain and controls muscular movement and balance.

Where is the medulla located and what is its function?

The medulla is located in the brainstem at the middle bottom and controls unconscious functions like heart rate and breathing.

What is the function of the hypothalamus?

It acts as the regulatory centre and controls body temperature, water content, and salt balance.

What is the function of the pituitary gland?

It releases hormones into the blood.

Give 2 reasons why it is difficult to investigate brain function.

Surgery is not risk-free; people with brain disorders may be unable to consent.

Why is it difficult to treat brain disorders?

The brain and spinal cord are very difficult to access; tissues in the CNS cannot regenerate; drugs cannot penetrate the blood-brain barrier.

What are hormones?

Hormones are chemical messengers that are secreted by glands of the endocrine system into the bloodstream.

What are the target cells?

Target cells are cells with the specific receptor for a hormone that produce an effect when the hormone binds.

What does the hormone thyroxine control in the body?

Thyroxine controls metabolic rate.

Describe thyroxine as a negative feedback system.

When the level of thyroxine decreases, the pituitary gland produces thyroid stimulating hormone (TSH) which causes the thyroid gland to produce more thyroxine. When the level of thyroxine increases, the pituitary gland produces less TSH.

When is adrenaline secreted?

During times of anxiety, fear or stress.

Give 3 effects of adrenaline in the body.

1. Increases heart and breathing rate. 2. Increases blood glucose concentration. 3. Dilates the pupils.

What does oestrogen do?

Oestrogen causes the uterus lining to thicken.

What hormone does oestrogen inhibit?

Oestrogen inhibits follicle stimulating hormone (FSH).

What does progesterone do?

Progesterone maintains the womb lining.

What hormone does progesterone inhibit?

Progesterone inhibits follicle stimulating hormone (FSH).

What does follicle stimulating hormone (FSH) do?

FSH stimulates the follicle to mature and release oestrogen.

What does luteinising hormone (LH) do?

A surge in LH causes the release of an egg from a follicle (ovulation).

How do oestrogen pills work to prevent pregnancy?

Oestrogen pills inhibit FSH which stops the egg from maturing.

How do progesterone pills work to prevent pregnancy?

Progesterone pills cause a sticky mucus to form at the cervix which prevents the sperm from fertilising the egg.

Give one advantage and one disadvantage of hormonal contraception.

Advantage - More than 99% effective. Disadvantage - It can cause side effects like weight gain.

Give one advantage and one disadvantage of condoms as non-hormonal contraception.

Advantage - 98% effective and prevents sexually transmitted diseases. Disadvantage - Condoms are only one-time use and they can break.

Describe how IVF is carried out.

1. The mother is given FSH. 2. Sperm from the father and eggs from the mother are collected. 3. The egg is fertilised in a laboratory and allowed to develop into an embryo. 4. The embryo is then put into the mother's uterus.

What hormone is given in female fertility drugs?

Follicle stimulating hormone (FSH).

What does auxin trigger?

Auxin triggers growth of the main stem of the plant and inhibits the growth of side shoots.

What is phototropism and which part of a plant is positively phototropic?

Phototropism is the growth of a plant towards a light source. The shoots are positively phototropic.

What is geotropism and which part of a plant is positively geotropic?

Geotropism is the growth of a plant towards the pull of gravity. The roots are positively geotropic.

How does auxin cause the shoots to grow towards the light source?

1. Auxin collects on the shaded side. 2. Auxin promotes cell growth. 3. The shoot curves towards the light.

What do gibberellins do?

1. Promote seed germination. 2. Increase the length between stem nodes. 3. Delays leaf shedding.

What does ethene cause when it is applied to plants?

It causes fruit ripening which is useful so that fruit can be transported long distances.

How do selective weedkillers work?

1. They contain auxin. 2. They work on some plants (weeds) and not others. 3. They cause the plant to grow too quickly which kills it.

What are parthenocarpic fruit?

Seedless fruit.