Year 9 Biology Mini quiz 1 (neurons)

What are the 5 senses?

Sight, hearing, taste, touch, smell.

Stimulus

any information that the body receives that causes it to respond

Receptor

specialized cells that detect stimuli and convert them into electrical signals

Sight

Senses light

How does sight work?

The different types of photoreceptor cells at the back of the eyes transform the light into nerve signals for the brain.

Hearing

Sensing sound

How does hearing work?

• This causes the eardrums to vibrate.

• The vibrations are transferred along the bones of the middle ear – the smallest bones in your body.

• The vibrations enter the cochlea to be converted into nerve impulses.

Tasting

Sensing Flavour

How does tasting work?

• Taste buds contain special receptor cells that react to chemicals in foods.

• These chemical receptors can recognize basic kinds of taste molecules, such as sweet, salty, sour, bitter, and umami (savory).

Smelling

Sensing odour

How does smelling work?

• The receptors in the nostrils detect chemicals in the air.

• The receptors send messages to the brain.

• The brain interprets the messages and tells us what we are smelling.

• Smell is closely linked to taste.

Touch

Sensing pressure, temperature and pain.

How does touch work?

• The inner layer of skin, called the dermis, contains many nerve endings.

• These nerve endings can detect heat, cold, pressure, and pain.

Neuron

A nerve cell

Cell body

The main part of a cell that contains the nucleus/genetic material.

Axon

The part of a neuron (nerve cell) that carries an electrical message away from the cell body to the synapse.

Myelin sheath

A fatty layer that covers the axon of a nerve cell.

Dendrite

The part of a neuron (nerve cell) that receives a message and sends it to the cell body.

Neurotransmitter

A chemical messenger that crosses the synapse between the axon of one neuron and the dendrite of another neuron.

Synapse

A small gap between two neurons that must be crossed by neurotransmitters.

What does a neuron do?

A neuron carries information as an electrical impulse.

(Scientists believe that we may have up to 100 billion neurons in our bodies, connected in paths called nerves.)

What is a neuron?

A neuron carries information as an electrical impulse.

Approximatley how many neurons are in the human body?

Scientists believe that we may have up to 100 billion neurons in our bodies, connected in paths called nerves.

What does an axon do?

An axon carries electrical nerve impulses away from the cell body

What are synaptic terminals?

Synaptic terminals are small bulbs at the end of an axon where electrical impulses are changed into chemical signals.

What is a neurotransmitter?

A neurotransmitter is a chemical messenger thatt carries signals acorss a synapse from one neuron to another

What happens to an electrical impulse at the synpase?

It is converted into a chemical signal (a neurotransmitter), crosses the synapse, then is converted back into an electrical signal in the next neuron.

What do dendrites do?

Dendrites receive chemical messages from other neurons and pass them to the cell body.

What is the myelin sheath?

The myelin sheath is a fatty layer that surrounds the axon and insulates it.

Why is the myelin sheath important?

It speeds up nerve impulses by insulating the axon and helping the electrical signal travel faster.

How are nerves similar to electrical wires?

Both carry electrical signals and require insulation to work efficiently.

How long can some axons be?

Axons connecting the spinal cord to the foot can be up to 1 metre long.

Interneurons:

They sensory and motor neurons, as well as other interneurons.

Sensory neurons

They collect information from the internal environment or the outside world and send the information they to the central nervous system for processing.

Motor neurons

They carry messages from the central nervous system to muscle cells  throughout the body, which then carry out the response.

Reflex

An involuntary and nearly instantaneous movement in response to a stimulus (e.g. that the object is hot)

Stimulus Pathway

Stimulus → Receptor → Control centre (via sensory neuron) → Effector (via motor neuron) → Response

Central nervous system

Control centre of the body

What are the 2 main parts of the central nervous system?

The brain and the spinal chord

Peripheral nervous system

A large system made up of all the nerves outside the central nervous system it carries information to and from the central nervous system to the rest of the body (e.g such as the limbs and organs.)

What are the 2 parts of the peripheral nervouse system?

• Somatic nervous system controls voluntary skeletal muscle movements, such as walking.

• Autonomic nervous system controls involuntary actions, which happen without our conscious control. This includes heartbeat, digestion, respiration, salivation and perspiration. 

What are the 2 divisions of the autonomic nervous system?

• The parasympathetic division slows down the heart rate or constricts pupils. 

• The sympathetic division speeds up the heart rate or dilates pupils. 

What are the things that can go wrong with the nervous system?

Paraplegia, Slipped disc, Multiple sclerosis, Motor Neurone Disease, Alzherimer’s disease

What is Paraplegia?

When the spinal cord is damaged, the messages from the neurons below the level of injury can no longer travel to the brain.

What is a Slipped disc?

If a disc becomes weak and puts pressure on the nerves entering or leaving the spinal cord, this will cause pain or numbness along the nerve.

What is Multiple Sclerosis?

In multiple sclerosis, the immune system mistakenly recognises myelin sheath cells as dangerous, and attacks and destroys them.

What is Motor Neurone Disease?

• The neurons that send messages to the muscles become weak and eventually lose function.

• Scientists do not know what causes the motor neurons to lose function.

What is Alzheimer’s Disease

• Caused by progressive damage to the neurons in the brain. This gradually affects memory, and the ability to reason or plan and carry out everyday activities.

• The cause of Alzheimer’s disease is not known.