The Human Nervous System

Question 1

The nervous system

Answer 1

The nervous system protects organisms from harm by responding to changes in the environment. It does this by coordinating communication between different parts of organisms.

Question 2

The brain

Answer 2

The brain is one of the components (parts) of the central nervous system (CNS).
The CNS coordinates the response of effectors. Effectors are muscles or glands that act in response to a change in the internal or external environment.

Question 3

The spinal cord

Answer 3

The spinal cord is the other component (part) of the CNS. It is also important in coordinating the response of effectors to changes in the environment.

Question 4

The neurones (nerve cells)

Answer 4

Neurones (nerve cells) carry electrical impulses (signals) between receptors, the central nervous system (CNS) and effectors.

Question 5

Synapses

Answer 5

At each junction of the reflex arc, there is a synapse. Synapses are gaps between neurones. Nerve impulses must travel across these gaps: The electrical impulse reaches the end of the neurone before the synapse.
This triggers the release of chemicals called neurotransmitters. The neurotransmitters diffuse (move down a concentration gradient) across the synapse. The neurotransmitters bind to receptors on the next neurone.
The presence of the neurotransmitter causes the production of an electrical impulse in the next neurone.

Question 6

At each junction of the reflex arc, there is a synapse

Answer 6

Synapses allow information to be passed from one neurone to another.

Question 7

Neurone Structure

Answer 7

Axons carry electrical impulses away from the cell body. Dendrites carry electrical impulses towards the cell body. Axons are covered in a layer called a myelin sheath. This insulates the neurone, so electrical impulses travel down it more quickly.

Question 8

Axons are covered in a layer

Answer 8

called a myelin sheath. This insulates the neurone, so electrical impulses travel down it more quickly.

Question 9

Axons are covered in a layer called a myelin sheath

Answer 9

This insulates the neurone, so electrical impulses travel down it more quickly.

Question 10

Reflex Actions

Answer 10

Reflex actions allow us to respond to dangerous situations rapidly and automatically. Reflex actions do not involve conscious thought. The nervous system responds to stimuli (events or things) via a reflex arc.

Question 11

Some examples of reflexes are:

Answer 11

Dropping hot objects, Sneezing, Blinking

Question 13

Reflex actions allow us to

Answer 13

respond to dangerous situations rapidly and automatically. For reflex actions, the nervous system responds to stimuli (events or things) via a reflex arc.

Question 14

Components of a Reflex Arc
The different parts of a reflex arc are: Stimulus

Answer 14

A stimulus can be any change in the environment to which the body needs to respond.
The stimulus is detected by a receptor.

Question 15

Components of a Reflex Arc
The different parts of a reflex arc are: Receptor

Answer 15

Receptors are found all over the body.
They detect the change in the environment and initiate (start) a signalling process within the body.
The signal is picked up by a neurone (nerve cell).

Question 16

Components of a Reflex Arc
The different parts of a reflex arc are: Neurones

Answer 16

There are three types of neurone (nerve cell):
The sensory neurone, which carries the signal in the form of an electrical impulse to the central nervous system (CNS). The relay neurone (in the CNS) relays the electrical impulse from the sensory neurone to the appropriate motor neurone. The motor neurone is another type of nerve cell that carries the electrical impulse from the CNS to an effector.

Question 17

Components of a Reflex Arc
The different parts of a reflex arc are: effector

Answer 17

An effector is a muscle or gland that brings about an action in response to the change in the internal or external environment.

Question 18

Components of a Reflex Arc
The different parts of a reflex arc are: response

Answer 18

Response
The response can be any action that helps the organism to avoid the harmful situation.

Question 19

Reflex Arc

Answer 19

The stimulus is detected by a receptor. The sensory neurone carries the signal, in the form of an electrical impulse, to the central nervous system (CNS). The motor neurone carries the electrical impulse from the CNS to an effector. An effector (a muscle or gland) brings about an action in response to the change in the internal or external environment.

Question 20

The Brain

Answer 20

The brain is a very complex organ that controls all conscious and unconscious thoughts in order to keep an organism alive.

Question 21

Brain function

Answer 21

Brain function
The brain is made up of millions of interconnecting neurones (nerve cells).
Different regions of the brain are responsible for coordinating (organising) different functions.

Question 22

Brain damage

Answer 22

The brain is delicate and complicated.
Therefore, the treatment of brain damage and brain disease is difficult.

Question 23

Parts of the Brain

Answer 23

The brain is made up of three main parts.

Question 24

Medulla oblongata

Answer 24

This part is responsible for unconscious activities (e.g. breathing and heartbeat).

Question 25

Cerebellum

Answer 25

This part is responsible for the muscle coordination. The cerebellum is important for movement, posture, balance and speech.

Question 26

Cerebral hemispheres

Answer 26

This part is responsible for conscious thought (e.g. memory, language and intelligence).

Question 27

In the brain, the cerebellum is

Answer 27

responsible for muscle coordination. The cerebral hemispheres are responsible for conscious thought. The medulla oblongata is responsible for unconscious activities.

Question 28

Researching the Brain

Answer 28

Many areas of the brain cannot be accessed safely through surgery while people are alive. But neuroscientists (scientists who study the brain) have other ways to understand how the brain works.

Question 29

PET scans

Answer 29

These scans are used to look at how parts of the brain are functioning. Using radioactive glucose, the amount of glucose different parts of the brain are using up can be detected. An image of brain activity is then made

Question 30

Studying brain damage

Answer 30

By studying patients with brain damage, where part of their brain doesn’t function, neuroscientists have been able to link particular regions of the brain to particular functions.

Question 31

CT scanning

Answer 31

Lots of x-rays are taken of the brain, and a computer then builds a 3D image of the brain's structure. Different types of cells absorb different amounts of the x-rays. Brain tumours show up as white blotches.

Question 32

Researching the Brain

Answer 32

Neuroscientists (scientists who study the brain) have been working for many years to further understand how the brain works, using both CT and PET scanning and by studying the effects of brain damage.

Question 33

Brain Damage

Answer 33

Treating injuries or diseases in the brain or in other parts of the nervous system is very difficult.

Question 34

Spinal injuries

Answer 34

If the spinal cord is severed (cut), electrical impulses can no longer travel to the brain. Wires can partly re-connect the spinal cord, but this isn't very effective.

Question 35

Neurone damage

Answer 35

Neurones cannot be replaced like other cells in the body, so damage to these cells is often permanent and irreversible. Researchers are trying to find a way to make new neurones using stem cells.

Question 36

Brain tumours

Answer 36

Brain tumours are lumps of dividing cancer cells. They can block blood flow to other parts of the brain. These cancers can be treated with chemotherapy (using drugs), radiotherapy (using radiation) or brain surgery, but these also cause lots of damage to the body.