B10 - The Human Nervous System

Question 1

What is the internal environment?

Answer 1

The conditions inside your body.

Question 2

What can happen if the internal environment keeps changing?

Answer 2

Your organs cannot work properly.

Question 3

Many of the processes that go on inside your body aim to ….

Answer 3

Keep everything as constant as possible.

Question 4

Ways in which the internal environment is kept constant?

Answer 4

Keeping the body as a whole constant, including the regulation of the internal conditions of cells to maintain optimum conditions for functioning, in response to internal and external changes.

Question 5

This balancing act is called…..?

Answer 5

Homeostasis

Question 6

Why is it important to respond to changes in the internal or external environment?

Answer 6

To maintain optimum conditions for the cellular enzymes. This is because enzymes control all the functions of a cell, as enzymes only work at their best in specific comditions of temperature and pH.

Question 7

Internal conditions that are controlled include:

Answer 7

Body temperature

The water content of the body

Blood glucose concentration

Question 8

Examples of body responses

Answer 8

When you excercise your muscles get hotter
When you have eaten a meal, your blood sugar levels go up
In hot weather you lose water and salt through sweating

Question 9

What do automatic systems do?

Answer 9

They help detect changes and responding to them. These automatic systems include nervous responses in your nervous system and chemical responses in your hormone system. They also involve many of your body organs.

Question 10

Key features all control systems need to function:

Answer 10

Receptors
Coordination centres
Effectors

Question 11

What are receptors?

Answer 11

Cells that detect changes in the internal or external environment. These changes are known as stimuli. Receptors may be part of the nervous or the hormonal control systems of the body.

Question 12

What are coordination centres?

Answer 12

Areas that receive and process the information from the receptors. They send out signals and coordinate the response of the body. They include the brain, which acts as a coordination centre for both the nervous system and parts of the hormonal system, the spinal cord, and some prgans such as the pancreas.

Question 13

What are effectors?

Answer 13

Muscles or glands that bring about responses to the stimulus that has been received. These responses restore conditions in the body to the optimum levels.

Question 14

Your nervous system enables you to?

Answer 14

React to your surroundings and coordinate your behaviour.

Question 15

What does the nervous system carrya nd what speed do they travel at?

Answer 15

Carries electrical signals(impulses) that travel fast -between 1 and 120 metres per second. This means that you can react to changes in your surroundings very quickly.

Question 16

What are changes or stimuli picked up by?

Answer 16

Cells called receptors

Question 17

Structure and location of receptor cells?

Answer 17

They are similar to most animal cells and have a nucleus, cytoplasm, and a cell membrane. These receptors are usually found clustered together in special sense organs, like your eyes and skin. You have many different types of sensory receptor.

Question 18

Some male moths have receptors so sensitive, they can…?

Answer 18

Detect the scent of a female several kilometres away and follow the scent trail to find her.

Question 19

Neurones are usually found in?

Answer 19

Bundles of hundreds or even thousands of neurones known as nerves.

Question 20

What is the central nervous system (CNS) made up of?

Answer 20

The brain and the spinal cord.

Question 21

What are sensory neurones?

Answer 21

The cells that carry impulses from your sense organs to your CNS.

Question 22

What are motor neurone cells?

Answer 22

Special cells that carry information from the CNS to these rest of your body -the effectors.

Question 23

Effectors may be :

Answer 23

Muscles or glands

Question 24

How do muscles respond to the arrival of impulses?

Answer 24

By contracting

Question 25

How do glands respond to the arrival of impulses?

Answer 25

By releasing (secreting) chemical substances.

Question 26

Examples of effectors responding to impulses (two):

Answer 26

Your salivary glands produce and release extra saliva when you smell food cooking.

Your pancreas releases the hormone insulin when your blood sugar levels go up after a meal.

Question 27

How does your nervous system work?

Answer 27

Once a sensory receptor detects a stimulus, the receptor sends an impulse along a sensory neurone, carrying information about a change in the environment to the coordinator (CNS). Once all the incoming information has been processed, the coordinator sends impulses down motor neurones. These motor impulses stimulate the effectors to bring about the responses needed in any particular situation.

Question 28

Two simple methods to investigate how quickly nerve impulses travel in your body?

Answer 28

Use the ruler drop test or digital sensors to measure how quickly you react to a visual stimulus

Stand in a circle holding hands with your eyes closed and measure how long it takes a hand-squeeze to pass around the circle.

Question 29

Why are reflexes important?

Answer 29

They help us to avoid danger or harm because they happen so fast. There are also lots of reflexes that take care of your basic bodily functions. These include breathing and moving food through your digestive system.

Question 30

Key ideas about reflexes?

Answer 30

They are automatic and rapid. They do not involve the conscious part of your brain.

Question 31

Simple reflex actions such as the pain withdrawal reflex involve just 3 types of neuron:

Answer 31

Sensory neurons
Motor neurons
Relay neurones- These connect a sensory and motor neuron, and are found in the CNS.

Question 32

How do reflexes work?

Answer 32

An electrical impulse passes from the receptor along the sensory neurone to the CNS. It then passes along a relay neurone (usually in the spinal cord) and straight back along the motor neurone. From there, the impulse arrives at the effector organ. The effector organ will be a muscle or a gland. We call this pathway a reflex arc.

Question 33

Key point about a reflex arc

Answer 33

The impulse bypasses the concious areas of your brain. The result is that the time between the stimulus and the reflex action is as short as possible.

Question 34

How do synapses work?

Answer 34

Because your neurones aren’t joined directly to each other, there are junctions between them called synapses, which form physical gaps between the neurones. The electrical impulses travelling along your neurones have to cross these synapses. The diffusion of the chemical across the synapse is slower than the electrical impulse in the neurones, but it makes it possible for the impulse to cross the gap between them.

Question 35

Response if you touched a hot object:

Answer 35

When you touch the object, the receptor in your skin is stimulated. An electrical impulse from a receptor passes along a sensory neurone to the CNS - in this case, the spinal cord. When an impulse from the sensory neurone areives at the synapse with a relay neurone, a chemical is released. This chemical diffuses across the synapse to the relay neurone, where it sets off a new electrical impulse that travels along the relay neurone. When the impulse reaches the synapse between the relay neurone and a motor neurone returning to the arm, another chemical is released. Again, the chemical diffuses across the synapse and starts a new electrical impulse travelling down the motor neurone to the effector. When the impulse reaches the effector organ, it is stimulated to respond. In this example, the impulses arrive in the muscles of the arm, causing them to contract. This action moves the hand rapidly away from the source of the pain. If the effector organ is a gland, it will respond by releasing (secreting) chemical substances.

Question 36

The reflex pathway is not very different from a normal concious action. However, …

Answer 36

in a reflex action, the coordinator is a relay neurone either in the spinal cord, or in the unconcious areas of the brain. An impulse also travels up the spinal cord to the consciousnareas of your brain, so you know about the reflex action, but onky after it has happened.