Sense And Control

Front 1

Describe the stimulus response mechanism

Back 1

Step 1: Detecting the stimulus
This happens when a sense receptors is stimulated.

These are specialised areas or cells that are sensitive to a change in the environment such as a change in temperature, light, pressure, torch, sound etc.

Your body contains receptors to detect all these stimuli


Step 2: Effector
The message is then sent to an effector – an organ, land or muscle.


Step 3: Response
The effector then causes a response.

A response could be anything from an increase heartbeat to a rush of adrenalin. It could be a surge of tears, or the feeling of fear.

Front 2

Central Nervous System

Back 2

Is made up of the brain and spinal cord.

It acts as the control centre, receiving messages from all parts of the body.

Examines the information received, and then sends out messages instructing different parts of the body about what they are to do.

Front 3

Peripheral Nervous System

Back 3

Is made up of sensory receptors and nerves.

Continually inform the CNS of changing conditions, and transmit the decisions made by the CNS back to the effector organs.

Front 4

Describe a simple reflex response mechanism

Back 4

Are fast, occurring automatically and without thinking.

They use a pathway called the reflex arc made up of only a few neurons. The brain is not directly involved.

Example is blinking, sweating shivering.

Front 5

Identify the structure and function of a neuron

Back 5

Messages are passed through the system by nerve cells called neurons.

These are specialised cells that transmit and receive messages in the form of electrical impulse.

The information that is carried by electrical impulses travels at speeds between one and 100 meter per second.

A neuron has the features of any cell found in an animal. It has a nucleus, cytoplasm and cell membrane, but it also has other specialised parts.

Around the cell are dendrites, which are small threads, which make contact with other cells and receive information from them.

One long thread, which is an axon, carries information away from the cell. Axons are often encased in a white fatty substance called myelin.

Myelin insulates the axon like the plastic coating on an electrical wire, enabling messages to pass more quickly along the axon.

Neurons are grouped together in bundles called nerves, and is like smaller wires bounded together.

Front 6

Connecting Neuron

Back 6

Connecting neuron transfer electrical messages within the CNS

Front 7

Motor Neuron

Back 7

Motor neuron transfer messages from the CNS to effector organs such as muscles.

Front 8

Sensory Neurons

Back 8

Sensory neuron have specialised endings sensitive only to stimuli such as heat and light.

These form part of the body’s larger sense organs (eyes, ears etc.), which function by collecting different energy forms.

The sensory neuron then converts this energy into an electrical impulse.

Front 9

The synapse and neurotransmitters

Back 9

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Between neurons are small gaps called synapses.
Messages cross these synapses, but not as electrical impulses. Instead special compounds called neurotransmitters carry the message chemically.

When an impulse reaches a synapse, neurotransmitters are released and quickly moved across the gap. They move to sites on the other side restarting the electrical impulse.

The neurotransmitter is then broken down so new messages can be received.

Front 10

Types of neurotransmitters

Back 10

Noradrenalin – Is associated with alertness

Dopamine – Is associated with emotions.

Drugs such as cocaine, amphetamines and ecstasy increase production of these neurotransmitters.

The result is an increased state of alertness and heightened emotions, along with high blood pressure, irritability and later depression and insomnia.

Front 11

Multiple Sclerosis

Back 11

A disease that breaks down patches of myelin along neurons in the CNS.

The affected areas cannot conduct impulses so some messages from the brain to the muscles are lost.

Common symptoms are loss of coordination, tremors, vision difficulties etc.

The cause is a mystery. But evidence shows that a measles-like virus may be responsible in those who are genetically susceptible.

This disease is incurable as neurons cannot rebuild or be replaced.

Front 12

Spinal Injury cords

Back 12

Occurs if the spinal cord is broken, crushed or weaken.

If it is disconnected completely, then messages from the brain cannot get past to the organs and muscles below. This results in paralysis.

The extent of the injury is very dependent on where the break is, More function is lost the higher is break is.

Front 13

Spina Bifida

Back 13

A genetic condition in which some of the vertebrae are not completely formed, exposing parts of the spinal cord.

These parts have limited protection and usually do not develop completely.

Some people do not experience problems but others experience loss of nervous function.

Front 14

Protecting the Nervous System

Back 14

The spinal cord is protected by the spine (backbone)

The brain is protected by the skull.

Both the brain and spinal cord has a fluid around called cerebrospinal fluid to cushion them against shock.

Front 15

Brain Damage

Back 15

The brain receives 20% of the body’s blood and uses 20% of its oxygen.

Consciousness is lot rapidly and irreversible damage occurs within minutes if the blood flow to the brain is interrupted.

The most common form is a stroke, where the part of the brain is deprived of blood. This can happen when a blood vessel bursts in the brain or when a blood clot blocks a vessel.

Front 16

Brain

Back 16

The brain has three main parts: the cerebrum, cerebellum and medulla.

The brain is divided into two hemispheres. The right is responsible for artistic and musical ability, intuition and perception. The left takes care of language, learning mathematics and logical thinking.

The sensory areas are specialised regions that receive and interpret impulses from sense organs.

Front 17

Cerebrum

Back 17

A mass of wrinkled tissue that makes up 90% of the brain.

It is responsible for complex thoughts, the senses, muscle control, memory and thinking.

Front 18

Cerebellum

Back 18

The ‘base’ of the brain.

It controls complex muscular movements like cycling, walking and running.

Front 19

Medulla

Back 19

The ‘stem’ of the brain.

It controls vital activities that do not require conscious thought, like breathing and heartbeat.

Front 20

Spinal Cord

Back 20

A bundle of nerves running the length of the spine.

They transmit messages between the brain and the PNS, and control some actions that do not require thinking.

Front 21

Endocrine System

Back 21

The endocrine system uses chemical messages called hormones to transfer information around the body.

The endocrine system responses to a stimulus. The response tends to be slow, and over a longer period of time compared to the nervous system

Front 22

Hormone

Back 22

Although the endocrine glands work together they are not controlled from one central location like the nervous system

Are produced by the endocrine glands

Hormones regulate functions like growth and development, water balance, sexual reproduction and the rate of chemical reactions in cells.

Front 23

How hormone works

Back 23

Hormones travel to all parts of the body but only particular target cells respond to a particular hormone.

Hormones have a specific shape that fits chemically into a receptor on the membrane of the target cell like pieces of jigsaw.

This way hormones target the right cell with all the other being blocked.

The bonding of the hormone to the receptor start changes in the cells activities.

Hormones are secreted In very small quantities, making them difficult to detect.

Front 24

Pituitary Gland

Back 24

Produces the hormone:

Human growth hormone (HGH), which controls cell growth and development

Antidiuretic hormone (ADH), which controls water balance.
Also stimulates other glands to release their hormones.

Front 25

Thryiod

Back 25

Produces the hormone thyroxin which controls the rate of chemical reactions in cells.

Front 26

Pancreas

Back 26

Produces the hormones insulin and glucagon which both control blood glucose levels.

Front 27

Adrenal

Back 27

Produces the hormone adrenalin in readiness for flight or fight.

Front 28

Ovaries

Back 28

Produces the hormone:

· Oestrogen, which controls female sexual development and the menstrual cycle
· Progesterone, which controls the ovary and uterus in pregnancy.

Front 29

Testes

Back 29

Produce the hormone testosterone which controls male sexual development and sexual activity.

Front 30

Why hormones

Back 30

The endocrine system acts more slowly, taking minutes, hours or days for the level of a hormone in the blood to reach its peak.

This can be beneficial, as not all responses need to be fast.

When a hormone affects a cell, the response is usually long lasting.

If the hormone acted as quickly as the nervous system then a continuous supply would be needed to keep long-term responses going.

Front 31

The need for bodily co-ordination

Back 31

The body needs coordination in order to properly function

The central nervous system controls and coordinates all parts of your body

It is the most complex and least understood of all body systems.

Front 32

Damage to endocrine system

Back 32

Diabetes type 1: those who have defective pancreas and high blood glucose levels as a result of the pancreas not producing enough insulin and can be treated will a daily insulin injection

Diabetes type 2: those who do not produce enough insulin or have cells that do not respond correctly to insulin and treatment involves a special diet, an exercise program, use of drugs and possibly insulin injections.