The Body Control SystemsStrathcona BGGS

Yr 9 Science 2013

The Body Control Systems

You are made up of somewhere between 50 000 000 000 000 – 75 000 000 000 000 (50 – 75 Trillion cells1.

To maintain and control all of these we have a number of systems this year we will look at 2 of these.

1. Asimov, Isaac, The Human Body, New Rev Ed. p 79

In this Unit We will look at two systems involved in the control of the Human Body:

1. The Nervous System

Consists of tissues that conduct electrical signals (nerve impulses)

Impulses travel at high speed

Generally brings about fast, short term change

2. The Endocrine System

Consists of glands that produce chemical messages (Hormones).

Hormones travel through the blood stream.

Generally brings about slow, long term change

The Nervous System

1.The Nervous SystemIt is our interface to the outside

world.

Is made up of 2 parts:a) The Central Nervous System

(CNS) which is made up of the Brain and Spinal Cord.

b)The Peripheral Nervous System (PNS)

Neurons are the cells that carry nerve signals around the body

All Neurons have the same basic structures: Dendrites: (from the Greek

meaning tree) branched extension of nerve cells that receive nerve impulses from other cells.

Cell Body (including a nucleus) Axon: a long, slender projection

that conducts electrical impulses away from the neuron's cell body.

NB: Neurons are some of the oldest and longest cells in your body. You have many of the same neurons for your whole life.

Axons & DendritesAxon

Take information away from the cell body

Smooth Surface

Generally only 1 axon per cell

No ribosomes

Can have myelin

Branch further from the cell body

Dendrites

Bring information to the cell body

Rough Surface (dendritic spines)

Usually many dendrites per cell

Have ribosomes

No myelin insulation

Branch near the cell body

Is made up of 4 different types of neurons; we will deal with 3 :1. Brain Cells – These process

information.

2. Sensory Neurons – These detect the outside world and send signals to the CNS

3. Motor Neurons – These receive signals from the CNS and pass them on to muscles and glands.

Our Sensory Neurons receive or detect information from specialised cells.

This is then sent to the CNS for processing.

From the CNS commands are sent to Motor Neurons in the PNS which pass them on to muscles and glands.

NB: Nerves only carry signals in one direction

CNS

Sensory

Neurons

Motor Neuron

s

PNS

Synapses: a small gap separating

neurons.

Signals travel through a nerve as an electrical signal but across synapse as a chemical signal or neurotransmitter.

Stimulus - Response A Stimulus is any change in the environment

of the organism. The nervous system will then induce a response, which may be movement, speech, blinking etc. Advanced organisms have specialised sense

organs, which are designed to detect stimuli. These are often called receptors and are

sensitive to one stimuli (e.g. Skin to touch, eyes to light patterns)

A Response is how the organism reacts to the stimulus and results in a change in behaviour

Examples Stimulus: being cold - Response: move

into the sun Stimulus: Thirst - Response: Get a drink

The Reflex ArcA reflex is the simplest form of response to a stimulus.

In a reflex reaction, the response occurs before the message reaches the brain, or the message may not reach the brain at all.

The receptor cell sends an impulse through a sensory neuron to the spinal cord.

The message doesn’t go directly to the brain but to the cell body of motor neuron and then to the muscle.

The muscle contracts and the response is issued.

The brain may get the message soon after. In reflexes, the impulse is not related to stored information in the brain before the response.

The most common reflex is the knee jerk.

Remember:Information travels through the neurones as an

electrical impulse.

Nerve impulses travel in only one direction in a nerve fibre. (Dendrites Axon)

Information is passed between neurones as chemical messages.

Reference: Textbook:

P234 q 1-5, 6, 9, 10, 12-14,

Homework Book: p 82 7.1 The Nervous

systemp 83 7.2 Reflexesp 84 7.3 Reaction Time

Person Science 9

7.1 Nervous Control

pp225-6

pp228-31

Work to be completed: