1. The Body Control Systems
Strathcona BGGS
Yr 9 Science 2012

2. 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

3. In this Unit We will look at two systems involved in the
control of the Human Body:
1. The Nervous System 2. The Endocrine System
 Consists of tissues that  Consists of glands that produce
conduct electrical signals chemical messages (Hormones).
(nerve impulses)
 Hormones travel through the
 Impulses travel at high speed blood stream.
 Generally brings about fast,  Generally brings about slow, long
short term change term change

4. The Nervous System

5. 1.The Nervous System
It 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)

6.  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.

7. Axons & Dendrites
Axon Dendrites
 Take information away from  Bring information to the cell
the cell body body
 Smooth Surface  Rough Surface (dendritic
spines)
 Generally only 1 axon per
cell  Usually many dendrites per
cell
 No ribosomes
 Have ribosomes
 Can have myelin
 No myelin insulation
 Branch further from the cell
body  Branch near the cell body

12.  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.

13.  Our Sensory Neurons receive or
detect information from specialised
cells.
 This is then sent to the CNS for
processing. CNS
 From the CNS commands are sent
to Motor Neurons in the PNS
which pass them on to muscles
and glands. Sensory
 NB: Nerves only carry signals in one direction Neurons
Motor
Neurons
PNS

14.  Synapses:
 a small gap separating
neurons.
 Signals travel through a
nerve as an electrical signal
but across synapse as a
chemical signal or
neurotransmitter.

15. 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

16. The Reflex Arc
A 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.

17. 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.

18. Reference: Work to be completed:
Science Links 3  Textbook:
7.1 Nerves and reflex Action  p 193 – 1, 2 & 4
pp191 – 196  p 196 – 1, 3-4, 6-8, 10
 Homework Book:
 p 94 Activity 8.1
 pp 95-6 Activity 8.2