Ch14 Notes

1. 14 - Coordination and
Excretion

2. Objectives
 Describe a nerve impulse as an electrical signal that passes along
nerve cells called neurones.
 Describe the human nervous system in terms of:
o the central nervous system consisting of brain and spinal cord
o the peripheral nervous system
o coordination and regulation of body functions.
 Distinguish between voluntary and involuntary actions.
 Identify motor (effector), relay (connector) and sensory neurones
from diagrams.

3. Human Nervous
System
 The human nervous system consists of the:
o central nervous system (CNS) - the brain
and the spinal cord
o peripheral nervous system (PNS) - all of
the nerves in the body
 It allows us to make sense of our surroundings
and respond to them and to coordinate and
regulate body functions

4. Nerves
 Information is sent through the
nervous system as nerve
impulses - electrical signals that
pass along nerve cells known
as neurones
 A bundle of neurones is known as
a nerve

5. Basic Structure of Neurone

6. Structure of Neurones
 Neurones have a long fibre (axon)
 This means that less time is wasted transferring the impulse from one cell to
another
 The axon is insulated by a fatty sheath with small uninsulated sections along it (called
nodes)
 This means that the electrical impulse does not travel down the whole axon,
but jumps from one node to the next
 Their cell body contains many extensions called dendrites
 This means they can connect to many other neurones and receive impulses from
them, forming a network for easy communication

7. Types of Neurons
 There are three main types of neurone: sensory, relay and motor
o Sensory neurones carry impulses from sense organs to the CNS (brain or
spinal cord)
o Relay neurones are found inside the CNS and connect sensory and motor
neurones
o Motor neurones carry impulses from the CNS to effectors (muscles or glands)

10. Voluntary & Involuntary Responses
 A voluntary response is one where you make a conscious decision to
carry out a particular action therefore it starts with your brain
 An involuntary (or reflex) response does not involve the brain as the
coordinator of the reaction and you are not aware you have
completed it until after you have carried it out
 Involuntary actions are usually ones which are essential to basic
survival and are rapid, whereas voluntary responses often take
longer as we consider what the response might be before doing it