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The Nervous System and Reflex Arc
Name:__________
Parts of the Nervous System
The NERVOUS SYSTEM is made up of three main parts;



THE BRAIN
THE SPINAL CORD
NERVE FIBRES
It detects STIMULI such as light, sounds, temperature, pressure, pain and co-ordinates the bodies response.
What are the 5 sense organs and what do they sense?
Organs
Stimulus it detects…
SKIN (the largest in the body)
Touch
Nose
Smell (Chemicals)
Eyes
Light/Colour
Tongue
Taste (Chemicals)
Sound (Vibrations)
Ears
You put your hand near a flame. What is happening?
STIMULUS
RECEPTOR
SENSORY NEURONE
COORDINATOR (CNS)
RELAY NEURONE
MOTOR NEURONE
EFFECTOR (MUSCLE)
RESPONSE
Your body’s SENSE organs contain NERVE cells.
SENSORY neurons detect CHANGES/STIMULI in the environment and send messages called NERVE
IMPULSES along nerves to the BRAIN and SPINAL CORD.
An EFFECTOR is any part of the body that produces the RESPONSE
Effectors: Here are some examples of effectors:
•
a muscle contracting to move the arm
•
a muscle squeezing saliva from the salivary gland
•
a GLAND releasing a HORMONE. into the blood
Nerve Fibres
•
Nerve fibres are bundles of nerve cells (NEURONES) that pass on electrical signals (IMPULSES) to the brain.
•
From the brain, nerve fibres send impulses to EFFECTORS (muscles/glands).
There are three types of neruones
1.
Sensory neurons 2. Relay neurons 3. Motor neurones
SENSE
ORGAN/
RECEPTOR
Senses stimuli
from our
surroundings.
VOLUNTARY
SENSORY NEURONE
Takes impulses from the sense
organ to the relay neurone.
SPINAL
CORD
Where the
relay
neurones
are found.
BRAIN
Receives
impulses from
the spinal
cord and
sends out new
impulses.
RELAY
NEURONE
Takes
impulses to the
brain and from
the brain.
INVOLUNTARY
MOTOR
NEURONE
Takes impulses
from the relay
neurone to the
effector.
EFFECTOR
The muscle
that receives
the impulse
from motor
neurone.
Reflex arcs
Automatic responses to stimuli are called REFLEX ACTIONS.
A reflex response is RAPID and its function is PROTECTION
The spinal cord mediates REFLEX RESPONSES to some sensory impulses DIRECTLY ie. without going to the brain. This
makes it much FASTER
The messages pass through a REFLEX ARC
1.
We need reflex actions because:
a) They conserve energy for your body
b) They are required for survival
c) They ensure all nerves in the body are used equally
2. You step on a plug- which of the sentences below is accurate?
a) light receptors in the eyes are allowing you to feel the plug.
b) temperature receptors in the skin allow you to feel the plug.
4.
You burn your hand on a hot plate- which of the
following order of events is correct?
a) receptor-->sensory neurone-->relay neurone-->motor
neurone--> effector
b) receptor--> motor neurone-->relay neurone-->sensory
neurone-->effector
c) receptor-->sensory neurone-->CNS->motor neurone-->effector
d) receptor-->sensory neurone-->CNS-->relay neurone->effector
c) pressure receptors in the skin allow you to feel the plug.
d) pressure receptors in the mouth allow you to feel the plug.
3. You see a football and kick it- which of the following order of events is correct:
a) receptor--> motor neurone--> brain--> sensory neurone--> effector
b) receptor--> sensory neurone--> relay neurone-->motor neurone--> effector
c) receptor-->sensory neurone-->brain-->motor neurone--> effector
d) receptor-->sensory neurone-->motor neurone--> effector