Transcript Unit10 Nervous Wk 1

Gland, Hormone, Impulse, Nervous system, Effector, Stimulus,
Receptor, Neurone, Synapse
CONTROL SYSTEMS
There are two main control systems
(communication systems) in your
body.
1. Nervous system – a system of
electrical impulses organized into 2
main sections
2. Endocrine system – a system of
glands that release signalling
chemicals, or hormones
Central or CNS: spinal cord and brain;
functions to coordinate all actions of
the body
Peripheral or PNS: body’s nerves;
functions to connect the CNS to the
rest of the body through neurons.
• PNS is further divided into
– somatic or SNS: voluntary control of
body movements and is made up of
all neurons, sense organs, skin,
skeletal muscles
– Autonomic or ANS: involuntary
control of body movements like
reflex & controls such things as
heart rate, body temp, digestion etc.
PNS is further divided into
– somatic or SNS: voluntary control of body
movements and is made up of all neurons, sense
organs, skin, skeletal muscles
– Autonomic or ANS:
involuntary control of body
movements such as reflex and controls such things as
heart rate, body temperature, digestion etc.
1. The ANS is further divided into
» Parasympathetic nervous system
works in actions that do not require a
fast response (rest and digest
response)
» Sympathetic nervous system
works in actions that do require a fast
response (fight or fight response)
Say what?
NERVOUS SYSTEM
CNS
Nervous system releases electrical
impulses that are quick but the
effects are short lived and it involves
the CNS (either just spinal cord or
both spinal cord and brain) messages
are carried by neurones
PNS
ANS
Parasympathetic
SNS
Sympathetic
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 coordinates the bodies response.
Parts of the nervous system
For example;
If you smell something burning…
• Your nose (receptor) detects the
stimulus (smell)
• Nerve fibres send the message to the
brain
• Your brain then sends a message to
move your body away or to put out the
fire!
SIMPLE RIGHT!
Lets look at some bits more
closely
RECEPTORS
• Receptors are sensors on the body that detect stimuli
• They convert stimuli into electrical signals (messages)
called impulses.
EFFECTORS
An effector is any part of the body that produces the
response.
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
(neurons) that pass on electrical signals
(impulses) to the brain.
• From the brain, nerve fibres send impulses to
effectors (muscles).
NEURONS
3 types of neurons
1. Sensory neuron – carries impulses from the
receptors to the spinal cord.
2. Relay Neuron – carries impulses to and from
the spinal cord and the brain
3. Motor Neuron – carries impulses from the
brain to the effector
SYNAPSES
Where two neurons meet, there is a tiny
gap called a synapse.
Signals cross this gap using chemicals.
One neuron releases the chemical into
the gap.
The chemical diffuses across the gap and
makes the next neuron transmit an
electrical signal.
ttp://www.bbc.co.uk/schools/gcsebitesize/science/aqa/
human/thenervoussystemrev2.shtml
Watch this video on synahpses then draw a flow chart of the process
The stick drop test!
METHOD:
1. Working in pairs, one student holds a metre rule vertically at the zero end,
between the thumb and forefinger of another student, so that the 50 cm
mark is level with the top of the forefinger.
2. Without warning, the first student drops the rule and the second student
attempts to catch it between the thumb and forefinger, noting the distance on
the ruler just above the forefinger.
3. Repeat several times, so that an average can be calculated.
4. Then change around so that everyone gets a turn.
5. Create a data table to record your results.
CONCLUSION AND DISCUSSION:
Do you think the measurements were accurate? Explain why/why
Identify the parts of the body involved. What senses are being used? Can we
train ourselves to react more quickly? Does practice make perfect?
Can we alter reflex actions? – think of a situations where it is possible to alter
the automatic response (not dropping a hot object, deliberately breathing
more slowly, etc.). Are there some reflex actions over which we have no
control? Name some examples.
REFLEX ARC
•
When your body needs to react to something
very quickly (to protect itself) it uses a reflex
arc (spinal reflex).
• Instead of sending impulses from the receptor
Spinal cord
brain
spinal cord
effector
• It sends impulses from the receptor
spinal cord
effector…Yup it bypasses the
brain!
GCSE Biology 1A
Human Biology
Questions
How are impulses sent through nerve cells?
What is a synapse?
What are two types of effectors?
ANSWERS
•
Electrical impulses along neurones,
chemical (neurotransmitters) across the
synapse.
• The microscopic gap between two
neurones.
• By chemicals called neurotransmitters.
• To pass the impulse onto the correct
motor neurone.
• Glands or muscle that produce the
effect or make a response.
REFLEX ACTION
The way the iris in
our eye adjusts
the size of the
pupil in response
to bright or dim
light is also a
reflex action.
In bright light In dim light
•Circular muscles
of the iris contract.
•Radial muscles of
the iris relax.
•Less light enters
the eye through
the contracted
pupil.
•Radial muscles
of the iris
contract.
•Circular
muscles of the
iris relax.
•More light
enters the eye
through the
dilated pupil.
Inside the eye
cornea
protects eye surface and
focuses light rays
suspensory ligaments
hold lens in place
retina
senses light
lens
focuses light
on retina
iris
regulates amount
of light entering eye
ciliary muscles
change shape of the lens
optic nerve
transmits impulses to
the brain