Nervous System
Your Nervous System is the most complicated and fragile system. It tells all your other systems what to do. The Nervous System carries messages to the brain.
How Your Nervous System Works
Your Nervous System helps you move. Your Nervous System wouldn’t work if you didn’t have the other systems. It is just the same the other way around, if you didn’t have your Nervous System you wouldn’t be able to move.
Organization of Nervous System
Nervous System
Central Nervous System
Peripheral Nervous System
Brain & spinal cord
Autonomic N.S.
Somatic N.S.
What Your Nervous System is Made of
Your brain is made of special cells called neurons that run throughout your body. Neurons carry information around your body and brain.
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Medical Art Service, Munich /, Wellcome Images
Credit Medical Art Service, Munich /, Wellcome Images
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your nervous system
is divided into the central nervous system (CNS)
and the
peripheral nervous system (PNS)
which is the brain and spinal cord
which connects everything to the brain and spinal cord
Organs of the nervous system can be divided into two groups:�
The central nervous system (CNS) is composed of the brain and spinal cord. These neurons cannot regenerate if damaged.
Peripheral Nervous System
Peripheral Nervous System
Parasympathetic vs. Sympathetic Divisions
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your brain
as well as being responsible for
thinking, learning, memory and emotion
Different parts of your brain have different functions…
Credit: Heidi Cartwright, Wellcome Images
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interprets the information it gets though your senses in order to monitor and regulate your body
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Credit: Mark Lythgoe & Chloe Hutton, Wellcome Images
different regions have different functions
Cerebral cortex
Functions include: planning; reasoning; language; recognising sounds and images; memory.
Corpus callosum
connects the brain’s right and left hemispheres
Cerebellum
important for coordination, precision and timing of movement
Brain stem
regulates heart rate, breathing, sleep cycles
and emotions
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the cells of the nervous system are called neurones
cell body
axon
myelin sheath
dendrites
nerve endings
nucleus
structure of a neurone
there are different types of neurone
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sense organ
muscle
sensory neurone
motor neurone
relay neurone
direction of electrical signal
sends signals to your muscles to tell them to move
sends signals from your sense organs
connects neurones to other neurones
dendrites
cell body
axon
myelin sheath
nerve endings
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neurones communicate with each other using a mixture of electrical & chemical signals
cell body
axon
myelin sheath
dendrites
nerve endings
nucleus
an electrical signal is transmitted along the axon
But what happens when the signal reaches the end of the axon?
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cell body
axon
myelin sheath
dendrites
nerve endings
nucleus
the signal
is transmitted to another neurone across a junction called a synapse by chemicals called neurotransmitters.
synapse
signals cross between neurones at the synapse
neurotransmitter
vesicle
synaptic cleft
receptor
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the signal
is transmitted to another neurone across a junction called a synapse by chemicals called neurotransmitters.
cell body
axon
myelin sheath
dendrites
nerve endings
nucleus
synapse
signals cross between neurones at the synapse
neurotransmitter
vesicle
synaptic cleft
receptor
electrical impulse triggers vesicles to move to the synapse membrane
1
vesicles fuse with the membrane and release neurotransmitter into the synaptic cleft
2
neurotransmitter diffuses across the cleft and binds to receptors on the other side
3
Once enough receptors have neurotransmitters bound to them, the signal is transmitted…
4
The point where your muscles and nervous system meet is called the neuromuscular junction (NMJ)
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muscle
Signals sent from your central nervous system to the NMJ tell muscles to move
The synapses at the NMJ use a neurotransmitter called acetylcholine
Classification of Neurons
Classification of Neurons
Classification of Neurons (by function)
Sensory Neurons – (afferent) have specialized receptor ends that sense stimuli and then carry impulses from peripheral body parts to brain or spinal cord.
Can be unipolar or bipolar.
Interneurons – lie entirely within the brain or spinal cord; direct incoming sensory impulses to appropriate parts for processing and interpreting.
Motor Neurons – (efferent) carry impulses out of the brain or spinal cord to effectors (muscles, glands).
Interneurons and motor neurons are multipolar.
Your brain changes and adapts
What happens as our brains mature?
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Credit Marina Caruso, Wellcome Images
your brain changes and adapts all the time and all through your life
your brain learns and forms memories by strengthening synapses that are used a lot and weakening those that are used less often
As your brain matures, it prunes synapses to make it more efficient
During adolescence your brain has a major tidy-up and gets rid of lots of connections it isn’t using
This is a critical and delicate process. It is thought that conditions such as schizophrenia could be the result of it going wrong
Some evidence suggests that using drugs can disrupt this process
Between birth and age 3 your brain makes lots of new synapses
A toddler has 2-3 times more synapses than an adult
What happens as you grow?
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