Download Nervous System

Cells & Systems
The Nervous System
The Nervous System
I wonder if
IT
BURNS!!
that’s
hot?
• The system that constantly
monitors and responds
the stimuli (stimulus)
around you …
• Stimuli your body can respond to …
(Internal or External)
- Temperature
- Sound
- Light
- Body Chemistry
- Pressure
- Dangers
Neurons
• Nervous system is mostly one type of tissue
– Nervous Tissue
• This tissue is made up entirely of specialized
cells called neurons
– Brain, spinal cord, nerves = nervous tissue
• Job of a neuron?
– Send and receive messages
Neurons - Photos
Neurons Cont …
• A neuron receives messages from small branches
called dendrites
• The incoming messages pass from dendrite to cell
body itself to the axon
• The axon trails off the cell and connects to the
neighbouring cells dendrites
Slice of brain
• We have electrical transmission!
(hippocampus)
Axon
Dendrite
Cell Body
Neurons Cont …
System Organization
• Two main divisions
• The Central
Nervous System
– Brain
– Spinal Cord
• The Peripheral Nervous System
– Cranial Nerves
– Spinal Nerves
Side Topic – Not to Study!
• How does your brain work … in lobes (zones)
Nervous System – The Real Deal
The Peripheral Nervous System
• Consists of two types of neurons
• Sensory Neurons
– Information from body  central nervous system
• Motor Neurons
– From central nervous system  muscles/organs
• But wait! We can split this system even more!
The Peripheral Nervous System Cont …
• The PNS has conscious & unconscious
control
• Somatic Nervous System
– You hear a sound … to look or not to look?
– Conscious/Voluntary – you are in control
• Autonomic Nervous System
– Adjust pupil size to light (let’s prove that one),
heart rate when exercising
– Unconscious control – body just does it
Nervous System Graph … Helps for study!
The Central Nervous System
• We constantly receive stimuli from the outside
world: sights, sounds, smells, feel, etc …
• Taking in all the stimuli and reacting to it
• The brain is generally (very, very generally)
divided into 3 main sections
– Cerebrum
– Cerebellum
– Medulla
Central Nervous System Cont …
• Cerebrum
• Control/reaction to senses
• Movement
• Thinking
• Cerebellum
– Balance
• Medulla
– Breathing
– Heart Rate
Central Nervous System Cont …
• The spinal cord connects the brain to the
peripheral nervous system
– Like a highway of information
• It contains a special type of neuron called an
interneuron
– They connect one neuron to another
Reflex Response – The Shortcut
• When sensory & motor work together and do
not use the brain  we call that a reflex
– Automatic response by the nervous system to an
external stimulus
• For example … you put your hand on a tac
– Sensory neurons in your hand react to the pain by
sending nerve impulses (signal) to the spinal cord
– Interneurons relay the message to the motor
neurons
– Impulse travels to your arm which you lift quickly!
Reflex Response Cont …
• Sensory neurons also send a message to
your brain
• However … the message gets there after you
have reacted
• The reflex response helps protect you!
Pain & Reaction Time Video
Uneven Sense of Touch
•
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Smell = specific location
Sight = specific location
Taste = specific location
Hearing = specific location
Touch = everywhere!
• Touch is located everywhere and is the
biggest sensory organ in the body
• Not all parts have the same amount of
receptors however! It is very uneven!
Uneven Sense of Touch
Cells & Systems
Systems Done!