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NERVOUS SYSTEM
The excitable highway
Brainstorm
Groups of 3-4 On Chart Paper, make a mind map of
what you know of the nervous system Thoughts, ideas, knowledge
Gallery Walk
Take about 3-4 Minutes to look around at other groups Mind Maps
Bring your group’s marker to add any thoughts or ideas
What do these mind maps look like?
Learning Goals
Learn the components of a neuron Differentiate amongst the three different
types of neurons
Nerve Cell (Neuron)
Dendrite: Receivers Cell Body: Houses the
nucleus and the majority of the organelles of the cell
Nucleus: Brain of the cell
Nodes of Ranvier
Nerve Cell (Neuron)
Axon: Conducts the nerve impulse along the cell
Myelin Sheath: Some neurons are covered in a fatty myelin sheath
Axon Terminals: relay messages to other neurons
Nodes of Ranvier: Gaps where there is no myelin covering
Nerve Highway
Neurons are the primary component of the nervous system
Nervous system includes the brain, spinal cord and peripheral ganglia
Neurons can be divided into different specialized neurons: Sensory, Motor and Interneurons
Different types of Neurons
Split into 3 different groups Using Chart Paper, describe your group’s
designated neuron
Designate a few members to present findings to the class
Sensory Neuron
Convert external stimulus into an internal stimulus
Stimulated by sensory input (touch, sound, smell, temperature) and send information to the brain
Unlike neurons from the central nervous system, which are activated by other neurons, sensory neurons are activated by a physical sensory input
Motor Neuron
Composed of neurons within the CNS, and extend axons out of the CNS, to control muscular contractions Somatic Motor Neurons: Control skeletal
muscular contractions Visceral Motor Neurons: Innervate cardiac
and smooth muscle
Interneurons
All neurons within the CNS are composed of interneurons
Local connections within specific neurons Form chain networks and “highways”
Recap
Neuron/Nerve Cell Structure
Sensory Neuron Motor Neuron Interneuron
Learning Goals
Understand the concept of an Action Potential
Look at the importance of the Sodium-Potassium Pump
How do Neurons transmit a nerve impulse
Nerve Impulse: a message that is sent or convey information along a neuron
Measured using oscilloscope (voltage expressed in millivolts mV – measure of the electrical potential difference between two points)
Resting Potential
Voltmeter is attached along the axon of a neuron, we can monitor the difference in voltage
-65 mV
Threshold
Sodium pumps begin to open, changing the flux in gradient
Action Potential - Depolarization
Rapid change in polarity across the membrane
All or none principle
Sodium Gates Open
+ 40 mV
Action Potential – Repolarization
Potassium gates open and potassium flows down the concentration gradient
-70mV
Refractory Period
After the depolarization period, the axon undergoes a “limbo” period, where the Sodium gates cannot open
This ensures the AP can only move towards the axon terminal
-65 mV
DEMO
PHET Neuron
Speed of Transmission
In Myelinated axons, gated Sodium-Potassium pumps are concentrated at the Nodes of Ranvier
The action potential skips from node to node, creating a faster action potential
Therefore AP’s travel faster on myelinated axons that non-myelinated axons
Recap
Nerve Impulse Resting Period Action Potential
Depolarization Repolarization
Refractory Period Speed of Transmission
Draw an Action Potential Graph Graph out a Nerve Impulse Include, stages of an action potential
charges, extra/intracellular sodium and potassium levels, Na, K gates,
Recap
How do Neurons transmit messages
Recall that axons end in branched axon terminals.
Axon terminals are within close proximity to dendrites of other neurons
No physical contact, separated by a gap called the synaptic cleft (synapse)
Learning Goals
How do neurons send messages amongst each other
Learn a few of the primary neurotransmitters
Synapse – Relayed Message
Occurs when an AP reaches the axon terminal Triggers the influx of Sodium
to the terminal Stimulates vesicles filled with
Neurotransmitter to fuse with the synaptic membrane to release the neurotransmitter
Neurotransmitter cross the synaptic cleft and bind to receptors proteins on the post synaptic membrane to trigger Sodium gates to open, causing an action potential to begin
Reuptake
Neurotransmitter is either reabsorbed by the presynaptic neuron OR
Broken down by specific enzymes
Acetylcholine > acetylcholinerase
Neurotransmitter
Chemicals that transmit signals from a neuron to a target cell across the synapse
Depending on the neurotransmitter, can cause a excitatory or inhibitory response
Acetylcholine (ACh) – responsible for muscular contractions at the neuromuscular junction
GABA – primary inhibitory transmitter in the brain
Neurotransmitter Project
STSE – Society, Technology, Science, Environment
Form groups of 2 people Sign up for a topic on things that may effect
neurotransmitters or disorders of the brain Create a 5-7 minute presentation on your
specific topic – Can be a powerpoint, skit, demo, etc…
Include a 1 page (double spaced) write up of your findings – APA format referencing
Presentations on Monday!
Example
GOOGLE “MOUSE PARTY” – interactive demo
iPad work Period
Use iPad’s to work on project!
Learning Goals
Learn the components of the Central Nervous System (CNS)
Understand the functions of the CNS
Central Nervous System
Composed of the brain and spinal cord
Sensory information is received, motor initiation begins
Protected by bone – skull and vertebrae
Also cushioned by Cerebrospinal fluid
Central Nervous System
Brain contains interconnecting cavities called ventricles, which connect to the central canal of the spinal cord.
Spinal Cord
Spinal cord is protected by individual vertebrae
Vertebrae are separated by intervertebral discs
Spinal Cord
Grey matter contains sensory neurons, motor neurons and interneurons. Dorsal Root of the spinal nerve contains sensory fibers entering grey matter
Ventral Root contains motor fibers exiting the grey matter
Join before leaving the vertebral column
Spinal Cord
White matter contains tracts of neurons taking information to or from the brain
Dorsally: Ascending tract to the brain Ventrally: Descending tract away from
the brain
The Brain
The brain is composed of: cerebrum, diencephalon, cerebellum, brain stem
Divided into 2 hemispheres Each hemisphere is composed of the
frontal lobe, parietal lobe, occipital lobe, and temporal lobe
The lobes
Frontal Lobe: Higher order processes, executive functions and movement
Parietal Lobe: integrating sensory information
Occipital Lobe: Visual processing centers Temporal Lobe: Auditory perception
The Brain
Gallery Activity - Cerebrum Cerebellum Medulla Oblongata