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