Learning Target: NeuronsLearning Target: NeuronsBasic Unit of the Nervous System
Learning Target: Neurons
I Can… List the three main types of neurons and their role in the nervous system and describe the general structure and function of a neuron
I Will…• Identify the three types of neurons and their
associated function• Label the main and accessory structures of a
typical neuron• Describe how neurons transmit impulses within
a neuron and between neurons
Learning Target: Neurons
Neuron – specialized cell that stores information and carries messages within the nervous system and between other body systems.• Communication Systems
Learning Target: Neurons
Three types:• 1) Sensory neuron (afferent)• Detects stimuli • Transmits signal to CNS
• 2) Interneuron (associative)• Receives signals from sensory neurons • Relays info within CNS and processes
information• 3) Motor neuron (efferent)• Transmits messages from CNS to targets
(organs, tissues, cells)
Learning Target: Neurons
Basic Neuron Structure:• All neurons have 3 basic structures• 1) Cell body• Contains nucleus and organelles
• 2) Dendrites• Branch-like extensions of cytoplasm and cell
membrane• Receive messages from neighboring cells
• 3) Axon• Long extension that carries electrical signal
away from cell body • Passes message to other cells
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Learning Target: Neurons
Main Structures:1) Cell Body2) Nucleus3) Dendrites4) AxonAccessory Structures:5) Myelin Sheath6) Schwaan’s cell7) Node of Ranvier8) Axon terminals
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Learning Target: Neurons
Before a Neuron is Stimulated …Resting potential – when a neuron is NOT transmitting an impulse.• Maintenance of ion concentrations across the
membrane.• Unequal inside & outside neuron.• More Na+ outside than inside cell.• More K+ inside than outside cell.
• Creates a “relative” negative charge inside the cell compared to the outside of the cell.
Learning Target: Neurons
Before a Neuron is Stimulated …Sodium-Potassium pump- Helps maintain resting potential by using energy to actively transport Na+ ions out of the cell and bring K+ ions into the cell.• Leak channels allow Na+ to diffuse into the cell.• Leak channels allow K+ ions to diffuse out.• More K+ than Na+ channels (positive charges
exit faster than enter – maintain relative negative charge)
Learning Target: Neurons
Before a Neuron is Stimulated …
Learning Target: Neurons
How neurons function…• Transmission of signal within a neuron• Based on “action potential” - change of distribution of
ion charges. Stimulation causes…• Opening of gated Na+ ion channels in cell membrane
allowing diffusion to take place (positive charges rush in).
• Stimulates adjacent channels to open.• Once ions rush in, channels snap shut. (traps Na+ ions)• K+ channels open and close more slowly.• Causes repolarization of part of the membrane.• Reversing electrical charges travel along membrane
Learning Target: Neurons
How neurons function…• All or None (like dominoes falling…
if the first goes, they all go)
Learning Target: Neurons
How neurons function…• Transmission of signal between neurons• Action potential must move from
axon terminal of one neuron to dendrite of next neuron• Tiny gap between cells – synapse• Axon terminals release neurotransmitters from
vesicles• Diffuses across synapse• Binds to receptors on dendrite cell membrane
surface• Initiates action potential in second neuron
Learning Target: Neurons
Learning Check√: Neurons
1. What are the three types of neurons and their function in the nervous system?a) _____________ Function: ___________b) _____________ Function: ___________c) _____________ Function: ___________
2. What are three main structures of all neurons and what is the function of each structure?a) _____________ Function: ___________b) _____________ Function: ___________c) _____________ Function: ___________