Nerve Cells The Neuron
Dec 23, 2015
Fun facts about neuronsMost specialized cell in
animalsLongest cell:
blue whale neuron10-30 meters
giraffe axon5 meters
human neuron1-2 meters
Nervous system allows for 1 millisecond response time
3 parts of a Neuron
1) Dendrite – branched end that extends out from the cell, provides a large surface area to receive nervous information
2) Cell Body – control center, regular cell organelles (nucleus etc)
3) Axon – long thin fiber, extends out from cell body, carries action potential from cell body
-ending are called synaptic terminals
Nervous system cells
dendrites
cell body
axon
synapse
Neurona nerve cell
Structure and function
many entry points for signal
one path outtransmits signal
signal direction
signaldirection
dendrite cell body axon
3 Types of Neurons
1) Motor – connects to a muscle or gland
2) Sensory – receives a stimulus
3) Interneuron – connects the above 2
Myelin Sheath-Schwann cells contain a lipid called myelin in cell
membrane
-Schwann cells wrap around axon many times
Nodes of Ranvier- gaps between Myelin sheaths
Reflex arc
Direct nervous message from a sensory neuron to inter-neuron to a motor neuron to an effector (a muscle or a gland)
Video
Reflex Arc
A motor, sensory and inter neuron form a reflex arc
Begins with a stimulus causing an impulse in the sensory receptors of a sensory neuron.
The impulse then continues on through the dendrite, cell body and axon of a sensory neuron (DCA).
The impulse passes to the interneuron, passing through dendrite, cell body and axon (DCA).
The impulse passes onto the motor neuron, passing through the dendrite, cell body, and axon (DCA).
This causes a response in an effector (a muscle or a gland)
Summary Neuron TypesSensory
Neuron
Interneuron Motor
Neuron
Structure Long dendrite
Short axon
Short dendrite
Short axon
Short dendrite
Long axon
Function Conduct impulse to cord Interconnect sensory neurons with motor neurons
Conduct impulse to effector (muscle/ gland)
Location Cell body/ dendrite outside spinal cord
Cell body- dorsal root
Entirely within CNS
Cell body/ dendrites in spinal cord
Axon outside spinal cord
Synapses/ synaptic gap
Synapse- region of close proximitySynaptic gap- Space between a neuron
(axon terminal) and the next cellThe next cell could be another neuron or
an effector (muscle/ gland)Space between must be bridged by
neurotransmittersMore on neurotransmission and nerve
impulses tomorrow!