Nerve Cells The Neuron

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

-Myelin Sheath covers some axons

Myelin Sheath

-Formed by a type of neuroglia called Schwann cells

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

Rapid, predictable, and involuntary responses to stimuli

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)

Reflex Arc

Reflex Arc

Nerves

Combination of nerve cell fibersSensory dendrites and motor axons

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!

Synapse