Transcript Neuron & the Nervous Systems & Reflex

Nervous Systems
The Nervous System:
Sends messages quickly but they don’t last long.
Broken into two parts:
• Central Nervous System (CNS)
– Brain and spinal cord
• Peripheral Nervous System (PNS)
– Carries messages to and from CNS
The Nervous System: It breaks down into two parts.
Central nervous
system
Peripheral
nervous system
Sympathetic and parasympathetic divisions
of the nervous system
Summary of autonomic
differences
Autonomic nervous system controls physiological arousal
Sympathetic
division (arousing)
Pupils dilate
Parasympathetic
division (calming)
EYES
Pupils contract
SALIVATION
Increases
Perspires
SKIN
Dries
Increases
RESPERATION
Decreases
Accelerates
HEART
Slows
Inhibits
DIGESTION
Activates
Secrete stress
hormones
ADRENAL
GLANDS
Decrease secretion
of stress hormones
Decreases
3 types Neurons
Types of Neurons
Sensory
Motor
Interneurons
Sensory Neurons
• INPUT From sensory organs to the brain
and spinal cord
Drawing shows a
somatic neuron
Sensory
Neuron
Brain
Spinal
Cord
Motor Neurons
• OUTPUT From the brain and spinal
cord, to the muscles and glands
Sensory
Neuron
Brain
Spinal
Cord
Motor
Neuron
Interneurons
• Interneurons
carry
information
between other
neurons only
found in the
brain and spinal
cord
Sensory
Neuron
Brain
Spinal
Cord
Motor
Neuron
The Neuron & Action Potential
The basic building block of our
nervous system and how it sends
messages.
Cell Body & Nucleus
The Cell Body
Contains the cell’s nucleus
– round, centrally located
structure
– contains DNA
– controls protein
manufacturing
– directs metabolism
– no role in neural signaling
Dendrites
Dendrites
• Information collectors or receivers
• Receive inputs or signals from neighboring
neurons
• Inputs may number in thousands
• If enough inputs the cell’s AXON may
generate an electrical output
Dendritic Growth
• Mature neurons generally can’t divide
• But new dendrites can grow
• Provides room for more connections to other
neurons
• New connections are basis for learning
• Studies show people with higher education have
more dendritic connections than someone that is a
high school dropout.
Neural Networks
Axon
Axon
Axon
• Where all the action is
• Action Potential takes place – electrical
charge is sent down the axon.
• One axon per cell, 2 distinct parts
– tube-like structure
– branches at end (axon terminals) that branch out
to dendrites of other cells
Myelin Sheath & Nodes of Ranvier
Myelin Sheath
•
•
•
•
White fatty casing on axon
Acts as an electrical insulator
Not present on all cells
When present, increases the speed of neural signals
down the axon allowing the action potential to
“jump” to each Node of Ranvier - like a paved
highway (see video below to compare mylenated
axons vs. non-mylenated axons
• If this degenerates (dirt road), you have multiple
sclerosis and can’t control your muscles.
If time view this in a video click on the web
address below (it will use QuickTime):
Mylenated Axon
Axon Terminal or Buttons
Axon
Terminals
Axon Terminal or Buttons
• This is where the electrical impulse triggers
synaptic transmission to the dendrites of a
receiving neuron.
Glial Cells
•They are the janitors of the neuron.
•Support cells that provide neurons with
structural support and nutrition.
•They also remove cell wastes and enhance the
speed of the neuron
The Reflex
Works by bypassing the brain so you can react quicker.
Sensory Neuron
Interneuron
Motor Neuron
A Neural Chain
A Neural Chain
A Neural Chain
A Neural Chain
A Neural Chain
A Neural Chain