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Cells of the Nervous System
- Neurons
- are excitable
- hey generate and
transmit electrical
signals
- these are called action potentials
- these are called action potentials
- hey generate and
transmit electrical
signals
- human brain contains 100,000,000,000 neurons
- any given neuron can have upwards of 10,000 synapses
- therefore in the brain there are 100,000,000,000 x 10,000 synapses
- the number of possible networks is almost infinite
- the number of possible networks is almost infinite
- therefore in the brain there are 100,000,000,000 x 10,000 synapses
- as the incredible ability to :
- process information
- learn
- solve complex tasks
- have emotions
- process information
- any given neuron can have upwards of 10,000 synapses
- have four regions
- cell body
- contains the nucleus
and organelles
- contains the nucleus
and organelles
- dendrities
- bring information to the
cell body
- bring information to the
cell body
- axon
- carries information away from
the cell body
- carries information away from
the cell body
- axon terminals
- at the tip of the axon
- at the tip of the axon
- cell body
- all neurons share some common mechanisms
- the plasma membranes of all neurons can generate
and conduct action potentials
- action potentials can travel at speeds of up
to 100 m/sec (360km/hour)
- the axon terminal comes extermely close to the
membrane of the target cells forming a synapse
- electrical synapses allow the action potential to pass
directly between two neurons
- synapses can either be electrical or chemical
- in vertebrates most synapses are
chemical
- the arrival of the action potential at the terminal
causes it to release neurotransmitter
- neurotransmitters are chemicals which diffuse to
the receptors on the target cell
- neurotransmitters are chemicals which diffuse to
the receptors on the target cell
- the arrival of the action potential at the terminal
causes it to release neurotransmitter
- in vertebrates most synapses are
chemical
- l
- synapses can either be electrical or chemical
- the plasma membranes of all neurons can generate
and conduct action potentials
- are excitable
- Glia
- modulate neuron activity and provide support
- outnumber neurons in the human brain
- about 10 times more
- represent 90% of the cells in the brain and spinal cord
- about 10 times more
- have numerous functions
- Ependymal cells
- promote the circulation of cerebrospinal fluid
- modified ependymal cells found in the choroid
plexus are responsible for the production of
cerebrospinal fluid
- there are four choroid plexuses, one
in each ventricle of the brain
- there are four choroid plexuses, one
in each ventricle of the brain
- promote the circulation of cerebrospinal fluid
- Microglia
- protect the nervous sytem from micro organisms
- protect the nervous sytem from micro organisms
- oligodendrocytes
- form the myelin sheaths around axons
- form the myelin sheaths around axons
- Schwann Cells
- Astrocytes
- provide structural support for neurons
- regulate extracellular ions and neurotransmitters
- induce the formation of the blood-brain barrier
- this regulates the chemical environment of the CNS
- this regulates the chemical environment of the CNS
- store glycogen which can be broken down to supply neurons with fuel
- aid repair and regeneration of neurons
- make contact with blood vessels and neurons
- signal changes in the
composition of the blood
- signal changes in the
composition of the blood
- their role in plasticity/memory has been discussed recently
- it's projections can make contact with
more than 100,000 synapses
- provide structural support for neurons
- Ependymal cells
- modulate neuron activity and provide support
- tripartite synapse
- the idea that a synapse has pre and porsynaptic neurons as well as
connections from astrocytes
- the idea that a synapse has pre and porsynaptic neurons as well as
connections from astrocytes
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