- Brain (80-100 billion neurons) and spinal cord (100 million neurons)
Central Nervous System
Cranial nerves and branches, spinal nerves and branches, ganglia, plexuses, and sensory receptors
Peripheral Nervous System
-Sends information to the CNS from sensory receptors through afferent (sensory)
neurons
Sensory
Takes information from the CNS to target cells via efferent neurons
Efferent
-Basic signaling nits of the nervous system Components - Cell Body - Dendrites - Axons - Presynatic Terminals
Neurons
- Contains the nucleus and protein synthesizing regions
Cell body (Soma)
Receive incoming signals from neighboring cells
Dendrites
Carry outgoing signals from the integrating center to target cells
Axons
Contain the transmitting elements that are transferred from the soma.
Presynatic Terminals
During development the dendrite fused with the axon
Pseudounipolar
Two relatively equal fibers extending off the soma
Bipolar
CNS interneurons that have no apparent axon
Anaxonic
Multipolar
-Carry information about temperature, pressure, light, and other stimuli to the
CNS
-Specialized receptors convert stimulus to electrical energy
Afferent Sensory
Complex branching neurons that facilitate communication between neurons
Interneurons
Usually have axon terminals or varicosities
Efferent
- May be Efferent, Afferent, or Mixed
Nerves
Glia
Composed of multiple concentric layers of phospholipid membrane
wrapped around an axon
- Provides structural stability and insulates the neuron to speed up signals
(saltatory conduction)
Myelin
Multiple Sclerosis caused by
Demyelination of brain and spinal cord
Ependymal
Highly branched glial cells believed to make up half of all cells in the
brain
- Several subtypes, forms a functional sub-network
Functions
- Take up and release chemicals at synapses
- Provide neurons with substrates for ATP production
- Help maintain homeostasis in ECF (take up K+ and H2O)
- Surround vessels
- Part of the blood brain barrier
- Influence vascular dynamics
Astrocytes
-Specialized immune cells
-Functions
-Protect and preserve neuronal cells from pathogens and facilitate recovery from metabolic insults
-If activated past a threshold or remain active too long they
display detrimental properties
Microglia
Satellite Cells