Nervous Tissue

• Central Nervous System (CNS)
• -Brain
• -Spinal Cord
• Peripheral Nervous System(PNS)
• -All Neural tissue outside CNS
• *Nerves (Cranial and Spinal)
• *Ganglia 
• *Sensory receptors
• -Carries info between CNS and rest of the body

• Sensory- Detects internal & external stimuli & transmits to CNS
• Integrative- Processes, analyzes & stores sensory information; Makes decisions regarding appropriate responses. 
• Motor- Controls muscles & glands in response to sensory info

• Sensory Nervous System
• Motor Nervous System

• Transmits all sensory info from receptors to CNS (afferent)
• Contains Somatic Sensory and Visceral Sensory
• Contains both CNS and PNS components

• Receives sensory info from skin, fascia, joints, skeletal muscles and special senses (taste, balance, vision, hearing)
• Part of the Sensory Nervous System

• Receives sensory information from viscera and  blood vessels and transports to CNS
• Part of the Sensory Nervous System

• Transmits motor commands from CNS to muscles and glands (efferent)
• Somatic Motor (Voluntary: Skeletal muscle)
• Autonomic Motor (Involuntary: Cardiac Muscle, smooth muscle, glands)

• Basic unit of Nervous System
• Most specialized cell in the body
• Conducts impulses
• High metabolic rate
• Long-lived
• Non-mitotic

• Support, nourish and protect
• Most numerous
• Mitotic

• Cell body of neuron
• Contains nucleus surrounded by cytoplasm
• Receives, integrates and sends impulses

Assist moving materials between cell body and axon of a neuron

Yellow-brown pigment of neuronal lysosomes, accumulates in cytoplasm of neurons

Shape and support of neurons

• A process connected to cell body of neuron
• Receive impulse from other Neurons or receptors 
• Conduct impulse towards cell body
• Numerous and short branched

• Carries impulse away from neuron cell body (efferent)
• Carries towards: Neuron, Muscle fibers, glands
• Long and singular
• Joined to cell body at axon hillock

• AKA axon terminals 
• Numerous, fine processes at ends of axon and its collaterals 
• Swelled tips are called synaptic knobs; strings are varicosities

• One process (Dendrites and axon fused)
• Cell bodies usually located in ganglia 
• Usually Sensory (Pain, touch, pressure, temperature)

• Two processes extend directly from cell body: One dendrite and one axon
• Rare; Special sensory (eye, inner ear, olfactory epithelium)

• Contain several dendrites and one axon
• Most common
• Motor neurons and interneurons

• Afferent - Signal sent from nerve receptors to spinal cord and brain
• Efferent - Signals sent from brain to peripheral body.

• -Afferent
• -Transmit from receptors to CNS

• -Efferent
• -Transmit from CNS to Effectors (Muscles or glands)

• CNS
• Integrate Sensory AND Motor
• Most numerous
• Decide how body responds to stimuli

• Fibrous Astrocytes (Mainly in white matter)
• Protoplasmic (Gray matter)

• Most numerous
• Processes make contact with blood capillaries, neurons, and pia matter.
• Assist with blood brain barrier
• Fill spaces, provides support
• Assist in neuronal development
• Help maintain appropriate chemical environment

• Type of Glial Cell
• Ciliated cubodial/columnar cells epithelial cells 
• Line ventricles & Central canal
• Form Choroid plexus with blood capillaries
• Produce & help circulate CSF
• CNS

• Made from Ependymal cells and blood capillaries
• Produces cerebrospinal fluid; A clear liquid that bathes the CNS and fills internal cavities

• Type of Glial Cell
• They're small, wondering phagocytes
• Derived from monocytes 
• Lowest glial cell in number in CNS

• Large bulbous type of Glial cell
• Provide myelin sheath to axons in CNS
• Myelinates axons of multiple neurons

• Satellite cells 
• Neurolemmocytes

• Ependymal Cells
• Microglial Cells 
• Oligodendrocytes

• PNS Glial Cells
• Flattened cells around cell bodies of ganglia
• Provide structural Support
• Regulate exchange between neuronal cell bodies a& interstitial fluid

• PNS Glial Cell
• Can enclose many axons
• Provides myelin sheath to axons in PNS Myelinates only single axon
• Participates in axon regeneration

• Sheath composed of multi-layers of glial plasma membrane
• Neurofibril nodes - gaps in myelin sheath 
• Provided by: Neurolemmocytes (PNS) from inner myelin sheath & outer neurilemma; Oligodendrocytes (CNS) form myelin sheath
• Insulates
• Increase speed of conduction

• Continuous- Typical of non-myelinated axons (Slower)
• Saltatory- occurs along myelinated neurons; no current where myelinated; Action potential jumps from neurofibril node to node; much faster

• Must be in the PNS
• Requires: Intact cell body, functional neurolemmocytes & intact neurilemma, slower formation of scar tissue.

• Chromatolysis- Nissi bodies break up in to fine granular masses.
• Wallerian degeneration of distal end of axon and myelin sheath
• Phagocytosis of debris
• Mitosis of neurolemmocytes, grow toward each other forming "regeneration tube"
• Axon regrows within tube (proximal to distal)
• New Myelin sheath forms around regrown axon

• Intercellular junction between neuron and:
• Another neuron
• Muscle cell
• Gland cell

• Converts electrical signal into chemical signal
• Sends the signal

Receives the mesage

From axon to axon dendrites

From axon to axon cell body

From axon telodendria to axon telodendria 

Seperates presynaptic and post synaptic cells

Are the chemical signal

• Ions flow through gap junctions
• A large number or cells can produce action potentials in unison 
• Faster communication
• Can synchronize a group of neurons (or muscle fibers)
• -ie. digestive movements or heartbeat

• Has a synaptic cleft that separates pre and post synaptic cells
• Pre synaptic neuron much convert electrical to chemical signal
• Send neurotransmitters 
• Slower relay in information 

Functional group of neurons that process specific types of information

Presynaptic neuron stimulates a single spot-synaptics neurons (the 2nd stimulates another ect)

• Single pre-synaptic neuron stimulates several post-synaptic neurons
• This arrangement amplifies the signal
• Ie. A sensory impulse can be relayed to several brain regions

• Collaterals from later neurons synapse with earlier ones
• Sends signals back through the circuit again and again
• ie. Breathing suring sleep

• A sing presynaptic cells stimulates groups of neurons & each group synapses with a common post-synaptic neuron 
• Impulses reach final output cell at different times 
• Ie. Precise mental activities - Mathematical calculations 

• Bundles of parallel axon in PNS
• Functionally classified as sensory, motor, and mixed
• Organized by three CT coverings: Endonerium (each axon) Perineurium  (Each fascile), epineurium (all fasicles covering nerve)

• Areolar connective tissue 
• Separates and electrically isolates each axon

• Dense Irregular connective tissue 
• Supports blood vessels supplying the capillaries within the endoneurium 

• Dense irregular connective tissue ancloses the entire nerve
• Provides support and protection to fascicles within

The Autonomic nervous system