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Nervous System (Central Nervous System (Structures: (Brain, Spinal cord,…
Nervous System
Central Nervous System
Structures:
Brain
Spinal cord
Nucleus
Tracts
Function:
Integration
Interpret
Neuroglia:
Astrocyte
Largest cell
Most abundant cell
Helps maintain the correct chemical environment for electrical signal transmission
Microglia
Phagocyte
Mobile
Looks for invaders & destroys pathogens
Cleans up dead cells & debris
Ependymal cells
Simple cuboidal & columnar epithelium
Cilia
Circulates cerebrospinal fluid
Microvilli
Increases surface area
Absorbs stuff from blood vessels to make cerebrospinal fluid
Lines ventricles
Myelination:
Oligodendrocyte
One cell wraps around multiple sections of axon
Matter:
Gray matter
Neuron cell body with dendrites
Nonmyelinated
Looks tan
40% of brain
Where processing happens
White matter
Tracts
Looks white
Only axons
Myelinated
Deeper than gray matter
60% of brain
Conducts messages
Peripheral Nervous System
Structures:
Nerves
Spinal nerves
Cranial nerves
Cluster/group of axons
Ganglia
Ganglion
Collection of neuron cell bodies
Types of sensory fibers:
Somatic sensory fiber
Located:
Skin
Body wall
Limbs
Muscles
Joints
General senses:
Sensory receptors
Mechanoreceptor
Touch
Pressure
Vibration
Proprioceptors
Stretch
Coordinate movement
Thermoreceptor
Temperature
Nociceptor
Pain
Special senses:
Hearing
Equilibrium
Vision
Visceral sensory fiber
Located:
Guts in ventral body cavity
General senses:
Stretch
Pain
Temperature
Chemical changes
Irritation in viscera
Nausea
Hunger
Special senses:
Taste
Smell
Types of motor fibers:
Somatic motor fiber
Located:
Skeletal muscle
Function:
Motor innervation
Visceral motor fiber
Located:
Smooth muscle
Cardiac muscle
Glands
Endocrine glands
Exocrine glands
Function:
Motor innervation
Neuroglia:
Satellite cells
Surrounds neuron cell bodies in the dorsal root ganglion
Structural support
Helps regulate what enters/exits the neuron cell bodies
Myelination:
Schwann cell
One cell wraps around one section of axon
General Anatomy
Nerve
Is an organ
Has more than one tissue type
Most nerves can carry both sensory & motor signals
A large collection of neuron axons
Epineurium
Fibrous connective tissue surrounding outside of nerve
Perineurium
Fibrous connective tissue surrounding a fascicle
Fascicles
Bundles of nerve fibers
Endoneurium
Areolar connective tissue surrounding a nerve fiber
Myelin sheath
Insulator that surrounds an axon
Axon
Fiber that sends electrical signals
Has blood vessels inside
Microscopic Anatomy
Cell body (soma)
Receives signals from other cells
Nucleus
Directs cell functions
Nucleolus
Makes ribosome units
Synthesize proteins
Chromatophilic substance
Clusters of free ribosomes & rough endoplasmic reticulum in cell body
Constantly creating new plasma membrane
Dendrites
Receives signals from other cells
Branches off of cell body
Axon hillock
Between cell body and axon
Axon
Axon collaterals
Branches off of an axon
Transmits signals away from neuron cell bodies
Myelin sheath
Surrounds axon for insulation
Allows signals to travel faster
Myelin sheath gaps
Node of Ranvier
Terminal arborization
Branches at the end of an axon
Axon terminals (terminal boutons)
Connects to other cells
Determines if the signals will get passed on to cell body
Structural Types of Neurons
Multipolar
Most common
Many processes
Many dendrites
One axon
Bipolar
Two processes from one cell body
Not common
Unipolar (pseudounipolar)
One stock from cell body
One process
Functional Types of Neurons
Motor
Efferent neurons
Multipolar
Carry signals from CNS to effector (muscle or gland)
Cell body in CNS
Axon in PNS
Very long
Sensory
Unipolar
General senses
Axon in PNS & CNS
Very long
Bipolar
Special senses
In ganglia of PNS
Interneurons
Association neurons
Multipolar
Only in CNS
Entire cell in CNS
Usually smaller
Make up 99.98% of all neurons