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74 Cards in this Set

  • Front
  • Back
Nerve tissue derived from?
Ectoderm, Outer layer of embryo
Description of Afferent Neuron
Receive and transmit info from environment to CNS
Description of Efferent Neuron
Receive and transmit info from the CNS to the periphery
Somatic Nervous System
Composed of neural elements associated with the body wall and extremities (skin, skeletal muscle, bones, joints)
Voluntary Functions
Autonomic (Visceral) Nervous System
Composed of neural elements associated with internal organs or viscera (cardiac muscle, smooth muscle, glandular epithelium)
Involuntary Functions
Similarities in both ANS and SNS?
Components lie in both CNS and PNS
Afferent and Efferent information is transmitted.
How do Neurons respond to stimuli?
By altering electrical potentails that exist between the inner and outer surfaces of their membranes
Cell Body (aka?) - Structure
AKA - Perikaryon
Contains nucleus and surrounding cytoplasm
Cytoplasm - Structure
Abundent RER (Nissl Substance) and plysomes
Well-developed Golgi complexes
Numerous mitochondria
Well-developed Cytoskeleton
Nucleus - Structure
Large, Spherical
Euchromatic w/prominent nucleolus
Cell Body - Function
Trophic center of cell
Receptive to stimuli
Aggregate of neuronal cell bodies in CNS
Aggregate of neuronal cell bodies in PNS
Dendrites - Structure
Short, tapered, highly branched
Organelles similar to cell body, but no Golgi complexes
Dendritic spines are specializations located at synapses (more ion channels, greater AP)
Dendrites - Function
Signal reception
Transmit towards cell body
Axons - Structure
Long, cylindrical, don't branch profusely
Organelles similar to cell body, but NO RER or Polysomes, MORE mitochondria at terminal end
Axon Hillock
Pyrmaid shaped region where the axon emanates from cell body, devoid of Nissl
(Only way to differentiate from dendrite)
Terminal Arborization
Branched distal portion of axon
Each branch terminates on next cell in dilations, called Terminal Boutons
Axons - Function
Generate and conduct nerve impulses
Receptive to stimuli
Motor (efferent) neurons
Control effector organs
Sensory (afferent) neurons
Receive sensory stimuli
Connect other neurons
Most numerous
More than one dendrite and one axon
Most common, efferent and interneurons
(Motor neurons)
One dendrite and one axon
Developmental stage of most neurons
(special sense organs/retina)
Single process that is close to the cell body and divides into two branches (central and peripheral)
(Sensory neurons in dorsal root ganglion)
Molecular Transport Systems (definitions and types)
Transport of substances between cell body and processes, axons and dendrites
Three speeds (slow - .2-4mm/day, intermediate, fast - 20-400mm/day)
Anterograde, Retrograde
Anterograde (Molecular Transport System)
Carries materials (Organelles, macromolecules) from cell body to periphery
Retrograde (Molecular Transport System)
Carries material (Toxins, viruses) from periphery to cell body.
Synapses - Ways to classify
Sites of functional contact between neurons and effector cells
1) Morphology
2) Mechanism of Impulse Conduction
Synapse based on morphology
Axosomatic - Btw axon and cell body
Axodendritic - Btw axon and dendrite
Axoaxonic - Btw axon and another axon (least common)
Synapse based on Mechanism of Impulse Conduction
Electrical, Chemical
Electrical Conduction
Transmit ionic signals through Gap Junctions that cross the pre- and postsynaptic membranes --> conduct neuronal signals directly
Allow for rapid and synchronous firing of interconnected cells
Chemical Conduction
Use chemical messengers to transmit signal from axon terminal bouton (presynaptic cell), across thin extracellular space (synaptic cleft), to a region on another cell (postsynaptic cell) to generate a new signal
Consists of Chemical messengers, transmission, reception
Chemical Conduction - Chemical Messengers
Neurotransmitters - Bind to receptor proteins --> act on ion channels (direct or indirect)
Neuromodulators - Modify function of receptor
Chemical Conduction - Transmission
1) AP reaches terminal boutons of neurons
2) Voltage-gated Ca++ channels open
3) Ca++ influx causes synaptic vesicles to migrate to and fuse with presynaptic membrane
4) Synaptic vesicles release neurotransmitter into synaptic cleft
5) Neurotransmitter binds to receptors on postsynaptic membrane
Chemical Conduction - Reception - Types
Properties of receptors that recognize and bind to NT on postsynaptic cell determine the type of response
Impulse Conduction
Generation of nerve impulse in postsynaptic neuron depends on summation of excitatory and inhibitory impulses reaching that neuron
Significant depolarization of postsynaptic membrane can cause V-gated Na++ to open, generating an impulse
Depolarization of one part of membrane sends E-stim to neighboring regions of membrane, repeating depolarization
Neuron - Function
Receive, transmit, and process stimuli
Release NT's and other informational molecules
Glial Cells - Types
Oligodendrocyte, Schwann Cell, Astrocyte, Ependymal Cell, Microglia
Oligodendrocyte - Structure
Large, ovoid with few radiating processes
Oligodendrocyte - Function/Location
Myelin Production
Ones that don't produce myelin are Satellite Cells associated with neuronal cell bodies
Schwann Cell - Structure
Irregular shape, associated with neurons
Schwann Cell - Function/Location
Myelin production
Ensheath axons - with or without myelin
Ones that do not ensheath axons are called Satellite Cells and are associated with neuronal cell bodies
Astrocyte - Structure
Stellate shape
Multiple radiating processes
Astrocyte - Function/Location
Structural support, Ionic homeostasis, NT uptake
Ependymal Cell - Structure
Cuboidal or low columnar shape
Ependymal Cell - Function/Location
Lines Cavities
Microglia - Structure
Small, ovoid with fine, highly branched processes
Microglia - Function/Location
Macrophagic Activity
Myelin Sheath - Structure
Segmented, multilamellar, lipid rich, wrapping of axons
Formed by plasma membranes of: Oligodendrocytes and Schwann Cells
Oligodendrocytes are capable of myelinating several internodes and several axons
Schwann Cells are capaply of myelinating only one internode and one axon
Single segment of myelin sheath on an axon
Node of Ranvier
Interval at which an axon is not covered by myelin sheath, located between intrnodes
Myelin Sheath - Function
Provides electrical insulation.
Increase speed of impulse conduction by saltation, method whereby an AP jumps, or saltates, from node to node
Gray Matter
Contains neuronal cell bodies, dendrites, unbyelinated axons, and glial cells.
Gray Matter in Brain
Occupies superficial outer layer and deeper regions.
Constitutes - cortex and nuclei
Gray Matter in Spinal Cord
Occupies central H-shaped region
Constitutes - nuclei of dorsal and ventral horns
(ventral horn is location of cell bodies of (mulipolar) motor neurons)
White Matter
Contains myelinated nerve axons and oligodendrocytes
White Matter in Brain
Occupies deeper regions
Constitutes tracts
White Matter in Spinal Cord
Occupies peripheral region
Constitutes tracts
Dura Mater
Outermost layer
Dense irregular CT
Continuous w/periosteum in skull
Separated from vertebrae in spine by epidural space
Separated from arachnoid mater by subdural space
Arachnoid Mater
Middle layer
Cell layer in contact with dura mater and a system of trabeculae connected to pia mater
Cavities between trabeculae form subarachnoid space and are filed w/CSF
Pia Mater
Innermost layer
Loose CT lying directly on surface of nervous tissue
Blood Brain Barrier - Structure
Capillary Endothelial (Epithelial) Cells - Tight junctions between adjacent cells
Astrocytes - End foot processes closely associated with endothelial cells
Blood Brain Barrier - Function
Highly Selective Barrier
Aging of Neurons
Atrophy of brain tissue due to loss and shrinkage
Decreased nerve conduction velocity in sensory and motor systems
Alterations in neuron structure and function
Diminished blood supply
Ovoid structures containing neuronal cell bodies and glial cells supported by connective tissue
Sensory (Somatic and Visceral) Ganglia
Associated with dorsal roots of spinal nerves and cranial nerves V, VII, VIII, IX, X
Contain cell bodies of (pseudounipolar) sensory neurons
Motor (Visceral) Ganglia
Sympathetic and Parasympathetic
Consist of axon with its investing schwann cells
Peripheral nerve composed of one or more fascicles (bundles) of nerve fibers surrounded by connective tissue sheaths
Afferent Nerve Endings
Receptors - located at distal tips of peripheral processes of sensory neurons
Initiate nerve impulse in response to stimulus
Afferent - Classified based on structure
Nonencapsulated (Simple)- Free nerve endings. Detect relatively unsophisticated modalities (touch, pain, temp, etc.)
Encapulated (Compound)- Common. Detect sophisticated modalities (proproception, smell, taste, sight, hearing)
Afferent - Classified by Function
Exteroceptors - Respond to stimuli outside body (touch, cutaneous pain, temp, smell, sight, hearing)
Enteroceptors - Respond to stimuli from viscera. (Chemical composition of blood, blood pressure, visceral distention and pain, hunger, thirst, etc.)
Proprioceptors - Respond to stimuli regarding posture and movement of body parts. (vestibular apparatus of ear, muscles, tendons)
Surface Coverings of Nerves
Epineurium - Dense irregular CT surrounding entire nerve
Perineurium - Dense irregular CT surrounds bundles of nerve fibers (fascicles)
Endoneurium - Delicate layer of loose CT surrounding individular nerve fibers
Aging of PNS
Decreased number of myelinated fibers due to decrease in protein production needed to express myelin and vascular occlusion
Atrophy of axons
Decreased nerve conduction velocity
Altered density and morphology of sensory receptors