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Chapter 12
Neural Tissue
63
Anatomy
Undergraduate 2
11/19/2017

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Term
Neurons
Definition
The basic functional units of the nervous system.
Term
Neuroglia (glial cells)
Definition
Support and protect neurons.
Act as phagocytes
Help regulate the composition of the interstitial fluid
Term
What does the Central Nervous System consist of?
Definition
The brain and spinal cord.
Contains neural tissue, connective tissue, and blood vessels.
Term
Functions of the CNS
Definition
Process and coordinate:
sensory data: from in/outside body
motor commands:control or adjust peripheral organs
higher functions:intelligence, memory, learning, and emotion
Term
What does the Peripheral Nervous System consist of?
Definition
All neural tissue outside the CNS
Term
Functions of the PNS
Definition
Deliver sensory information to the CNS
Carries motor commands
Term
Nerve fibers (bundles of axons)
Definition
Cranial nerves-connected to the brain
Spinal nerves-attach to the spinal cord
Term
2 divisions of the PNS
Definition
Afferent division
Efferent division
Term
Afferent division
Definition
Carries sensory information from PNS sensory receptors TO the CNS
Term
Receptors
Definition
Detect changes or respond to stimuli
May be neurons and specialized cells, complex sensory organs
Term
Efferent division
Definition
Carries motor commands FROM the CNS to muscles, glands, and adipose tissue
These target organs are effectors.
Has both somatic and autonomic components
Term
Somatic nervous system
Definition
Controls skeletal muscle contractions: voluntary and involuntary (reflexes) muscle contractions.
Term
Autonomic nervous system
Definition
Controls subconscious actions: contractions of smooth and cardiac muscle and glandular secretions

Sympathetic division: stimulating effect
"Fight or flight"

Parasympathetic division: relaxing effect
"Rest and digest"
Term
What does the efferent division consist of?
Definition
The somatic nervous system (SNS) and the autonomic nervous system
Term
What does the autonomic nervous system consist of?
Definition
The sympathetic division and the parasympathetic division.
Term
Cell body (soma)
Definition
contains a large round nucleus with a prominent nucleolus.
Cytoplasm: perikaryon
Cytoskeletan contains: neurofilaments and neurotubules
neurofibrils: bundles of neurofilaments
Term
Structure of a multipolar neuron
Definition
Contains the cell body, several short, branched dendrites, a single long axon, ending in terminal branches called telodendria
Term
Major organelles of the cell body
Definition
large nucleus and nucleolus
perikaryon
mitochondria
RER and ribosomes (produce neurotransmitters)
cytoskeletan:neurofilaments and neurotubules
neurofibrils (bundles of neurofilaments that provide support for dendrites and axon
Nissl bodies
Term
Nissl bodies
Definition
Dense areas of RER and ribosomes that make neural tissue appear gray (gray matter)
Term
Dendrites
Definition
Slender, sensitive extensions that extend out from the cell body.
Highly branched-each branch has fine studded processes called dendritic spines
Dendritic spines-80-90% of total surface area
Receive information from other neurons
Term
Axon
Definition
long cytoplasmic process
carries an electrical impulse (action potential)
Axoplasm-cytoplasm of axon, contains neurotubules, neurofibrils, enzymes, organelles
Axolemma-covers the axoplasm, is a specialized portion of the plasma membrane
Term
Collaterals
Definition
branches of a single axon
Term
synaptic terminals
Definition
the tips of telodendria (fine extensions of distal axon)
Term
Axon hillock
Definition
thick section of cell body
attaches to initial segment (base)
Term
Synapse
Definition
Area where a neuron communicates with another cell
Involves 2 cells:
1.Presynaptic cell-neuron that SENDS a message
2.Postsynaptic cell-RECEIVES the message

Synaptic cleft:small gap that separates the 2 cells
Term
Synaptic knob
Definition
Expanded area of presynaptic neuron's axon which contains synaptic vesicles of neurotransmitters
Term
Neuromuscular junction
Definition
A synapse between a neuron and muscle
Term
Neuroglandular junction
Definition
Synapse between a neuron and a gland.
Term
Neurotransmitters
Definition
-chemical messengers released at presynaptic membrane
-affect receptors of postsynaptic membrane
-broken down by enzymes
-reassembled at synaptic knob
Term
Axoplasmic transport
Definition
Occurs along neurotubules within the axon

Transport raw materials between cell body & synaptic knob

Powered by mitochondria

Anterograde: from the cell body to the axon terminal carried by kinesin

Retrograde: From the axon terminal to the cell body carried by dynein
Term
Neurons are classified as ______, ______, _____, or ______ on the basis of the relationship of the dendrites to the cell body and the axon.
Definition
Anaxonic, unipolar, bipolar, or multipolar
Term
Anaxonic neurons
Definition
Found in brain and sense organs
No axon
Term
Bipolar neurons
Definition
one dendrite, one axon, with cell body between the two.
Found in special sensory organs
Are rare
Term
Unipolar neurons
Definition
The dendrites and axon are continuous, basically fused, the cell body lies off to one side.

Very long axons

Most sensory neurons
Term
Multipolar neurons
Definition
The most common in the CNS

Includes all the motor neurons that control skeletal muscles.

Two or more dendrites and a single axon.
Very long axons
Term
Sensory neurons
Definition
Afferent neurons of PNS
Term
Motor neurons
Definition
Efferent neurons of the PNS
Term
Interneurons
Definition
Associated neurons
Term
Functions of Sensory neurons-afferent
Definition
Deliver information from sensory receptors TO the CNS

Monitor internal environment-visceral sensory neurons

Monitor effects of external environment-somatic sensory neurons
Term
Structures of sensory neurons
Definition
Unipolar, processes (afferent fibers) extend FROM sensory receptors TO the CNS

Cell bodies grouped in sensory ganglia
-ganglion: collection of cell bodies in PNS
Term
Types of sensory receptors
Definition
Interoceptors: monitor internal systems (digestive, respiratory, urinary, cardiovascular, reproductive)

Exteroceptors: provide information about external environment-touch, pressure, temperature
Complex senses-sight, smell, hearing

Proprioceptors: monitor position and movement (skeletal muscles and joints)
Term
Motor neurons-efferent
2 different systems
Definition
Somatic nervous system
Autonomic nervous system
Term
Somatic Nervous System
Definition
-includes all somatic motor neurons that innervate skeletal muscles
-conscious control
-cell bodies lie in CNS, axons extend into periphery
Term
Autonomic Nervous System
Definition
-visceral motor neurons innervate all other peripheral effectors: smooth muscle, cardiac muscle, glands, adipose tissue
Term
2 groups of efferent axons
Definition
Signals from CNS motor neurons to VISCERAL effectors pass synapses at autonomic ganglia dividing axons into:

-Preganglionic fibers-CNS to autonomic ganglia
-Postganglionic fibers-connect ganglion cells to effectors
Term
Autonomic ganglia
Definition
Collection of neural cell bodies that regulate autonomic nervous system, control peripheral effectors
Term
Interneurons
Definition
Found mainly in the brain, spinal cord, a few in autonomic ganglia

Between sensory and motor neurons
Term
Functions of interneurons
Definition
-Distribution of sensory information
-Coordination of motor activity
-Involved in higher functions; memory, planning, learning
Term
4 types of Neuroglia-CNS
Definition
Ependymal cells: cells with highly branched processes
Astrocytes: large cell bodies with many processes
Oligodendrocytes: smaller cell bodies with fewer processes
Microglia: smallest and least numerous neuroglia with many fine-branched processes
Term
Ependymal cells
Definition
Form epithelium called ependyma

Line central canal of spinal cord and ventricles of brain:
-secrete cerebrospinal (CSF) fluid
-have cilia or microvilli that circulate CSF
-monitor composition of CSF
-contain stem cells for repair
Term
Astrocytes
Definition
Largest and most numerous in CNS
Maintain the blood-brain barrier (isolates CNS)
Create structural framework for CNS
Repair damaged neural tissue
Guide neuron development
Control interstitial environment
-Regulate Na+, K+, CO2
-Transport nutrients
-Control blood volume through capillaries
-Absorb/recycle neurotransmitters
Term
Oligodendrocytes
Definition
Axolemma wrap around axons to form myelin sheaths
Membrane provides electrical insulation (myelin)
Increases speed of action potential, makes nerve look white
Term
Nodes (Nodes of Ranvier)
Definition
gaps between internodes where axons may branch
Term
Internodes
Definition
myelinated segments of axon
Term
Ependymocytes
Definition
a type of ependymal cell with cilia and microvilli to circulate the CSF.
Term
Tanycytes
Definition
specialized non-ciliated epedymal cells with microvilli.
Found in only one brain ventricle.
Term
Microglia
Definition
Least numerous and smallest
Migrate through neural tissue
Clean up cellular debris, waste products, and pathogens
Lineage of WBC (macrophage)
Term
2 types of neuroglia in the PNS
Definition
Neuroglia completely surround cell bodies and most axons of neurons in PNS.
1.Satellite cells
2.Schwann cells
Term
Satellite cells (amphicytes)
Definition
Surround neural cell bodies in ganglia
Regulate environment around neuron
Term
Schwann cells (neurilemmocytes)
Definition
Form myelin sheath (neurilemma) around peripheral axons
One Schwann cell sheaths one segment of axon, need manyi Schwann cells to sheath the entire axon.
Term
Demyelination
Definition
Progressive destruction of myelin sheaths
Loss of sensation and motor control-numb, paralyzed
-Heavy metal poisoning: damage neuroglia, demyelination. Axons deteriorate, irreversible.

Diptheria: bacterial infection, destroys PNS (Schwann cells), fatal paralysis

Multiple Sclerosis: affect optic nerve, brain, spinal cord; lose vision, speech, balance, general motor control

Guillain-Barre Syndrome: autoimmune disorder, may be triggered by a virus; demylination of PNS, weakness and tingling of legs, spreads to arms, affects breathing
Term
Wallerian degeneration
Definition
Schwann cells repair damaged nerves
1. Axon distal to the injury degenerates, macrophages move in and clean up the debris.
2.Schwann cells proliferate, form solid cellular cord, making path for new axon growth.
3.Axon begins growing, Schwann cells wrap in myelin
4. Axon may reestablish normal synaptic contacts; if grows off course or stops growing-no normal function
Term
Nerve regeneration in CNS
Definition
-many more axons involved
-astrocytes produce scar tissue, prevent axon growth across damaged area
-astrocytes release chemicals that block the growth of axons
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