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| The basic functional units of the nervous system. |
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Support and protect neurons.
Act as phagocytes
Help regulate the composition of the interstitial fluid |
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| What does the Central Nervous System consist of? |
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The brain and spinal cord.
Contains neural tissue, connective tissue, and blood vessels. |
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Process and coordinate:
sensory data: from in/outside body
motor commands:control or adjust peripheral organs
higher functions:intelligence, memory, learning, and emotion |
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| What does the Peripheral Nervous System consist of? |
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| All neural tissue outside the CNS |
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Deliver sensory information to the CNS
Carries motor commands |
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| Nerve fibers (bundles of axons) |
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Definition
Cranial nerves-connected to the brain
Spinal nerves-attach to the spinal cord |
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Afferent division
Efferent division |
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| Carries sensory information from PNS sensory receptors TO the CNS |
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Detect changes or respond to stimuli
May be neurons and specialized cells, complex sensory organs |
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Carries motor commands FROM the CNS to muscles, glands, and adipose tissue
These target organs are effectors.
Has both somatic and autonomic components |
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| Controls skeletal muscle contractions: voluntary and involuntary (reflexes) muscle contractions. |
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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" |
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| What does the efferent division consist of? |
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Definition
| The somatic nervous system (SNS) and the autonomic nervous system |
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| What does the autonomic nervous system consist of? |
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| The sympathetic division and the parasympathetic division. |
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Definition
contains a large round nucleus with a prominent nucleolus.
Cytoplasm: perikaryon
Cytoskeletan contains: neurofilaments and neurotubules
neurofibrils: bundles of neurofilaments |
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| Structure of a multipolar neuron |
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Definition
| Contains the cell body, several short, branched dendrites, a single long axon, ending in terminal branches called telodendria |
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| Major organelles of the cell body |
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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 |
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Definition
| Dense areas of RER and ribosomes that make neural tissue appear gray (gray matter) |
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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 |
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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 |
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| branches of a single axon |
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| the tips of telodendria (fine extensions of distal axon) |
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thick section of cell body
attaches to initial segment (base) |
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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 |
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| Expanded area of presynaptic neuron's axon which contains synaptic vesicles of neurotransmitters |
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| A synapse between a neuron and muscle |
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| Synapse between a neuron and a gland. |
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Definition
-chemical messengers released at presynaptic membrane
-affect receptors of postsynaptic membrane
-broken down by enzymes
-reassembled at synaptic knob |
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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 |
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Term
| Neurons are classified as ______, ______, _____, or ______ on the basis of the relationship of the dendrites to the cell body and the axon. |
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Definition
| Anaxonic, unipolar, bipolar, or multipolar |
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Found in brain and sense organs
No axon |
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one dendrite, one axon, with cell body between the two.
Found in special sensory organs
Are rare |
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Definition
The dendrites and axon are continuous, basically fused, the cell body lies off to one side.
Very long axons
Most sensory neurons |
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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 |
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Definition
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Definition
| Efferent neurons of the PNS |
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| Functions of Sensory neurons-afferent |
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Definition
Deliver information from sensory receptors TO the CNS
Monitor internal environment-visceral sensory neurons
Monitor effects of external environment-somatic sensory neurons |
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| Structures of sensory neurons |
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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 |
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| Types of sensory receptors |
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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) |
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Motor neurons-efferent
2 different systems |
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Definition
Somatic nervous system
Autonomic nervous system |
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Definition
-includes all somatic motor neurons that innervate skeletal muscles
-conscious control
-cell bodies lie in CNS, axons extend into periphery |
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Definition
| -visceral motor neurons innervate all other peripheral effectors: smooth muscle, cardiac muscle, glands, adipose tissue |
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| 2 groups of efferent axons |
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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 |
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| Collection of neural cell bodies that regulate autonomic nervous system, control peripheral effectors |
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Found mainly in the brain, spinal cord, a few in autonomic ganglia
Between sensory and motor neurons |
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| Functions of interneurons |
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Definition
-Distribution of sensory information
-Coordination of motor activity
-Involved in higher functions; memory, planning, learning |
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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 |
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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 |
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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 |
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Definition
Axolemma wrap around axons to form myelin sheaths
Membrane provides electrical insulation (myelin)
Increases speed of action potential, makes nerve look white |
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Definition
| gaps between internodes where axons may branch |
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Definition
| myelinated segments of axon |
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Definition
| a type of ependymal cell with cilia and microvilli to circulate the CSF. |
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Definition
specialized non-ciliated epedymal cells with microvilli.
Found in only one brain ventricle. |
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Definition
Least numerous and smallest
Migrate through neural tissue
Clean up cellular debris, waste products, and pathogens
Lineage of WBC (macrophage) |
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| 2 types of neuroglia in the PNS |
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Definition
Neuroglia completely surround cell bodies and most axons of neurons in PNS.
1.Satellite cells
2.Schwann cells |
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| Satellite cells (amphicytes) |
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Definition
Surround neural cell bodies in ganglia
Regulate environment around neuron |
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Term
| Schwann cells (neurilemmocytes) |
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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. |
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Term
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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 |
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Term
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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 |
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| Nerve regeneration in CNS |
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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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