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HA Ch. 12 (13)

Nervous System I: Nervous Tissue

QuestionAnswer
the nervous system is one of the ... yet... organ systems in the human body smallest...complex
nervous system includes all of the neural tissue in the body
the nervous system along with the ... controls and adjusts the activities of ... endocrine...the other organ systems in the body
chief functions of nervous system monitor, integrate, respond to information in the environment
CNS contains the brain and spinal cord
PNS contains nerves and ganglia
ganglia are all the nervous tissue structures external to the CNS
the nervous system receives..and dictates sensory inputs...motor outputs
2 functional divisions of the nervous system afferent and efferent
afferent = sensory
afferent division carries...from...through the sensory impulses...sensory receptors...PNS TOWARDS the CNS
efferent division = motor
efferent division carries...through...to the... motor impulses AWAY FROM the CNS...the PNS...effectors
effectors are muscles and glands
efferent is further divided into the somatic nervous system (SNS) and autonomic nervous system (ANS)
SNS provides voluntary control over skeletal muscle contraction
ANS provides automatic control involving regulation of smooth muscles, cardiac muscle, and glandular activity
types of sensory inputs and motor outputs are categorized as somatic, visceral, general, special, branchial, proprioception
somatic refers to the outer body
visceral refers to mainly the inner body
general widespread
special localized
branchial innervation refers to the motor innervation of pharyngeal muscle
proprioception refers to a series of senses that monitor the degree of strech in muscles, tendons, and joint capsules
proprioception, therefor, refers to sensing the positions and movements of the body parts
nervous tissue organization is comprised of neurons and supporting cells called neuroglia or glial cells
neurons are long-lived, non-dividing cells
each neuron has a cell body (soma) and cell processes (axons and dendrites)
neuron cell SOMA contains a nucleus surrounded by cytoplasm (nucleoplasm or perikaryon)
cytoplasm of neuron contains supportive neurofibrils, neurotubules, neurofilaments and chromatophilic (Nissl) bodies
Nissl bodies are concentrations of RER and free ribosomes
all neuron bodies are in the CNS except for those found in ganglia of the PNS
axon hillock is the specialized region of an axon which connects the initial segment of the axon to the cell body
axoplasm cytoplasm of axon which contains numerous organelles
collaterals side branches from an axon
terminal arborizations are a series of fine, terminal extensions which branch from the tip of the axon and end at the synaptic terminals
terminal bouton is the area where one neuron synapses on another
axolemma plasmalemma of an axon
ganglia (PNS) clusters of PNS neuron cell bodies
nerves (PNS) bundles of axons in PNS
most neurons have a # of branched dendrites which are receptive sites that conduct signals from other neurons TOWARD the neuron cell body
most neurons have one axon which generates and conducts nerve impulses AWAY from the neuron cell body
synapse is a functional junction between neurons at neuroeffector junctions
synapses function as a site of intercellular communication
synapses occur on dendrites, the cell body, or along axons (axodendritic, axosomatic, axoaxonic)
vesicular synapse = chemical synapse involving neurotransmitters
nonvesicular synapse = electrical synapse involving direct contract between cells
anatomically, neurons are classified by the number of processes issuing from their cell bodies (multi, bi, uni, pseudouni, anaxonic)(polar)
multipolar several dendrites and one axon
bipolar one dendrite and one axon
unipolar one process
pseudounipolar the dendrite and axon are continuous at one side of the cell body
anaxonic contains no distinguishable axon
functionally, neruons are classified according to the direction in which they conduct impulses (sensory, motor, interneruons)
sensory (afferent) neurons conduct impulses TOWARDS the CNS
motor (efferent) neurons conduct impulses AWAY from the CNS
interneurons (association neurons)lie in the CNS between sensory and motor neurons
there are non-neural supporting cells in the neural tissue which support, protect, nourish and insulate neurons
supporting cells of the nervous system neuroglia or glial cells
neuroglia of the CNS include astrocytes, microglia, ependymal, oligodendrocytes
astrocytes are the largest andmost numerous of the glial cells
astrocytes function in controlling the interstitial environment
astrocytes repair damaged neural tissue
astrocytes create a 3-D framework for the CNS
astrocytes guide neuron development
astrocytes maintain the blood-brain barrier which isolates the CNS from the environment
microglia phagocytic cells of the CNS
microglia cells engulf cellular debris, waste products and pathogens
ependymal cells cuboidal to columnar epithelial cells that line the central canal and ventricles of the brain
oligodendrocytes glial cells responsible for maintaining cellular organization in the gray matter and producting myelin to completely sheath areas of white matter
neuroglia or supporting cells of the PNS include schwann cells and satellite cells
schwann cells myelin forming cells that cover all peripheral axons, whether myelinated or unmyelinated
satellite cells enclose neuron cell bodies in the peripheral ganglia
satellite cells regulate the exchange of nutrients and waste products between the neuron cell body and the extracellular fluid
thick axons are myelinated
myelin speeds impulse conduction along axons
myelin sheath = a coat of supporting cell membranes wrapped in layers around the axon
the myelin sheath has gaps called nodes of ranvier
unmyelinated axons are surrounded by supporting cells but they are not wrapped by layers of myelin
a peripheral nerve (simply nerve) is a bundle of axons wrapped in CT in the PNS
each axon is enclosed by an endoneurium
each fascicle of axons is wrapped by a perineurium
the whole nerve is surrounded by the epineurium
nerves are organs because they contain more than one kind of tissue
reflexes are rapid, automatic responses to stimuli
reflexes can either be somatic or visceral
5 minimum number of elements in a reflext receptor, sensory neuron, integration center, motor neuron, effector
simple 3 neuron reflex arcs form the basis of the structural plan of the entire nervous system
sensory neurons enter the spinal cord dorsally
motor axons exit it ventrally
interneurons are the confined to the CNS
the nerves in the PNS consist of the peripheral axons of the sensory and motor neruson
cell bodies of motor neurons and interneurons make up the internal gray matter of the CNS, whereas the cell bodies of sensory neurons lie external to the CNS in sensory ganglia of the PNS
throughout most of the CNS the inner gray matter is surrounded by outer white matter
the extreme center of the spinal cord and brain is a fluid-filled hollow central cavity
Created by: handrzej