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A&P ch. 11
Nervous system
47
Anatomy
Undergraduate 2
12/15/2013

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Term
Functions of the nervous system
Definition
Sensory input- information gathered by sensory receptors about internal and external changes
integration- interpretation of sensory input
motor output- activation of effector organs (muscles and glands ) produce a response
Term
Divisions of the nervous system
Definition
Central nervous system CNS- brain and spinal cord integration and command center
peripheral nervous system PNS- paired spinal and cranial nerves carry messages to and from the CNS
Term
Peripheral nervous system PNS- 2 functional divisions
Definition
Sensory (afferent) division- somatic afferent fibers- convey pulses from skin skeletal muscles and joints. Visceral afferent fibers convey impulses from visceral organs.
Motor (efferent) division- transmits impulses from the central nervous system to effector organs
Term
Motor division of the peripheral nervous system
Definition
Somatic (voluntary) nervous system- conscious control of skeletal muscles
Autonomic (involuntary) nervous system ANS- visceral motor nerve fibers. Regulates smooth muscle cardiac muscle and glands. 2 functional subdivisions sympathetic and parasympathetic
Term
Histology of nervous tissues- 2 principal cell types
Definition
Neurons excitable cells that transmit electrical signals. No route you Beliles house – supporting cells
Term
Astrocytes
Definition
Most abundant, versatile, and highly branched glial cells. Cling to neurons, synaptic endings, and capillaries. Support and brace neurons. Help determine capillary permeability. Guide migration of young neurons. Control the chemical environment. Participate in information processing in the brain.
Term
Microglia
Definition
Small ovoid cells with thorny processes. Migrate toward injured neurons. Phagocytize microorganisms and neuronal debris.
Term
Ependymal cells
Definition
Range in shape from squamous to columnar. Maybe ciliated – line essential cavities of the brain and spinal column. Separate the CNS interstitial fluid from the cerebrospinal fluid in the cavities
Term
Oligodendrocytes
Definition
Branched cells. Processes wrap CNS nerve fibers, forming insulating myelin sheaths
Term
Satellite cells
Definition
Surround neuron cell bodies in PNS
Term
Schwan cells (neurolemmocytes)
Definition
Surround peripheral nerve fibers and form Myelin sheaths. Vital to regeneration of damaged peripheral nerve fibers
Term
Neurons nerve cells special characteristics
Definition
Long-lived over 100 years or more. Amitotic with few exceptions. High metabolic rate – depends on continuous supply of oxygen and glucose. plasma membrane functions in: electrical signaling cell to cell interactions during development
Term
Cell body (perikaryon or soma)
Definition
Biosynthetic center of a neuron. Spherical nucleus with nucleolus. Well-developed Goldie apparatus. Rough ER called Nissl bodies (chromatophilic substance). Network of neurofibrils neurofilament's cytoskeleton. Ask on Hillach – cone shaped area from which axon arises. Clusters of cell bodies are called nuclei in CMS ganglia in the PNS
Term
Processes
Definition
Dendrites and exons. Bundles of processes are called tracks in the CNS nerves and the PNS.
Term
Dendrites
Definition
Short, tapering, and diffusely branched. Receptive input region of a neuron. Convey electrical signals towards the cell body as graded potentials
Term
The axon
Definition
One axon arising from the Axon hillock. Long axons nerve fibers. Occasional branches axon collaterals. Numerous terminal branches telodendeia. Numerous knob like axon terminals synaptic knobs or Boutons secretory region of a neuron release neurotransmitters to excite or inhibit other cells
Term
Functions of axons
Definition
Conducting region of a neuron. Generate and transmits nerve impulses action potentials away from the cell body. Molecules and organelles are moved along axons by motor molecules in 2 directions: anterograde – toward axon terminal retrograde retrograde towards the cell body
Term
Myelin sheath
Definition
Segmented protein lipoid sheath around most long or large diameter axons. It functions to: protect an electrically insulate the axon. Increase speed of nerve impulse transmission
Term
Myelin sheaths in the PNS
Definition
Schwan cells wraps many times around the axon. – Myelin sheath – concentric layers of Schwann cell membrane.
Neurilemma- peripheral bulge of Schwann cell cytoplasm. Nodes of Ranvier – myelin sheath gaps between adjacent Schwan cells sites were axon collaterals can emerge
Term
Unmyelinated axons
Definition
Then nerve fibers are unmyelinated. Slower transmission of impulses.
Term
Myelin sheath in the CNs
Definition
Formed by processes of Oligodendrocytes, not the whole cells. Nodes of Ranvier are present. No Neurilemma. Thinnest fibers are unmyelinated
Term
White matter
Definition
Dense collections of myelinated fibers
Term
Mostly neuron cell bodies and unmylenated fibers
Definition
Gray matter
Term
3 types of neurons structural classification
Definition
Multi polar, bipolar, Uni polar.
Term
Multi polar
Definition
1 axon and several dendrites. – Most abundant. Motor neurons and interneurons.
Term
Bipolar
Definition
One axon and one dendrite. Rare
Term
Uni polar (pseudo unipolar)
Definition
Single, short process that has two branches: peripheral process – more distal branch, often associated with sensory receptor. Central process – branch entering the CNS.
Term
Functional classification of neurons three types
Definition
Sensory afferent, motor efferent, interneurons association neurons
Term
Sensory neurons
Definition
Transmit impulses from sensory receptors towards the CNS
Term
Motor neurons
Definition
Carry impulses from the CNS to effectors
Term
Interneurons
Definition
Shuttle signals through CNS pathways most are entirely within the CNS
Term
Neuron function
Definition
Neurons are highly irritable. Respond to adequate stimulus by generating an action potential or nerve impulse. Impulse is always the same regardless of the stimulus
Term
Principles of electricity
Definition
Opposite charges attract to each other. Energy is required to separate opposite charges across the membrane. Energy is liberated when the charges move toward one another. If opposite charges are separated, the system has potential energy
Term
Voltage
Definition
Measure of potential energy generated by separated charge
Term
Potential difference
Definition
Voltage measured between two points
Term
Current (I)
Definition
The flow of electrical charge ions between two points
Term
Resistance (r)
Definition
Hindrance to charge flow provided by the plasma membrane
Term
Insulator
Definition
Substance with high electrical resistance
Term
Conductor
Definition
Substance with low electrical resistance
Term
Role of membrane ion channels
Definition
Proteins serve as membrane ion channels. Two main types of ion channels leakage non-gated channels always open and gated channels three types
Term
Three types of gated channels
Definition
Chemically gated like in gated channels – open with binding of specific neurotransmitter. Voltage gated channels – open and close in response to charges in membrane potential. Mechanically gated channels – opening clothes in response to physical D formation of receptors.
Term
When gated channels are open
Definition
Ions diffuse quickly across the membrane along their electrochemical gradients. Along chemical concentration gradient from higher concentration to lower concentration. Along electrical gradients toward opposite. electrical charge. – Ion flow creates electrical current and voltage changes across the membrane
Term
Resting membrane potential is generated by
Definition
Differences in ionic makeup of ICF and ECF. Differential permeability of the plasma membrane
Term
Differences in ionic makeup of resting membrane potential
Definition
ICF has lower concentration of sodium and chloride then ECF. ICF has a higher concentration of potassium and negatively charged proteins then ECF
Term
Differential permeability of membrane and resting membrane potential
Definition
In permeable to a minus. Slightly permeable to sodium through leakage channels 75 times more permeable to potassium more leakage channels. Freely permeable to chloride.
Term
Resting membrane potential
Definition
Negative interior of the cell is due to much greater diffusion of potassium out of the cell then sodium diffusion into the cell. Sodium potassium pump stabilizes the resting membrane potential by maintaining the concentration gradients for sodium and potassium.
Term
Membrane potentials that act as signals
Definition
Membrane potential changes when: concentrations of ions across the membrane change. Permeability of membranes ions changes. Changes in membrane potential our signals used to receive, integrate and send information.
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