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Plasma cell membrane
A flexible yet sturdy barrier that surrounds and contains the cytoplasm of a cell. Protects contents of cell, makes contact with other cells, and mendiates entry and exit of substances.
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Cytoplasm ( divided into two parts)
The contents that make up the cells interiour.
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Cytosol (cytoplasm)
The fluid portion of the cytoplasm that surrounds organelles, made up of 75-90% water plus other various components.
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Function of Cytosol
The site of many chemical reactions required for a cell's existence
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Organelles (cytoplasm)
Specialized structures that have characteristic shapes and perform specific functions in cellular growth, maintenance, and reproduction. There are 6 main components.
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Ribosomes (organelles)
Tiny organelles composed of a type of RNA and various proteins. Function - sites of protein synthesis
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Endoplasmic reticulum (organelles)
Extensive network of folded membranes that extends from the nuclear envelope throughout the cytoplasm. Function - it syntgesizes fatty acids and steroids and detoxifies drugs and other harmful substances.
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Golgi complexes (organelles)
3-20 flattend membranous sacs with bulging edges stacked on one another. Function - modify, sort, and package proteins for transport to different destinations. Forms lysosomes.
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Mitochondria (organelles)
Double-membraned organelle with a fluid filled space in between, referred to as the powerhouse of the cell. Function - site of ATP synthesis
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Lysosome (organelle)
A membrane enclosed vesicles that contains digestive enzymes. Function- digest worn - out organelles
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Cilia and flagella (organelle)
Motile hair-like projections containing microtubing. One moves fluid around the cell wilebthe othere moves the entire cell.
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Nucleus
A sherical or oval structure in the cell, most prominent feature of the cell. Functions - contains the hereditary factors called genes that controls cellular structure and directs activities.
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Neurons
Convert stimuli into nerve impulses (action potentials) and conduct these impulses to other neurons, muscle tissue or glands.
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Cell body (neuron)
Contains a nucleus surrounded by cytoplasm with tipical organelles.
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Dendrites (neuron)
Short, tapering and highly branched extentions off the cell body. Functions as the receving portion of a neuron
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Axon (neuron)
Long, thin, cylindrical projection that joins the cell body at a cone - shaped elevation. Function - propagates nerve impulses toward another neuron, muscle fiber, or gland cell.
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Axon hillocks (axon)
A small conical elevation that originates from the cell body.
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Axon collateral (axon)
Several side branches off the axon typically at a right angle.
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Axon terminals (axon)
The axon and its collaterals end into many fine processes.
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Synaptic end bulbs
The tips of some axon terminals swell into bulb-shaped stuctures.
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Synaptic vesicles
Are membrane enclosed sacs that store chemicals called neurotransmitters.
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Multipolar
Several dendrites and one axon (most neurons in the cns).
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Bipolar
One main dendrite and one axon on both sides of the cell body.
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Unipolar
Sensory neurons that originate in the embryo.
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Absolute refractory Period
A second action potential cannot be initiated, even with very strong stimulus.
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Membrane potential
electrical voltage difference across the membrane.
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Astrocytes
- Star-shaped, with many processes
- Provides nutrients to neurons
- Help form blood brain barrier
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Refractory Period
The period of time which an excitable cell cannot generate another action potential.
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Repolarizing Phase
- Resting membrane potential restored
- Slowing of Na+ inflow and increase of K+ outflow causes potential to change from +30 mV to 0 mV to -70 mV.
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Microglia
Protect CNS cells from disease by engulfing invading microbes.
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Resting membrane potential
Term used to describe voltage difference across membrane; average value is -70mV
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Oligodendrocytes
- Smaller than astrocytes, with fewer processes; round or oval cell body
- Forms supporting network around CNS neurons.
- Produces myelin sheath
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Depolarizing phase
- Threshold - when stimulus causes membrane to depolarize to a critical level, typically -55mV
- Inflow of Na+ causes potential to change from -55mV, passes 0mV and reaches +30mV
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Efferent(motor)
carry information out of the brain and spinal cord.
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Afferent (sensory)
Carry sensory information into the brain and spinal cord.
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After-hyperpolarizing phase
- Membrane potential drifts toward the potassium equilibrium potential (about -90mV).
- Return to -70mV occurs when K+ channels close.
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Ependymal
- epithelial cells arranged in a single layer, may be ciliated.
- Lines ventricles of the brain and central canal of the spinal cord
- Forms Cerebral Spinal Fluid and assists in circulat.
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Association(interneuron)
Processes sensory information by analyzing, storying and making decisions regarding appropriate responses.
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Relative refractory period
period of time during which a second action potential can be initiated, but only by a larger-than-normal stimulus
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Schwann Cells
- flattened cells that encircle the PNS axons.
- participates in regeneration of axons.
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satellite cells
- flattened cells arranged around the cell bodies of neurons in ganglia.
- Support neurons in PNS ganglia.
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