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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.
Cytoplasm ( divided into two parts)
The contents that make up the cells interiour.
The fluid portion of the cytoplasm that surrounds organelles, made up of 75-90% water plus other various components.
Function of Cytosol
The site of many chemical reactions required for a cell's existence
Specialized structures that have characteristic shapes and perform specific functions in cellular growth, maintenance, and reproduction. There are 6 main components.
Tiny organelles composed of a type of RNA and various proteins. Function - sites of protein synthesis
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.
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.
Double-membraned organelle with a fluid filled space in between, referred to as the powerhouse of the cell. Function - site of ATP synthesis
A membrane enclosed vesicles that contains digestive enzymes. Function- digest worn - out organelles
Cilia and flagella (organelle)
Motile hair-like projections containing microtubing. One moves fluid around the cell wilebthe othere moves the entire cell.
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.
Convert stimuli into nerve impulses (action potentials) and conduct these impulses to other neurons, muscle tissue or glands.
Cell body (neuron)
Contains a nucleus surrounded by cytoplasm with tipical organelles.
Short, tapering and highly branched extentions off the cell body. Functions as the receving portion of a 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.
Axon hillocks (axon)
A small conical elevation that originates from the cell body.
Axon collateral (axon)
Several side branches off the axon typically at a right angle.
Axon terminals (axon)
The axon and its collaterals end into many fine processes.
Synaptic end bulbs
The tips of some axon terminals swell into bulb-shaped stuctures.
Are membrane enclosed sacs that store chemicals called neurotransmitters.
Several dendrites and one axon (most neurons in the cns).
One main dendrite and one axon on both sides of the cell body.
Sensory neurons that originate in the embryo.
Absolute refractory Period
A second action potential cannot be initiated, even with very strong stimulus.
electrical voltage difference across the membrane.
- Star-shaped, with many processes
- Provides nutrients to neurons
- Help form blood brain barrier
The period of time which an excitable cell cannot generate another action potential.
- 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.
Protect CNS cells from disease by engulfing invading microbes.
Resting membrane potential
Term used to describe voltage difference across membrane; average value is -70mV
- Smaller than astrocytes, with fewer processes; round or oval cell body
- Forms supporting network around CNS neurons.
- Produces myelin sheath
- 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
carry information out of the brain and spinal cord.
Carry sensory information into the brain and spinal cord.
- Membrane potential drifts toward the potassium equilibrium potential (about -90mV).
- Return to -70mV occurs when K+ channels close.
- 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.
Processes sensory information by analyzing, storying and making decisions regarding appropriate responses.
Relative refractory period
period of time during which a second action potential can be initiated, but only by a larger-than-normal stimulus
- flattened cells that encircle the PNS axons.
- participates in regeneration of axons.
- flattened cells arranged around the cell bodies of neurons in ganglia.
- Support neurons in PNS ganglia.
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