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| composed of the skin and accessory organs, protects the body from invasion by harmful pathogens, chemicals, and ultraviolet lights. Also prevents water loss from the body and helps regulate temperature. |
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| outer, nonvascular layer of skin composed of stratified squamous epithelial cells |
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| specialized cells in the epidermis that produce melanin, which absorbs ultraviolet light and gives different humans different skin colors. |
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| located beneath the epidermis, composed of dense fibrous connective tissue. rich in collagen and elastin. |
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| develop in pocketlike folds of the skin near the tips of fingers and toes, grow from the white, half-moon region of epithelial cells at the base of the nail. |
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| produced only by mammals, grows in length when new cells are produced by cell division of the epidermal cells that form the root of the hair. Hair cells produce keratin as they are pushed farther from the root. |
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| oil-producing glands that grow out from the epithelium that surrounds a hair. their secretions lubricate the hair and skin. |
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| present in all regions of the skin. help regulate body temperature, because sweat absorbs body heat. |
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| also called hypodermis. composed of loose connective tisue and adipose tissue. thicker in women because they store more body fat than men. |
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| receives and interprets the millions of signals received from the environment. |
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| cells that carry electrical and chemical messages back and forth between the brain and other parts of the body |
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| specialized cells that support and nourish the neurons. they don't carry messages, but supply nutrients to neurons, repair brain after injury, and attack invading bacteria |
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| cells of muscles and glands that respond to neural signals. |
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| neurons or other cells that detect changes in conditions inside or outside the body. |
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| two main division of the nervous system |
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| CNS- central nervous system and PNS- peripheral nervous system |
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| peripheral nervous system |
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| network of nerves that radiates out from the brain and spinal cord extending throughout the body |
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| short extensions of neurons that send signals to the cell body |
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| nucleus and organelles of the neuron |
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| long wirelike body that conducts signals from the dendrites |
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| sensory, motor, and interneurons |
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| carry sensory input toward the cns |
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| carry information away from the cns toward effectors |
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| link sensory and motor neurons within the brain or spinal cord |
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| protective layer around axons in the pns, formed by neuroglial cells |
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| the neuroglial cells that make up the myelin sheath and wrap themselves around the axon |
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| cns tissue, white because of the myelin substance in the plasma in the schwann cells |
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| cns tissue w/no myelinated axons |
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| bundles of myelinated axons in the pns |
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| when myelinated axons of white matter are bundled together in the CNS |
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| spaces between the schwann cells that interrupt the myelin sheath, leaving tiny unmyelinated patches |
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| electrical charges that carry information along nerve cells |
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| the net negative charge inside the cytoplasm of the axon compared to the outside when the axon is not conductin and impulse. |
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| a protein in the cell membrane that actively transports sodium out of the cell and potassium into the cell. 3 Na+ out for every 2 K+ in. Maintains the difference in ions in the cell |
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| brief reversal of electrical charge of the axon that transmits a signal along the length of the axon. the more intense the stimulus, the more often the axon fires/begins an action potential |
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| if sodium rushing into the cell reaches a critical level, many of the sodium channels open and sodium floods the cell, quickly eliminating the charge difference across the cell. |
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| when potassium ions diffuse out of the cell, and the inside of the cell again becomes more negative than the outside. |
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| after an action potential, affected portion of the axon keeps sodium gates closed, preventing another action potential |
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| the region between 2 neurons |
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| the neuron transmitting the action potential |
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| the neuron in a synapse that receives the action potential |
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| chemicals that are released when an electrical impulse arrives at the terminal bouton of a nerve cell |
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| when neurotransmitter receptors on the presynaptic cell permit the neurotransmitter to reenter the cell, allowing the neuron that released the neurotransmitter to use it again |
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| stems from impaired function of acetylcholine |
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| an important neurotransmitter at nerve-muscle synapses |
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| an enzyme that breaks down acetylcholine, drugs that inhibit this enzyme temporarily improve mental function for alzheimer's patients. |
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| caused by malfunctioning of neurons that produce dopamine, which controls emotions and complex movements |
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| the process by which individual neurons sum up the overall message of contrasting inhibitory and excitatory signals. |
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| the process by which individual neurons sum up the overall message of contrasting inhibitory and excitatory signals. |
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