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Lecture 9
| Definition | Term |
|---|---|
| Functions of the Nervous System (List all 3) | 1. Receives 2. Integrates 3. Commands |
| consists of the brain and spinal cord | Central Nervous System (CNS) |
| consists of all the rest of the nervous system, composed of nerves and ganglia; it is functionally divided into sensory and motor divisions | Peripheral Nervous System (PNS) |
| a division of the PNS that carries signals from various receptors to the CNS; it is divided into somatic and visceral divisions | Sensory Division (Afferent) |
| carries signals from receptors in the skin, muscles, bones, and joints | Somatic Sensory |
| carries signals mainly from the viscera of the thoracic and abdominal cavities | Visceral Sensory |
| a division of the PNS that carries signals from the CNS to effectors that carry out the body’s responses; it is divided into somatic and visceral divisions | Motor Division (Efferent) |
| carries signals to the skeletal muscles which produces voluntary muscle contractions and autonomic reflexes | Somatic Motor |
| carries signals to glands, cardiac muscle and smooth muscle to produce visceral reflexes | Visceral Motor |
| the division of the ANS that tends to arouse the body for action but inhibits digestion | Sympathetic Division |
| the division of the ANS that tends to have a calming effect but it stimulates digestion | Parasympathetic Division |
| cells that carry out the communicative role of the nervous system; they have 3 fundamental properties that enable them to communicate with other cells | Neuron (Nerve Cell) |
| neurons respond to stimuli to the highest degree compared to other types of cells | Excitability |
| neurons respond to stimuli by producing electrical signals | Conductivity |
| when signals reach the end of a nerve fiber, the neuron secretes neurotransmitter that crosses the gap and stimulates the next cell | Secretion |
| a class of neurons that specializes in detecting stimuli such as light, heat, pressure, and chemicals and transmits this information to the CNS | Sensory Neurons |
| a class of neurons that lie entirely within the CNS and receive signals from many other neurons to carry out the integrative function of the nervous system; they make up about 90% of the neurons in the nervous system. | Interneurons |
| a class of neurons that send signals predominantly to effectors such as muscle and gland cells | Motor Neuron |
| the control center of the neuron which consists of a centrally located nucleus and organelles | Neurosoma (Soma) |
| thick processes that branch off the neurosomas of most neurons; they are the primary site for receiving signals from other neurons and are named for their bare branches of a tree in winter | Dendrites |
| a mound located on one side of the neurosoma from which the axon originates | Axon Hillock |
| a cylindrical process with extensive branching at its distal end; it is specialized for rapid conduction of nerve signals to points remote from the soma | Axon |
| an extensive complex of fine branches at the distal end of an axon | Terminal Arborization |
| the bulbous ends of each branch of the terminal arborization which forms a synapse with the next cell | Axon Terminals |
| a class of neurons that have one axon and multiple dendrites; this is the most common type | multipolar neurons |
| a class of neurons that have one axon and one dendrite; they are located in the olfactory cells of the nose, retina and sensory neurons of the ear | bipolar neurons |
| a class of neurons that have one single process leading away from the soma; they represent neurons that carry signals to the spinal cord for senses such as touch and pain | unipolar neurons |
| a class of neurons that have multiple dendrites but no axon; they communicate locally through their dendrites and do not produce action potentials | anaxonic neurons |
| cells that outnumber neurons at least 10 to 1 and serve to protect the neurons and help them function | neuroglia (glial cells) |
| a type of neuroglia that somewhat resembles an octopus with each arm reaching out and wrapping around nerve fibers to form myelin in the CNS | oligodendrocytes |
| a type of neuroglia that line the internal cavities of the brain and spinal cord and functions to produce CSF | ependymal |
| a type of neuroglia consisting of small macrophages that function to phagocytize and destroy microorganisms, foreign matter and dead nervous tissue | microglia |
| a type of neuroglia with a starlike shape and are the most abundant glial cell in the CNS; it has the most diverse functions of any glial cell | astrocytes |
| a type of neuroglia that functions to produce myelin in the PNS | schwann cells |
| a type of neuroglia that surrounds the somas in ganglia of the PNS and functions to provide insulation and regulate the chemical environment of the neurons | satellite cells |
| a spiral layer of insulation around a nerve fiber formed by oligodendrocytes in the CNS and Schwann cells in the PNS | myelin sheath |
| the name given for the production of myelin sheath which begins in the 14th week of development and proceeds rapidly in infancy and isn’t completed until late adolescence | myelination |
| the name of the gap in between segments of myelin sheath where there is no myelin | node of ranvier |
| the name of the myelin-covered segments from each node to the next | internodal segments |
| the short section of nerve fiber between the axon hillock and the first glial cell | initial segment |
| the collective name for both the axon hillock and initial segment which plays an important role in initiating a nerve signal | trigger zone |
| Conduction Speed of Nerve Fibers (List the 2 factors) | 1. Diameter of the fiber 2. Presence or absence of myelin |
| a difference in the concentration of charged particles between one point and another | electrical potential |
| the charge difference across the plasma membrane which is typically about -70 | resting membrane potential (RMP) |
| when voltage shifts to a less negative value which occurs when a neuron is stimulated and sodium channels open | depolarization |
| when voltage shifts to a more negative value making a neuron less sensitive and less likely to produce an action potential | hyperpolarization |
| a short range change in voltage, creating a wave of excitation that spreads out from the point of stimulation | local potential |
| A rapid up-and-down shift in voltage produced by voltage-gated ion channels in the plasma membrane | Action potential |
| if a stimulus depolarizes the neuron to threshold, the neuron fires at its max voltage, if threshold is not reached, the neuron doesn’t fire at all | All or None Law |
| the period of resistance to re-stimulation that occurs for a few milliseconds after an action potential when it is difficult or impossible to stimulate that region of a neuron to fire again | refractory period |
| a period of time in which no stimulus of any strength will trigger a new action potential | absolute refractory |
| a period of time in which it is possible to trigger a new action potential but only with an unusually strong stimulus | relative refractory |
| a traveling wave of excitation produced by self-propagating action potentials; it is like a burning fuse on a firecracker | nerve signal |
| a type of signal conduction that occurs in unmyelinated fibers in which there is an uninterrupted wave of electrical excitation all along the fiber | continuous conduction |
| a faster type of signal conduction that occurs in myelinated fibers in which the action potentials only occur at the gaps; it creates an impression that the nerve signal jumps from gap to gap | saltatory conduction |
| the neuron that releases neurotransmitter | presynaptic neuron |
| the neuron that responds to neurotransmitter | postsynaptic neuron |
| a 20 to 40 nm gap between the presynaptic and postsynaptic neurons | synaptic cleft |
| a type of synapse in which neurons communicate over a gap via neurotransmitters; they are the site of learning and memory, the target of many prescription drugs, and the site of action of addictive drugs | chemical synapse |
| molecules that are synthesized by a neuron and released when a nerve signal reaches an axon terminal; most are classified as small organic molecules that are released by exocytosis and bind to specific receptors on the receiving cell | neurotransmitter |
| the ability of neurons to process information, store and recall it, and make decisions; it is based on the postsynaptic potentials produced by neurotransmitters | neural integration |
| when a neurotransmitter depolarizes a postsynaptic neuron in the direction that makes it more likely to fire | excitatory postsynaptic potential (EPSP) |
| when a neurotransmitter hyperpolarizes the postsynaptic neuron making it more negative and less likely to fire | Inhibitory postsynaptic potential (IPSP) |
| the process of adding up postsynaptic potentials and responding to their net effect; it occurs at the trigger zone | summation |
| a type of summation that occurs when a single synapse generates EPSPs so quickly that each is generated before the previous one fades; it allows EPSPs to add up over time to a threshold voltage that triggers an action potential | temporal summation |
| a type of summation that occurs when EPSPs from several synapses add up to threshold at the axon hillock; the presynaptic neurons collaborate to induce the postsynaptic neuron to fire | spatial summation |
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