Nervous System
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86 terms
Terms | Definitions |
|---|---|
 Three overlapping functions | sensory input; integration; motor output |
| Sensory input | gathered information and monitoring stimuli |
| Integration | processes and interprets the sensory input and then decides what needs to be done |
| Motor Output | the response to stimuli that is carried out by effector organs |
| Brain and Spinal Cord | CNS; integration and command center |
| Spinal nerves | paired nerves that carry impulses to and away from the spinal cord |
| PNS | peripheral nervous system; links all parts of the body to CNS |
| Cranial nerves | paired nerves that carry impulses to and from the brain |
| Afferent Division | conveys impulses to CNS |
| Somatic afferent fibers | from skin, muscles, joints |
| Visceral afferent fibers | from visceral organs of ventral body cavity |
| Efferent division | transmits impulses from CNS to effector organs-muscles and glands |
| Somatic Nervous system | voluntary nervous system |
| Autonomic Nervous system | involuntary nervous system |
| Sympathetic Division | mobilizes body systems during activity |
| Parasympathetic Divison | conserves energy |
| neurons | nerve cells that transmit electrical signals |
| Neuroglia | supporting cells; smaller cells that surround nuerons |
| Four types of neuroglia in CNS | astrocytes, microglia, oligodendrocytes, ependymal cells |
| Astrocytes | most abundant and versatile |
| Microglia | transform into macrophage to ingest debris/microorganisms; denies immune system access to CNS |
| Oligodendrocytes | form insulation called myelin sheath around thicker neurons |
| Ependymal Cells | line brain cavity to keep barrier between cerebrospinal fluid and the tissue fluid bathing cns cells |
| Two types of neuroglia in PNS | satellite cells; schwann cells |
| Satellite Cells | surround the cell bodies in PNS |
| Schwann cells | form myelin sheath in PNS |
| Characteristics of Neurons | conduct electrical nerve impulses; extreme longevity; amitotic; high metabolic rate |
| Plasma Membrane of a Neuron | site of electrical signaling and plays a part in cell to cell interactions during development |
| Neuron Cell body | most cell bodies are in the CNS |
| Dendrites | main receptive or input region; receives input from other neurons; conveys incoming messages towards the cell body |
| Axons | conducting region of the neuron; generates nerve impulse called an action potential and transmits them away from the body |
| Axons in the CNS | myelin sheath is formed by oligodendrocytes; no neurilemma; nodes of ranvier more widespread |
| White matter | mylinated fibers |
| Gray matter | cell bodies and unmylenated fibers |
| Myelin | whitish fatty tissue that covers long or large axons-does not cover dendrites |
| Myelinated fibers | conduct impulses rapidly |
| Functions of Myelin | protects and insulates axon fibers; increases speed of impulse transmission |
| Neurilemma | outermost layer of schwann cell |
| Nodes of Ranvier | gaps in myelin sheath |
| Unmyelinated fibers | covered by schwann cell but they are not coiled and do not forma myelin sheath |
| Multipolar neurons | most common type; major type in CNS |
| Sensory neurons | transmit impulses toward the CNS (afferent) |
| Motor neurons | transmit impulses away from the CNS (efferent) |
| Action potentials | nerve impulses; electrical impulses carried along the length of the axons; the underlying functional feature of the nervous system |
| Cause of Action Potentials | flow of ions across cellular membranes to cause electric current |
| Passsive or leakage membrane ion channel | always open |
| Chemically gated membrane ion channel | open with binding of specific neurotransmitter |
| Voltage gated channels | open and close in response to membrane potential |
| Mechanically gated channels | open and close in response to physical deformation of receptors |
| Potassium | plays the most important role in generating the membrane potential |
| Membrane potential | voltage across the membrane; cytosol has increased concentrations K ions than Na ions and there is a greater concentration of Na ions in extracellular fluid |
| Graded Potentials | short lived changes in membrane potential; sufficiently strong graded potentials can initiate action potentials and are critical to generation of action potentials |
| Axon hillock | where transition from graded to action potential takes place |
| Action Potentials | the principal means of neural communication |
| Nerve impulse | an action potential in the axon of a neuron |
| Four Stages of AP generation | Resting; Depolarization; Repolarization; Hyperpolarization |
| Resting State | All gated Na and K channels are closed; Na activation gates closed; inactivation gates open |
| Depolarization Phase | Na channels open |
| Repolarization | Na channels inactivating; K channels open; restores the resting electrical conditions of the neuron |
| Hyperpolarization | K channels remain open; Na channels resettling |
| continuous conduction | unmyelinated fibers; action potentials are generated at sites next to each other and conduction is relatively slow |
| salutatory conduction | myelinated fibers; action fibers are triggered only at the nodes and jump from one mode to the next |
| Threshold | a value depolarization must reach to generate an action potential |
| All or none phenomenon | action potentials either happen completely or not at all |
| absolute refractory period | enforces one way transmission of nerve impulses; A period of time following an action potential during which no additional action potential can be evoked regardless of the level of stimulation |
| relative refractory period | a period after firing when a neuron is returning to its normal polarize state and will only fire again if the incoming message (impulse) is stronger than usual; returning to arresting state |
| Synapses | a junction between neurons that mediates information transfer from one neuron to another neuron or to an effector cell |
| Electrical Synapses | less common than chemical synapses; ions flow directly from neuron to neuron; important in the CNS for arousal from sleep, mental attention, emotions, and memory |
| Chemical Synapses | specialized for the release and reception of neurotransmitters |
| Synaptic Cleft | fluid filled space separating presynaptic and postsynaptic neurons |
| Synaptic delay | time needed for neurotransmitter to be released, diffuse across the synapse, and bind to receptors |
| Excitatory postsynaptic potentials (EPSP) | graded potentials that can initiate an action potential in an axon; a singly EPSP can not induce an action potential; they must summate temporally or spatially to induce an AP |
| Inhibitory postsynaptic potentials | (IPSPs) graded post-synaptic hyperpolarizations, which decrease the likelihood that an action potential will be generated |
| Acetycholine | released at neuromuscular junction; released by all neurons that stimulate skeletal muscle; associated with voluntary movement |
| Biogenic Amines | plays a role in emotional behaviors and our biological clock |
| Excitatory neurotransmitters | cause depolarizations |
| Inhibitory neurotransmitters | cause hyperpolarizations |
| Channel linked receptors | mediate direct neurotransmitter action; very quick |
| G Protein linked receptors | responses are indirect, slow, complex, prolonged, and often diffuse |
| Neural Pools | functional groups of neurons that integrate incoming information and forward the processed information to its appropriate destination |
| Divergent circuit | one incoming fiber stimulates ever increasing number of fibers often amplifying circuits |
| Convergent Circuits | opposite of divergent circuits; resulting in either strong stimulation or inhibit |
| Reverberating | chain of neurons containing collateral synapses with previous neurons in chain |
| Parallel after-discharge | incoming neurons stimulate several neurons |
| Serial Processing | input travels along one pathway to a specific destination |
| Parallel Processing | input travels along several pathways |
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