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WVWC Nervous System
WVWC
| Question | Answer |
|---|---|
| Nervous system | employs electrical and chemical means to send messages very quickly from cell to cell |
| Three basic steps to nervous system coordination: | 1) Sense organs receive information about the environment and sends message to brain and spinal cord. 2) Spinal cord and brain process the information and determine the appropriate response. 3)Spinal cord and brain issue commands to muscles or glands. |
| Two major anatomical subdivisions: | Central nervous system – brain and spinal cord Peripheral nervous system – composed of nerves and ganglia … so, all the nervous system except the brain and spinal cord |
| Nerve | bundle of nerve fibers (axons) wrapped in fibrous connective tissue Emerge from the CNS through foramina of the skull or vertebral column and carry signals to and from other organs of the body. |
| Ganglion | Knotlike swelling in a nerve where the cell bodies of neurons are concentrated. |
| Peripheral nervous system is divided: | Sensory (afferent) division Motor (efferent) division |
| Sensory (afferent) division | carries stimulus info from various receptors to CNS. |
| Somatic sensory division | signals FROM skin, muscle, bones, joints |
| Visceral sensory division | signals FROM viscera of thoracic and abdominal cavities (heart, lungs, stomach, urinary bladder) |
| Motor (efferent) division | carries signals from CNS to the gland and muscle to get a response. Cells/organs that respond to commands from CNS are effectors. |
| Somatic motor division | signals TO skeletal muscles for voluntary contractions and involuntary muscle contractions … somatic reflexes |
| Visceral motor division (aka autonomic nervous system) | signals TO glands, cardiac muscle, and smooth muscle. We have no voluntary control here and the responses of this system and its effectors are visceral reflexes. |
| Autonomic nervous system: | Sympathetic division – arouses the body for action … increases heart rate and respiration, decreases digestion. Parasympathetic division – has a calming effect … slowing the heartbeat, but stimulates digestion. |
| Neurons | nerve cells |
| Universal Properties of Nerve Cells | Excitability, Conductivity, Secretion |
| Excitability | (irritability) – respond to environmental changes … stimuli |
| Conductivity | electrical signals are quickly conducted to other cells at distant locations |
| Secretion | when the electrical signal reaches the end of a nerve fiber, the neuron secretes a chemical neurotransmitter that crosses the gap and stimulates the next cell |
| Three Functional Classes of Neurons: | Sensory( afferent) Neurons, Inteneurons ( associated neurons), Motor ( efferent neurons) |
| Sensory (afferent) neurons | specialized to detect stimuli such as light, heat, pressure, chemicals. |
| Interneurons (associated neurons) | interconnect the incoming sensory pathway with the outgoing motor pathway of the CNS. |
| Motor (efferent) neurons | signal to effectors (muscle or gland cells) to carry out the body’s response to stimuli |
| Structure of a neuron: | Neurosoma, Neurofibrils, Axoplasm, Axolemma, Dendrites, Axon, Axon Hillock, Axon Collateral, Schwan Cell, Terminal arborization, Synaptic Knob, Synaptic Vessicles. |
| Neurosoma | cell body of a neuron |
| Neurofibrils | actin filaments, along with microtubules make up the cytoskeleton |
| Axoplasm | cytoplasm |
| Axolemma | membrane |
| Dendrites | thick processes that branch out to receive signals from other neurons. |
| Axon | single “nerve fiber” is long, relatively unbranched and specialized for rapid conduction of nerve signals. |
| Axon hillock | site where the axon originates |
| Axon collateral | branch off axon |
| Schwan cell (myelin sheath) | encloses the axon |
| Terminal arborization | complex of fine branches at the end of an axon |
| Synaptic knob | swelling that forms a junction (synapse) |
| Synaptic vessicles | filled with neurotransmitter. |
| Multipolar neurons | 1 axon + many dendrites |
| Bipolar neurons | 1 axon + 1 dendrite |
| Unipolar neurons | 1 process out of the soma that branches to the axon and dendrite |
| Anaxonic neurons | dendrites only?, no obvious axon |
| Neuroglia, or glial cells | are supportive cells that protect the neurons and help them function. |
| Presynaptic neuron | releases neurotransmitter |
| Postsynaptic neuron | responds to the signal of the neurotransmitter |
| Chemical synapses | neurons communicate by neurotransmitters |
| Neurotransmitters | More than 100 confirmed |
| Four Major Categories of Neurotransmitters | Acetylcholine, Amino acid, Monoamines, Neuropeptides |
| Acetylcholine | acetic acid + choline |
| Amino acid | glycine, glutamate, aspartate, GABA |
| Monoamines | animo acids without the –COOH group. Ex: catecholamines (epinephrine, norepinephrine, dopamine), histamine, serotonin |
| Neuropeptides | chains of 2-40 amino acids |
| Cholinergic Synapse | Employs acetylcholine as its neurotransmitter, |
| Neurotransmitter Junction | Nerve opens Ca2+ gates Ca2+ in knob triggers vesicle exocytosis, release of Ach Recycle and reload the vesicles Ach diffuses across cleft binds ligand-regulated ion gates that open so Na+ in and K+ later. Na+ depolarizes membrane= Post synaptic potenti |
| Cessation of the signal | Diffusion, Reuptake of neurotransmitter, Degradation in synaptic cleft. |
| Diffusion | Neurotransmitter escapes into nearby extracellular fluid |
| Reuptake of neurotransmitter | Synaptic knob reabsorbs amino acids and monoamines by endocytosis and breaks them down with monoamine oxidase (MAO) |
| Degradation in the synaptic cleft | AchE breaks down Ach into acetate and choline, which is reabsorbed into the synaptic knob for recycling into new Ach |
| Excitation of a neuron by a chemical stimulus | Ligand binds receptor Receptor-mediated gate opens to let Na+ inside Depolarization of the membrane |
| nodes of Ranvier. | Ions are exchanged with the ECF only at______ Ions diffuse quickly down the membrane of internodes. So, the action potentials occur only at the nodes |
Created by:
lorette_ca
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