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The Nervous System: Neural Tissue I. Organization of the nervous system A. Functions of the nervous system 1. _____________________________________________________________ ___________________________________________ 2. _____________________________________________________________ ___________________________________________ 3. _____________________________________________________________ ___________________________________________ B. Two divisions 1. __________________ Nervous System (CNS) – __________________ & ____________________________________ 2. __________________ Nervous System (PNS) – part of the nervous system __________________ the CNS a. __________________ nerves – carry impulses to & from the __________________ b. __________________ nerves – carry impulses to & from the _____________________ C. Functional Classification of Neurons 1. __________________ (afferent) neurons – carry impulses from __________________ towards the __________________ a. __________________ – sensitive to stimuli that occur __________________ the body (sense of touch, sight, taste, etc.) b. __________________ – respond to stimuli __________________ the body & monitor changes in the blood, body temp., etc.) 2. __________________ neurons (interneurons) – lie __________________ sensory & motor neurons in the CNS and __________________ incoming & outgoing signals. 3. __________________ (efferent) neurons – carry impulses __________________ from the CNS and to effectors (muscles or glands) D. Two types of Neural Cells 1. __________________ – carry __________________ 2. __________________ cells – __________________ cells for the neurons a. __________________ – __________________ cells that __________________neurons from __________________ microorganisms. b. __________________ – __________________cells that connect neurons to __________________ and help exchange nutrients between capillaries and neurons. c. ____________________________ – cover the fibers of the __________________ neurons with __________________ __________________. 1 d. ____________________________– cover the fibers of the __________________ neurons with __________________ __________________. E. Neuron Structure 1. __________________ - cell body a. contains all organelles except centrioles (thus neurons are not able to reproduce) b. __________________ __________________– complex rough ER network with many ribosomes. 2. __________________ – typically shorter processes that convey impulses toward the soma. 3. __________________ – longer process (up to __________________) that conveys signals away from the soma. a. Each neuron will have only _________ axon, however it may be __________________. b. At the end of the axon will be __________________ __________________ (AKA - synaptic knobs or synaptic boutons). c. Some axons will be covered by white, fatty insulation called a __________________ __________________. Myelin sheaths increase the speed of impulse transmission. 1) White matter in the brain consists of __________________ fibers 2) Gray matter consists mainly of __________________ fibers. d. The spaces between the myelin sheaths are called __________________of __________________. F. Structural Classification of Neurons 1. __________________ – have a __________________ process that emerges from the cell body. Functions mainly as an axon for the _____________. 2. __________________ – have __________________ processes- one axon, one dendrite. Found in the __________________ of the eye and the __________________ mucosa. 3. __________________ – have __________________ (at least 2) dendrites and one axon. Most __________________ neuron in the body. II. Neurophysiology A. Nerve cells are able to transmit signals due to their properties of 1. __________________ – responding to a __________________ 2. __________________ – able to __________________ an impulse down its __________________ B. The Electrochemical gradient & the Resting Potential 1. The __________________ for an impulse is supplied by the __________________. 2. Neurons create a __________________ __________________ between the __________________ and the __________________ of the cell membrane (Potential difference). 2 3. This chemical imbalance allows the __________________ charge to travel __________________ the __________________ of the __________________. 4. __________________ along the cell membrane, called __________________ __________________ __________________, actively transport __________________of the cell & __________________the cell. 5. The build-up of Na outside the cell & K inside the cell makes the __________________ __________________. 6. Because the Na & K ions have different __________________, an electrical __________________ exists between the inside & outside of the cell membrane. 7. The __________________ __________________of a “charged” or __________________axon is _______ mV. (The inside is negative relative to the outside) C. The Acton Potential 1. The transmission of an impulse down the length of an axon is called the __________________ __________________. 2. A stimulus is applied to a __________________ membrane, which causes the membrane to become __________________ to Na. 3. Since there is a high concentration of Na outside the cell, the Na rushes in and changes to ionic differential to a more positive level (about ________ mV) called __________________. 4. The __________________ of a membrane at a certain area stimulates neighboring region of the membrane and causes it to depolarize. (This causes a __________________ __________________down the length of the membrane). 5. The impulse is always the same __________________ and only __________________ one way. D. Repolarization 1. Within ________, the Na gates have __________________ and K gates have __________________ to allow for K to flow out of the cell. 2. The loss of K helps to restore the axon to the Resting Potential of –70 mV. (__________________) 3. The Na/K pumps are then __________________ to restore normal Na & K levels. E. Stimuli for Depolarization 1. The minimum stimulus needed to trigger a depolarization and an impulse is called a __________________ __________________. 2. The _______ – _____ – ________ ________ says that action potentials will happen completely or not at all. 3. All action potentials are alike no matter the __________________ of the stimulus. 4. __________________ of impulse transmission is what separates __________________ from __________________ stimulus. 3 5. Stimuli not strong enough to trigger depolarization are called __________________ stimuli. 6. Subthreshold stimuli can be __________________ to cause depolarization. 7. Suprathreshold stimuli trigger only a __________________ action potential. 8. The __________________ __________________ __________________ is the period of time when the Na gates are open & a second stimulus can NOT come down the axon – no matter how strong it is. 9. The __________________ __________________ __________________ is the time immediately after the Na gates close and repolarization is still occurring that a exceptionally strong stimulus may cause depolarization. F. Impulses 1. Impulses travel at different speeds based upon the a. __________________ of the axon b. degree of __________________ 2. __________________ axons (which are usually longer as well) carry impulses __________________ than smaller axons. 3. __________________ axons carry impulses __________________ than unmyelinated axons. a. Myelin sheaths have spaces between them (about 1mm apart) called __________________ __________________. b. The current can only be carried at these nodes, thus the impulse has to “__________________” the myelin sheath. This is called __________________ __________________. 4. Speed of Impulse Conduction a. Large, myelinated = __________________ b. Medium, lightly myelinated = __________________ c. Small, unmyelinated = __________________ III. The Synapse A. Synapse structure 1. __________________ occur __________________ the __________________ of one cell and the __________________ of the next cell 2. __________________ __________________– neuron conducting impulses towards the synapse a. The end of the axon terminates (or ends) in a __________________ or __________________. b. The knob contains many tiny sacs called __________________ __________________ that contain a __________________. 3. __________________ __________________– neuron conducting impulses away from the synapse a. The end of the dendrite has a __________________ membrane. b. The membrane bears __________________ __________________. 4. __________________ __________________– space between the synaptic knob & the receptor membrane__________________ wide 4 B. Synaptic transmission 1. When the impulse reaches the axon terminal (knob), __________________ of the presynaptic membrane causes __________________ of the neurotransmitter into the synaptic cleft. 2. The neurotransmitter binds to the __________________ receptors, which causes Na ion gates to open and local __________________ to occur. 3. Neurotransmitters – two classes 1. __________________: Acetylcholine (_______), Norepinephrine, Dopamine, etc. 2. __________________: Gamma-aminobutyric acid (________), Glycine, etc. C. Termination & reabsorption of neurotransmitters 1. The neurotransmitter will continue to __________________ the receptors as long as they are __________________. The neurotransmitters must be __________________ in one of three ways. a. Chemical breakdown (__________________ [AChE]) b. __________________ of the neurotransmitter by the presynaptic membrane c. __________________ away from the synapse IV. Neural Disorders A. __________________ __________________ (MS) 1. __________________ disorder that __________________ the myelin sheaths of the axons of the optic nerve, brain, &/or spinal cord. 2. Characterized by __________________, __________________, __________________, and __________________ coordination problems. 3. It starts at __________________, is progressive & there is no __________________ B. __________________ 1. __________________ infection that kills the motor neurons of the spinal cord & brain 2. The dependant motor units become _______________ and _____________. 3. __________________ programs have all but eliminated this disease. C. __________________ 1. __________________ infection of the __________________ that is transmitted by __________________ animals. The virus is absorbed through the __________________ knob and is carried by the axons up to the CNS. 2. __________________ __________________symptoms include headache, nausea & muscle pain. __________________ __________________symptoms include hallucinations, muscle spasms, and difficulty swallowing that cause saliva buildup in the mouth (foaming at the mouth). __________________ & __________________ soon follow. 3. __________________ consists of a series of injections that contain antibodies, which must begin almost __________________. W/o treatment, rabies is always __________________. 5