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BIO12 Textbook Questions Nerve Signals P417#1) CNS includes nerves of the brain and spinal cord. PNS consists of other nerves. PNS sends messages TO the CNS, which is the “control center”. Somatic, autonomic, sympathetic, parasympathetic Page 412 paragraph 5 Page 413 paragraph 1 P417 #2) Sensory neurons go TO the CNS. Motor neurons come FROM the CNS. Neuron, CNS, ganglia, receptors, effectors, afferent, efferent Page 413, paragraphs 3&4 P417#3) Dendrites- receives signal from receptor or other neuron Myelin sheath- insulates the neuron and prevents ion loss Schwann Cells- makes the myelin sheath Cell body- contains cell nucleus and holds other organelles Axon- carries nerve impulse from cell body toward the next neuron or effector Nodes of Ranvier, neurilemma Page 414 paragraphs 1&2 P417#4) Receptor recognizes a stimulus Sensory neuron receives impulse from receptor Interneuron connects sensory neuron directly to motor neuron (bypassing the brain and speeding up a response) Motor neuron relays impulse to an effector Effector makes a response Reflexes, involuntary Page 416, Figure 6 P417#5) Both neurons shown are motor neurons. So there must be two effectors involved in this reflex arc. If neuron I was severed, the muscle fibre (effector) would not contract, so there would be no muscle movement. The other response (hair standing up on end?) would still occur. Effector, response Refer back to page 416 to review reflex arc. This was an application question, though. P426#3) Unqual distribution of positively charged particles on either side of the membrane Ions, concentration, -70 mV P. 419, paragraph 2 P426#4) There are more Na+ ions outside the neuron than there are K+ ions inside the neuron. Diffusion, ion gates P. 419, paragraph 2 P. 419, paragraph 3 BIO12 Textbook Questions P426#5) Na+ gates open up and Na+ ions enter the cell, depolarizing it (ie… making it more positive on the inside of the cell) Permeable, depolarization P426#6) When the neuron is stimulated, the resting potential, which is negative, changes to become an action potential, which is temporarily positive. This happens because Na+ gates open up, Na+ rushes inside, changing the charge inside from negative to positive. Then the Na+ gates, close and K+ gates open up, letting out K+. This makes the potential return to negative. After this, the Na/K pump restores the K+ and Na+ concentrations to the resting state (refractory period) Resting potential, ion gates P. 418, Figure 2. P. 419, paragraphs 2,3 P426#7) Rather than a continuous impulse, the impulse “jumps” from one Node of Ranvier to the next. Jumping makes the impulse go faster. Schwann cells, Node of Ranvier Page 414, paragraph 2. P426#8) There is a threshold level of stimulus required to fire an action potential… the minimum amount required to open up Na+ ion gates. If this level is reached, the action potential happens . If not, it doesn’t at all. Threshold, all-or-none Page 422, paragraphs 2 & 3. P426#10) Area B shows the depolarization of the membrane… potential increases. This must be where the Na+ channels are open and Na+ is entering the cell. depolarization Refer to page 419, paragraph 3. Nerve Signals