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Unformatted text preview: SAMPLE ESSAY QUESTIONS FOR FINAL EXAM 1. What is the difference between a sensory afferent neuron and a motor efferent neuron? Sensory (afferent) – carry impulse to the CNS Motor (efferent) – carry impulses from CNS Mixed – sensory and motor fibers carry impulses to and from CNS; most common type of nerve 2. Describe saltatory conduction and 2 advantages this type of conduction has over continuous conduction. Myelinated axons Myelin does NOT conduct electricity Insulator; prevents ion movement Electrical currents - only at the nodes of Ranvier High concentration of voltage-gated Na+ channels at nodes Action potentials JUMP from one node to the next Advantages : Smaller regions of membrane depolarize, etc. Less energy expended by Na+/K+ pump to reset RMP Increases speed of conduction 3. Name the 4 types of neuroglia in the CNS and a function of each. 1. Astrocytes-Support and brace neurons Anchor neurons to their nutrient supplies (capillaries) Control the chemical environment 2. Microglia-Phagocytes – protection from disease 3. Ependymal cells-Line the central cavities of the brain and spinal cord Produce CSF (cerebrospinal fluid) Cilia to help circulated CSF 4. Oligodendrocytes-Branched cells that wrap around axons of neurons Myelin – phospholipid covering, insulating function 4. What is the basis for the resting membrane potential (-70 mV)? 5. Define: depolarization, repolarization, hyperpolarization. What ion channels are responsible for these phases? Depolarization – the inside of the membrane becomes less negative Na+ permeability increases; membrane potential reverses Na+ gates are opened; K+ gates are closed Threshold – a critical level of depolarization (-55 to -50 mV) Repolarization – the membrane returns to its resting membrane potential Na+ gates close Voltage-sensitive K+ gates open K+ efflux results in return toward RMP Hyperpolarization – the inside of the membrane becomes more negative than the resting potential K+ gates remain open, causing an excessive efflux of K+ Hyperpolarization of the membrane 6. What is the difference between a chemically-gated ion channel and a voltage-gated ion channel? Chemically-gated channels Integral proteins – change shape to function as gates Restrict/allow movement – dependent on binding of a specific neurotransmitter Voltage-gated channels Integral proteins – change shape to function as gates Restrict/allow movement – dependent on membrane potential Electrical changes at the membrane change function of gate 7. Describe 2 differences between a graded potential and an action potential....
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This note was uploaded on 03/31/2008 for the course BIO 124 taught by Professor Tondi during the Fall '07 term at George Mason.
- Fall '07