PreAssignment #11 The Nervous System Name: _______________________________ Section #: _______ 1) In order to organize the nervous system, we often use a functional approach. To better understand this, you need to have a few definitions worked out ahead of time. Please define each of the following terms so they make sense to you later: Central nervous system? Peripheral nervous system? Afferent versus efferent? Somatic? Autonomic? Visceral? Receptors? Effectors? 2) The functional unit of the nervous system is the neuron. Neurons are highly modified cells that generate and move electrical stimuli (APs) . They are insulated, fed, and repaired when damaged by ancillary cells called neuroglia (or just glial cells). Please properly label the following generic neuron and then write a simple function for each labeled region:

3) Neuroglia (or glial cells) are located in both the CNS and the PNS. Please write a general function for each of the following common forms of glial cells: a. Satellite Cells – b. Schwann Cells – c. Oligodendrocytes (“few dendrite cells”) – d. Astrocytes – e. Microglia – f. Ependymal Cells – g. Which two types of glia myelinate neurons? h. Which two types of glia regulate interstitial fluids? 4) After visiting the “Membrane Potential (RP)” assignment in the content area of D-2-L, answer the following questions: a. How many neurons on average are in a human brain? b. In a resting neuron, how does the charge on the inside of the cell in general compare to the charge on the outside? c. On average, what is the charge (in mV) inside the neuronal cell at resting potential? d. Which side of the neuronal membrane at rest has more K+ ions? More Na+ ions? e. Which type of “leak channel” is more common in neurons? f. If K+ ions were the only ions moving, what would be the charge inside the cell? g. What ions are always entering the cell to bring the charge back to -70mV? h. What membrane feature constantly compensates for the Na+ and K+ ion leakage?

All living cells have a membrane potential that varies from moment to moment depending on the interaction of the cell and the fluids surrounding it. In an unstimulated, resting neuron, the potential difference between the outside and inside of the cell is called the resting membrane potential. Pumps (active only) and channels (active and passive) constantly influence the differential across the membrane, an electrical charge that can easily be measured with a common voltage meter. 5) After visiting the “Generation of an Action Potential” and “Propagation of an Action Potential” assignments in the content area of D-2-L, answer the following questions: a. Where exactly do most action potentials originate on a neuron? b. Which channels open when a neuron reaches threshold, Na+ or K+? c. What two key events occur at +30mV? d. What happens in Phase #3 when K+ ions continue to exit a neuron? e. What 2 events make an axon insensitive (or refractory) to another stimulus? f. What does the term saltatory mean in English? g. Which channels are found in high concentration (Na+ or K+) within the Nodes of Ranvier? h. How fast can myelinated neurons move an action potential?

6) When a neuron receives a stimulus, it temporarily becomes more positive on the inside (a process called depolarization). Using active Na+/K+ pumps and allowing K+ ions to passively leak back out of the cell, the neuron can then go negative again (celled repolarization). Graded Potentials in an EEG occur when a stimulus is subthreshold, and not enough positives enter the cell. Action Potentials occur once a stimulus is large enough to reach threshold (the so called “all or nothing” principle) and the neuron is forced to respond. Compare graded and action potentials using the following characteristics:

Characteristic Graded Potentials Action Potentials Depolarizing (up) or hyperpolarizing (down)? All or nothing or local summation? Active or passive spread on cell? Does effect stay local or spread down neuron? Is there a refractory period? What human cells have this type of potential?

What exactly is a refractory period? What is the difference between continuous and saltatory conduction? 7) Neurons are often lined up in neuronal pathways called reflex arcs. Neurotransmitters released by the axon terminal buds of the first (or presynaptic) neuron either have excitatory or inhibitory effects on the next (or postsynaptic) neuron in the sequence. For each of the following chemicals, tell me whether their overall effects tend to create EPSPs (Excitatory Post-synaptic Potentials) or IPSPs (Inhibitory Post-Synaptic Potentials) in our brains. In other words, are they uppers (stimulants) or downers (depressants) when used?

Chemical EPSP or IPSP? Chemical EPSP or IPSP? Norepinephrine Caffeine GABA Marijuana Endorphins Alcohol ACh (skeletal muscles) Nicotine

8) In multiple sclerosis, there is intermittent and progressive damage to the myelin sheath of peripheral nerves. This results in poor motor control of the affected area. Why does destruction of the myelin sheath affect motor control? What does the name “multiple sclerosis” actually mean? What are the major symptoms of this disorder? What is the average life expectancy for folks with MS? 9) In infantile Tay-Sachs disease, a genetic malformation causes irreversible damage to the myelin sheath, and thus death of a child’s neurons. Where is the genetic mutation located? Which ethnic group tends to develop TS? How do we test an infant for the disorder? What are the major symptoms? 10) For a long time, historians thought that FDR (Franklin Delano Roosevelt) had polio since it was very common then and since newspapers reported that upon his death. Does polio attack the CNS or the PNS? What disorder do we now think caused his death? Does this more recently described disorder attack the CNS or the PNS? How do the symptoms of the 2 disorders differ from one-another?