BIOL 213 1st Edition Exam # 2 Study Guide Nervous System Pathway• Sensory input (SI)  Integration  Motor Output (MO)• SI (afferent): gather info. is called SI…think AS• Integration: where NS process and interprets SI and decide what should be done ateach moment• MO (efferent): NS causes a response (aka: MO) by activating effector organs…think MEDivisions of NS• Central NS consists of: brain & spinal cord• Peripheral NS consists of: spinal nerves (carry impulses to and from spinal cord), cranial nerves (carry impulses to and from brain)Neurons- Functional unit of NSDendrites- Characterized as twig-like- Are the main receptive or input regions- Receive info from other neurons- Convey/deliver incoming message toward cell body- The electrical signals are NOT action potential (long-distance signals of axons), but are incoming signals operating @ short-distance called graded potentials (GP) Axon- Each neuron has a single axon- axon terminals (AT)- when the impulse reaches AT, it causes NT (signaling chem. stored in vesicles there) to be released n2 the extracellular spaceNodes of Ranvier- Adjacent schwann cells/oligodendrocytes along an axon do NOT touch one another, so there are gaps in the MS called noR• Myelinated axon prevents the electrical message from conduction all along axon—that’s why you have MS along axon, it allows the message to skip from node to node (saltatory conduction)• Saltatory conduction allows for faster transmission Depolarization (DP), Repolarization (RP), & Hyperpolarization (HP)The terms DP and HP describe the mp change relative the rmp• DP is a reduction in mp• Ex. change from -70mV to -65mV• HP occurs with mp increases• Ex. change from -70mV to -75mVSynapse• Comm. btwn. 2 neurons begins when an electrical impulse call AP travel along axon of pre-s neuron toward AT• AP can’t cross synaptic space, when it reaches AT, it causes vesicle sacs to move towards & fuses with pre-s membrane of AT and dump NT into synaptic space.• NT cross the synaptic space into receptors on post-s…which can trigger an AP which thentravels along new neuron• NT, along with electrical signals, are the “language” of the NS—the means by which eachneuron comm. w/ others to process and send messages to the rest of the body• NT are classified chemically and functionally• Vesicles (which contain NT) from pre-s terminal is regulated by an external ion called Ca+2 (which ctrl vesicle and NT