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Chap 13 Synapses:-A synapse is the place where two neurons meet, which includes a small gap between the axon terminals of pre-synaptic membrane and the dendrites of the post-synaptic membrane (i.e. the synaptic cleft) and the post-synaptic membrane.-Electrical transmission:the cytoplasm of two neurons is connected via gap junctions, allowingthe ions of the action potential to conduct directly into the effector neuron. (faster, Bidirectional, excitory)-Chemical transmission:signals are sent between neurons via chemicals, called neurotransmitters, that bind to receptors on the post-synaptic membrane. (unidirectional, excitatory or inhibitory, plastic)-iClicker: Which is true of electrical synapses? A.They only respond to excitatory neurotransmitters.Chap 20 Muscle Contractions:Muscle is a tissue built of specialized contractile cells. There are two main categories of muscle:1) Striated muscle tissue has the appearance of alternating light and dark bands, which are collections of contractile proteins called sarcomeres. In vertebrates, the striated muscle makes up the skeletal(most) and cardiac muscle.2)Smooth muscle tissuealso uses contractile proteins, but they are not organized into sarcomeres, so it doesn’t have a striated appearance. In vertebrates, smooth muscle lines the blood vessels, gut, respiratory tract, etc.-Skeletal Muscles are Organized HierarchicallySkeletal muscle consists of multiple bundles of muscle fibersMyofibersare long, multinucleate, cylindrical cells, organized in parallelEach myofiber consists of many parallel myofibrilsEach myofibril is composed of repeated sarcomeresThe sarcomere is the fundemental unit of contraction, which consists of actin and myosin filamentsSkeletal muscle consists of multiplebundles of muscle fibersMyofibers are long, multinucleate, cylindrical cells, organized in parallelThe sarcomere is the fundemental unit of contraction, which consists ofactinand myosin filaments-Skeletal muscle fibers are subdivided into repeated 2 μm long striated sarcomeres with a z disk at each end.