The release of calcium ions initiates muscle contractions. Watch this video (http://openstaxcollege.org/l/ calciumrole) to learn more about the role of calcium. (a) What are T-tubules and what is their role? (b) Please also describe how actin-binding sites are made available for cross-bridging with myosin heads during contraction.
34. Neurons and Nervous System (34.1) NS Consists of Neurons and Glia NS have two categories of cells: o Neurons generate and transmit electrical signals called action potentials o Glia provide support and maintain extracellular environment Neuron o Cell body o Dendrites: receive signals from other neurons o Axon: transmits signals to other cells o Axon hillock: signals are generated o Axon terminals: form synapses Synapse: gap where two neurons communicate o Neurotransmitters cross synapse to transmit signals 3 Stages of information processing o Afferent neurons (sensory) From sense receptors, send neurons to CNS o Interneurons Tell motor neurons to contract muscles o Efferent neurons (motor) Neural networks vary from simple to complex o Reflexes to active movement (34.2) Neurons Generate and transmit electrical signals Neurons have membrane potential (difference in electrical charge) across membrane o Action potential is a sudden large change in the membrane potential In a neuron that is not signaling, resting potential is appx. -60 millivolts o Inside cell is negative at rest Active transport proteins in the membrane create concentration gradients o Na+-K+ pump moves Na+ ions from inside exchanges for K+ from outside. Requires energy o Low -> high concentration (against conc