Repolarization refers to the change in membrane potential that returns it to a negative value just after the depolarization phase of an action potential has changed the membrane potential to a positive value. 41 . Hyperpolarization It inhibits action potentials by increasing the stimulus required to move the membrane potential to the action potential threshold. •Less Excitable 42 . Hypopolorization Smaller than normal stimulus could reach threshold potential and depolarize the cell. •More Excitable 43 . Does Low Potassium Cause Cell to be MORE or LESS Excitable? Why? Causes cell to be less Excitable, potassium (K+) is positivity charged. Having less potassium makes cell more negative or Hyperpolarized, requiring more stimulus to generate an action potential. 44 . Does high potassium cause cell to be MORE or LESS excitable? Why? Causes cell to be more excitable, potassium (K+) is positively charged and causes testing membrane potential to become less negatively charged requiring less than normal stimulus to generate an action potential. 45 . 5 Ways Cells Communicate 1. Contact Dependent 2. Autocrine 3. Paracrine 4. Synaptic 5. Endocrine 46 . Tight Junctions Tight junctions, also known as occluding junctions or zonulae occludentes (singular, zonula occludens) are multiprotein junctional complexes whose general function is to prevent leakage of transported solutes and water and seals the paracellular pathway.
47 . Gap Junctions Gap junctions are a specialized intercellular connection between a multitude of animal cell-types. They directly connect the cytoplasm of two cells, which allows various molecules, ions and electrical impulses to directly pass through a regulated gate between cells. 48 . Desmosomes Desmosomes are intercellular junctions that provide strong adhesion between cells. Because they also link intracellularly to the intermediate filament cytoskeleton they form the adhesive bonds in a network that gives mechanical strength to tissues. 49 . Paracrine Cell Communication Paracrine signaling is a form of cell signaling or cell-to-cell communication in which a cell produces a signal to induce changes in nearby cells, altering the behavior of those cells. 50 . Autocrine Cell Communication Autocrine signaling is a form of cell signaling in which a cell secretes a hormone or chemical messenger that binds to autocrine receptors on that same cell, leading to changes in the cell. 51 . 4 Basic Types of Tissue 1. Epithelial 2. Connective 3. Muscle 4. Neural 52 . 5 Types of Cellular Adaptation 1. Atrophy 2. Hypertrophy 3. Hyperplasia 4. Dysplasia 5. Metaplasia 53 . Atrophy 1. Shrinking in size such as skeletal muscle atrophy. Disuse atrophy, withdrawal of growth factors or hormones 2. Physiologic atrophy—thymus gland atrophies in childhood 54 . Hypertrophy 1. Enlarging of cells and thus the organ usually due to increased workload 2. Ex. Left ventricular hypertrophy, cells enlarge not multiply 3. Physiologic hypertrophy turns into pathologic.
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- Fall '17
- keisha lovence