BIOL 5600 Notes 1-28-16
BIOL 5600 Notes 1-28-16 BIOL 5600
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This 4 page Class Notes was uploaded by LaurenC on Wednesday February 17, 2016. The Class Notes belongs to BIOL 5600 at Auburn University taught by Dr. Mendonća in Winter 2016. Since its upload, it has received 52 views. For similar materials see Biomedical physiology in Biology at Auburn University.
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Date Created: 02/17/16
BIOL 5600 1-28-16 Muscle Physiology: -3 types are skeletal, smooth, and cardiac -Ways they differ: >Morphologically, in location, in type of control they are under, in how they are innervated/ what kind of neuro- connections they have 1) Skeletal -Muscle cells connected to the your skeleton -Voluntary control (you can consciously move/control) -Appearance is striated (banding pattern alternating dark and light bands) -Cells are fairly large in size -Multinucleate >Each cell is innervated by 1 motor neuron >Each cell has an axonal terminal going to it >This junction (axonal terminal of motor neuron with synaptic vesicles) is called a neuromuscular junction 2) Cardiac -Involuntary/unconscious control -Square shaped -Occur in sheets; adhere together by specialized gap junctions called intercalated disks (Only in skeletal muscle cells) -Striated with banding and an alternating light and dark pattern -Only one motor neuron for the sheet of cells -Wave of depolarization spreads via the gap junction -All cells are depolarized almost instantaneously -The idea of a wave… cells said to form “functional syncytium” >You only need to stimulate one cell to control all of them -Sheet of cells acts as one big cell 2) Smooth -Not striated; no banding A) Single cell smooth muscle cell -Ex. wrapped around a blood vessel -Described as multi-unit B) Single-unit muscle cell -Many cells -Visceral smooth muscle -Sheets united by gap junctions -Act like cardiac -Functional syncytium formed -Ex. influences contraction patterns -Involuntary control -Found in the wall of the uterus, wall of uterine -The innervation pattern depends >Each multi-unit has an axonal terminal >Each single unit sheet as one axonal terminal Skeletal muscle -Made of many individual muscle fiver that are bundled together -Sometimes attached to bond, sometimes attached to other muscles -Most of the time it is found in joins (2 bones, 1 muscle) with a tendon on either side (tendon is made of dense connective tissue) -Dense connective tissue also covers the “belly” of the muscle Structure from outside in: -Muscle -Connective tissue called epimysium (epimysium protects and prevents overstretching and helps with elasticity) -Tendon -Fascicles (each one is covered by perimysium, a continuation of the epimysium) -Individual skeletal muscle fibers covered by endomysium (continuation of perimysium) (holds blood vessels and nerve endings going to the individual cells) An individual muscle fiber is made of bundles of myofibrils -The myofibrils are made of myofilaments, which are the thin and thick filaments that create the light and dark bands >Thin filaments are made of mostly actin (the lighter areas) >Thick filaments are made of myosin (the darker areas) (myosin is a protein) -This striation is the functional arrangement -An element that allows contraction is the sarcomere -The sarcomere is the basic functional unit of skeletal and cardiac muscle -A “sarcomere” is the distance from z-line to z-line -The z-line serves as an attachment point for thin filaments -The M-line serves as an attachment point for thick filaments Contraction -Cell shortens and thickens -The z-lines get closer together -Sarcomeres shorten -Thin filaments are almost touching -You have to have this arrangement to maximize the tension/fore that is generated by the cell >In the overall cell, the thick portion stays the same length and the thin portions narrow -Contraction increases the overlap between thin and thick filaments A band -The length of the thick filament -No change is size I band -Where you only see thin filaments -No overlap with thick filaments -Relative lengths due to changes in width H zone -Where you only see thick filaments -No overlap with thin filaments Contractions cause increase of overlap between thin and thick filaments H zone and I band become very narrow Cardiac muscle cells -Also striated -Have thin/thick filaments -Have sarcomeres *Sliding filament theory of muscle contractions Other molecules involved: -Thin filaments >Made of actin, tropomyosin, and troponin -Thick filaments >Made of myosin Molecules that help with alignment (accessory molecules) o Titin -Huge elastic molecule (25 thousand amino acids long) -Stretches from z line to m line -Stabilizes thin/thick filament arrangement -Holds thick filaments appropriately in the myofibril -Contributes to passive elasticity of myofibril >Helps cell regain shape o Nebulin (vital role) -Spans entire length of thin filament -Thought to align the tin filaments, though not exactly sure of actual purpose o Diptrophin -Anchors the myofibrils to the fiber cell membrane There is normally not much Ca2+. So if you increase Ca2+, it binds to troponin and changes the configuration -Important in contraction
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