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M5 Muscle Histology
| Question | Answer |
|---|---|
| basic task of muscle tissue (4) | movement, maintenance of posture, joint stabilaization, heat generation |
| 3 other tasks and defs of muscle tissues | 1. contractibility (to shorten, generating a pulling force) 2. Excitability (nerve fibers cause electrical impulses to travel to m fibers) 3. Extensibility (ability to stretch to the contraction of an opposing muscle) |
| 3 types of muscles | skeletal, smooth, cardiac |
| skeletal muscles def | attaches and moves skeleton; multitnucleate cells; striated; voulntary contractions |
| cardiac muscles and deff | heart; striated; involuntary contractions |
| smooth muscle def | walls of hollows; no striation; involuntary contractions |
| smiliarties between 3 muscles (3) | 1. cells called fibers bc theyre elongated; 2. contractions depend on myofilaments; plasma membrane called sarcolemma |
| how muscles attach to the bones (2) | 1. collagen from the epimysium extend beyond the muscle and forms the CT of the tendon; 2. the tendon then connects to the bone that the muscle is resonisble for moving |
| muscle fiber | each muscle cells called this |
| Endomysium | thin collagen layer that wraps around each cell |
| fascicle | bundle of muscle fibers |
| perimysium | each fascicle wrapped with another collagen layer |
| epimysium | each muscle is further wrapped in another collagen layer |
| sarcolema | plasma membrane of the muslce fiber |
| sarcopasmic reticulum | endoplasmic reticulum of a muscle fiber |
| t-tubules | from the pits in the sarcolema and allows a signal form the nervous system to get fown the sarcoplasmic reticulum; folded in areas of the sarcollemma in skeletal and cardiac miscles; allow signals to get down sarcolplasmic reticulum |
| myofibrils | are responsible for the appearance if stritations and several myofibrils are found in a muscle fiber |
| what do myofibrils contain? | myrofilaments- actin and myosin |
| actin | thinner myrofiilaments |
| myosin | thicker myrofilaments |
| how the skeletal muscles contract | "heads" on myosin touch actin; (called cross bridge); the head pulls on the active site, shortening the sarcomere; |
| cross bridge and contaction | cc= when the head touches the active site on the actin;;;; c= all sarcomeres shorten at the same time |
| sarcomeres; A and I bands? | A= thick, dark stripes |
| sarcomeres; H zone and Z disks | H zone= area between the ends of the actin;;; Z disks= a place to which the actin can be anchored... each sarcomere is in between 2 z disks |
| sarcomere contraction | myosin heads connect with actin active sites and pull ---> z disks come together ; this reduces the length of the sarcomeres, the H zone, and the length of the I bands |
| 3 things that stay the same during contraction | actin, myosin and A band |
| do actin and myosin contract? | no |
| what does the actin contains what 2 proteins? | troponin and tropomyosin |
| troponin | lies across the tropomyosin |
| tropomyosin | winds around the double helix actin molecules |
| how does the muscles stop contracting? (3) | the nerves stop sending messages; this removes the calcium ions; this hides the active sites in the actin |
| neurons | functional unit of the nervous system, a nerve cell |
| motor neurons | muscles controlled by nerves; specialzed neve cells designed to control skeletal muscles |
| axon | long processes that extend far away from the main body of the cell |
| neuromusclular junction | where the acon of a motor neuron reaches the perimysium of several muscles fibers, it branches off and each branch connects with an individual fiber |
| synaptic cleft | nerve cell does not actually touch the muscle fiber, the gap is called this |
| synapse | the space between a nerve cell and another cells |
| spresynaptic terminal | the end of the nerve cell |
| postsynaptic membrane | part of the muscle fiber where the synaptic celft ends |
| synaptic vesicles | hold acetylcholine (ACh) for the neuron |
| ACh | acetylcholine; a neurotransmitter |
| neurotransmitter | a chemical that travels across the synaptic celdt; allowing the neuron to communicate with another cell |
| what happens when ACh ocmes into contact with the membrane? | its signal causes the cell to contract |
| acetylcholinesterase | an enzyme that inactivates ACh, so that our muscles are not constantly contracting;; released by skeletal muscle |
| what happens in the absense of ACh | muslces relezes |
| how the muscle fiber relaxes | look on paper |
| summery of the steps on contraction | look on the paper |
| steps in muscle contraction? | look on paper |
| motor units | one motor neuron and all the muscle fibers it innervates(controls) |
| what is the amount of branching directly linked to inmotor units? reduces what? | with how finely the muscle is controlled; if one fiber out of 1000 contracts, all of them will at the same time if they are connected in the same motor unit; reduces muscle's precision |
| large and small motor untis found where? | L= large muscles, allwoing greater power or strength; s= found in our eyes |
| multiple motor unit summary? | look on paper |
| Calcium | from sar. reticulum;to actin; causes troponin to move out of the way and reeveal active site |
| action potential | muscle contraction starts; an electrical messgae that flows down the motor neuron, causing synaptic vesicles to travels to the membrane of the neuron and secrete ACh |
| is there partial muscle contraction for motor units? | no |
| all of nothing law of skeletal muscle contraction | motor unit muscles either all contract, or don't contract at all |
| subtthreshold stimulus | motor units can receive stimuli that are too small to cause an action potential ; no muscle contraction takes place |
| threshold stimulus | as the strength of the stimulus increases, it will eventually trigger one action potential |
| sub-maximal stimuli | atimulli of increasing strength that result in more action potentials |
| maximal stimulus | eventually, action potential will occur in every motor neuron of the muscle |
| summary of the motor units | as the original stimulus gets larger and larger, more actions potentials ravel down more motor units, causing more muscle fibers to contract. |
| muscle tone | the state of partial contraction in a muscle, even when the mucle is not being used |
| what do the motor units do during sleep | contracting and relaxing |
| how does a muscle lose muscle tone? atrophy? | the only way to lose muscle tone entirely is to sever the nerve to that muscle...atrophy - shrinking du eto the lack of use - will result |
| 3 ways ATP is generated in muscle fibers | aerobic respiration, if cells have rest periods between periods of high energy consumption, it can create a reserve ini the form of creatine phosphate; anaerobic respiration |
| aerobic respiration. how many ATP molecules? efficiency? | 3 steps where the oxygen and glucose produces energy to turn ADP + P into ATP; 36; takes a long time, so it is not efficient enough when cells need a lot if energy in a short amount of time; used in time of rest and endurance activities |
| anaerobic respiration | this only produces a net gain of 2 ATP's it is incredibly inefficient but quick eventually lactic acid build up causes muscle cramps and fatigue |
| 2. if cells have rest periods between periods of high energy consumption, it can create a reserve in the form of creatine phosphate | creatine phosphate + ADP --> creatine + ATP creatine gives up its phosphate to create ATP when a muscle cell can no longer make ATP, it will make creatine phosphate this retain is much quicker that aerobic respiration. this retain does not require ener |
| how much creatine phosphate does a cell have to sustain itself for how long? | 10-15 seconds |
Created by:
Ktfic
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