Muscles: Muscular Tissue Flashcards
Muscle Tissue In Homeostatsis
Muscle tissue contributes to homeostasis by producing body movements , moving substances in body, aid in maintaining body temp. through making heat byproduct.
Muscle Tissue Types
- Skeletal Muscle
- Smooth Muscle
- Cardiac Muscle
Skeletal Muscle
Attaches to skeleton
- Stritaed Tissues (light and dark protein bands)
- Voluntary
- Mulinucleated around the outer sides: produce proteins needed for contraction
Cardaic Muscle
Only in heart
* Stirated Tissue
* Involutary and does autorythmic contraction
* Central Nucleus
* Intercalated discs
Smooth Muscle
Located on hollow walls of blood vessle, airways, organs, digestive
- Lack striations
- involutary
- Central nuclei
Functions
- Produce coordinated muscle movements relying on skeletal contraction/releaxing
- Skeletal Muscel contraction stablize joints and maintain body post.
- Storage is done through the rings of smooth muscle called sphincters prevent flow of contents ( cardaic contraction move blood through circulatory , smooth contractions move food through digestive and reprod, skeletal contractions promote lymph)
- Genereate heat: as a muscle tissue contracs it producues heat (thermogenesis)
Muscle Properties
- Electrical Excitability: respond to stimuli by promote action potentials. One is autorthymicity arsing from muscle itself other is chemical stmuli from neurotransmitters.
- Contractability: ability to contract stimuluated by action pot
- Extensibility: ability to strech, without damage
- Elasticity: ability to return to orignal length
Muscle Connective Tissue Components
- Muscle (organ)
- Fasicle ( 10-100 muscle fibers)
- Muscle (fibers or cells)
- Myofilaments (contractile organelles)
- Sacromeres (contractile units)
- Contractive (filaments: thick and thin)
- Contraction ( protein : actin and myosin)
Tissue Components
- Subcutaneus Layer: sepreate muscle and skin
- provides a passge for neverves , vessles, store fat
Three Layers Connective: - Epimyisum: desne irreg, surrond whole muscle
- Perimyisum: dense irre, 10-100 fibers and in bundles called fasicles
- Endomysium: penetrate inteieor of each fassicle, sperate each fiber. Elastic and retiuclar fibers and has three feautures
- Capillary network
- Myosatitlet cells
- neve fibers
Tendon and Aporneuorsis
All fibers that extend the muscle attach to periostenum (tendon)
Flat tendo sheet for attachment (Aponeurosis)
Microscopic Mucle Fiber
Muscle fibers: made of myofibrils
- Plasma membrane of muscle fibers: Sacrolemna
- Cytoplasma: sacroplasma
- Specicalized Smooth ER: Sacroplasmic reticlum (SR) stores and releases Ca ions
- Nuecli located beneath sacrolemna and produce proteins for contraction.
- Myoglobin: protein found in msucle that binds o2 and releases for ATP sythesis
Muscle Fiber Cell
Sacro= flesh
- Sacrolemna
- Sacroplasam
- Sacroplasmic reticulum ( specialized for initating contraction and store, release, reuptake calcium.
Myofibrils and Sacroplasmic Reticulum
Myofibrils: contractile organelle of skeletal muscle. Make muscle stritations and are made of many sacromeres.
1. Tranverse (T-tubules): small invagiantions of the sacrolemna and filled with interstial fluid to ensure all parts of muscle are activated during action pot.
2. Sacroplasmic Reticulum: fluid filled ystsem of membranous sacs that surrond the myofibril
- Like ER and have teriminal cisterns ( against the t-tubules forming a tirad)
In relaxed tissue the SR stores Ca+ , release of ions from teriminal cisterns casues muscle contraction
Filaments
Thick Filament: composed of myosin protein
Thin Filaments: protein actin, troponin, tropomyosin
- Thick and thin are involved in contractile processess
- 2 thin filaments for every 1 thick –> 2:1
Sacromere
A Band: darker middle part that extends the entire length of thick filaments (Thick - Thin)
I Band: lighter less dense that has rest of thin filaments
H Zone: area where there is no thin only thick: only thick when relaxed however during contraction thin over thick causing thick to be gone.
M Line: Center of He zone composed of proteins holding thick together
Z Disc: plate shaped that sepreate sacromeres
What are the Muscle proteins types
- Contractile Proteins: proteins that genrate force during muscle contraction
- Actin: thin filament- each actin has myosin binding site where the moysin head binds during contraction.
- Myosin: main part of thick filaments- consists of tail and two heads, bind to myosin site, ATP binding site - Regulatory proteins: proteins that switch contraction on and off.
- Tropomoysin: part of thin filament that when the muslce fibers are relaxed the tropomyosin covers the myosin-binding sites on the actin molcules to prevent myosin from binding.
- Troponin: part of thin filament that when calcium binds to troponin it changes shape, which removes tropomyosin from the myosin binding sites and muscel contraction begins as myosin binds to actin. - Stuctural Proteins: proteins that keep filaments in alignment and give myofibil elasticty and extensibility, liink myofibirl and sacrolemna to matrix
- Titin: connects z disc to m line ( line of sacromere, very elastic and gives extensibility to myofibirl)
- Actinin: protein of the z disc that attaches actin to the thin filament
- Myomesin: form m line of sacromere ( connects thick filaments together)
- Nebulin: wrap around entire length of thin filament and z disc
- Dytrophin: reinforce sacrolemma
Steps in Muscle Contraction Cycle
Initation of contraction: Ca+ is released from the sacroplasmic reticulum which binds to troponin
- Troponin changes shape
- Removes the tropomyosin from the myoisn binding sites
1. ATP Hydrolysis: Myosin head has an ATP binding site and a ATPase. ATPase hydrolyzes the ATP –> ADP + P and the reaction energizes the myosin head.
2. Attachement of Myosin to Actin Cross Bridges: Enegrized myosin head attaches to the myosin binding site and the hydrolyzed phopshate group is released.
3. Power Stroke: the site on the cross birdge where the ADP is opens and causes the cross-bridge to rotate and release APD. Rotation is towards the center of sacromere and thin flaments are pulled across the thick filaments.
4. Detachment of Myosin From Actin. The cross birdge remains attached until they bind to another ATP molecule. As ATP binds to the binding site , the myosin head relases from the actin.
Sliding Filament Mechanisum
- The myosin head attach and walk along the thin filaments at both ends of sacromere which pulls the thin filaments towards M-Line.
- Z-Disc comes closer together and the sacromere shortens , muscle fibers shortern and length shortens
What are the 5 Steps to Excitation - Contraction Coupling
1) At the neuromuscular junction, the ACH binds to receptor porteins on the sacrolemma , triggers an action potenitial (AP) in fiber.
2) AP moves down the sacrolema and T-Tubules
3) Ca+ are released: Action pot along the t-tubules causes voltage gatted sensitive protein gates to change shape. The change in shape allows calcium to move into cytosol
4) Calcium binds to troponin: troponin changes shape removing tropomyosin from myosin binding sites.
5) Contraction!
Describe the Neuromuscular Junction
Somatic motor neuron: stimuluate skeletal muscle contraction
Neurmuscular Junction: the synsape between somatic motor neuro and muscle fiber.
Synaptic Clef: small gap that sepereates the axon from the muscle cell.
Neurotransmitter: A chemical messanger that allows two cells to communicate
Axon terminal: end of motor neuron
Synaptic vesicles: contain many acetycholine for transport
Motor End Plate region of the sacrolemma that is opposte the bulb and has receptors
Junctional Folds: deep folds in motor plate to up surface area.
How a nerve impulse stimulates contraction?
1) Release of Acetycholine: when nerve impulse arrives at the NMJ, volate gated channels open and calicum ions flow inward based on the concentration gradient. - - The calcium stimulates exocytosis which causes synaptic vesicles to fuse with the plasma membrane of the motor neuron liberating the achetocholine into synaptic clef.
2) **Activation of Ach Receptors: **Binding two molceules of Ach to the receptor on the motor end plate opens an ion channel in the achetycholine receptor. Once open, sodium can move across the membrane.
3) Production of Muscle Action Potential: The inflow of sodium causes the inside of muscle fiber to become positive charged. The Action potential travels to the T-Tubules causing the sacroplasmic reticulum to release its storred calcium and initiate muscle contraction.
4) Termination of Ach Activity: Achetyocholine is broken down by acteylcholinestrase which is attached to collegen fibers in the matrix of snypatic clef.
