Muscle Tissue - Mace: exam 2 Flashcards
What type of muscle has striations?
Skeletal muscle and cardiac muscle
What type of muscle is unbranched?
Skeletal and smooth muscle
What type of muscle is multinucleated?
Mostly skeletal muscle
What type of muscle has intercalated discs?
Cardiac muscle
What is the function of intercalated discs?
Allows for functional syncytium(allows for low resistance ion movement)
What types of muscle is unbranched?
Skeletal muscle and smooth muscle
In what type of muscle cells is the nucleus pushed to the side of the cell?
Skeletal muscle
Order the following from innermost to outermost. Perimysium Endomysium Epimysium
Endomysium Perimysium Epimysium
What are the functions of skeletal muscle?
Body movement Maintenance of posture Protection and support Storage and support Heat production
What is a fasicle?
A bundle of muscle cells
What type of connective tissue are the following tissues composed of? Epimysium Perimysium Endomysium
Epimysium- dense irregular CT Perimysium- Dense irregular CT Endomysium - Areolar CT
Tendon is composed of what type of CT?
Dense regular CT
Individual muscle cells are separated by _____.
Endomysium
What is a fascicle?
A bundle of muscle cells
Fascicles are separated by ______.
Perimysium
Intercalated discs are composed of _____ and ________.
Desmosomes and gap junctions
Gap junctions allow for what important function?
Allows for ion movement between cells, allowing the heart to work as a functional syncytium.
What is the primary function of desmosomes?
Holding cells together
What types of muscle are under involuntary control?
smooth and cardiac muscle
Tendons are composed of what type of CT?
Dense regular CT
A thin flattened sheet of tendon with a wide area of attachment is called a _______.
Aponeurosis
Tendons and aponeuroses are made of how many layers of connective tissue?
3 - the endomysium, perimysium, and epimysium continue into tendons.
Deep fascia is made of what type of connective tissue?
Dense irregular CT
What is the difference between hypertrophy and hyperplasia?
Hypertrophy is an increase in the size of individual cells. Hyperplasia is an increase in the number of cells.
Does weight lifting cause hypertrophy or hyperplasia?
Hypertrophy
Do skeletal muscle cells have one nucleus or multiple?
Multiple
What is the function of satellite cells in skeletal muscle?
Differentiate for repairing injured muscle cells
What is the sarcolemma?
Muscle cell membrane
What are T-tubules?
Deep invaginations of the sarcolemma for transmitting nerve impulses from the sarcolemma inwards
What are terminal cisternae?
Dilations ends of sarcoplasmic reticulum that serves as a reservoir for calcium ions
What is a triad in a muscle cell?
T tubule with terminal cisternae on the sides
What is the sarcoplasmic reticulum?
A tubular network surrounding contractile proteins made of modified smooth endoplasmic reticulum.
Functions of myoglobin?
Allows muscle cell to store oxygen
What are myofibrils?
contractile proteins, composed of thin and thick myofilaments.
Myofibrils occupy what percentage of total cell volume?
80%
Thick filaments are composed of what?
Myosin - a protein with a globular head and elongated tail
Thin filaments are composed of what?
G (globular) actin and F (filamentous) actin.
Tropomyosin
Troponin
Explain the arrangement of molecules in the thin filaments.
G actin with F actin spiraling around it. Tropomyosin is bound to F actin and troponin is bound to tropomyosin.
What happens to thin filaments when Ca++ binds to troponin?
Binding of troponin causes conformational shift in tropomyosin which exposes the myosin binding sites on F actin.
What is the functional unit of muscle?
The sarcomere
What separates sarcomeres?
Z discs
Define the following terms: I band A band H zone M line
- I band - Region containing only thin filaments
- A band - central region of sarcomere, contains entire thick filament and partially overlapping thin filaments
- H zone - Central portion of A band containing only thick filaments
- M line - Protein meshwork structure at center of H zone
What color are I bands and A bands under a microscope?
I bands are light A bands are dark
T/F? Each muscle cell has only one neuromuscular junction
True
Neuromuscular junctions are composed of what structures?
Synaptic knob, motor end plate, synaptic cleft
Explain how the synaptic knob functions up to the point of ACh release.
Nerve signal causes voltage gated calcium channels to open. Calcium enters synaptic knob and binds to synaptic vesicles, which leads to exocytosis of synaptic vesicles containing ACh
The synaptic cleft contains what enzyme? What is its function?
Acetylcholinesterase Breaks down ACh molecules after they’re released into synaptic cleft
How does the binding of ACh by the motor end plate start an action potential?
Binding of ACh opens Na+/K+ channels on the motor end plate, creating an end plate potential (EPP). EPP triggers action potential which propagates along sarcolemma and T tubules. Action potential causes opening of Ca2+ channels leading to cross bridge cycling.
Cross bridge cycling is responsible for the contraction of the muscle. Explain how it works.
Ca++ enters muscle cells, and binds to troponin. This causes conformational shift of tropomyosin and myosin binding sites become exposed. With myosin binding sites exposed, myosin heads on thick filaments bind to the thin filaments. Myosin heads swivel and causing thin filaments to be pulled past thick filaments. Myosin heads bind ATP and release from thin filaments ATPase breaks ATP down into ADP and Pi, which provides the energy to reset the myosin heads.
Why aren’t H bands present on microscopy when muscle is contracted?
Thin and thick filaments are overlapping so H band is not visible.
Explain the process of skeletal muscle relaxation.
AChesterase hydrolyzes ACh in synaptic cleft. Without ACh, no further action potential is generated. Ca++ channels close and Ca++ is pumped back into SR. Without Ca++ in cells, tropomyosin returns to its position covering myosin binding sites.
Dantrolene is a drug that causes decrease in muscle spasticity. How does it work?
Interferes with release of Ca++ from SR.
Succinylcholine is a drug used for surgery and intubation because it causes flaccid skeletal muscle paralysis. How does it work?
The drug binds to ACh receptors, but does not produce the effect of ACh, preventing the muscle from generating an action potential. AChesterase cannot break down the drug.
In what ways can muscles produce ATP in order to work?
Phosphagen system Glycolysis Oxidative phosphorylation
Rank the following from fastest to slowest in terms of energy production. Phosphagen system Glycolysis Oxidative phosphorylation
Phosphagen system - 5-6 seconds Glycolysis - 50-60 seconds Oxidative phosphorylation 5-6 minutes
Which modes of skeletal muscle metabolism are anaerobic? Aerobic?
Phosphagen system - anaerobic Glycolysis - anaerobic Oxidative phosphorylation - aerobic
Which mode of skeletal muscle metabolism is most efficient?
Oxidative phosphorylation
Power of muscle contraction is determined by what factor?
Muscle fiber diameter
Speed of muscle contraction is determined by what factor?
Slow or fast twitch muscle fibers
Fast twitch muscle fibers use what type of metabolism?
Anaerobic (phosphagen system or gylcolysis)
How many ATP are produced per glucose in glycolysis vs oxidative phosphorylation?
Glycolysis - 2 ATP per glucose Oxidative phosphorylation - 34 ATP per glucose
What type of metabolism would you expect slow twitch muscle fibers to use?
Oxidative phosphorylation
What type of muscles do you expect to be well vascularized? Why?
Slow twitch because they use aerobic metabolism so they need a good supply of oxygen from the blood
What type of muscle is the most red in color? Why?
Slow twitch because it has higher concentration of myoglobin because myoglobin is used to store oxygen
What is isometric contraction?
Muscle contracts and shortens, but the angle of the joint does not change.
What is isotonic contraction?
Muscle contracts and shortens overcoming the load, joint angle changes
What are the two types of isotonic contraction? Describe them.
Concentric - isotonic contraction with the muscle length decreasing Eccentric - isotonic contraction with the muscle length increasing
Define a muscle twitch
Single brief contraction in response to a single stimulation
Define threshold.
Minimum voltage needed to active a muscle
Define the latent peroid
Time after stimulus is applied before contraction begins
What is the mechanism of tetany?
Increased frequency of stimulation to muscles causes contraction
What is the mechanism of rigor?
Lack of ATP, so myosin heads cannot reset to relaxed postion
In what ways is cardiac muscle similar to skeletal muscle?
Striations, t-tubules, and CICR
Is cardiac muscle metabolism aerobic or anaerobic?
Almost entirely aerobic
What muscle cells would you expect to see a high volume of mitochondria?
Cardiac muscle
T/F? Smooth muscle does not have sarcomeres?
True
Describe the anchoring proteins of smooth muscle.
Smooth muscle has a cytoskeleton made of intermediate filaments. Dense bodies bind the filaments into the sarcoplasm, and dense plaques to the SL
Thick filaments of smooth muscle have a latch mechanism. What benefit does this provide?
Allows muscle to stay contracted without using additional ATP
Explain the pathway of smooth muscle contraction starting when calcium enters the cell.
Calcium binds to calmodulin forming Ca++ calmodulin complex. Ca++ calmodulin complex activates MLCK MLCK activates myosin Activated myosin can form cross bridges to contract.
