Muscular Tissue Flashcards
What is the function of muscular tissue?
- Producing body movements
• relies on integrated functioning of skeletal muscles, bones, joints - Stabilizing body positions
• skeletal muscles contract to stabilize joints and help maintain body positions
• postural muscles contact continuously when awake - Regulate organ volumes
- Generating heat (thermogenesis)
• muscular tissue produces heat when contracting (thermogenesis) and heat generated is used to maintain body temperature (homeostasis) - Movement of substances throughout body
What produces motion?
Motion results from alternating contraction and relaxation of muscles. Chemical energy changed into mechanical energy to generate force, produce work and movement
What percentage does muscular tissue make up total adult body weight?
40-50% depending on percentage of body fat, gender, and exercise regimen
Myology
Study of muscles
What are the 3 types of muscular tissue?
Skeletal, cardiac, smooth
In what ways do the 3 muscular tissue differ from one another?
They differ in their microscopic anatomy and location, and how they are controlled by the nervous and endocrine systems
What is the function of skeletal muscles? Is it striated or non-striated? Is its activity involuntary or voluntary? How is it regulated?
• moves the bones of the skeleton (a few skeletal muscles attach to and move the skin or other skeletal muscles)
• striated: alternating light and dark protein bands (striations) are seen under microscope
• works mainly in voluntary matter and most skeletal muscles are controlled subconsciously
• activity can be consciously controlled by neutrons part of somatic (voluntary) division of nervous system
What is the function of cardiac muscle tissue? Is it non-striated or striated? Is it’s action voluntary or involuntary? How is it regulated?
• forms most of the heart wall
• striated
• action is involuntary; alternating contraction and relaxation of heart are not consciously controlled but heart beats because of natural pacemaker that initiates each contraction (built in rhythm called autorhythmicity)
• regulated by neurons part of autonomic (involuntary) division of nervous system and by hormones released by endocrine glands that can adjust heart rate by slowing down or speeding up pacemaker
What is the function of smooth muscle tissue? Is it striated or nonstriated? Is it’s action voluntary or involuntary? How is it regulated?
• located in walls of hollow internal structures (ex. blood vessels, airways, most organs of abdominopelvic cavity), attached to hair follicles in skin
• nonstriated; smooth
• action is involuntary
• some smooth muscle tissue has autorhythmicity (ex. muscles that propel good through digestive canal)
• regulated by neurons part of autonomic (involuntary) division of nervous system and by hormones released by endocrine glands
What are the 4 properties of muscular tissue?
- Electrical excitability: ability to respond to certain stimuli by producing muscle action potentials (impulses)
• muscle action potentials respond to 2 types of stimuli:
1) autorhythmic electrical signals coming from muscular tissue
2) chemical stimuli (ex. neurotransmitters released by neurons, hormones distributed by blood, local changes in pH - Contractibility: ability to contract and generate force (tension) while pulling on its attachment points
• if tension overcomes resistance of object being moved, muscle shortens and movement occurs - Extensibility: ability to stretch without being damaged
• connective tissues in muscles limits range of extensibility
• smooth muscle subject to most amount of stretching - Elasticity: ability to return to original length and shape after contraction or extension
Why is rich blood supply important for muscle contraction?
Describe how sarcolemma, T tubules, sarcoplasm, myofibril, thin and thick filaments, sarcomeres, Z discs, M line, sarcoplasmic reticulum, triads, terminal cisterns, and the bands and zones of sarcomeres make up the microscopic anatomy of a skeletal muscle fiber.
• Sarcolemma: the plasma membrane of a muscle fiber. The multiple nuclei are located beneath the sarcolemma.
• T (transverse) tubule: tiny tube shaped invaginations of sarcolemma filled with interstitial fluid. Thousands of these tunnel in from the surface toward the centre of each muscle fiber and allow muscle action potentials to quickly spread to all parts of muscle fiber.
• Sarcoplasm: cytoplasm of muscle fiber filled with a lot of glycogen, myoglobin (red coloured protein found only in muscle), mitochondria, and myofibrils. Glycogen is important for ATP synthesis. Myoglobin binds oxygen that diffuse into muscle fibers from interstitial fluid and releases it when needed by mitochondria for ATP production. Mitochondria lie in rows throughout the muscle fiber, close to contractile muscle proteins so that ATP can be produced quickly for use.
• Myofibrils are the contractile organelles of skeletal muscle. They’re 2 nanometers in diameter and extend the entire length of the muscle fiber and look like little threads which makes the muscle fiber appear striped (striated). Myofibrils contain filaments/myofilaments sorted into thin filaments and thick filaments. Thin filaments are 8 nanometers in diameter and 1-2 nanometers long and compose of protein actin. Thick filaments are 16 nanometers in diameter and 1-2 nanometers long and compose of protein myosin. The filaments are directly involved in the contractile process but don’t extend entire length of muscle fiber, and usually there’s 2 thin filaments per 1 thick filaments where they overlap.
• Sarcomere: group of overlapping thin and thick filaments (how thin and thick filaments are organized)
• Z discs: narrow, plate shaped regions of dense protein found on each end of a sarcomere to separate them and at centre of I band. It contains proteins that link adjacent sarcomeres and anchors thin filaments.
• I band: lighter, less dense area containing rest of thin filaments and no thick filaments. Striations seen in myofibrils and skeletal and cardiac muscle fibers are due to alternation of A and I bands.
• A band: darker middle part of sarcomere extending entire length of thick filaments and parts of thin filaments that overlap with thick filaments.
• Zone of overlap: 2 zones found in A band where thick and thin filaments overlap.
• H band: narrow band in centre of each A band in between 2 zones of overlap containing thick filaments only.
• M line: formed from supporting proteins that hold thick filaments together at centre of H band located in middle of sarcomere.
• Sarcoplasmic reticulum (SR): a fluid filled system of membranous sacs that encircles each myofibril and stores calcium ions (Ca2+) when muscle is relaxed and on release triggers muscle contraction. Ca2+ is released from terminal cisterns which are the dilated end sacs and form a triad when 2 terminal cisterns sit in either side of a T tubule.
What is skeletal muscles composed of?
Thousands of long, cylindrical muscles cells called muscle fibers/myocytes, connective tissues surround muscle fibers, blood vessels, and nerves
What is the function of connective tissue in skeletal muscle tissue?
Connective tissue surrounds and protects muscular tissue
What is the subcutaneous tissue/hypodermis? What is it composed of and it’s function?
The subcutaneous tissue or hypodermis separates muscle from skin. It is composed of areolar connective tissue and adipose tissue. It provides pathway for nerves, blood vessels, and lymphatic vessels to enter and exit muscles. The adipose tissue stores most of body’s triglycerides and serves as insulating layer to reduce heat loss and protects muscles from physical trauma.
What is fascia? What is it’s function?
Fascia is a dense sheet of irregular connective tissue that lines body wall and limbs and supports and surrounds muscles and other body organs. It hold muscles with similar functions together and allows free movement of muscles, carries nerves, blood vessels, and lymphatic vessels, and fills spaces between muscles.
What are the 3 layers of connective tissue that extend from fascia to protect and strengthen skeletal muscle and help organize skeletal muscles?
- Epimysium: outer layer of dense irregular connective tissue encircling entire muscle
- Perimysium: layer of dense irregular connective tissue surrounding groups of 10-100 or more muscle fibers and separates them into bundles called muscle fascicles/muscle fasciculi
• muscle fascicles give meat characteristic “grain”; meat will rip apart along muscle fascicles - Endomysium: reticular fibers that separates individual muscle fibers from each other within each muscle fascicle
Aponeurosis
Connective tissues elements that extend as a broad, flat sheet
What are the 2 structures that connective tissue layer can extend to form?
- Tendon: ropelike structure that attaches muscle to periosteum of a bone
- Aponeurosis: when tissues extend as a broad, flat sheet
What are somatic motor neurons? What is the component(s) that allow it to function?
Neurons that stimulate skeletal muscle to contract, each neuron has an axon that extends from brain or spinal cord to group of skeletal muscle fibers and each axon typically branches many times to differ be skeletal muscle fiber.
How many arteries and veins accompany each nerve that penetrates a skeletal muscle?
Generally 1 artery and 1-2 veins accompany each nefve
Each muscle fiber is in close contact with 1 or more blood capillaries. What do blood capillaries do?
They bring oxygen and nutrients to muscle fiber and remove heat and waste products of muscle metabolism from it.
What is fibromyalgia? What are the symptoms and treatments?
Fibromyalgia is a chronic, non articular rheumatic disorder affecting fibrous connective tissue components of muscles, tendons, and ligaments. It causes pain, especially from gentle pressure at “tender points”, tenderness, stiffness of muscles, tendons and surrounding soft tissues, severe fatigue, poor sleep, headaches, depression, irritable bowel syndrome, and inability to carry out daily activities. Treatment includes stress reduction, regular excercise, heat application, gentle massage, physical therapy, pain meds, and low dose of antidepressants for sleep; there is no identifiable cause.
What is the diameter and length of a mature muscle fiber?
Diameter ranges from 10-100 nanometer and length is about 4in but some can be as long as 12in.
