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muscular system ch 8
| Question | Answer |
|---|---|
| muscle functions | Motion Maintenance of posture Heat production |
| types of muscle | Skeletal Smooth Cardiac |
| characteristics of muscle | Excitability Responds to stimuli (e.g., nervous impulses) Contractility Able to shorten in length Extensibility Stretches when pulled Elasticity Tends to return to original shape & length after contraction or extension |
| muscles | skeletal muscles -will not contract unless stimulated by neurons (mooth & cardiac -will contract without nervous stimulation but their contraction can be influenced by the nervous system Nervous and muscle systems are closely interconnected |
| skeletal | Attached to bones & moves skeleton Also called striated muscle (because of its appearance under the microscope Voluntary muscle |
| smooth | -Involuntary muscle -Non-striated -Muscle of the viscera -In walls of hollow organs -blood vessels -Intestine -Bladder -uterus -other 'hollow' structures and organs in the body |
| cardiac | Muscle of the heart Involuntary Striated |
| Voluntary Striated Muscle | Microscopic appearance – low power magnification Dark and light bands run the length of each cell Pattern of cross banding |
| tendons | are tough fibrous connective tissue bands which connect most skeletal muscles to bone |
| Aponeuroses | are broad sheets of fibrous connective tissue which attach some muscles to bones or other muscles Example: Linea alba which runs along the ventral midline |
| the origin | of muscle is the more stable site of attachment Therefore the origin does not move much when the muscle contracts |
| insertion | of the muscle is the more moveable attachment |
| muscle action | Contract after stimulation by a nerve impulse.Pulls on its attachment sites=movement.Individual muscles rarely contract singly.Usually work in groups w/certain muscles.others stabilize nearby joints 4 a smooth control over movements |
| Prime Mover or Agonist | is the muscle or muscle group which directly produces desired movement |
| Antagonist | is the muscle or muscle group that directly opposes the action of the prime agonist Through partial contractions can help smooth out the movements of agonist. Rigidity or lack of motion will result if forcefully contracts at same time as prime mover |
| synergist | a muscle that contracts at the same time as a prime mover and assists in carrying out its action |
| fixator | muscles stabilize joints to allow other movements to take place Flex your fingers on one hand while feeling the underside and the top of your forearm |
| triceps brachii's origin | Attached at its origin to a large area of bone-the scapula and proximal humerus |
| triceps brachii's other end | the insertion, it tapers into a glistening white tendon which is attached to the Olecranon process of ulna Olecranon process is the point of the elbow |
| triceps brachii contracts | As the triceps contracts, the insertion is pulled toward the origin and the arm is straightened also known as extended at the elbow Therefore the triceps is an extensor muscle |
| flexor | Because skeletal muscle exerts force only when it contracts, a second muscle — a flexor — is needed to flex or bend the joint |
| bicepts | This muscle is the flexor of the lower arm |
| antagonistic pair of muscles | Together, the biceps and triceps make it. |
| naming | Action-ex. flexor Shape- ex. deltoideous Location- ex. biceps brachii Direction of fibers- ex. external abd. oblique Number of heads or divisions- ex. biceps Attachment sites –ex. sternocephalicus |
| Cutaneous Muscles | Thin, broad and superficial Serve only to twitch skin Humans lack In the connective tissue just below the skin |
| Masseter | powerful chewing muscle (closes the jaw) |
| Splenius and Trapezius muscles | raise/extend the head and neck Located on the dorsal aspect of the neck |
| Brachiocephalicus | Extends head and neck as well as pulls the front leg forward Located on the mid to ventral portion of the neck Large strap like muscle from the proximal humerus to the base of skull |
| Sternocephalicus | Smaller straplike flexor (lower) of neck Extends from sternum to base of skull |
| abdominal muscles | Function to support abdominal organs, flexion of the back, respiration and provide abdominal press for any type of straining |
| Arranged in layers | (ordered from outside-in (from abaxial to axial)) External Abdominal Oblique Muscles Internal Abdominal Oblique Muscles Rectus Abdominis Transversus Abdominis |
| Linea Alba | Left and Right parts meet at ventral midline known as Linea Alba. Linea Alba – aponeurosis that extends from xiphoid process to pubis |
| External Abdominal Oblique Muscles | Slant in caudoventral direction |
| Internal Abdominal Oblique Muscles | Slant in cranioventral direction |
| Rectus Abdominis | Forms the ventral portion Runs from ribs and sternum back to pubis |
| Transversus Abdominis | Deepest of the muscles and runs directly downward in a ventral direction to insert on the linea alba |
| Inspiratory Muscles | (drawing air in and expanding thoracic cavity size) |
| Diaphragm | One of the main muscles Thin dome shaped sheet of muscle separating thoracic cavity from abdominal cavity Convex surface protrudes into thoracic cavity Contracts – Flattens and subsequently pushes abdominal organs caudally |
| External intercostal muscles | Oblique orientation allows contraction to rotate ribs upward and forward Increases size of thoracic cavity - drawing air in |
| Expiratory Muscles | do not require as much energy due to elastic nature of lungs and mechanical forces such as gravity |
| Internal intercostal muscles | Run at right angles to the external intercostal muscles Oblique orientation allows contraction to rotate ribs backwards Decreases size of thoracic cavity – pushing air out |
| Abdominal Muscles | Push abdominal organs against diaphragm Most important when breathing hard or fast Severe chronic respiratory diseases will increase abdominal musculature press – “Heave Line” |
| Latissimus Dorsi Muscle | flexes the shoulder (propels body forward) Broad triangular muscle that extends from spinal column to the humerus |
| Pectoral Muscles | Adductors (inward movers) of the front leg Prevent Splaying Extend from sternum to humerus Usually two pectoral muscles per side: deep and superficial |
| Deltoid Muscle | abducts (moves outward) and flexes shoulder joint Triangular and extends form lateral portion of scapular down to humerus |
| Biceps Brachii | Flexes the elbow joint Two heads/origins Extends from distal end of scapula to proximal radius |
| Triceps Brachii | Extends the elbow joint Three heads/origins Extends from distal scapula and proximal humerus down to the olecranon process of the ulna (point of the elbow) |
| Extensor Muscles | are on the generally located on cranial aspect (front) of the radius Extensor carpi radialis – extends the carpus |
| Flexors Muscles | are generally located on the caudal aspect (back) of the radius Deep digital flexor – flexes the digit |
| Gluteal Muscles | extensors of the hip joint (pulling the leg backward) Extend from bones of the pelvis to the trochanters of the femurs |
| Hamstring muscle group | extensors of the hip joint and main flexors of the stifle joint (propel the animal forward) 3 Muscles located on the caudal thigh region Biceps Femoris Semimembranosus Semitendinosus |
| Quadriceps femoris | main extensor of the stifle Located on the cranial part of the thigh Helps to bring limb forward to prepare for the next stride Composed of 4 heads or parts |
| Gastrocnemius Muscle | powerful extensor of the hock (propels body forward) Extends from the caudal aspect of the distal femur to the calcaneal tuberosity (point of the hock) Muscle is equivalent to human calf muscle: Tendon is known in humans as the Achilles tendon |
| The flexors and extensors of the tarsus and digit | demonstrate similar general locations as mentioned for the thoracic limb (flexors are caudal; extensors are cranial) |
| best areas for intramuscular injection | are large, thick muscle bellies which are easily accessible and place the person injecting the drug in a relatively safe location |
| intramuscular injection Ideal locations | are not neighboring sensitive structures such as nerves and will allow for ventral drainage should a complication such as infection/abscessation occur. In food animals – would like to avoid the choice cuts of meats |
| Intramuscular Injection Sites in Cats and Dogs | Pelvic limb - Gluteal muscles Quadriceps Femoris muscle Hamstring group (biceps femoris, semimembranosus and semitendinosus muscles) Thoracic Limb - Triceps Brachii muscle |
| Cattle and Goats | Pelvic limb Gluteal muscles Hamstring group (biceps femoris, semimembranosus and semitendinosus muscles) Thoracic Limb (goat) - Triceps Brachii muscle Neck - Trapezius muscle |
| horses | Pelvic limb Gluteal muscles Hamstring group (biceps femoris, semimembranosus and semitendinosus muscles) Thoracic Limb - Triceps Brachii muscle Neck - Trapezius muscle Chest - Pectoral muscles |
| swine | Pelvic Limb Semitendinosus muscle Neck Brachiocephalicus muscle Trapezius muscle |
| Skeletal Muscle – General Structure | Made up of thousands of cylindrical muscle fibers often running all the way from origin to insertion The fibers are bound together by connective tissue through which run blood vessels and nerves |
| muscle fibers | An array of myofibrils that are stacked lengthwise and run the entire length of the fiber Mitochondria An extensive endoplasmic reticulum Many nuclei |
| muscle fiber development | by the fusion of many cells (called myoblasts); subsequently, resulting in multiple nuclei in each fiber The number of fibers is probably fixed early in life |
| Myostatin | cytokine that is synthesized in muscle cells (and circulates as a hormone later in life). Myostatin suppresses skeletal muscle development |
| Increased strength and muscle mass | is achieved in mature animals by increased thickness of the individual fibers and an increase in the amount of connective tissue |
| endomysium | Each individual skeletal muscle fiber is surrounded by delicate connective tissue known as it. |
| fascicles | Groups of skeletal muscle fibers |
| perimysium | Fascicles are bound together by tougher connective tissue known as it |
| epimysium | Groups of fascicles are surrounded by it Epimysium is fibrous connective tissue mainly of tough collagen fibers Epimysium is the outer covering of the muscle |
| sarcoplasmic reticulum | it extends between the myofibrils. The striated appearance of the muscle fiber is created by a pattern of alternating dark A bands and light I bands. The A bands are bisected by the H zone The I bands are bisected by the Z line. |
| sarcoplasm | cytoplasm |
| sarcolemma | plasma membrane of a muscle cell Maintains a membrane potential Impulses travel along muscle cell membranes Function of impulses in muscle cells is to bring about contraction |
| myofilaments | Muscle fibers or Myofibrils r made up of long parallel protein molecules called it 2 types- Thin: Composed mainly of Actin Also troponin and tropomysin Thick: Myosin (Thick myofilaments (Myosin)r surrounded by 6 thin myofilaments (mainly Actin)) |
| Thin myofilaments | (mainly Actin) extend in from each end |
| Thick myofilaments | are found in the middle of the sarcomere and do not extend to the ends |
| ends of a sarcomere | (where only thin myofilaments are found) appear lighter than the central section (which is dark because of the presence of the thick myofilaments) |
| filaments structure | The thick filaments produce the dark A band Thin filaments extend in each direction from the Z line The I band is where the thick filaments do not overlap The H zone is that portion of the A band where the thick and thin filaments do not overlap |
| sarcomere | is the entire array of thick and thin filaments between the Z lines Each myofibril is composed of many sarcomeres lined up end-to-end |
| MYOSIN HEAD | (thick)Has ATP-binding sites=fit molecules of ATP.Actin-binding sites=fit molecules of actin.hinge=at the point where it leaves the core of the thick myofilament.Allow the head to swivel back n forth.Swivelling is what actually causes muscle contraction |
| Thin myofilaments composed of 3 types of protein | Actin Troponin Tropomyosin The actin molecules are spherical and form long chains Each thin myofilament contains two such actin chains that coil around each other |
| Tropomyosin and troponin | molecules are lone, thin molecules that wrap around the chain of actin.At the end of each tropomyosin is a troponin molecule. The tropomyosin and troponin molecules are connected to each other. |
| Tropomyosin | In a relaxed muscle, the myosin heads lie against tropomyosin molecules As long as the heads remains in contact with tropomyosin nothing happens |
| troponin | Troponin=binding sites4calcium ions When a calcium ion fills this site it causes a change in the shape n position of troponin.Troponin shifts, pulling the attached tropomyosin.The myosin head that was touching the tropomyosin=contact w/underlying actin |
| Actin | When actin combines with myosin head the previous energy stored from ATP breakdown into ADP & P is released This reaction releases energy that causes the head to swivel |
| Sarcolemma's T-Tubules | has extensions known T-tubules.T-tubules extend the cell membrane into the depths of the cell.They do not open into the interior of the muscle cell help carry an impulse caused by nerve stimulation into the interior of the muscle cell for contraction |
| The function of T-tubules | is to conduct impulses from the surface of the cell, the sarcolemma, down into the cell Specifically to the sarcoplasmic reticulum |
| Sarcoplasmic reticulum | The membrane of the SR is well-equipped to handle calcium “Pumps" (active transport) for calcium Calcium is constantly being "pumped" into the SR from the cytoplasm of the muscle cell (Sarcoplasm). store Ca |
| Ca2+ role in a relaxed muscle | high ca-SR low ca=sarcoplasm low ca=myofibrils & myofilaments membrane has "gates", for calcium.When relaxed these gates are closed and calcium cannot pass through the membrane So, the calcium remains in the SR |
| Ca2+ role in impulse | travels along the membrane of the SR, the calcium "gates" open Calcium diffuses rapidly out of the SR & into the sarcoplasm where the myofibrils & myofilaments are located A key step in muscle contraction. |
| SKELETAL MUSCLE CONTRACTION step 1 | When the impulse is transferred from a neuron to the sarcolemma of a muscle cell |
| step 2 | The impulse travels along the sarcolemma down the T-tubules to the sarcoplasmic reticulum |
| step 3 | The calcium gates in the membrane of the SR open and calcium diffuses out of the SR and among the myofilaments |
| step 4 | Movement of tropomyosin permits the myosin head to contact actin |
| step 5 | Contact with actin causes the myosin head to swivel |
| step 6 | during swivel=the head is firmly attached to actin The head swivels and pulls the actin n subsequently the entire thin myofilament.Many myosin heads r swiveling simultaneously and their collective efforts are enough to pull the entire thin myofilament |
| step 7 | end swivel=ATP fits binding site on the cross-bridge & breaks the bond b/w cross-bridge (myosin) and actin The myosin head then swivels back As it swivels back, the ATP breaks down to ADP & P and the cross-bridge again binds to an actin molecule. |
| step 8 | The head is once again bound firmly to actin However, the HEAD was not attached to actin when it swiveled back so it will bind to a different ACTIN molecule Once the head is attached to actin, the cross-bridge again swivels, so step 7 is repeated |
| Skeletal muscle relaxes | impulse stops=No impulse=membrane of the SARCOPLASMIC RETICULUM no longer permeable to Ca.Ca no longer diffuses out of the SR and is actively transported back into the SR via a calcium pump.Req ATP–active transport.Ca ions leave sites on the troponin |
| Ca levels | Calcium levels in the muscle fiber are determined largely by the calcium level in the bloodstream Calcitonin and parathyroid hormone relaxing=ATP 2 |
| muscle stop contracting | Troponin returns to its original shape,attached tropomyosin returns to original shape.Tropomyosin is now back in position in contact with the myosin head.Myosin head is no longer in contact with actin and, therefore, the muscle stops contracting |
| ATP decline | the myosin heads remain bound to actin ,Can no longer swivel.Fatigue=strong contraction not possible. energy Phosphate to keep ATP filled: creatine phosphate glycogen cellular respiration in the mitochondria of the fibers |
| Creatine phosphate | The phosphate group in creatine phosphate is attached by a "high-energy" bond like that in ATP Creatine phosphate derives its high-energy phosphate from ATP n can donate it back to ADP to form ATP Creatine phosphate + ADP ↔ creatine + ATP.atp reservoir |
| glycogen | Skeletal muscle fibers contain 1% glycogen .Glycogen metabolized to ATP.Keeps the muscle functioning if it fails to receive sufficient oxygen to meet its ATP needs by respiration. limited and eventually the muscle must depend on cellular respiration |
| neuromuscular junction 1 | the impulse at end bulb chemical transmitter released diffuses across the neuromuscular cleft the transmitter molecules fill receptor sites in the membrane of the muscle. |
| neuromuscular junction 2 | increase membrane permeability to sodium sodium diffuses in the membrane potential becomes less negative if the threshold potential is reached, an action potential occurs, an impulse travels along the muscle cell membrane, and the muscle contracts. |
| motor neuron | leading to muscles have branching axons=terminates in a neuromuscular junction with a single muscle fiber.Nerve impulses passing down a single motor neuron will trigger contraction in all the muscle fibers at which the branches of that neuron terminate. |
| motor unit | minimum unit of contraction.The size of the motor unit is small in muscles over which we have precise control A single motor neuron triggers fewer than 10 fibers in the muscles controlling eye movements |
| Response of a motor unit is all-or-none | However, the strength of the response of the entire muscle is determined by the number of motor units activated |
| tonus | partial contractions maintained by the activation of a few motor units at all times even in resting muscle As one set of motor units relaxes, another set takes over |
| isotonic | tension or force generated by the muscle is greater than the load & the muscle shortens |
| isometric | load is greater than the tension or force generated by the muscle & the muscle does not shorten |
| twitch | The response of a skeletal muscle to a single stimulation (or action potential) |
| latent period | No change in length Time during which impulse is traveling along sarcolemma & down t-tubules to sarcoplasmic reticulum, calcium is being released Muscle cannot contract instantaneously |
| contraction period | Tension increases (cross-bridges are swiveling) |
| relaxation period | Muscle relaxes (tension decreases) & tends to return to its original length |
| type 1 muscle fibers | Loaded w/mitochondria.Depend on cellular respiration for ATP.Resistant to fatigue.Rich in myoglobin=red.Activated by small-diameter=slow-conducting, motor neurons=slow-twitch fibers.Dominant in muscles that depend on tonus e)posture |
| type 2 muscle fibers | Few mitochondria.Rich in glycogen and Depend on glycolysis for ATP.Fatigue easily.Low in myoglobin=whitish.Activated by large-diameter (fast-conducting) motor neurons.Also known as "fast-twitch" fibers .Dominant in muscles used for rapid movement |
| Involuntary muscle (smooth muscle) | Innervated by the Autonomic Nervous System (visceral efferent fibers) Found primarily in the walls of hollow organs & tubes Spindle-shaped cells typically arranged in sheets |
| Involuntary muscle2 | Cells no sarcomeres (not striated) The contraction of smooth muscle tends to be slower than that of striated muscle.It also is often sustained for long periods. This, too, is called tonus but the mechanism is not like that in skeletal muscle. |
| Involuntary muscle3 | In general does not depend on motor neurons to be stimulated Motor neurons (of the autonomic system) reach smooth muscle and can stimulate it — or relax it — depending on the neurotransmitter they release |
| cardiac muscle | Resembles skeletal muscle in some ways Striated appearance Each cell contains sarcomeres with sliding filaments of actin and myosin |
| cardiac muscle 2 | pumping blood. The myofibrils of each cell (and cardiac muscle is made of single cells — each with a single nucleus) are branched. The branches interlock with those of adjacent fibers by adherens junctions. |
| cardiac muscle 3 | Motor nerves (of the ANS) do run to the heart However, their effect=modulate — increase or decrease the intrinsic rate and the strength of the heartbeat.Even if the nerves are destroyed (as they are in a transplanted heart), the heart continues to beat. |
| fibrillation | Anything that interferes with this synchronous wave (such as damage to part of the heart muscle from a heart attack) may cause the fibers of the heart to beat at random |
| action potential | Drives contraction of the heart passes from fiber to fiber through gap junctions.All the fibers contract in a synchronous wave that sweeps from the atria down through the ventricles and pumps blood out of the heart |
| Cardiac muscle energy | Cardiac muscle has a much richer supply of mitochondria than skeletal muscle=greater dependence on cellular respiration for ATP.Cardiac muscle has little glycogen and gets little benefit from glycolysis when the supply of oxygen is limited. |
| Regenerative capacity of muscle types | Skeletal- Some regenerative capacity from satellite cells within the basal lamina of the muscle fiber Cardiac- none Smooth- high regenerative capacity Cells can take on a proliferative state or a contractile state |
Created by:
mary92