Chapter 12 - Muscles (Mechanisms of Control and Neural Control) Flashcards
Extensor =
increases the angle at a joint
Flexor =
Decreases the angle at a joint
Abductor =
Moves limb away form the midline of the body
Adductor =
Moves limb toward the midline of the body
Levator =
Moves insertion upward
Depressor =
Moves insertion downward
Rotator =
Rotates a bone along its axis
Sphincter =
Constricts an opening
Agonist Muscle =
prime mover of any skeletal movement
Antagonistic Muscles =
Flexors and extensors that act on the same joint to produce opposite actions
Episium =
Epi = Above / My = muscle, Fibrous connective tissue proteins within the tendorns extend around the muscle in an irregular arrangement, forming a sheeth.
Fascicles =
Connective Tissue from the episium extends into the body of the muscles, subdiving it in to cloumes. “Strings of Meat”
Perimysium =
Peri = round, Fascicles is surrounded by its own connective tissues sheath.
Sarcolemma =
Plasma membrane of muscles
A Bands =
Anistropic dark bands. Contains thick filaments (myosin)
I Bands =
Instoropic light bands. Contains thin filaments (actin)
M Lines =
produced by protein filaments located at the center of the thick filaments/A Band in the sarcomere. These serve to anchor the thick filaments, helping them stay together during contraction.
H Bands =
Central lighter regions of A Bands “H for Helle a German word meaing Bright”.
What is a “Motor Unit”? Fig. 12.4
A Motor Unit are each Somatic motor neuron, together with all of the muscle fibers that innervate.
A Motor unit consissts of somatic motor neuron and the muscle fibers it innervates.
Study figure 12.3, know all of the anatomical parts.
Look up.
What are fibers? What are myofibrils, myofilaments (filaments), sarcomeres?
Muscles are really just tubes within tubes: Filaments, Myofibrils, Muscle Fibers, Fasciculus, Skeletal Muscles
Myofibrils =
bundles in muscle fiber make up of filaments.
Myofilaments (filaments) =
Makes up the smaller structures of myofibril
Sarcomers =
Each subunit from Z to Z
Titin =
type of elastic protein that runs through the thick filaments from M Lines to Z Disces. This is believed to contribute to the elastic recoil of muscles that helps them return to their resting length during muscle relaxation.
Tropomysin =
A filamentous protein that attaches to actin in the thin filaments. Together with another protein called troponin, it acts to inhibit and regulate the attachment of myosin cross bridges to actin.
Troponin =
a protein found in the thin filaments of the sarcomeres of skeletal muscle. A subuint of tropopin binds….PG 749
Myosin =
Thick mucsle fibers
Actin =
Thin muscle fibers.
- Individual balls on actin is call G-Actin
- Tropomyosin are between G-Actin
- Actin is really 3 proteins: G-Actin, Tropomyosin, and Troponin.
Be able to draw the structure of a sarcomere much as I did on the board. Use figures 12.6,12.7,12.8 as guides.
REVIEW
What is the “Sliding Filament” theory?
The Theory that the thick (myosin) and thin (actin) filaments of a myofibril slide past each other during muscles contraction, decreasing the lenght of the sarcomers but maintaining their own initial length.
What are “Cross Bridges”? What are the 2 binding sites on the myosin head?
Extends out from the myosin to the actin. Shaft of myosin head that sticks out. Part of the myosin proteins that extend from the axis of the thick filaments to form an “arm” that terminate in globular heads. Myosin proteins have two globular heads that serves as cross bridges by attaching actin to each side of the sarcomere. They can pull the actin form each side toward the center.
Cross bridges are trying to attach to actins but tropomyosin is blocking the active site.
What is the actual structure of a thin filament? (See fig. 12.10)
Thin filament is composed of:
- Troponin
- (G)-Actin
- Tropomyosin
What is a “Power Stroke”?
A. Power Stroke is the force that pulls the thin filaments toward the center of the A Band.
B. Once the myosin head binds to actin, forming a cross bridge, the bound Phopspate is released. This results in a conformational change in the myosin cause the cross bridges to produce this.
C. The splitting of ATP is required before a cross bridge can attach to actin and undergo a power stroke, and that the attachment of a new ATP is needed for the cross bridge to release from actin at the end of a power stroke
What does the term “Rigor Mortis” mean?
A. Rigor Mortis occurs due to lack of ATP when the muscles dies. Without ATP the ADP remans bound to the cross bridges, and the cross bridges remain tightly bound to actin. The myosin and actin cannot detach.
What is the role of Ca++ in contraction?
The role of Ca++ in contraction is the attachment of Ca to troponin causes movement of the troopnin-tropomosin complex, which exposes binding sites on the actin. The myosin cross bridges can then attach to the actin and undergo a power stroke.
What is the mechanism that brings Ca ++ back into the sarcoplasmic reticulum?
Ca ++ -ATPase pumps, move Ca ++ from the sarcoplasm into the the sarcoplasmic reticulm. This causes the Ca ++ channels to close and action to stop. These pumps are powered by Hydrolysis of ATP, ATP is also needed for muscle relaxation as well as muscle contraction
Twitch:
When a muscle is stimulated with a single electric shock, it quickly contracts and relaxes.
Summation:
If a second electrical shock is delivered immediately after the first, it will produce a second twitch that may partially “ride piggyback” on the first.
Tetanus (Incomplete):
if the stimulator is set to deliver an increasing frequency of electrical shocks automatically, the relatxion time between successive twitches will get shorter and shorter as the strtength of the contractions increases in amplitude.
Tetanus (Complete):
a smooth sustained contraction, during normal muscle contraction in vivo
Isotonic:
same force
Isometric:
same length
What is the “Series Elastic Component”? What is its significance?
Provided by Tendons because they are somewhat elastic and in line with the force of the muscle contractions.
SEC absorbs some of the tension as a muscle contracts and it must be pulled right before the muscle contracts and must be pulled tight before the muscle contraction can result in muscle shortening.
Understand the “Length-Tension” relationship for skeletal muscle. Fig. 12.21 (Fig.12.20)
Maximum relative tension dj achieved when the muscle is 100% to 120% of its resting length. Increases or decreases in muscle (and sarcomere) lengths results in rapid decrease of tension.
Tension
The force that the muscle generates when it contracts is usually the same force required to prevent it from shortening.
Oxygen Debt
the extra oxygen used to get the levels back to the pre existing levels prior to exercise.
Slow-Twitch (type 1 fibers)
Also called red fibers (due the presence of myoglobin) these are often referred to as slow oxidative fibers. These fibers are rich in capillary supply, number mitochondria and aerobic respiration enzymes and myoglobin (which help to improve delivery of oxygen
Fast-Twitch (type 2 fibers)
White fibers, adapted to respire anaerobically by a large store of glycogen and high concentration of glycolytic enzyme.
Intermediate Fibers (Fast twitch fibers)
High-Oxidative, resistant to fatigue.
- IIA Fibers - fast oxidative fibers - high aerobic ability.
- Fast Glycolytic Fiber - hight rate of glycolysis (Type IIX Fibers in humans and Type IIB fingers in animals)
Muscle Fatigue
Appears to be due to the accumulation of extracellular K, which reduces the membrane potential of muscid fibers and interfere with their ability to produce action potentials.
Lower motor neurons
Neurons whose axons innervate skeletal muscles, also called the final common pathway in the control of the skeletal muscles
Upper motor neurons
Neurons of the brain that are involved in the control of skeletal movements an that act by facilitating or inhibiting the activing of the lower motor neurons.
Extrapyarmidal tracts
neurons in other areas of the brain produce these, the major on is the reticulospinal tract, believed to produce the inhibition of lower motor neurons.
Pyramidal Tracts
Neurons in the pre central gyrus of the cerebral cores contribute axons that cross to the contralateral sides in the pyramids of the medulla oblongata.
