Ch 10 study guide

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2 minutes

Anaerobic glycolysis supplies enough ATP for muscles for two minutes of maximal activity.

Skeletal muscle

voluntarily controlled

Cross-bridges

when cross-bridges bind to the active site of actin thin filaments (myosin binding site), the thick filaments pivot toward the M line

Fascia

Fascia lines the body wall and limbs that surround and support muscles

15 seconds

In skeletal muscles, the combined amounts of creatine phosphate and ATP provide enough energy for the muscle to contract maximally for approximately 15 seconds.

Smooth muscle contraction

Smooth muscle contracts when calcium ions Ca2+ interact with calmodulin which activate the enzyme myosin light chain kinase, enabling myosin heads to attach to actin

Contraction Cycle

Step 1: Myosin head hydrolyses ATP and become energized and oriented

Transverse tubules (T-tubules)

T tubules are tunnels in from the surface toward the center of each muscle fiber

Triad

a T-tubule and two terminal cisterns on either side form a triad

Twitch

a brief contraction of all muscle fibers in a motor unit in response to a single action potential moving down the somatic motor neuron.

Rigor mortis

a condition in which muscles are in a state of rigidity 3-4 hour after death and last about 24 hours

Cori cycle

a cycle in the liver in which the lactic acid is converted to pyruvic acid and glucose

Zone of Overlap

a dark region where thin and thick filaments lie side by side

Perimysium

a fibrous connective tissue that covers each fascicle of muscle and contains nerves and blood vessels that service the muscle fibers

Nebulin

a long, non-elastic protein wrapped around the entire length of each thin filament

Incomplete tetanus (unfused tetanus)

a muscle producing peak tension with rapid cycles of contraction and relaxation

Complete tetanus (fused tetanus)

a muscle that is stimulated so frequently that the relaxation phase is completely eliminated

Refractory Period

a period that the muscle fiber loses its excitability and cannot response to a second stimulus

A myogram

a record of muscle contraction

Muscle tone

a small amount of tension in the muscle at rest due to weak, involuntary contractions of its motor units

Flaccid

a state of limpness in which muscle tone is lost.

Aponeurosis

a wide and flat tendon

Myasthenia Gravis

an autoimmune disorder that targets the ACh receptors at the NMJ and ultimately reduces the number of available receptors. Treat the patient with a drug that inhibits the activity of acetylcholinesterase will increase contraction

Spasticity

an increased muscle tone associated with an increase in tendon reflexes

Rigidity

an increased muscle tone in which tendon reflexes are not affected (tetanus)

tropomyosin

at rest, active sites of actin (myosin-binding site) thin filament are blocked (covered) by tropomyosin molecules

tropomyosin

at rest, the tropomyosin molecule is held in place by troponin

Overlapping

The overlapping of thick and thin filaments and the prominent striations of the myofibrils make the entire skeletal muscle fiber appear striated

Titin

The part of the titin that extends from the Z disc is very elastic. Thus, titin accounts for much of the elasticity and extensibility of myofibrils

Action potentials

conducted into a skeletal muscle fiber by transverse tubules (T-tubules)

The cytoplasm of the synaptic terminal

contains mitochondria and vesicles filled with neurotransmitter acetylcholine

Myofibrils

contractile organelles of muscle cell

Excitation-contraction coupling

The sequence of events that links excitation (generation an action potential) to the contraction

receptors for Ach

There are approximately 40 million receptors for Ach that are found in the motor-end -plate

Actin and myosin

contractile proteins of the muscle fiber

Acetylcholine (Ach)

To generate an action potential, acetylcholine (Ach), a neurotransmitter must be released at the neuromuscular junction (NMJ)

Contraction of myofibrils

contraction of myofibrils within a muscle fiber begins when calciumion is released from the terminal cistern of sarcoplasmic reticulum

calcium release

When a muscle fiber is relaxed, the concentration of Ca++in the sarcoplasm is very slow, but the concentration of Ca++ in the sarcoplasm reticulum (SR) is very high. As a result, to trigger muscle contraction, Ca++ must be released from SR

Acetylcholine

When acetylcholine binds to receptors at the motor-end plate, the muscle membrane becomes more permeable to sodium ions ( Voltage-gated Na+ channel opens to allow Na+ ions entering inside the sarcolemma)

Terminal cisterns

dilated end sac of the SR

Rigor mortis

disappears as proteolytic enzymes from lysosomes digest the cross-bridges)

thin filament

each thin filament consists of a pair of protein actin strands wound together into a helix

Myoblast

embryonic cell (stem cell) that forms muscle fiber

ATP hydrolysis reaction

energizes the myosin head

Energy Reserves in a Muscle

When energy reserves in a muscle are exhausted and lactic acid levels increase, muscle fatigue occurs

Single-unit smooth muscle tissue

found in the skin and in tubular arrangements that form part of the walls of small arteries and veins and of hollow organs such as the stomach, intestines, uterus, and urinary bladder.

Multi-unit smooth muscle tissue

found in the walls of large arteries, in airways to the lungs, in the arrector pili muscles that attach to hair follicles, in the muscles of the iris that adjust pupil diameter, and in the ciliary body that adjusts focus of the lens in the eye

Muscle fibers

have many nuclei in order to produce large amounts of the enzymes and structural proteins needed for contraction

Skeletal muscle cells

have more than one nucleus, are large and run parallel to each other

A myogram of twitch contraction

includes the latent period, the contraction period, and the relaxation period

Cardiac & Smooth muscle tissue

involuntary and auto-rhythmic

Skeletal muscle fiber

is controlled by a neuron at a single neuromuscular junction

Tetanus

is due to a toxin that makes the muscle cell membrane more permeable to calcium ions (Ca2+), causing powerful tetanic contraction

The mechanisms of rigor mortis

is due to calcium ions leak out of the SR (allowing myosin heads to bind to actin) and muscle fibers run out of ATP (causing the cross-bridges cannot detach from actin)

action potential or a (depolarization) or a (nerve impulse)

is required for the SR releases Ca2+ into sarcoplasm because when an action potential travels along the T. Tubule to open the voltage-gated Ca2+ channel allows a large amount of calcium flow out of the SR

Recruitment

is the increase in muscle tension that is produced by increasing the number of active motor units.

Neuromuscular Junction (NMJ)

is the synapse between the terminal end of a somatic motor (axon terminal) neuron and a portion sarcolemma (called Motor-End-Plate) of a skeletal muscle fiber

smooth muscle cells

like cardiac muscle cells, some smooth muscle cells communicate via gap junctions

Receptors for acetylcholine

located on the motor-end plate (the region of the sarcolemma opposite the synaptic end)

Levels of Exertion

mitochondria can provide only one-third (33%) of the ATP needed. The remainder comes from glycolysis

Multi-unit smooth muscle tissue

muscle cells have few gap junctions with neighboring cells and thus must be excited by their own motor neuron terminal

Z line or Z disk

narrow, plate-shaped region of dense protein material that separates one sarcomere to another

Cramp

occurs because the relaxation phase of a muscle contraction is often prolonged in a fatigued muscle, raising the likelihood of fused summation of action potentials causing painful disturbances to a skeletal muscle

Sarcolemma

plasma membrane of a muscle fiber (muscle cell)

Dystrophin

protein used to reinforce the sarcolemma and help transmit the tension generated by the sarcomeres to the tendons

Somatic motor neurons (voluntary control)

provide nerve impulses that stimulate skeletal muscle to contract

Hypotonia

refers to decreased or lost muscle tone

Hypertonia

refers to increased muscle tone

Tropomyosin and troponin

regulatory proteins of the muscle fibers

SR (sarcoplasmic reticulum)

releases calcium in response to an arrival of action potential

Mitochondrial activity

skeletal muscle cells are usually efficient, but can have limited ATP production if there is limited O2 availability

Smooth muscle cells

small but form thick layers of hollow organs

Microfilaments

smaller proteins within myofibrils

stores calcium ions (Ca2+)

Sarcoplasm

stores glycogen and myoglobin, a red-colored protein that binds O2

Titin, myomesin, nebulin, α-Actinin, & dystrophin

structural proteins of the muscle fibers

Aerobic respiration

supplies enough ATP for muscles during periods of rest or moderate exercises (running, jogging, swimming, and walking)

Sarcomere

the basic functional unit of a myofibril of a skeletal muscle fiber

Sarcoplasm

the cytoplasm of a muscle fiber

A band

the darker middle area of sarcomere that contains thick & thin filament

Endomysium

the delicate connective tissue that surrounds the individual muscle fiber and contains a large capillary network

Epimysium

the dense irregular connective tissue that surrounds the entire muscle

Treppe (stair case)

the increased strength of a contraction that occurs when a second stimulus arrives after the muscle fiber has relaxed completely following the previous stimulus

Wave summation

the increased strength of a contraction that occurs when a second stimulus arrives before the muscle fiber has relaxed completely.

Titin

the largest size protein in the muscle fiber that extends from the Z disk to M line

I band

the light area of the sarcomere that contains thin filament only

Myosin

the main component of the thick filament and functions as a motor protein of muscle tissue

Actin

the main protein of the thin filament

Eccentric isotonic contraction

the muscle fiber lengthens. (object is dropped)

Concentric isotonic contraction

the muscle fiber shortens. (object is lifted)

H zone

the narrow area in the center of the A band that contains thick filament only

Synaptic cleft

the narrow space between the neuron and the muscle fiber

Myomesin

the protein of M line

Sarcoplasmic reticulum (SR)

the series of membranous channels that surround each myofibril.

Isometric contraction

the type of contraction in which the muscle fibers produce tension but do not shorten nor lengthen. (Object cannot be moved)

Isotonic contraction

the type of contraction in which the muscle fibers produce tension while muscle length is changed

(sarcomere)M line

thick and thin filaments are linked laterally

Microfilaments

thin and thick filaments

Sarcomere

thin and thick filaments do not extend the entire length of muscle fiber. Instead, they are arranged in compartment

Thin filaments

thin filaments at either end of sarcomere are attached to the Z line (Z disc)

Cardiac muscle cells

usually have only one, sometimes two, centrally located nuclei and are branched

Cross bridges

- are portions of thick filament (myosin head) - act as (an enzymes) ATPase during the contraction cycle of muscle - generate force

Motor unit

-A term describes a somatic motor neuron and all the skeletal muscle fibers it stimulates -The ratio of motor neurons to muscle fiber is the greatest in muscles that control the eye and the tongue

Form crossbridges

-ATP must be broken down by enzyme ATPase -Calcium ions must be present in the sarcoplasm -Myosin binding sites (actin active site) must be exposed

Functions of Smooth Muscle

-Altering the diameter of the respiratory passageways -Moving food materials along the digestive tract -Moving sperms in the male reproductive tract and oocytes in the uterine tract Expelling fetus by contraction of the wall of the uterus -Acting as a sphincter

Slow fibers: Slow oxidative fiber (SO)

-Small diameter -MOST resistant to fatigue -Oxidative fibers have many mitochondria. That is a reason why they use aerobic respiration. -high concentration of myoglobin (Red meat) -Produce slow contraction

Major characteristics of smooth muscle cells

-Smooth muscle cells are uninucleate -Smooth muscles lack sarcomeres -Thin filaments are attached to dense bodies -Transmitting the contractile forces from cell to cells throughout the muscle tissue. -Involuntary control (pacesetter cells)

skeletal muscle fiber contracts in the sliding filament mechanism

-Z line (Z disk) moves closer together -the H zones and I bands get smaller -the width of the A band remains constant -the zone of overlap gets larger (more zone of overlaps between thin & thick filament)

Provide the oxygen after exercise

-convert the lactic acid produced during exercise back into glycogen -resynthesize creatine phosphate -replace oxygen displaced from muscle myoglobin

A Troponin molecule consists three globular subunits

-unit 1 binds to tropomyosin -unit 2 binds to G-actin -unit 3 binds to calcium ions

Muscle has 3 ways to produce ATP

-Producing ATP from creatine phosphate by direct phosphorylation -Producing ATP from anaerobic glycolysis -Producing aerobic respiration

4 major functions of skeletal muscle

-Producing body movement and storing nutrients as glycogen, proteins -Maintaining posture (upright position) -Generating heat d. Controlling entrance and exit

4 properties of muscle tissues

-Electrical excitability -Contractility -Extensibility [property of muscle gives it the ability to stretch without damage] -Elasticity [property of muscle gives it the ability to recoil]

Factors that lead to Muscle Fatigue

-Inadequate release of calcium ions from the SR -Deletion of creatine phosphate -Insufficient oxygen -Depletion of glycogen and other nutrients -Buildup lactic acid -Failure of action potentials in the motor neurons to release enough Ach

Fast fibers: Fast glycolytic fibers (FG)

-Large diameter -Produces powerful contraction -Less resistant to fatigue -Glycolytic fiber: fast fibers have fewer mitochondria and large of glycogen reserves and that why it uses anaerobic respiration -Low concentration of myoglobin (White meat)

Anaerobic endurance

-Most of the muscle's energy is produced in cytoplasm by glycolysis -Glycolysis is a main source of ATP (2ATPs) -Oxygen debts are common -Dependent on fast glycolytic fibers -Oxygen is NOT required -Muscle fatigue quickly (not able to have sustained contraction for hours)

Aerobic endurance

-Most of the muscle's energy is produced in mitochondria -Krebs cycle is a main source of ATP (36 ATPs) -No oxygen debt d. Oxygen is required -Dependent on slow oxidative fibers -Fatigue resistant (sustained contraction for hours)

Length-Tension Relationship

A muscle fiber develops its greatest tension when there is an optimal zone of overlap (sarcomere length is 2.0- 2.4 μm) between thick and thin filament. This dependency is the length-tension relationship