muscle type and contraction

skeletal muscle

-body movements, voluntary -striated, tubular, multinucleate fibers -attached to bone. -fatigue

hemoglobin

-color in blood -globular protein involved in oxygen transport -hemoglobin allows 4 O2 to bind

cardiac muscle

-found in heart, involuntary -striated, branched uninucleate fibers -only in heart and fatigue resistance

smooth muscle

-intestines,blood vessels, uterus; involuntary -spindle shaped, nonstraited uninucleate fibers; fatigue resistant

tropomyosin

-regulatory component of actin filaments -long molecules comprising of a coil of alpha helices

sarcomere

-the smallest functional unit ofa skeletal muscle fiber and is a highly organized arrangement of contractile, regulatory, and structural proteins. -The contractile unit of muscle and it is responsible for muscle contraction -region between 2 adjacent Z disks

actin

Actin is the contractile protein that forms the thinfilaments. • All acting filaments are of the same length and contain myosin binding sites, to which the myosin heads attach and 'walk' along. This results in contraction

connective tissue

Cells are wrapped in bundles of connective tissue, divided into threelevels of organization: -endomysium -perimysium -epimysium

muscle bundle (fascicle)

Composed of bundles of muscle fibers (musclecells) .• The number of fibers varies from 50 to 300 in each bundle. Power muscles have larger muscle bundleand larger fibers .• Surrounded by a connective tissue called the perimysium.

sarcomere I band

I- isotropic uniform in each direction, thin filaments (actin) anchored by Z disks by actin -light band striation

Sarcolemma

Muscle fibers are surrounded byplasma membrane called the sarcolemma, which contains cytoplasm known as sarcoplasm • Sarcolemma is a lipid bilayer (60%protein, 20% phospholipid, 20%cholesterol): the reason that meat contains a significant amount of cholesterol

muscle (meat) as food

Muscle tissue is converted into meat by postmortem changes occurring after death of the animal The properties of muscle determine the flavor, tenderness and texture of meat

myosin

Myosin is the contractile protein that forms the thickfilaments. • Myosin is the most abundant myofibrillar protein, accounting for more than 40% of the myofibrillar proteins in skeletal muscle• It lies mainly in the A-band and H-zone of thesarcomere and interacts with actin to create movement .• Myosin filaments are made up of three domains:head, tail, and neck.

myosin function

Myosin mainly involves coupling hydrolysis ofATP to conformational changes in the head region of thefilament that enables it to bind and move along actinfilaments.

action potential depolarizes the

SR (sarcoplasmic reticulum) and releases calcium from the SR

sarcoplasmic reticulum (SR)

Sac-like membranes • It contains large, concentrated stores of calcium .• Stores Ca2+ in relaxed muscle • Release of Ca2+ triggers muscle contraction

traverse tubules (T-tubule)

Sarcolemma is invaginated in places to formmembranous tunnels known as transversetubules or T tubules. • The tubules penetrate through the fiber andconduct electrical stimuli from the sarcolemma.

movement of the body

Skeletal movement :production of force and movement, supporting of the body,changing of body posture, stability of joints Blood flow (heart and blood vessels) Movement of food through the digestive system

composition of meat (skeletal muscle)

Skeletal muscle is complex organ(muscular system) Each muscle consists of skeletal muscletissue, connective tissue, nerve tissue,and blood or vascular tissue.Anatomy of skeletal muscle

sarcomere appearance

Striated appearance: arrangement of thick andthink filaments within sarcomere

endomysium

The endomysium is a thin layer of connective tissue that surroundseach muscle fiber (cell). -location: skeletal muscle fiber/myofiber

epimysium

The epimysium is a sheet of thick connective tissue that surroundsthe entirety of a skeletal muscle- Intermuscular fat (Seam fat)deposited within the epimysium. It separates the muscle fromsurrounding tissues and organs

perimysium

The perimysium is a thick layer of connective tissue that groups the muscle fibers into fascicles. Intramuscular fat (marbling) is fatdeposited within the perimysium. It protects the fascicle fromdamage and contains capillaries and nerve fibers to allow nutrienttransfer within the muscle -seperating. bundles (fascicles)

Sarcoplasm

The sarcoplasm is the cytoplasm of the cell and contains large amounts of glycogen and myoglobin .• Glycogen provides energy during muscle contraction while myoglobin contains stored oxygen

sliding filament mechanism movement

This movement causes sarcomere shortening because the thin filaments are attached to the Z-line, and thethick filaments are able to grip their way along, makingthe H-zone almost non-existent. The combined shortening of the sarcomeres along a number of myofibrils causes whole muscle contraction

troponin

Troponin is a regulatory component of actin filaments. It is involved in moving tropomyosin away from the myosin binding site on actin filament

composition of meat made up of

blood vessel, nerve tissue, muscle fibers (muscle cells), connective tissue, adipose tissue (fat)

actin function

bound to myosin molecules

muscle contracted initiated by

by an electrical impulse (actionpotential) that travels down the motor nerve to themyoneural junction.

at a neuromuscular synapse an action potential is converted into a

chemical signal travels across the synapse, enables neuron to communicate with adjacent muscle cell

stromal proteins

collagen, elastin, keratin

myoglobin

color of muscle tissues -globular protein-heme ring with Fe in center -shape of myoglobin allows one O2 to bind

3 main types of myofibrillar proteins

contractile proteins, regulatory proteins, structural proteins

regulatory proteins control

contraction

body homeostasis

e.g. Thermogenesis Skeletal muscles contribute to maintaining temperature homeostasis in the body by generating heat

intramuscular fat (marbling)

fat deposit within perimysium

action potential travels into

interior of fiber via T-tubules

fat deposit within epimysium

intermuscular fat (seam fat)

tropomyosin function

involved in uncovering of myosin head binding sites on actin filaments

muscle fibers: mitochondria

located near muscle proteins use ATP for contraction

muscle fiber (muscle cell)

made up of protein structure called myofibril covered by connective tissue called endomysium

sarcomere H zone

middle of A band

action potential causes

motor nerve to release chemical acetylcholine (Ach)

function of muscle

movement of the body, body homeostasis, muscle (meat) as food

perimysium location

muscle bundle

muscle fiber=

muscle cell=myofiber

muscle fibers: nucleus

muscle fibers are multinucleate cells (more than 2 nuclei) -each muscle fiber contains multiple flattened nuclei lie beneath sarcolemma

55% of protein in muscle cell is

myofibril protein including actin, myosin

sarcoplasmic proteins (involved in color of meat)

myoglobin and hemoglobin

contractile proteins

myosin and actin

myofibrils are made up of repeating subunits

sarcomeres

muscle contraction cycle

series of events cause contraction of sarcomere, contractile unit of muscle fibers

epimysium location

skeletal muscle

anatomy of skeletal muscle

skeletal muscle, muscle fascicle, muscle fiber, myofibril

skeletal muscle structure in order

skeletal muscle->muscle bundle->skeletal muscle fiber/myofiber->myofibril->myofilaments (actin, myosin)

Types of muscles

skeletal, smooth, cardiac

sarcomere A band

thick filaments (myosin) spans center of sarcomere and extends toward Z disk -Dark striation

muscle contraction occurs because

thick filaments bindonto the thin filaments by forming chemical bondscalled crossbridge. Once bound, the thick filaments 'walk' along the thinfilaments and pull them towards the center of thesarcomere.

sarcomere M line

thin line in middle of thick myosin filaments

structural proteins

titin, nebulan, dystrophin

regulatory proteins (control contraction)

troponin and tropomyosin

chemical composition of muscle

water, proteins, myofibrillar proteins, sarcoplasmic proteins, stromal proteins, lipid, carbohydrate, inorganic constituents

myofibrils

• Each myofibril is composed of bundles known as myofilaments which are arranged into the contractile elements of a muscular cell, i.e., the sarcomere Within a muscle fiber, proteins are organized into structures called myofibrils