meat science test 2

muscle tissue

basis of all movement and essential biological functions— locomotion, digestion, breathing, vision, circulation; contraction and relaxation; maintain body temperature; communication; 30-40% body mass

what are the three types of muscle tissue

skeletal, cardiac, smooth

skeletal muscle

voluntary, striated, multinucleated, non-branched

cardiac muscle

involuntary, striated, uninucleated, brancehd

smooth muscle

involuntary, non-striated, uninucleated, tapered

striation

caused by organization of protein filaments; highly organized = striated, lacking organized= non-striated

skeletal muscle overview

many sizes and shapes, origin on one side of joint and terminated in the other side of the articulation, attachment through tendon, maybe be terminated on thin sheet of connective tissue, large cells within vast network of connective tissues

tendon

dense connective tissue

what is the fascia

where the skeletal muscle sometimes terminates into a thin sheet of connective tissue

connective tissues

basis for structural integrity of a muscle

what are the three major connective tissues

epimysium, perimysium, endomysium

epimysium

separates muscles, nerves, blood vessels, at least 1 artery and 1 vein and a bundle of nerves

perimysium

separating muscle bundles (fascicles), differing amino acid composition and type of protein compared to epimysium, 20-40 muscle fibers per primary bundle, primary bundles form a secondary bundle, intramuscular fat within this

endomysium

separating muscle fibers, major connective tissues, adjacent to muscle cell membrane, responsible for meat tenderness

skeletal muscle fiber

within the fiber: muscle cell, myocyte, muscle fiber, myofiber; multinucleated; extend entire or only partial length of a muscle; sarcolemma

what is the sarcolemma

it is the basement membrane for skeletal muscle fibers

sarcolemma

cell membrane of a muscle fiber, classical bi-lipid cell membrane

t-tubule (transverse tubule)

small invagination extending deep into muscle cells

triad

t-tubules/terminal cisternae of sarcoplasmic reticulum, release calcium for muscle contraction

myofibril

unique microfilaments of muscle fibers, highly organized, cylindrical structure, extend the entire length of muscle cell, 1 μm in diameter, bathed in cytoplasm

myofibril: sarcomere

muscle unit, 2.5μm average in resting, 0.9 μm in super-contracted, 4 μm severely stretched, contains z-line

myofibril: z-line

outer boundary of sarcomere, anchor for thin filament

myofibril: thin filament

emit from z-line

myofibril: thick filament

center of sarcomere, overlap with thin filaments

myofibril: z-line and filaments

alternates light and dark banding patterns so has striated appearance

myofibril: a-band

dense area in the middle of sarcomere, location of thick filament

myofibril: h-zone

within a-band, where thin filaments terminate

myofibril: pseudo h-zone

highly dense area in the middle of sarcomere

myofibril: i- band

z-line and thin filaments of adjacent sarcomeres

myofibril: m-line

crosslinking proteins

myofibril: z-line structure

actin filaments terminate, where titin and nebulin are anchored, 1 thin filament connected by 4 z filaments

myofibril: thin filament proteins

f-actin (filamentous), g-actin (globular), cap z, troponin, tropomyosin

myofibril proteins: tropomyosin

regulatory, 2 strands along 2 f-actin molecules, 1 molecule extending 7 g-actin, cover myosin binding sites on actin sub-units of thin (actin) filaments

myofibril proteins: troponin

every 7-8 g-actins, three parts— i and c and t, i= inhibitor, c=calcium, t=tropomyosin

what protein do thick filaments mostly contain

myosin

myosin

elongated rod, has head and rod/tail and neck

parts of myosin: head/neck

heavy meromyosin (HHM)

parts of myosin: rod like tail

light meromyosin (LMM)

parts of myosin: HHM

globular head heavy S1 (enzymatic) and light portion S2 (structural, fine tuning)

parts of HHM

S1 of HHM is water soluble and enzymatic, has ATP binding pocket and actin binding site

proteins in actin filament

g-actin, f-actin, troponin, tropomyosin

proteins in myosin filament

myosin (LMM, HHM), c-protein

myofibril proteins: titin

close and parallel to thick filament

myofibril protein: nebulin

close and parallel to thin filament, anchor thin filament to z-disk

proteins in m-line

myomesin, skelemin, stabilizing thick filament

protein in z-disk

alpha actinin, cap z, costameres

what is action potential

momentary change in electrical membrane potential, in neurons - nerve impulse, electrochemical process

action potential: electrical potential

difference in net charge

action potential: extracellular fluid

high concentration of Na and Cl

action potential: intracellular fluid

high concentration of K

action potential: resting potential of neuron and muscle cell membrane

-70 mV -90 mV

how is resting potential maintained

by sodium potasium ATPase

action potential: steps

depolarization, repolarization, redistributing ions while maintaining resting potential

action potential: step 1 ( depolarization )

sudden and drastic increase in permeability of Na, causing reversing potential

action potential: 2nd step ( repolarization )

reestablishing resting potential, at max reverse potential potassium has outward diffusion to reestablish resting potential

action potential: during step 1 and 2

by depolarization current, stimulate N channels in the adjacent region to depolarize the next region, domino effect

action potential: 3rd step ( redistributing ions while maintaining resting potential )

sodium potassium pump (ATPase) redistributes Na outwards and K inwards while maintaining resting potential, pump works continuously during action potential and during resting

when does action potential start

with a sudden increase in Na permeability

acetyl choline

neurotransmitter increasing Na permeability released at motor end plate of neuron containing sarcolemma

what are the nine events that happen at the neuromuscular junction

1. action potential travels to axon terminal of motor neuron

2. voltage gates calcium channels open, calcium diffuses into axon terminal

3. acetylcholine is released into the synaptic cleft

4. acetylcholine binds to receptors at the motor endplate

5. ligand-gated cation channels open, Na enters muscle fiber and K exits for depolarization

6. -7 voltage gated Na channels open leading to an action potential

8. action potential propagates along the sarcolemma and into t-tubules

9. acetylcholine esterase breaks down acetylcholine

calcium release from sarcoplasmic reticulum: terminal cisterna

action potential travel from sarcolemma to t-tubules, t-tubules connect with SR, calcium released from the SR to sarcoplasm, calcium triggers the contraction

what receptor is in t-tubules in concern to contraction

dihydropyrideine receptor

what channel is in terminal cisterna is regards to muscle contraction

calcium channel

what are the three ways muscles generate ATP

creatine phosphate, anaerobic glycolysis, aerobic respiration

creatine phosphate

fastest method of ATP production but lasts only 10-15 seconds, uses creatine phosphate stored in the muscle to rapidly regenerate ATP, no oxygen required (anaerobic), 1 creatine = 1ATP

anaerobic glycolysis -short term energy

breaks down glucose or glycogen to produce ATP, does not require oxygen, produces ATP quickly but generates lactic acid which can cause muscle fatigue, provides energy for 30 seconds to 2 minutes, 1 glucose = 2 ATP

anaerobic

glycolytic metabolism in sarcoplasm, using glucose or glycogen

aerobic respiration (oxidative phosphorylation) -long term energy

occurs in the mitochondria and requires oxygen, uses glucose and fatty acids and sometimes proteins to generate ATP, produces much more ATP than anaerobic processes but is slower, provides energy for long-duration and low intensity activities, 1 glucose = 36 ATP

aerobic

oxidative metabolism in mitochondria, using pyruvate or acetyl CoA

muscle fiber typing

using two characteristics that differ among muscle fiber types

what are the two characteristics that are used in muscle typing

speed of contraction, metabolic pathway used to produce ATP

what are the two types of muscle fibers

slow twitch (type 1) and fast twitch (type 2)

type 1 fibers features

mitochondria- high, myoglobin- high, capillary density- high, energy source- aerobic, contraction speed- slow, fatigue resistance- high, primary function- endurance, color- red

type 2 fiber typing

mitochondria- low, myoglobin- low, capillary density- low, energy source- anaerobic, contraction speed- fast, fatigue resistance- low, primary function- short and explosive power, color- white or pink

muscle fiber type- color

difference caused by ratio of muscle fiber types in muscles, red fibers, white fibers, shades of color ranging between deep red to off-white

muscle fiber type: irregularities

functionality differences of regions within the same muscle, pig semitendinous— varying shades of red to white and superficial portion has 80% white fiber with20% red fiber and deep portion has 80% red fiber with 20% white fiber

oxidative fiber- type 1

great oxidative enzyme activity and more myoglobin and more redness, low glycolytic markers and less glycogen and smaller sarcoplasm = smaller diameter, low ATPase activity, low peak force and very fatigue resistant because producing more ATP and using ATP at slower rate, tonic mode of action - slow but sustained, more and larger mitochondria because they are needed for oxidative metabolism

glycolytic fibers- type 2 B

low oxidative enzyme activity, high glycolytic markers and need more glycogen, high ATPase activity, high peak force and fatigue susceptible because producing less ATP but using much of it, phasic mode of action- short burst but quick fatigue

type 1 (slow twitch) pH

higher pH, oxidative metabolism, lower glycogen stores, slower rate of post mortem pH decline

type 2B (fast twitch) pH

lower pH, anaerobic glycolysis, higher glycogen stores, rapid postmortem pH decline

type 1 and meat tenderness

more tender meat, smaller fiber diameter, higher intramuscular fat content, lower collage cross-linking

type 2B and meat tenderness

tougher meat, larger fiber diameter, lower lipid content

which muscle fiber is more tender

type 1

which muscle fiber has higher water-holding capacity

type 1

which muscle fiber has a higher pH

type 1

which muscle fiber has a more complex flavor

type 1

type 1 muscle fiber flavor profile

more complex flavor, higher IMF, more mitochondria which are flavor enhancing enzymes and phospholipids, higher levels of amino acids and nucleotides, longer chain fatty acids

type 2B muscle fiber flavor profile

less complex flavor, lower IMF, less mitochondria which are flavor enhancing enzymes and phospholipids, fewer fat soluble flavor compounds

type 1 oxidative stability

darker meat, higher myoglobin which is a pro-oxidant, more mitochondria which is auto oxidizing membrane phospholipids, higher levels of polyunsaturated fatty acids, increased iron content which is catalyst for oxidation

type 2B oxidative stability

lighter meat, lower myoglobin, fewer mitochondria, higher proportion of saturated fats, lower iron content

moisture

water is most important functional component, carrier of intra and inter cellular constituents, inversely related to fat: increase fat = decrease water, affects initial juiciness

protein

average 18.5%, least variable, composed of amino acids, worldwide shortage, most critical nutrients

essential proteins

Phenylalanine (Phe), Valine (Val), Tryptophan (Trp), Threonine (Thr), Isoleucine (Ile), Methionine (Met), Histidine (His), Arginine (Arg), Leucine (Leu), Lysine (Lys)

how to remember essential proteins

PVT TIM HALL

protein types

myofibrillar, sarcoplasmic, stromal

Myofibrillar

9.5%, principal ones are actin and myosin

Sarcoplasmic

6%, enzymes and pigments, the two principal pigments are myoglobin and hemoglobin, hemoglobin in red blood cells carries O2 from lungs to cells, myoglobin store O2 in cells

stromal

3%, connective tissues are 10-15 % muscle proteins— collagen and elastin and reticulin, the skeleton of a muscle,

collagen

predominates and can affect tenderness greatly as an animal ages, forms a network and becomes less tender, degrades to gelatin at 65 degrees C with moist heat cookery, most abundant protein in animal body, 20-25% of total body protein, skin and sinews and tendons

elastin

ligamentum nuchae, does not degrade with moist heat, gives elasticity to arterial walls