KSU ASI 350 Exam 1

Meat

Flesh tissues suitable for use as food; typically means skeletal muscle tissues but includes many others

Muscle evolved to \______________

Serve functions of locomotion and heat production in living animals

Lipids

•Most variable component of meat
•Comprised of neutral (triglycerides) and polar (phospholipids) components

Meat Composition: % Water

75%

Meat Composition: % Protein

18.5%

Meat Composition: % Lipid

~3.0%

Meat Composition: % Nitrogenous (non-protein)

1.5%

Meat Composition: % Carbohydrates

1.0%

Meat Composition: % Inorganic

1.0%

Most \______ and \________ occur in water.

chemical reactions and metabolic processes

Protein is composed of \________, \__________, \__________, \__________, and \__________ proteins

Contractile, regulatory, cytoskeletal, sarcoplasmic, and stromal

Carcass composition:

•45-65% muscle
•15-40% fat
•10-25% bone

Standard

Marbling grade: Select

3-4%

Marbling grade: Choice

4-9%

Marbling grade: Prime

\>9%

Muscle comprises \_____ of an animal's body mass

30-40%

Primary functions of muscle:

Movement
Support
Maintenance
Dietary protein

Skeletal muscle

Comprises the majority of muscle tissue
Voluntary contraction
Striated
Multi-nucleated
Non-branched

Cardiac muscle

Only found in heart
Involuntary contraction
Striated
Mononucleated
Branched
Intercalated discs

Smooth muscle

Found in GI, repro tract....
Involuntary contraction
Mononucleated
Non-striated
Non-branched

Sarcolemma

Cell membrane

Sarcoplasmic reticulum and T-Tubules

Release and store Ca++ during muscle contraction

Mitochondria

Powerhouse of the cell; oxidative metabolism

Myofibrils

Contractile machinery of cells; made of sarcomeres

Epimysium

Sheath surrounding entire muscle

Perimysium

Sheath surrounding muscle bundle

Endomysium

Sheath surrounding individual muscle fiber

Muscle Structure (Out-\>in)

Epimysium \> muscle \> perimysium \> muscle bundle \> endomysium \> muscle fiber \> sarcolemma \> sarcomere \> myofibril \> Myofilament

Sarcomere

Contractile unit in muscle

A-band; myosin

Thick, dark filament in the sarcomere

I-band; Actin

Light, thin filament in the sarcomere

Z-line

Forms lateral boundaries of contractile units

H-zone

Light band within A-band; no overlap of thick and thin myofilaments

Pseudo H-zone

Dark region bisecting H-zone; size remains the same; no myosin heads

M-Line

Bisects pseudo H-zone; 'holds' thick filaments in position

Thin filament

Comprised of superhelix F-actin (string of pearls, Troponin (T,I,C) and tropomysin

Troponin-T

bound to tropomyosin

Troponin-I

Inhibits interaction between actin and myosin

Troponin-C

Binds Ca++

Thick filament

Comprised primarily of myosin, which is bound together by C-proteins

C-protein

Encircles thick filament and 'clamps' myosin molecules together

Titin

Location: extends from Z-line to M-line
Function: Attaches thick filament to Z-line; maintains resting tension of muscle and keeps sarcomere aligned
(copper wire)

Nebulin

Location: originates at Z-line, extends along entire length of the thin filament
Function: believed to be a template for building and maintaining F-actin; may be help connect thin filament to Z-line
(twizzler string)

Desmin

Location: Encircles myofibril at the Z-line
Function: attaches adjacent myofibrils
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Skelemin

Attaches adjacent myofibrils at the M-Line
(little bean)

Epithelial tissue

Forms lining that covers organs
Functions: protection, secretion, excretion, transport, absorption, and sense perception

Nervous tissue

•Less than 1% of meat
Two parts:
1. Central nervous system (can't eat)
2. Peripheral nervous system (found throughout muscle)

Adipose tissue

•Energy storage
•Large impact on palatability and muscle composition
•Two types: brown and white

Brown Fat

Formed prenatally; highly oxidative and can be metabolized more quickly than white fat

Hyaline cartilage

Joint surfaces, costal cartilage, dorsal tips of vertebrae

Elastic cartilage

Epiglottis and developing bone

Fibrocartilage

Attachments of tendons and bones

\___________ can be removed from meat; \_________ and \__________ are always consumed.

Epimysium; perimysium and endomysium

Collagen forms \____% of protein and connective tissue

20-25%

Tropocollagen

•Structural unit of a collagen fibril
•Has a repeating amino acid tripeptide consisting of glycine, proline and and hydroxyproline

\__ of 12 types of collagen are found in skeletal muscle

5

Collagen cross-links are \_________

Heat degradable

Elastin (Lig. Nuchae)

•Contains AA desomine and isedesomine, which form cross-links
•Provides stability for head and neck
•More stable than collagen, heat resistant and can't be broken down
('yellow bit') (bungee cord)

Red muscle fiber

•Type I and IIA
•"slow twitch"
•Highly oxidative
•Prolonged contraction
(marathon runners)

White muscle fiber

•Type IIX and IIB
•"fast twitch"
•Low aerobic threshold
•Bursts of strength
(sprinters)

\________________ are needed for oxidative metabolism.

Mitochondria

Swine, cattle muscle fiber types

More red at birth, more white later on

Contraction

Conversion of chemical energy into mechanical energy for locomotion

Most muscle contractions are initiated by stimuli that arrive at the \_________________.

Sarcolemma

Skeletal muscle stimulus

Starts in brain and is transmitted via nerves (CNS \---\> PNS)

Motor nerves

Transmit stimuli to skeletal muscles

Transmembrane potentials

•Selective permeability (water is exception)
•Ion movement across causes electrical gradient
•Protein channels act as transporters

Resting membrane potential

•Created by disproportion of ions between inside and outside of cell
•Net negative charge inside, net positive charge outside

Resting potential is maintained through \___________

•Active transport of ions
•Selective permeability to ions/small molecules
•Unique ionic composition of intra/extracellular fluids

Na+/K+ pump

•One of the largest ATP utilizers in the body
•1 ATP\= 2 K+ out, 3 Na+ in

Action potential

•Transmission of an electrical impulse "down" a fiber's cell membrane
•Causes a wave of depolarization

Action Potential process

1. Na+ channels open after action potential depolarizes membrane
2. Na+ enters cell until it closes again by electrical gradient
3. K+ channels open and K+ cells rush out, resetting electrical gradient
4. K+ channels close, Na+/K+ pump returns to resting potential

The action potential is transferred from nerve fiber to muscle at the \_______ \_______.

Myoneural junction

Acetylcholine

Neurotransmitter that binds to sarcolemma receptors, causes depolarization of cell membrane (activates action potential)

Action potential is transmitted to the \_____________ via \___________

Sarcoplasmic reticulum; T-tubules

T-Tubules

•Continuous with surface membrane
•Brings extracellular solution into cell interior
• Contains DHP

DHP

•Dihydropyrodine receptor
•Voltage-sensitive Ca+ channels responsible for opening RYR receptors

Sarcoplasmic reticulum

•Sleeve-like structure around each myofibril
•Stores intercellular Ca+
•Contains RYR

RYR

•Ryanodine receptor
• Channel responsible for Ca+ release for muscle contraction

Contraction process - channels/receptors

1. AP arrives at triad
2. DHP receptors on T-tubules release Ca+ into cytoplasm
3. Ca+ activates RYR receptors on the sarcoplasmic reticulum
4. Stored Ca+ is released from the terminal cisternae of the SR
5. Ca+ binds with troponin-C
6. Troponin-I is moved away from actin
7. Troponin-T pushes tropomyosin away from myosin-binding site on actin
8. Myosin head binds with actin at the binding site, forming actomyosin

Myosin ATPase

Responsible for hydrolizing ATP to ADP to provide energy for contraction

Sliding Filament Theory

Swiveling action during contraction causes myosin heads to move along the thin filament, causing the sarcomere to shorten

Contraction review 1

Contraction review 2

Relaxation process

1. Cholinesterase process is released by nerve at the myoneural junction and breaks down acetylcholine
2. Sarcolemma is repolarized
3. Ca+ is reduced in the sarcoplasm and returned to the SR via the SERCA pump
4. Ca+ is released from Troponin-C
5. Troponin complex is returned to original state
6. Tropomyosin returns to blocking the actin-binding site
7. Cross-bridge is terminated, myosin slides back into resting state)
(Passive, no ATP needed)

Mg++

Complexed with ATP to inhibit actin-myosin interaction

Contraction review 3

Relaxation review

Hypertrophy

Enlargement of existing cells (prenatal, postnatal)

Hyperplasia

Multiplication of new cells; mitosis (prenatal)

Fiber type differentiation

•All muscles are Type I (red) at birth
• Eventually differentiate into white and intermediate types

Fibroblast

Precursor cell to connective tissue

Adipoblast

Precursor to adipocyte; starts to accumulate fat

Internal fat

Perirenal; pericardial; mesenteric

Intermuscular fat

Undesirable for cutability

Intramuscular fat

Marbling; accumulates after intermuscular fat

Intracellular fat

Unsaturated (not full of H+ ions)

Adipose tissue deposits

As fat % increases, \_______ and \________ %s decrease

Moisture and protein