Anatomy Chapter 9 Muscles And Muscle Tissue

Front 1

Muscles

Back 1

Distinguished by their ability to transform chemical energy (ATP) into directed mechanical enregy. In doing so, they become capable of exerting force

Front 2

- Can send an action potential

- Can contract

- Can stretch

Back 2

Characteristics of muscle tissue (3)

Front 3

Skin (Epidermis & Dermis)

Hypodermis (Adipose tissue & superficial fascia {another layer of loose fatty connective tissue})

Deep Fascia (Dense regular connective tissue)

Back 3

To get to the muscle we must get through 3 layers

Front 4

Fascicles

Muscle Fibers

Myofibrils

Myofilaments

Back 4

Muscle is an organ composed of ____________, which are made of _____________, which are made of ___________________, which are made of _________________.

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Fascicles

Back 5

Bundle of Muscle Fibers (Cell)

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Muscle Fibers

Back 6

Made up of myofibrils,

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Myofibrils

Back 7

Contain the contractile elements of skeletal muscle cells, the sarcomere, which contain even smaller rod like structures called of myofilaments

Front 8

Myofilaments

Back 8

Filaments of myofibrils, constructed from proteins, principally myosin or actin

Front 9

Actin: Thin filaments

Myosin: Thick filaments

Back 9

Myofilaments (2 types)

Front 10

Endomysium

Back 10

What is the membrane that encloses individual muscle fascicles?

Front 11

Perimysium

Back 11

What is the membrane that encloses all the muscle fascicles in a muscle?

Front 12

Epimysium

Back 12

What is the membrane enclosing the skeletal muscle?

Front 13

Sarcomere

Back 13

Region of a myofibril between two successive Z discs

- Smallest contractile unit of a muscle fiber - the functional unit of skeletal muscle

- Contains an A band flanked by half an I band at each end

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Sarcolemma

Back 14

Analogous to the Cell membrane, but of the skeletal muscle fiber

Front 15

Sarcoplasm

Back 15

Analogous to Cytoplasm of a muscle cell

- Contains unusually large amounts of glycosomes (stored glycogen granules) and myoglobin (red pigment that stores oxygen)

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Sarcoplasmic Reticulum

Back 16

- Analogous to Endoplasmic Reticulum

- Surround each myofibril

- Stores calcium and releases it on demand for muscle contraction

Front 17

Striations

Think MHAIZ

Back 17

Arrangement of myofilaments in the cell into sarcomeres, dark A bands and light I bands

- Each dark A band has a lighter region in the middle called H zone)

- Each H zone is bisected vertically by dark line called M line formed by myomesin proteins

- Each light I bind also has midline interruption, darker area called Z disc

Front 18

I Band

Back 18

- Region with Actin filaments only, with Z disc in middle

- Thus appears "lighter"

Front 19

H Band

Back 19

- Region in the Middle of A Band, contains vertical M line

- Consists of thick filaments

Front 20

A Band

Back 20

- Region of sarcomere with Thick and thin filaments with the vertical M line in the middle

- Thus appears "darker"

Front 21

Tropomyosin

Troponin

Back 21

2 Types of regulatory proteins holding actin in place

Front 22

Tropomyosin

Back 22

- Rod-like protein that spirals about the acting core to help stiffen and stabilize it

- Block myosin-binding sites on actin

Front 23

Troponin

Back 23

- Globular protein on the actin filament that binds calcium ions

Front 24

Titin

Back 24

- Elastic filament composed of a giant protein that extends from Z disc to the thick filament myosin, then runs within the thick filament to attach to M line

- Helps muscle spring back into shape after stretching

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Myosin

Back 25

- Thick type of myofilament with the ability to break down ATP

- Ability to pivot

- Ability to attach to actin

- Extend entire length of A band, connected in the middle of the sarcomere at the M line

Front 26

Actin

Back 26

- Thin filaments extend across the I band and part way into A band, Z band anchors the thin filaments

Front 27

T-Tubule

Back 27

At each A band, I band junction, the sarcolemma of the muscle protrudes deep into the cell interior, forming an elongated tube vertically

- Increase the muscle fiber's surface area

- Conduct impulses to the deepest regions of the muscle cell and every sarcomere for the release of calcium

Front 28

Sliding filament theory

Back 28

- Action potential down sarcolemma

- Calcium release

- Calcium binds to troponin

- Twists tropomyosin off binding sites

- Myosin binds to actin

- Myosin heads (cross bridges) ratchet

- Sarcomere shortens

Describes what theory?

Front 29

- I Bands shorten

- Distance between Z disc shortens

- H zones disappear

- A bands move closer together, but length does not change

Back 29

When muscle cell contracts, what are the 4 things that happen along the sarcomere?

Front 30

Path of action potential

Back 30

- Calcium binds to and enters the synaptic bulb of motor neuron

- Acetylcholine released into synaptic cleft

- Acetylcholine binds to acetylcholine receptors

- Action potential sent across sarcolemma and down T-tubules

- This occurs because Na+ which is normally outside cell gets pumped into cell membrane

- Changes to more positively charged inside membrane and this charge travels down

- This action potential then triggers Calcium release from sarcoplasmic reticulum which diffuses into cell and acts further in muscle contraction

Front 31

Excitation of Muscle Cell

Back 31

- Nerve signal arrives at synaptic bulb

- Calcium enters synaptic bulb through voltage gated calcium channels

- Acetylcholine released from synaptic bulb by exocytosis

- ACH binds to ligand (chemically) gated ion channels at sarcolemma, channels change shape and open

- Na diffuses in, K diffuses out

- Causes voltage change inside sarcolemma

- Voltage gated ion channels open - more Na comes in

- Action potential, muscle fiber excited

- Action potential travels along sarcolemma down T-tubules

- Voltage gated ion channels in T-tubules open and calcium channels in sarcoplasmic reticulum open

- Calcium rushes into cytosol of muscle cell

Front 32

After calcium release

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- Calcium binds to troponin

- Causes tropomyosin to change position

- Myosin binding sites are exposed on actin

- Myosin heads attach, thus contraction occurs

- After, calcium goes back into sarcoplasmic reticulum (ATP required)

Front 33

Calcium Pump (Into sarcoplasmic reticulum)

Na/K Pump

Kinking of myosin head

Back 33

ATP is required for 3 processes in the muscle fiber/cell?

Front 34

- Anaerobic & Aerobic Pathways

- Stored glycogen in cell

Back 34

ATP comes from? (2)

Front 35

Muscles at rest

Back 35

- Minimal ATP needed

- Excess ATP will donate phosphate to creatine

- CREATINE PHOSPHATE formed

- Held in reserve for use later

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High muscle activity

Anaerobic

Back 36

- Not enough oxygenated cells

- Glycogen in sarcoplasm breaks down to glucose

- Glucose into Pyruvic acid and 2 ATPs formed in the process

- Pyruvic acid turns into lactic acid

- Creatine phosphate donates phosphate to ADP forming ATP

- Used for quick, powerful contractions

- Muscle fatigues quickly

Front 37

Moderate activity

Aerobic

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- Enough oxygen in cells stored by the protein myoglobin

- Glycogen to Glucose to Pyruvic acid (2 ATPs made)

- Pyruvic acid to Mitochondria to 34 ATPS

- Used for longer periods of contraction

- No fatigue

Front 38

Anaerobic Pathway to create ATP

Back 38

- Creatine phosphate + ADP => Creatine + ATP

- Glucose broken down to 2 Pyruvic acid molecules (releasing 2 ATP per glucose), then during no oxygen, converts to lactic acid

Front 39

Aerobic Respiration

Back 39

Glucose + O2 => CO2 + H2O + ATP

Provides about 32 ATP per glucose, but slower process than anaerobic

Front 40

Fast glycolytic fibers

Back 40

- Most muscles fibers are these

- Large diameter

- No myoglobin - White color

- Anaerobic ATP production

- Quick powerful contraction, short-term intense

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Slow oxidative fibers

Back 41

- Fibers are smaller in diameter

- Lots of Myoglobin - Red color

- Aerobic ATP production

- Longer contraction for endurance

Front 42

Type I (slow-oxidative) Fibers

Back 42

- Fiber color: Red
- ATPase activity: Low

- Contraction speed: Slow

- Glycolytic enzymes: Low

- Mitochondrial content: Packed

- Fatigue resistance: High
- Myoglobin content: High

- Vascularization: Extensive
-Motor unit size: 100+ fibers

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Type IIa (fast-oxidative) Fibers

Back 43

- Fiber color: Red

-Motor unit size: 2-6 fibers

- ATPase activity: High
- Contraction speed: Fast

- Myoglobin content: High
- Fatigue resistance: Intermediate

- Glycolytic enzymes: Intermediate

Front 44

Type IIb (fast-glycolytic) Fibers

Back 44

- Fiber color: White

- Vascularization: Average

-Motor unit size: 2-6 fibers

- ATPase activity: High

- Contraction speed: Fast
- Glycolytic enzymes: High

- Fatigue resistance: Low

- Myoglobin content: Low

- Mitochondrial content: Sparse

Front 45

Motor Unit

Back 45

1 motor neuron and all of the muscle fibers it innervates

Front 46

Change the number of motor units stimulated

Back 46

How do we vary the degree of contraction?

Front 47

Small Motor Unit

Back 47

- Motor neuron controls only 5-6 muscle fibers

- Allows precise control

- Ex: Eye and finger muscles

Front 48

Large Motor Unit

Back 48

- Motor neuron controls 1000-2000 muscle fibers

- Less precise control

- Ex: Leg muscle

Front 49

Muscle Tone

Back 49

- Due to spinal reflexes that activate first one group of motor units and then another in response to activated stretch receptors in the muscles

- Motor units "switching" on and off

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Hypertrophy

Back 50

- Muscle cells enlarge

- More myofibrils

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Atrophy

Back 51

- Smaller muscle cells

Front 52

Muscle Twitch

Back 52

- Motor unit's response to a single action potential of its motor neuron

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Myogram

Back 53

- "Picture" of the contraction of a motor unit

- Typically depicts three phases
Latent Period

Period of Contraction

Period of relaxation

Front 54

Wave Summation / Incomplete Tetanus

Back 54

- More than one stimuli are delivered to a muscle in rapid succession, the second twitch will be stronger than the first, because it occurs before the muscle has completely relaxed

- Contractions are added together

Front 55

Complete Tetanus

Back 55

- Sustained muscle contraction evoked when the motor nerve that innervates a skeletal muscle emits action potentials at a very high rate

- Reaches maximal tension, all evidence of muscle relaxation disappears and contractions fuse into smooth, sustained contraction plateau

Front 56

Treppe

Back 56

- The graduated series of increasingly vigorous contractions that results when a corresponding series of identical stimuli is applied to a rested muscle—called also staircase effect, staircase phenomenon

Ex: Lifting small weights repeatedly

Front 57

Isometric Contraction

Back 57

When weight applied and tension increases:

- Muscle length is constant

- Because Weight exceeds muscle's maximal tension

- Ex: Carrying a bag of groceries

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Isotonic Contraction

Back 58

When weight applied and tension increases:

- Muscle length shortens

- Ex: Lifting an object, running

Front 59

Cardiac Muscle

Back 59

Characteristics: Branched cells, intercalated disks (Gap junctions, desmosomes)

Sarcomeres: Yes

Motor Neurons: No (Involuntary)

Energy Source: Lactic acid

Role of calcium: Yes

Tetanus: No, contractile strength increases with degree of stretch

Front 60

Cardiac Muscle

Back 60

Sarcomeres: Yes

Motor Neurons: No (Involuntary)

Energy Source: Lactic acid

Role of calcium: Yes

Tetanus: No, contractile strength increases with degree of stretch

Front 61

Smooth Muscle

Back 61

- Dense bodies anchor actin filaments instead of tropomyosin, tethered to sarcolemma, act like Z discs of skeletal muscle

- No T-tubules, only caveolae

- Underdeveloped sarcoplasmic reticulum

- Calmodulin in cytosol regulates calcium instead of troponin

- Lattice-like intermediate filaments

Front 62

Caveolae

Back 62

Pouch like in foldings containing large number of Ca2+ channels, allowing Calcium influx more so than the underdeveloped sarcoplasmic reticulum in the smooth muscle fiber

Front 63

Stripes

Back 63

When describing muscle, what does "striated" mean?