Chapter 10 Muscle Tissue

Front 1

Characteristics of Muscle Tissue

Back 1

Excitability: Responsiveness to electrical stimuli

Conductivity: Ability to transmit electrical impulses

Contractility: Ability to contract and generate force

Extensiblity: Ability to extend fiber length

Elasticity: Ability to recoil back to original length

Front 2

Muscle Components

Back 2

Whole Muscle:

Muscle Fascicles (10 or more groups of muscle fibers) > Muscle Fibers > Myofibrils (contractile organelles) > Protein filaments

Front 3

Connective Tissue Components

Back 3

Periosteum > Tendon > Epismysium (encircle entire muscle) > Perimysium (surrounds muscle fascicle) > Endomysium (separates individual muscle fibers from one another)

Front 4

Neuromuscular Junction

Back 4

Place where an axon from a motor neuron comes into close contact with muscular fiber

Front 5

Skeletal Muscle Fiber Characteristics

Back 5

Sarcolemma: plasma membrane

Sarcoplasm: Cytoplasm

Sarcoplasmic Reticulum (SR): Smooth ER, stores calcium ion

T-tubules: Invaginations of the sarcolemma, filled with interstitial fluid

Myofibrils contain Myofilaments

Front 6

Components of a Myofibril

Back 6

Thick filaments: Myosin

Thin filaments: Actin, Troponin, Tropomyosin

Front 7

Myosin

Back 7

*Composed of Sticky heads and tail

Myosin proteins overlap to form the thick filament

The sticky heads protrude from the surface of filament in all directions

Front 8

Actin

Back 8

Globular actin proteins that form bread-like strands are thin filaments

Embedded in the strands are Troponin and Tropomyosin

** Contains binding sites for myosin called Myosin-binding sites

Front 9

Troponin

Back 9

Complex of proteins with binding sites for Actin, tropomyosin, and calcium ions

Front 10

Tropomyosin

Back 10

Fibrous proteins that binds to Actin and Troponin

It covers myosin-binding sites on actin molecules

Front 11

A band detail

Back 11

* Located in Darker middle part of Sarcomere and is the entire length of thick filament

Front 12

I band detail

Back 12

* Located in Lighter, less dense area and only contain thin filaments

Front 13

H zone detail

Back 13

* Located in the Center of each A band and only contain thick filaments

Front 14

M line detail

Back 14

* Located in the middle of Sarcomere and it support proteins that hold thick filaments together

Front 15

Z discs detail

Back 15

* Separate Sarcomeres from each other and is the plate-shaped regions of dense proteins

Front 16

Molecular events of Muscle Contraction

Back 16

Sliding filaments mechanism: Thick and Thin filaments slide against each other

Thin filaments move

Thick filaments stay stationary and Sarcomeres shorten

Front 17

Roles of Calcium in Sliding Filaments

Back 17

**Calcium Ion binds to Troponin and changes it's shape

** Tropomyosin pulls away from myosin-binding sites on actin molecules

Front 18

Steps of Filament Sliding

Back 18

**Myosin binds to myosin-binding site on actin and changes it's shape

**Actin slides against Myosin toward M line (center of Sarcomere)

Front 19

Role of ATP

Back 19

ATP is used to break the bond between Myosin and Actin

** Binding: Requires calcium ions

** Breaking: Requires ATP

**Cycle of binding and breaking repeats over and over again

Front 20

Relaxed Muscle Fiber

Back 20

** Calcium Ion channels are closed in membrane of SR

**Troponin holds Tropomyosin in position to block Myosin-binding sites on Actin

Front 21

Excitation-Contraction Coupling

Step 1

Back 21

Primary motor area of Cerebral cortex of brain stimulates motorneuron in Spinal cord

Front 22

Excitation-Contraction Coupling

Step 2

Back 22

Axon of motor neuron begins to transmit electrical impulse towards the axon terminal

Front 23

Excitation-Contraction Coupling

Step 3

Back 23

**Impulse arrives

** Calcium channels open in the membrane of the axon terminal

** Calcium ions diffuse into the axon terminal

Front 24

Excitation-Contraction Coupling

Step 4

Back 24

** Calcium ions stimulate movement of vesicles to the axon membrane

** Acetylcholine (ACh) is released into Synaptic Cleft by Exocytosis

Front 25

Excitation-Contraction Coupling

Step 5

Back 25

** Acetylcholine binds to ACh receptors

** ACh receptors are located on Na+ ligand-gated ion channels embedded within Sarcolemma

Front 26

Excitation-Contraction Coupling

Step 6

Back 26

** Binding of ACh to ACh receptor opens Na+ ligand-gated channel

** Small cations, mostly Na+, can flow across Sarcolemma into Sarcoplasm, which generates an electrical impulse in the muscle fiber

** Impulse travels along Sarcolemma

Front 27

Excitation-Contraction Coupling

Step 7

Back 27

** Electrical impulse dives down into T-tubules

**It causes voltage-gated calcium ion channels in the membrane of Sarcoplasmic Reticulum (SR) to open

Front 28

Excitation-Contraction Coupling

Step 8

Back 28

** Calcium ions diffuse out of the SR through these calcium channels into the Sarcoplasm

Front 29

Excitation-Contraction Coupling

Step 9

Back 29

** Calcium ions bind to Troponin on thin filament and changes it's shape

** Tropomyosin pulls away from Myosin-binding sites on Actin molecules

**Myosin sticky head attaches to sites on Actin

*Then thin filaments slide towards M-line and Sarcomere shortens

Front 30

Excitation-Contraction Coupling

Step 10

Back 30

** Pumping Calcium ions from Sarcoplasm back into SR

**This active transport mechanism requires ATP

** Muscle contraction stops when calcium ions are eliminated from Sarcoplasm

Front 31

Acetylcholinesterase (AChE)

Back 31

** Enzyme that breaks down ACh within the Synaptic Cleft

** ACh levels decreases and muscle fiber stops contracting

Front 32

Myogram Twitch Contraction

Back 32

** The response in a muscle fiber after electrical stimulation

**Has three phases:

1) Latent period

2) Contraction period

3) Relaxation period

Front 33

Latent Period

Back 33

**Time before contraction begins

** Includes all the events of Excitation-contraction coupling and release of calcium ions from SR

Front 34

Contraction Period

Back 34

**When contraction happens

** Myosin-Actin binding and breaking and Sarcomere shortening

** Muscle fiber is generating force now

Front 35

Relaxation Period

Back 35

**Calcium ion is being pumped back into SR

**Muscle fiber is generating less force

Front 36

Muscle Metabolism

Back 36

Requires ATP and is used for: Breaking bonds between Myosin and Actin then pumping calcium ion back into SR

Front 37

Creatine Phosphate

Back 37

**Muscle fibers store creatine phosphate and is a readily available source of ATP

** Used for quick bursts of activity (last up to 15 seconds)

Cr-PO4- creatine phosphate

Cr-PO4 + ADP >> Creatine + ATP

Front 38

Anaerobic Glycolysis

Back 38

**ATP production have been depleted and takes place in cytosol; Does not require oxygen

**Glucose >> Pyruvic acid (Lactic Acid)

2 ATP's are produced for every glucose molecule

**Used for longer periods of physical activity ( 30 to 40 seconds)

Front 39

Aerobic Cellular Respiration

Back 39

** Requires oxygen and takes place in Mitochondrion

**Its used for long periods of physical activity

Pyruvic acid >> CO2 + H2O + Heat

34 more ATP's are produced

Front 40

Cardiac Muscle

Back 40

**Muscle tissue of the heart and is controlled by ANS

** Has same arrangement of proteins and bands

** Intercalated discs contain desmosome and gap junctions; Mitochondria larger than Skeletal muscle

**Requires constant supply of oxygen and use lactic acid produced by skeletal muscle fibers

Front 41

Smooth Muscle

Back 41

Muscle tissue of all organs, has no striations, sarcomeres, and T-tubules; Controlled by ANS

Has two types:

1) Visceral 2) Multiunit

Front 42

Visceral (Single Unit) Smooth Muscle

Back 42

**ANS neuron stimulates muscle fibers

** Gap junctions spread electrical impulse to other fibers and contractions occurs as one unit

** Located: Small arteries and veins, Hollow organs such as stomach, intestines, uterus

Front 43

Multiunit Smooth Muscle

Back 43

**Every muscle fiber has its own ANS neuron

** Only a few gap junctions and individual contractions occur

**Located: Arrector pilli muscles, Airways to lungs, Large arteries such as Aorta

Front 44

Autonomic Nervous System (ANS)

Back 44

**Control both Smooth and Cardiac Muscles**

** Sympathetic subdivision: prepares body for energy expanding, emergency situations like "fight and flight" response

** Parasympathetic subdivision: Maintains body during non-energy, "resting and digesting"