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Anatomy & Physiology Review I > Chapter 10 - Muscle Tissue > Flashcards

Chapter 10 - Muscle Tissue Flashcards

1
Q

What are the 3 Types of Muscular Tissue?

A

Skeletal Muscle
Cardiac Muscle
Smooth (Visceral) Muscle

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2
Q

What is the Location, Function, Appearance, and Control of Skeletal Muscle?

A

Location:
Skeletal

Function:
Move bones

Appearance:
Multi-nucleated
Striated

Control:
Voluntary

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3
Q

What is the Location, Function, Appearance, and Control of Cardiac Muscle?

A

Location:
Heart

Function:
Pump blood

Appearance:
One nucleus
Striated
Intercalated Discs

Control:
Involuntary

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4
Q

What is the Location, Function, Appearance, and Control of Smooth (Visceral) Muscle?

A

Location:
Various organs
Like GI Tract

Function:
Various functions
Like Peristalsis (moving food through GI Tract)

Appearance:
One nucleus
No striations

Control:
Involuntary

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5
Q

Which muscle has the Fastest Contractions?

A

Skeletal then Cardiac then Smooth

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6
Q

Which muscle has the Strongest Contractions?

A

Smooth then Cardiac then Skeletal

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7
Q

What are the Functions of Muscular Tissue?

A

1- Producing body movements
2- Stabilizing body positions
3- Storing and mobilizing substances within the body
4- Generating heat

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8
Q

What are the Properties of Muscular Tissue?

A

1- Electrical Excitability:
Neurons release neurotransmitters at synaptic joint
Neurotransmitters attach to receptors on muscles
Muscle contracts

2- Contractility

3- Extensibility

4- Elasticity

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9
Q

How is Muscle Formed?

A

Myoblasts fuse into skeletal muscle fiber
Myoblasts that didn’t fuse with others becomes Satellite cell
immature muscle fiber is made

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10
Q

What are the Components of Muscle Tissue?

A

Muscle Tissue is attached to bone with Tendon

Epimysium covers Muscle
Many Fascicles inside

Perimysium covers each Fascicle
Many Muscle Fiber (cell) inside

Endomysium covers each Muscle Fiber
Somatic Motor Neuron
Blood Capillary

Sarcolemma covers each Muscle Fiber deep to Endomysium
Sarcoplasmic Reticulum made of Triad
Triad: 1 Transverse Tubule and 2 Terminal Cisternae
Sarcoplasm
Nuclei
Mitochondria
Many Myofibrils
Striations on Myofibrils

Sarcomere: Segment of Myofibril starting and ending with Z Disc
Filaments make up the Myofibrils
Thick Filaments: Myosin (not touching Z Discs)
Thin Filaments: Actin (Touching each Z Disc but not in middle)

Each Myofibril is connected to Dystrophin on each end
Dystrophin is connected to Membrane Protein

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11
Q

What is the Arrangement of a Sarcomere?

A

Sarcomere:
Segment between 2 Z Discs

I Band:
2 I Bands, one on each end of Sarcomere
Between 2 Myosin Filaments
Z disc at center of I Band
Contains parts of Actin Filaments from 2 different Sarcomeres

M Line:
Central line across Sarcomere

A Band:
Length of Myosin Filament of 1 Sarcomere

H Zone:
Length of Myosin Filament of 1 Sarcomere without overlap with Actin
M Line at the center of H Zone

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12
Q

What are the Components of a Sarcomere?

A

2 Z Discs
A Band
2 I Bands
H Zone
M Line

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13
Q

What is the Z Disc?

A

Narrow, plate-shaped region of dense material that separate one Sarcomere from the next

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14
Q

What is the A Band?

A

Dark, middle part of Sarcomere that extends entire length of Thick Filament (Myosin) and includes those parts of Thin Filaments (Actin) that overlap Thick Filament (Myosin)

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15
Q

What is the I Band?

A

Lighter, less dense area of Sarcomere that contains remainder of Thin Filaments (Actin) but no Thick Filaments (Myosin)

A Z Disc passes through center of each I Band

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16
Q

What is the H Zone?

A

Narrow region in center of each A Band that contains Thick Filaments (Myosin) but not Thin Filaments (Actin)

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17
Q

What is the M Line?

A

Region in center of H Zone that contains proteins that hold Thick Filaments (Myosin) together at center of Sarcomere

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18
Q

What are the Muscle Proteins?

A

1- Contractile Proteins:
Myosin
Actin

2- Regulatory Proteins:
Troponin
Tropomyosin

3- Structural Proteins:
Titin
Nebulin
Alpha-Actin
Myomesin
Dystrophin

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19
Q

What is a Contractile Protein?

A

Protein that generate force during muscle contraction

(Myosin and Actin)

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20
Q

What is Myosin?

A

Contractile protein that makes up Thick Filament

Molecule consists of a tail and 2 Myosin heads which bind to Myosin-Binding Sites on Actin molecules of Thin Filament during muscle contraction

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21
Q

What is Actin?

A

Contractile protein that is the main component of Thin Filament

Each Actin molecule has a Myosin-Binding Site where the Myosin head of Thick Filament binds during muscle contraction

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22
Q

What is a Regulatory Protein?

A

Protein that help switch muscle contraction process on and off

(Tropomyosin, and Troponin)

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23
Q

What is Tropomyosin?

A

Regulatory protein that is a component of Thin Filament

When skeletal muscle fiber is relaxed, Tropomyosin covers Myosin Binding Sites on Actin molecules, thereby preventing Myosin from binding to Actin

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24
Q

What is Troponin?

A

Regulatory protein that is a component of Thin Filament

When Ca2+ bind to Troponin, it changes shape
This conformational change moves Tropomyosin away from Myosin-Binding Sites on Actin, and muscle contractions subsequently begins as Myosin binds to Actin

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25
Q

What is a Structural Protein?

A

Protein that keep Thick and Thin Filaments of Myofibrils in proper alignment
Give Myofibrils elasticity and extensibility
Link Myofibrils to Sarcolemma and Extracellular Matrix

(Titin, Alpha-Actinin, Myomesin, Nebulin, and Dystrophin)

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26
Q

What is Titin?

A

Structural protein that connects Z Disc to M Line of Sarcomere, thereby helping to stabilize Thick Filament position

Can stretch and then spring back unharmed
Accounts for much of the elasticity and extensibility of Myofibrils

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27
Q

What is Alpha-Actinin?

A

Structural protein of Z Discs that attaches to Actin molecules of Thin Filaments and to Titin molecules

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28
Q

What is Myomesin?

A

Structural protein that forms M Line of Sarcomere

Binds to Titin molecules
Connects adjacent Thick Filaments to one another

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29
Q

What is Nebulin?

A

Structural protein that wraps around entire length of each Thin Filament

Helps anchor Thin Filaments to Z Discs
Helps regulate length of Thin Filaments during development

30
Q

What is Dystrophin?

A

Structural protein that links Thin Filaments of Sarcomere to integral membrane proteins in Sarcolemma, which are in turn attached to proteins in connective tissue matrix that surrounds muscle fibers

Thought to help reinforce Sarcolemma and help transmit tension generated by Sarcomeres to Tendons

31
Q

What is Skeletal Muscle?

A

Organ made up of Fascicles that contain Muscle Fibers (Cells), blood vessels, and nerves

Wrapped in Epimysium

32
Q

What is Fascicle?

A

Bundle of Muscle Fibers wrapped in Perimysium

33
Q

What is Muscle Fiber (Cell)?

A

Long cylindrical cell covered by Endomysium and Sarcolemma

Contains:
Sarcoplasm
Myofibrils
Many peripherally located Nuclei
Mitochondria
Transverse Tubules
Sarcoplasmic Reticulum
Terminal Cisternae

The Fiber has a striated appearance

34
Q

What is Myofibril?

A

Threadlike contractile elements within Sarcoplasm of muscle that extend the entire length of the fiber

Composed of Filaments

35
Q

What is Filaments (Myofilaments)?

A

Contractile proteins within Myofibrils that are of 2 types

Thick Filament composed of Myosin

Thin Filament composed of Actin, Tropomyosin, and Troponin

Sliding of Thin Filaments past Thick Filaments produces muscle shortening

36
Q

What is the Sliding Filament Mechanism?

A

Myosin pulls on Actin
Causing Thin Filament to slide inwards

Consequently, Z Discs move toward each other and Sarcomere shortens

Thanks to structural proteins, there is a transmission of force throughout the entire muscle, resulting in whole muscle contraction

37
Q

Relaxed vs Partially Contracted vs Maximally Contracted Muscles?

A

Relaxed Muscle:
Normal Sarcomere

Partially Contracted Muscle:
H Zone shorter
I Band shorter

Maximally Contracted Muscle:
No H Zone visible
No I Band visible

38
Q

What is the Contraction Cycle?

A

1- Myosin head hydrolyzes ATP and becomes energized and oriented

2- Myosin head binds to Actin, forming a cross-bridge

(Phosphate group leaves)

3- Myosin head pivots, pulling the Thin Filament past the Thick Filament towards the center of the Sarcomere (power stroke)

(ADP leaves, ATP comes in)

4- As Myosin head binds ATP, the cross-bridge detaches from Actin

39
Q

What is the Excitation-Contraction Coupling?

A

Concept that connects the events of a muscle action potential with the sliding filament mechanism

At Relaxation:
Voltage-gated Ca2+ channels closed, Ca2+ remains inside Terminal Cisternae of Sarcoplasmic Reticulum
Troponin holds Tropomyosin in position to block Myosin-Binding Sites on Actin

At Contraction:
Voltage-gated Ca2+ channels open, releasing Ca2+ from Terminal Cisternae of Sarcoplasmic Reticulum into the Sarcoplasm
Ca2+ binds to Troponin, which in turn undergoes a conformational change that moves Tropomyosin away from the Myosin-Binding Sites on Actin
Therefore, Myosin heads bind to Actin and pull it, resulting in contractions

40
Q

What is the Length-Tension Relationship?

A

The force of a muscle contraction depends on the length of the Sarcomeres in a muscle prior to contraction

41
Q

What are the Events at the Neuromuscular Junction (NMJ)?

A

The events at the NMJ produce a muscle action potential

Voltage-gated Ca2+ channels in a Neuron’s Synaptic End Bulb open
Resulting in an influx of Ca2+
This causes exocytosis of a Neurotransmitter (Acetylcholine - ACh) into the Synaptic Cleft

NT binds to Ligand-gated Na+ channels on the Motor Endplate
Causes an influx of Na+ into the muscle

This depolarizes the muscle and results in Ca2+ release from Sarcoplasmic Reticulum

NT gets broken down by Acetylcholinesterase, or back to neuron by cellular reuptake, or diffuse back

42
Q

What is the Summary of Contraction and Relaxation in Skeletal Muscle?

A

1- A nerve action potential in a Somatic Motor Neuron triggers the release of Acetylcholine (ACh)

2- ACh binds to receptors in the Motor End Plate, ultimately triggering a muscle action potential

3- Acetylcholinesterase destroys ACh so another muscle action potential does not arise unless more ACh is released from the Somatic Motor Neuron

4- A muscle action potential traveling along a Transverse Tubule triggers a change in the Voltage-gated Ca2+ channels that causes the Ca2+ release channels to open, allowing the release of Ca2+ into the Sarcoplasm

5- Ca2+ binds to Troponin on the Thin Filament, exposing the Myosin-Binding Sites on Actin

6- Contraction:
Myosin heads bind to Actin, undergo power strokes, and release
Thin Filaments are pulled towards center of Sarcomere

7- Ca2+ release channels close and Ca2+-ATPase Pumps use ATP to restore low level of Ca2+ in the Sarcoplasm

8- Tropomyosin slides back into position where it blocks the Myosin-Binding Sites on Actin

9- Muscle relaxes

43
Q

What is Muscle Metabolism?

A

Muscles derive the ATP necessary to power the contraction cycle from:

Creatine Phosphate
Anaerobic Glycolysis
Cellular Respiration

44
Q

What is Creatine Phosphate do for Muscle energy?

A

Creatine Kinase catalyzes the transfer of a phosphate group from Creatine Phosphate to ADP to rapidly yield ATP

Duration of energy: 15 seconds

45
Q

What is Anaerobic Glycolysis?

A

When Creatine Phosphate stores are depleted, glucose is converted into Pyruvic Acid to generate ATP

Lactic Acid goes into blood

Duration of energy: 2 minutes

46
Q

What is Cellular Respiration?

A

Under aerobic conditions, Pyruvic Acid can enter the Mitochondria and undergo a series of oxygen-requiring reactions to generate large amounts of ATP

Amino Acids from protein breakdown, Fatty Acids liberated from adipose cells, Pyruvic Acid from Glycolysis, and oxygen from hemoglobin in blood or from Myoglobin in muscle fibers go into Krebs Cycle and Electron Transport Chain in Mitochondrion

Make 30-32 ATP (and heat, CO2, and H2O)

Duration of energy: Several minutes to hours

47
Q

What is Muscle Fatigue?

A

Muscle fatigue is the inability to maintain force of contraction after prolonged activity

Due to:
Inadequate release of Ca2+ from Sarcoplasmic Reticulum
Depletion of Creatine Phosphate, oxygen, and nutrients
Build up of Lactic Acid and ADP
Insufficient release of ACh at NMJ

48
Q

What is Central Fatigue?

A

Central Fatigue occurs due to changes in the CNS and generally results in cessation of exercise

49
Q

Why increased Oxygen Consumption after exercise?

A

Breath heavily after exercise to get extra oxygen
Extra oxygen goes toward:

1- Replenishing Creatine Phosphate
2- Converting Lactate into Pyruvate
(since Lactic Acid was accumulated, Pyruvate goes to Krebs Cycle in Mitochondria to make ATP)
3- Reloading oxygen onto Myoglobin

50
Q

How is Muscle Tension controlled?

A

The strength of a muscle contraction depends on how many Motor Units are activated

A motor Unit consists of a Somatic Motor Neuron and the Muscle Fibers it innervates

Activating only a few Motor Units will generally result in a weak muscle contraction

Activating many Motor Units will generally result in a strong muscle contraction

51
Q

What is Motor Unit Recruitment?

A

Motor Unit Recruitment is the process in which the number of active Motor Units increases

Weakest Motor Units are recruited first, followed by stronger Motor Units

Motor Units contract alternately to sustain contractions for longer periods of time

52
Q

What is twitch Contraction?

A

Twitch Contraction is the brief contraction of all muscle fibers in a Motor Unit in response to a single action potential

1- Latent Period
2- Contraction Period
3- Relaxation Period
4- Refractory Period

53
Q

What is Frequency of Stimulation?

A

Wave summation occurs when the 2nd action potential triggers muscle contraction before the 1st contraction has finished

Results in a stronger contraction

Unfused Tetanus:
Back to back wave contractions, strong
Fused Tetanus:
All waves summed together for one strong contraction

54
Q

What is Muscle Tone?

A

Even when at rest, a skeletal muscle exhibits a small amount of tension called Tone (resistance to movement)

Tone is established by the alternating, involuntary activation of small groups of Motor Units in a muscle

55
Q

What is Isotonic Contractions?

A

Isotonic Contraction:
Tension is constant while muscle length changes
(Movement happening)

1- Concentric:
While picking up object

2- Eccentric:
While lowering object

56
Q

What is Isometric Contraction?

A

Isometric Contraction:
Muscle contracts but does not change length
(No movement happening)

ex- holding an object steady

57
Q

What are the 3 Types of Skeletal Muscle Fiber?

A

1- Slow Oxidative Fiber
2- Fast Glycolytic Fiber
3- Fast Oxidative-Glycolytic Fiber

58
Q

What are the Characteristics of Slow Oxidative Fiber?

A

Myoglobin Content:
Large amount

Mitochondria:
Many

Capillaries:
Many

Color:
Red

Method and capacity for generating ATP:
Aerobic Respiration
High

Rate of ATP hydrolysis by Myosin ATPase:
Slow

Contraction Velocity:
Slow

Fatigue Resistance:
High

Creatine Kinase:
Lowest amount

Glycogen Stores:
Low

Order of Recruitment:
First

Location where fibers are abundant:
Postural muscles such as neck

Primary Functions of fiber:
Maintain posture and aerobic endurance activities

59
Q

What are the Characteristics of Fast Oxidative-Glycolytic Fiber?

A

Myoglobin Content:
Large amount

Mitochondria:
Many

Capillaries:
Many

Color:
Red-pink

Method and capacity for generating ATP:
Aerobic Respiration and Anaerobic Glycolysis

Rate of ATP hydrolysis by Myosin ATPase:
Fast

Contraction Velocity:
Fast

Fatigue Resistance:
Intermediate

Creatine Kinase:
Intermediate amount

Glycogen Stores:
Intermediate

Order of Recruitment:
Second

Location where fibers are abundant:
Lower limb muscles

Primary Functions of fiber:
Walking, sprinting

60
Q

What are the Characteristics of Fast Glycolytic Fiber?

A

Myoglobin Content:
Small amount

Mitochondria:
Few

Capillaries:
Few

Color:
White (pale)

Method and capacity for generating ATP:
Anaerobic Glycolysis
Low

Rate of ATP hydrolysis by Myosin ATPase:
Fast

Contraction Velocity:
Fast

Fatigue Resistance:
Low

Creatine Kinase:
Highest amount

Glycogen Stores:
High

Order of Recruitment:
Third

Location where fibers are abundant:
Extraocular muscles

Primary Functions of fiber:
Rapid, intense movements of short duration

61
Q

What is Cardiac Muscle?

A

Cardiac Muscle has the same arrangements as skeletal muscle, but also has Intercalated Discs
Involuntary muscle

Nucleus
Striated
Intercalated Discs

Intercalated Discs:
Contain Desmosomes and Gap Junctions that allow muscle action potentials to spread from one muscle fiber to another

Cardiac muscle cells have more mitochondria and their contractions last 10 to 15 times longer than skeletal muscle contractions

62
Q

What is Smooth Muscle?

A

Smooth Muscle looks quite different than Cardiac and Skeletal muscle

It is thick in the middle, tapered on the ends, and not striated

Single-unit (Visceral) or Multi-unit fibers

Contractions start more slowly and last longer
Can shorten and stretch to a greater extent
Smooth Muscle fibers shorten in response to stretch

Has Dense Bodies connected by Intermediate Filaments

63
Q

What are the Characteristics of Skeletal Muscle?

A

Microscopic appearance and features:
Long cylindrical fiber with many peripherally located nuclei
Unbranched
Striated

Location:
Most commonly attached by tendons to bones

Fiber diameter:
Very large

Connective tissue components:
Endomysium
Perimysium
Epimysium

Fiber length:
Very large

Contractile proteins organized into sarcomeres:
Yes

Sarcoplasmic Reticulum:
Abundant

Transverse Tubules:
Yes
Aligned with each A Band junction

Junctions between fibers:
None

Autorhythmicity:
No

Source of Ca2+ for contraction:
Sarcoplasmic Reticulum

Regulator proteins for contractions:
Troponin
Tropomyosin

Speed of contraction:
Fast

Nervous control:
Voluntary (Somatic Nervous System)

Contraction regulation:
ACh released by somatic motor neurons

Capacity for regeneration:
Limited via Satellite cells

64
Q

What are the Characteristics of Cardiac Muscle?

A

Microscopic appearance and features:
Branched cylindrical fiber
One central nucleus
Intercalated Discs join neighboring fibers
Striated

Location:
Heart

Fiber diameter:
Large

Connective tissue components:
Endomysium
Perimysium

Fiber length:
Large

Contractile proteins organized into sarcomeres:
Yes

Sarcoplasmic Reticulum:
Some

Transverse Tubules:
Yes
Aligned with each Z Disc

Junctions between fibers:
Intercalated Discs contain Gap junctions and Desmosomes

Autorhythmicity:
Yes

Source of Ca2+ for contraction:
Sarcoplasmic Reticulum
Interstitial Fluid

Regulator proteins for contractions:
Troponin
Tropomyosin

Speed of contraction:
Moderate

Nervous control:
Involuntary (Autonomic Nervous System)

Contraction regulation:
ACh and Norepinephrine released by Autonomic Motor Neurons
Several hormones

Capacity for regeneration:
Limited under certain conditions

65
Q

What are the Characteristics of Smooth Muscle?

A

Microscopic appearance and features:
Fiber thick in middle
Fiber tapered at each end
One central Nucleus
No striations

Location:
Walls of hollow viscera
Airways (Trachea, Bronchi)
Blood vessels
Iris and Ciliary Body of Eye
Arrector Pili Muscles of hair follicles

Fiber diameter:
Small

Connective tissue components:
Endomysium

Fiber length:
Intermediate

Contractile proteins organized into sarcomeres:
No

Sarcoplasmic Reticulum:
Very little

Transverse Tubules:
No

Junctions between fibers:
Gap junctions in Visceral Smooth Muscle
None in Multi-unit Smooth Muscle

Autorhythmicity:
Yes
In Visceral smooth muscle

Source of Ca2+ for contraction:
Sarcoplasmic reticulum
Interstitial Fluid

Regulator proteins for contractions:
Calmodulin
Myosin Light Chain Kinase

Speed of contraction:
Slow

Nervous control:
Involuntary (Autonomic Nervous System)

Contraction regulation:
ACh and Norepinephrine released by Autonomic Motor Neurons
Several Hormones
Local chemical changes
Stretching

Capacity for regeneration:
Considerable (compared to other muscle, limited compared to epithelium)
Via Pericytes

66
Q

What is Muscle Tissue Regeneration?

A

Mature skeletal muscle fibers cannot undergo mitosis

Hypertrophy:
Increase in size

Hyperplasia:
Increased number of cells, over formation

Pericytes help contractions of smooth muscles

67
Q

How do Muscles Develop?

A

Most muscles are derived from the Mesoderm which develops into Somites:

Myotome
Dermatome
Sclerotome

68
Q

How does Aging affect Muscles?

A

Age 30-50:
About 10% of muscle tissue replaced by Fibrous Connective Tissue and Adipose tissue

Age 50-80:
Another 40% of muscle tissue is replaced

Results:
Muscle strength and flexibility decreases
Reflexes slow
Slow Oxidative Fibers numbers increase

69
Q

What is Deep Fascia?

A

External to Epimysium
Separates different muscles while binding them together

70
Q

What is Superficial Fascia?

A

Superficial to Deep Fascia
Separates Muscles from skin

Anatomy & Physiology Review I (30 decks)

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