Unit 7 Objectives 1. Describe the properties and functions of muscle tissue. (p. 178) 2. Describe...

Unit 7 Objectives

1. Describe the properties and functions of muscle tissue. (p. 178) 2. Describe the organization of muscle at the tissue level. (p. 178) 3. Identify the structural components of a sarcomere. (pp. 179–182) 4. Explain the key steps involved in the contraction of a skeletal muscle fiber. (pp. 182–184) 5. Compare the different types of muscle contractions. (pp. 187–189) 6. Describe the mechanisms by which muscles obtain and use energy to power contractions. (pp. 189–192) 7. Relate types of muscle fibers to muscular performance. (pp. 193–195) 8. Distinguish between aerobic and anaerobic endurance and explain their implications for muscular performance. (p. 192) 9. Contrast skeletal, cardiac, and smooth muscles in terms of structure and function. (pp. 194–195) 10. Identify the principal axial muscles of the body together with their origins and insertions. (pp. 199–204) 11. Identify the principal appendicular muscles of the body, together with their origins and insertions. (pp. 204–216) 12. Describe the effects of exercise and aging on muscle tissue. (p. 216)

Unit 7

1. Describe the properties and functions of muscle tissue. (p. 178)

Unit 7 1. Describe the properties and functions of muscle tissue. (p. 178)

• Produces movements such as walking, running, facial expressions, eye movements, and respiration. • Maintains posture, joint stability.• Supports, protect and encloses vital organs.• Helps to maintain body temperature by producing heat. • Guards the “gates” into and out of our bodies (ex. The iris of the eye).

The integrated action of joints, bones, nerves and skeletal muscles…

Unit 7

2. Describe the organization of muscle at the tissue level. (p. 178)

Muscle Organization II

Muscle Organization III

Muscle Organization I

Unit 7 2. Describe the organization of muscle at the tissue level. (p. 178)

Movement is attained due to a muscle moving an attached bone.

* Insertion

* Tendon

* Origin * Muscle Contracting

* DUH!

Unit 7 2. Describe the organization of muscle at the tissue level. (p. 178)

Gross Anatomy of Skeletal Muscle

* Bone * Perimysium * Blood Vesseles

*Tendon *Epimysium*Endomysium

*Fascicle

*Muscle Fiber

Unit 73. Identify the structural components of a

sarcomere. (pp. 179–182)

Unit 7 3. Identify the structural components of a sarcomere. (pp. 179–182)

* Nuclei

* Myofibril

* Sarcomere

} }* sarcolemma

Unit 7

Because a muscle fiber is not a single cell, its parts are often given special names such as:

• Sarcolemma for plasma membrane • Sarcoplasmic reticulum for endoplasmic reticulum • Sarcosome for mitochondrion • Sarcoplasm for cytoplasm

3. Identify the structural components of a sarcomere. (pp. 179–182)

Myonuclei identified along the length of an isolated muscle fiber.

* Myofibrils

* Transverse or T-Tube

* Sarcoplasmic reticulum

* Motor NeuronSkeletal Muscle

Contractile Unit

* Sarcomere* Z-Line

* Action Potential

* Myosin

* Actin

* Sarcomere

* Z-Line

Skeletal Muscle Contractile Unit

A single myofibril from a muscle fiber.

Skeletal Muscle Contractile Unit

* Actin

* Myosin

* Sarcomere

* Z-Line * I Band ~ Thin

* A Band ~ Thick

Skeletal Muscle Contractile Unit Terms

I-bands (isotropic) contain only thin myofilaments.

A-bands (anisotropic) contain both thin and thick myofilaments.

Z-line (German for Zwischenscheiben, meaning “between disks”)

M-line (German for Mitte, meaning “middle”)

iso- means equal , tropic- means turning

an- means without

Changes in Skeletal Muscle Contractile UnitBand/Line Contracted

MuscleStretched

Muscle

A-band No ChangeNo Change

I-band Shortens Lengthens

Z-lineMoves closer

togetherMoves further

Unit 7

Muscle Contraction Animation

Muscle Contraction Movie

Muscle Contraction Animation

4. Explain the key steps involved in the contraction of a skeletal muscle fiber. (pp. 182–184)

Cross Bridging Cycle

Overview

Contraction of skeletal muscle

Resistance

Unit 7 4. Explain the key steps involved in the contraction of a skeletal muscle fiber. (pp. 182–184)

Contraction

Tension

Quick Facts…

• Every skeletal muscle fiber is under the direct control by a neuron at a neural muscular junction.• When an action potential arrives at a neural

muscular junction and is transferred across the sarcolemma, the contraction process begins.• When an action potential reaches a muscle

fiber it will cause Ca+2 ions to seep out of the sarcoplasmic reticulum into the myofibrils starting contraction.

ACH Receptor Sites

Sarcolemma of Motor end plate

Synaptic TerminalMembrane

SynapticVesicle

Neural Control of Muscle Contraction

Step 1: Release of Acetylcholine (ACh)

SynapticVesicle

Step 2: Ach Binding at Motor End Plate

Sarcolemmamembrane becomes permeableto Na+

Step 3: Action Potential Conduction by Sarcolemma

Action Potential Propagation

AChE removing ACh in synaptic cleft

SynapseNeuromuscular Junction

Molecular Events of the Contraction Process

Myosin Fiber & Head

Actin subunits & fiber

TropomyosineTroponinActive Myosin-Actin Cross-bridge

Attachment site (in the absence

of Ca+2)

Inside a sacromere at

rest…

“Cocked” or Primed Myosin Head

Step 1: Active-site exposure

Tropomyosine slides off the

active site

Ca+2 binds to Troponin

Active Myosin-Actin Cross-bridge

Attachment site is uncovered

Ca+2 released from the Sacroplasmic Reticulum arrives at the sacromere.

Ca+2ADP

Attachment of myosin head to exposed active site on the thin filament of the

actin fiberCa+2

Step 2: Cross-bridge Attachment

Step 3: Pivoting of myosin head

Myosin headsreleases ADP

and P resulting in a “pivoting” of

the head toward the

center of the sacromere

The myosine head pivot

action thrusts the actin fiber

to the left contracting

the sacromere by a small

amount

Step 4: Cross-bridge deattachment

Myosin headsdeattachs from the

active site on the actin fiber when it binds with another

ATP can be supplied by aerobic or anaerobic cellular respiration or via CPATP cycle (page 190)

Step 5: Myosin reactivation

Myosin headsBecome

“cocked” or reactivated

again as they split ATP into

ADP and P and capture

the bond energy that is

released

The entire attachment –reattachment contraction cycle begins again until Ca+2 or ATP is removed.

Review: Sliding Filament Cross-Bridge Theory

Unit 7

5. Compare the different types of muscle contractions. (pp. 187–189)

Frequency of Muscle Fiber Stimulation Number of Muscle Fibers Involved Flavors of Contraction: Isotonic & Isometric Anti-Contraction : Muscle Elongation

Unit 7 5. Compare the different types of muscle contractions. (pp. 187–189)

Quick Facts…

• Muscles are composed of 1,000’s of fibers.• Individual muscle fibers either 100% contracted or are 100% at rest known as the “all-or-nothing” principle”• A “twitch” along a single muscle fiber is a

complete contraction cycle… at rest contraction at rest

• The “recruited” more motor units into a contraction cycle, increases“tension”.• Repeated stimulation before relaxation results in more “twitches”;summation.

Twitch: Development of Tension

Resting Phase

Latent Period

Contraction Phase

StimulusRelaxation Phase

Maximum tension development

Action Potential Sweeps Across the Sarcolemma.Cross-bridging begins between myosin and actin.Ca+2 levels drop and cross-bridging declines.

Frequency of Muscle Fiber Stimulation

Summation of twitches increases a muscle …

POWEROUTPUT!

Stimulation

Frequency of Muscle Fiber StimulationT

MaximumTension

A muscle producing maximum tension through repeated summation is said to reach a state called ….

Incomplete tetanus

MaximumTension

A muscle producing maximum tension through repeated summation while not allowing relaxation is said to reach a state called ….

Complete tetanus

Frequency of Muscle Fiber StimulationSR can’t reclaim Ca+2 fast enough for relaxation.

Low / Blue

Highest / Red

Medium / Green

Strong / Yellow

Skeletal Muscle Fascicle

Muscle Fibers / Cells

Motor Unit

Number of Muscle Fibers Involved

Threshold / Motor Unit

Quick Facts…• Muscles at rest maintain a “relaxed” tension created by various contracting motor units; this tension, called muscle tone helps maintain our posture.• If a muscle fiber is not stimulated on a regular basis is will atrophy, or become smaller and weaker.• Severe atrophy results in muscle fiber death. Dead fibers are not replaced.

Quick Facts…• Muscle contractions come in two flavors:

• Isotonic contraction … a contraction that results in the shortening of the entire

muscle as it maintains a constant tension before relaxing.

• Isometric contraction … caused by a increase of tension that does not result in the shortening of the muscle or the moving a joint or any other oject.

Iso- equal, tonic- tension

Iso- equal, metric- length

Anti-Contraction : Muscle Elongation• Muscle only actively contract ! • Muscles passively relax or elongate or…• Gravity can cause the mass of the contracted, shorten muscle to “drop” or elongate during its relaxation cycle…• The “memory” of elastic connective tissue

surround muscle fibers “uncoil” after a contraction…

• The contraction of an “opposing” muscle stretches out its relaxed antagonist.

Unit 7

6. Describe the mechanisms by which muscles obtain and use energy to power contractions. (pp. 189–192)

Unit 7 6. Describe the mechanisms by which muscles obtain and use energy to power contractions. (pp. 189–192)

• Muscle contractions require large amounts of energy (~6 x1014 ATP/sec/muscle fiber)

• Most of this energy is generated “on-demand”.• ATP is an energy-transfer molecule not an energy storage molecule.• Resting muscles (RM) transfer the energy stored in ATP to Creatine forming Creatine Phosphate (CP) and ADP. CP can then be used to convert ADP back into ATP “on demand”. • CP levels in RM’s are > ATP levels.

Quick Facts…

• Aerobic cellular respiration in mitochondria is used to recycle ADP + P + energy ATP during rest through moderate levels of

activity.• When muscular activity uses up the available

supplies of oxygen and or ATP and CP, available energy stored in the fiber’s glycogen deposits are converted through glycolysis to form ATP anaerobically.

Quick Facts…

ATP ~ Adenosine TriPhosphate

Adenine

Ribose

3 Phosphate Groups

Life’s “Rechargeable Battery”

ATP ~ Adenosine TriPhosphateUnstable

Life’s……………………“Rechargeable Battery”

“Releasing Energy” “Trapping Energy”

Creatine Phosphokinase

unstable…

Because large amounts of ATP in resting muscle cells are

…excess ATP transfers its third high energy ~P to a polypeptide called creatine forming creatine phosphate or CP.

ATP + Creatine ADP + Creatine Phosphate

ATP ~ Adenosine TriPhosphateUnit 7 6. Describe the mechanisms by which muscles obtain and use

energy to power contractions. (pp. 189–192)

Energyfrom Cellular Respiration

Energyfor Muscle Contraction

When Cellular ATP is High

Creatine

PO4Creatine

Phosphate

When Cellular ATP is Low

ATP Cycle ADP + CP ATP

C-C bond energy in organic molecules can be released and trapped in molecules of ATP

using the Krebs/ citric acid / tricarboxilic acid cycle; a slower but more efficient aerobic

process. Or…

Energy could be released and trapped in molecules of ATP using glycolysis; a quick

but less efficient anaerobic process

These processes prefer C-C bonds found in… 1st Carbohydrates > 2nd Lipids > 3rd Proteins

Quick Facts…

• Muscle fatigue can be caused by a prolonged oxygen debt, a by-product of glycolysis, called lactic acid, a decrease in the pH of the muscle fiber, or just a lack of ATP.

• A period of muscle recovery follows muscle fatigue, in which pre-fatigue conditions or pre-exertion level are re-established.

• Muscle recovery requires muscular, cardiovascular and hepatic systems to work together in order to reach homeostatic levels after heavy muscular exertion.

Unit 7

7. Relate types of muscle fibers to muscular performance. (pp.193–195)

8. Distinguish between aerobic and anaerobic endurance and explain their implications for muscular performance. (p.192)

Unit 7 8. Distinguish between aerobic and anaerobic endurance and explain their implications for muscular performance. (p. 192)

First some vocabulary…

Aerobic ~

Anaerobic ~

Any process that requires oxygen is said to be an aerobic process.

Any process that does not require oxygen is said to be an anaerobic process.

Like rusting, fire, or cellular respiration…

Like fermentation or glycolysis…

Some more vocabulary…

Endurance ~

Power ~

The ability to continue a given task.

The amount of work or energy expended in a given amount of time.

The amount of time an individual can perform a task.

The maximum amount of tension a muscle group can produce.

Unit 7 7. Relate types of muscle fibers to muscular performance. (pp. 193–195)

Two different types of muscle fiber can be found in most skeletal muscles.

Type I vs. Type II Fibers

Dark vs. White vs. Pink “flesh”“Chicken vs.“Chicken vs. “Human Thigh” Breast” muscle”The Type I and Type II fibers differ in

their…• Structure, • Biochemistry and• Performance

Type I vs. Type II Fibers

Type I(slow)

Type II a

(fast)Type II b

Type I, Red, or Aerobic Muscle Fibers … • Also known as "slow-twitch" fibers, take 3x longer to contract after stimulation,• Activated by small-diameter, thus slow-conducting, motor neurons, • Muscles containing many slow-twitch fibers have Egreater vascular support.• ERich in myoglobin and hence red in color, • Depend on cellular respiration for ATP production, contain Emany mitochondria,• EResistant to fatigue, and are dominant in muscles that are responsible for posture.

Type II, White, or Anaerobic Muscle Fibers…• PAlso known as "fast-twitch" fibers, • PTwice the diameter (more sacromeres) and

are more common then Type I fibers, • Activated by large-diameter, thus fast-conducting, motor neurons, • Low in myoglobin and rich in glycogen hence are whitish in color,• Depend on glycolysis for ATP production,

therefore they contain few mitochondria, • Fatigue easily, dominant in muscles used

for rapid and fine motor movements.

Most skeletal muscles contain some mixture of Type I and Type II fibers, but a single motor unit always contains one

fiber type or the other, never both.

Now we can consider how…Muscular Performance…

• The “muscle fiber” makeup of the muscle and…

A measure of how a muscle or muscle group responds to

perform a task of any intensity.

depends upon…

• The physical conditioning of the person!

Fast Fiber Conditioning

Improves a muscle or muscle groups ability to sustain a short -term high tension effort by…“Bulking-Up” or Increasing the number of myofibrils in fast-twitch fibers (increasing its diameter)

Increasing the standing supplies of glycogen/glucose (remembering that these fibers use glycolysis, an anaerobic reaction)

Slow Fiber Conditioning

Improves a muscle or muscle groups ability to sustain a long-term low tension effort by…“CardioVascular Training”… increasing the bodies ability to supply oxygen to the muscles by increasing lung capacity, RBC count & RBC hemoglobin content. (blood doping)

“Carbo-Loading”… preparing for and improving the bodies ability to elevate the blood glucose levels on demand (remember, these fibers use aerobic respiration).

Unit 7

9. Contrast skeletal, cardiac, and smooth muscles in terms of structure and function. (pp. 194–195)

Unit 7 9. Contrast skeletal, cardiac, and smooth muscles in terms of structure and function. (pp. 194–195)

Skeletal

•Moves bones

•Voluntary, capable of great work, but tires easily

Smooth

•Found around organs, such as the intestines and stomach

•Involuntary, capable of sustained work for very long periods of time

Cardiac: heart beat, capable of sustained work, mainly involuntary!

Muscle : Types

Skeletal

Cardiac

Smooth

Muscle Type: Location

Attached to bone

Heart Walls of hollow organs blood vessles and glands

Muscle Type: Cell Shape

Long, cylindrical

Branched Spindle- shaped

Muscle Type: Nucleus

Multiple, peripheral

Usually single, central

Single, central

Muscle Type: Special Features

Intercalated disks

Cell-to-cell attachments

Muscle Type: Striations

Yes NoYes

Muscle Type: Autorythmic

Yes, smooth sustained, & rythmic

Muscle Type: Control

Involuntary InvoluntaryVoluntary

Muscle Type: Function

Heart contraction to propel blood through the body

Compression of organs, ducts, glands, etc.

Move the whole body

• Smaller (than skeletal)•Have a single nucleus

• Less extensive T-tubule system• Myofilaments/fibrils organized as sarcomeres

Cardiac muscle fibers are…

Cardiac muscle fibers…

• Have extensive cell-to-cell connections at gap junctions that:

• Add strength (the intercalated disks)• Permits direct transmission of electrical signals from cell-to-cell (the gap junctions)• Provides its own intrinsic conduction system so that it does not rely upon a neural action potential to initiate contraction. • Rate and force of contraction is controlled by the autonomic nervous system however.

Autonomic nervous system: the part of the nervous system that supplies stimulation to the involuntary muscles, like the smooth and cardiac muscles, and to the glands, considered “visceral organs”.

Smooth muscle fibers …• Are smaller than skeletal and cardiac,• Occur in bundles/sheets of short fibers,

• Contraction are stimulated and controlled by the autonomic nervous system.• Do not end in tendons since they don’t attach or pull on bones!• Do not have troponin attached two the actin fibers• Have an extensive network of gap junctions between adjacent cells.

• Rather than organized arrays of thick and thin filaments, actin-based thin filaments and myosin-based thick filaments are dispersed throughout the cytoplasm in a seemingly random manner. • The thin filaments are attached to the plasma membrane and to cytoskeletal elements. • The thick filaments are distributed through the cytoplasm (like the plastic webbing in a bag used to package fruit and vegetables)

Smooth muscle fibers …

Unit 7

10. Identify the principal axial muscles of the body together with their origins and insertions. (pp. 199–204)

Unit 7 10. Identify the principal axial muscles of the body together with their origins and insertions. (pp. 199–204)

Origins & Insertions

• Pretend you were a puppet • Imagine strings attached to your body at the origins and insertions of skeletal muscles.• Pick a muscle and touch these locations and in you imagination “string” that part of your puppet” (you)• What would happen if you pulled the string from the “origin’s” end?

Origins & Insertions

HINT: The largest part of the muscles mass is closer to the origin of the muscle

*Sternocleidomastoid

*Infraspinatus

*Teres major

*Teres minor

*Latissimus dorsi

*Deltoid

*TrapeziusPosterior, Dorsal View

*Orbicularis oris*Masseter

*External oblique

*Rectus abdominis

*Serratus anterior

*Pectoralis major*Trapezius

*Sternocleidomastoid

*Deltoid

Anterior, Ventral View

Unit 7

11. Identify the principal appendicular muscles of the body, together with their origins and insertions. (pp. 204–216)

Unit 7 11. Identify the principal appendicular muscles of the body, together with their origins and insertions. (pp. 204–216)

*Fibularis* Soleus

*Gracilis

*Sartorius

*Rectus femoralis

*Gastronemius

*Vastus medialis

*Vastus lateralis Anterior, Ventral View

*Abductor magnus

*Biceps femoris

*Gluteus maximus

*Gastronemius * Soleus

*Gracilis

*Gluteus medius

*SartoriusPosterior, Dorsal View

* Soleus

*Gastronemius

* Fibularis muscle(s)

* Tibialis anterior

* Extensor digitorum

Laterial View

*Brachioradius

*Flexor carpi ulnaris *Biceps brachii

Anterior View

*Extensor carpi radialus *Flexor

carpi ulnaris

*Brachioradius

*Triceps brachii

*Extensor digitorum

*Extensor carpi ulnaris

Posterior View

Unit 7

12. Describe the effects of exercise and aging on muscle tissue. (p. 216)

Unit 7 12. Describe the effects of exercise and aging on muscle tissue. (p. 216)

Unit 7

Unit 7 Objectives 1. Describe the properties and functions of muscle tissue. (p. 178) 2. Describe...

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