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MUSCLES . Form is For Function. We See This in bones when we look at a vertebrae Processes are for attachment of muscles, tendons and ligaments. Openings such as foramen are for nerves and blood vessels. .

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form is for function
Form is For Function
  • We See This in bones when we look at a vertebrae
  • Processes are for attachment of muscles, tendons and ligaments.
  • Openings such as foramen are for nerves and blood vessels.
smooth muscle characteristics
Smooth Muscle Characteristics
  • Has no striations
  • Spindle-shaped cells
  • Single nucleus
  • Involuntary – no conscious control
  • Found mainly in the walls of hollow organs

Figure 6.2a

skeletal muscle characteristics
Skeletal Muscle Characteristics
  • Most are attached by tendons to bones
  • Cells are multinucleate
  • Striated – have visible banding
  • Voluntary – subject to conscious control
  • Cells are surrounded and bundled by connective tissue
cardiac muscle characteristics
Cardiac Muscle Characteristics
  • Has striations
  • Usually has a single nucleus
  • Joined to another muscle cell at an intercalated disc
  • Involuntary
  • Found only in the heart

Figure 6.2b

characteristics of muscles
Characteristics of Muscles
  • Muscle cells are elongated (muscle cell = muscle fiber)
  • Contraction of muscles is due to the movement of microfilaments
  • All muscles share some terminology
    • Prefix myo refers to muscle
    • Prefix mys refers to muscle
    • Prefix sarco refers to flesh
skeletal muscle attachments
Skeletal Muscle Attachments
  • Epimysium blends into a connective tissue attachment
    • Tendon – cord-like structure
    • Aponeuroses – sheet-like structure
  • Sites of muscle attachment
    • Bones
    • Cartilages
    • Connective tissue coverings
connective tissue wrappings of skeletal muscle so as to keep muscle fibers together
Connective Tissue Wrappings of Skeletal Muscle (So as to keep Muscle fibers together)
  • Endomysium – around single muscle fiber
  • Perimysium – around a fascicle (bundle) of fibers
  • Epimysium- The outermost connective tissue

Figure 6.1

characteristics of muscles and myo mys and sarco
Characteristics of Muscles: AND….MYO, MYS and SARCO
  • Muscle cells are elongated (muscle cell = muscle fiber)
  • Contraction of muscles is due to the movement of microfilaments
  • All muscles share some terminology:
    • Prefix myo refers to muscle
    • Prefix mys refers to muscle
    • Prefix sarco refers to flesh
muscle cell muscle fiber myocyte but beware all muscles cells are not alike
The myocyte is elongated

Their characteristics depend on which type of muscle they are found: skeletal, muscle or cardiac.

Which Type of Muscle are we referring to here??

Muscle Cell =Muscle Fiber= Myocyte: But BEWARE…ALL Muscles cells are NOT ALIKE!!
microscopic anatomy of skeletal muscle cell a first look
Microscopic Anatomy of Skeletal Muscle Cell: A First Look
  • Cells are multinucleate
  • Nuclei are just beneath the sarcolemma

Figure 6.3a

smooth endoplasmic reticulum sr in muscle cells
Smooth Endoplasmic Reticulum (SR) in Muscle Cells
  • VERY SPECIALIZED
  • It STORES and MOBILIZES Calcium ions
  • What is the role of Ca++ in muscle contraction??
function of muscles
Function of Muscles
  • Produce movement
  • Maintain posture
  • Stabilize joints
  • Generate heat
properties of skeletal muscle activity
Properties of Skeletal Muscle Activity
  • Irritability – ability to receive and respond to a stimulus
  • Contractility – ability to shorten when an adequate stimulus is received
muscle contraction begins when
Muscle Contraction Begins When..
  • Stored Calcium is released into the sarcoplasm
  • These ions are released into the sarcomeres
relaxed and contracted sarcomeres
Relaxed and Contracted Sarcomeres
  • Muscle cells shorten because their individual sarcomeres shorten
    • pulling Z discs closer together
    • pulls on sarcolemma
  • Notice neither thick nor thin filaments change length during shortening
  • Their overlap changes as sarcomeres shorten
microscopic anatomy of skeletal muscle
Microscopic Anatomy of Skeletal Muscle

Sarcoplasmic reticulum – specialized endoplasmic reticulum

Figure 6.3a

microscopic anatomy of skeletal muscle28
Microscopic Anatomy of Skeletal Muscle
  • Myofibril
    • Bundles of myofilaments
    • Myofibrils are aligned to give distinct bands
      • I band =

light band

      • A band = dark band

Figure 6.3b

microscopic anatomy of skeletal muscle29
Microscopic Anatomy of Skeletal Muscle
  • Sarcomere
    • Contractile unit of a muscle

Figure 6.3b

microscopic anatomy of skeletal muscle30
Microscopic Anatomy of Skeletal Muscle
  • Organization of the sarcomere
    • Thick filaments = myosin filaments
      • Composed of the protein myosin
      • Has ATPase enzymes

Figure 6.3c

microscopic anatomy of skeletal muscle31
Microscopic Anatomy of Skeletal Muscle
  • Organization of the sarcomere
    • Thin filaments = actin filaments
      • Composed of the protein actin

Figure 6.3c

microscopic anatomy of skeletal muscle32
Microscopic Anatomy of Skeletal Muscle
  • Myosin filaments have heads (extensions, or cross bridges)
  • Myosin and actin overlap somewhat

Figure 6.3d

microscopic anatomy of skeletal muscle33
Microscopic Anatomy of Skeletal Muscle
  • At rest, there is a bare zone that lacks actin filaments
  • Sarcoplasmic reticulum (SR) – for storage of calcium

Figure 6.3d

neural stimulus to muscles
Neural Stimulus to Muscles
  • Skeletal muscles must be stimulated by a nerve to contract
  • Motor unit
    • One neuron
    • Muscle cells stimulated by that neuron

Figure 6.4a

those myofiloments how they move the basis of muscle contraction

Those Myofiloments: How They Move: The Basis of Muscle Contraction

Plus: The Neuromuscular Junction: where it all happens: This IS Muscle Physiology!

what do you think
What Do You Think?
  • Glycogen- Stored form of starch found in muscle
  • What is the role of Glycogen in muscle physiology?
the case of the shrinking sarcomere
SEE THE I BAND DISAPPEAR during a contraction of the.. sarcomere? Yes. Which makes up myofilament.

Will the I band reappear? When?

What causes the I band to dissapear?

The Case of the Shrinking Sarcomere
what is actually happening when a sacromere shrinks
What is ACTUALLY happening when a Sacromere Shrinks?
  • The thin filament ACTIN and the THICK filament MYOCIN form a CROSS-BRIDGE that cause a SLIDING motion.
  • This shortens the sacromere or closes that GAP or I band and causes a CONTRACTION.
  • Neither the ACTIN nor the Myocin filament actually shorten its the sacromere itself.
before contraction can happen
Before Contraction Can Happen
  • We must think about it …even if it is a reflex.
  • We must involve the CNS…
nerve stimulus to muscles
Nerve Stimulus to Muscles
  • Skeletal muscles must be stimulated by a nerve to contract
  • Motor unit
    • One neuron
    • Muscle cells stimulated by that neuron

Figure 6.4a

motor end plate
MOTOREND PLATE
  • This is where the neuron and myofiber intercept.
  • Muscle contraction is possible because of neural impulse at the motor end plate.
  • It is the action potential that causes the release of Ca++ ions from the SR,
  • The Ca++ can then bind to Troponin and change the configuration of Tropomyocin.
  • ACTiN’s G binding sites are then exposed.
nerve stimulus to muscles43
Nerve Stimulus to Muscles
  • Synaptic cleft – gap between nerve and muscle
    • Nerve and muscle do not make contact
    • Area between nerve and muscle is filled with interstitial fluid

Figure 6.5b

transmission of nerve impulse to muscle
Transmission of Nerve Impulse to Muscle
  • Neurotransmitter – chemical released by nerve upon arrival of nerve impulse
    • The neurotransmitter for skeletal muscle is acetylcholine
  • Neurotransmitter attaches to receptors on the sarcolemma
  • Sarcolemma becomes permeable to sodium (Na+)
transmission of nerve impulse to muscle45
Transmission of Nerve Impulse to Muscle
  • Sodium rushes into the cell generates an action potential (AP)
  • The action potential travels along the T-tubules to the SR to stimulate release of Calcium ions.
where do ca ions go
Where do Ca ions go?
  • The ions travels to the muscle tissue and bind to the ACTIN regulatory proteins ( TROPONIN) .
  • This UNCOVERS Myosin Head BINDING Sites on ACTIN so as to allow CROSS BRIDGING ( once myosin is powered by ATP.
the sliding filament theory of muscle contraction
The Sliding Filament Theory of Muscle Contraction
  • Activation by nerve causes myosin heads (crossbridges) to attach to binding sites on the thin filament
  • Myosin heads then bind to the next site of the thin filament

Figure 6.7

the sliding filament theory of muscle contraction49
The Sliding Filament Theory of Muscle Contraction
  • This continued action causes a sliding of the myosin along the actin
  • The result is that the muscle is shortened (contracted)

Figure 6.7

now the muscle must relax
NOW the muscle Must RELAX
  • Acetylcholine, the neurotransmitter is broken down by the enzyme acetylcholinesterase
  • SO the stimulus to muscle ceases!
  • Calcium ions are actively transported back to the SR
  • The actin and myocin cross bridges break
  • RELAXES------S T R E T C H of the sarcomere. Get it??
creatine phosphate
Creatine Phosphate
  • This a high energy molecule found in muscle cells
  • 4 to 6 time more abundant in muscle fibers than ATP!!
  • It CANNOT directly transfer a phosphate group to a reaction
  • INSTEAD, when ATP is sufficient an enzyme in mitochondrian, creatine phosphokinase promotes the synthesis of creatine phosphate.
  • As ATP gets degraded, creatine phosphate can donate its phosphate bonds to ADP creating NEW ATP
energy for muscle contraction
Energy for Muscle Contraction
  • Direct phosphorylation
    • Muscle cells contain creatine phosphate (CP)
      • CP is a high-energy molecule
    • After ATP is depleted, ADP is left
    • CP transfers energy to ADP, to regenerate ATP
    • CP supplies are exhausted in about 20 seconds

Figure 6.10a

energy for muscle contraction55
Energy for Muscle Contraction
  • Initially, muscles used stored ATP for energy
    • Bonds of ATP are broken to release energy
    • Only 4-6 seconds worth of ATP is stored by muscles
  • After this initial time, other pathways must be utilized to produce ATP
energy for muscle contraction56
Energy for Muscle Contraction
  • Aerobic Respiration
    • Series of metabolic pathways that occur in the mitochondria
    • Glucose is broken down to carbon dioxide and water, releasing energy
    • This is a slower reaction that requires continuous oxygen

Figure 6.10b

energy for muscle contraction57
Energy for Muscle Contraction
  • Anaerobic glycolysis
    • Reaction that breaks down glucose without oxygen
    • Glucose is broken down to pyruvic acid to produce some ATP
    • Pyruvic acid is converted to lactic acid

Figure 6.10c

myoglobin
Myoglobin
  • Myoglobin is oxygen carrier ( It is a pigment)
  • Synthesized in muscle
  • Higher affinity for oxygen than hemoglobin
  • One globin protein, rather than 4: therefore we say this protein has tertiary level structure as apposed to hemoglobin’s quartenary level structure.
  • It can STORE oxygen as well as carry it.
muscles and body movements
Muscles and Body Movements
  • Movement is attained due to a muscle moving an attached bone

Figure 6.12

energy for muscle contraction60
Energy for Muscle Contraction
  • Anaerobic glycolysis (continued)
    • This reaction is not as efficient, but is fast
      • Huge amounts of glucose are needed
      • Lactic acid produces muscle fatigue

Figure 6.10c

muscle fatigue and oxygen debt
Muscle Fatigue and Oxygen Debt
  • When a muscle is fatigued, it is unable to contract
  • The common reason for muscle fatigue is oxygen debt
    • Oxygen must be “repaid” to tissue to remove oxygen debt
    • Oxygen is required to get rid of accumulated lactic acid
  • Increasing acidity (from lactic acid) and lack of ATP causes the muscle to contract less
muscles and body movements63
Muscles and Body Movements
  • Muscles are attached to at least two points
    • Origin– attachment to a immoveable bone
    • Insertion – attachment to a movable bone
    • Action- What this muscle and bone (together) accomplish

Figure 6.12

example of how it works
Example of how it works:

Name of Muscle: Biceps Brachii

Origin:Scapula of Shoulder girdle

Insertion: Proximal Radius

Action: Flexes elbow and supinates ( to turn backward = supinate ) forearm

types of ordinary body movements
Types of Ordinary Body Movements
  • Flexion
  • Extension
  • Rotation
  • Abduction
  • Circumduction
body movements
Body Movements

Figure 6.13a–c

body movements67
Body Movements

Figure 6.13d

slide68

TYPES OF MUSCLES

:

Prime mover:

  • major muscle of movement

Antagonist:

opposes movement;when primeMover is active

, antagonist is stretched and relaxes

Synergists:

  • assist prime mover
  • fixator--stabilizers
fascicle arrangement
Fascicle Arrangement

All skeletal muscles have fascicles

Fascicle arrangement allows

different functions of muscles

  • circular (sphincter)—squeeze
  • convergent—fan, triangle
  • parallel (fusiform)--strap
  • pennate (feather)
slide71

Power and Range of Motion

Determined by fascicular arrangement

Skeletal muscle shortens to 70%

of resting length

  • parallel--shorter, not powerful
  • pennate--lots of fibers, powerful
pennate muscles
Pennate Muscles
  • Unipennate:
    • fibers on 1 side of tendon e.g., extensor digitorum
  • Bipennate:
    • fibers on both sides of tendon e.g., rectus femoris
    • tendon branches within muscle e.g., deltoid
  • Multipennate:
  • Form angle with tendon
  • Don’t move as far as parallel muscles
  • Contain more myofibrils than parallel muscles
  • Develop more tension than parallel muscles

Figure 11–1c, d, e

duchenne muscular dystrophy
Duchenne Muscular Dystrophy
  • Inherited muscle-destroying diseases affects muscle (MALES only)
  • Muscles atrophy- wheelchairs at a young age. Death from failure of respiratory muscles by young adulthood.
  • Due to lack of protein called dystropin-associated glycoprotein (DAG)that helps maintain sarcolemma. NO CURE YET.
myathenia gravis
Myathenia Gravis
  • The disease involves a SHORTAGE of

Acetylcholine receptors at the neuromuscular junction.

NT can’t bind and stimulate AP to muscle.

slide78
Patients of Myasthenia Gravis usually have drooping eyelids
  • Difficulty in swallowing and talking
  • Generalized muscle weakness and fatigability
  • Antibodies to acetylcholine receptors found in blood …suggests MG is autoimmune disease
  • Respiratory Failure due to muscle failure here--Death
botulism
Botulism
  • Bacterium, Clostridiumbotulinum, under anaerobic conditions, produces a toxin called botulinum.
  • It prevents release of Acetylcholine from nerves at NM junction.
  • Paralyzes muscles. Do you understand why?