Muscular SystemMuscular System

Honors Anatomy & Honors Anatomy & PhysiologyPhysiology

Skeletal, Smooth, or Cardiac?Skeletal, Smooth, or Cardiac?SKELETALSKELETAL

StriatedVoluntaryMultinucleatedBound to bones to move skeleton

SMOOTHSMOOTHNot striatedInvoluntarySingle nucleusIn hollow organs like stomachMoves food

CARDIACCARDIACStriatedInvoluntary Single nucleusHeart muscleMoves blood

• The remainder of the chapter will focus on SKELETAL MUSCLE

• Smooth/Visceral muscle will be covered in the DIGESTIVE system

• Cardiac muscle will be covered in the CARDIOVASCULAR system.

Introduction Introduction Muscles are organs made of Muscles are organs made of

specialized cells that use specialized cells that use nutrients for energy to contract.nutrients for energy to contract.

Skeletal Muscle action provide:Skeletal Muscle action provide: Movement of skeletonMovement of skeleton Muscle tone and postureMuscle tone and posture Stabilizes jointsStabilizes joints Generate body heatGenerate body heat Protect abdominal organsProtect abdominal organs

Muscle cell vs. Muscle fiberMuscle cell vs. Muscle fiber

Typical body cells are round with a Typical body cells are round with a single, central nucleus.single, central nucleus.

Muscle cells/FIBERS are elongated Muscle cells/FIBERS are elongated often with several nuclei pushed to often with several nuclei pushed to the outside of the cytoplasm.the outside of the cytoplasm.

Skeletal Muscle StructureSkeletal Muscle Structure Composed of several tissue types:Composed of several tissue types:

Skeletal muscle tissueSkeletal muscle tissue Nervous tissueNervous tissue BloodBlood Connective tissueConnective tissue

Attached to bone through a tendon.Attached to bone through a tendon. Attached to other muscles or organsAttached to other muscles or organs through a sheet-like tendon called anthrough a sheet-like tendon called an aponeurosisaponeurosis..

Connective TissueConnective Tissue Used to separate individual skeletal Used to separate individual skeletal

muscles and hold in position.muscles and hold in position. Insulates and bundles individual Insulates and bundles individual

skeletal muscle cells, aka muscle skeletal muscle cells, aka muscle fibers.fibers.

Allows for blood vessels and nerves to Allows for blood vessels and nerves to pass into the muscle fiber.pass into the muscle fiber.

Allows different parts of the muscle toAllows different parts of the muscle to move independently.move independently.

Structure of a Skeletal MuscleStructure of a Skeletal Muscle

Sarcolemma

Skeletal Muscle FiberSkeletal Muscle Fiber An individual muscle cell.An individual muscle cell. Contracts in response to stimulation.Contracts in response to stimulation. Composed of:Composed of:

Cell membrane = sarcolemmaCell membrane = sarcolemma Cytoplasm = sarcoplasmCytoplasm = sarcoplasm Several small nucleiSeveral small nuclei Mitochondria = possibly HUNDREDS Mitochondria = possibly HUNDREDS

depending on demand placed on the depending on demand placed on the muscle.muscle.

Myofilaments that allow for contractionMyofilaments that allow for contraction

Make a muscle cell and Make a muscle cell and organize into muscle organize into muscle

bundlebundle

Functional Unit of Muscle = Functional Unit of Muscle = SarcomereSarcomere

Actin – THIN myofilamentActin – THIN myofilament Myosin – THICK Myosin – THICK

myofilamentmyofilament It is the overlapping It is the overlapping

nature of the ACTIN and nature of the ACTIN and Myosin and the Myosin and the connection made connection made between them that allows between them that allows muscles to contract.muscles to contract.

Skeletal Muscle Skeletal Muscle ActivityActivity

FUNCTIONAL PROPERTIES

Excitability – can receive – can receive message from the brain.message from the brain.Contractility – can – can contract.contract.Extensibility – can – can stretch through use of stretch through use of connective tissues like connective tissues like tendons.tendons.Elasticity – can return to – can return to original position following original position following contraction.contraction.

How do Muscles How do Muscles KNOW to KNOW to Contract?Contract?

A motor neuron A motor neuron communicates the communicates the signal to move from the signal to move from the brain to the muscle.brain to the muscle. A motor neuron is an A motor neuron is an

EFFERENT neuron.EFFERENT neuron.

The connection The connection between a motor between a motor neuron and a muscle neuron and a muscle fiber is called the fiber is called the NEUROMUSCULAR NEUROMUSCULAR JUNCTION.JUNCTION.

What do muscles NEED to contract?What do muscles NEED to contract? Blood supply containing:Blood supply containing:

OxygenOxygen GlucoseGlucose WaterWater Electrolytes Electrolytes

Innervation: informationInnervation: information Brain – spinal cord – spinal nerve – nerveBrain – spinal cord – spinal nerve – nerve Neuromuscular junction and Neuromuscular junction and

neurotransmitter neurotransmitter

How do Muscles Contract?How do Muscles Contract?Sliding Filament TheorySliding Filament Theory

Mitochondria convert carbohydrates and Mitochondria convert carbohydrates and oxygen to ATP.oxygen to ATP.

ATP is the energy muscles use to contract.ATP is the energy muscles use to contract. With this energy, the myofilaments ACTIN and With this energy, the myofilaments ACTIN and

MYOSIN inside the muscle fiber MYOSIN inside the muscle fiber slide across slide across one another.one another.

This causes the muscle to CONTRACT This causes the muscle to CONTRACT (shorten) and RELAX (lengthen).(shorten) and RELAX (lengthen).