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Physiology of Muscles PHYSIOLOGY I (PHL 215) Dr. Gamal Gabr
22

Muscular System Functions Body movement (Locomotion) Maintenance of posture Respiration * Diaphragm and intercostals contractions Communication.

Dec 16, 2015

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Page 1: Muscular System Functions  Body movement (Locomotion)  Maintenance of posture  Respiration * Diaphragm and intercostals contractions  Communication.

Physiology of Muscles

PHYSIOLOGY I (PHL 215)

Dr. Gamal Gabr

Page 2: Muscular System Functions  Body movement (Locomotion)  Maintenance of posture  Respiration * Diaphragm and intercostals contractions  Communication.

Muscular System Functions

Body movement (Locomotion) Maintenance of posture Respiration

*Diaphragm and intercostals contractions Communication (Verbal and Facial) Constriction of organs and vessels Heart beat Production of body heat (Thermogenesis)

Page 3: Muscular System Functions  Body movement (Locomotion)  Maintenance of posture  Respiration * Diaphragm and intercostals contractions  Communication.

Typical cells Muscle cell=fiber

Plasma membrane Sarcolemma

Cytoplasm Sarcoplasm

Endoplasmic reticulum

Sarcoplasmic reticulum (SR)

Many mitochondria

Multiple nuclei

Page 4: Muscular System Functions  Body movement (Locomotion)  Maintenance of posture  Respiration * Diaphragm and intercostals contractions  Communication.

Muscle cell structures not found in other cells

Myofibrils: bundles of very fine fibers Thick and thin myofilaments: very fine fibers that make

up myofibrils Sarcomere: segment of myofibril between two Z lines;

contractile unit T tubules: transmit electrical impulses through cell

Page 5: Muscular System Functions  Body movement (Locomotion)  Maintenance of posture  Respiration * Diaphragm and intercostals contractions  Communication.
Page 6: Muscular System Functions  Body movement (Locomotion)  Maintenance of posture  Respiration * Diaphragm and intercostals contractions  Communication.

Myofilaments

4 protein molecules that make up myofilaments: Myosin, actin, tropomyosin, troponin

Thin filaments: actin, tropomyosin, troponin

Thick filaments: mostly myosin

Page 7: Muscular System Functions  Body movement (Locomotion)  Maintenance of posture  Respiration * Diaphragm and intercostals contractions  Communication.

Properties of Muscle

Excitability: Capacity of muscle to respond to a stimulus

Contractility: Ability of a muscle to shorten and generate pulling force

Extensibility: Ability stretches when pulled

Elasticity: Ability to return to original shape and length after contraction or extension

Page 8: Muscular System Functions  Body movement (Locomotion)  Maintenance of posture  Respiration * Diaphragm and intercostals contractions  Communication.

Muscle structure

Connective Tissue Sheaths

Connective Tissue (CT) of a Muscle

Epimysium: Dense regular CT surrounding entire muscle

*Separates muscle from surrounding tissues and organs

Perimysium: Collagen and elastic fibers surrounding a group of muscle fibers called a fascicle

*Contains blood vessels and nerves

Endomysium: Loose CT that surrounds individual muscle fibers

*Also contains blood vessels and nerves

*Collagen fibers of all 3 layers come together at each end of muscle to form a tendon or aponeurosis.

Page 9: Muscular System Functions  Body movement (Locomotion)  Maintenance of posture  Respiration * Diaphragm and intercostals contractions  Communication.
Page 10: Muscular System Functions  Body movement (Locomotion)  Maintenance of posture  Respiration * Diaphragm and intercostals contractions  Communication.

Motor neurons

*Stimulate muscle fibers to contract

*Neuron axons branch so that each muscle fiber (muscle cell) is innervated

*Form a neuromuscular junction

Capillary beds surround muscle fibers

*Muscles require large amount of energy

*Extensive vascular network delivers necessary oxygen and nutrients and carries away metabolic waste produced by muscle fibers

Page 11: Muscular System Functions  Body movement (Locomotion)  Maintenance of posture  Respiration * Diaphragm and intercostals contractions  Communication.

Energy for Muscle Contractions

*ATP: adenosine triphosphate

*CP: creatine phosphate

Glucose & Oxygen

*Glucose stored in form of glycogen in muscle

*Excess oxygen molecules in sarcoplasm bound to myoglobin

Page 12: Muscular System Functions  Body movement (Locomotion)  Maintenance of posture  Respiration * Diaphragm and intercostals contractions  Communication.

Anaerobic respiration

Allows body to avoid use of oxygen in short termProduces lactic acidAccumulation of lactic acid in muscles causes burning sensation

Page 13: Muscular System Functions  Body movement (Locomotion)  Maintenance of posture  Respiration * Diaphragm and intercostals contractions  Communication.

Types of MuscleSkeletal

*Attached to bones

*Makes up 40% of body weight (Women’s skeletal muscle makes up 36% of their body mass, Men’s skeletal muscle makes up 42% of their body mass)

*Responsible for locomotion, facial expressions, posture, respiratory movements, other types of body movement

*Voluntary in action; controlled by somatic motor neurons

Smooth

*In the walls of hollow organs, blood vessels, eye, glands, uterus, skin

*Functions: propel urine, mix food in digestive tract, regulating blood flow

*Controlled involuntarily by endocrine and autonomic nervous systems

Cardiac

*Heart: major source of movement of blood

Page 14: Muscular System Functions  Body movement (Locomotion)  Maintenance of posture  Respiration * Diaphragm and intercostals contractions  Communication.

Basic Features of a Skeletal Muscle

Muscle attachments*Most skeletal muscles run from one bone to another

*One bone will move – other bone remains fixed

*Origin – less movable attachment

*Insertion – more movable attachment

*Muscles attach to origins and insertions by connective tissue

Fleshy attachments – connective tissue fibers are short

Indirect attachments – connective tissue forms a tendon

Page 15: Muscular System Functions  Body movement (Locomotion)  Maintenance of posture  Respiration * Diaphragm and intercostals contractions  Communication.

Skeletal Muscle Structure

*Composed of muscle cells (fibers), connective tissue, blood vessels, nerves

*Fibers are long, cylindrical, and multinucleated

*Tend to be smaller diameter in small muscles and larger in large muscles. 1 mm - 4 cm in length

*Striated appearance

*Nuclei are peripherally located

Page 16: Muscular System Functions  Body movement (Locomotion)  Maintenance of posture  Respiration * Diaphragm and intercostals contractions  Communication.

Muscle Fiber Anatomy

Sarcolemma - cell membrane

* Surrounds the Sarcoplasm (cytoplasm of fiber)

* Punctuated by openings called the transverse tubules (T-tubules)

Myofibrils -cylindrical structures within muscle fiber

* Are bundles of protein filaments (=myofilaments)

* Two types of myofilaments

1. Actin filaments (thin filaments)

2.Myosin filaments (thick filaments)

– When myofibril shortens, muscle shortens (contracts)

Page 17: Muscular System Functions  Body movement (Locomotion)  Maintenance of posture  Respiration * Diaphragm and intercostals contractions  Communication.

Sarcoplasmic Reticulum (SR)

SR is an elaborate, smooth endoplasmic reticulum Runs longitudinally and surrounds each myofibrilSR stores Ca++ when muscle not contractingWhen stimulated, calcium released into sarcoplasm SR membrane has Ca++ pumps that function to pump Ca++ out of the sarcoplasm back into the SR after contraction

Page 18: Muscular System Functions  Body movement (Locomotion)  Maintenance of posture  Respiration * Diaphragm and intercostals contractions  Communication.

Smooth Muscle

*Cells are not striated

*Fibers smaller than those in skeletal muscle

*Spindle-shaped; single, central nucleus

*More actin than myosin

*No sarcomeres

*Not arranged as symmetrically as in skeletal muscle, thus no striations.

Page 19: Muscular System Functions  Body movement (Locomotion)  Maintenance of posture  Respiration * Diaphragm and intercostals contractions  Communication.

Smooth Muscle

• Grouped into sheets in walls of hollow organs• Longitudinal layer: muscle fibers run parallel to organ’s long

axis• Circular layer: muscle fibers run around circumference of the

organ• Both layers participate in peristalsis

Page 20: Muscular System Functions  Body movement (Locomotion)  Maintenance of posture  Respiration * Diaphragm and intercostals contractions  Communication.

Cardiac Muscle Found only in heart where it forms a thick layer called the

myocardium

Striated fibers that branch

Each cell usually has one centrally-located nucleus

Fibers joined by intercalated disks

Page 21: Muscular System Functions  Body movement (Locomotion)  Maintenance of posture  Respiration * Diaphragm and intercostals contractions  Communication.

Disorders of Muscle Tissue

*Muscle Fatigue

*Lack of oxygen causes ATP deficit

*Lactic acid builds up from anaerobic respiration

*Muscle Atrophy

*a decrease in the mass of the muscle

*Weakening and shrinking of a muscle

*May be caused

*Immobilization

*Loss of neural stimulation

Page 22: Muscular System Functions  Body movement (Locomotion)  Maintenance of posture  Respiration * Diaphragm and intercostals contractions  Communication.

Disorders of Muscle Tissue

*Muscle Hypertrophy

*Enlargement of a muscle

*More capillaries

*More mitochondria

*Caused by*Strenuous exercise

*Steroid hormones

*Muscle Tonus

*Tightness of a muscle

*Some fibers always contracted