Types of Muscle

• The human body is comprised of over 600 muscles• Muscle makes up 30-35% (in women) and 42-47% (in men) of body mass.

Three types of muscle:

Skeletal muscle

Smooth muscle

Cardiac muscle

Key TermsTendons - tough bands of connective tissue that join muscle to

boneAponeurosis – a sheet-like membrane that serves as a fascia to

bind muscles together or to connect muscle to bone

ex. Palmar aponeurosis

Fascia – connective tissue that covers, supports, and separates muscles

ex. Fascia lata (thigh), brachial fascia (upper arm)

Tissue - masses of cells that have similar function and formMuscle tissue - collection of cells that shorten during

contraction, therefore creating tension that results in movement

A. Skeletal (Striated) Muscle

Muscles that are attached to the bones via connective tissue tendons– During muscle contraction, skeletal muscle

shortens and moves various parts of the skeleton

– We have voluntary control of our muscles, meaning they are activated through signals carried to the them via nerves

– Referred to as striated, because their appearance is a series of alternating light and dark stripes (myofilaments)

– Repetitive contraction leads to fatigue

B. Smooth Muscle

Muscles surrounding your body’s internal organs, as well as your blood vessels, respiratory tract, iris (eye) & gastro-intestinal tract– The contractions are slow and uniform and can

remain for long periods of time

– Activation is involuntary

– Fatigue resistant

– Fibres are arranged in dense sheets, therefore appearing smooth

C. Cardiac Muscle

Muscles found only in the heart.– Functions to provide the contractile

activity of the heart (pumping blood to

the rest of the body)

– Is very fatigue resistant

– Activation of cardiac muscle is

involuntary

– Striated

a) Muscle b) Fascicle c) Muscle fiber d) Myofibril

Components of skeletal muscle

Muscle StructureBeginning at the muscle (superficial to deep):

• Epimysium: connective tissue surrounding the whole muscle (many fascicles)

• Perimysium: connective tissue surrounding each fascicle

• Fascicle: perimysium wrapped muscle fibres

• Endomysium: connective tissue surrounding each muscle fibre

• Muscle fiber: muscle cell

• Sarcolemma: a plasma membrane beneath the endomysium that contains the cells sarcoplasm

• Sarcoplasm: similar to cytoplasm of other cells, containing large amounts of glucose & myoglobin (protein that stores oxygen)

• Myofibrils: rodlike contractile elements, that occupy most of the muscle cell and are composed of sarcomeres arranged end to end

• Sarcomeres: a contractile unit composed of myofilaments (actin & myosin)

• Myofilaments:o Myosin (thick): made up of a “head” (attachment site for actin) & “tail”o Actin (thin):

− tropomyosin: arranged along the actin filament, and when relaxed prevent myosin head from binding to actin

− troponin: binding site for calcium

Muscle Structure Cont’d

Properties of a Muscle Fibre

Irritability - ability of muscle to respond to stimulus

Conductivity - ability to transmit nerve impulses

Contractibility - ability to shorten in length

Extensibility - ability to extend in length

Elasticity - ability to stretch and return to normal position

Muscle Teamwork

Agonist (prime mover): • the muscle or group of

muscles producing a desired effect

Antagonist: • the muscle or group of

muscles opposing the action• lengthens when the agonist

muscle contracts

Contractile Machinery:

Origin & InsertionIn order for muscles to contract, they must be attached to the bones to create movement.

Origin: the end of the muscle attached to the bone that does not move (proximal attachment)

Insertion: the point of attachment of the muscle on the bone that moves (distal attachment)