1. Muscle Structure and Function

2. Types of Muscle Skeletal muscle Smooth muscle Cardiac 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

3. Key Terms
Tendons - tough bands of connective tissue that join muscle to bone
Aponeurosis – 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 form
Muscle tissue - collection of cells that shorten during contraction, therefore creating tension that results in movement

4. 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

5. 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

6. 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

7. Components of skeletal muscle
a) Muscle b) Fascicle c) Muscle fiber d) Myofibril

8. Muscle Structure Beginning 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)

9. Muscle Structure Cont’d
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:
Myosin (thick): made up of a “head” (attachment site for actin) & “tail”
Actin (thin):
tropomyosin: arranged along the actin filament, and when relaxed
prevent myosin head from binding to actin
troponin: binding site for calcium

10. 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

11. Muscle Teamwork Agonist (prime mover): Antagonist:
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

12. Contractile Machinery: Origin & Insertion
In 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)