1. Muscle Structure and Function

2. Types of Muscle Skeletal muscle Smooth muscle Cardiac muscle
The human body is comprised of 324 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. Characteristics of a Muscle
Irritability
Muscles have ability to receive and respond to stimuli (force and electrical)
Contractility
Muscle has the ability to shorten
Extendibility
Muscle has the ability to lengthen
Elasticity
Muscle has the ability to return to normal length

4. A. Skeletal (Striated) Muscle
Connects the various parts of the skeleton through one or more connective tissue tendons
During muscle contraction, skeletal muscle shortens and moves various parts of the skeleton
Through graded activation of the muscles, the speed and smoothness of the movement can be gradated
Activated through signals carried to the muscles via nerves (voluntary control)
Repeated activation of a skeletal muscle can lead to fatigue
Biomechanics: assessment of movement and the sequential pattern of muscle activation that move body segments

5. B. Smooth Muscle
Located in the blood vessels, the respiratory tract, the iris of the eye, the gastro-intestinal tract
The contractions are slow and uniform
Functions to alter the activity of various body parts to meet the needs of the body at that time
Is fatigue resistant
Activation is involuntary

6. C. Cardiac Muscle
Has characteristics of both skeletal and smooth muscle
Functions to provide the contractile activity of the heart
Contractile activity can be gradated (like skeletal muscle)
Is very fatigue resistant
Activation of cardiac muscle is involuntary (like smooth muscle)

7. Components of skeletal muscle
a) Muscle b) muscle fibre bundle c) muscle fibre d) myofibril

8. Muscle Fibres Cylinder-shaped cells that make up skeletal muscle
Each fibre is made up of a number of myofilaments
Diameter of fibre ( mm)
Length of fibre (appr. 15 cm)
Surrounded by a connective tissue sheath called Sarcolemma
Many fibres are enclosed by connective tissue sheath Perimycium to form bundle of fibres
Each fibre contains contractile machinery and cell organelles
Activated through impulses via motor end plate
Group of fibres activated via same nerve: motor unit
Each fibre has capillaries that supply nutrients and eliminate waste

9. 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
Synergist:
- the muscles surrounding the joint being moved
Fixators:
- the muscle or group of muscles that steady joints closer to the body axis so that the desired action can occur

10. Bending or straightening of elbow requires the coordinated interplay of the biceps and triceps muscles

11. Contractile Machinery: Tendons, origin, insertion
In order for muscles to contract, they must be attached to the bones to create movement
Tendons: strong fibrous tissues at the ends of each muscle that attach muscle to bone
Origin: the end of the muscle attached to the bone that does not move
Insertion: the point of attachment of the muscle on the bone that moves

12. Muscle Fibre Types Fast twitch fibres: Slow twitch fibres:
Slow Oxidative (Type I)
Fast twitch fibres:
Fast Glycolytic (Type IIb)
Fast Oxidative Glyc. (Type IIb)

13. A. Slow Twitch Fibres
Suited for repeated contractions during activities requiring a force output of < 20-25% of max force output
Examples: lower power activities, endurance events

14. B) Fast Twitch Fibres
Significantly greater force and speed generating capability than slow twitch fibres
Well suited for activities involving high power
Examples: sprinting, jumping, throwing

15. Glycogen fibres Large diameter
Muscle Biopsy
Glycogen fibres Large diameter
Capillary blood
vessels
Oxidative fibres
Small diameter