1. 11.2 Muscles and Movement

2. Learning Objectives To describe the components of the skeletal system
To be familiar with one joint and its structure – the elbow
To compare the functioning of different sorts of joint
To describe the macro and micro structures of skeletal muscle
To explain the sliding-filament action of muscular contraction

3. The Skeletal System The skeletal system consists of: BONES LIGAMENTS
MUSCLES
TENDONS
NERVES
The interaction between these structures enables human movement

4. The Elbow

5. The structures of the Elbow
BONES:
Humerus
Radius & Ulna
MUSCLES (Antagonistic pair)
Biceps
Triceps
CARTILAGE
JOINT CAPSULE & SYNOVIAL FLUID

6. The Knee and Hip joints
The knee is a HINGE joint and allows movement in one plane only
The hip is a ball and socket joint and allows movement in three planes

7. 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

8. 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

9. 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

10. 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)

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

12. 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 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

13. Muscle Teamwork
Agonist (prime mover):
- the muscle or group of muscles which bend a joint - FLEXORS
Antagonist:
- the muscle or group of muscles which straighten a joint – EXTENSORS
When one group of muscles is contracting and doing work, the other group is relaxing. This teamwork allows fine control of joint movement.

14. Bending or straightening of elbow requires the coordinated interplay of the biceps (flexor) and triceps (extensor) muscles

15. Contractile Machinery: Sarcomeres
Contractile units
Organized in series ( attached end to end)
Two types of protein myofilaments:
- Actin: thin filament
- Myosin: thick filament
Each myosin is surrounded by six actin filaments
Projecting from each myosin are tiny contractile myosin bridges
Longitudinal section of myofibril
(a) At rest

16. High microscope magnification of sarcomeres within a myofibril

17. Contractile Machinery: Crossbridge formation and movement
Cross bridge formation: a signal comes from the motor nerve activating the fibre by causing the release of calcium ions from the sarcoplasmic reticulum the heads of the myosin filaments temporarily attach themselves to the actin filaments
Cross bridge movement:
- similar to the stroking of the oars and movement of rowing shell
- movement of myosin filaments in relation to actin filaments
- shortening of the sarcomere
- shortening of each sarcomere is additive
Longitudinal section of myofibril