Download The muscular system

THE MUSCULAR SYSTEM
LEARNING GOALS
• I will be able to identify the functions, characteristics and types of muscle.
• I will understand the terms associated with muscle naming and function.
FUNCTIONS
• Locomotion – All body movements and many body
functions (arms, heart, intestines…).
• Posture – Even when relaxed muscles are working to keep
you upright (neck, lower back…)
• Heat production – Body needs a basal temperature and
muscles keep this by releasing heat as a by-product of
reactions.
CHARACTERISTICS
• Irritability: Sensitive to nervous stimuli
• Contractility: Responds to stimuli by
shortening
• Extensibility: Can be stretched when relaxed
• Elasticity: Return to normal length when
relaxed
3 TYPES OF MUSCLE
• Muscle makes up 30-35% (in women) and 42-47% (in men) of body mass.
• Smooth
• Cardiac
• Skeletal
1. SMOOTH (VISCERAL) MUSCLE
• usually found in hollow internal organs (stomach, intestines bladder)
• involuntary muscle
• lacks the appearance of striations
• SM cells shorter than skeletal muscle cells
2. CARDIAC
• Occurs only in the heart
• Controlled involuntarily
• Can continue to function without nerve impulses
• striated in appearance and the cells are joined end to end
• Very fatigue resistant
3. SKELETAL
• Over 400
• Contraction is voluntary
• Striated in appearance (alternating dark and light bands)
• When stimulated by a nerve fibre it contracts and relaxes
• Includes both fast twitch and slow twitch fibers
• attached to bones; responsible for movement
• Also used in talking, breathing, swallowing and singing.
MUSCLE ATTACHMENT
• Muscle attaches to bone either directly or indirectly.
INDIRECT ATTACHMENT
• When attached indirectly, the epimysium that surrounds the exterior
of the muscle fibre extends past the muscle as a tendon and then
attached to the periosteum.
DIRECT ATTACHMENT
• When attached directly, the epimysium fuses with the periosteum.
CONNECTIVE TISSUE
• Tendons and ligaments are connective tissue that help to improve the stability
of the joint.
• In order for muscles to contract, they must be attached to the bones to create
movement
• A tendon is a connective tissue that attaches the muscle to the bone.
CONNECTIVE TISSUE
• Ligaments are tough connecting tissue that run from bone to bone limiting the
movement of the joint and helps to maintain the stability of the joint.
• Tendons and ligaments are not very elastic and lose their ability to perform
correctly when stretched.
• If repeatedly stretched or torn, surgery may be necessary to repair the
damage.
ACTIONS OF MUSCULAR SYSTEM
• movement a muscle causes depends on where it is attached to a bone and
how it is crosses a joint.
• ORIGIN: Immovable end (proximal end)
• INSERTION: The moveable end of the joint (distal end)
• When a muscle contracts, its insertion is pulled toward its origin.
• For example, when you contract your biceps, you pull your forearm
towards your shoulder, so you are pulling towards the origin.
• The insertion is on the radius, called the radial tuberosity, and it is the
forearm that moves during contraction.
AGONIST AND ANTAGONIST MUSCLE
PAIRS
• Muscles pull. They never push.
• Skeletal muscles typically arranged as opposing pairs.
• AGONIST: muscle primarily responsible for movement of a body part
• ANTAGONIST: muscle that counteracts the agonist, lengthening when the
agonist muscle contracts.
• Many muscles are paired in agonist – antagonist relations
• (Ex. Bicep and Triceps)
MUSCLE DEVELOPMENT
• Most muscles have formed by the 8th week of pregnancy.
• Most women can feel movement by the 17th week of pregnancy.
• At birth you have a fixed amount of muscle cells.
• Growth of muscle cells depend on their use.
• Atrophy – decrease in muscle cell diameter due to neglect of stimulation
• Hypertrophy – increase in muscle cell diameter due to stimulation
LEARNING GOALS
• I will be able to identify the functions, characteristics and types of muscle.
• I will understand the terms associated with muscle naming and function.