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.

Irritability: Sensitive to nervous stimuli 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.