Differentiate Skeletal muscle from cardiac and smooth muscle Muscles Objectives: Differentiate Skeletal muscle from cardiac and smooth muscle Define key terms: fascicle, epimysium, perimysium, endomysium, muscle fibre, myofibril, sarcomere, actin, myosin, sarcoplasm, sarcolemma, sarcoplasmic reticulum.

Human Muscle Types and Functions There are three types of muscles found in humans: 1. Cardiac Muscle: Found in the heart. It does not fatigue (it cannot respire anaerobically) and is myogenic (controls its own contractions through the SA Node) 2. Smooth Muscle: Found in blood vessels and the gut – moves food through the gut and controls vascular shunting in blood vessels (involuntary) http://www.cellsalive.com/myocyte.htm http://mcdb.colorado.edu/courses/2115/units/Other/Beating%20heart%20with%20nodes.mov

3. Skeletal Muscle Attached to the skeleton and responsible for: Movement Support and posture Heat generation

Properties of Skeletal Muscle Extensibility: - ability of muscle to lengthen while contracting and provide the effort required to move the lever system Elasticity: – ability of muscle to return to its normal length after stretching, enabling the muscle to perform repeated contractions without losing power Contractility: – capacity of the muscle to contract/shorten forcibly when stimulated by nerves and hormones.

Skeletal Muscle Structure Muscle belly

Recapping Basic Joint Structure Pig trotter dissection – can you identify… Skin Muscle Tendon Bone Connective Tissue Ligament Cartilage (last two may not be easily identifiable)

What are the features of a muscle fibre? Fascicle Muscle fibre Myofibril What are the features of a muscle fibre?

Microscopic Structure of Skeletal Muscle Muscle fibre is the name given to a muscle cell. Muscle fibres are: Long – up to 30cm depending on length of muscle Multinucleate (several thousand nuclei in a 30cm fibre) Packed full of myofibrils – bundles of protein filaments 1μm wide that run the length of the muscle fibre Packed full of mitochondria which are squashed between the myofibrils. Well supplied with blood – 3 or 4 capillaries surround each fibre in a non-athlete, up to 7 in a highly trained athlete

What are the features of a myofibril? Myofibrils are bundles of protein filaments that run the length of the muscle fibre They are made of repeating subunits of the protein fibres called sarcomeres. The myofibrils are made of two main proteins, actin and myosin, that are responsible for muscle contraction

New terms for muscle fibres: Sarcolemma: Sarcoplasm: Sarcoplasmic reticulum: Muscle fibre cell surface membrane Muscle fibre cytoplasm Type of SER (smooth endplasmic reticulum) found in muscle fibres Its role is to release Ca2+ to stimulate muscle contraction. It is connected to the sarcolemma by T-Tubules.