Muscular System

Muscle Cells

Three Types of muscles Smooth muscle involuntary long cells with mononucleate slow contacting – Found in certain, iris of the eye, digestive system (Intestine)

Three Types of muscles Cardiac muscle Unique to the striated & branched mononucleate involuntary with innate ability to beat

Three Types of muscles Skeletal muscle long cells (fibres) Contraction is voluntary ( ♀ () mass ♂ ( )mass) Tubular and striated

FUNCTIONS OF SKELETAL MUSCLES Support – allow us to and remain upright Move bones – allow us to move and have Help maintain body temp – release large amounts of Help organs and stabilize joints

COOPERATION OF SKELETAL MUSCLE When muscles they They can Because of this to bend joints ( ) Example: bicep and tricep

Muscle Structure Muscles  bundles of muscle fibres  bundles of myofibrils  myofibrils are made of myofilaments ()

Muscle Structure Blood & run between the Muscle cells contain common to other cells and many mitochondria Note: cell membrane = cytoplasm = hemoglobin =

Components of Skeletal Muscle Fibres ComponentDescriptionFunction Muscle fibre muscle cellresponsible for myoglobinO 2 -binding pigment in a skeletal muscle fibre Stores for use during muscle contractions sarcolemmamembrane of a muscle fibresurrounds the muscle fibre and regulates the entry and exit of materials sarcoplasmcytoplasm of a muscle fibresite of processes for normal cell activities; contains myoglobin and glycogen (which stores energy for muscle contractions)

Components of Skeletal Muscle Fibres ComponentDescriptionFunction sarcoplasmic reticulum smooth endoplasmic reticulum in a muscle fibrestores needed for muscle contractions Myofibrilsorganized bundles of myofilaments; cylindrical structures, as long as the muscle fibre itself contain myofilaments that are responsible for muscle contractions thick filamentfine myofilament composed of bundles of protein called myosin (about 11 nm in diameter) binds to actin and causes muscle contractions thin filamentfine myofilament composed of strands of protein called actin (about 5 nm in diameter) binds to myosin and causes muscle contractions

MUSCLE CONTRACTIONS Involve the actions of two types of Actin myofilament Thin Have two strands of actin molecules that wrap around each other

Myosin filament Thick Two molecules wound around each other 10X longer than actin and a different shape

HOW MYOFILAMENTS CONTRACT When a the heads of myosin move first These heads are myofilaments Head bends and pulling the actin myofilament Requires ()to work Part of the

ROLE OF CALCIUM When at heads are not bound to actin because they are by Calcium is needed to move the tropomyosin Calcium and to make a which to, moving it out of the way

Energy for Muscle Contraction Creatine phosphate (aka phosphocreatine) anaerobically donates a group to to form during initial intense muscular effort (similar neuronal function in the brain)

Creatine phosphate builds up and is stored in muscle. For the muscle to, it needs to. (A) When the muscle starts, it stored. This generates some ATP that is used immediately. (B) To continue contracting, the muscle carries out as long as is available. When the oxygen has been used up, the muscle can carry out for a limited period of time. Fermentation results in only a small amount of ATP compared with the amount produced by aerobic cellular respiration, and. Once the muscle resumes resting (purple box), creatine phosphate builds up again.

Energy for Muscle Contraction Aerobic respiration provides energy as is available occurs in myoglobin (cf.) in the muscles stores O 2 to be used by the muscle when activity begins

Energy for Muscle Contraction Anaerobic respiration small amounts of ATP producing cramping & fatigue after 2-3 mins lactic acid is back to

Oxygen Debt Muscles can function with an more than other tissues Benefits of aerobic training: increased ability of to deliver O 2 increased mitochondria to process O 2

Isometric & Isotonic Contraction Isometric muscle vs. muscle can rapidly & strength Isotonic involves movement

Body Posture Many of the muscles of the body employ contractions to support the body or some part of it (Example: )

Muscle Tone Is the result of of different parts of a muscle (good muscle tone – muscle always under a and ready for action)

Tendons & Ligaments Tendons Ligaments

Muscle Twitch Individual muscle cells fully or not at all () Heavy Light loads use less cells

Slow Twitch Fibers Slow twitch fibers are used for and biking Contract and Produce most of their energy (with ) They are because they have many and myogloblin (respiratory pigment) they also have more to be continually supplied with oxygen.

Fast Twitch Fibers Fast twitch fibers are used in and weight lifting They but can They are rich in () because they depend on (no ) produced energy They are and myoglobin (oxygen)

Different Types of Muscle Fibres Intermediate-twitch () Fast twitch with Endurance training can proportion of these fibers in a muscle Genetic component

Different Types of Muscle Fibres Skeletal muscles have of fast-twitch and slow-twitch fibres. Thus, the force and response times of their contractions differ.

Myograms These graphs show the force of muscle contraction with time. (A) A simple muscle twitch has three periods:,, and. (B) When a muscle is not allowed to relax completely between stimuli, the contraction gradually increases in intensity until it reaches a maximum, which is sustained until the muscle fatigues.

Muscle Atrophy Unused muscles will, Initially but may become Fig

Muscle Exercise in muscle mass Muscle fibres get ( ) Myofibrils get

Benefits of Training Muscles Stay Have supply Better storage

Muscles & Homeostasis Muscle contraction produces heat  Cardiac & systems rely on well functioning muscles Support of & many other activities are supported by the muscular system

Disorders of the Muscular System Muscular H ereditary condition Skeletal muscles and are replaced by Poor blood circulation  muscle degeneration

Disorders of the Muscular System Botulism () Potentially muscular paralysis Toxin produced by the release of by cells of the nervous system 

Disorders of the Muscular System Cramps Painful triggered by strenuous exercise, extreme cold,, salt (electrolyte) imbalance, low blood glucose, or reduced blood flow

Disorders of the Muscular System Contracture Abnormal muscle (not caused by nerve stimulation) Can result from from the or from the contraction of scar tissue (Example: severe burns)

Disorders of the Muscular System Fibromyalgia Chronic muscular pain and tenderness often associated with and sleep disturbances Can be caused by, physical or emotional trauma, or medications Considered a controversial diagnosis, due to consensus to its cause 9:1 ( ♀ : ♂ )

Disorders of the Muscular System Crush Syndrome Shock-like state following of the muscles (Example: collapse of a building or a traffic accident) Associated with, heart irregularities (caused by released from the muscles), and (caused by blockage of the renal tubules with myoglobin released by the traumatized muscles)

Disorders of the Muscular System Delayed Onset Muscle Soreness Pain & felt after novel strenuous exercise (begins 8-24 hours after exercise, peaks hours after exercise and subsides over the next 5-7 days) Associated with, disruptions in the myofibrils & sarcolemma, and increased levels of and muscle-fibre enzymes

Disorders of the Muscular System Myositis Muscle inflammation and weakness resulting from or an

Chapter Review What body systems do muscles support? How do muscles support these systems? Explain the difference in muscle composition between a person who is not active versus someone who is very active? Describe two different types of muscle injuries. Recommend appropriate treatments for each. Explain how muscles change with strength training? With endurance training? With inactivity?

Concept Organizer

Chapter Summary All muscles do their work by contracting. Relaxation is the passive state of a muscle. There are three types of muscle cells: skeletal, smooth, and cardiac. Skeletal muscle cells are attached to the bones of the skeleton, have many nuclei, are striated and tubular, and contract voluntarily. Smooth muscle cells are found in the walls of internal organs, have one nucleus, are not striated, and contract involuntarily. Cardiac muscle cells form the walls of the heart; have one nucleus, are striated, tubular, and branched; and contract involuntarily.

Chapter Summary The fact that skeletal muscles can only either contract or relax means they can pull but not push. Therefore, they must work in pairs to move any part of the body—a relaxed muscle is only lengthened when the opposing muscle contracts to stretch it. Skeletal muscle contractions are explained by the sliding filament model. Skeletal muscle produces heat as well as movement and also supports and pads the body. Each muscle is made up of clusters of bundles of muscle fibres, which enclose bundles of myofibrils containing thin myofilaments of actin and thick myofilaments of myosin. Blood vessels supply nutrients and oxygen to the fibre bundles and remove wastes. The oxygen fuels the cellular respiration that supplies most of the energy muscles use.

Chapter Summary Nerves trigger and control muscle contractions, which last for only a fraction of second in each muscle fibre. It is the wave of successive contractions, or twitches, that result in a muscle contraction. Skeletal muscles have both slow and fast-twitch fibres that are good for either endurance (slow-twitch) or intense (fast- twitch) activities. Using the skeletal muscles is the only way to maintain and build their function.