Muscular System. Honors Anatomy & Physiology. Susan Chabot Lemon Bay High School

Transcription

1 Muscular System Honors Anatomy & Physiology Susan Chabot Lemon Bay High School

2 Skeletal, Smooth, or Cardiac SKELETAL Striated Voluntary Multinucleated Bound to bones Moves skeleton SMOOTH Not striated Involuntary Single nucleus In hollow organs/ stomach Moves food CARDIAC Striated Involuntary Single nucleus Heart muscle Moves blood

3 The remainder of the chapter will focus on SKELETAL MUSCLE Smooth/Visceral muscle will be covered in the DIGESTIVE system Cardiac muscle will be covered in the CARDIOVASCULAR system.

4 Introduction Muscles are: organs made of specialized cells that use nutrients for energy to contract. Skeletal Muscle action provide: Movement of skeleton Muscle tone and posture Stabilizes joints Generate body heat Not included in book BUT important Protect abdominal organs

5 Make a Cell Using the clay provided, construct a typical cell.

6 Cell vs. Muscle cell/muscle fiber Typical body cells are round with a single, central nucleus. Muscle cells/fibers are elongated often with several nuclei pushed to the outside of the cytoplasm.

7 Skeletal Muscle Structure Composed of several tissue types: Skeletal muscle tissue Nervous tissue Blood (Connective tissue) Dense Connective tissue Attached to bone through a tendon. Attached to other muscles or organs through a sheet-like tendon called an aponeuroses.

8 Connective Tissue Used to separate individual skeletal muscles and hold in position. Insulates and bundles individual skeletal muscle cells, aka muscle fibers. Allows for blood vessels and nerves to pass into the muscle fiber. Allows different parts of the muscle to move independently.

9 TENDON EPImysium ENDOmysium Bone PERImysium FASCICLE MUSCLE FIBER/cell MYOFIBRIL

10 Transform your cell into a muscle fiber

11 Skeletal Muscle Fiber An individual muscle cell. Contracts in response to stimulation. Composed of: Cell membrane = sarcolemma Cytoplasm = sarcoplasm Several small nuclei Mitochondria = possibly HUNDREDS depending on demand placed on the muscle. Myofilaments/Myofibrils that allow for contraction

12 Functional Unit of Muscle = Sarcomere Actin THIN myofilament Myosin THICK myofilament It is the overlapping nature of the ACTIN and Myosin and the connection made between them that allows muscles to contract.

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14 Skeletal Muscle Activity FUNCTIONAL PROPERTIES Excitability can receive message from the brain. Contractility can contract. Extensibility can stretch through use of connective tissues like tendons. Elasticity can return to original position following contraction.

15 How do Muscles KNOW to Contract? A motor neuron communicates the signal to move from the brain to the muscle. A motor neuron is an EFFERENT neuron. The connection between a motor neuron and a muscle fiber is called the NEUROMUSCULAR JUNCTION.

16 What do muscles NEED to contract? Blood supply containing: Oxygen Glucose Water Electrolytes Innervation: information Brain spinal cord spinal nerve nerve Neuromuscular junction and neurotransmitter

17 How do Muscles Contract? Sliding Filament Theory Mitochondria convert carbohydrates and oxygen to ATP. ATP is the energy muscles use to contract. With this energy, the myofilaments ACTIN and MYOSIN inside the muscle fiber slide across one another. This causes the muscle to CONTRACT (shorten) and RELAX (lengthen).

18 MUSCLE PERFORMANCE AND ENERGY TRANSFORMATION

19 Some motor neurons split to several axon terminals to communicate with hundreds of muscle fibers. Some motor neurons hardly split at all and communicate with only a few muscle fibers. The more muscle fibers a motor neuron must communicate with, the less control we have over the muscle. Ex: tongue many neurons/ few cells hamstring single neuron/ many cells

20 Muscle Tone AKA residual muscle tension or tonus Continuous/passive contraction of muscle Muscles resistance to passive stretch during rest Helps maintain posture and declines during sleep Types of Tone/Contraction Isotonic contraction movement Isometric contraction reflexive posture

21 As we exercise beyond our muscle cells ability to meet energy demand, our muscles experience fatigue. Fatigue is the decline in ability to generate force. Factors: Vigorous exercise Barriers to stages of contraction Lack of glucose, oxygen, electrolytes, blood flow

22 When muscles experience fatigue, recovery must occur to restore normal function. Following fatigue, lactic acid is left between the myofibrils and must be removed. Removal is done by: Light exercise to increase blood flow through muscle Light stretching Massage/foam rollers Nutrition Water

23 Have you ever wondered why some people are better sprinter/power athletes and other are better at endurance sports? Muscles can be identified based on their distribution of fast, slow, and intermediate fibers. Slow twitch fibers efficient at ACR, best suited for endurance Fast twitch fibers AnACR, explosive contraction, best suited for sprinting and power Many genes have recently been identified to play a critical role in muscle performance ACTN3 speed gene EPAS1 increased RBC production more energy ACE allelic expression differs in endurance vs sprint athletes.

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