Muscles are the tissues responsible for generating force and thus producing movement.

Types of Muscle Tissue (Brief Overview):

• Skeletal Muscle: Attached to bones, responsible for voluntary movement. These are the muscles we focus on in physical activity. They are striated (striped) and contract quickly.
• Smooth Muscle: Found in the walls of internal organs (e.g., stomach, intestines, blood vessels). Responsible for involuntary movements like digestion and blood flow regulation.
• Cardiac Muscle: Found only in the heart. Responsible for pumping blood throughout the body; also involuntary.

Skeletal Muscle Contraction:

• Muscles contract by shortening, pulling on the bones they are attached to.
• Agonist (Prime Mover): The muscle primarily responsible for a specific movement (e.g., biceps brachii during a bicep curl).
• Antagonist: The muscle that opposes the action of the agonist and must relax to allow the movement to occur (e.g., triceps brachii during a bicep curl).
• Synergists: Muscles that assist the prime mover, often by stabilizing a joint or fine-tuning the movement.
• Fixators: Muscles that stabilize the origin of the prime mover to allow it to work more efficiently.

Major Muscle Groups and Their Actions (Examples):

• Quadriceps (front of thigh): Extend the knee (e.g., kicking, standing up).
• Hamstrings (back of thigh): Flex the knee and extend the hip (e.g., running, jumping).
• Gluteals (buttocks): Extend and abduct the hip (e.g., climbing stairs, powerful jumping).
• Biceps Brachii (front of upper arm): Flex the elbow (e.g., lifting).
• Triceps Brachii (back of upper arm): Extend the elbow (e.g., pushing).
• Pectorals (chest): Adduct and flex the shoulder (e.g., pushing, throwing).
• Latissimus Dorsi (upper back): Extend, adduct, and internally rotate the shoulder (e.g., pulling, rowing).
• Deltoids (shoulders): Abduct, flex, and extend the shoulder (e.g., lifting arms sideways, forward, backward).
• Abdominals (core): Flex and rotate the trunk, stabilize the spine (e.g., sit-ups, core stability).
• Gastrocnemius and Soleus (calves): Plantarflex the ankle (e.g., walking, jumping).

The skeleton provides the rigid framework that muscles pull against to create movement.

Major Bones (Examples):

• Cranium: Protects the brain.
• Vertebral Column (Spine): Supports the body, protects the spinal cord, allows for trunk movement.
• Rib Cage: Protects heart and lungs.
• Humerus (upper arm), Radius/Ulna (forearm): Provide structure for arm movements.
• Femur (thigh), Tibia/Fibula (lower leg): Provide structure for leg movements.
• Pelvis: Supports the trunk, connects to the legs.
• Scapula (shoulder blade), Clavicle (collarbone): Form the shoulder girdle, allowing for a wide range of arm movements.

Joints: The Articulations of Movement

Joints are the points where two or more bones meet. Their structure determines the type and range of movement possible.
- Synovial Joints (Most common for movement): Characterized by a joint capsule containing synovial fluid, which lubricates the joint and reduces friction.
- Hinge Joints: Allow movement in one plane, like a door hinge (e.g., knee, elbow, ankle).
- Ball-and-Socket Joints: Allow for multi-directional movement, including rotation (e.g., shoulder, hip).
- Pivot Joints: Allow rotation around an axis (e.g., joint between radius and ulna allowing forearm rotation, first two vertebrae allowing head rotation).
- Condyloid Joints: Allow movement in two planes (e.g., wrist joint).
- Saddle Joints: Allow movement in two planes with some rotation (e.g., thumb joint).
- Gliding Joints: Allow limited sliding or gliding movements (e.g., between carpals in the wrist).
- Ligaments: Strong, fibrous connective tissues that connect bone to bone, providing stability to joints and preventing excessive movement.
- Tendons: Strong, fibrous connective tissues that connect muscle to bone, transmitting the force of muscle contraction to create movement.
- Cartilage: Smooth, elastic tissue covering the ends of bones at joints, reducing friction and absorbing shock.

The cardiovascular system is the body's transport network, essential for sustained physical activity.

Heart: The pump that propels blood throughout the body. During exercise, heart rate increases to pump more oxygenated blood to muscles.

Blood Vessels:

• Arteries: Carry oxygenated blood away from the heart to the muscles.
• Veins: Carry deoxygenated blood back to the heart from the muscles.
• Capillaries: Tiny, thin-walled vessels where the exchange of oxygen, nutrients, and waste products occurs between blood and muscle cells.

Blood: Carries oxygen (bound to hemoglobin in red blood cells), nutrients, hormones, and removes waste products (carbon dioxide, lactic acid).

Response to Exercise:

• Increased Heart Rate: To pump blood faster.
• Increased Stroke Volume: The amount of blood pumped by the heart with each beat.
• Increased Cardiac Output: The total volume of blood pumped by the heart per minute (Heart Rate x Stroke Volume).
• Redistribution of Blood Flow: Blood is shunted away from less active organs (e.g., digestive system) and directed towards working muscles.
• Increased Oxygen Delivery: More oxygen is delivered to muscles for energy production.
• More Efficient Waste Removal: Lactic acid and carbon dioxide are removed more quickly.