Muscular System Unit Test on Friday 11-20

Muscle Types Skeletal: a.) Attach to skeleton b.) Striated b/c fibers appear to be stripped c.) voluntary (conscious control/ reflexes) Cardiac: a.) Found in the heart b.) Striated c.) Involuntary (occurs automatically) Smooth: a.) Found in walls in hallow visceral organs- propels substances along pathway. b.) No striations c.) Involuntary

Functions of Muscles Producing Movement Maintaining Posture Stabilizing Joints Generating Heat (is a by-product of muscle activity)

Stimulation & Contraction of muscle cells 1. Must be stimulated by nerve impulses to contract. 2. One motor neuron may stimulate a few muscle cells or hundreds. * One neuron and all the skeletal muscle cells it stimulates are a motor unit. 3. When the nerve fiber or axon reaches the muscle it branches into a number or terminals. Although they are close, they never touch. The gap between is called the synaptic cleft & is filled with tissue fluid (interstitial). 4. When the nerve impulse reaches the axonal terminals, a neurotransmitter is released (ACh).

Contraction Continued… ACh diffuses across the synaptic cleft & attaches to receptors (membrane proteins). If enough ACh is released, the muscle fibers at that point become temporarily permeable to sodium ions, which rush into the muscle cell. This sudden rush of sodium ions gives the cell interior an excess of positive ions, which upsets and changes the electrical conditions of the muscle fiber. This upset generates an electrical current called an action potential. Once begun the action potential is unstoppable; creating an electrical impulse from one end of the cell to the other. The result= contraction of muscle cell.

Types of Muscle Contractions…Isotonic vs. Isometric Isotonic: The muscle shortens and the movement occurs . Isometric: Tension in the muscle keeps increasing. Example: Muscles are contracting isometrically when you try to lift a 400 lb. dresser alone. Example: When you straighten a bent elbow, the triceps is contracting isotonically. Example: When you push against a wall with bent elbows, the wall doesn’t move and the triceps muscles, which cannot shorten to straighten the elbow are contracting isometrically. Isotonic Isometric

Use it or Lose it… Benefits of regular Exercise: a.) Aerobic/Endurance (with oxygen, anaerobic= without oxygen)- Stronger, more flexible, & a greater resistant to fatigue. b.) Blood supply increases, individual cells form more mitochondria (powerhouse of cell, helps use nutrients for energy) & store more oxygen. c.) Increases metabolism, improves digestion (and elimination), enhances coordination, makes skeleton stronger, heart enlarges (hypertrophies)= more more blood pumped with each beat. Fat deposits cleared, lunges become more efficient in gas exchange.

How Muscles Attach 600 total muscles All are attached to either bone or connective tissue structures at 2 points called Origin and Insertion. Origin= attached to immovable or less moveable bone Insertion= attached to moveable one. During Muscle Contraction, the insertion moves toward the origin.

They all Work together to form smooth, precise movements. Types of Muscles… They all Work together to form smooth, precise movements. Prime Movers: major responsibility for causing a particular movement. Ex: biceps is PM for elbow flexion. Antagonists: Oppose or reverse a movement. Synergists: Help prime movers by producing the same movement or by reducing undesired movements. Ex: You can make a fist without bending your wrist because synergist muscles stabilize the wrist joints and allow the prime mover to act on the finger joint. Fixators: Specialized synergists. They hold a bone still or stabilize the origin of a prime mover. Ex: The Postural muscles that stabilize the vertebral column are fixators, as the muscles that anchor the scapula to the thorax.

Types of Muscle Movements Flexion: Decreases angle of joint, brings two bones closer together. Extension: Increases the angle, increases the distance between two bones (or parts of the body). Rotation: movement of a bone around its axis. Most common in ball-and-socket joints. Abduction: Moving a limb away from the midline. Adduction: Movement of a limp towards the midline or body. Circumduction: The proximal end of a limb is stationary, and its distal end moves in a circle.

Special Movements Dorsiflexion & Plantar Flexion: Up & down movements of the foot at the ankle. Lifting the foot so its superior surface approaches the shin (standing on your heels)= dorsiflexion. Pointing the toes is called plantar flexion. Inversion & Eversion: To invert the foot, turn the sole medially. To evert the foot, turn the sole laterally. Supination & Pronation: Refer to the motion of the radius around the ulna. Supination occurs when the forearm rotates laterally so the palm faces anteriorly (radius and ulna are parallel). Pronation occurs when the forearm rotates medially so the palm faces posteriorly. Pronation brings the radius across the ulna to form an X.

Lets Learn Some Muscles! Trapezius

Arm & Shoulder

Muscles of the Abdomen

Muscles of the Back Sternocleidomastoid Erector Spinae Trapezius Deltoid Illiocostalis Longissimus Spinalis Erector Spinae Latissimus Dorsi

Muscles of the Butt & Upper Leg .

Muscles of the Thigh (Anterior) Quadriceps Illiopsoas

Lower Leg Anterior View Posterior View