Applied anatomy and physiology

• Skeletal muscles are made up of thousands of muscle fibers, each one of which is made of a myofibril.
• When skeletal muscles contract, all the thousands of muscle fibers contract, resulting in a contraction of the entire muscle.
• The cerebellum, located in the brain, controls all muscular contractions.
• A neuron, also known as a nerve, is a cell that transmits impulses.
• An impulse generated by a cell in the cerebellum will pass through a neuron or a nerve into the muscle fibers, causing them to contract.
• A motor unit consists of a cell in the cerebellum, a neuron or a nerve, and the muscle fibers themselves.
• To contract the muscle fibers, the cell body produces an impulse which passes down the neuron or the nerve to the motor endplate, causing the muscle fibers to contract.
• The strength of a contraction can be varied by recruiting the correct number of motor units and the correct size of motor units.
• Neurotransmitter acetylcholine is released into the synaptic cleft to allow the impulse or action potential to move from the motor endplate into the muscle fiber.
• If the impulse or action potential is big enough and there is enough neurotransmitter, it will cross the synaptic cleft into the muscle fiber, causing the muscle fiber to contract.
• The synaptic cleft is the gap between the end of the motor endplate and the wavy edge of the muscle fiber.
• The all-or-none law states that if the charge is above the threshold the muscle fibre will contract if not nothing will happen
• The impulse has to travel from the cell body down the neuron to the motor endplate to stimulate the muscle fibre to contract.
• The impulse is set by the cerebellum or the cell body and that impulse or action potential is sent down the neuron to the motor endplate.
• The neuron has these little finger-like structures called motor end plates that attach the neuron onto the muscle fiber.
• Muscle fibers are made up of smaller structures called myofibrils.
• The impulse or action potential is set by the cerebellum or the cell body and that impulse or action potential is sent down the neuron to the motor endplate.
• what effects the strength of a contraction

  amount of fibres recruited
• the 5 joints are hinge, ball and socket, condyloid, pivot and gliding
• an isotonic contraction is when a muscle changes length during contraction
• isometric contractions occur when there is no change in muscle length but tension remains constant throughout the movement
• dorsi and plantar flexion happens at the ankle joints
• the anterior deltoid and posterior deltoid move the shoulder by flexion and extension
• adduction occurs at the knee joint
• extension occurs at the elbow joint
• abduction occurs at the hip joint
• flexion occurs at the wrist joint
• The biceps brachii muscle is responsible for flexing the forearm at the elbow joint.
• The triceps brachii muscle extends the arm at the elbow joint.
• slow oxidative muscle fibres are slow twitch and work aerobically
• fast glycolytic muscle fibers are fast twitch and work anaerobically
• fast oxidative glycolytic fibres work anaerobically to provide energy for muscle contraction
• fast oxidative have the ability to resist fatigue unlike fast glycolytic
• The heart produces its own heartbeat through the contraction and relaxation phases known as systole and diastole.
• The heart's atria receive blood from the body and the lungs and pump it into the ventricles, which are then pumped back to the lungs or out into the rest of the body.
• The heart's contraction begins with the SA node, also known as the pacemaker, which generates an electrical impulse that spreads across the atria, creating atrial systole.
• The SA node, located in the heart, creates an impulse and this creates atrial systole.
• The AV node then releases the impulse down the bundle of hiss into the Purkinje fibers.
• The atria then contract after the impulse reaches the AV node.
• The AV node, located in the heart, squeezes blood into the ventricles and holds the impulse for 0.1-0.2 seconds, giving the ventricles a chance to fill with blood.