Movement Analysis Flashcards
Label a diagram of a motor unit
axon •dendrite • cell body • nucleus • motor end plate • synapse • muscle.
Explain the role of neurotransmitters in stimulating muscle contraction
Acetylcholine
Acetylcholine is the primary neurotransmitter for the motor neurons that innervate skeletal muscle and for most parasympathetic neurons. It is generally an excitatory neurotransmitter, but it can have inhibitory effects at some parasympathetic nerve endings, such as the heart.
In biochemistry, cholinesterase is an enzyme that catalyzes the hydrolysis of the neurotransmitter acetylcholine into choline and acetic acid, a reaction necessary to allow a neuron to return to its resting state after activation.
Explain how skeletal muscle contracts by the sliding filament theory
- Action potentials arrive at motor end plates, which release the transmitter acetylcholine.
- Acetylcholine binds to ligand-gated receptors on the muscle fibre membrane, causing depolarisation.
- Depolarisation spreads through the transverse tubules to the sarcoplasmic reticulum, which simulates Ca2+ channels to open and release calcium into the sarcoplasm.
Some of the Ca2+ ions in the sarcoplasm bind to troponin molecules, which change shape and move tropomyosin away from actin binding sites. - Actin-myosin cross-bridges are formed as the myosin head can now attach to the actin filament. When this happens, a myosin head will release a phosphate from ATP, leading to the “power stroke”.
- Power stroke - The myosin head bends backwards, pulling the thin filament along. Myosin attaching and detaching from actin causes the filaments to slide relative to one another. This movement reduces the sarcomere length (the filaments do not change length).
- The myosin is then released from the actin and fresh ATP can join the myosin head. If the electrical signal is still present, fresh calcium will also be available, and the myosin heads can bind to the next sites on the actin.
Explain how slow and fast twitch fibre types differ in structure and function
Skeletal muscles contain two main types of fibers, which differ in the primary mechanisms they use to produce ATP, the type of motor neuron innervation, and the type of myosin heavy chain expressed. The proportions of each type of fiber varies from muscle to muscle, from animal to animal, and from person to person.
Types of Fibers (Slow Twitch)
Slow-twitch, or type I, fibers (sometimes referred to as “Red”)
• have more mitochondria,
• store oxygen in myoglobin,
• rely on aerobic metabolism,
• have a greater capillary to volume ratio
• They produce ATP more slowly and therefore are associated with endurance. Marathon runners tend to have more type I fibers, generally through a combination of genetics and training (transforming the type IIb into type IIa – more oxidative).
Types of Fibers (Fast fibre)
Fast-twitch, or type II, fibers (sometimes referred to as “White”)
• have fewer mitochondria
• are capable of more powerful (but shorter)
contractions
• metabolize ATP more quickly
• have a lower capillary to volume ratio
• Fiber type IIa and IIb
• are more likely to accumulate lactic acid.
• Weightlifters and sprinters tend to have more type II fibers. Type II fibers are distinguished by their primary sub-types, IIa, IIx, and IIb.
Fibers Types and Performance
Power athletes – Sprinters – Possess high percentage of fast fibers • Endurance athletes – Distance runners – Have high percentage of slow fibers • Others – Weight lifters and nonathletes – Have about 50% slow and 50% fast fibers
• Endurance and resistance training
– Cannot change fast fibers to slow fibers
– Can result in shift from Type IIb to IIa fibers
• Toward more oxidative properties
Outline the types of movement of synovial joints
Abduction: movement away from the body’s center.
Adduction: movement towards the body’s center
Circumduction: making circular movements.
Dorsiflexion: movement of the ankle elevating the sole. (digging in the heel)
Plantar flexion: extending the ankle and elevating the heel. (standing on tiptoes)
Elevation: occurs when a structure moves in a superior (towards head) manner.
e.g. elevating the shoulders or depressing mandible
Depression: movement is inferior (towards feet).
Extension: movement that increases the angle between articulating elements opening the joint.
Flexion: decreases the angle between articulating elements and closes the joint.
Pronation: rotating the palm down. Supination: rotating the palm up.
Rotation: turning the body around a longitudinal axis.
Internal (or medial) Rotation - refers to rotation towards the axis of the body
External (or lateral) Rotation - refers to rotation away from the centre of the body.
Inversion: when the ankle rolls outward.
Eversion: ankle roles inward.
Types of muscle contraction
Concentric: muscle is shortened during contraction.
Eccentric: muscle is lengthening while contracting.
Isotonic: eccentric and concentric contractions are sometimes known as isotonic contractions (meaning “same tension” or “same force”) because the force remains constant during the movement of the body segment affected by the muscle.
What is reciprocal inhibition
Describes muscles on one side of a joint relaxing while the other side is contracting. (antagonistic pairs)
Agonist: muscle that causes the movement.
Antagonist: muscle that works opposite the agonist to return the joint to its initial position.
Reciprocal Inhibition
When an agonist contracts to move a body segment, it is usual for the antagonist (the muscle with the opposite concentric contraction action) to relax. This means that the agonist is not being opposed by any muscle torque acting in the opposite direction to that of the motion. This is called reciprocal inhibition reflex and is an automatic action controlled by neurons.
DELAYED ONSET MUSCLE SORENESS
A high-intensity exercise programme involving eccentric exercise is likely to generate the most soreness
Is associated with injury (within the muscle) or inflammatory actions or overtraining
Normally occurs 24–72 hours after exercise Symptoms can last up to 5 days
Biomechanics
applications of mechanics to the human body and sporting implements, and studies forces on (and caused by) the human body and subsequent result of those forces
Kinematics: study of motion (change in position) of a body or object
Kinetics: forces involved in the movement of an object or body
What is linear motion
When a body moves in a straight line with all its parts moving the same DISTANCE, DIRECTION, and SPEED
What is angular motion
When a body or part of a body moves in a circle or part of a circle about a point (the axis of rotation).
General Motion
General motion is a combination of Linear and Angular motion
