SEHS terms in Generating movement in the body

The dark band of a sarcomere, equal to the length of the myosin filaments, which stays the same length during contraction.

A movement in the frontal plane that takes a body part away from the midline of the body, such as raising the arm sideways at the shoulder.

A neurotransmitter released by motor neurons at the neuromuscular junction, which binds to receptors on the sarcolemma and starts a muscle action potential.

The thin protein filament of the sarcomere, anchored to the Z lines, which has binding sites for myosin heads and is pulled towards the centre of the sarcomere during contraction.

A movement in the frontal plane that brings a body part towards the midline of the body, such as lowering the arm from the side back to the trunk.

The muscle that contracts to produce a particular movement at a joint; also called the prime mover.

The principle that when a motor neuron is stimulated above its threshold, all the muscle fibres of that motor unit contract fully, and below threshold none of them contract.

The standard reference posture from which positions and movements are described: standing upright facing forward, feet slightly apart, arms by the sides and palms facing forward.

The muscle on the opposite side of a joint to the agonist, which relaxes and lengthens to allow the agonist to produce a movement.

Two muscles on opposite sides of a joint that produce opposite movements, so that one acts as the agonist while the other acts as the antagonist, such as the biceps and triceps brachii.

A positional term meaning towards the front of the body, also called ventral, for example the patella is anterior to the knee joint.

A collection of standardised body measurements from a large, defined sample of people, used to describe a population's dimensions and percentiles and to design and size equipment.

The measurement of the size, shape, proportions and composition of the human body, including stature, body mass, segment lengths, breadths, girths and skinfolds.

The bones of the upper and lower limbs together with the shoulder and pelvic girdles that attach them to the axial skeleton; its main function is movement.

The smooth layer of hyaline cartilage covering the ends of bones in a synovial joint, which reduces friction between the bones and absorbs and spreads load.

A joint: a place where two or more bones meet, classified by structure as fibrous, cartilaginous or synovial.

A decrease in the size of a muscle caused by a loss of contractile proteins from its fibres, usually because of disuse, immobilisation, injury, illness, ageing or malnutrition.

The part of the skeleton forming the central axis of the body (skull, vertebral column, ribs and sternum), whose main functions are protecting vital organs and supporting the body.

An imaginary line about which a body or body segment rotates, passing through the joint or centre of mass and lying at right angles to the plane of movement.

A multiaxial synovial joint in which a ball-shaped head fits into a cup-shaped socket, allowing movement in all three planes including rotation and circumduction, such as the hip and shoulder.

A hard, living connective tissue whose matrix of collagen is hardened with calcium phosphate; bones support and protect the body, act as levers for movement, store minerals and produce blood cells.

A small fluid-filled sac lined with synovial membrane between a bone and a tendon, ligament or the skin, which reduces friction where these structures move over one another.

A firm, flexible connective tissue without blood vessels, made of collagen fibres in a water-rich matrix, that reduces friction, absorbs shock and gives shape; types are hyaline, fibrocartilage and elastic.

A joint in which the bones are joined by cartilage, usually a fibrocartilage pad, allowing slight movement, such as the joints between vertebrae and the pubic symphysis.

A circular movement in which the distal end of a limb traces a circle while the proximal end stays fixed, combining flexion, abduction, extension and adduction across several planes.

A strong, flexible structural protein forming the fibres of connective tissues; collagen fibres have high tensile strength and stretch very little.

Dense, solid bone tissue that forms the outer layer of every bone and the walls of the shaft of long bones, resisting bending and compression.

An isotonic contraction in which the muscle shortens while producing tension, because the muscle force is greater than the load.

A biaxial synovial joint, also called an ellipsoid joint, in which an oval convex surface fits an oval concave one, allowing flexion, extension, abduction, adduction and circumduction but not rotation, such as the wrist.

Tissue that supports, connects and separates other tissues and organs, made of cells in a matrix of protein fibres (mainly collagen) and ground substance; bone, ligament, tendon, cartilage and fascia are examples.

The temporary link formed when a myosin head binds to a binding site on an actin filament during muscle contraction.

A positional term meaning further from the surface of the body than another structure, for example the femur is deep to the quadriceps.

A downward movement of a body part in the frontal plane, such as lowering the shoulder girdle during a dip.

The shaft of a long bone: a tube of compact bone surrounding the medullary cavity, which contains yellow bone marrow.

A positional term meaning further from the trunk, or from the point where a limb attaches to the trunk, than another structure, for example the ankle is distal to the knee.

A movement at the ankle in the sagittal plane that brings the top of the foot towards the shin, decreasing the angle at the front of the ankle.

An isotonic contraction in which the muscle lengthens while producing tension, because the load is greater than the muscle force; it controls or brakes a movement.

The force applied to a lever to make it rotate; in the human body, the force produced by a contracting muscle at its insertion.

The perpendicular distance from the fulcrum of a lever to the line of action of the effort.

An upward movement of a body part in the frontal plane, such as raising the shoulder girdle in a shrug.

The expanded end of a long bone, made of spongy bone containing red marrow inside a thin shell of compact bone, covered by articular cartilage where it forms a joint.

The scientific study and design of equipment, tasks and environments to fit the people who use them, in order to improve efficiency, comfort and safety.

A movement of the foot in the frontal plane that turns the sole outwards, away from the midline of the body.

A movement in the sagittal plane that increases the angle between the bones at a joint, returning a body part towards the anatomical position, such as straightening the knee.

Sheets of collagen-rich connective tissue that surround and separate muscles and muscle groups, allow them to slide past one another and help transmit force between them.

A bundle of skeletal muscle fibres wrapped in a layer of connective tissue called the perimysium; many fascicles make up a whole muscle.

A tough type of cartilage containing dense bundles of collagen fibres that resists compression and tension, forming the menisci, intervertebral discs and pubic symphysis.

A joint in which the bones are held together by dense fibrous connective tissue without a joint cavity, allowing no or almost no movement, such as the sutures of the skull.

A lever in which the fulcrum lies between the effort and the load, such as the head nodding at the atlanto-occipital joint; its mechanical advantage can be above, equal to or below 1.

A muscle that contracts, usually isometrically, to stabilise the bone to which the agonist is attached, so that the agonist moves only the intended bone.

A movement in the sagittal plane that decreases the angle between the bones at a joint, such as bending the knee or raising the arm forwards at the shoulder.

An axis running horizontally from side to side through a joint or the body; rotation about it occurs in the sagittal plane, as in flexion, extension and a somersault.

A vertical plane running from side to side that divides the body into front and back parts, also called the coronal plane; abduction and adduction occur in it, about the sagittal axis.

The fixed point or axis about which a lever rotates; in the human body, usually a joint.

A synovial joint, also called a plane joint, with nearly flat surfaces that slide over one another in small movements, such as the joints between the carpals.

A protractor-like instrument with two arms, centred over the axis of a joint, used to measure the angle of the joint or its range of motion in degrees.

The lighter region in the centre of the A band containing only myosin filaments, which shortens and may disappear during contraction.

A uniaxial synovial joint in which a convex surface fits into a concave one, allowing only flexion and extension, such as the elbow and knee.

A movement in the transverse plane that takes a limb, raised to the horizontal, backwards away from the midline, as in a discus wind-up; also called horizontal abduction.

A movement in the transverse plane that brings a limb, raised to the horizontal, forwards and across towards the midline, as in a chest press; also called horizontal adduction.

Extension of a joint beyond the anatomical position, such as arching the lower back in a back walkover or swinging the arm behind the body.

A range of motion at several joints well beyond the normal range, which can help in sports such as gymnastics but may reduce joint stability and increase the risk of sprains and dislocations.

An increase in the size of a muscle caused by an increase in the cross-sectional area of its fibres, mainly through the synthesis of more contractile proteins and myofibrils.

The light band of a sarcomere containing only actin filaments, spanning a Z line, which shortens during contraction.

A positional term meaning away from the head or lower down the body than another structure, for example the knee is inferior to the hip.

A positional term describing a structure that lies between a more medial and a more lateral structure, for example the clavicle lies between the sternum and the shoulder joint.

A movement of the foot in the frontal plane that turns the sole inwards, towards the midline of the body.

A muscle contraction in which the muscle changes length at a constant speed throughout the range of movement, usually produced on an isokinetic dynamometer that matches its resistance to the force applied.

A muscle contraction in which tension is produced but the muscle length does not change and no joint movement occurs, because the muscle force equals the opposing force.

A muscle contraction in which the muscle changes length and moves a joint while producing tension; it is either concentric (shortening) or eccentric (lengthening).

A sleeve of dense fibrous connective tissue that surrounds a synovial joint and attaches to the bones on either side, enclosing the joint cavity and holding the bones together.

The ability of a joint to keep its articulating bones in their correct position and to resist displacement or injury during movement.

A positional term meaning further from the midline of the body than another structure, for example the fibula is lateral to the tibia.

A rigid bar that rotates about a fixed point (the fulcrum) when a force (the effort) is applied, in order to move or overcome another force (the load).

A band of dense, regular, collagen-rich connective tissue that joins bone to bone at a joint, stabilising the joint and limiting excessive movement.

The force that a lever acts against, also called the resistance; in the body, the weight of the body segment and of any object held, moved or struck.

The perpendicular distance from the fulcrum of a lever to the line of action of the load.

A bone that is longer than it is wide, with a shaft (diaphysis) and two ends (epiphyses), such as the femur or humerus; long bones act as levers for movement.

An axis running vertically from head to toe, or along the length of a limb; rotation about it occurs in the transverse plane, as in a pirouette or medial rotation.

The line at the centre of a sarcomere that holds the myosin filaments in place and towards which actin is pulled during contraction.

The ratio of the effort arm to the load arm of a lever; a value greater than 1 means a load can be moved with a smaller effort.

The situation in which the effort arm of a lever is shorter than the load arm (mechanical advantage below 1), so a larger effort is needed but the load moves faster and through a greater range.

A positional term meaning closer to the midline of the body than another structure, for example the ulna is medial to the radius in the anatomical position.

A crescent-shaped pad of fibrocartilage between the articular surfaces of a joint, such as the knee, that deepens the joint, absorbs shock and spreads load.

The turning effect of a force about a fulcrum, equal to the force multiplied by the perpendicular distance from the fulcrum to its line of action, measured in newton metres.

A single motor neuron together with all the muscle fibres it innervates; the functional unit of muscle contraction, whose fibres all contract together.

The activation of additional motor units by the nervous system to increase the force of a muscle contraction.

A single skeletal muscle cell, long, cylindrical and multinucleated, containing many myofibrils and surrounded by the sarcolemma.

A long, thread-like structure inside a muscle fibre, made of sarcomeres joined end to end, that contains the contractile filaments actin and myosin.

The thick protein filament of the sarcomere, whose heads bind to actin to form cross-bridges and break down ATP to provide the energy for the power stroke.

The synapse between the axon terminal of a motor neuron and a skeletal muscle fibre, where acetylcholine is released to start a muscle action potential.

A movement of the thumb across the palm so that its tip touches the tip of a finger, combining flexion, abduction and rotation; it allows a precision grip.

The value below which a given percentage of a population falls; for example, 5% of people have a dimension smaller than the 5th percentile value.

The tough fibrous membrane covering the outer surface of bone, except at joint surfaces, carrying blood vessels and nerves, anchoring tendons and ligaments and containing bone-forming cells.

A uniaxial synovial joint in which one bone rotates within a ring formed by another bone and a ligament, allowing rotation only, such as the atlanto-axial and radio-ulnar joints.

An imaginary flat surface dividing the body into two parts, in which a movement takes place; the three planes are the sagittal, frontal and transverse planes.

A movement at the ankle in the sagittal plane that points the foot downwards, away from the shin, as when standing on tiptoe or pushing off in sprinting.

A positional term meaning towards the back of the body, also called dorsal, for example the scapula is posterior to the ribs.

The pivoting of an attached myosin head, powered by energy previously released from ATP, that pulls the actin filament towards the centre of the sarcomere.

Rotation of the forearm in the transverse plane at the radio-ulnar joints so that the palm faces backwards or downwards.

A forward (anterior) movement of a body part in the transverse plane, such as the shoulder blades sliding forwards around the ribs at the end of a punch.

A positional term meaning closer to the trunk, or to the point where a limb attaches to the trunk, than another structure, for example the elbow is proximal to the wrist.

The amount of movement possible at a joint, usually measured in degrees from one end of the movement to the other.

The automatic relaxation of the antagonist when the agonist contracts, caused by inhibitory nerve signals in the spinal cord, which allows smooth and efficient movement at a joint.

The movement that returns the thumb from opposition to its position in the anatomical position.

A backward (posterior) movement of a body part in the transverse plane, such as pulling the shoulder blades together at the end of a rowing stroke.

The turning of a bone about its own longitudinal axis in the transverse plane; medial rotation turns its front towards the midline and lateral rotation away from it.

A biaxial synovial joint whose surfaces are each concave in one direction and convex in the other, allowing flexion, extension, abduction, adduction and circumduction, as at the base of the thumb.

An axis running horizontally from front to back through a joint or the body; rotation about it occurs in the frontal plane, as in abduction, adduction and a cartwheel.

A vertical plane running from front to back that divides the body into left and right parts; flexion and extension occur in it, about the frontal axis.

The cell membrane of a muscle fibre, which carries the muscle action potential along the fibre and into the T-tubules.

The basic contractile unit of a myofibril, the section between two Z lines, containing overlapping actin and myosin filaments.

A network of membranes around each myofibril that stores calcium ions, releases them when a muscle action potential arrives and pumps them back during relaxation.

A lever in which the load lies between the fulcrum and the effort, such as a wheelbarrow or a press-up; its mechanical advantage is always greater than 1.

The principle that motor units are recruited in order of size, from the smallest low-threshold type I units at low forces to the largest type IIx units at the highest forces.

Striated muscle attached to the skeleton by tendons, under voluntary control, that contracts to produce movement, maintain posture and generate heat.

The framework of bones, cartilage and ligaments that supports the body, protects internal organs, allows movement by providing levers for muscles, stores minerals and produces blood cells.

The explanation of muscle contraction in which myosin heads form cross-bridges with actin and pull the actin filaments towards the centre of the sarcomere, so the sarcomere shortens while the filaments keep their length.

Non-striated, involuntary muscle found in the walls of hollow organs such as blood vessels, the gut and the airways, controlled by the autonomic nervous system and hormones.

A description of body shape and composition as three rated components: endomorphy (relative fatness), mesomorphy (relative muscularity) and ectomorphy (relative linearity).

A light, porous lattice of bony struts (trabeculae) inside the ends of long bones and other bones; it absorbs and spreads load and contains red bone marrow.

A positional term meaning closer to the surface of the body than another structure, for example the skin is superficial to the muscles.

A positional term meaning towards the head or higher up the body than another structure, for example the sternum is superior to the pelvis.

Rotation of the forearm in the transverse plane at the radio-ulnar joints so that the palm faces forwards or upwards, as in the anatomical position.

A muscle that assists the agonist in producing a movement or reduces unwanted movement, such as the brachialis helping the biceps brachii to flex the elbow.

The thick, slippery fluid secreted by the synovial membrane into a synovial joint cavity, which lubricates the joint, nourishes the articular cartilage and helps absorb shock.

A freely movable joint in which the bone ends are covered with articular cartilage and separated by a cavity of synovial fluid enclosed in a joint capsule lined with synovial membrane.

The thin membrane lining the inside of the joint capsule of a synovial joint, which secretes synovial fluid into the joint cavity.

A strong cord of dense, regular, collagen-rich connective tissue that attaches muscle to bone, transmitting the force of contraction and storing and returning elastic energy.

A lever in which the effort lies between the fulcrum and the load, such as the biceps flexing the elbow; its mechanical advantage is always less than 1, favouring speed and range.

A horizontal plane that divides the body into upper and lower parts; rotation, pronation and supination occur in it, about the longitudinal axis.

A regulatory protein strand lying along the actin filament that covers the myosin-binding sites when the muscle is relaxed.

A regulatory protein complex on the actin filament that binds calcium ions and, by changing shape, moves tropomyosin away from the myosin-binding sites on actin.

A slow-twitch, slow oxidative muscle fibre with many mitochondria, high myoglobin and a dense capillary supply, which contracts slowly with low force but is highly resistant to fatigue.

A fast-twitch, fast oxidative glycolytic muscle fibre that contracts quickly and forcefully with moderate fatigue resistance, using both oxidative and glycolytic pathways to resynthesise ATP.

A fast-twitch, fast glycolytic muscle fibre with a large motor neuron, high phosphocreatine and glycogen stores and few mitochondria, which produces the greatest force and speed but fatigues quickly.

The column of 33 vertebrae (7 cervical, 12 thoracic, 5 lumbar, the fused sacrum and coccyx) that supports the trunk and head, protects the spinal cord and allows trunk movement.

The principle that bone adapts to the loads placed on it: bone loaded more than usual becomes denser and stronger, and unloaded bone loses mass and strength.

The boundary at each end of a sarcomere, to which the actin filaments are anchored; the Z lines move closer together when the sarcomere contracts.