4.1 Neuromuscular function
4.1.1 Label a diagram of a motor unit
4.1.2 Explain the role of neurotransmitters in stimulating skeletal muscle contraction
Neurotransmitters are chemicals that are used for communication between a neuron at the synapse and another cell. 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.
Neurotransmitters are chemicals that are used for communication between a neuron at the synapse and another cell. 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.
4.1.3 Explain how skeletal muscle contracts by the sliding filament theory
4.1.4 Explain how slow and fast twitch fibre types differ in structure and function
Slow-twitch, or type I, fibres have more mitochondria, store oxygen in myoglobin, rely on aerobic metabolism, have a greater capillary to volume ratio and are associated with endurance; these produce ATP more slowly.
Fast-twitch, or type II, fibers have fewer mitochondria, are capable of more powerful (but shorter) contractions, metabolize ATP more quickly, have a lower capillary to volume ratio, and are more likely to accumulate lactic acid.
Fast-twitch, or type II, fibers have fewer mitochondria, are capable of more powerful (but shorter) contractions, metabolize ATP more quickly, have a lower capillary to volume ratio, and are more likely to accumulate lactic acid.
4.2 Joint and movement type
4.2.1 Outline the types of movement of synovial joints
Axes
An axis is a straight line around which an object rotates. Movements at joints take place in a plane about an axis.
The three axis of rotation are:
An axis is a straight line around which an object rotates. Movements at joints take place in a plane about an axis.
The three axis of rotation are:
- Sagittal axis - passes horizontally from posterior to anterior and its formed by the intersection of the sagittal and transverse planes.
- Frontal axis - passes horizontally from left to right and is formed by the intersection of the frontal and transverse planes.
- Vertical axis - passes vertically from inferior to superior and is formed by the intersection of the frontal and sagittal planes.
4.2.2 Outline the types of muscle contraction
Isometric Contraction
In general in this form of contraction the muscle length remains constant. It occurs when muscle force balances resistance and no joint movement occurs
Isometric Contraction
In general in this form of contraction the muscle length remains constant. It occurs when muscle force balances resistance and no joint movement occurs
- there is generally no movement resulting from this type of contraction
- pushing against a fixed object
- planking
Isotonic contraction
an increase in tension (load) results in changes in skeletal muscle length. i.e. lengthening and shortening of the muscle. Concentric contraction Concerns muscle actions that produce a force to overcome the load being acted upon. The work done is referred to as positive work. Eccentric contraction Refers to muscle action in which the muscle force yields to the imposed load. The work done during a concentric contraction is referred to as negative Isokinetic contraction The term is used in two contexts. First, as a specific muscle contraction and second as a testing and rehabilitation machine. When a muscle contracts so that the body segment to which it is attached moves at a constant speed around the joint, rarely found in sport. |
4.2.3 Explain the concept of reciprocal inhibition
When an agonist contract 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 of the motion. This is an automatic action controlled by neurons. When the agonist motoneuron is stimulated the motoneuron to the antagonist is inhibited preventing it from contacting strongly
When an agonist contract 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 of the motion. This is an automatic action controlled by neurons. When the agonist motoneuron is stimulated the motoneuron to the antagonist is inhibited preventing it from contacting strongly
4.2.4 Analyze movements in relation to joint action and muscle contraction
4.2.5 Explain delayed onset muscle soreness (DOMS) in relation to eccentric and concentric muscle contractions
The pain and stiffness felt in muscles several hours to days after unaccustomed or strenuous exercise.
*brought on by eccentric contractions of the muscle causing pressure at the nerve endings.
The pain and stiffness felt in muscles several hours to days after unaccustomed or strenuous exercise.
*brought on by eccentric contractions of the muscle causing pressure at the nerve endings.
- DOMS results primarily from eccentric muscle action and is associated with structural muscle damage, inflammatory reactions in the muscle, overstretching and overtraining.
- DOMS is prevented/minimized by reducing the eccentric component of muscle actions during early training, starting training at a low intensity and gradually increasing the intensity, and warming up before exercise, cooling down after exercise.
4.3 Fundamentals of biomechanics
4.3.1 Define the terms:
force: a push or pull on an object
speed: maximum rate at which a person is able to move their body
velocity: rate at which an object changes position
displacement: distance measured in a stated direction
acceleration: rate of change of velocity (speed/direction) per second
momentum: the amount of motion possessed by a moving object
impulse: force x time. The motion (momentum) of a body depends not only on the force, but also the duration (time) the force is applied
force: a push or pull on an object
speed: maximum rate at which a person is able to move their body
velocity: rate at which an object changes position
displacement: distance measured in a stated direction
acceleration: rate of change of velocity (speed/direction) per second
momentum: the amount of motion possessed by a moving object
impulse: force x time. The motion (momentum) of a body depends not only on the force, but also the duration (time) the force is applied
Scalar
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Vector
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4.3.2 Analyze velocity-time, distance-time, and force-time graphs of sporting actions
4.3.3 Define the term center of mass
the point at which the body is balanced in all directions
the point at which the body is balanced in all directions
4.3.4 Explain that a change in body position during sporting activities can change the position of the center of mass
The center of mass can change when the body is moving dynamically. The center of mass is not always inside the body, it can be outside of the body depending on position.
Sporting Example: High Jump
2. Frosbery Flop
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4.3.5 Distinguish between first, second and third class levers
4.3.6 Label anatomical representations of levers
4.3.6 Label anatomical representations of levers
Fulcrum = the joint
Resistance = body part to be moved
Effort = muscle pull at the muscle insertion
123 FRE (referring to what is in the middle)
Resistance = body part to be moved
Effort = muscle pull at the muscle insertion
123 FRE (referring to what is in the middle)
First class lever: this lever has the fulcrum in the middle, the effort and the load are equally apart from the fulcrum and both push in the same way, in order to balance the object. eg. the head
Second class lever: this lever has its fulcrum on one side. The downward resistance or load is central and the force acting in the opposite direction is furthest away from the fulcrum. eg. standing on the tip toes Third class lever: in this lever the fulcrum again is located on one side. The effort (force) now is closest to the fulcrum and the load is farther away. The effort and resistance are opposing direction. eg. the contracting of the bicep in a curl. |
4.3.7 Define Newton's three laws of motion
4.3.8 Explain how Newton's three laws of motion apply to sporting activities
4.3.8 Explain how Newton's three laws of motion apply to sporting activities
First Law (Law of Inertia)
An object will remain at rest or constant velocity unless acted upon by an external force.
Example: An athlete at a starting block will not move unless a force acts upon them. The external force comes from the block and this propels the sprinter out of the blocks when they exert a downward and backward force against the blocks.
Second Law (Law of Acceleration)
The rate of change of acceleration of an object is proportional to the force applied and acts in the direction of the force.
The acceleration of an object is directly proportional to the force causing it and is inversely proportional to the mass of the object.
Example: Two athletes at a starting block both push off, one is lighter (and has a lesser mass) and therefore accelerates quicker. Two athletes at a starting block of the same mass both push off, the one who applied greater force accelerates faster.
Third Law (Law of Reaction)
For every action there is an equal and opposite reaction
Example: The sprinter applied downward and backward force on the immovable starting blocks, they exert back with a forwards and upward reaction force on the sprinter, pushing the sprinter forwards. The harder the sprinter pushes, the greater the reaction force will be.
An object will remain at rest or constant velocity unless acted upon by an external force.
Example: An athlete at a starting block will not move unless a force acts upon them. The external force comes from the block and this propels the sprinter out of the blocks when they exert a downward and backward force against the blocks.
Second Law (Law of Acceleration)
The rate of change of acceleration of an object is proportional to the force applied and acts in the direction of the force.
The acceleration of an object is directly proportional to the force causing it and is inversely proportional to the mass of the object.
Example: Two athletes at a starting block both push off, one is lighter (and has a lesser mass) and therefore accelerates quicker. Two athletes at a starting block of the same mass both push off, the one who applied greater force accelerates faster.
Third Law (Law of Reaction)
For every action there is an equal and opposite reaction
Example: The sprinter applied downward and backward force on the immovable starting blocks, they exert back with a forwards and upward reaction force on the sprinter, pushing the sprinter forwards. The harder the sprinter pushes, the greater the reaction force will be.
4.3.9 State the relationship between angular momentum, moment of inertia and angular velocity
Angular momentum: the product of the body's moment of inertia, and its angular velocity. M=I*V Moment of inertia: It determines the torque (force that causes rotation) needed for a desired angular acceleration about a rotational axis. It depends on the mass of the object, its shape and its relative point of rotation. Angular velocity: is a ratio of the change of angular displacement and the time during which the change occurred. The rate of which a body spins/rotates/turns through an angle. Angular velocity = angular displacement ÷ time |
4.3.10 Explain the concept of angular momentum in relation to sporting activities
4.3.11 Explain the factors that affect projectile motion at take-off or release
Projectiles are: objects or athletes that are propelled in the air
Influences
Influences
- height of release
- the higher the release = the greater distance covered
- the higher the release = the longer spent in the air
- the higher the release = the longer the horizontal component will be acting
- angle of release
- ideal angle of release is 45 degrees
- the angle changes the relationship between the horizontal and vertical components of projectile
- speed of release (most influential)
- speed is directly related to the distance
- greater the speed = greater the distance
- initial vertical velocity increases the height of the trajectory, creating a longer flight path
- initial horizontal velocity will increase the length of flight time and distance
4.3.12 Outline the Bernoulli principle with respect to projectile motion in sporting activities