Topic 4 Flashcards
Role of Neurotransmitters in stimulating skeletal muscle contraction
Acetylcholine is the neurotransmiter that initiates muscle contraction and Cholinesterase is the enzyme which breaks down acetylcholine and initiates muscle relaxation
Sliding Filament Theory
Myofibril is surrounded by sarcoplasmic reticulum
there each myofibril can be broken down into functional repeating segments called sarcomere
sarcomere consists of actin and myosin
When a nerve impulse arrives at the muscle, it causes the release of a chemical called acetylcholine
This presence causes depolarization enabling calcium to be released from the sarcoplasmic reticulum
The calcium binds to troponin changing its shape and so moving tropomyosin from the active site of the actin
The myosin filaments can now attatch to the actin forming a cross bridge
The breakdown of atp releases energy which enables the myosin to pull the actin filaments (occurs along the entire length of every myofibril in the muscle cell)
When the ATP molecule binds to the myosin head, the myosin detaches from the actin and the cross bridge is broken
when atp is then broken down the myosin head can again attatch to an actin biding site further along the actin filament
lasts as long as adequate ATP and CA+ stores
The nerve impulse stops the CA+ is pumped back to the sarcoplasmic reticulum and the actin returns to its resting position causing the muscle to lengthen and the muscle to relax
Z line: where actin is
A band: myosin
H zone: myosin not in contact with actin
Fibre types
slow twitch (type 1) , fast twitch (type 2a and 2b
A muscle contraction is all about
sarcomeres contracting bringing the Z lines together reducing the H zone while A band doesn´t change
Type 1
Glycolysis, aerobic (yes oxygen), red, size small, endurance, fatigue slow
Type 2a
Glycolysis, anaerobic and aerobic, yes and no oxygen, intermediete, rapid movement max force, fatigue medium, red and white
Type 2b
anaerobic (Glycolysis + PCr
No oxygen, white, size big, maximal effect, fast fatigue
Types of muscle contractions
isometric: contractions are contractions in which there is no change in the length of the muscle (plank)
isotonic:muscle contracts while it changes lengths (push ups)
isokinetic: the muscular contraction that accompanies constant velocity limb movements around a joint (riding a stationary bike)
concentric: muscles shorten while generating force
Eccentric: total length of muscle increases as tension is produced
Reciprocal inhibition
process in which a muscle must relax (agonistic) on one side of a joint to allow for a muscle on the other side on the joint, the antagonistic to contract
DOMS
Delayed Onset Muscle soreness
there is structural damage, inflammatory reactions in the muscle from overstratching and overtraining (usually from eccentric muscle action)
DOMS is prevented when …
removing the eccentric component of muscle actions during early training, start with low intensity, warming up before exercising, cooling down after wards
Shoulder, Hip, Knee, wrists and elbow
arm flexion, Moving arm forward in sagittal plane
Arm extension, moving the arm backward in the sagittal plane
Hip, shoulder
Abduction, moving arm away front the body in a frontal plane
Adduction, moving the arm toward the body in a frontal plane (para dentro)
hip (rotation of the hip
Internal or medial rotation, rotating the arm inward
External or lateral rotation, rotating the arm outward
shoulder
circumduction is rotating the arm inward
Shoulder, elbows, knees and wrists
hip flexion, moving the leg forward in a sagittal plane
In a hip extension, hip moves backwards in a sagittal plane
radioulnar joint
Supination, externally rotationg the forearm, palm is up
pronation, internaly rotating the forearm, palm is down
ankle
dorsi flexion, poiting the toes up
plantar flexion, tiptoing
Inversion, sola do pé para dentro
eversion sola do pé para fora
scapula or mandible
elevation of the scapula or mandible
Depression of the scapula or mandible
Force
pushing or pulling action that causes a change in state (rest/motion) of a body
F=ma
(N)
Speed
The rate at which a body moves from one location to another (scaler)
s=distance traveled/time
(m/s)
Distance
Length of a path a body follows (scaler)
Displacement
length of a straight line joining the start and finish points (vector)
Velocity
rate at which a body moves from one location to another with magnitude and direction making it a vector quantity
V= displacement/time
Accelaration
rate at which velocity changes over time and the ability to change ones speed from either a static position or moving state (vector)
A= final velocity-initial velocity
Momentum
a vector describing a quantity of motion
Momentum = mass times velocity
only happens with an impulse
impulse
effect of force over time
I= force times time
centre of mass
the point at which the body is balanced in all directions
change in the position of the centre of mass
High jump: when the athlete arches the back, the center of mass will lie below the bar due to the curved shape
Rowing: The center of mass is located around the pelvic area when sitting down, once the legs extend and the body leans back whilst rowing, the centre of mass moves horizontally but remains inside the body
Distinguish between first, second and third class levers
Lever consists of a rigid rob, a fulcrum, a resistance force and an effort force (used to amplify force)
effort arm/ resistance arm
First class: effort force and resistance force on opposite sides of the fulcrum
(neck muscles providing force to support the head)
Second class: effort force and resistance force on the same side of the fulcrum
effort arm is longer than the resistance arm (effort is further away)
(calve muscles in plantar flexion ankle joint) (more than 1 mechanical advantage)
third class: effort and resistance force on the same side but resistance arm is longer (less than 1 mechanical advantage)
(biceps branchii for elbow joint to lift weights)
Newtons laws
1- Law of inertia (an object at rest will remain at rest until a force acts upon it)
2- law of acceleration (the rate of momentum of a body is proportional to the force causing it and the change in the direction in which the force acts F=ma
3- Law of action and reaction (an action will have an equal and opposite reaction (force that is acting at the end of the bat will cause the ball to be batted away))
relationship between angular momentum, momentum of inertia and angular velocity
Angular velocity: velocity at which an object rotates
Momentum of inertia: the force needed for an object to rotate (depends on mass and shape)
Angular momentum= momentum of inertia times angular velocity (the amount of rotation of a body, this remains constant)
explain the factors that affect projectile motion at take-off or release
angle (45 degrees from the floor but depends on the sport)
Hight of release: the higher the further
Speed of release: the greater the force, the greater the distance
Outline the Bernoulli principle with respect to projectile motion in sporting activities
a projectile experiences airflow velocity and air pressure.
When the projectile has back spin, there are uneven pressures on it which cause it to deviate from its path. the pressure difference (due to rotation) causes a lift force. this is the Magnus force which is that when moving through air the air dragged around by rotation causes an increased velocity on one side and decrease in another
Planes, the Motor Neuron, movement of synovial joints, analyse velocity-time, distance-time and force-time graphs and label the anatomical representations of levers (effort, load, fulcrum and the muscles/ bones involved)
