Topic 4

Question 1

Role of Neurotransmitters in stimulating skeletal muscle contraction

Answer 1

Acetylcholine is the neurotransmiter that initiates muscle contraction and Cholinesterase is the enzyme which breaks down acetylcholine and initiates muscle relaxation

Question 2

Sliding Filament Theory

Answer 2

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

Question 3

Fibre types

Answer 3

slow twitch (type 1) , fast twitch (type 2a and 2b

Question 3

A muscle contraction is all about

Answer 3

sarcomeres contracting bringing the Z lines together

Question 4

Type 1

Answer 4

Glycolysis, aerobic (yes oxygen), red, size small, endurance, fatigue slow

Question 5

Type 2a

Answer 5

Glycolysis, anaerobic and aerobic, yes and no oxygen, intermediete, rapid movement max force, fatigue medium, red and white

Question 6

Type 2b

Answer 6

anaerobic (Glycolysis + PCr
No oxygen, white, size big, maximal effect, fast fatigue

Question 7

Types of muscle contractions

Answer 7

isometric: contractions are contractions in which there is no change in the length of the muscle (plank)

isotonic: maintain constant tension in the muscle as the muscle 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

Question 8

Reciprocal inhibition

Answer 8

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

Question 9

DOMS

Answer 9

Delayed Onset Muscle soreness
there is structural damage, inflammatory reactions in the muscle from overstratching and overtraining (usually from eccentric muscle action)

Question 10

DOMS is prevented when …

Answer 10

removing the eccentric component of muscle actions during early training, start with low intensity, warming up before exercising, cooling down after wards

Question 11

Shoulder, Hip, Knee, wrists and elbow

Answer 11

arm flexion, Moving arm forward in sagittal plane

Arm extension, moving the arm backward in the sagittal plane

Question 12

Hip, shoulder

Answer 12

Abduction, moving arm away front the body in a frontal plane

Adduction, moving the arm toward the body in a frontal plane (para dentro)

Question 13

hip (rotation of the hip

Answer 13

Internal or medial rotation, rotating the arm inward

External or lateral rotation, rotating the arm outward

Question 14

shoulder

Answer 14

circumduction is rotating the arm inward

Question 15

Shoulder, elbows, knees and wrists

Answer 15

hip flexion, moving the leg forward in a sagittal plane

In a hip extension, hip moves backwards in a sagittal plane

Question 16

radioulnar joint

Answer 16

Supination, externally rotationg the forearm, palm is up

pronation, internaly rotating the forearm, palm is down

Question 17

ankle

Answer 17

dorsi flexion, poiting the toes up

plantar flexion, tiptoing

Inversion, outward

eversion inward torcer o pé

Question 18

scapula or mandible

Answer 18

elevation of the scapula or mandible

Depression of the scapula or mandible

Question 19

Force

Answer 19

pushing or pulling action that causes a change in state (rest/motion) of a body
F=ma
(N)

Question 20

Speed

Answer 20

The rate at which a body moves from one location to another (scaler)
s=distance traveled/time
(m/s)

Question 21

Distance

Answer 21

Length of a path a body follows (scaler)

Question 22

Displacement

Answer 22

length of a straight line joining the start and finish points (vector)

Question 23

Velocity

Answer 23

rate at which a body moves from one location to another with magnitude and direction making it a vector quantity
V= displacement/time

Question 24

Accelaration

Answer 24

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

Question 25

Momentum

Answer 25

a vector describing a quantity of motion
Momentum = mass times velocity
only happens with an impulse

Question 26

impulse

Answer 26

effect of force over time
I= force times time

Question 27

centre of mass

Answer 27

the point at which the body is balanced in all directions

Question 28

change in the position of the centre of mass

Answer 28

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

Question 29

Distinguish between first, second and third class levers

Answer 29

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)

Question 30

Newtons laws

Answer 30

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))

Question 31

relationship between angular momentum, momentum of inertia and angular velocity

Answer 31

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)

Question 32

explain the factors that affect projectile motion at take-off or release

Answer 32

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

Question 33

Outline the Bernoulli principle with respect to projectile motion in sporting activities

Answer 33

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