SEHS TOPIC 4

Question 1

What are the main two parts of the nervous system?

Answer 1

The central nervous system and the peripheral nervous system.

Question 2

CNS features

Answer 2

Brain and spinal cord. The brain uses your nerves to send the messages to the rest of your body. Most of the sensing and control takes place here.

Question 3

Myelin

Answer 3

Each nerve has a protective outer layer called myelin. Myelin insulates the nerve and helps the message get through.

Question 4

Peripheral nervous system

Answer 4

many nerves that branch out from your CNS all over your body. This system relays information from the brain and spinal cord to the organs, arms, legs, fingers and toes. Contains: Somatic nervous system (voluntary movements) & Autonomic nervous system (involuntary movements).

Question 5

Sensory neurons

Answer 5

afferent neurons –> nerve cells that are activated by sensory input from the environment. Carry signals to the CNS from receptors that sense various factors of the environment.
- Body temperature
- Blood pressure
- Blood O2 and CO2 levels (and more)

Question 6

Motorneurons

Answer 6

efferent neurons –> nerve cell forming part of a pathway along which impulses pass from the brain or spinal cord to a muscle or gland. Carry information from the CNS to the muscles and which tell muscles to contract or relax.
When a muscle is required to contract, an electrical impulse is emitted from the central nervous system. The electrical impulse, or action potential, begins at the brain and is transmitted via the spinal cord and by nerve cells called motor neurons.

Question 7

what do the number of muscle fibers per motorneuron indicate? (innervation ratio)

Answer 7

A large number of muscle fibers per motoneuron allows a single motoneuron to cause the muscle to generate large forces.
A smaller number of muscle fibers per motoneuron gives small forces but great precision.
The number of muscle fibers stimulated by one motoneuron is called the innervation ratio.

Question 8

All-or-nothing response

Answer 8

When the motor unit is innervated by the motoneuron all of its muscle fibers contract at once. This is called the all-or-nothing response (all of the muscle fibers attached to one motoneuron are either relaxed or contracted).

Question 9

slow twitch muscle fibers –> type 1

Answer 9

slow twitch motor units consist of mainly type I (slow twitch) muscle fibers and have fairly slow neurotransmission speeds and small muscle forces. Maintain contractions for a long time, as they are fatigue resistant

Sometimes referred to as “Red”. have more mitochondria, store oxygen in myoglobin, rely on aerobic metabolism, have a greater capillary to volume ratio and are associated with endurance exercise / activity; these produce ATP more slowly.

Question 10

Fast twitch –> type 2a

Answer 10

Also known as intermediate muscle fibers, are a mix of type I and type 2b, with comparable tension. Able to use both aerobic and anaerobic systems, these fibers have a higher oxidative capacity and fatigue more slowly than type 2b.

Question 11

Fast twitch –> type 2b

Answer 11

The largest fibres, called into action when all-out effort is required (fight or flight). They contract many times faster than slow-twitch fibres and with much greater force, but they fatigue quickly. Suited to speed, strength and power type activities.

Question 12

Myofibril

Answer 12

a cylindrical organelle running the length of the muscle fibre, containing actin and myosin filaments.

Question 13

Sarcomere

Answer 13

the functional unit of the myofibril, divided into I, A and H bands

Question 14

Actin

Answer 14

a thin, contractile protein filament, containing “active” or “binding” sites. It slides past myosin casing contractions.

Question 15

Myosin

Answer 15

a thick, contractile protein filament, with protrusions known as Myosin Heads. Pulls action filaments towards one another by means of cross bridges.

Question 16

Tropomyosin

Answer 16

an actin-binding protein which regulates muscle contraction.

Question 17

Troponin

Answer 17

a complex of three proteins, attached to Tropomyosin.

Question 18

Z line

Answer 18

separates each sarcomere. It provides an anchor for protein and also anchors the actin filaments to the ends of the sarcomere.

Question 19

M line

Answer 19

is the center of the A band and it is where adjacent myosin filaments anchor to each other.

Question 20

H Zone

Answer 20

is the center of the sarcomere and has only myosin filaments.

Question 21

A bands

Answer 21

are also known as dark bands and have both actin and myosin microfilaments.

Question 22

I bands

Answer 22

are also known as light bands and have only actin microfilaments.

Question 23

Isotonic contraction (concentric and eccentric contractions)

Answer 23

an increase in tension (load) results in changes in skeletal muscle length. Broken down into concentric and eccentric contractions.
- Concentric contraction: it is the shortening contraction which typically occurs against gravity
- Eccentric contraction: it is a lengthening contraction which typically occurs with gravity.

Question 24

Isometric contractions

Answer 24

in general in this form of contraction the muscle length remains constant. It occurs when muscle force balances resistance and no joint movement occurs.
It is the joint angle that remains constant because there are internal movement processes that take place during muscle contraction that make it virtually impossible for the fibres to remain the same length.

Question 25

Isokinetic contractions

Answer 25

the term is used in two contexts. As a specific muscle contraction and 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.

Question 26

reciprocal inhibition

Answer 26

can be defined as: a neuromuscular reflex that inhibits muscles during movement OR the relaxation of muscles on one side of a joint to accommodate contraction on the other side.
When we talk about reciprocal inhibition we want to consider the agonist muscle and antagonist muscle.
Agonist: a muscle whose contraction moves a part of the body directly.
Antagonist: a muscle whose action counteracts that of another specified muscle

Question 27

DOMS in relation to eccentric and concentric

Answer 27

DELAYED ONSET MUSCLE SORENESS. 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.
Delayed Onset of Muscle Soreness (DOMS)
tends to occur as soon as 6-8 hours
post-exercise and peaks around the 48 hour
mark.
Lower body exercise tends to produce
more inhibiting and memorable DOMS,
however, they can occur anywhere on
the body that has recently been
exposed to unfamiliar or intense physical
activity.
DOMS results primarily from eccentric muscle
action and is associated with structural muscle
damage, inflammatory reactions in the muscle, overstretching and overtraining.

Question 28

Force

Answer 28

force equals mass times acceleration and is a vector quantity (direction). Force is usually measured in Newtons (N).

Question 29

Speed

Answer 29

distance moved ina given time. The rate of change of distance and is a scalar quantity. Speed (ms-1) = Distance (m) / Time (s).

Question 30

Velocity

Answer 30

the speed of a body in a specific direction and is the rate of change of displacement. Velocity (m/s) = Displacement (m) / Time (s). Linearly it will correlate with speed.

Question 31

Displacement

Answer 31

the change in a position of an object in a direction. Different between an objects final position an dits starting position.

Question 32

momentum

Answer 32

the measure of an object’s motion and is calculated by multiplying the object’s mass bits velocity. Because momentum is calculated using velocity, it is a vector. Momentum (kg.m/s) = Mass (kg) x Velocity (m/s)

Question 33

impulse

Answer 33

impulse is force multiplied by time (actually it’s the sum of net force or the force that influences acceleration, multiplied by time over phase of interest) and is sometimes calculated by taking the area under the force time curve. It is typically reported in newton-seconds (Ns).

Question 34

acceleration

Answer 34

the rate at which a body changes its velocity and similarly to velocity, it is a vector quantity. It is measured in meters per second per second (meters per second squared – ms-2). Acceleration (ms-2) = Vf - Vi (m/s) / time (s).