SEHS TOPIC 4 Flashcards
What are the main two parts of the nervous system?
The central nervous system and the peripheral nervous system.
CNS features
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.
Myelin
Each nerve has a protective outer layer called myelin. Myelin insulates the nerve and helps the message get through.
Peripheral nervous system
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).
Sensory neurons
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)
Motorneurons
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.
what do the number of muscle fibers per motorneuron indicate? (innervation ratio)
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.
All-or-nothing response
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).
slow twitch muscle fibers –> type 1
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.
Fast twitch –> type 2a
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.
Fast twitch –> type 2b
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.
Myofibril
a cylindrical organelle running the length of the muscle fibre, containing actin and myosin filaments.
Sarcomere
the functional unit of the myofibril, divided into I, A and H bands
Actin
a thin, contractile protein filament, containing “active” or “binding” sites. It slides past myosin casing contractions.
Myosin
a thick, contractile protein filament, with protrusions known as Myosin Heads. Pulls action filaments towards one another by means of cross bridges.
Tropomyosin
an actin-binding protein which regulates muscle contraction.
Troponin
a complex of three proteins, attached to Tropomyosin.
Z line
separates each sarcomere. It provides an anchor for protein and also anchors the actin filaments to the ends of the sarcomere.
M line
is the center of the A band and it is where adjacent myosin filaments anchor to each other.
H Zone
is the center of the sarcomere and has only myosin filaments.
A bands
are also known as dark bands and have both actin and myosin microfilaments.
I bands
are also known as light bands and have only actin microfilaments.
Isotonic contraction (concentric and eccentric contractions)
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.
Isometric contractions
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.
Isokinetic contractions
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.
reciprocal inhibition
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
DOMS in relation to eccentric and concentric
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.
Force
force equals mass times acceleration and is a vector quantity (direction). Force is usually measured in Newtons (N).
Speed
distance moved ina given time. The rate of change of distance and is a scalar quantity. Speed (ms-1) = Distance (m) / Time (s).
Velocity
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.
Displacement
the change in a position of an object in a direction. Different between an objects final position an dits starting position.
momentum
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)
impulse
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).
acceleration
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). (Change in velocity/ time)
flexion
BENDING. Angle between bones decreases
extension
Opposite of flexion, angle between the bones of a joint increases
abduction
bone moves away from midline of body.
adduction
movement of a bone toward the midline of the body
pronation
opposite movement. palm faces backward.
supination
palm faces forward
elevation
upward movement of bone
depression
opposite of elevation. downward movement of bone
rotation
bone rotates around its longitudinal axis
circumduction
movement of limb in a circular motion
dorsiflexion
bending of ankle so that toes are lifted towards the knee
plantarflexion
bending ankle when heel is lifted, tip toes
eversion
sole of the foot outward
inversion
sole of foot inward
