the nervous system Flashcards
nervous system consists of
spinal cord. brain, and all peripheral nerves
primary functions of CNS
1) sensory input
2) interpretation
3) motor output
sensory input
detect changes to body’s internal and external environment = stimuli
also known as afferent nerves
interpretation
sensory input converted into electrical signals called ‘nervous impulses’ that are transmitted back to brain. here the signals are consolidated to created sensations, thoughts, decisions and even memories.
motor output
nervous system responds stimuli by sending signals to muscles and/or glands. instruct the muscle or gland to increase or decrease activity. signals which produce movement are called ‘motor signals’ or ‘efferents’
PNS (Peripheral Nervous System)
31 pairs of nerves outside spinal cord and brain
branch off spinal cord through tiny holes in vertebrae called ‘foramen’
junction at which one nerve joins another is referred to as a ‘synapse’
PNS can be further can be divided further into the
Somatic Nervous System
Autonomic Nervous System
Somatic Nervous System
- Primarily associated with efferent or motor activity
- Largely responsible for controlling voluntary activity
- The nerves that form the somatic nervous system are called ‘motor neurons’
- Under conscious control but does rely on sensory feedback from external sensory receptors
- These receptors are:
- Nociceptors = pain stimulus
- Thermoreceptors = heat/temperature stimulus
- Mechanoreceptors = touch, feel, pressure stimulus
- Proprioceptors = motion, position and tension stimulus
autonomic nervous system
- Primarily concerned with involuntary processes
- Regulates hormone secretion from glands
- Controls organ activity
- Regulates HR and blood pressure
- Controls body temperature
- Regulates digestion
- Contracts/relaxes smooth and cardiac muscle
- This system relies on feedback from internal sensory organs
- These organs are:
- Baroreceptors = pressure within organs and vessels
- Osmoreceptors = concentration of water in blood
- Chemoreceptors = concentration of gasses in blood
- Proprioceptors = pressure and deformation in muscle-reflexes only
- Thermoreceptors = temperature of internal environment
sympathetic and parasympathetic
autonomic system can be further divided into sympathetic and parasympathetic systems
sympathetic division
generally sends stimulatory impulses to target organs in an attempt to speed them up
for eg, during exercise the heart receives sympathetic stimulation from autonomic nervous system to increase rate at which it contracts
parasympathetic sub-system
typically concerned with inhibitory actions to reduce activity of the target organ
eg, arteries supplying the active tissues during exercise receive a parasympathetic stimulation which causes their smooth muscle lining to relax, thus enabling them to stretch, or dilate, under increased pressure
neurotransmitters
nerves communicate by releasing chemical messengers called neurotransmitters
they diffuse across nerve junction/synapses to stimulate next nerve or cell
electrical signals travel along the length of a nerve until they reach the synapse. this is where neurotransmitters are released and signal becomes chemical.
when neurotransmitters reach post synaptic membrane of nerve, it becomes electrical again.
some common neurotransmitters
acetylcholine - muscle cell communication
dopamine - brain cell communication
adrenaline - varied roles throughout the body
noradrenaline - varied roles throughout the body
parasympathetic nerves within the autonomic nervous system are entirely responsible for
suppressive and inhibitory activities like slowing heart rate, relaxing smooth muscle tissue and reducing glandular activity
parasympathetic nerves within the autonomic nervous systems release
the neurotransmitter ‘acetylcholine’ from their terminal end.
this neurotransmitter is therefore used to suppress and inhibit the activity of the target organs/cells
also in some systems, acetylcholine is used to excite cells
baroreceptors
tiny pressure receptors located inside larger arteries, including aorta, which provide feedback to CNS about changes in arterial pressure.
so, when HR increases so does the arterial blood volume, which then causes blood pressure to rise. this pressure is detected by baroreceptors and fed back to the CNS.
baroreceptors and parasympathetic response
when a pressure increase is detected by the baroreceptors and fed back to the CNS, it exerts a parasympathetic response on the arteries supplying the active tissues. causes them to relax and widen.
vasodilation
large volume of elastin within the artery wall means artery is able to stretch or dilate
it is a passive stretching response that occurs because of the increased pressure
vasoconstriction
simultaneously to parasympathetic response, a sympathetic response is exerted on arteries supplying the non-active tissue, which cause them to narrow or constrict.
vasoconstriction excites the smooth muscle tissue that lines the arterial wall and causes immediate reduction in the diameter of the arteries lumen; this narrowing process reduces blood flow and diverts it to the dilated arteries where it is needed.
primary purpose of both vasodilation and vasoconstriction
to divert more blood towards the active tissues.
components of a neuron
cell body dendrites axon nodes of ranvier myelin sheath terminal end
cell body
this is the brain of the cell and contains both the nucleus and DNA. regulates all cell activity
dendrites
tree-like structures that receive information from the terminal end of adjacent nerves.
the dendrites relay this information to the cell body, which is subsequently interpreted and transmitted along the axon towards the terminal end.
axon
the elongated fibre that transmits information away from the cell body towards terminal end.
nodes of ranvier
these are the non-insulated spaces along the nerve’s axon, which allow electrical signals to rapidly jump from one myelin to the next, thus speeding up the rate at which impulses travel along the nerve. this process is known as depolarisation an repolarisation.
the nodes of ranvier, which expose the axon, also allow nutrients and waste products to enter the nerve cells.
myelin sheath
myelin is the fatty sheath that provides the protective and insulating case surrounding the nerve’s axon; the myelin sheath enables impulses to travel along the nerve at lightening speeds and with little resistance
terminal end
sometimes called and ‘axon terminal’ or ‘synaptic terminal’, the terminal end contains an extensive range of sacs (vesicles) that store and release a variety of neurotransmitters essential for nerve function.
reflex arcs
exist between the sensory organs in PNS, the peripheral nerves and the CNS.
arcs serve to provide rapid and involuntary activation of motor neurons, often with the goal of protecting the bodily tissues from damage, whether this is perceived or actual.
within in a reflex arc, the afferent sensory neurons feedback stimuli to the CNS about the nature and intensity of the stimulus.
more specifically it is fed back to the grey matter in the spinal cord by the afferent nerves on the dorsal root of the cord.
the grey matter is capable of initiating the activation of motor neurons of its own volition (without consulting the brain) = reflex.
the grey matter of the spinal cord
stimulates the efferent motor neurons via the ventral root of the spinal cord, which results in the contraction of one or more skeletal muscles and the onset of the required movement.
interneurons
situated within the grey matter and between the afferent and efferent nerves
relay sensory information to different levels of the spinal cord.
proprioceptors
specialised sensory organs that relay information to the spinal cord via the nervous system.
muscle spindles
run parallel to, a detect changes in muscle fibre length.
occasionally referred to as ‘intrafusal muscle fibres’, and are primarily responsible for protecting the functional unit of the muscle fibre (sarcomere).
When the muscle spindles detect that the sarcomere is at risk of injury or damage, they protect fibre my initiating stretch reflex.
golgi tendon organs
located in musculo-tendinous junction (where tendon and muscle join) and detect tension and deformation of the tendinous tissue. when the threat of strain in the tendon is high, these fibres overrride and inhibit any muscle action in order to relax the muscle and protect the tendon.
the stretch/myotatic reflex
when the stress on the fibres is perceived by the muscle spindles to be dangerously high, they inform the CNS, which in turn instructs the muscle to contract through a reflex arc.
by slowly and gradually easing into a stretch, the onset of the stretch reflex can be delayed and a greater range of movement can be achieved.
autogenic inhibition
when the stretch reflex is applied to the muscle for a sustained period of time, tension is also created at the musculo-tendinous junction. this is because the stretch reflex is attempting to shorten the muscle, while the stretch technique is attempting to lengthen the muscle.
the golgi tendon organs recognise the increased strain in the tendinous area and override the muscle spindle activity by inhibiting the stretch reflex.
the primary purpose of this is to protect the tendon from strain. this process is occasionally referred to as the ‘inverse stretch reflex’
reciprocal innervation
sometimes called ‘reciprocal inhibition’.
this process provides the foundation of how muscles are able to communicate at the same joint to create an opposite movement.
Basically, for every muscle that contracts, the antagonist must relax.
at the same time as an excitatory stimulus is delivered to the agonist, an inhibitory action is delivered to the antagonist to ensure the muscle action is not impeded. This mechanism can be exploited and manipulated when performing active and PNF style stretches.
balance
ability to maintain a stable body position
speed
the ability to move a greater distance in a shorter time
agility
the ability to maintain speed whilst changing direction
coordination
the ability to produce smooth and accurate movement patterns
reaction time
the time between the sensory input and the initiation of the desired action (stimulus-response)
kinaesthetic/spatial awareness
the ability to specifically identify where the body is (or a segment of the body) during movement.
power
strength x speed; the ability to exert a maximum force in the shortest time.
common skill training equipment
stability discs and balls BOSU (both sides) maker cones micro hurdles foot ladders kettlebells wobble boards
methods of developing motor skills
> reducing the speed of an activity
whole-part-whole
layering
reducing the speed of an activity
reducing the speed of an activity or movement and rehearsing it in slow-time can help to form or consolidate the new motor programme. Once the programme has been created and the participant is able to complete the skill correctly, the speed of execution can then be progressed.
whole-part-whole
a technique that involves breaking a particular skill down into smaller and less complex components.
essential when working with novice or deconditioned participants.
useful for when rehearsing drills that involve multiple activities
- allows participants to master the fundamentals and reduces their potential for error and/or injury.
layering
the opposite of whole-part-whole
involves the addition of new skills to the activity in order to make it more complex and demanding.
eg = a depth jump at the beginning of a plyometric activity to increase the eccentric workload on the lower body muscles, or adding a multidirectional sprint to the end of a ladder drill to extend the duration and physical demands of the activity.
neural adaptations to skill training
- increased strength of neural connections = stronger muscle contractions and greater control during movement
- formation of new synapses = creates more neural pathways to connect to muscles and allow more muscle fibres to be recruited = improve the control and forced produced by muscle.
- improved intra and inter-muscular coordination = enhancing the application of force created by motor units.
- increased twitch frequency = enhances the potential to achieve tetanus within motor units = improve speed of muscle contractions
- increased synchronisation of motor units, enabling muscle fibres to fire simultaneously and to achieve stronger muscle contractions.
- common movement patterns become automated and more reflexive, which frees up the conscious mind for other tasks
- improved balance due to improved efficiency of proprioceptors
popular plyometric exercises
> jumping lunges > lateral lunge-jumps > clap press-ups > bounding > tuck jumps > depth jumps > frog squats > hopping
phases of plyometric exercises
phase 1 = eccentric muscle action
phase 2 = transition
phase 3 = the concentric muscle action
eccentric muscle action
characterised by rapid lengthening/stretching of the active muscle(s) and usually occurs during a landing activity.
active muscles are employed to decelerate movement and absorb shock; this generates elastic energy in the SEC. simultaneously, the muscle moves towards its end range, the muscle spindles are excited = initiation of stretch reflex.
transition
/support phase
crucial to the amount of force that will be generated in phase 3.
can be characterised as the shock absorption and or energy wastage phase.
goal of plyometric exercises is to reduce the time spent in this phase, maximising energy loss. if too much time spent in this phase, the energy generated from phase 1 will dissipate as heat.
the concentric muscle action
where all energy generated and stored in previous two phases is unleased.
Each generated from the stretch reflex SEC and PEC is combined with the voluntary muscle action to release as much force as possible. The sum of these four mechanisms generates far more force than any isolated muscle contraction, especially when the transition period is kept to a minimum.
stretch shortening cycle
fundamental to plyometric exercise
assists the voluntary activation of muscle to create a rapid and powerful muscular contraction.
purpose is to enhance the performance of the concentric contraction = more explosive and powerful.
plyometric training
fast and ballistic movements that are typically performed milliseconds after a rapid pre-stretching action.
eg - performing a vertical jump, the jumper would bend their knees immediately prior to activating the hip, knee and ankle extensors.
afferent and efferent nerves
within the PNS there are two types of nerve cells, afferent and efferent
afferent nerves
- responsible for carrying sensory information
- feedback information from the various receptors throughout the body
- deliver signals to the dorsal or posterior surface of the spinal cord
- provide sensory feedback to the CNS about stability of body’s environment
efferent nerves
- transmit motor information
- transmit info from CNS to the muscles, glands and organs
- deliver motor information from the ventral or anterior surface of the spinal cord to the target organs and muscles
- transmit the CNS’s response from the interpretation of stimuli (from afferent neurons)
structure/function of a neuron
- carry electrical and chemical signals to and from every living cell in body
- neurons connect to each other by synapse, it is here that the neurotransmitter releases and is switched from an electrical to chemical signal
- in an efferent nerve, the dendrites act as extensions of the cell body and receive incoming chemical signals from adjacent nerves, creating an electrochemical signal
- this signal (action potential) travels along axon, this process is repeated with next nerve until it reaches its destination
- axon is protected and insulated by the myelin sheath
axon
elongated fibre that transmits information away from the cell body towards terminal branches
myelin sheath
- helps speed up the rate the action potential moves along the neuron
- composed largely of fat cells
- has dedicated gaps (nodes of ranvier) which can generate impulses and can cause the impulse to jump from one segment to the next.
- this jumping action accelerates the rate at which these electrical messages travel along the axon of the nerve by reducing impedance
The sodium-potassium pump
- the electrical signals of neurons are initiated and maintained by a transport system called the sodium-potassium pump.
- serves to move the sodium ions outside the nerve cell and potassium ions into the nerve cell
- this exchange of sodium and potassium creates and electrical charge which is used to keep the electrical signal moving along the nerves.
- this process depends on ATP for energy
motor skill training
- places a lot of strain on neuromuscular system and so should always be completed when person is rested.
- key to developing motor fitness is frequent repetition of required action so training sessions should initially be structured with short duration and high frequency
- whilst performing motor training skills the participant needs feedback on the quality - could be mirror or video recording. verbal feedback as well.
The mechanisms of the Stretch Shortening Cycle
- elastic energy generated from the muscles’ fascia during the prestretch (parallel elastic components)
- the series of elastic components are considered to be the primary mechanism for generating power in the plyometric exercise and are primarily composed of the elastic properties within the muscular and tendinous tissue
- the stretch reflex that is initiated by the muscle spindles when the agonist muscles are loaded and stretched. this involuntary muscle contraction assists athletes with the voluntary muscle contraction that occurs during the post-stretch phase of the movement
- the voluntary contraction of the active muscles following the rapid pre-stretch generates considerable force and power, especially when combined with the above three mechanisms
motor programme
the information that is stored within the motor cortex of the brain when an electrical impulse is sent to a muscle or group of muscles to produce a movement
how repetition makes movement more efficient
- with each action the nervous system responds by increasing the number of synapses between adjacent nerves, thus increasing number of pathways an impulse can reach the active muscles = hard wiring.
- if the movement pattern is anything less than perfect, greater repetition will reinforce incorrect and inefficient motor programmes making it more difficult to correct later.
- it is said that it can take over 2000 high quality repetitions of an action before an efficient motor programme can be formed.
single leg balance (balance) progression, regression and equipment
progression = BOSU or another unstable surface
add in catching of medicine ball
regression = use support from stable object or person
reduce time held in the position
equipment = ground, stability disc, medicine ball, BOSU
single leg squat (movement) progression, regression and equipment
progression = BOSU ball or another unstable surface
increase range of reach and lever length add in catching of medicine ball
increase resistance with dbs
slow down tempo
perform from a step to increase range
regression = use support from stable object or person
increase the speed of the movement
decrease resistance
equipment = ground, stability disc, medicine ball, leg weights, BOSU
single leg balance reach (stability) progression, regression and equipment
progression = BOSU ball or another unstable surface
increase range of reach and lever length add in catching of medicine ball
regression = use support from stable object or person
reduce time held in the position
only reach in one plane of movement eg sagital
equipment = ground, stability disc, medicine ball, leg weights, BOSU
step up to balance (movement) progression, regression, equipment
progression = BOSU ball or another unstable surface
increase range of reach and lever length add in catching of medicine ball
increase resistance with dbs
slow down tempo
perform from a step to increase range
perform in different planes of movement
increase the step height
regression = use support from stable person or object
equipment = ground, stability disc, medicine ball, leg weights, BOSU, step
