MST Week 2 (sports Injury) Flashcards
Define neuromuscular
Affecting or characteristic of both neural and muscular tissue
What are the signs of myasthenia gravis
Complaints of muscle weakness in an otherwise healthy and strong patient
Ptosis (droopy upper eyelid)
Cannot prolong muscle contraction
Symptoms progressing
What is myasthenia gravis
Disorder of neuromuscular transmission
Production of autoantibodies directed against the nicotinic AChR
Prevalence of about 1 in 10-20,000
Women affected about twice as often as men
Peak onset in women 2-3 decades, peak in men 5-6 decades
Key properties of synapses
Unidirectional
Irreversible delay
Chemical
How does an action potential in the motor neurone lead to contraction of the muscle fibre
1) action potential in motor neurone arrives at axon terminal
2) terminal membrane depolarises, volatge gated calcium channels open
3) calcium mediated exocytosis of acetylcholine (ACh) into extracellular space
4) interaction of ACh with nicotinic acetylcholine receptor
5) influx of sodium ions and efflux of potassium ions from muscle cell via nAChRs, generation of receptor potentials
6) if RGPs are sufficient to pass thereshold an action potential is generated
7) action potential propagates through muscle, which leads to release of calcium ions from sarcoplasmic reticulum leading to contraction of muscle
How does action potential lead to end plate potential
Open Ca2+ ion channel Ca2+ entry Exocytosis of ACh ACh binds to nicotinic receptor Conformational change Na+ influx and K+ efflux Depolarisation
End plate potential
How does an end plate potential lead to a contraction
Propagated action potential
Spreads in muscle
Contraction
How is myasthenia gravis treated
Increase the ACh levels at the neuromuscular junction.
What clinical use does neuromuscular blockade serve
Surgery
Prevents muscle contractions
Maintain muscle relaxation / paralysis without deep general anaesthesia
Cosmetic surgery
What does the patient experience during neuromuscular blockade
Slow methodical paralysis in skeletal muscle
Extrinsic muscles of eye first, then the small muscles of the face and hands followed by muscles of pharynx, respiratory muscles last
Individuals still experience pain
How can we block neuromuscular transmission
1) prevent synthesis (block Ch uptake)
2) prevent release (exocytosis)
3) block receptor activation (nicotinic receptor antagonists)
4) increase reuptake / inactivation
Clinical uses of Botox
Cervical dystonia - neuromuscular movement disorder involving the head and neck
Blepharospasm - involuntary contraction of the eye muscles
Severe primary axillary hyperhidrosis (excessive sweating)
What are the 2 classes of neuromuscular blockers
1) non-depolarising: nACh-R antagonists
2) depolarising nACh-R agonists
Features of non-depolarising blockers
- Occupy without stimulating post-synaptic nACh receptors
- additive effect of similar drugs
- block is competitive
- onset of action 3-5 min, duration typically 30+ min
- block not preceded by stimulation
Features of non-depolarising blockers
- during block, high freq stimulation causes tetanus with duration only slightly longer than a twitch
- block antagonised by agents that depolaris muscle membrane
- block antagonised by drugs that increase ACh release
- block reversed by anticholinesterases
How do depolarising blockers work
Persistent activation of nACh-R causes inactivation of voltage - gated Na+ channels ie can no longer open in response to brief depolarisation
Rapid onset of action (<1min), very short duration
Features of depolarising blockers
- Block preceded by muscle twitches
- during block tension of tetanus is depressed but does not fade
- AChEs do not reverse block
- block summaries with other depolarising drugs
- drugs with weak curare like action antagonise block
What are direct / contact acute injuries
Caused by an external blow or force
What is an indirect / non contact acute injury
The actual injury can occur some distance from the impact site
Eg FOOSH can result in shoulder dislocation
The injury doesn’t result from physical contact with an object or person but from internal forces built up by the actions of the performer
What is an overuse injury
Exercise applies stress to the body. Your body adapts by thickening and strengthening the various tissues involved hence muscles get stronger, firmer, and sometimes larger
However if exercise is applied in a way that adaptation doesn’t occur the overload can cause microscopic injuries leading to inflammation
What are overuse injuries caused by
Training errors, improper techniques, excessive training, inadequate rest, muscle weakness
Ligament sprain grading
Grade 1: microscopic tearing, minimal swelling, no joint instability, full / partial weight bearing
Grade 2: partial tearing, moderate / severe swelling, mild / moderate joint instability and unable to weight bear
Grade 3: complete rupture, severe swelling, moderate / severe joint instability, unable to weight bear
To help recovery you shoudl avoid HARM
Heat- can increase blood flow whic may increase swelling
Alcohol- can increase bleeding and swelling to injured area
Running - or other forms of exercise
Massage- can cause more swelling or bleeding
Define nutrition
The provision of nourishment to cells, tissues, organs, systems and the body as a whole
How food influences our body function and health
Includes dietary guidelines, food composition, and the roles that various nutrients have in maintaining health
Define sports nutrition
How food and nutrients influence athletic performance in different sports- use of ergogenic aids
Define exercise nutrition
How nutrition modifies the physiological and metabolic responses to exercise in a variety of populations
What is sub-maximal exercise
Can be sustained for durations of between 30 and 180 min before fatigue
Because the rate of muscle ATP re-synthesis required is relatively low carbohydrate, and fat can both contribute to ATP re-synthesis ie there is a metabolic fuel integration
Carbohydrate ingestion during exercise
CHO ingestion immediately before and during exercise delayed the onset of fatigue by sparing muscle glycogen stores during exercise
How much carbohydrates should be ingested
Ingestion of 5-6% CHO solutions in serial feedings every 15-20 mins could be used without impairing emptying from the stomach
A 5-6% CHO solution will also ensure fluid balance is maintained, particularly important when exercising in the heat
Why should carbohydrate intake during recovery be increased
It accelerates skeletal muscle and liver glycogen depletion and improves the capacity for repeated exercise
How much CHO post exercise?
1.2g/kg body mass / hour for the first 6 hours post exercise (ie 84g per hour for a 70kg person)
What is groin strain
When someone pulls / tears one of the proximal attachments of an adductor / flexor
Which serious circulatory problems are most likely to affect the lower limb
Arterial insufficiency
Venous insufficiency
Lymphoedema
