muscle system Flashcards
function of muscle
- contract transiently and move the skeleton or fluids
- maintain a state of tone for support
two types of muscle
striated and smooth
striated muscle
striations running across the fibre, due to the arrangement of fibres and the contractile proteins contained
where is striated muscle found
skeleton ( support and movement) and cardiac muscle (rhythmic contraction)
smooth muscle
no clear structure - plain
where is smooth muscle found
around hollow organs
connective tissue sheet
external to epimysium and holds muscles together and separates them into functional groups - muscular fascia
layers of connective tissue coverings
epimysium, perimysium, endomysium
epimysium (outer layer)
surrounds a whole muscle
perimysium (middle layer)
denser ct surrounding a group of muscle fibres, allowing transmission of tension
endomysium (inner layer)
loose CT with reticular fibres (network of nerves and blood vessels)
muscle fibres
elongated multinucleate cell, contain a large number of rod-like myofibrils
myofibrils
organised protein components, composed of bundles of myofilaments
types of muscle fibres
type I, IIa, IIb
type I
long distance, slow twitch, more resistant to fatigue
type 2A
middle distance, fast twitch oxidative
type 2B
sprints, fast twitch glycolytic
sarcomeres
highly ordered repeating units of myofilaments
T tubule
wrap around the myofibril underneath the membrane, release ions to SR (sarcoplasmic reticulum)
Sacroplasmic reticulum
channel along the full length of the fibril filled with calcium, signals contraction initiation of the sarcomere
contractile proteins (2 types)
thick and thin filament
thick filament
bundle of myosin molecules, ATPase activity
thin filament
two strands of f-actin with spaced Ca++ regulatory proteins: troponin and tropomyosin
cross-bridge cycling
interaction of thick and thin filaments which creates contraction, iniated by the release of Ca++ ions
sliding filament theory
- during contraction the I-band (thin) is reduced but the A-band doesn’t,
- associated with the two filaments sliding past each other
neuromuscular junction
motor end plate activates the muscle fibre by releasing a neurotransmitter - acetylcholine
function of nmj
synaptic vessels, contains neurotransmitter- acetylcholine
excitation- contraction coupling
Ca++ entry allows the actin to alter the position of troponin which enables an attachment to myosin heads
relaxation (how muscles relax)
Ca++ dissociates from troponin, and is transported back into the SR via the action of ARC app put, no binding sites remain so cannot make a cross-bridge connection
3 types of mechanics of movement
concentric, isometric, eccentric
length-tension relationship
full range of motion of a muscle where the greatest tension can be generated with optimal cross-bridge formations
concentric muscle contraction
force is generated when the muscle shortens (e.g: bicep curl)
isometric muscle contraction
force is generated with a change in muscle (eg: holding a heavy object)
eccentric muscle contraction
force is generated as the muscle is lengthened (eg: pushing down an object very slowly)
4 functions of muscle
excitability, contractility, extensibility and elasticity
excitability
ability of muscle to respond to stimuli
contractibility
ability of muscle to contract or shorten its size
extensibility
ability of muscle to stretch
elasticity
ability of muscles to return to original length after stretching
peristalsis
contraction of the colon and the GI tract down to the anus
thermogenesis
repetitive contractions of muscle to produce heat
process of peristalsis muscle movement
- inner circular muscles squeeze and expand in a synchronised way to push food through the intestines while the outer longitudinal muscles propel bolus forward.
- segmentation occurs in your digestive system, but only in the intestines
muscularis propria
circular and longitudinal muscles collectively
process of peristalsis segmentation
activates circular muscles in your intestines that contract to move food back and “churn” the chyme with digestive juices
process of circulation
Involuntary muscles contract and relax to regulate blood pressure. The muscles contract to also redirect blood to areas of the body where it is needed.
parts of a muscle
body, origin, insertion
avulsion fracture
when a muscle contracts quickly it can cause the tendon to pull of part of the bone. Common in paediatric pelvis’ with children playing lots of sports
colonic transit study
patients with chronic constipation will take radio-opaque capsule to see if they are expelled from the body after 5 days
symptoms of muscular dystrophy
frequent falls, difficulty rising from a sitting and lying position
cardiomyopathy
disease of the heart muscle, walls of the heart chambers have become stretched, thickened or stiff
first degree heart block
least severe, electrical signals slow down as they move from your atria to your ventricles
second degree heart block
electrical signals between your atria and ventricles can intermittently fail to conduct
third degree heart block
most severe could lead to a heart attack
what causes heart block?
coronary heart disease, congenital (present at birth), cardiomyopathy
pacemaker
sends out electrical impulses to regulate heart rhythm
fibromyalgia
pain all over the body
strengths of MRI
- provides better soft tissue contrast than CT
- can differentiate between fat, water, muscle and other soft tissue
- non-ionising radiation
weaknesses of MRI
- longer scan times
- problematic in patients with claustrophobia
- long waiting lists
IM
intramuscular
myositis
inflammation of muscular tissue
myoma
a tumour consisting of muscle tissue
myoplasty
surgical repair of a muscle
atrophy
decrease in size of organ or tissue
hypertrophy
excess of growth of muscle tissue
electromyography
used in diagnosing muscle pathologies
define a tissue and give an example (2)
a group of cells that work together to carry out a specific function. Eg: connective tissue
define disease (1)
any abnormal disturbance of the function or structure of the human body
name the 4 properties of muscle (4)
- excitability: the ability to respond to stimuli
- contractility: ability of muscle to contract or shorten its size
- extensibility: ability of muscle to stretch
- elasticity: ability of muscles to return to original length after stretching
describe the structure of a vertebral disc and explain what happens when a patient encounters a “slipped disc”
annulus fibrosus and nucleus pulposus
defect in structure of annulus fibrosus causes nucleus pulpous to protrude. can press on nerve root
what is the gold standard imaging modality for diagnosing cauda equina syndrome?
MRI
describe the process of atherosclerosis
- damage to arterial walls and build up of plaque
- caused by a stimuli such as high blood pressure
- when arterial wall is damaged, endothelial cells produce receptors
- white blood cells then stick to arterial wall, attracting substances such as cholesterol increasing the amount of plaque inside of the artery
- leading to a stenosis or occlusion of the artery
4 risk factors for atherosclerosis
high blood pressure, diet high in salt, stress and genetics
