Case 9 - muscle and movement Flashcards
features of skeletal muscle
connected to bone
striated
voluntary
high power
usually relaxed
features of cardiac muscle
heart
striated
involuntary
high power
pump (cyclic)
features of smooth muscle
hollow organs
smooth
involuntary
low power
usually contracted
neuromuscular junction diagram
neuromuscular junction diagram
what is in a sarcomere
a number of different proteins in highly organised structure
how does muscle contract
by overlapping the filaments
using energy derived from ATP hydrolysis to power this mechanism which is progressively shortening the distances
what is the thin filament
actin
what is the thick filament
myosin
where is tropomyosin normally sat
over the binding sites for myosin on actin
what has to happen in order fr the myosin to bind to the myosin binding site on actin
the binding site has to be exposed. when there is little Ca2+ or none, tropomyosin moves down and covers the binding sites. means that the actin and myosin can’t interact and bind to each other therefore giving no muscle contraction
what is the troponin complex
series of regulatory proteins and in the presence of calcium, they help to move that tropomyosin out of the myosin binding site and allows the actin and myosin to interact. you then get ATP hydrolysis that powers the whole process. effectively makes the muscle shorter
striated muscle contraction series of events
- ATP binds to the myosin head causing the dissociated of the actin-myosin complex
- ATP is hydrolysed, causing myosin heads to return to their resting connotation
- a cross bridge forms and the myosin head binds to a new position on actin
- phosphate is released… myosin heads change conformation resulting in the power stroke. the filaments slide past each other
- ADP is released
what happens when there are high levels of calcium
you get contraction
diagram with anatomy concerning excitation-contraction coupling
what is the plasma membrane
the sarcolemma
what are there lots of in the muscle cell
myofibrils
what do the invaginations of the plasma membrane form
transverse tubules
what interacts with the transverse tubule
the sarcoplasmic reticulum cisterns
where does the action potential go
goes along the sarcolemma and finds its way down into the T tubules and the T tubule is running very close to the SR. t
where is calcium stored
the SR.
when the muscle is relaxed, the Ca2+ will be locked up inside the SR
when the cells contract, Ca2+ will be released
when do we get release of calcium
when a wave of depolarisation passes through the T tubule
what does the twitch force depend on
how much calcium is released. bigger contraction when more calcium is released
what are the two types of contraction
isometric
isotonic
what is isometric contraction
a constant length and doesn’t actually shorten
what is isotonic contraction
a constant load
what does isotonic muscle contraction produce
limb movement without change in muscle tension, whereas isometric muscle contraction produced muscle tension without a change in limb movement. most physical activities involve a combination of both forms of muscle contraction, although one form usually predominates
more on isometric contraction
contraction is stronger the closer the muscle initial length is to the optimum length
a muscle contracts but the joint is controls does not move
more on isotonic contraction
contraction is faster the closer the muscle initial length is to the optimum length
a muscle contracts and the joint angle it controls increases and decreases while the muscle either shortens or lengthens
what is a muscle unit
muscle fibres innervated by a single motor neurone
what is a motor unit
muscle unit plus its motor neurone
what is a motor neurone pool
collection of neurones innervating a single muscle
what is involved in fine control
few muscle fibres per motor unit
what is involved in coarse control
any muscle fibres per motor unit
how many motor neurones control a muscle
typically about 100
what are the features of type 1 muscle
oxidative slow, red
slow myosin response time
moderate rate of Ca2+ pump transport
moderate diameter
high oxidative capacity
moderate glycolytic capacity
reistant to fatigue
what are the features of type 2B muscle - 7
glycolytic fast, white
fastest myosin response time
high Ca2+ pump transport rate
large diameter
low oxidative capacity
high glycolytic capacity
non-resistant to fatigue
what are the features of type 2A muscles - 7
glycolytic, fast, red
fast myosin response time
high Ca2+ pump transport rate
small diameter
very high oxidative capacity
high glycolytic capacity
resistant to fatigue
which muscle type is good for long distance running and why
type 1 fibres are slow and oxidative and tend to rely on aerobic respiration to generate most of their force - long distance run at low speed
which fibres fatigue slower than 2B
2A but generate a decent amount of tension
what are 2B designed to do
give you high energy. relying on glycolysis anaerobic respiration to give out most of their power.
what are the two mechanisms to increase the amount of force
recruitment of motor units
firing rate of motor units (shortening the time between action potentials and the contractions sort of add together and the calcium is never fully mopped up by the SR)
what is the sequence of recruitment in the gradation of muscle force
S->FR->FF
what are the large motor unit properties
motor neurone: large, fast conduction, hard to excite
Muscle fibres: many, type 2 (large, fast glycolytic)
Activity: recruited if a strong contraction is required, usually inactive
what are the small motor unit properties
motor neurone; small, slow conduction, easy to excite
Muscle fibres: few, type 1 (small, slow, oxidative)
Activity: first to be recruited, frequently active
detailed stretch reflex diagram
LMN muscle strength
weak
what type of paralysis do you get with LMN lesion and why
flaccid - effectively damaged the wiring between the muscle and the spinal cord; cant get a message from the spinal cord to the muscle
what is the muscle tone if you have a LMN lesion
hypotonia
what is the type of reflex if there is a LMN lesion
hyporeflexia
muscle strength in UMN lesion
weakness
what type of paralysis do you get in UMN lesion
you get spasticity because the wiring is still there form the muscle unlike in an LMN lesion: can’t get the message from the motor cortex to the spinal cord. you get sensitisation of the lower motor neurone pools so that they’re responding in the absence of innovation from the motor cortex. that is why you get spastic paralysis
what type of muscle tone is there in UMN lesion
hypertonia - thanks to sensitisation to lower motor pools
what sort of reflexes do you get. in UMN lesion
hyperreflexia
what is Babinski sign
may show a problem in the corticospinal tract. CST is a neural pathway that goes from your brain to spinal cord and helps control your movements. evaluate neuro only in patients above age of 2.
the essential phenomenon appears to be recruitment of the extensor hallicus Longus, which consequent overpowering of the toe flexors. the movements of the other joints remain the same
how what happens when the corticospinal tract is not functioning
The corticospinal tract influences the segmental reflex in the spinal cord. When the corticospinal tract is not functioning properly, the result is that the receptive field of the normal toe extensor reflex enlarges at the expense of the receptive field for toe flexion. Toe extension is consequently elicited from what is normally the receptive field for toe flexion.
what is the plantar reflex
a nociceptive segmentaal spinal reflex that serves the purpose of protecting the sole of the foot
in what conditions has the extensor reflex been observed
hemorrhage, brain and spinal cord tumors, and multiple sclerosis, and in abnormal metabolic states such as hypoglycemia, hypoxia, and anesthesia.[2]
