Skeletal Muscle Physiology 2 Flashcards
4 causes of impaired skeletal muscle
intrinsic disease of muscle, problem with NMJ, problem with lower motor neurons, problem with upper motor neurons
name the 2 factors influencing skeletal muscle tension?
number of muscle fibres contracting within the muscle, tension developed by each contracting muscle fibre
what allows the simultaneous contraction of muscle fibres
motor units
what would make contraction of muscle fibres stronger?
stimulation of more motor units
is the action potential shorter or longer in duration than the resulting contraction?
shorter
what aspect of the skeletal muscle action potential prevents tetanic contraction?
a long refractory period
describe the relationship developed by skeletal muscle tension and frequency of stimulation
skeletal muscle tension increases with increasing frequency of stimulation
when is skeletal muscle at its optimum length?
at resting conditions
when is cardiac muscle at its optimum length?
when stretched
name the contractile component of skeletal muscle
cross bridge cycling via sarcomeres
name the elastic component of skeletal muscle
stretching and tightening of muscle connective tissue and tendon
name the 2 types of skeletal muscle contraction
isotonic
isometric
which type of skeletal muscle contraction changes its length but not its tension
isotonic contraction
give an example of isotonic contraction
moving objects
body movements
which type of skeletal muscle contraction changes its tension but not its length
isometric contraction
give an example of isometric contraction
supporting objects
maintaining body posture
name the main differences between different types of skeletal muscle?
methods of ATP synthesis
resistance to fatigue
myosin ATPase activity
what effect does myosin ATPase have on skeletal muscle?
increases speed of muscle contraction as it makes ADP more readily available for cross bridging
name the different methods of ATP production in muscle
creatinine phosphate to ADP, oxidative phosphorylation, glycolysis
which pathway provides the main source of ATP when oxygen isnt present
glycolysis
which pathway provides the main source of ATP when oxygen is present
oxidative phosphorylation
name the 3 types of skeletal muscle
type 1, 2 and 2x
which skeletal muscle type has a slow contraction speed and a high resistance to fatigue
type 1
which skeletal muscle type has a high contraction speed and large number of mitochondria
2a
which skeletal muscle type depends on anaerobic activity?
2x
which skeletal type is white?
white
through what kind of activity is type 1 skeletal muscle used?
walking, posture maintenance
through what kind of activity is type 2a skeletal muscle used?
jogging, moderate activity
through what kind of activity is type 2x skeletal muscle used?
short term high intensity eg jumping
why are type 2 skeletal muscles very fast?
high myosin ATPase activity
what is a reflex action?
a stereotyped response to a specific stimulus
is the stretch reflex a negative or positive feedback mechanism?
negative
what structure is the sensory receptor in the stretch reflex?
muscle spindle
what is the sensory receptor activated by in the stretch reflex?
muscle stretch
what causes contraction of muscle in the stretch reflex?
stretching of the muscle stimulates firing of afferent neurons, these synapse in the spinal cord with the alpha motor neurons that innervate muscle
what nerve levels and overall nerve are tested in the knee jerk test?
L3, L4; femoral
what are muscle spindles?
collection of specialised muscle fibres
where muscle spindles found?
in the belly of muscles parallel to normal muscle fibres
what is an extrafusal fibre?
normal muscle fibre
what are the sensory nerve endings of muscle spindles called?
annulospiral fibres
what are the efferent neurons that supply muscle spindles called?
gamma motor neurons
what do gamma motor neurons do?
adjust tension levels in skeletal muscle to maintain sensitivity
does the contraction of muscle spindles contribute to overall muscle contraction?
no
give an example of an inflammatory acquired myopathy
polymyositis
give an example of a non-inflammatory acquired myopathy
fibromyalgia
give an example of an endocrine acquired myopathy
cushings syndrome, thyroid disease
investigations for neuromuscular disease?
electromyography
nerve conduction study
creatine kinase
CRP
