Physiology - Skeletal Muscle Flashcards
what is the largest tissue type in the body?
muscle
what are the three types of muscle?
skeletal
cardiac
smooth
what muscle types are striated?
cardiac
skeletal
what muscle type is not striated?
smooth
what causes muscle striation?
alternating dark and light bands
what are the dark bands in muscle?
myosin thick filaments
what are the light bands in muscle?
actin thin filaments
what nervous system innervates skeletal muscle and what does this mean?
somatic
voluntary control
what nervous system innervates cardiac and smooth muscle and what does this mean?
autonomic
involuntary control
what mechanism initiates contraction of skeletal muscle?
neurogenic
what mechanism initiates contraction of cardiac muscle?
myogenic
in which type of muscle are neuromuscular junctions present?
skeletal
in which type of muscle are gap junctions present?
cardiac
what is the neurotransmitter at the neuromuscular junction?
acetylcholine
what are skeletal muscle fibres organised into?
motor units
what is a motor unit?
a single alpha motor neurone and all skeletal muscle fibres it innervates
what does the number of muscle fibres per motor unit depend on?
the functions served by the muscle
fine movement = less fibres
name two types of muscles with few fibres per motor unit
intrinsic hand muscle
extra ocular muscles
how are skeletal muscles organised?
parallel muscle fibres bundled by connective tissues
how long are skeletal muscle fibres?
the length of the muscle
what attaches skeletal muscles to the skeleton?
tendons
what is the predominant structure of skeletal muscle fibres?
myofibrils
what is found within each myofibril?
sarcomeres
what is the functional unit of muscle?
sarcomeres
what is the functional unit of an organ?
the smallest component capable of performing all of the organs functions
where are sarcomeres found?
between two Z lines
what are the four zones of a sarcomere?
A band
H zone
M line
I band
what makes up the A band?
thick filaments
thin filaments that overlap
what is the H zone?
the lighter area in the middle of the A band where thin filaments don’t reach
where is the M line found?
the middle of the A band and the centre of the H zone
what is the I band made of?
the remaining thin filaments that are not in the A band
what produces muscle tension?
sliding of actin filaments on myosin filaments
what does force generation depend on?
ATP dependent interactions between myosin and actin filaments
where are calcium ions stored in skeletal muscle fibres?
the lateral sacs of the sarcoplasmic reticulum
when are calcium ions released in skeletal muscle?
when the surface action potential spreads down the T tubules
what are T tubules?
extension of the surface membrane that dip into the muscle fibre
what two factors determine the gradation of skeletal muscle tension?
number of fibres contracting
the tension developed by each fibre
what is motor unit recruitment?
the stimulation of more motor units in a muscle
what is longer in skeletal muscle - the duration of the AP or the duration of the resulting twitch?
the twitch
how can a stronger contraction be achieved in skeletal muscle?
repetitive fast stimulation of the muscle
what is repetitive fast stimulation of muscle called?
tetanus
why can cardiac muscle not be tetanised?
long refractory period
how can maximal tetanic contraction be achieved?
when muscle is the optimal length before the onset of contraction
what are the two types of skeletal muscle contraction?
isotonic
isometric
what is isotonic contraction used for?
body movements
moving objects
what is isotonic contraction?
when muscle tension remains constant as the muscle length changes
what is isometric contraction used for?
supporting objects in fixed positions
maintaining body posture
what is isometric contraction?
when muscle tension develops at constant muscle lengths
