muscles Flashcards
what are muscles for
whole body movements and localised movements
holding joints in place, maintaining posture
movement of substances within the body
thermogenesis
what is thermogenesis
production of heat - normal opperation
how do muscles achieve the things they do
contractility
electrical excitability
elasticity
extensibility
define contractability
the ability of muscle to contract forcefully
what is electrical excitability
can produce electrical signals which
allow regulation of contraction via excitation contraction
coupling – Control
what is elasticity
muscle returns to original length after contraction or
extension
what is extensibility
can stretch without being damaged – allows
contraction even after stretching e.g. cardiac muscle after filling
of heart, digestive tract after meal
what is the structure of cardiac muscle tissue
striated
is cardiac muscle tissue voluntary or involuntary
involuntary
where is cardiac muscle tissue found in the body
forms myocardium of the heart
what is the structure of smooth muscle tissue
non striated / smooth
is smooth muscle tissue voluntary or involuntary
involuntary, sometimes auto-rhythmicity
where is smooth muscle found within the body
walls of internal structures like blood vessels
how are skeletal muscles controlled
by neurons via the neuromuscular junction
how many neuromuscular junctions do each muscle fibres have
1
how many muscles fibres do somatic motor neurons branch to innervate
150 avg
what are the typical measurements of a muscle fibre
diameter 10-100um
length 10-30cm
what is the sarcolemma
the plasma membrane of the muscle fibre
what is the role interstitial fluid in transverse tubules that move into the muscle fibre from the sarcolemma
allows depolarisation to spread throughout the fibre
what is the sarcoplasm
interior of muscle fibre
what does sarcoplasm contain a lot of
glycogen and myoglobin
what are the 3 types of muscle proteins
contractile, regulatory and structural
what is the role of contractile proteins
generate force during contraction (actin and myosin, motor protein)
what is the role of regulatory proteins
switch contraction on and off
what is the role of structural proteins
hold contractile components in proper alignment. Allow elasticity and extensibility
what lines do sarcomeres run from
z line to z line
what is the m line
the centre of myosin
what is the H zone
myosin alone
what is the A band
myosin alone as well as actin and myosin overlap
what is the I band
actin alone
what happens to the lines and bands when muscles contract
M line - no change
Z line - move closer
I and H zone shorten
A bands stay the same
what is a power stroke in muscles
the formation of a cross bridge between filaments causing a change in shape of cross bridge - twisting motion - which in turn moves actin along
is ATP hydrolysed or synthesised to reset the myosin head
hydrolysed
what regulated contraction of muscles
excitation contraction coupling
what is the concentration of calcium like in cell cytosol at rest
0.1u mole per litre
where can calcium be released from to promote more muscular contractions
sarcoplasmic reticulum
what is the sequence that results in muscular contraction
activation of NMJ causes action potential
- this propagates along sarcolemma and into T tubules
- depolarisation causes opening of calcium release channels- calcium released into cystol
- calcium binds to troponin which changes the conformation of the troponin-tropomyosin complex
- which clears the actin-myosin binding site
what is Twitch Contraction
Brief
contraction of a motor
unit. Stimulate nerve and
muscle depolarises.
what is Tetanic Contraction:
Once refractory period is over, contractions can summate if inadequate time for relaxation
what is an isometric muscle contraction
◦ Muscle exerts force without changing length
◦ Pulling against immovable object
◦ Postural muscles
what is an isotonic muscle contraction
◦ Concentric - Muscle shortens during force production
◦ Eccentric - Muscle produces force but length increases
what does the muscle spindle receptor detect
◦ Detect dynamic and static
changes in muscle length
◦ Stretch reflex
◦ Stretch on muscle causes reflex
contraction
what does the Golgi tendon organ detect
◦ Monitor tension developed in
muscle
◦ Prevents damage during
excessive force generation
◦ Stimulation results in reflex
relaxation of muscle
the heart has auto rhythmicity what does this mean
constant process of contraction and
relaxation.
what does an organ with auto rhythmicity require and have more than others
needs more energy so has more mitochondria
what initiates contractions in smooth muscles
binding calcium binding to calmodulin and activating myosin light chain kinase.
which phosphorylates myosin head making it active
what autonomic innervations do smooth muscles respond to
pH oxygen co2 hormones
what does The distribution of myofilaments determine
the changes in cell shape associated with contraction
and relaxation
why are smooth
muscle found orientated
longitudinally and transversely
Smooth Muscle can also relax in response to?
chemicals cAMP
and cGMP (intracellular messengers)
Skeletal Muscle, Cardiac Muscle and Smooth Muscle all contract
in response to the presence of ?
intracellular calcium ions
what are the 2 main control mechanisms in smooth muscle control
electrochemical (membrane potential change)
describe the stages of smooth muscle contraction mechanism
- Calcium enters the smooth muscle cell
- Calcium binds calmodulin
- Activation of MLCK (myosin light chain kinase)
- Phosphorylation of myosin leading to contraction
- If calcium drops, loose phosphorylation, muscle relaxes
- Cyclic nucleotides can reduce calcium levels in the cell
(interplay with cell signalling pathways)
