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IMED1001 > Muscular system > Flashcards

Muscular system Flashcards

1
Q

skeletal muscle

A

attached to bones of skeleton
striated
voluntary control
multiple nuclei

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2
Q

cardiac muscle

A

walls of heart
striated, intercalated discs
involuntary control
one nucleus

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3
Q

smooth muscle

A

walls of hollow organs
no striations
involuntary control
one nucleus

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4
Q

functions of muscles

A

move bones, stabilise joints, posture, generate heat, glycaemic control, move substances around the body, protects visceral organs

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5
Q

wrapped in endomysium component

A

muscle fibres containing mitochondria nuclei contractile myofilaments
endomysium is thin loose, wraps around nerve fibres, capillaries, sarcolemma

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6
Q

wrapped in perimysium component

A

bundles of muscle fibres called fascicles, blood vessels, nerves, stretch receptors
perimysium is thick CT sheath

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7
Q

wrapped in epimysium content

A

thick fibrous sheath
inner surface projects between fascicles and forms peri
outer surface grades into fascia

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8
Q

fascia

A

thin casing of connective tissue surrouding and holding every organ, blood vessel, bone, nerve fibre, muscle in place
collagenous fibres arranged in an irregular weave, withstands stress from multiple directions

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9
Q

how are skeletal muscles attached

A

directly - epimysium fused to bone
indirectly - epimysium extends beyond muscle

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10
Q

tendon vs aponeurosis

A

flexible cord of collagen
flattened shape, regular weave of collagen fibres

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11
Q

retinaculum

A

retraining band or ligament, keeps tendons and ligaments in place

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12
Q

circular fascicle

A

concentric rings, forming a sphincter

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13
Q

convergent fascicle

A

fan shaped, broad origin, converge at a single tendon for insertion

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14
Q

parallel fascicle

A

parallel to the long axis of the muscle

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15
Q

pennate fascicle

A

fascicles run obliquely to a central tendon
uni: fascicles insert into 1 side of tendon
bi: fascicles insert into opposite sides of tendon
multi: many fascicles together

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16
Q

fusiform fascicle

A

thin at the ends, thick in the middle

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17
Q

naming muscles

A

location : insertion and origin
size: major/maximus, minor/minimus, longus, brevis
shape: orb, rhomboid
orientation: rectus, transversus/oblique
function: flexor, extensor, opponens
number of origins

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18
Q

muscle action

A

agonist: muscle supplying the main force for movement
antagonist: muscle that opposes or reverses movement
synergist: changes direction of movement/aid agonist
fixator: stabilises bones during movement

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19
Q

muscle fibre composition

A

made up of myofibrils, which consists of sarcomeres, surrounded by sarcoplasmic reticulum

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20
Q

sarcomere structure

A

sarcomere spans between 2 Z lines
thick myosin filaments forms A band, attached to Z lines by titin
thin actin filaments form I bands, attached to Z lines with α-actinin
H zone is the part with myosin only

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21
Q

actin structure

A

double helix of globular actin proteins
tropomyosin
troponin complexes (T/I/C)

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22
Q

myosin structures

A

composed of many myosin molecules, each head has ATP binding site and actin binding site, able to change conformation between high and low energy states

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23
Q

during contraction zones length change

A

H zone and I band shortens, sarcomere shortens
A band doesn’t change length

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24
Q

formation of cross bridges and power stroke

A
  1. myosin head (high energy) attaches to actin active sites, crossbridge forms (contains ADP and Pi)
  2. power stroke occurs, myosin head rotates and pulls on actin, sarcomere shortens (releases ADP and Pi)
  3. ATP binds to myosin, binding causes conformational change that detaches crossbridge
  4. ATP hydrolysis occurs, myosin head is recocked to high energy state
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25
passive vs active tension and when are they most generated
passive - from elastic components of muscle (tendon, α-actinin, titin), most generated when muscle is stretched active - from crossbridge formation, most generated when there is max overlap between fibres both involved in contraction, only passive is involved in relaxed state
26
length tension curve for active tension
overly shortened - thick filaments just hit Z lines overly stretched - no overlap between actin and myosin optimum length - 100% overlap between actin and myosin, resting muscles maintained at this length (muscle tone)
27
when is max power generated
at intermediate loads and intermediate velocity
28
when is no power generated
velocity is 0, muscle is not moving - isometric contraction force is 0 - muscle isn't contracting
29
T tubules and triad SR
T tubules: infoldings of the cell membrane penetrating through the cell, emerging on the other side Triad: where SR and plasma membrane meet
30
calcium transporters on plasma membrane (storage)
PMCA NCX: Na Ca exchanger (secondary active transport)
31
calcium transporters on SR and functions (storage)
SERCA - scavenge Ca from myoplasm, needs lots of ATP calsequestrin - binds free Ca ions, reduces free Ca gradient, prevents SR from losing too much Ca when gates open
32
ion channels for Ca release
dihydropyridine receptor - voltage gated "L type" channel, doesn't inactivate and lock ryanodine receptor - mechanically gated in skeletal muscle, found on SR
33
coupling of DHPR and RyR1
located right next to each other AP opens DHPRs, which pushes RyR1 Ca floods into myoplasm after a long time, DHPRs close, RyR1 also closes
34
Ca causing TM conformational change
Relaxed muscle: tropomyosin blocks myosin binding site on actin filaments (regulated by troponin complex) Ca binds to Troponin-C, conformational change occurs, pulls tropomyosin out of myosin bindng site, crossbridges can now form
35
NMJ description
synapse, neurotransmitter is ACh, nicotinic receptors, always excitatory considered a trigger zone, high Na channel density
36
excitation-contraction coupling
AP travels from nerve to muscle via NMJ excitatory PSP (end plate potential) occurs AP generated in muscle fibre plasma membrane, spreads down T tubules, opens DHPR and RyR1 Ca enters myoplasm, tropomyosin conformational change, crossbridges form, sarcomeres contract
37
Excitation contraction coupling graph
graph of tension against time latent period: small gap between E and C contraction period relaxation period: takes a while for pumps to reduce Ca
38
twitch
motor neuron AP stops ACh degrated by AChE muscle AP stops, DHPR, RyR1 closes transporters remove Ca from myoplasm conformational change in troponin, myosin bidning sites blocked
39
wave summation and tetanus
twitches are slow, more than 1 AP takes place, wave summation increases Ca concentration, increasing tension tetanus: max tension when all troponin C is bound by Ca, all actin and myosin are forming crossbridges
40
sensory vs motor neuron pathways
sensory: first order to spine, second order to thalamus, third order to PSC motor: upper to spine, lower to muscle (heavily myelinated, fast)
41
movement initiation and maintenance
initiated by CNS, maintained by spinal reflexes continuous and instantaneous feedback required for muscle control
42
muscle spindles structure
intrafusal fibres (not contractile, have mechanically gated ion channels to measure stretch) contractile ends innervated with γMNs to shorten with the muscle
43
muscle spindles function
measure change in muscle length and tension, and rate of change in muscle length and tension RA/SA contract slower, so they are not hyperactive when muscle is shortening
44
myotactic reflex
catch reflex muscle spindle sensory neuron synapses directly with motor neuron, increase αMN firing, contracts muscle more
45
Golgi tendon organ structure and function
receptors in myotendinous junction, measuring tendon tension, SA dont lengthen or shorten
46
inverse myotactic reflex
drop reflex sensory neuron from GTO synapses with inhibitory interneuron inhibits αMN firing, muscle relaxes
47
reflex coordination around joint
excitatory synapses for agonist, inhibitory interneuron synapse for antagonist muscle when inducing contraction in left leg, also simultaniously induces relaxation in right leg
48
motor unit definition
single motor neuron and the multiple muscle fibres it innervates
49
MU composition
in terms of no. fibres larger: more fibres/MU, strong smaller: less fibres/MU, weak in terms of no. MUs less: less dexterity more: more dexterity in terms of type of fibres slow: small forces, continuous activity fast: high forces, small explosive activity
50
skeletal muscle fibre types
I (slow fatigue resistant) IIa (fast fatigue resistant) IIb (fast fatiguable)
51
MU recruitment
small slow MUs are recruited first due to Hennemans size principle: small slow MUs have lowest threshold for synaptic activation muscle spindles and GTOs send sensory info to brain, brain evaluates info, recurits larger MUs
52
intercalated discs cardiac muscle
joins cardiac myocites together with desmosomes (transmits force) and gap junctions (allow ions to flow to transmit action potential quickly)
53
define autorythmicity
allows cardiac cells to depolarise rhythmically and independently, generating own APs without nervous stimulation
54
pace maker potential - prepontential
funny channels are leaky to Na ions, membrane slowly depolarised and rises towards threshold, allowing depolarisation to occur normally
55
pacemaker potential - repolarisation
L-type Ca ions channels are used, such that there is a plateau in the membrane potential APs are much longer
56
pacemaker potential - long refractory period
muscle cannot be stimulated, until contraction is almost over, allows blood to have time to fill chambers during refractory period prevents tetanus - fatal
57
what does ECG record
change in electrical potential, sum of electrical activity of all the cells
58
parts of ECG
P wave: atrial depolarisation QRS complex: ventricular depolarisation, atrial repolarisation T wave: ventricular repolarisation
59
smooth vs skeletal contraction structure
no organised sarcomeres, still has actin and myosin filaments arranged differently no troponin no NMJs but gap junctions no T tubules
60
smooth vs skeletal functional differences
Ca for contraction comes from ECF takes longer to contract but can remain contracted for a long time without fatigue
61
Ca channels smooth muscles
slow to open and close, long duration of contraction many different types available (ligand voltage mechanical)
62
smooth muscle contraction
Ca enters cell, binds to calmodulin on thick filaments activates kinase, activating myosin myosin burns ATP to pull on actin, which pulls the cytoskeleton force transferred to plasma membrane, entire cell shortens
63
latch bridge mechanism
myosin heads dont detach from actin immediately does not consume any more ATP, very efficient maintains tonic contraction - smooth muscle tone

IMED1001 (14 decks)

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