finals study - all topics

Question 1

what is the muscle breakdown

Answer 1

whole muscle -> fascicle -> fibre or M cell -> myofibril

Question 2

what is the epimysium

Answer 2

surrounds the muscle tissue

Question 3

what are the 3 roles of skeletal muscle

Answer 3

stores protein (metabolism)
movement and generates force
thermogenesis

Question 4

what are the 4 unique properties of muscle

Answer 4

excitability/irritability, contractility, extensibility, and elasticity

Question 5

what is excitability/irritability

Answer 5

developing and propagating (sustaining) a transient electrical event (action potential)

Question 6

what is contractility

Answer 6

ability to shorten

Question 7

what is extensibility

Answer 7

stretched without damage

Question 8

what is elasticity

Answer 8

tends to return to original state after extensibility and contractility

Question 9

what are the 8 factors that affect torque

Answer 9

1. activation history
2. elasticity/passive stiffness
3. cross-bridge functions and energetics/ATP availability
4. muscle size
5. mechanics
6. innervation/neural activation
7. fibre type composition
8. antagonist balance

Question 10

what factors determine muscle phenotypic properties

Answer 10

1. cell lineage/genetic determinants
2. epigenetics

Question 11

what makes up epigenetics

Answer 11

• motoneurons, hormones, load/stretch

Question 12

what are the 2 components of structure <–> function contraction

Answer 12

1. contractile components
2. support and connecting protein components

Question 13

what makes up the contractile components

Answer 13

muscles that shorten (actin and myosin)

Question 14

what makes up the support and connecting protein components

Answer 14

• collagen and elastin form connective tissue at many levels
• epimysium (whole muscle separation)
• perimysium (fascicles)
• endomysium (fibre level)

Question 15

what are the roles of structural proteins at the sub-cellular level

Answer 15

• support contractile components
• transmit force to tendons
• resist injurious stretch by wide distribution of forces
• mechanotransducers
• promote gene transcription
• involved in protein metabolism

Question 16

what is the Hill (1938) model

Answer 16

1. passive elements (CT, tendons and titin)
2. active elastic elements (rotation of myosin heads during actin attachment)
   - parallel elastic elements (PE)
   - series elastic elements (SE)
   - contractile element (sarcomere)

Question 17

what are the determinants of muscle force output

Answer 17

• size, shape, composition
• increased size = increased force
• shape
• slow twitch vs fast twitch
• adaptability
• variations of muscle shape/architecture
• pennation
• extrinsic factors

Question 18

what makes up size, shape and composition

Answer 18

mass, geometry and fibre type

Question 19

what makes up increased size = increased force

Answer 19

muscle force is proportional to cross-sectional area (CSA) or more correctly, physiological cross-sectional area (PCSA)

Question 20

what makes up shape

Answer 20

compartments, length of fibres, and pennation arrangement -> pennation affects PCSA

Question 21

what makes up slow twitch vs fast twitch

Answer 21

fibre type composition affects speed and endurance of muscle contraction

Question 22

what makes up adaptability of skeletal tissue

Answer 22

muscle atrophy aligns with adipose tissue/subcutaneous fat buildup

Question 23

what makes up variations of muscle shapes and architecture

Answer 23

different pennation types, and length of fibre architecture of fibre

Question 24

what are the different types of pennation

Answer 24

• unipennate = linear from end-to-end (fastest)
• bipennate = angular to central tendon (large fibre length to muscle length ratio)
• multipennate = many angles to central tendon (highest pennation = most force, low muscle to fibre ratio)

Question 25

what makes up length of fibres

Answer 25

varies within and among different muscles, but usually does not span the length of the muscle (tendon-to-tendon) --> ratio of FL:ML = <1 (0.2-0.8)

Question 26

what makes up muscle fibre architecture

Answer 26

- affects contractile properties of whole muscle - a combination of series and parallel (not 100% of either) - in series -> contractile length and shortening velocity, greater ROM, and faster force produced and greater shortening - in parallel -> total force generating capacity, lower ROM, higher force produced total, shortens less

Question 27

what makes up the affect of pennation

Answer 27

- more fibres = more force - not a 1:1 ratio of force to fibre # - force is lost with angle but more in total - PCSA = CSA x cosB (greater angle from horizontal = more force lost, small loss of force per fibre, but great increase in packing density of fibres and overall greater force potential) - specific tension of fibres (F/PCSA ~15-20N/cm^2 or 2kg/cm^2) - larger PCSA = greater overall force capacity - can assess angle with an ultrasound - PCSA and ACSA (anatomical) are equal in non-pennated muscle -> therefore less force

Question 28

what are the extrinsic determinants of muscle force output

Answer 28

neural control, activation history, antagonist function

Question 29

what are the components of the motoneuron

Answer 29

soma, synapse, spinal cord regionalization, axon, axon hillock, dendrites

Question 30

what is the soma

Answer 30

- aka cell body - the ventral portion of gray matter in SC. > 100/muscle (may be several hundred) - hard to maintan (large SA) - very active cells - post-mitotic after birth - loss with aging - alpha exrafusal fibres and gamma intrafusal fibres (spindles) - small soma supports may long processes

Question 31

what is the different between alpha extrafusal fibres and gamma intrafusal fibres (spindles)

Answer 31

- alpha = what we will focus on, the main fibres of skeletal muscles - spindles = proprioception for length changes (feedback)

Question 32

what is the synapse

Answer 32

- electrical or chemical junction between neural tissues - transmission point between2 cells (same or different cells) - differential control - the site of information control (positive (excitatory) or negative (inhibitory) signal types -> need a balance

Question 33

what is the spinal cord regionalization of motoneurons

Answer 33

- regionalization meaning not randomized - the motoneurons span more than one lumbar level so paralysis at L2 won't necessarily make lost function completely

Question 34

what is the axon

Answer 34

- for efferent traffic (out of cell) -> toward the muscle - covered by organized myelin (lipid); nodes of ranvier

Question 35

what is the axon hillock

Answer 35

- for afferent traffic (into cell) - dendritic tree - > receiving information via synaptic connections (control points) - 1 axon = many dendrites - electrical or chemical

Question 36

what is the membrane potential pump

Answer 36

the pump requires energy which moves sodium and potassium in and out of the membrane -> potassium into cell and sodium out

Question 37

what are the steps to action potential

Answer 37

1. negative membrane potential inside the cell 2. threshold of excitation is reached 3. Na into cell 4. Na into cell and K out (depolarization) 5. K out of cell, at a big positive membrane potential 6. K out of cell causing membrane potential to return to normal (repolarization) 7. K channels and Na channels close and reset 8. extra K diffuses away -> overshoots (afterhyperpolarization) because wants to ensure the negative point is reached (for a few ms) -> if negative point isn't reached, can't send another

Question 38

what is the normal resting membrane potential

Answer 38

~-70mV -> if reached a rapid change in ionic concentration causes a reversal of the membrane potential to positive (+30 to 50mV) -> spike potential

Question 39

what is Na conductance

Answer 39

abrupt/rapid/big (lower than membrane potential, higher than K conductance)

Question 40

what is K conductance

Answer 40

(lower than both membrane potential and Na conductance)

Question 41

what is refractory

Answer 41

determines the number of action potentials that can be sent per millisecond -> includes absolute (can't produce) and relative (harder to produce)

Question 42

what are synaptic pots

Answer 42

not all input will reach threshold and cause action potential, not enough input so forgotten, small hyperpolarizing afterpotential -> smaller periods = less time between action potentials

Question 43

what is action potential

Answer 43

- AP amplitude is invariant and all-or-nothing - neural information is encoded by the frequency and pattern of impulses (rate coding) - refractory periods variable among different motoneuron types and determines basic firing rates - net charge of synaptic potentials - ~10K synapses generates an action potential at the axon hillock if critical threshold is reached (excitatory > inhibitory)

Question 44

what are nerve conduction velocities