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HUBS191 Human Movement and Sensation > Muscles, contraction and movement > Flashcards

Muscles, contraction and movement Flashcards

1
Q

function of cardiac muscle

A

pumping of blood

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2
Q

function of smooth muscle

A

to control the movement of fluid e.g. blood, urine, digestion

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3
Q

function of skeletal muscle

A

to move, maintain posture, generate heat

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4
Q

structure of skeletal muscle

A
  1. Tendon attaches muscle to bone
  2. fascia
  3. muscle
  4. epimysium
  5. muscle bundle
  6. perimysium
  7. fascicle
  8. endomysium
  9. muscle cell aka muscle fibre aka myocyte
  10. sarcoplasmic reticulum and T tubule
  11. myofibrils
  12. sarcomere
  13. myofilaments
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5
Q

T-tubule

A

invagination of Extracellular space that allows the action potential to enter the myofibril and initiate the release of Ca2+

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6
Q

triad

A

T-tubule sandwiched between two SR

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7
Q

sarcolemma

A

plasma membrane of the muscle cell

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8
Q

sarcoplasmic reticulum

A

ER of a muscle cell and stores calcium

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9
Q

sarcomere

A

myofilament between to Z-disks= basal contractile unit

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10
Q

thin filament

A

actin, tropomyosin, troponin; Globular actin forms a double helix strand surround by two thin strands of tropomyosin

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11
Q

thick filament

A

myosin and myosin head

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12
Q

NMJ vs synapse

A
  • In healthy humans, there is no IPSP or EPSP
  • if an action potential reaches the NMJ it will cause contraction;
  • Should call the cleft the NMJ cleft rather than the synaptic clefts
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13
Q

3 steps of skeletal muscle contraction

A

excitation, contraction, relaxation

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14
Q

steps of excitation

A
  1. AP reaches end of motor neuron, which causes Ca2+ entry into nerve terminal
  2. Neuronal action potential Acetylcholine (Ach) released from the nerve terminal in synaptic vesicles
  3. Synaptic vesicles release Ach, which diffuses into the synaptic cleft
  4. Ach stimulates Ach-receptors on the adjacent muscle fibre, initiating an impulse in the muscle fibre
  5. Depolarisation of muscle sarcolemma, initiating an action potential
  6. Electro-chemical-electro coupling
  7. Action potential on the muscle fibre- always sufficient to reach threshold in healthy individuals
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15
Q

steps of contraction

A
  1. AP travels over sarcolemma and T-tubules very quickly, which triggers the release of Ca2+ ions from the adjacent sarcoplasmic reticulum almost simultaneously along the myofibril
  2. Large Ca2+ release from the internal Ca2+ store- ions diffuse to the myofilaments to trigger cross-bridge formation
  3. Cross-bridge formation of myofilaments
  4. Myosin head is in its energised state, with ATP bound
  5. Ca2+- troponin interaction exposes active site
  6. Actin-myosin interact as a cross-bridge
  7. Energised myosin head pulls the actin in a power-stroke
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16
Q

steps of relaxation

A
  1. No new AP- sarcolemma repolarises
  2. Ca2+ no longer bind to Troponin; ion re-uptake into internal Ca2+ store
  3. Troponin active sites are hidden
  4. Actin and myosin are still bound but not enough Ca2+ ions to initiate new cross-bridges
  5. ATP must bind for actin and myosin to uncouple cross-bridge
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17
Q

sliding filament model

A
  • When inactive the filaments are not over one another
  • When activated the myofibril shortens as the z-lines move closer
  • Myofilaments do not change length themselves
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18
Q

motor unit

A

one somatic Motor Neuron and Muscle Fibres innervated by its branches

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19
Q

energy sources for contraction

A

Anaerobic and anaerobic

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20
Q

features of anaerobic respiration

A
  • short term - fast energy production - no O2 required - ATP, creatine phosphate, glycolysis
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21
Q

features of aerobic respiration

A
  • long term - steady - slower energy production - O2 required - Oxidative phosphorylation
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22
Q

why is energy required for relaxation?

A

Ca2+ re-uptake into SR and uncoupling of crossbridges

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23
Q

types of muscle fibres

A

red, white and intermediate (myosin type IIa)

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24
Q

features of red muscle fibres and example

A

high myoglobin (myosin type I), high aerobic enzymes - soleus

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25
Q

features of white muscle fibres and example

A

low myoglobin (myosin type IIx), low aerobic enzymes - eye

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26
Q

function of red (myosin type I) fibres

A

slow rate interaction with actin; slow force production; slow energy consumption; sustained by aerobic metabolism

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27
Q

function of white (myosin type IIx) fibres

A

fast rate interaction with actin; fast force production; fast energy consumption; use anaerobic metabolism

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28
Q

what is a twitch

A

the smallest tension a muscle can produce - a single AP in a single motor unit

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29
Q

what is treppe

A
  • repeated stimuli - sustained levels of SR Ca2+ = more contraction - actin and myosin become more sensitive to Ca2+ - more sensitive at higher temperatures
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30
Q

what is tetanus

A
  • rapidly repeated stimuli - closely spaced twitches - heat increases sensitivity - mechanical summation due to high Ca2+ in SR
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31
Q

effects of strength training on muscle

A
  • Increased number of contractile filaments- hypertrophy - More power - Improved anaerobic metabolism
32
Q

effects of disuse of muscle

A
  • Loss of number of contractile filaments- atrophy - Less power
33
Q

effect of endurance training on muscle

A
  • Increased blood supply to muscle - higher number of blood vessels - More mitochondria - More aerobic enzymes - Improved aerobic metabolism
34
Q

description fatigue

A
  • state of exhaustion (loss of strength or endurance) produced by strenuous muscle activity
35
Q

physiological fatigue

A
  • ATP depletion, secondary to depletion of glucose, glycogen and O2 - Build-up of metabolic by-products: e.g. Pi and lactic acid
36
Q

psychological fatigue

A
  • feedback from working muscles to brain produces sensation of fatigue, even though muscle is still capable of contraction
37
Q

cardiac muscle structure

A

• Intercalated disks; lots of individual cells stuck together that create a mesh work • Desmosomes (mechanical)-proteins that stand the gap between cells and act as the glue; when one cell contracts, it pulls on its neighbour • Gap junctions (electrical)- connection that allows one action potential in a myocyte to pass into the next myocyte; therefore, cells are electrically connected

38
Q

cardiac muscle function

A

• Heart controlled by nerves from the brain called the Sinoatrial node (pacemaker), and depolarises the atria • Signal passes into the atrioventricular node, which depolarises the septum between the ventricles • The signal passes to the outside of the ventricles and depolarises them • More and more contractions occur as the heart becomes more depolarised; when fully polarised blood flows out • Relaxation allows blood flow back in

39
Q

smooth muscle structure

A

• Filaments organised similarly to skeletal muscle- actin and myosin move over one another • Dense bodies are nodes within the cell and pull the cells together into a mesh • Contraction involves squeezing the cell down • Sustained tension- e.g. sphincters • Large length changes- e.g. bladders • Cells form a ring length wise around the digestive tract, cells formed in the same direction • Cells form rings around tubes- controls the movement of whatever travels through the tubes

40
Q

Single-unit smooth muscle

A

gap junctions allow electrical signal to be transferred from one cell to the other; all electrically connected; thus, many cells can be considered a single unit

41
Q

Multi-unit smooth muscle

A

muscles cells are not electrically connected as no gap junctions, more varicosities present to innervate more cells

42
Q

Smooth muscle: Excitation-contraction

A

• Action potential or hormones provide Ca2+ rise • Ca2+ binds to Calmodulin which activates protein called Myosin light chain kinase (MLCK) into an active and inactive cycle • MLCK activates MLC which activates the cross bridge • Myosin filaments regulated • A kinase adds phosphate (P), whereas a phosphatase removes a phosphate (P), changing the function (active/inactive) of the protein

43
Q

four types of information that describe a sensory stimulus

A
  • modality (type of receptor activated) - intensity (frequency of AP firing) - duration of AP firing - location
44
Q

Specialised receptor cell

A

modified nerve ending converts a unique stimulus into an action potential e.g. temperature, pressure

45
Q

special senses

A

Vision, Hearing, Taste, Smell, Vestibular (balance)

46
Q

cell shapes of 3 muscle types

A

Skeletal Muscle has Long, cylindrical, multinucleate cells; Cardiac Muscle has mononucleate, branching cells; Smooth Muscle has mononucleate, spindle-shaped cells

47
Q

presence of sarcomeres in 3 muscle types

A

present in skeletal muscle, present in cardiac muscle, absent in smooth muscle (hence no striations)

48
Q

filament which is regulated to allow contraction in 3 muscle types

A

skeletal muscle is actin, cardiac muscle is actin, smooth muscle is myosin

49
Q

AP propagation in 3 muscle types

A

in skeletal muscle, AP does NOT spread from cell to cell; in cardiac muscle, APs DO spread from cell to cell; in single unit smooth muscle, APs do spread from cell to cell; in multi unit smooth muscle, APs do not spread from cell to cell

50
Q

presence of T tubuli in 3 muscle types

A

present in skeletal muscle; present in cardiac muscle; absent in smooth muscle

51
Q

nervous system input of 3 muscle types

A

skeletal muscle is somatic motor (voluntary); cardiac muscle is visceral motor (involuntary); smooth muscle is visceral motor (involuntary)

52
Q

speed of contraction of 3 muscle types

A

skeletal is fast; cardiac is slow; smooth is very slow

53
Q

3 types of modality

A

proprioception, touch and pain

54
Q

how is proprioception detected

A

golgi tendon organ is a protective device that detects tension; muscle spindles are length receptors that detect shortening of muscle and maintain posture

55
Q

adaption to stimulus

A

decreased receptor potential over time in response to continuous stimulation

56
Q

receptor field

A

 Region of space in which a stimulus can lead to activity in a particular afferent neuron  Small fields and dense innervation gives good discrimination

57
Q

Afferent pathway for touch, posture, vibration

A
  • Dorsal column pathway (Medial lemniscal pathway)
  • Three neurons in relay
  • Up and across
  • The sensory neurons from muscle spindles- fastest neurons in the body
  1. cell body in dorsal root ganglion
  2. up dorsal column of spinal cord
  3. crosses side in medulla
  4. synapses in thalamus
  5. to primary somatosensory cortex
58
Q

somatosensory cortex function

A

sensation (conscious identification of what and where) and perception (meaningful interpretation)

59
Q

Somatotopic organisation

A
  • Areas of the cortex correspond to areas of the body
  • Densely innervated areas of the body occupy large regions of the cortex
  • Left cortex represents right body and vice versa
60
Q

stimulus modality of pain

A
  • Sensed by free nerve endings (Nociceptors)
  • Located in organs throughout the body but not in the brain
  • Specialised sensitivity to local chemicals signals in damaged tissue
61
Q

Fast (acute) pain

A
  • Small receptive field
  • Large myelinated afferent axons
  • Somatic pain
62
Q

Slow (chronic) pain

A
  • Large receptive field
  • Small unmyelinated axons
  • Visceral pain
63
Q

Afferent pathway for pain and temperature

A

Lateral spinothalamic (antero-lateral) pathway

  • Minimum of 3 neurons in a relay (can have interneurons)
  • Neurons go across and up
  • Far less precise in location than other afferent pathway
  1. cell body in dorsal root ganglion
  2. crosses side immediately
  3. synapse in dorsal horn on opposite side
  4. up antero-lateral column of spinal cord
  5. synapse in thalamus
  6. to primary somatosensory cortex in post-central gyrus
64
Q

reflex movement

A
  • A predictable, reproducible, automatic response to a particular sensory stimulus; force of response depends on how many motor units activated
  • Organised neural circuit- recognise specific disturbances to the body
  • usually organised within spinal cord
65
Q

two types of reflex

A

stretch reflex and withdrawal reflex

66
Q

stretch reflex mechanism and function

A

prevents muscle fibres being torn by stimulus

67
Q

withdrawal reflex mechanism and function

A

protect the body from damaging stimuli by moving away from it

68
Q

primary motor cortex function

A

execution of movement via activation of specific motor units

69
Q

premotor cortex function

A

planning movement

70
Q

corticospinal pathway (pyramidal tract) strructure and function

A

Controls precise movement of hands and feet

Upper motor neuron:

  • Primary motor cortex
  • Crosses over at medulla
  • Corticospinal tract in spinal cord
  • Excitatory synapse onto lower motor neuron
  • Sometimes an interneuron

Lower motor neuron

71
Q

Non-corticospinal pathways (extrapyramidal tracts)

A
  • all other descending pathways onto the final common pathway
  • excitatory and inhibitory
  • reticulospinal tract: excites lower motor neurons to extensors, inhibits flexors
  • rubrospinal tract: excites flexors, inhibits extensors
  • for automatic movements like walking, chewing
72
Q

function of basal nuclei in integration between motor and sensory systems

A
  • Modify movement using a loop stem with the cortex
  • Pre-programming through extensive practice allows muscle memory
  • Help select an appropriate movement for a given situation
  • inhibition of inappropriate movement for a given situation
73
Q

function of cerebellum in integration between motor and sensory systems

A
  • Ensures the selected movement is coordinated, guided by sensory feedback
  • Compares intention with result
  • Maintenance of posture
74
Q
A
75
Q

steps leading to voluntary movement of a skeletal muscle

A

HUBS191 Human Movement and Sensation (4 decks)

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