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BDS 1 BAMS > Locomotor System > Flashcards

Locomotor System Flashcards

1
Q

what is meant by calcium activated calcium release

A

calcium channels opened at +35mV L-type channels, causes calcium to move into cytoplasm, calcium in the cytoplasm then generates release of more calcium from sacroplasmic reticulum

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2
Q

what activates calcium release from the SR

A

calcium binding to ryanodine receptors in skeletal, smooth and cardiac muscle, but also IP3 receptors in smooth muscle

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3
Q

how is calcium removed from the cytoplasm of the cell

A

re-uptake by the SR through serca receptors, or exchanging calcium out of the cell for sodium into the cell - NCX receptors

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4
Q

how does Calcium allow for contraction in skeletal and cardiac muscle

A

calcium binds to troponin C subunit, which changes the orientation and moves the tropomyosin away from the actin binding site, exposing this to myosin

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5
Q

how does calcium allow for contraction in smooth muscle

A

calcium binds to calmodulin, this complex this activates myosin light chain kinase, allowing it to phosphorylate myosin, allowing it to bind to actin

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6
Q

explain the cross bridge cycle in muscle contraction

A

myosin not bound to actin, bound to ATP molecule, muscle relaxed but myosin head cocked. myosin hydrolyses ATP to bind to actin, releases an inorganic phosphate. then generates a power stroke, shortening the sacromere and releasing ADP. muscle contracted but myosin head relaxed. then for muscle relaxation, ATP required to pull myosin head off of the actin

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7
Q

describe an abnormality of muscle physiology

A

when RyR are leaky, constantly releasing calcium into the cytoplasm, can get random contractions of muscle. also, Ca cytoplasm conc. increased so removal of Ca by NCX, SR levels of Ca constantly reduced, leads to inability to contract muscle due to lack of Ca - duchennes muscular dystrophy

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8
Q

describe the structure of a sensory neuron

A

pseudounipolar - has one cell body with 2 axons, one axon projects to periphery with nerve endings, one axon projects to central nervous system

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9
Q

what sensory information must be conveyed

A

quality, intensity, location and duration

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10
Q

how do we know the quality of a sensation

A

different receptors are activated for different types of sensation - nociception for pain, mechanoreceptors for touch

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11
Q

what is the receptive field

A

the area a neurone innervates, has nerve ending receptors in this location providing this area with sensory neurones

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12
Q

what is two point discrimination and how can this differ in different regions of the body

A

the minimum distance at which two points of touch can be felt as separate. areas with smaller two point discrimination have a higher density of neurones and a higher cortical representation, fingers, lips

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13
Q

how is an action potential generated in response to a sensation

A

mechanoreceptors - touch and pressure changes the membrane and opens a channel to allow influx of ions
chemoreceptors - either ligand gated which a ligand directly opens a channel or g-protein, ligand activates g protein which in turn opens a channel

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14
Q

how is the intensity of a stimuli detected

A

increased firing codes for a higher intensity, a lot of neurones recruited and increased frequency of action potential off the back of another means a higher intensity

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15
Q

how is the duration of a stimuli detected

A

the length of time an action potential is generated either slowly or rapidly adapting

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16
Q

what is the different types of axons and what are these used for

A

a alpha - motor neurones and sensory 1A fibres
a beta - mechanoreceptors
a delta - nociception and temperature
c fibres - pain temperature and itch

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17
Q

describe the pathway for mechanoreception from the body

A

the sensory afferents enter through the dorsal horn and immediately ascend through the medial lemniscal dorsal column pathway. first order neurons travel to the brainstem where they synapse to second order neurones. these then travel dessicate to the thalamus to synapse to 3rd order neurones which go to the cortex

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18
Q

describe the pathway for nociception from the body

A

these enter the dorsal horn of the spinal cord and synpase to 2nd order neurons. these then cross over to the other side and travel to the thalamus via the spinothalamic tract. at the thalamus, 3rd order neurones are activated and these travel to the cortex

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19
Q

how are the sensory pathways arranged

A

modality specific

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20
Q

what are the different types of pain

A

nociceptive, clinical - acute and chronic

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21
Q

describe nocicpetive pain

A

this is in response to tissue damage, a protective mechanism for us to remove ourselves from the stimulus, a delta or c fibres, high threshold and limited duration

22
Q

describe acute pain

A

similar to nociceptive, in response to inflammation, prostaglandins and bradykinin activate receptors, protective function

23
Q

describe chronic pain

A

serves no protective function, due to damage in a nerve, activated despite no stimuli or damage, spontaneously activates pathway, not responsive to treatment

24
Q

how is pain located

A

each spinal nerve gives rise to a dermatome, an area of the body that it innervates, when this nerve is activated it travels to a specific area of the cortex in the sensory homunculous so the location can be noted

25
Q

what is referred pain

A

when the damage is at one area of the body but the pain is felt elsewhere, due to embryological development

26
Q

what are the different peaks in the pain activation

A

first peak - activation of a beta in response to touch
second peak - activation of a delta fibres in response to pain - sharp pain
third peak - activation of c fibres, dull pain - different latencys due to different myelination and diameter

27
Q

How can perception of pain be dampened down

A

by rubbing the effected area, this activates mechanoreceptors and a beta fibres, this then travels to spinal cord where most travel up DCML pathway, but some come off and activate inhibitory interneurones, to inhibit the STT tract - reduced pain

28
Q

what are the cardinal signs of inflammation

A

redness, heat, swelling, pain, loss of function

29
Q

what are the 3 things in the triple response

A

red line, wheal and redness

30
Q

what is the wheal in the triple response

A

this area is white and is swollen, due to oedema, inflammatory exudate moving in to deal with the trauma

31
Q

what is the red area in the triple response

A

this area is not swollen or raised, just red due to dilation of blood vessels

32
Q

what are the main features of the reflex movements

A

stereotyped response, short latency, no cortical in put even with conscious control, monosynaptic circuit involving peripheral nerve and spinal cord/brainstem

33
Q

what is required for a reflex movement

A

stimuli, receptor, sensory nerve, motor nerve, effector organ, response

34
Q

what nerve fibres are involved in the reflex response

A

A alpha fibres for both sensory and motor

35
Q

how is posture maintained

A

stretch in muscle is detected by proprioceptors, this then activates muscle 1A afferents, enters dorsal horn, synapses to motor neurone, causes contraction of muscle

36
Q

describe the tendon jerk reflex

A

tapping the tendon causes stretch of the muscle, activating muscle spindle receptors which activates muscle 1A afferent fibres, enter dorsal horn and synapse to efferent to cause contraction

37
Q

how does the ankle tendon and jaw tendon reflex differ

A

the same mechanism but the jaw has a much shorter latency, as it is closer to the brainstem, the circuit is shorter so happens much faster. but the ankle has a bigger response as the muscles recruited are stronger

38
Q

describe the gag reflex

A

sensory receptors on soft palate are activated, this activates glossopharyngeal nerve which travels to spinal trigeminal nucleus, then synapse and activate vagal nerve to cause contraction of pharyngeal constrictors on both sides

39
Q

how does the reflex movement prevent muscle overloading

A

muscle overloading is detected by golgi tendon receptors, activates IB muscle afferents, this are inhibitory neurones and inhibit the motor neurones at the spinal cord, stops muscle contraction

40
Q

how is overloading of the jaw detected and controlled

A

in jaw, no golgi tendon receptors, instead, PDL detects the loading of the jaw muscles and feeds back to the muscles of mastication and trigeminal nerve to control force of biting

41
Q

what is the jendrasik manoeuvre

A

clasping the hands, this activates the corticospinal tract, meaning motor neurones are closer to their action potential even if theyre not being used, so when the reflex loop comes in to synapse, more neurones are recruited meaning more muscle fibres can be contracted - higher magnitude of response

42
Q

what controls semi-automatic movements

A

central pattern generator - generates a rhythm

43
Q

what provides feedback for semi-automatic movements

A

environment, effector organ, conscious control from cortex

44
Q

how many neurones are involved in motor pathways

A

2 - one upper, from cortex, one lower from brainstem or spinal cord

45
Q

describe the corticobulbar pathway

A

motor cortex activates upper motor neurone, travels to the brainstem, synpases at trigeminal nucleus, vagal, glossopharyngeal, hypoglossal, facial, this then activates the lower motor neurone which travels to the muscle to generate contraction

46
Q

describe the corticospinal pathway

A

motor cortex generates upper motor neurone, these travel to the medullary pyramids where they decussate - 85% do, 15% do not - stay on same side. those decussated form the lateral pathway, the others form the anterior pathway. then travel to the correct level of the spinal cord for activating the lower motor neurones

47
Q

how might the upper motor neurones be damaged

A

stroke

48
Q

what would be the result of upper motor neurone damage

A

not able to generate voluntary movements but still have reflexes, often more reinforced

49
Q

how might the lower motor neurones be damaged

A

nerve damage, trauma

50
Q

what would be the result of lower motor neurone damage

A

unable to generate any type of movement, even reflexes, muscle atrophy

BDS 1 BAMS (13 decks)

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