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MEDICINE > NAS W3 - sensory & motor neuron > Flashcards

NAS W3 - sensory & motor neuron Flashcards

1
Q

EXTEROCEPTORS

A

receive info from world around us (our senses)

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2
Q

INTEROCEPTORS

A

receive stimuli from world inside us

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3
Q

RECEPTIVE FIELD

A
  • area innervated by a single neuron

- sensitive ares = smaller receptive field

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4
Q

RECEPTING STIMULUS TYPES

A

each sensory receptor responds to only one type of stimulus (e.g. firm/soft touch) but at a range of different intensities (labeled line - one nerve always ends in one effector and all its branches end there too)

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5
Q

RECEPTOR ADAPTATION

A
  • when receptors stop continuously triggering AP even though stimulus is constant
  • frees up our attention & resources to attend to other stimuli
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6
Q

PHASIC RECEPTORS

A

receptors that adapt rapidly (changing quickly helps give us instant updates on rate of change of stimulus/stimulus intensity)

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7
Q

TONIC RECEPTORS

A

receptors that adapt slowly & inform about duration & strength of stimulus

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8
Q

ADEQUATE STIMULUS

A

type of energy to which a stimulus is most sensitive

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9
Q

SENSE ORGANS

A

structure containing sensory receptors (to receive stimulus) & sensory nerve fibres (convey specific impulses to CNS)

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10
Q

TYPES OF MECHANORECEPTORS OF SOMATIC SENSORY SYSTEM

A
  • Meissner receptor - transmit sensations of light, fine touches (rapidly adapting)
  • Merkel receptor - slowly adapting & are between epithelial cells & respond to maintained stimulation
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11
Q

HOW SENSORY RECEPTORS IN PERIPHERY (side) INFORM BRAIN ON WAG1 IN/OUT BODY

A

action potentials conveyed from periphery to brain via sensory neurones

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12
Q

PACINIAN CORPUSCLE (PC)

A
  1. normally, stretch mediated sodium ion channels around neurone too narrow for sodium ions to pass through
  2. when pressure applied to PC, it is deformed & membrane around neurone stretches which widens sodium channel so ions can now diffuse into neurone
  3. influx of sodium ions leads to generator potential which creates nerve impulse that goes to CNS
  4. if stimulus is maintained, rings slide over each other, effectively damping energy of stimulus
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13
Q

MAJOR UNIT

A

single somatic efferent (motor-neurone) & all muscle fibres it supplies

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14
Q

USES OF SKELETAL MUSCLE

A
  • movement (when one muscle contracts, other relaxes)

- heat genesis (as 80% wasted as heat energy)

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15
Q

MYOCYTE

A

single cell of muscle

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16
Q

TISSUE ENVELOPES OF SKELETAL MUSCLE

A
  • ENDOMYSIUM (surrounds myocyte) PERIMYSIUM (surrounds fascicle) EPIMYSIUM (surrounds all fascicles & also the neurovascular bundle)
  • neurovascular bundle binds nerves & veins with connective tissue
17
Q

APONEUROSIS

A

tissue sheet that takes place of tendon in flat muscles

18
Q

TENDON

A

tough band of fibrous connective tissue that brings together single contractions of myocytes to produce combined action at single point

19
Q

MYOFIBRILS

A
  • myocytes are made of myofibrils
20
Q

DARK V LIGHT BANDS

A

light bands are only actin but dark bands are overlap of actin & myosin

21
Q

PROCESS OF MUSCLE CONTRACTION IN MYOFIBRILS

A
  1. Neurotransmitter released from neuron & binds to receptors which depolarises membrane of muscle fibre in SR
  2. AP travels down T-tubules & opens calcium stores so CA2+ diffuses to myofibrils from reticulum (SR)
  3. CA2+ bind to troponin which causes tropomyosin molecule to move & expose myosin binding sites so myosin binds to actin on binding sites
  4. ATP hydrolysed to cause myosin heads to bend so actin pulled along & myosin remains attached until we attach ATP to each myosin head so it detaches from actin site
22
Q

CHARACTERISTICS OF MOTOR UNIT

A
  • each muscle cell supplied by only 1 motoneuron
  • muscle cells of motor unit randomly distributed throughout muscle so if certain number of muscle cells are active & contracts, the whole muscle does not just one side of it
23
Q

TETANIC CONTRACTION

A

muscles activated with very high frequency of stimuli to form tetanic (smooth) contraction not a jerking one like in single twitch or summation

24
Q

INTRAFUSAL MUSCLE FIBRE

A
  • Myocyte inside muscle spindle

- contract to change signalling of afferent nerves (update brain on muscle movement)

25
Q

EXTRAFUSAL MUSCLE FIBRE

A
  • myocyte outside of muscle spindle

- contract for movement

26
Q

TEST TO SEE RELATIONSHIP BETWEEN MOTOR NEURONE (A-NEURONE) & MUSCLE FIBRE

A

type S motoneuron was connected to type FF muscle fibre vice versa & the result was that FF changed biochem properties & became type S vice versa

27
Q

HOW WE HAVE PROPRIOCEPTION & KNOW LOCATION OF STIMULI

A

we code location and code where our receptors are to make maps of sensory space in our brain

28
Q

NMJ

A
  • synapse between motor neuron & muscle cell (NMJ is tuned for rapid transmission
  • many synaptic vesicles in active zone of presynaptic terminal (way more than usual)
  • junctional folds & lots of receptors in postsynaptic for more SA
29
Q

WHY NMJ ALWAYS WORKS

A
  • so many quanta (vesicles each containing hundreds of AcH molecules) released in presynaptic
  • junctional folds & lots of nACH receptors
30
Q

ROLE OF CA2+ IN EXCITATION-CONTRACTION COUPLING

A
  1. Ca2+ conc outside cell > inside so AP happens in presynaptic & depolarisation opens volatge gated Ca2+ channels
  2. Ca2+ enters presynaptic terminal & triggers vesicles to fuse with presynaptic membrane & release AcH in quota to synaptic cleft
  3. AcH binds to ionotropic nAcH receptors on postsynaptic (receptor has 2 AcH binding sites so 2 bind at a time)
31
Q

END PLATE POTENTIAL (EPP)

A
  • achieved when many EPSP collect together & depolarisation reaches threshold
  • initiates AP in muscle (regularly passes threshold as so many Na+ channels)
  • EPP decays as it moves away from end-plate (as nAcHR absent away from synapse)
32
Q

MYASTHENIA GRAVIS

A
  • autoimmune disease on nAcHR (so less of them at NMJ) identified by rolled back eyes (as leads to flaccid weakness of affected muscles (resp. failure is resp. muscles)
  • seen on graph as decreased muscle firing (as not enough receptors activated)
  • treated by giving AcH esterase inhibitors to prolong signal
33
Q

thin/thick filaments

A
  • thin filament made of actin (anchored to Z-line)
  • thick filament made of myosin (anchored at M-line (centre of sarcomere))
  • (sarcomere shortens from both sides when actin filaments slide along myosin filaments)

MEDICINE (27 decks)

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