Reflexes 3 Flashcards

1
Q

what happens when the golgi tendon organ is put under increasing tension?

A
  • more collagen fibres lock onto it, and stretch the type 1B sensory fibres
  • this process increases the GP and speeds signal frequency
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2
Q

what is the function of golgi tendon organs?

A
  • they monitor tension in muscle because they are in series with the muscle fibres
  • they compliment the info from the muscle spindles in CNS
  • in extreme conditions, protect the muscle and tendon from damage
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3
Q

what is the role of golgi tendon organs in a reflex arc?

A

to provide reflex inhibition to the motor neurons in the tendons in which they are located (their homonymous MNs) via a DISYNAPTIC

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4
Q

what happens when more alpha MNs are activated by CNS?

A

more muscles contract and more tension develops:

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5
Q

what happens as more tension develops, regarding GTOs?

A

GTOs increase their rate of firing and so increase the inhibition of alpha MNs - this consequently reduces tension in the muscle

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6
Q

what is skeletal muscle contraction a combination of?

A
  1. alpha MN mediated contraction (under control of CNS)
  2. gamma MN mediated spindle fibre contraction enabling accurate feedback
  3. GTO mediated inhibitory feedback to alpha MNs
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7
Q

what effect can damage have on reflexes?

A
  • if the component parts of the reflex arc are damaged, clearly the reflex will change in character and for
  • damage to the peripheral nerves can cause a reduction or loss of reflex responses
  • damage to pathways from brain can cause some reflexes to become exaggerated
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8
Q

what is rotatory nystagmus?

A

eye movements driven by moving visual images

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9
Q

what is post rotatory nystagmus?

A

eye movements driven by the movement of fluid in the semi-circular canals of the inner ear

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10
Q

what is an example of ocular reflexes?

A
  • when alarmed or excited, activity in sympathetic nervous system causes activation of the radial muscles of the iris which dilate the pupil
  • parasympathetic neurons innervating the pupil constrict the pupil
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11
Q

how is focussing an image on the retina achieved?

A

by parasympathetic activity controlling the ciliary muscles of the eyes - they are responsible for changing the shape of the lens

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12
Q

what are example of cardiovascular reflexes?

A

blood pressure determined by cardiac output and peripheral resistance of vascular beds:

SNS increases:

  • heart rate as well as force of constriction
  • peripheral resistance by constricting small arterioles

PNS reduces:
- heart rate but has less of an effect of peripheral resistance than the sympathetic system

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13
Q

the activation of baroreceptors (bp detectors) by increased blood pressure do what 2 things?

A
  1. depresses tonic sympathetic activity to arterioles causing dilation and so a drop in peripheral resistance
  2. increases vagal activity (parasympathetic) to the heart which decreases heart rate
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