Reflexes 3 Flashcards
what happens when the golgi tendon organ is put under increasing tension?
- more collagen fibres lock onto it, and stretch the type 1B sensory fibres
- this process increases the GP and speeds signal frequency
what is the function of golgi tendon organs?
- 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
what is the role of golgi tendon organs in a reflex arc?
to provide reflex inhibition to the motor neurons in the tendons in which they are located (their homonymous MNs) via a DISYNAPTIC
what happens when more alpha MNs are activated by CNS?
more muscles contract and more tension develops:
what happens as more tension develops, regarding GTOs?
GTOs increase their rate of firing and so increase the inhibition of alpha MNs - this consequently reduces tension in the muscle
what is skeletal muscle contraction a combination of?
- alpha MN mediated contraction (under control of CNS)
- gamma MN mediated spindle fibre contraction enabling accurate feedback
- GTO mediated inhibitory feedback to alpha MNs
what effect can damage have on reflexes?
- 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
what is rotatory nystagmus?
eye movements driven by moving visual images
what is post rotatory nystagmus?
eye movements driven by the movement of fluid in the semi-circular canals of the inner ear
what is an example of ocular reflexes?
- 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
how is focussing an image on the retina achieved?
by parasympathetic activity controlling the ciliary muscles of the eyes - they are responsible for changing the shape of the lens
what are example of cardiovascular reflexes?
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
the activation of baroreceptors (bp detectors) by increased blood pressure do what 2 things?
- depresses tonic sympathetic activity to arterioles causing dilation and so a drop in peripheral resistance
- increases vagal activity (parasympathetic) to the heart which decreases heart rate