Reflexes 3

Question 1

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

Answer 1

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

Question 2

what is the function of golgi tendon organs?

Answer 2

• 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

Question 3

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

Answer 3

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

Question 4

what happens when more alpha MNs are activated by CNS?

Answer 4

more muscles contract and more tension develops:

Question 5

what happens as more tension develops, regarding GTOs?

Answer 5

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

Question 6

what is skeletal muscle contraction a combination of?

Answer 6

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

Question 7

what effect can damage have on reflexes?

Answer 7

• 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

Question 8

what is rotatory nystagmus?

Answer 8

eye movements driven by moving visual images

Question 9

what is post rotatory nystagmus?

Answer 9

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

Question 10

what is an example of ocular reflexes?

Answer 10

• 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

Question 11

how is focussing an image on the retina achieved?

Answer 11

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

Question 12

what are example of cardiovascular reflexes?

Answer 12

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

Question 13

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

Answer 13

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