Reflexes

Question 1

<p>What is the simplest reflex?</p>

Answer 1

<p>The stretch reflex</p>

Question 2

<p>Where is the stretch reflex found?</p>

Answer 2

<p>In all muscles</p>

Question 3

<p>What are examples of the stretch reflex?</p>

Answer 3

<p>Pattelar tendon</p>

<p>Knee jerk reflex</p>

Question 4

<p>What does the stretch reflex use?</p>

Answer 4

<p>Information from muscle spindles which monitor muscle length</p>

Question 5

<p>What is the stretch reflex?</p>

Answer 5

<p>Follows a sharp tap to an inelastic tendon</p>

Question 6

<p>What is the process of the stretch reflex?</p>

Answer 6

<ol> <li>Force is transmitted to muscle fibres</li> <li>Stretch activates sensory nerves in muscle spindles</li> <li>Increases the numbers of action potentials in afferent nerves projected through the dorsal horn into the spinal cord</li></ol>

Question 7

<p>What are the three connections that the spindle sensory afferent devides into?</p>

Answer 7

<ol> <li>Activates alpha motor neurons to the muscle which was stretched (rapid contraction of the agonist muscle)</li> <li>Connects indirectly with and influences the antagonist muscle (agonist muscle relaxes, stretches)</li> <li>Dorsal columns and makes connection in the somatosensory cortex (tells the brain about the length of the muscle)</li></ol>

Question 8

<p>During the stretch reflex, what kind of loop is the activation of the alpha motor neurons to the stretched muscle?</p>

Answer 8

<p>Monosynaptic reflex that is a negative feedback loop</p>

Question 9

<p>During the stretch reflex, why does the antagonist muscle relax when the agonist muscle contracts?</p>

Answer 9

<p>Spindle afferent activates inhibitory interneurons which stop the activation of alpha motor neurons to the antagonist muscle</p>

Question 10

<p>What is the inverse stretch reflex?</p>

Answer 10

<p>Caused by afferent neuron from golgi tendon organs</p>

<p>Muscle contracts and shortens</p>

<p>Pulls on tendon and I_bsensory nerves from the GTO increases firing of APs</p>

Question 11

<p>What is the process of the inverse stretch reflex?</p>

Answer 11

<ol> <li>Activation of inhibitory interneurons to agonist muscle (decrease in contraction strength)</li> <li>Activation of exitatory interneurons to antagonist muscle</li> <li>Information sent through the dorsal column to somatosensory complex</li></ol>

Question 12

<p>What is the inverse stretch reflex also called?</p>

Answer 12

<p>Clasp knife</p>

<p>Golgi tendon organ reflex</p>

Question 13

<p>What does the inverse stretch reflex prevent?</p>

Answer 13

<p>The inverse stretch reflex prevents the muscle form contracting so hard that the tendon insertion is torn away from the bone</p>

Question 14

<p>What is the flexor (withdrawal) reflex?</p>

Answer 14

<p>Uses information from pain receptors</p>

<p>Withdraws part of the body away from pain stimuli</p>

Question 15

<p>How does the flexor reflex happen?</p>

Answer 15

<p>Increased aciton potentials cause:</p>

<ol> <li>Increased activity in flexor muscles (excites more neurons)</li> <li>Antagonistic extensors are inhibited at the same time by a number of exitatory and inhibitory reflexors</li> <li>To prevent you falling over extends to the contralateral limbs by excitatory interneurons cross spinal cord excite the contralateral extendors</li> <li>At the same time inhibition of contralateral flexors</li> <li>Sensory information goes to the brain in the contralateral spinothalamic tract</li></ol>

Question 16

<p>What can you say about spinal segments involved in the flexor reflex?</p>

Answer 16

<p>Neurons branch a lot and so activate interneurons in several spinal segments, allowing the control of many muscle groups</p>

Question 17

<p>Is the reaction of the flexor reflex quicker at the source or contralateral limbs?</p>

Answer 17

<p>Slower at the contralateral limbs due to the time taken to travel through so many interneurons</p>

Question 18

<p>How can reflexes be overridden?</p>

Answer 18

<p>Consciously</p>

Question 19

<p>What is an example of consciously stopping a reflex?</p>

Answer 19

<p>If excessive load is placed on a muscle, the GTO reflex is activated causing muscle relaxation and the load to be dropped, but this can be consciously stopped</p>

Question 20

<p>How is it possible to consciously stop a reflex?</p>

Answer 20

<p>A motor neurons recieve more than 10000 synapses</p>

<p>Integration of EPSP and IPSP</p>

<p>Voluntary excitation of alpha motor neurons can overide inhibition from GTO to maintain contraction</p>

Question 21

<p>How can the stretch reflex be overridden?</p>

Answer 21

<p>Decending inhibition hyperpolarises alpha motor neurons</p>

<p>Stretch reflex cannot be evoked</p>

Question 22

<p>What does activation of gamma motor neurons depend on?</p>

Answer 22

<p>Decending pathways</p>

Question 23

<p>What are clinical uses of reflexes?</p>

Answer 23

<p>Assessing spinal cord localisation of a problem (reflex works above but not below the point of damage)</p>

Question 24

<p>What can you say about the spinal segments involved in the stretch reflex?</p>

Answer 24

<p>Stretch reflex is highly localised so only affects alpha motoneurons at one or two spinal segments</p>

Question 25

<p>What can you say about the spinal segments of the withdrawal reflex?</p>

Answer 25

<p>Diffuses and spreads to several spinal segments</p>

Question 26

<p>What is facillitation?</p>

Answer 26

<p>Spreads to many spinal cord segments to allow a quicker response</p>