QUESTIONS

1. Why do you see loss of proprioception before you see loss of motor deficits?
    
2. Describe the "extensor postural thrust" reaction.
    
3. What nerve is responsible for the patellar tendon tap reflex & from what spinal cord segments does this nerve arise?
    
4. Branches of the sciatic nerve are responsible for the cranial tibial reflex and the gastrocnemius reflex.  What are these branches?
    
5. What are the three main reflexes tested in the front limb & what nerves/spinal segments are responsible for them?
    
6. You are testing the withdraw reflex in a dog's rear leg.  Evidence of the perception of pain is noted but a crossed extensor reflex is noted in the leg opposite the one you are testing.
    
7. When you test the withdraw reflex, does it matter if you test medially, laterally, cranially or caudally?  (ie are you testing a different nerve in each location?)
    
8. What nerve is responsible for the perineal reflex?
    
9. List the cranial nerves in order.
    
10. What cranial nerves are being tested by the following popular reflexes (remember there is both an afferant & an efferent arc)
    
    a) menace
    
    b) pupillary light reflexes
    
    c) palpebral reflex
    
    d) corneal reflex
    
    e) doll's eye reflex
     
11. MIX & MATCH
    
    cerebellum & pons                         Telecephalon
    thalamus & hypothalamus            Diencephalon
    midbrain                                           Mesencephalon
    cerebrum & basal nuclei                metencephalon
    medulla oblongata                          myelencephalon
     
12. What spinal cord segments are included in the cervical intuminescence?  How about the lumbosacral intuminescence?
     
13. Which of the 5 senses does not have synapses in the thalamus prior to the cerebrum?
     
14. Motor neurons have cell bodies in the (choose one) dorsal/ventral horn.
     
15. A spinal nerve typically has 4 branches.  What are they & what are they for?
    
    
    
    
     

ANSWERS

1. Fibers carrying postural information of this nature are more superficial in the spinal cord than are motor fibers.  This means that compression from the outside of the cord pressing in (like a disc for example) affects cp fibers first.  Remember that cp stands for  "conscious" proprioception - a brain problem can also affect cp.  RECALL LESIONS BELOW THE MIDBRAIN ARE IPSILATERAL BUT ABOVE THE MIDBRAIN THEY ARE CONTRALATERAL.
   
   
   
   
    
2. Support the animal by the thorax so that the animal is standing upright (like a person) on its hind legs.  Lift the animal off the ground & lower the pelvic limbs to the floor.  The hind legs will move symmetrically caudally & will extend to support the body.  This is controlled by the vestibular apparatus but will also show asymmetry in coordination as will wheel barrowing.
   
   
   
   
    
3. The femoral nerve is responsible for the patellar tendon tap reflex.  It originates in spinal segments L4-L6.  This is the major weight bearing nerve of the rear leg; without the femoral nerve, the leg will not bear weight.  (Silly way to remember this:  The nerve you might get confused with is the sciatic L6-S1.  If you can remember "2-4-6-8 who do we appreciate" you can remember that 4,6 goes with the nerve we appreciate - the one that keeps us standing.)
   
   The patellar tendon tap reflex (also called the quadriceps reflex) is an example of a PHASIC response as opposed to a TONIC response.
   
   
   
   
   
    
4. The cranial tibial muscle flexes the hock via the peroneal nerve ( a branch of the sciatic) and the gastrocnemius muscles extends the hock via the tibial nerve.  Both these reflexes are considered somewhat difficult to elicit.  The sciatic nerve originates L5-S2.  The peroneal nerve = from L6-L7 & the gastroc nerve = L7-S1.
   
   
   
   
    
5. Extensor Carpi radialis reflex - extends the carpus via the radial nerve (C7, C8, T1)
   
   Triceps reflex - extends the elbow (essential for wt bearing) via the radial nerve -same origin as above.
   
   Biceps reflex - flexes the elbow via the musculocutaneous nerve (C6-C8)
   
   
   
   
    
6. A crossed extensor reflex is an upper motor neuron sign.  This indicates that the lesion is cranial to the sciatic segments L6-S1.  (How to remember that the sciatic comes from L6-S1?  Think of the word "sexy".  "Sciatic" begins with "SC" which sounds like "sexy."  Similarly 6-SI can be pronounced "sexy.")
   
   
   
   
    
7. Yes, when you test withdraws you are testing a different nerve branch depending on if you are testing the foot medially, laterally, cranially, or caudally.
   
   Medial=saphenous nerve (branch of the femoral)
   Lateral=tibial (sciatic branch)
   cranial=peroneal (sciatic branch)
   caudal=tibial (sciatic branch)
   
   In the foreleg:
   
   Medial=median & ulnar nerves (C8-T1)
   Lateral=ulnar nerve
   Cranial=radial (C7-T1)
   Caudal=ulnar nerve
   
   
   
   
    
8. The pudendal nerve is responsible for the perineal reflex.  This nerve originates in cord segments S123.  If this reflex is absent, the bladder may be expected to leak.
   
   
   
   
    
9. I = olfactory
   II = optic
   III = oculomotor
   IV = trochlear
   V = trigeminal
   VI = abducens
   VII = facial
   VIII = auditory
   IX = glossopharyngeal
   X = vagus
   XI = spinoaccessory
   XII = hypoglossal
   
   (Yes, there is an way to remember this but it is rated X.  If you want to know, you will have to E-mail me personally.)
   
   
   
   
    
10. a) menace - optic (II) & facial (VII)
    b) pupillary light reflexes - optic (II) & oculomotor (III)
    c) palpebral reflex - trigeminal (V) -nasally tests the ophthalmic branch, temporally tests the maxillary branch, & facial (VII)
    d) corneal reflex - trigeminal (ophthalmic branch) & facial (VII) & abducens (VI)
    e) doll's eye reflex - auditory (VIII) & oculomotor (III)
    
    
    
    
    
     
11. Cerebellum & pons                >>  Metenchephalon
    Thalamus & hypothalamus  >>  Diencephalon
    Midbrain                                  >>  Mesencephalon
    Cerebrum & basal nuclei       >>  Telencephalon
    Medulla oblongata                 >>  myelencephalon
    
    
    
    
     
12. The cervical intuminescence includes cord segments C5-T2.  The lumbosacral intuminescence includes spinal cord segments L4-S3.
    
    
    
    
     
13. Olfaction simply sends tracts right into the cerebrum.
    
    
    
    
     
14. Motor neurons have cell bodies in the ventral horn.
    
    
    
    
     
15. The dorsal branch - for afferent fibers returning to the cord with information
    The ventral branch - for efferent fibers
    The meningeal branch-
    The communicating branch - communicates info to the local autonomic ganglion.