Nervous System 1 Flashcards
Central nervous system
Brain and spinal cord (dorsal and tubular vertebrae)
Peripheral nervous system
Sensory afferent
- exteroreceptor (outside skin)
- interoreception (internal organs)
- proprioception (limb position)
Motor efferent
- autonomic to internal organs (soma and viscera) and blood vessels
- somatic motor to skeletal muscle
How else can you categorise the NS
Where they are located
1- spinal nerves have 30 pairs
2- cranial nerves exit brain - 12 pairs N.X vagus parasympathetic inner ages most thoracic and abdominal organs
Development and segmentation of neurons
Ganglia/cell bodies inside or outside the CNS
- cell bodies inside cns > develop from the neural tube e.g. motor, preganglionic and autonomic neurons
- ganglia outside cns > develop from neural crest e.g. sensory and post ganglionic neurons
Development from embryonic somite and segmentation
Each spinal nerve induced to grow by embryonic somite which follows it as it forms muscle and dermis
> nerve climbs through sclerotome to reach myotome= segmental > vertebrae are parasegmental
- Skin is innervated in dermatome stripes but the dermatomes overlap
- Muscles are innervated by nerves to their myotome of origin but many muscles are derived from more than one myotome e.g. triceps
Plexi
Adjacent spinal nerves are tangled ad mix soon after leaving the vertebral column to form this
Spinal nerve numbering
Each intervertebral notch carries 1 spinal nerve
NO SPINAL NERVES ARE Cd 4567
C1 is motor only and exists lateral foramen of atlas
Cervical nerve numbering (exception)
7+1C … discovery of an 8th cervical nerve, these C nerves emerge cranial to the like number vertebra, others emerge caudal to it
Regional variation - cervical nerves 1-5
*** phrenic nerve
Each innervate segmental spinal muscles
- Some of them join cranial nerve XI to innervate cranial mm of TBJ
- c1 is motor only to c2 sensory to skin of caudal head/medial ear
- c5-7 join to form PHRENIC NERVE to join the diaphragm - reflects cephalon embryonic origin of that muscle
Brachial plexus - C6-T2
- HYPAXIAL RAMI mingle to form brachial plexus which goes to innervate dozen nerves of the forelimb
- plexus lies deep to scapula
- all limb muscles form from hypomere part of myotome > subdivides into dorsal and ventral groups within the limb
Brachial plexus c6-t2 injuries
- horses strike scapula on gate posts or wear ill fitting fraught collars > damages suprascapular nerve
- Sweeny = autotrophy of supraspinatus and infraspinatus
- damage to radial nerve if lat elbow hit by car, humeral fracture, prolonged recumbency in horses
- horses can stand if damage distal to the innervation of triceps
Interappendicular spine T3-L3
- T3-T12 innervate spinal segments and intercostal spaces - run in caudal groove on each rib
- T13-L3 provide sensory innervation to the flank
Lumbosacral plexus L4-S2
- hypaxial rami mingle as the LUMBOSACRAL PLEXUS > gives rise to 5 main nerves of hind limb
- as cattle give birth > fetus rubs against obturator nerve > paralysis of nerve > down cow syndrome
V-tail S3-Cd4-7
- nerves innovate segmental mm of the tail
- tail has extrinsic sagittal flexor and extensor mm with long tendons: med+lat, dors+vent, sacrocaudials
- intrinsic mm - continuation of transverspinales
Clinical aspects
- Diagnostic nerve blocks
- Local analgesia for surgery e.g. ruminant flank T13-L3
- Nerve disease e.g. myastheria gravis
- Accidental iatrogenic injury e.g. previously mentioned nerve injuries + IM injections near sciatic nerve
- Spinal cord injury: dependent on severity of damage, cranial-caudal location along cord
