1. Cranial and Peripheral Nerves
Principles of anatomy-ANSC 2202
Fall 2006

2. Central Nervous System = brain + spinal cord
Peripheral Nervous System = cranial + spinal nerves
Skin, muscles, tendons, bones
Smooth muscles, heart, glands
Taste, smell, vision, hearing
voluntary
involuntary
Somatic sensory neurons (afferent)
Somatic motor neurons (efferent)
Autonomic sensory neurons (afferent)
Autonomic motor neurons (efferent)
Special sensory fibers
Cn I,II,VII, VIII, IX
Smooth muscles, heart, glands
Parasympathetic NS (rest& digestion):
Pelvic nerves+Cranial III, VII,IX,X
Skeletal muscles
Sympathetic NS (fight or flight):
all spinal and most cranial nerves

3. Types of neurons in the PNS
Cranial - connects the brain with the periphery
Sensory (afferent) - carry information INTO the CNS from sense organs
Motor (efferent) - carry information away from the CNS (for muscle control).
Spinal - connects the spinal cord with the periphery:
Somatic - connects the skin or muscle with the CNS; afferent and efferent
Autonomic - connects the internal organs with the CNS; afferent and efferent

4. Central nervous system

5. The Brain: sagittal section of a sheep’s brain: A review
Cerebral cortex:
Thought
Voluntary movement
Language
Reasoning
Perception
Circadian rythm
Vision
Audition
Eye Movement
Body Movement
Links the 2 hemispheres
Movement
Balance
Posture
Brain stem=area of the brain between the thalamus and spinal cord:
Breathing . Heart rate, Blood Press

6. The spinal cord
Extension of brain stem starting at the foramen magnum and ending at:
L1 in humans (extension of pia matter attaches to coccyx)
S2 in animals
2 roles:
Transmission of nerve impulses (white matter-axons; grey matter-nuclei)
Spinal reflexes

7. The spinal cord

8. The spinal cord

9. The spinal cord

10. Spinal reflexes

11. Damages to the Central Nervous System
Brain does not regenerate
Spinal cord:
If severed: function below the lesion will not be restored
Babinski (extensor toe) reflex: withdrawal = chronic spinal cord lesion
Patellar (knee-jerk) reflex: no kick = femoral nerve and/or segment of spinal cord L4-6
Partial damage: may recover but stagnates after a certain period

12. Peripheral nervous system

13. PNS: Cranial nerves (12 pairs)
Nerve type (Sensory, Motor, Both) I
Olfactory S
“On Old Oklahoma’s Towering Tops a Fine Vet Gastroenterologist Viewed Some Horses”
“Six Sailors Made Merry But My Brother Said Bad Business My Man” II
Optic
III
Oculomotor M IV
Trochlear V
Trigeminal B VI
Abducens
VII
Facial
VIII
Vestibulocochlear IX
Glossopharyngeal X
Vagus XI
Spinal Accessory
XII
Hypoglossal

14. Function of cranial nerves
Olfactory Nerve: sense of smell II
Optic Nerve: vision
III
Oculomotor Nerve: eye movements, pupillary constriction and  accommodation, eyelid muscles IV
Trochlear Nerve: eye movements V
Trigeminal Nerve: somatic sensations from face, mouth, cornea; muscles of mastication (chewing) VI
Abducens Nerve: eye movements
VII
Facial Nerve: controls the muscles of facial expression, taste from anterior tongue, lacrimal (tears) and salivary glands
VIII
Auditory/Vestibular Nerve: hearing, sense of balance IX
Glossopharyngeal Nerve: sensation from pharynx, taste from posterior tongue, carotid baroceptors X
Vagus Nerve: autonomic functions of gut, sensation from pharynx, muscles of vocal cords, swallowing XI
Accessory Nerve: shoulder and neck muscles
XII
Hypoglossal Nerve: movements of tongue

15. Cranial nerves: origin

16. Damage to the cranial nerves
Pupillary light reflex: oculomotor nerve: flash light in right pupil: right pupil should constrict more
Corneal and palpebral (eyelid) reflexes (state of anesthesia): trigeminal nerve: blink before touching eyelids (ophtalmic branch); retraction of ocular globe when touch cornea (maxillary branch)
Reaction to smell (link with appetite): olfactory nerve (see experiment with Boar Mate)
Torticollis: spinal accessory nerve: neck muscles innervation
Pharynx paralysis: glossopharyngeal and vagus nerves: rabies!!

17. PNS: Spinal nerves (31 pairs; don’t need to identify them all)
Anatomy:
Emerges from dorsal and ventral roots
Emerges through intervertebral foramen (except 1st spinal nerve)
Somatic and autonomic systems

18. Somatic nervous system (skeletal muscles)

19. Autonomic nervous system: organization

20. Autonomic nervous system: organization

21. Differences between sympathetic and parasympathetic (autonomic nervous system)

22. Autonomic nervous system: targets

23. Autonomic nervous system: targets
Sympathetic
Parasympathetic
Eye
Dilates pupil
Constricts pupil
Salivary glands
Dry mouth (thick saliva)
Lots of dilute saliva
Heart rate
Increases
Decreases
Lungs (bronchi)
Dilates
Constricts
GI activity
Liver
Increases blood sugar
None
Adrenal medulla
Stim.secretion
none
Penis
Ejaculation
Erection

24. Some important spinal nerves (pig)

25. Some important spinal nerves (human)

26. Damages to peripheral nerves
Sciatic nerve pinched: lower back pain
Foot nerves: 90% of all lameness in horses. Heel, pastern/foot and fetlock blocks should identify damage; if not, work way up he limb.
Knee-jerk reflex

27. Conclusion CNS: brain + spinal cord PNS: cranial+ peripheral nerves:
Somatic nervous system: skeletal muscle control
Autonomic nervous system: smooth and cardiac muscle. Sympathetic/parasympathetic and fight/flight reactions
Neurological exams: non invasive, symptoms often specific to one type of lesion
To suspect if pain does not originate in muscles, tendons,…

28. The end Stations Knee-jerk reflex Pupillary light reflex
Palpebral reflex
Spinal cord model
Fetal pig, dissect:
Vagus and sciatic nerves
Brain
Handout
- Table of cranial nerves (with function and type-sensory or motor or both)
Answer the vignettes
Sympathetic/parasympathetic actions