Cranial and Peripheral Nerves Principles of anatomy-ANSC 2202 Fall 2006.
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Transcript of Cranial and Peripheral Nerves Principles of anatomy-ANSC 2202 Fall 2006.
Cranial and Peripheral Nerves
Principles of anatomy-ANSC 2202
Fall 2006
Somatic motor neurons (efferent)
Somatic sensory neurons (afferent)
Central Nervous System = brain + spinal cord
Peripheral Nervous System = cranial + spinal nerves
Nervous System
Skeletal
muscles Parasympathetic NS (rest& digestion):Pelvic nerves+Cranial III, VII,IX,X
Sympathetic NS (fight or flight):all spinal and most cranial nerves
Skin, muscles, tendons, bones
Smooth muscles, heart, glands
Autonomic motor neurons (efferent)
Autonomic sensory neurons (afferent)
Smooth muscles, heart, glands
voluntary involuntary
Special sensory fibersCn I,II,VII, VIII, IX
Taste, smell, vision, hearing
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
Central nervous system
The Brain: sagittal section of a sheep’s brain: A review
Links the 2 hemispheres
Cerebral cortex:•Thought •Voluntary movement •Language •Reasoning •Perception
•Movement •Balance •Posture Brain stem=area of the brain
between the thalamus and spinal cord:•Breathing . Heart rate, Blood Press
•Vision •Audition •Eye Movement •Body Movement
Circadian rythm
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
The spinal cord
The spinal cord
The spinal cord
Spinal reflexes
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
Peripheral nervous system
PNS: Cranial nerves(12 pairs)
Cranial nerve 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 S
III Oculomotor M
IV Trochlear M
V Trigeminal B
VI Abducens M
VII Facial B
VIII Vestibulocochlear S
IX Glossopharyngeal B
X Vagus B
XI Spinal Accessory M
XII Hypoglossal M
Function of cranial nerves
I 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
Cranial nerves: origin
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!!
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
Somatic nervous system (skeletal muscles)
Autonomic nervous system: organization
Autonomic nervous system: organization
Differences between sympathetic and parasympathetic (autonomic nervous system)
Autonomic nervous system: targets
Autonomic nervous system: targetsSympathetic 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 Decreases Increases
Liver Increases blood sugar
None
Adrenal medulla Stim.secretion none
Penis Ejaculation Erection
Some important spinal nerves (pig)
Some important spinal nerves (human)
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
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,…
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