NERVOUS SYSTEM Flashcards
Structural division
CNS
PNS
Functional division
Somatic Nervous system
Autonomic nervous system – sympathetic and
parasympathetic n.s
conducts sensory (afferent)
information from the periphery to the CNS. Sensory info
travels in ascending tracts from spinal cord (“lower”) to the
brain (“higher”)
Sensory (afferent) System
sensory fibers in the spinal cord that
travel toward the brain
Ascending Tracts
consists of motor (efferent)
nerves that conduct from higher to lower levels of the CNS
and from the CNS to the periphery
Motor (efferent) System
extend from the brain
down descending tracts in the cord to synapse on lower
motor neurons (LMN)
Upper Motor Neuron
extend away from the
spinal cord and brain to the muscles and glands of the
body
Lower Motor Neuron
bundles of upper motor neuron
fibers that move caudally in the spinal cord
Descending Tracts
Components of the nervous tissue
Components of the nervous tissue
Neuroglia
Neurons - its parts (cell body, nucleus and processes) and
classification
inflammation of a nerve
Neuritis
– allows diseases to differentially affect separate parts of the nerve cell.
Compartmentalization
– proliferate after brain damage, forming a
scar (gliosis). This can be detrimental, mechanically placing stress on the surrounding brain tissue, causing
irritation of adjacent tissue, and/or a possible epileptic focus
Astrocytes
A specialized site of apposition where information
passes from one nerve cell to another cell
Synapse
The first cell
Presynaptic Cell
Second Cell
Post synaptic Cell
Between the two cells
– synaptic cleft
– an electrical event that travels
down an axon
Nerve action potential
– the neuron that is transferring info to
the postsynaptic cell
Presynaptic cell
– the terminal end of the presynaptic nerve that is in apposition with the post synaptic cell; contains the synaptic vesicles
Synaptic button/knob
– membrane-bound organelles containing neurotransmitters located in the synaptic button
Synaptic vesicles
– a chemical substance within the
synaptic vesicle that mediates info transfer between
nerve cells and other cells at synapses; different sets of
neurons use different neurotransmitter
Neurotransmitters
– the neuron, muscle or gland
receiving info from the presynaptic cell
Postsynaptic cell
– integral protein inserted in the membrane of the postsynaptic cell; function to bind with a neurotransmitter, resulting in a change in the membrane of the post synaptic cell
Receptors
– the synaptic connection
between a neuron and muscular tissue where electrical
impulses pass from the neuron to the muscle cell; this
Neuromuscular junction
- nerve action potential propagates
down the axon to reach the synaptic knob; causes the synaptic vesicles to release their neurotransmitters into the synaptic cleft; the neurotransmitters diffuse across
the cleft to bind to receptors on the postsynaptic membrane; if the postsynaptic cell is a nerve, it can initiate or inhibit another nerve action potential in the
Synaptic event
CRANIAL NERVES- CLINICAL
– can be palpated and anesthetized
as it comes out of the infraorbital foramen
Infraorbital nerve
CRANIAL NERVES- CLINICAL
– can be palpated and anesthetized as it
comes out of the mental foramen
Mental nerve
CRANIAL NERVES- CLINICAL
can result in sensory deficit of the face and dropped jaw due to paralysis of the muscles of mastication
Injury to the trigeminal nerve
CRANIAL NERVES - CLINICAL
Injury to abducent nerve –
results in inability to gaze
CRANIAL NERVES - CLINICAL
can cause paralysis of the facial
nerve. This can cause loss of taste, facial paralysis and loss of lacrimation. Dogs have little vanity about their appearance, and the glossopharyngeal nerve also has taste
fibers, but without a functioning lacrimal gland or the orbicularis oculi muscle the eye can seriously dry up
MIDDLE EAR INFECTIONS
– cross the lateral
aspect of the masseter muscle. This can be injured, causing
facial paralysis [example, horse lying on a harness buckle
during surgery (buccal on buckle)]
Buccal branches of the facial nerve
– the facial nerve supplies
the motor component to the sensory component of the
trigeminal nerve. Pricking the face with a pin checks this
arc. If either nerve is paralyzed, then a twitch of the
muscles will not be elicite
Facial/trigeminal reflex arc
Damage to the glossopharyngeal nerve or vagus–
may cause difficulty in swallowing
– a zoonotic importance, causing hydrophobia
(fear of water, as in drinking) due to paralysis of the
pharynx (IX and X). With pharyngeal paralysis,
salivation or choke first think rabies!
RABIES
– common
in racehorses causing paralysis of the muscle that
opens the larynx (dorsal cricoarytenoideus), resulting
in a condition called “roaring”
Damage to the recurrent laryngeal nerve
causes paralysis
to the tongue’s muscles and unilateral damage causes
deviation of the tongue toward the normal side
Damage to the Hypoglossal Nerve
– anesthetize the mental nerve as
it comes out of the mental foramen to anesthetize the
lower chin
Mental nerve block
– injection at the mandibular foramen. The foramen is on the medial side of the mandible, opposite the points at which a line across the occlusal surface of the cheek teeth crosses a
perpendicular line from the caudal edge of the eye. Insert a 6” inch needle medial to the mandible straight up to this point and inject anesthetic. This anesthetizes
the lower lip but doesn’t get the incisors because those Fibers are internal. This block can be used when repairing lacerations of the lower lip
Mandibular alveolar nerve block
palpate the rostral end of the
facial crest. Run your finger dorsally to the infraorbital
foramen and palpate the nerve under the levator labii
superioris muscle. This block only anesthetizes superficial
structures from the point of the foramen to the lip.
Remember, nerves do not respect the midline, so do both
sides to anesthetize the middle of the upper lip. This can be
used when repairing lacerations on the lips or the bridge
of the nose. Injecting into the foramen one inch, which is
difficult, anesthetizes the face back to the orbit
Infraorbital Nerve Block
find the caudal angle of the eye
and palpate the notch in the lower part of the zygomatic
arch, just below the caudal angle of the eye. Pass the
needle under the notch and aim rostrally and ventrally to
anesthetize the maxillary nerve where it enters into the
maxillary foramen. This anesthetizes the upper cheek teeth
Maxillary nerve block
– palpate the foramen in the zygomatic process of the frontal bone. Inject a “bleb” of anesthetic over the foramen and rub it in. this anesthetizes the area over the forehead between the eyes. Do not inject into the foramen and thus the eyeball
Supraorbital Block
A region of the spinal cord from which a pair of spinal
nerves arise.
The last lumbar, the sacral, the caudal segments and the
end of the spinal cord are more cranial to the corresponding vertebrae
Spinal Segment
MENINGES-CLINICAL
– (G. hydro water + enkephalos brain) – an accumulation of cerebrospinal fluid in the brain’s ventricles due to obstruction of the flow of fluid. The blockade can occur in the cerebral aqueduct or the lateral apertures
Internal hydrocephalus
– an accumulation of CSF in
the subarachnoid space due to interference with absorption into the dural venous diseases
External hydrocephalus
EPIDUEAL ANESTHESIA-CLINICAL
– injection of a small volume of
analgesic into the epidural space at either the sacrocaudal (S5-
Ca1) or first intercaudal space (Ca1-Ca2). This inexpensive, simple
procedure is commonly performed on cows, sheep and goats for
obstetrical manipulations and surgeries involving the tail, anus,
rectum, vulva, perineum, and prepuce. Just enough analgesia to
block the sacral and caudal nerves is needed. If
Caudal epidural analgesia
ANESTHESIA FOR ABDOMINAL SURGERY-CLINICAL
– opening the paralumbar fossa to deal with such problems as “hardware disease”, dystocia, displaced abomasum, etc. the first three or four ventral lumbar nerves and the
last thoracic nerve are anesthetized in flank surgery of horse and ox
Standing flank surgery in the ox
ANESTHESIA FOR ABDOMINAL SURGERY-CLINICAL
concerned with T13, L1 and L2 nerves and can be done in a number of ways
Local/Regional anesthesia for a flank surgery –
– injections are done in the abdominal wall, from the subcutaneous area to the peritoneum
Inverted L block
ANESTHESIA FOR ABDOMINAL SURGERY-CLINICAL
Local/Regional anesthesia for a flank surgery
• ____________– block all branches of the spinal nerves
• Proximal Paravertebral anesthesia (Farquharson, Hall or
Cambridge Technique)
• Distal paralumbar anesthesia (Magda,
Cakala or Cornell Technique)– blocks only the ventral and lateral and dorsal branches of the spinal nerves
Paravertebral block
