Neurology Flashcards
What does an Axon do?
carries nerve impulses Away from the cell body
What does a Dendrite do?
carries nerve impulses towarD the body
What does the somatic NS do?
Controls superficial sensations and voluntary movements
What does the autonomic NS do?
Maintains visceral organ function
What does the somatic afferent NS do?
Responsible for sensing pain, temperature, and pressure
What does the somatic efferent NS do?
- Responsible for motor function
- Terminates at the neuromuscular junction of skeletal muscle
What does the autonomic afferent NS do?
- Involved in sensations of smell and taste
- Identification of distension or ischemia within tissues of organs
What does the autonomic efferent NS do?
Innervates cardiac muscles, and muscles of pharynx and larynx
What chemicals are released from vesicles in terminal ends of axons to activate or inhibit other impulses in dendrites of connecting neurons?
- Acetycholine
- Epinephrine
- Serotonin
Where does the spinal cord end in dogs?
L6-L7
Where does the spinal cord end in cats?
Variable: between L6 - sacrum
What are the actions of the 12 cranial nerves?
- Sensory
- Sensory
- Motor
- Motor
- Mixed
- Motor
- Mixed
- Sensory
- Mixed
- Mixed
- Motor
- Motor
What do the UMN and LMN do?
- Form a two neuron circuit that transmits motor impulses
- Both required for normal voluntary movement
What is an UMN?
Originates the cerebral cortex and travels down to the brainstem or spinal cord
What a LMN?
Begins in the spinal cord and innervates muscles and glands throughout the body
What are the 4 main PNS emergencies that can be seen?
All involve disruption of LMN communication with muscles
1. MG
2. Polyradic
3. Tick paralysis
4. Botulism
What is MG?
- The result of antibodies generated against the neurotransmitter acetylcholine’s receptors on a muscle’s surface at the neuromuscular junction
- Seen in both dogs and cats
What is the most commonly recognized polyneuropathy in dogs in North America?
Coonhound paralysis
What is polyradiculoneuritis?
- Suspected to be an immune mediate acute inflammation of multiple nerve roots and peripheral nerves in dogs
- Seen in both dogs and cats
What is botulism?
- A rapidly ascending motor paralysis
- Clostridium botulinum Type C
- Found in decomposing animal tissue
- Toxin prevents release of acetycholine at the neuromuscular junction, disrupting signals from LMN to the muscle
Where are the nerves of the SNS located?
T1-L4-5
C1-C5 neurolocalization
UMN signs to front and hind limbs
C6-T2 neurolocalization
- LMN signs to FL
- UMN deficits to HL
T3-L3 neurolocalization
- Normal thoracic limbs
- UMN deficits to rear limb
L4-S3 neurolocalization
- No deficits to thoracic limbs
- LMN deficits to pelvic limbs
What are signs of UMN disease?
- Increased muscle tone and nerve reflexes
- Lack of muscle atrophy
What are signs of LMN disease?
- Decreased muscle tone and nerve reflexes
- Muscle atrophy
What is the major determining factor of ICP?
The collective volume of intracranial contents
Schiff-Sherington posture indicates a legion in what area?
T2-L4
At what age does idiopathic epilepsy usually present?
6 months - 5 years
What breeds have a genetic predisposition to epilepsy?
- Aus shepherds
- Beagles
- Belgian shepherds
- Border collies
- GSD
- Standard poodle
- Goldens
- Labs
- Shelties
- Vislas
How is keppra metabolized?
Extrahepatic hydrolysis, mostly excreted unchanged by the kidneys
What is KBr’s MOA?
GABA receptor agonist
What BW changes can be seen with KBr adminstration?
False elevation of Cl
Why is KBr contraindicated in cats?
Potentially fatal pneumonitis
Why is it important to maintain a normal MAP in TBI patients?
TBI patients can lose the ability to autoregulate blood flow to their brain
What can hypercapnia lead to?
Vasodilation = increased ICP
What can hypocapnia lead to?
Vasoconstriction = decreased ICP
What clinical signs are seen as ICP rises?
- Compression alters PLRS
- Initially, disinhibition of LMN results in miosis
- As herniation occurs, pressure on LMN results in loss of function and mydriasis - pupils dilate and become non responsive
- Brain herniates through foramen magnum and causes decerebrate rigidity
What are spinal cord discs composed of?
- An outer fibrous material, the annulus fibrosus
- The AF is thinnest dorsally, just ventral to the spinal cord
- A jelly like inner material, the nucleus pulposus
What is the most common location for disc rupture?
T13-L1
What is spinal shock?
The loss of muscle tone and segmental spinal reflexes caudal to a severe cord injury
- Suspect with sudden return of reflexes
What breeds are predisposed to FCE?
- Shelties and miniature schnauzers
What diseases are associated with ischemic CVA?
- Hypothyroidism
- Idiopathic hyperlipoproteinemia (schnauzers)
- Neoplasma
- PLE/PLN
- Cushings
- HWD
- DM
- Sepsis
The presence of a brain hematoma initiates what?
Edema and neuroal damage in the surrounding parenchyma
What microorganism causes tetanus?
Clostridium tetani (gram pos anaerobic)
What occurs in tetanus?
- The toxin affects grey matter of brainstem and spinal cord
- Alterations to inhibitory pathways within the CNS leads to unopposed excitatory action and excess acetylcholine
- This results in rigidity of muscles
How does rabies reach the CNS?
- Virus replicates at the site of inoculation
- It then travels up the peripheral nerves to reach the CNS
- From there, spreads outwards via peripheral nerves to reach salivary glands and other organs
What is the incubation time of rabies?
Variable: 3 weeks to 6 months
When does death from rabies occur?
Within 7 days of the onset of CNS signs (both forms)
What does the vestibular system include?
Parts of the inner ear and brain that process sensory info with controlling balance and eye movement
What are the 3 major disease processes of vestibular disease?
- Idiopathic
- Inner ear
- Central
What type of nystagmus does idiopathic vestibular disease display?
Horizontal
How does inner ear disease cause facial paresis and/or Horner’s?
CN VII (facial) and sympathetic innervation to the eye travel through the petrous temporal bone surrounding the tympanic bulla
How do nasopharyngeal polyps cause vestibular disease?
They block the eustachian tube that drains the middle ear
What kind of nystagmus is seen with central vestibular disease?
Vertical
What does the peripheral vestibular system comprise of?
Inner ear sensors and vestibular cochlear nerve (CNVIII)
How does tick neurotoxin exert its effect?
The toxin interferes with the depolarization/acetylcholine release mechanism in the presynaptic nerve terminal
Cats appear resistant to which tick neurotoxins?
- Dermacentor
- Amyblomma
Where is D. variabilis found?
Wide distribution over eastern 2/3 of country + CA + OR
Where is D. andersoni found?
Only from the Cascades to the Rocky mountains
Where is A. americanum found?
Southern US distribution from TX & MO to Atlantic coast
Where is A. maculatum found?
Atlantic and Gulf of Mexico seaboards
Coonhound paralysis results in __?
Flaccid LMN tetraparesis that occurs over 4-5 days. Tail wag remains intact. No drugs have been effective in improving clinical signs
What is a brachial plexus injury?
Traumatically induced neuropathies of C6-T2 ventral spinal nerve rami
What is seen with cranial BPI?
- C6-C7
- Difficulty advancing limb at shoulder
- Shoulder instability
- Can usually bear weight and correct knuckling
What is seen with caudal BPI?
- C8-T2
- Inability to bear weight on thoracic limb
- Loss of carpal extension
- Proximal lesions can lead to Horner’s
- Hopping/knuckling/reflexes will be weak or absent
What is seen with complete BPI?
- Features of both cranial and caudal
- Analgesia to entire limb
What are the clinical signs of Horner’s Syndrome?
- Miosis (constricted pupil)
- Ptosis (eyelid drooping)
- Enophthalmos (retraction of globe)
- Protruding nictitans (elevated 3rd eyelid)
