Nervous System

the nervous system

a communication network that enables an animal to adjust itself or its part to changes in the external and internal environment

Sensory components

to detect environmental changes

Integrative components

to process the sensory data coupled the information stored /acquired

Motor components

to provide a response to the processed information

neurons

the basic working unit of the brain, a specialized cell designed to transmit information to other nerve cells, muscle, or gland cells

Glia 

non-neuronal cells that maintain homeostasis, form myelin, provide support/ protection for neurons

synapses

to transfer electric activity (information) from one cell to another

neurotransmitter

chemical messenger

The central nervous system

brain, brain stem, spinal cord

Autonomic nervous system

regulates involuntary body processes

Somatic nervous system

controls voluntary movement

sympathetic nervous system

prepares the body for stress reactions

parasympathetic nervous system

calms the body

Cerebrospinal fluid

a clear fluid present in the ventricles (core cavities) of the brain, in the central canal that runs through the core of the spinal cord, and in the subarachnoid space that surrounds the entire outer surface of the brain and spinal cord

the ventricle

a series of interconnected cavities in the core of the brain that have an ependymal cell lining and are filled with CSF; CSF is formed by the choroid plexus of the lateral ventricles

lateral ventricle 

located in the 2 cerebral hemispheres

third ventricle

at the midline of the diencephalon

fourth ventricle

between the cerebellum and the dorsal surface of the hindbrain

CSF functions

– to cushion the brain

– source of nutrition for the brain

– excretion of metabolic waste products

– control of chemical environment

– regulation of intracranial pressure

the blood-brain barrier

a diffusion barrier, which impedes influx of most compounds from blood to brain; the selective nature of CNS blood vessels with respect to the materials that can move across their walls, compared with blood vessels in other parts of the body; how the brain is protected from potentially harmful neuroactive chemicals in the blood, and why it is difficult to deliver certain drugs effectively to the brain

myelography

injection of radiopaque dyes into the CSF of the subarachnoid space; the dye is introduced using a needle, then the dye outlines the spinal cord and identifies any structure deforming it, such as a disc herniation; often used in conjunction with computerized tomography

Hydrocephalus (HC) -congenital-

obstruction of the flow of CSF

medical treatment for HC

↓ CSF volume and production but offers only temporary palliation of clinical signs and shunting CSF into another cavity

seizure

A sudden, electrical discharge in the brain causing alterations in behavior, sensation, or consciousness

epilepsy  

is a chronic disorder, the hallmark of which is recurrent, unprovoked seizures

Seizures seen in epilepsy are cause by

disturbances in the electrical activity of the brain

types of seizures

generalized seizure

partial seizure

pre-ictal

the start of a seizure 

ictus

the stroke or attack, ictus is another word for the physical seizure

post-ictal

after the attack, postictal refers to the aftereffects of the seizure, e.g., arm numbness, loss of consciousness, partial paralysis, etc

narcolepsy

when an animal suffers from excessive daytime sleepiness, lack of energy, or brief losses of consciousness (sudden collapse and loss of movements); episodes are brief and go away by themselves

cataplexy

sudden muscle paralysis without loss of consciousness; the animal remains alert and can follow movement with its eyes throughout the episode; cataplexy is similar to narcolepsy in that the episodes are spontaneous, brief, and reversible

Chiari-like malformation (CM) and syringomyelia

are components of a structural central nervous system disease syndrome that primarily affects Cavalier King Charles spaniels (CKCS) and other small-breed dogs, as well as cats (e.g., Persian)

Syringomyelia

a disorder of CSF which can occur when there is obstruction of flow of the fluid from the ventricles in the brain to around the spinal cord; fluid is forced or sucked into the spinal cord resulting in dilated fluid filled cavities

A syrinx

a fluid-filled cavity within the spinal cord

The most common symptoms (CM-affected dogs)

vocalization, head scratching or head rubbing, reduced activity, behavioral changes, touch aversion

horners syndrome

A common neurological disorder of the eye and facial muscles, caused by dysfunction/disruption of the sympathetic nervous system; suddenly, without warning

myasthenia gravis

A condition resulting from a deficiency of acetylcholine (ACh) receptors on the postsynaptic membrane → muscle weakness abnormal transmission of the message between the nerves and the muscles

congenitial MG

hereditary disorder resulting in deficiency of ACh receptors on the postsynaptic membrane

Acquired (immune-mediated) MG

antibody mediated destruction of ACh-receptors; the immune system is destroying neuromuscular junctions; pathogenesis unknown.

tensilon test

A clinical test used to presumptively diagnose MG, while awaiting results of the AChR-antibody test