Control center for the brain

-Receive stimuli, analyze and integrate it, and respond

-External: Touch, vision, hearing, smell

-Internal: Pain, hunger

#Tetanus toxins bind to nerve endings

CNS: Brain and spinal cord (foramen magnum)

PNS: Nerves off the CNS

• SNS-Voluntary Actions
• ANS-Vital Functions, HB, HR, unconsious

                -PS/S: Fight or flight

IN, ADMISSION

Neurons send input FROM muscle TO brain

EXIT

Neurons send signal FROM brain TO muscle to contract

Neuron: Individual cell

Nerve: Bundle of cell processes

Ganglion: Group of nerve cell bodies outside the CNS

Cytoplasmic projections

AFFERENT

Usually only one

EFFERENT

Lipoprotein made by Schwann cells, wrap around axon

White, insulating, allows for faster nerve impulse, nerve impulse jumps

#When puppies/kittens born, not completely myelinated

Nutrient and oxygen suppy for myelin, at 1mm intervals

Gated sodium channels

Electrical phenomena, impulse changes charge and alters relationship between negative cell contents and positive membrane

2 Na+ goes out, 1 K+ goes in

Repolarization->Refractory period

All or nothing response

Number of impulses

Number of neurons

Type of neuron

#Nervous symptoms of eclampisa in the bitch and milk fever in the cow are caused by low levels of calcium in the blood, affecting the transmission of nerve impulses

Vessicles filled with neurotransmitters

When depolarization reaches vessicles, they release their neurotransmitters into synaptic cleft, post synaptic membrane has receptors: vessicles merge with cell membrane

Lots of mitochondria/ADP

Synthesized in rough ER of neuron

Excitatory or inhibitory

Amino acids

Peptides

Monoamines

Acetylcholine

Acetylcholine

1st to be discovered, @ motor end plate

In CNS/PNS

Neurons that release ACh

Inactivated by acetylcholinesterase: bradycardia, hypotension, hypersecretion

SNS: Nor/Epinephrine

Brain: Dopamine

Effects: fight or flight, increased HR, strength of contraction, peripheral vasoconstriction, blood shunted to skeletal muscles, liver, brain, increased blood glucose, metabolic rate, bronchodialation, pupillary dilation

GABA(brain) and Glycine(spine)

Opens chloride channels resulting in hyperpolarization of membrane of post-synaptic neuron

Diazepam acts of GABA receptors

Ivermectin increases GABA release

Function: control and coordinate activities of the body

Grey matter: outside unmyelinated

White matter: inside, myelinated

TELencephalon (cerebrum

DIEencephalon

MESencephalon

METencephalon (pons/cerebellum)

MYELencephalon (medulla)

TELL DI, MES MET MYEL

90% of neurons, largest portion of brain

Right/Left hemispheres, divided by median fissure, connected by corpus callosum

Higher brain functions: sensory input, voluntary motor, memory storage

Acts as link between endocrine and nervous system

Helps to control ANS

Major influence on homeostasis: thirst, hunger, fluid, osmotic balence

Optic Chiasma: How nerve impulses from each eye reach opposite side of brain

Pituitary Gland: Endocrine gland

Olfactory bulbs: Sense of smell

"Little Brain," deep fissures, grey matter (furkinje cells)

Coordination, balence, movement, fine adjustments

Input from skeletal muscles, visual receptors, and vestibular receptors

#Injury or malformation results in incoordination and spasticity, can't walk in coordinated fashion: Cerebellar hypoplasia

Forms bridge between cerebellar hemispheres

Connections between spinal cord and brain

Works with medulla to regulate breathing

Origin of several cranial nerves

Connects the pons to the spinal cord

Reflex centers for HR, force of contraction, vasomotor, breathing rhythem, sneezing, swallowing

Hollow neural tube of embro, lumen develops into canals, filled with CSF, also surrounds brain

Chroid plexus, clear no protein

Capillary network, produces CSF

Samples can be collected from cisterna magna

Dura Mater-Outermost: tough fibrous CT, continuous with periosteum of skull, seperated by epidural space

Arachnoid-Middle: collagen fibers and large BV that supply adjacent NT with nutrients, CSF circulates here, subarachnoid space

Pia Mater-Innermost: Delicate membrane, closely adheres to brain

Systemic circulation has limited access to CNS

Capillaries have tighter junctions, surrounded by glial cells

Limits passage of many substances

Anything that does go in must be in lilpophilic form

Cerebrospinal Fluid

Clear, circulates within ventricles, cavaties surrounding brain and spinal cord, secreted by choroid plexus

Supploes nutrients/cushions brain

No RBC, few lymphocytes, limited protein

Exchanges nutrients and waste with interstitial fluid

Mechanical-Touch

Thermal-Heat/cold

Electromagnetic-Light

Chemical-Electrolyte, oxygen

Exteroceptors: On/Near body surface

Proprioceptors: In muscle, tendon, joints

Interceptors: W/I organs, other tissues

Interior environment

Hunger, thirst, distention

Poorly localized

Difficult to seperate

Different receptors for light and heavy pressure

Accomodatio to repeated stimulation is rapid

Internal and external

Central receptors monitor body temp.

Superficial receptors monitor body temp. on body surfaces

Proprioception

Body's awareness of where the various parts are

Mainly unconscious

Stretch receptors in muscles, tendons, joint capsules

Input integrated by CNS, used to make fine adjustments

Nociceptors, most common sensory receptor

Simple nerve endings which respond to intense stimuli, protective function

Classified by location (superficial, deep, visceral) and duration (acute, chronic)

Upper/Lower eyelids

Inner surface protected by Meibomian glands

Blink useful for detecting depth of anesthesia

Tear duct, glands that produce tears

Cornea needs to be kept hydrated, film needed to protect

Distributed by eyelids, drains through tear ducts and clogs easily, nasolacrimal duct

Muscous, lipids, antimcrobial secretions

Membranes lining anterior portion of sclera, eyelids

Bulbar and Palpebral

Usually pink

White of the eye, dense fibrous CT and elastic fibers

Protects and maintains eye shape

Avascular

Primarily collagen, laters, corneal epithelium

Clear to admit light, controlled water content

Corneal edema/dehydration will cause clouding

High number of receptors

Next layer after sclera, vascularized

Contains BV for internal structures of the eye

Pigments: melanin and tapetum

Triangular area of yellow-green light reflecting cells

Aids in low light situations-lacking humans/swine/blue eyes

Reflects light back to photoreceptor cells of retina

Just behind iris

Tiny muscles alter lens shape to focus it

Attach to lens via suspensory ligaments

Cells secrete aqueous humor

Muscular diapragm

Constricts or dilates to regulate amount of light into eye

Pigmented

In front of lens/ciliary body

Anterior/Posterior (iris)

Fluid produced by ciliary body

Drains into bloodstream

Blockage of drain->Canal of Schlemm->Excess pressure

Behind lens, gel-like

80% volume of eye

Maintains shape and provides nutrients

Innermost layer, lines interior of eye

Light is focused onto photoreceptor cells by the lens and info is transmitted to the brain via optic nerve

Deepest

Rods: Dim light

Cones: Color, sense either red, green, or blue, numbers and proportions define color vision

Transparent bioconvex disc surrounded by suspensory ligaments and ciliary body

Tissue is crystalline and elastic, shape is altered by contraction of ciliary muscles so lens can focus onto retina

Function of eyes is to conduct rays of light from an object and form an image on the retina

C A P L V R

CORNEA, ANT. CHAMBER, POST. CHAMBER, LENS, VITREOUS CHAMBER, RETINA

Eyelashes growing from Meibomian glands

Often irritate surface of the cornea

Not uncommon in lg/sm animals, need to reapose edges carefully, usually heal well

Eyes are well vascularized, can be stitched even if injury isn't fresh

Rolling inwards of the eyelid

Hair irritates cornea, can result in severe ulceration

Surgical correction often necessary

Cut out crescent shape, snip off

Ethical questions

Neonatal foals->Usually transient

Squamous cell carcinoma most common

Both lg/sm animals, more frequent in unpigmented skin

Prolapsed 3rd eyelid gland

Removal is bad->dry eye

Replacement possible

Inflammation of the conjunctiva

Can be sign of calicivirus, eye problem

Primary or secondary

Ingrowth of vessels as a response to irritation and damage

Blood supply is there to help heal

Normally avascular

Traumatic or infectious

Painful, photophobia, tearing, discharge

Fleuroscein stain highlights it

Never use corticosteroids on ulcerated eye

Small may respond to therapy

Deep may require surgery

Atropine-paralyzes smooth muscle

Lens, opacity of lens

Congenital or acquired

Traumatic

Always treat with agressive antibiotic therapy

Equine recurrent uveitis

"Moon Blindness"

Immune mediated inflammatory condition of anterior portion of eye, control vs. cure

Iris stuck to lens capsule

More common

Entire margin of iris stuck to lens

Blocks normal aqueous drainage

Secondary glaucoma

Utelized for detection of food, predators, social

Sensory receptors on turbinate bones

Jacobson's Organ

Olfactory sensory receptors for pheromones

Chemoreceptors in nasal mucosa

Chemoreceptors

Salt, sour, sweet, bitter

Cats can't taste sweet

Synergy with smell

Used to avoid toxic substances

Funnel-like, collects soundwaves

Cartilage and skin, mobile, communication

Conducts sound from pinna to eardrum

Debris tends to collect in horizontal canal

Ear drum, very thin, taut

Boundary between external and middle ear

Vibrates when soun waves meet surface

Internal side of tympanic membrane

Structures reside in hollow area of temporal bone-tympanic bulla

Other boundary is round oval windows: inner ear

Malleus (Hammer), Incus (Anvil), Stapes (Stirrup)

Transmit vibrations of tmpanic membrane to inner ear via oval window

Bones serve to magnify vibrations

Opens into pharynx, equalizes pressure

Horses have a diverticulum off of tube

Functions to cool blood flowing to brain

Openings into pharynx, carotid arteries nearby

Moist/Warm: prime site for infections

Internal to oval window

Bony labrynth within temperal bone

Membranous labrynth-series of tubular structures within bony labyrnth

Membranes divide spiral labrynth into channels, on either side fluid filled spaces with perilymph, like a parking garage

Runs length of cochlea

Contains endolymph

Waves cause organs of Corti to move

On basilar membrane of cochlear duct

Hair cells which move when fluid moves in wave

Send impulse to afferent nerve endings

Between cochlea and semicircular canals

Endolymph filled

Otoliths (tiny stones) move in fluid, stimulate hairs, generate impulses to vestibular nerve

Info on position of head

3, oriented in 3 planes

Comtain endolymph

Responsible for balence

Waves of endolymph in motion, especially rotation

Endolymph stimulates hair cells with ampulla, triggers to vestibular branch