Sense Organs Flashcards
Sensory organs are extensions of the ____ that allow for monitoring of the ___
CNS
Internal and external Body
What is adaptation
When a repeated signal over time begins to give a decreasing signal to the CNS to the point there is not signal at all
What does adaptation prevent
Overloading the senses with unnecessary information
What are the four general stimuli that sensory receptors are sensitive to
Mechanical ( touch hearing balance)
Thermal
Electromagnetic (vision)
Chemical (smell, taste)
What are the 10 main senses divided into?
General senses
Special senses
What is geomagnetism
A special sense in some animals (birds and fish) that help navigate during migration
What are the 5 general senses
Visceral sensations Touch Temperature Pain Proprioception
General senses are distributed _____ and transmit info to the CNS through the ___ and the ___
Throughout the body
Through the PNS and ANS
What are visceral sensations of the body
Interior body sensations, vague and poorly organized. Include sensations for hunger, thirst, full organs and sexual drive
How are hollow organs stimulated with visceral sensations
Stimulated by stretch (filling/distension) which results in the perception of PAIN
What is the exception to visceral sensations of pain to a hollow organ filling
The bladder -the sensation of fullness is felt, not pain like the GIT
True or false
Many internal structures can be handled cut or crushed without perception of pain
TRUE
True or false
The peritoneum and pleura hace loads of sensory receptors so any inflammation ot roughening due to infection is extremely painful
TRUE
Touch (AKA the tactile sense) is
The sensation of something being in contact with the body
Can touch perception adapt to continuous touch or pressure
Yes, you are often unaware unless the stimulus changes or is increased
What are superficial temperature receptors
Receptors for temperature located in the skin
When extreme temperatures are detected by superficial receptors what happens
Impusles to the CNS increase
Superficial receptors cause a ____ change in ___ to correct changes in temperature
Conscious changes in behaviour
If temperature is normal, what happens to the impulses
Impulse frequency is low and steady resulting in no consious awareness
What are central receptors for temperature
Monitors the core body temperature via the blood
What is the thermostat center of the brain
The hypothalamus
What are two ways core body temperature is increased
Fever (pyrogenic hyperthermia)
Non pyrogenic hyperthermia
What happens with a fever
Causes body to generate and convserve heat (shivering, vasoconstriction pilonerection)
What is pyrogenic hyperthermia
A increase in core body temperature due to pathogens/infections/toxins that imfluence the hypothalamus
What is non pyrogenic hyperthermia
Imcrease of temperature resulting from exertion or the environment (animals temp to cool down) and the hypothalamus shuts down
The CNS corrects fluctuations in temperature through changes in
Blood flow, sweating, piloerection, shivering, hormones, behaviours
What is heatstroke
Shock due to severe hyperthermia caused by a hot external environment or exertion
Shock is due to fluid loss, vasodilation and heat change to organs (low tissue perfusion, low blood volume and pressure)
What can high temperatures cause
Impair brain fucntion Damage organs Weakness Convulsions Unconsciousness
What is the max survivable temperature above normal
About 5 degrees
What is hypothermia
A decrease in temp (from anesthesia or environment) that causes a decrease in HR, RR, weakness, confusuon, comas and death
What is nociception and what are nociceptors
Nociception is the process of feelings pain
Nociceptors are pain receptors
Where is the only place nociceptors are NOT found
The brain
What are headaches
Caused by swelling of the sureounding tissue (meninges) or spasms in the msicles in the face, scalp and neck
True or false
Nociceptors have adaptation
FALSE
they cannot be turned off and perception of pain cannot be dulled
What are the 4 steps of pain perception
Transduction
Transmission
Modulation
Perception
What is transduction
Conversion of stimuli into a nerve impulse
What is transmission
Moves signal up the acon of the sensory nerve fiber
What is modulation
Information is integrated at the levelnof the spinal cord and sent to the brain
What is perception
Pain is processed by the brain
What step of pain perception is influenced by drugs (opioids)
Modulation
Pain can be classified as superficial, deep or visceral. What is different about visceral pain perception
Visceral pain is often referred pain. Which is when it is interpreted as originating from somewhere elsenin the body
Give an example of reffeded visceral pain
Heart pain isnoften felt as pain down rhe left arm
Why does reffered pain happen
Because the neuron in pain center can reciece inputs from nerves from different parts of the body so it confuses the location from where pain is coming from
What is acute pain
Sharp and intense
What is chronic pain
Dull and aching
Why do animals not seem to ever be in pain
A survival instinct to not look week to predators
True or false
Sensation for pain is often greater is the pain is anticipated
True
Which animals are more likely to endure pain
Stressed or relaxed animals
Relaxed animals
True or false
Pain receptors may continue signalling when a pain source has been removed
TRUE
What are the signs of pain
Loss of normal behaviour
Expression of abnormal behaviours
Reaction to touch
Physiologic parameters
What is general anesthesia
Compelte loss of sensory perception with loss of consciousness
What is local anesthesia
Loss of sensation from a specific area with no loss of consciousness
What is analgesia
Perception if pain is decreased but kor absent (by use of NSAIDS)
Pain killers
What is hyperesthesia
Increased responsiveness to a stimulus including pain
What is proprioception AKA body sense
The sense of telative body positions and movement without having to look
Whwre are sensory receptors for proprioception located
Stretch receptors in Skeletal muscles, tendons, ligamnets and joints
What creates the overall sense of positioning by integrating the information
The cerebellum coordinates movements
What is ataxia
Loss of perception during walking
Druken gair
What are the special senses
Smell Taste Hearing Sight Equilibrium
What is taste (gustatory sense)
A chemical sense detected by the tongue, mouth and pharynx
What are the chemical receptors in the tongue
Taste buds located on the tongue in elevated papillae
papillae have have tiny openings called taste pores whoch allow for what
Dissolved substances to stimulate the sensory cells that send an impulse to the brain
Heat receptors in the tongue tonorevent eating food is too hot. What does hor sauce stimulate
Spicy food stimulate heat receptors which is why spice is percieved as pain
Taste is important for
Selecting food containing things the animals need
Taste is strongly linked to
Smell
What is the role of saliva in taste
Dissolves the chemical molecules in the food to be detected by the taste buds
What is smell (olfactory sense)
A chemical sense carried by the olfactory nevere (CN 1)
Extremely important for communication between animals
Olfactory sense is rganized in 2 patches if olfactory cells and supporting epithelium covered in mucus. How do they sense smell
Odor molecules dissolve in mucus and the sensory receptors create signals and are sent to the brain
Why is sniffing important for smell
Sensory areas are above the usual path of inhaled air, so additional force of sniffing improves sense of smell
Each olfactory cell is a neuron specialized to detect a specific chemical. Why is this?
Helps differentiate smells
Can sensory receptors for smell adapt to stimuli?
Yes!
True or false
it doesnt take many molecules of an order to stimulate the receptors
True
What is the second area of smell
The vomeronasal organ
What is the vomeronasal organ important for
A diverticulum of the nasal cavity into the hard palate that are sensitive ti pheromones
What is hearing (auditory sense)
Converts air molecule vibrations into nerve impusles and interpreted by the brain as sound
What is equilibrium (balance)
A mechanical sense perceived in the ear
What structures does the outer/external ear contain
Pinna
External auditory canal
Tympanic membrane (eardrum)
What is the pinna
The fleshybexternal part of the ear, acts as a funnel to collect sound
What are aural hematomas
Blood filled subcutaneous swelling in the pinna normally from trauma causing a rupture of a vessel
What is the external auditory canal
Soft membrane lined L shaped passageway from the pinna to the eardrum
Transmits found to the tympanic membrane
Can the external auditory canal be filled in hair
Yes
What type of gland does the external auditory canal have
Ceruminous glands: produce wax to protect from infection
The external auditory canal is prone to otitis externa. What is this?
Inflammation if the external ear canal caused by water (called swimmer’s ear) which causes a build uo of bacteria
What is the tympanic membrane (ear drum)
A semitransparent membrane that is tightly stretched across the opening between the external auditory canal and the middle ear
Vibrates at the same frequency as sound waves strike it
What is the middle ear
A hollowed iut area of the temporal bone lines by a soft tissue membrane connected to the pharynx by the eustachianntube and contains the ossicles
What separates the middle ear from the inner ear
The oval and round windows
What is horner’s syndrome
Because if the sympathetic fibers in the middle ear, horner’s syndrom is caused by a disruption of the nerve pathway
What are the signs of horner’s syndrome
Drooping eye lid (ptosis) third eyelid prolapse, retracted globe, constricted pupil (meiosis) and sweating in horses
What are the three ossivles in the middle ear
The malleus (hammer)
Incus (anvil)
Stapes (stirrup)
What do the ossicles do
A system of levers that transmit and amplify aound vibrations of the tympanic membrane to the cochlea
What is the malleus connected to
Attached to the tympanic membrane
What is the incus connected to
Form the synovial joint to link the 2 other ossicles
What is the stapes connected to
Attached ti the membrane of the oval window of the cochlea
What are the two small muscles in the middle ear important for
Dampens loud noises
One attaches to the stapes and the other to the malleus
When they contract they reduce vibrations and protect the inner ear from loud noises
What is the eustachian tube
Functions to equalize pressure on both sides of thebtympanic membrane and protect it from rupturing
Creates “popping” to equalize in changes of pressure/altitude
What is the guttural pouch
A latge air filled diverticulum in the eustachian tube of horses
Contains a beanch of the carotid artery
This is the coolong device for blood flowing to the brain (activated by exercise)
What cranial nerves pass along the wall of the guttural pouch
CN VII, IX and XII
What is the inner ear
Site where hearing and balance in sensed
What parts are included in the inner ear
Cochlea
Vestibule
Semicircular canals
What is the hearing portion of the ear
The cochlea
The cochlea is the ____ and the spiral tibe inside of it is the _____
Bone cavity
Cochlear duct
There is a ___ channel that isnon either sodenof the cochlear duct
Fluid channel
The two arms of the cochlear duct form a ___ at the apex of the cochlea
U shaped tube
The u shaped tube/cochlear duct has two openings
The oval window and the round window
The oval window attaches to the
Stapes
The round window
Lets out sound from the cochlea
The cochlear duct houses the
Organ of corti
The organ of corti has cilia on the apical surface and nerve endings at the base of the hairs, the hairs are covered in the
Tectorial membrane
Movement of the hairs of the organ of cortis depend on ___ and ___ to kove th tectorial membrane
Sound waves Fluid movement
Sound perception:
Sound waves cause typanis mambrane and ossicles to
Vibrate
Sound perception:
As the stapes vibrates it pushes and pulls on the
Oval window of the cochlea
Sound perception:
Vibrations of the oval window are transferred to
The organ of corti which vibrates hairs
Sound perception:
The bending of hairs in the organ of corti generates
Nerve impulses that travel to the brain via the vestibulocochlear nerve (CN VIII) to be interpreted as sound
Different frequencies are felt at different parts of the organ of corti, this allows for
Differentiation of sounds (partly due to the length of hairs)
What helps the ears to localize sound better
A slight asymmetry in the ears
Where is equilibrium sensed
The semicircular canals
What is equilibrium
The ability to mainatin balance by tracking the position and movement so of the head
Receptors for equilibrium are in portions of the inner ear;
The vestibule and the semicircular canals
Sensory input for equilibrium are also from
Proprioceptors and vision
What is the equilibrium triad
The vestibule, vision and proprioceptive receptors
What causes motion sickness
Conflicting signals from vision and vestibular systems
What does the vestibule sense
Static equilibrium or linear motion
The vestibule is made of 2 saclike spaces, contain a patch of sensitive epithelium which has
Sensitive hairs and supporting cells covered in a gelatinous fluid that contains otoliths
What are otoliths
Tiny crystals made of calcium bicarbonate
What does tilting the head cause to the otoliths
Shifts the otoliths due to graviuty and bends the hairs, which generates the nerve impulses sent to the brain
What is a sign often seen with vestibular disease
Circling and loss of balance
What do the semicircular canals sensen
Dynamic equilibrium or rotary motion
The 3 semicircular canals are arranged at
Right angles to eachother
The 3 canals sense movement based on their 3 planes of orientation
Horizontal
Frontal
Sagittal
The semicircular canals are similar to the vestibule but have no
Otoliths
The hairs of the semicircular canals stick up into a
Gelatinous fluid which is a free floating structure in the canals that move with the fluid
As the head rotates the fluid lags due to
Inertia
Movement of the geleatinous fluid in the semicircular canals causes the
Hair to bend and generates nerve impulses
What is normal nystagmus
Jerky movement of the eyes that occurs when the head is rotated side to side
Eyes try and remain on a stationary object duriing movement, but jumps to the next stationary object when it changes vision fields
What is abnormal nystagmus
Jerky eye movements when there is no head movement
Has a fast and slow phase usually in a horizontal plane
What is abnormal nystagmus a sign of
General anesthesia
Vestibular disease
What is pendular nystagmus
A lifelong condition of minor significance (often in cows and cats)
Has no obvious fast or slow phase
Who is prone to nystagmus and strabismus
Siamese cats
They do not have stereoscopic vision so this does not bother them
What is strabismus
When the eye do not line up with one another
What two terms are used when referring to the eye
Ocular
Ophthalmic
What is the outer fibrous layer of the eye composed of
Cornea
Sclera
Limbus
What is the cornea
Transparent anterior part of the eye that lets light into the eye
Has no blood vessels but has lots of nerves (very painful when damaged)
Why might the transparent cornea become opaque
When it dried out or becomes edematous (swollen with water)
What is the sclera
The white of the eye, tough layer that gives shape and protects the inner structures
What is the limbus
The junction between the sclera and the cornea
Can be used for landmarking
What is the middle vascular layer of the eye composed of
choroid
Iris
Ciliary body
What is the choroid
At the back of the eye between the sclera and retina
Mainly contains dark melanin and blood vessels
What is the tapetum
The reflective layer on the choroid responsible for night vision because it causes light to bounce back through photoreceptors a second time to be processed again
Not found in pig or humans
What is the iris
The colored portion of the eye that controls the amount of light entering the eye
What is the pupil
The central opening/hole of the iris where light enters
The two layers of muscles of the iris
One like the spokes of a wheel to open the eye
Other is arranged circularly to contract the eye
Where does the iris get its nerve supply
The autonomic NS
Sympathetic: dilates the eye
Parasympathetic: constricts the eye
What is the ciliary body
Holds and helps focus the lens (focused by contraction and relaxation of the ciliary muscles)
How does the ciliary body connect to the lens
By the suspensory ligaments that attatch to the lens
What does the ciliary body produce
Aqueous humor
What is the inner nervous layer of the eye composed of
The retina
What is the retina
Functions to collect light/image
Contains the rods and cones which are sensory receptors for light
Nerves and vessels of the retina converge at the optic disc
The surface of the retina is sometimes called the fundus
Where does the retina originate
The optic nerve (where the nerve fibers enter and exit the eye to the optic nerve
What are the two compartments of the eye
Aqueous compartment
Vitreous compartment
What is the aqueous compartment and what is it divided into
Between the cornea and the lens, divided into the anterior and posterior chamber
Anterior: in front of the iris
Posterior: between the iris and the lens
The aqueous compartment is constantly filled with aqueous humor, this is primarily responsible for
Maintaining the internal pressure of the eye
Where does the aqueous humor drain into and why
Through the canals of Schlemm to be recylcled by the body (at the anterior chamber where the cornea meets the iris)
If drainage of the aqueous humor does not occur fast enough or if there is excess production what can happen
It can lead to glaucoma
Increased intraocular pressure due to accumulation of fluid and damages the optic nerve
Can be genetic or caused by inflammation of the canal of schlemm
What is enucleation
Eyeball removal (may be needed for glaucoma)
What is the vitreous compartment of the eye
Located between the lens and retina
Filled with a jelly like fluid called the vitreous humor
Maintains the shape of the eye and hold the retina in place
What is the lens
Soft transparent elastic biconvex structure made of tiny protein fibers that lacks blood vessles and nerves
How does the lens affect the light entering the eye
The ciliary body contracts and pulls the lens flatter or maskes it rounder in order to focus light
If the lens is rounded it is for
Up close vision
What is eyestrain
Exhaustion of the ciliary body muscle when focusing on close up onjects for too long
Most fish can change the shape of their lens so they
Adjust the length of their eye
The lens can become ___ with age
Opaque
Old fibers harden and lose transparency, gives a bluish hue to the lens
When the lens becomes opaque, what is this called
Lenticular sclerosis or nuclear sclerosis
What is the difference between lenticular and nuclear sclerosis
Lenticular: the whole lens
Nuclear: center of the lens
Sclerosis: thickening
Lenticular and nuclear sclerosis may progress into
Cataracts
What is cataracts
White opacity of the lens
May cause blindness
Common in old dogs
Can develop in younger animals due to heredity or diseases (infection, trauma, diabetes mellitus, radiation/UV)
How do you treat cataracts
Surgical lens removal
If the whole eye is cloudy (can’t see the iris) the ___ is damaged
Cornea
If the eye is cloudy but you CAN see the ris the ___ is damaged
Lens
If you can’t see into the eye then the animal
Can’t see out of it
What is the optic disc
The point at which the nerve leaves the eye to transmit visual info to the brain
Why is the optic disc the blind spot in vision
Bevause it has no photoreceptors so any light hitting it does not contribute to the image
True or false
The brain can fill in the gap in detail of the blind spot
True
What are the two types of photoreceptors
Rods and cones
What are rods good for
Function well in dim light but do NOT detect color and have poor sensitivity to detail (predominant in animals)
What do cones detect
Function well in bright light, detect color and great sensitivity to detail
C=color=cones
True or false
Animals are color blind
FALSE
Animals aren’t often color blind but they see the world in washed out colors
Animals have a low number of cones
Primates have an area on the center of the retina called the macula, what is this
Has a high concentration of cones, give excellent clarity and precise vision
Why are animals good at detecting motion
Because they have a higher number of rods (motion stimulates rods more than a static image)
What do rods require to function
A protein called rhodopsin
What does rhodopsin synthesis require
Vitamin A
Vit A deficiency can lead to
Night blindness and eventaully total blindness
What is refraction
The bending of light rays as they pass from one medium to another at an oblique angle
Explain the pathway of light
Air Cornea Aqueous humor Lens Vitreous humor Retina
What structure has the most significant contribution to refraction
The cornea
What is the only controllable structure in the eye for refraction
The lens
True or flase
The image in the eye is initially formed upside down
TRUE
What is refractive eye surgery
Cuts the cornea to alter its shape and correct changes in vision
Nerves from the optic nerve merage at the ___ and some nerves cross over to the other side of the ___
Merge at the optic chiasm and cross over to the other side of the brain
When nerves crooss over to the other side of the brain, it allows info from slightly different views to converge on the same part of the brain, this allows for
Stereoscopic vision and depth perception
You need ___ vision to see 3D objects
Binocular vision
Predators have better binocular vision but in a ___ range
Narrow range
Prey animals have narrow ranges of binocular vision but have a wide range of ___ vision
Monocular vision
What is responsible for conscious perception of images
The cerebrum
What is the conjunctiva of the eye
Special mucous membranes lining the eyeball and eyelid, covers the visual pary of the sclera and cornea and the inner surface of the eyelid
What is the palpebral conjunctiva
Lines the inner surface of the eyelid
What is the bulbar conjunctiva
Reflection of the conjunctiva into the eyeball
What do different colors of the conjunctiva indicate
Paleness: anemia
Yellow: jaundice
Dark purple: cyanosis
Inflammation of the conjunctiva is called
Conjunctivitis
Result of bacteria/viruses/irritants
Responds quickly to treatment
The lateral and medial junctions of the eyelids are all the later and medial
Canthus
What are the meibomian glands
Glands that line the margins of the eyelid
Secrete a waxy substance that conatin tears in the eye
Meibomian glands can be come plugged/enlarged/ cancerous, how can you treat a plugged meibomian gland
Hot compresses or pulling out the associated eyelash
What is the nictitating membrane
The third eyelid -fold of conjunctiva reinforced by a T shaped cartilage at the medial canthus of the eye
Has lymphatic tissue
Also has an accessory lacrimal gland
What is cherry eye
A protrusion of the third eyelid when the lacrimal gland is not properly attached and prolapses and becomes inflammed
Treatment is to remove the third eyelid and/or duct and treat inflammation
Retraction of the eyeball or external pressure causes the third eyelid to
Passively close across the cornea
What is the lacrimal gland
Pink glands located on the dorsolateral aspect of the eyeball that releases tears onto the surface of the eye
Tears are made of 3 sources/layers
From the conjunctiva (has antibacterial substances)
From the lacrimal glands: moisturizes the cornea (bulk of watery fluid)
From the tarsal gland: wazy substance that minimizes evaporation and spillage of tears (meibomian glands)
What is the lacrimal duct
An opening which drains excess tears on the upper and lower eyelids nears the medial canthus
Describe the pathway tears are drained
Lacrimal canaliculi
Lacrimal sac
Nasolacrimal duct
Nasal cavity
Many dogs have poorly formed or imperforate ducts causing characteristic
Tear staining below the eye
How many muscles attach to the eye
6 muscles
4 straight
2 oblique
What is the retractor bulbi muscle in the eye
Pulls the eye deeper into the socket and protrudes the third eyelid
What is entropian abnormality
An inversion of the lid margins into the eye
Eyelashes irritates the corneal and conjunctival surfaces and causes chronic abrasion of the cornea and results in a cloudy cornea
What is an ectropion abnormality
An eversion of the lid margins causing chronic conjunctival exposure, excessive discharge, abrasion of the cornea, droppy eyes and imflammation because of the debris getting stuck in the eye
Common in droppy eyed dogs (basset hounds)
What is cherry eye
A genestic weakness in attachment of the gland to the third eyelid
Inflammation or prolapse of the gland and third eyelid
Common in young dogs and droopy eyed dogs
What happens with an obstruction of the nasolacrimal duct
Causes tears to run down the face instead of inot the nasal canal (discoloration)
Caused by genetic malformation, inflammation, foreign bodies or infection
What happens with prolapse of the eye (proptosis or exophthalmos)
Acute prolapse of the eye as a result of trauma
Most common in dogs and cats
Prognosis for retention of vision is poor
Prognosis for retention of globe is good
What is ocular squamous cell carcinoma (cancer eye)
Most common in white faced outdoor aniamls (exposed to sun more)
Has hereditary bases
Usually occurs in solder animals
Tumor may originate from eyelids, conjunctiva or third eyelid
The cancerous or precancerous leions can be present in both eyes and can be removed in early stages
What are corneal ulcers
Often because of trauma or infection (leads to progression)
Diagnosed with fluorescein stain
Shallow corneal ulcers heal ___ by epithelialization
Rapidly
Deep corneal ulcers need vessles to grow in from the ___ in order to heal because they have no blood vessels in the cornea
Limbus
What is keratitis
Inflammation of the cornea with resulting edema, vascularization, scarring and pigmentation
If you can’t see the iris, it may include a corneal ulcer
Keratitis is seen in all species because of
Mechanical damage
Keratoconjunctivitis sicca
Ectropion
Infections
What is conjunctivitis
Inflammation and/or infection of the conjunctiva
Associated with physical irritation to dust or infection
Results in excessive tear production and third eyelid swelling
What is keratoconjunctivitis sicca (dry eye)
Due to tear deficiency
Usually results in conjunctivitis, corneal ulceration or corneal scarring
Results in inflammation due to drying (sicca)
What is nuclear sclerosis
Blusih transparent haze that develops in the lens of the eye in older animals
Animals can still see
What is glaucoma
Increase in intraocular pressure that dmages the retina and optic nerve leading to blindness
Very painful (only presenting concern)
What is cataracts
Opacity fo the lens
Immature: not the whole lens
Mature: entire lens
Common in older aniamls or with diabetes mellitus
Can be secondary to inflammation of the uvea
Juvenile cataracts are more often inherited especially in horses and in dogs (spaniels and siberian huskies)
What is progressive retinal atrophy
Night blindness leading to total blindness
An inherited disease complex seen in irish setters and collies as young as 4-6 months and in mini poodles as old as 5 years
What is otitis externa
Inflammation of the pinna and external auditory canal
May be caused by trauma, excess wax, moisture or hair or ear mites
Most common in floppy ear dogs
Signs: painful itchy smelly ears (from yeast)
What is otitis media or interna
Usually progressing from otitis externa from an infection tracking in the eustachian tube from the nasopharynx
More difficult to treat than otitis externa
Signs: head shaking, head tilt, circling and loss of balance with otitis interna
May lead to meningitis and death (close to the brain)
What is deafness
Can be aquired or congenital (syndrome in cats causing white fur, blue eyes and deafness -autosomal genes is dominant with partial expression for deafness)
