6. the senses: how companion animals can enjoy their surroundings

eye structure

“monocular vision” definition

• field of view of a singular eye

• blind spot in the rear

“binocular vision” definition

• field of view of both eyes, overlap

• depth perception

cat eyes

• vertical slit pupils

  • gauges distance the best for nocturnal animals

• near sighted

• blurrier vision

  • better at catching movements & shadows

dogs & cats have more _____ which gives them better night vision

1. rods

“tapetum lucidum” definition

• the reflective layer of the eye

• magnifies incoming light

• green/blue glint when light is shining on the eyes

“nictitating membrane” definition

• the third eyelid

• found under the other eyelids on the inside corner closest to the nose

• extends up when needed to protect the eye

the _____ _____ and the _____ _____ _____ _____ _____ _____ _____ are the collective preocular tear film

1. lacrimal glands

2. superficial tear gland of the nictitating membrane

tear film layers

• outer lipid

• middle aqueous layer

• deep layer

“tarsal (meibomian) gland” definition

waxy substance that prevents the lacrimal secretions from flowing out of the face

“meibomian adenoma” definition

a tumor that grows on the eyelid typically caused by an overgrowth of cells in the meibomian gland

“cherry eye” definition

• prolapse of the third eyelid

• gland within the third eyelid pops out

  • gland usually anchored by a fibrous attachment but certain breeds, the attachment is weal

tear drainage system

• 2 lacrimal puncta

• 2 canaliculi

• lacrimal sac

• lacrimal duct: empty tears within nasal

“keratoconjunctivitis sicca (KCS)” definition

• tear deficiency

• persistent inflammation of the conjunctiva & corneal ulceration & scarring

“retina” definition

• houses photoreceptors

  • rods & cones

• area centralis: most sensitive area, tightly packed photoreceptors to make photos sharp

do dogs need prescription glasses/lens/goggles? 

• yes

• contacts can be used as a bandage for dogs with slow-healing ulcers

• goggles can be used to protect the eyes from injuries or the sun

dog cone types

• yellow

• blue

cat cone types

• yellow/green

• blue

ability to distinguish color is _____ pronounced in dogs & cats

1. less

“lenticular (nuclear) sclerosis” definition

• cloudiness of the lens of the eye resulting from aging

• older components of lens are compressed as new components form

• affects lens’ ability to bend & allow light through

• usually does not cause blindness

“cataract” defintion

• cloudiness of lens from a significant change in the structure & integrity of proteins and/or other components making up the lens

• result in opacification of lens preventing light from entering

• various levels of blindness

“strabismus” definition

• abnormal positioning/direction of eye

• one muscle in one side of the eye may be stronger than the other causing eyeball to deviation from normal direction

• cross-eyed: both eyes pointed towards the nose

• divergent strabismus: both eyes deviate away from the nose

“albinism” definition

• more fibers of the optic nerve crosses than normal

• affects depth perception

“creel theory” definition

• lack of melanin pigment

• triggers a switch resulting in the conventional genetic instructions not to be completed

  • abnormal vision system

“feline taurine deficiency” definition

• a lack of the amino acid, taurine, that can not be synthetized in the body

• can cause blindness & heart failure

• caused by disease or diet

outer ear: pinna

• captures sound waves & funnels them through ear canal to eardrum

• mobile in cats

outer ear: ear canal

creates a funnel to carry sound to the eardrum

the middle ear

• eardrum

• hammer

• anvil

• stirrup

• two muscles

  • tenor timpani M & stapedius M

• oval window

• eustachian tube: connects middle ear to back of nose allowing air through

inner ear: cochlea

organ of hearing

inner ear: vestibular system

• organ of balance

• filled with fluid to maintain balance

  • highly developed in cats

deafness

• congenital/hereditary

  • associated with blue eyes & white pigmentation

• acquired

  • toxin, trauma, drugs, etc.

• sensorineural: loss of cochlear nerve cells

• conductive: obstruction of sound reaching cochlea

“vestibular syndrome” definition

• loss of balance, head tilt, rapid eye movement, & motion sickness

  • tilt always towards diseased side

• peripheral: affects inner ear

• central: affects nerves & brain

“righting reflex” definition

• augmented by unusually flexible backbone & absence of collar bone

• allows full upper body rotation so cat can land on it’s feet

cat olifaction

• smell less developed than dogs

• sniffing mechanism: rapid, short inhalations/exhalations

  • sniffing traps air in bony structure to allow molecules to interact with scent receptors

• vomeronasal organ: essential in detection of pheromones

dog olifaction

• acute sense of smell

• can detect odors at extremely low levels

• odor molecules dissolve in moisture on inside of nose

catnip response

• most cats excited by catnip smell but not all

  • reaction is inherited

• not addictive

no saliva, no _____

• taste

  • chemicals from food must dissolve in saliva to be detected by receptors on tastebuds

“filiform papillae” definition

• do not have taste buds

• are instead used for grooming

dog taste

• more taste buds than cats

• 4 classifications: sweet, sour, salty, & bitter

• no affinity for salt

• liking for sweet flavors like fruit

  • “strawberry furanone”

    • organic compound used in flavors derived from strawberries & other fruits

• dislike bitter tastes

dogs & cats have special taste buds for _____ at the _____ of the tongue where it curls

1. water

2. tip

“umami” definition

• the savory based taste

• red meat, eggs, parm cheese, tuna, soy sauce

sense of touch

• skin

• whiskers

• touch receptors

whiskers functions

• help animal sense environment

  • judge size of opening before crawling through

• sense objects without touching them

  • helps cats see at night

• pattern of whiskers unique to every cat

• can help show emotion & interest