How is sensation stimuli detected?

1. General
2. Special

What do General receptors detect?

(6)

• temperature
• pain
• touch
• stretch
• pressure
• proceiption

What do special senses detect?

(5)

• Gustation
• Olfaction
• vision
• equilibrium
• Audition

Charateristics of receptors

• Smaller receptive field offers greater specificity of location 
• Smaller receptors on hand - larger on back
• May act continuously (tonic) - pain
• May merely detect changes - sitting on something - after a while you don't feel it

Tonic Receptors

With continued exposure sensitivity to the stimulus remains constant

ex - hold head up - balance receptors in ear

Detection of a new or changed stimulus produces a response. 

With continued exposure sensitivity to the stimulus dimishes - called adaption

ex - foot in shoe - tactile receptors on skin

Peripheral Sensory Receptors are:

They are classified according to:

Structures that pick up sensory stimuli which initiate signals in sensory axons.

Stimulus origin - outside or inside the body

Receptor Distribution - where is the receptor

Modality of stimulus - what is being detected

1. Externoreptors - Detect stimuli from external environment
2. Interoceptors - Detect stimuli from internal organs (vicera) - also stretch, pressure, chemical changes and temperature in vicera
3. Proprioceptors - posture and where you are in space, awareness of the position and state of contractons of muscles

Two types of receptor classificaton by distribution are:

1. Somatic sensory receptors - housed w/i the body wall - skin - chemicals temperature, pain touch and proprioception
2. Viceral sensory receptors - Housed in walls of vicera - respond to chemicals, temperature and pressure

Types of receptor classificaton by Modality of stimulus are:

(6)

1. Chemoreceptors - molecules - taste, smell
2. Thermorecptors - skin/tongue - temperature
3. Photoreceptor - cones and rods - Light
4. Mechanoreceptors - pressure, stretch, tension, touch, vibration - tactile receptors
5. Baroreceptors - pressure changes w/i body structures
6. Nociceptors - pain

What are Tactile Receptors?

What are the two types?

What is the difference?

1. Mechanorreceptors in the dermis & hypodermis
2. Most numerous type of receptors

Unencapsulated - no connective tissue wraping

Capsulated - covered by connective tissue or glial cells

1. Receptors are confined to head region
2. Receptor cells housed in complex sensory organs or distinctive epithlial structures
3. Sensory information travels via Craniel Nerves

What type of receptors are taste buds? 

Where are they located? 

What are the 4 types?

Chemorecptors - must have saliva to taste

On tongue, posterior palate, cheeks, posterior pharynx, epiglottis

Vallate

Filiform

Fungiform

Foliate

What is a general name for taste buds?

What are they made of?

Papillae

Epithelial and connective tissue elevations

Which type of Papillea are

• short and spiked
• are on the anterior 2/3 of the tongue
• do not have taste buds?

These papillae

•  are the least numerous
• largest
• arranged in an inverted V on the posterior dorsal surface of the tongue
• surrounded by a deep narrow depression
• Most of our taste buds housed in these

Which type of Papilae are

• block like projections
• located primarily on the tip and sides of the tongue
• contain only a few taste buds?

Which type of Papillae

• are not well developed
• ridges on postierior lateral side
• taste buds only in infancy and childhood and die as you grow up

How often do taste buds replace?

What happens when you turn 50?

Book - 7-10 days

Lecture - 3-4 day

At age 50 you start to loose more taste buds than you replace - why old people may not have an appitite.

What are the 3 types of cells in Taste buds?

What type of epithelial cells?

1. Supporting cells - insulate gustatory cells from each other and surrounding epithelium
2. Gustatory cells - chemoreceptor cells
3. Basal cells- immature, replace other two cell types.

1. Salty - Na+
2. Sweet - Glucose
3. Bitter- H+ (hydrogen ions) acid
4. Unami - amino Acid - Glutamate (chix soup)

1. Facial Nerve (VII) innervates anterior 2/3 of tongue
2. Glossopharyngeal (IX) posterior 1/3 of tongue

Where are the olfactory bulbs located?

How many odors can the olfactory system recognize?

Nerves run through the Cribform plate

50-80 different primary oders as well as many thousands of other chemical stimuli

What are the three types of cells in olfaction?

What do they rest on?

1. Olfactory neurons - receptor cells -chemorecptors- when you smell the actual molecule of the substance is on the receptor.
2. Supoporting cells - surround the olfactory neurons
3. Basal cells - stem cells for renewal of others

Mucosa of the Nasal Cavity

What do the photoreceptors in the eyes detect?

What are the accessory structures of the eye?

What is their purpose?

Light, color and movement

1. Conjuctivea -superficial covering over anterior exposed surface
2. eyebrows, eyelashes, eyelids - foreign objects out
3. Lacrimal glads - moist and clean

Protect the eye

1. Fibrous
2. Vascular
3. Neural

Fibrous Tunic

1. Sclera
2. Cornea

1. Iris
2. Ciliary Body
3. Chorod

Neurons need constant O2 - why this part of the eye is so vascular

Where are the Photoreceptors of the eye located?

What are the two types?

What do they do?

Neural Layer of the retina

Rods - function in dim light

          Don't provide sharp vision or color vision

Cones - Operate best in bright light

            Provide high acuity color vision

1. Macula lutea containes mostly cones
2. Fovea centralis - found in Macula Lutea contains only cones - maximal visual acuity
3. Optic disc - axons and ganglion cells converge to exit the eye - Blind spot

What extension of the fetal brain does the retina develope from?

What week does it start? - Finish?

Diencephalon

Starts early week 4

Finishes week 20

What is the name for the condition when the image focuses behind the retina?

(far sightedness)

What kind of lens can correct this?

Hyperopia

Convex Lens

What is the name for the condition in which the image focuses in front of the retina?

(nearsightedness)

What type of lens corrects this?

Myopia

Concave Lens

1. Outer Ear
2. Middle Ear
3. Inner Ear

1. Auricle
2. External auditory canal
3. Typanic Membrane
4. Produces Cerumen

Earwax is made of

Cerumen and dead skin cells

• Air filled typanic cavity
• A boney wall separates middle ear from inner ear
• houses the oval and round windows

1. Incus
2. Malleus
3. Stapes

1. Vestibule
2. Semicircular Canals
3. Cochlea

1. Bony Labyrinth - spaces or cavities w/i the petrous portion of the temporal bone

1. Membranous Labyrinth - fluid-filled tubes and spaces w/i the bony labyrinth

Where are the uticle, and saccule housed?

What do they do?

The membranous Labyrinth structure w/i the bony structure of the Vestibule.

Detect acceleration and deceleraton and gravity

Where are the semicircular ducts?

What do they dectect?

they are the membranous structure w/i the semicircular canals

They detect rotational movements - where you are in space - cerebellum

What structures make up the Cochlea?

What do they detect?

Cochlear Duct

Audition

Where does hearing happen?

Where are the receptors for hearing located w/i this structure?

Whate is another name for them?

• Cochlea - two parts spiraling chamber and cochlear duct

Receptors for hearing located in cochlear duct, specifically in the spiral organ of corti

• Contains the Inner and Outer hair cells  - the receptor for hearing , also called sterocillia
•  Tectorial Membrane   

1. Soundwaves - ex. au. canal- vibrate typanic membrane
2. vibration moves auditory ossicles - sound waves are amplified, stapes moves w/i the oval window - pressure waves generated
3. Vestibular membrance vibrates - pressure wave in endolymp of sdcalea media - displace a specific region of basilar membrane- hair cells are distorted-stimulates cochlear nerve
4. remaining pressure wave vibrations transfered to the scala tympani and exit via the round window