Biology Chapter 16 Flashcards: Sense Organs & Functions

Receptor

structure specialized to detect a stimulus

Sense Organs

structure that combines nerve tissue surrounded by other tissues that enhance response to a certain type of stimulus

Transduction

conversion of one form of energy into another

What are the two stages in the sensory process?

Sensation and perception

Sensation

the process of when a sensory receptor detects stimulus

Receptor potential

small local electrical change

Perception

the conscious interpretation of stimuli

Sensory receptors transmit what four kinds of information?

Modality, location, intensity, and duration

Modality

type of stimulus or the perception it produces

What are examples of modality?

vision, hearing, taste

Location

where a stimulus is located (encoded by which nerve fibers are firing)

Receptive field

area within which a sensory neuron detects stimuli

What does the size of the receptive field determine?

Resolution

Resolution

ability to distinguish between two close-together stimuli

Intensity

strength of stimulus

What can a weak stimuli activate?

Most sensitive neurons

What can a strong stimuli activate?

Less sensitive neurons with higher thresholds

Which stimuli has the most fibers respond?

Intense stimuli

What happens to the rate of fibers firing as the stimulus intensity rises?

Fibers fire faster

Duration

how long stimulus lasts

Sensory adaption

if a stimulus is prolonged, firing of the neuron gets slower over time, we become less aware of it

Phasic receptors

rapidly adapt to a constant stimulus and turn off

Examples of phasic receptors?

smell, hair movement, and cutaneous pressure

Tonic receptors

adapt slowly, action potentials continue more steadily while stimulus is present

Examples of Tonic receptors?

Body position, muscle tension, joint motion

General (somatosensory, somesthetic) senses

widely distributed receptors in the skin, muscles, joints, tendons and viscera. Touch, pressure, stretch, heat, cold, pain and unperceived stimuli like blood pressure and composition.

Examples of General senses?

Touch, pressure, stretch, heat, cold, pain, blood pressure, blood composition

Special senses

limited to head, innervated by cranial nerves, and involve complex sense organs

Special sense examples?

vision, hearing, equilibrium, taste, smell

Gustation

sensory perception of molecules dissolved in water

Tastants

Chemicals that stimulate gustatory receptor cells

Taste buds

sensory cells clustered in 4,000

Lingual papillae

visible bumps on the tongue

How many Lingual papillae are there?

4

How many Lingual papillae have taste buds?

3

Filiform papillae

small spikes with no taste buds

What is the function of Filiform papillae?

Sense food texture

Foliate papillae

form parallel ridges along sides of posterior two-thirds of tongue

What is the function of foliate papillae?

have taste buds that mostly degenerate by age 3

Fungiform Papillae

shaped like mushrooms, at tips and sides of tongue

What does each fungiform papillae have?

three taste buds

Vallate papillae

large papillae arranged in a V at rear of tongue

What does the vallate papillae contain?

one-half of all taste buds

Taste Buds

clusters of 50-100 taste cells, supporting cells, and basal cells

Taste Cells

epithelial cells, not neurons

Taste hairs

apical microvilli, act as a receptor surface

Taste pore

opening in taste bud

Basal cells

stem cells that replace taste cells every 7 to 10 days

Supporting cells

resemble taste cells but no synaptic vesicles or sensory role

What are the five primary sensations of taste?

Salty, sweet, umami, sour, bitter

Salty

produced by metal ions (sodium, potassium)

Sweet

associated with carbohydrates and other foods of high caloric value

Umami

meaty or savory taste of amino acids in chicken or beef broth

Sour

acids such as in citrus fruits

Bitter

associated with spoiled foods and alkaloids such as nicotine, caffeine, quinine

What is taste influenced by?

Food texture, aroma, temperature, and appearance

Recent research suggests that there are two more primary tastes which are?

Oleogustus (taste of fats) and water

What is the process of taste for umami, sweet, and bitter?

Second messenger system: sugars, alkaloids, and glutamate activate G protein coupled receptors on taste cell membrane, activate second-messenger systems

What is the process of taste for salty?

Na+ goes straight into the cell, depolarizes it, and then serotonin and ATP are released

What is the process of taste for sour?

H+ enters and lowers pH of the cell causing for potassium to remain in the cell causing it to depolarize

What three cranial nerves carry taste information?

Facial nerve (anterior two-thirds of tongue), Glossopharyngeal nerve (posterior one-third of tongue), and Vagus nerve (palate, pharynx, and epiglottis)

Where do the fibers of the three cranial nerves involved with taste synapse?

Medulla oblongata

Second-order neurons from medulla oblongata relay to where?

Hypothalamus, amygdala, thalamus to primary gustatory cortex, and thalamus to orbitofrontal cortex

Olfaction

sense of smell

Odorants

airborne chemicals

Olfactory mucosa

patch of epithelium in roof of nasal cavity that houses receptor cells

Olfactory cell structure

neck and head are a modified dendrite, and head contains 10-20 immobile cilia

Olfactory hairs

immobile cillia

How many odorant receptors do humans have?

400

Each olfactory cell has receptors for how many kinds of chemical odorants?

one

1st step of Olfactory transduction

odorant binds g protein couple receptor on olfactory, activates cAMP secondary messenger system

2nd step of Olfactory transduction

Opens ion channels for Na and Ca which depolarizes membrane and triggers action potential that travels to the brain

1st step of Olfactory projection to the brain

Olfactory signals are received in olfactory bulbs

2nd step of Olfactory projection to the brain

Signals are relayed caudally in olfactory tracts

3rd step of Olfactory projection to the brain

Primary olfactory cortex in temporal lobe creates conscious perception of odor and relay signals to other brain destinations

4th step of Olfactory projection to the brain

Signals from each temporal lobe are relayed to contralateral temporal lobe, so all processing is mirrored in both cerebral hemispheres

Hearing

Response to vibrating air molecules

Equillibrium

Sense of motion, body orientation, and balance

Sound

any audible vibration of molecules

What causes the eardrum to vibrate?

air molecules hitting it

Pitch

whether a sound is high (treble) or Low (bass), determined by frequency of vibration which is measured in hertz

Loudness

perception of sound energy, intensity, or the amplitude of vibration

What is the typical range of frequency for sound for humans?

20-20,000Hz

Outer (external) ear

Funnel for conducting airborne vibrations to the eardrum

What is the outer cartilaginous part of the ear on the side of the head?

auricle (pinna)

Auditory canal (external acoustic meatus)

Slightly curved passage approximately 3cm long leading through temporal bone to eardrum

Outer end is protected by stiff what?

Guard hairs

Cerumen (earwax)

Ceremonious and sebaceous gland secretions mixed with dead skin cells

Functions of Cerumen?

Traps microbes, waterproofs canal, and keeps eardrum pliable

Middle Ear

Located in tympanic cavity in temporal bone, bounded by eardrum and inner ear

Tympanic membrane

The eardrum, a slightly conical membrane that vibrates in response to sound (highly sensitive to pain)

Tympanic cavity

air-filled, 2 to 3 mm wide space between outer and inner ears

Mastoid cells

air filled spaces in mastoid process of temporal bone

Auditory (eustachian or pharyngotympanic) tube

passageway to nasopharynx, normally flattened and closed but opens when swallowing or yawning

Auditory ossicles

three smallest bones of body, connect tympanic membrane to inner ear

Malleus

has long handle attached to inner surface of tympanic membrane and a head that articulates with incus

Incus

has triangular body that articulates with malleus and long limb articulates with stapes

Stapes

shaped like a stirrup; footplate rests on oval window

Oval window

where inner ear begins

Stapedius muscle attaches to what?

Stapes