Chapter 16: Senses Flashcards
Sensory receptors
detect a stimulus
Stimulus
changes in sensory information
Sensation
a stimulus we are consciously aware of
For a stimulus to be consciously perceived, the sensory input must be sent to what area of the brain?
the cerebral cortex
The 3 criteria used to describe sensory receptors
1- receptor distribution
2- stimulus origin
3- modality of the stimulus
Receptor distribution
the location of the receptors
General sense receptors
located throughout the body in the skin and internal organs; 2 subtypes:
1- somatosensory
2- visceral sensory
Somatosensory sense receptor location
located in skin, muscles, tendons, and joints
Visceral sense receptor location
located in the head region; 5 special senses
The 5 special senses
1- vision/sight
2- hearing/ audition
3- smell/olfaction
4- taste/ gustation
5- balance/ equilibrium and acceleration
Stimulus origin
where the stimulus originates from
Exteroceptors
stimuli originate from the external environment
Interoceptors
stimuli originate from the walls of internal organs
Proprioceptors
stimuli originates from muscles, tendons, and joints, and detects body and limb movement
Modality
the type of stimulus
Chemoreceptors
detect chemical changes such as molecules in the fluid
Thermoreceptors
detect temperature changes
Photoreceptors
detect light changes- color, intensity, and movement of light
Mechanoreceptors
detect touch, pressure, and vibrational changes (most common type)
Baroreceptors
detect stretch changes
Nociceptors
detect pain
Tactile receptors
abundant mechanoreceptors of skin and mucous membranes; endings can be encapsulated and unencapsulated
Unencapsulated tactile receptors
- free nerve endings
- root hair plexus
Encapsulated tactile receptors
- lamellated (Pacinian) corpuscles
- tactile (Meissner) corpuscles
Free nerve endings
- terminal ends of sensory neuron dendrites
- detect pain, temperature, light touch, and pressure
Root hair plexus
- wrap around the hair follicle
- signal initiated by hair movement
Lamellated (Pacinian) corpuscle
- wrapped in neurolemmocytes and concentric layers of connective tissue
- activated by deep pressure and vibration stimuli
Olfacation
detects odors in the air; detected by chemoreceptors
The areas in the brain that receive sensory input from olfactory chemoreceptors
- cerebral cortex
- hypothalamus
- amygdala
Olfactory epithelium
sensory receptor organ
Olfactory receptor cells
primary neurons in sensory pathway for smell
Olfactory bulbs
ends of olfactory tracts located under brain’s frontal lobe
Olfactory tracts
project directly to the primary olfactory cortex, hypothalamus, amygdala, and other regions
CNS areas that deal with olfaction
- cerebral cortex: perceive, identify smell
- hypothalamus: visceral reaction to smell
- amygdala: smell recognition, emotional reaction
Gustation
sense of taste; gustatory cells are chemoreceptors within taste buds
Papillae of the tongue
- filiform papillae
- fungiform papillae
- vallate papillae
- foliate papillae
Filiform papillae
short and spiked; on anterior 2/3 portion of the tongue; help manipulate food and detect texture; do not house taste buds
Fungiform papillae
mushroom-shaped; on the tip and sides of the tongue; each contains a few taste buds
Vallate Papillae
largest, least numerous; arranged in an inverted V on the posterior dorsal tongue; houses most taste buds
Foliate papillae
leaflike ridges; house a few taste buds in early childhood
Lifespan of tastebuds
7-10 days
Composition of a taste bud
- gustatory cells
- supporting cells
- basal cells
The general gustatory pathway to its destination in the brain
1- project first to the medulla
2- secondary neurons projecting to the thalamus
3- tertiary neurons projecting to the primary gustatory cortex in the insula
What are the 5 basic taste sensations?
1- sweet
2- salty
3- sour
4- bitter
5- umami
Sweet
produced by organic compounds (sugars)
Salty
produced by metal ions (Na+.K+)
Sour
associated with acids (vinegar)
Bitter
produced by alkaloids (unsweet chocolate)
Umami
taste related to amino acids producing savory or meaty flavor
The association of smell with taste
ability to taste heavily dependent on the olfactory sense
Photoreceptors
used to detect light, color, and movement
The 2 types of photoreceptors located in the retina
1-rods
2- cones
Rods
most numerous; primarily located in peripheral regions in the neural layer of the retina; especially important in dim light; cannot distinguish color
Cones
less numerous than rods; activated by high-intensity light; provide precise visual sharpness and color recognition; primarily located in fovea centralis of macula lutea; subdivided into 3 types (red, blue, green)
Rhodopsin
opsin in rods
Photopsin
specific opsin associated
Photopigments
are light-absorbing molecules found within membranes of outer segments of rods and cones
2 steps/processes involved in focusing the visual image on the retina
1- refraction
2- accomodation
Refraction
light is bent (refracted) when it passes from one medium to another of different densities (ex. air through the cornea)
Accomodation
allows us to view objects at different distances; involves:
- focal point
- focal distance
Focal point
specific point of intersection on retina
Focal distance
distance between the center of the lens and the focal point
Emmetropia
normal vision
Hyperopia
far-sighted
Myopia
near-sighted
Astigmatism
unequal focusing
Presbyopia
age-related change in vision
Photopigments
light-absorbing molecules
Visual acuity
clearness of vision
What is the normal standard rating for visual acuity?
20/20
The process of accommodation to view distant objects
- ciliary muscles relax, lens flattens
- focal distance increases so the focal point on the retina increases
The process of accommodation to view close objects
- ciliary muscle contracts, and the lens becomes round
- focal distance decreases so the focal point on the retina decreases
Trace the pathway of light from the cornea to photoreceptors to the brain
light rays pass through the cornea -> aqueous humor -> lens -> vitreous humor -> neural tissue of the retina -> photoreceptors
Describe the visual pathway from the photoreceptors to the brain
photopigments in photoreceptors stimulated -> depolarizes bipolar cell -> AP in ganglion cell -> optic nerves -> optic tracts -> superior colliculi and thalamus
Special senses
provided by the inner ear
Hearing
enables us to detect and interpret sound waves
Equilibrium
sensations inform us of the position of the head in space by monitoring:
- gravity
- linear acceleration
- rotation
Spiral organ (Organ of Corti)
sensory structure for hearing
Hair cells
sensory receptors of the inner ear for hearing
Stereocilia
long microvilli covered on the apical surface
Tectorial membrane
gelatinous structure; stereocilia extending into here
Cochlea
snail-shaped, spiral chamber within the bone of the inner ear
Know the path of sound waves from the outside of the ear to stimulate of the CN VIII
Frequency
the pitch of the sound; measured in hertz (Hz)
Intensity
the loudness of the sound; measured in decibels (dB)
Sound
the perception of pressure waves established from vibrating objects
What is the function of auditory ossicles?
amplify sound waves captured by the external ear through vibrations
3 auditory ossicles
1- malleus
2- incus
3- stapes
Describe the auditory pathway from stimulation of CN VIII to the brain
1- nerve signals for hearing propagated along CN VIII to the brain
2- go to the inferior colliculus for reflex response to noise
3- then travels to the thalamus, which directs signals to the primary auditory cortex in the temporal lobe
Utricle
saclike, membranous structure within the cochlea
Saccule
saclike, membranous structure within the cochlea
Semicircular canals
semicircular ducts connected to the utricle that contian a membranous labyrinth
Linear acceleration
tilting your head
Angular acceleration
the rotational movements of the head
Linear acceleration is detected by
the utricle and the saccule
Macula
contains the receptor cells
Kinocilium
one long cilium
Otolithic membrane
helps increase the weight of the otolithic membrane covering hair cells
Ampulla
expanded region within each semicircular duct/canal
Crista ampullaris
an elevated region on the ampulla
Cupula
extends across semicircular duct to the roof over ampulla
Explain how the semicircular ducts function to detect rotational movement of the head
- with head rotations
- pushes against cupula, causing bending of the stereocilia
- results in altered neurotransmitter release from hair cells
- stimulation of sensory neurons
Summarize the nerve pathways involved in equilibrium
