Ch. 2 Senses & Perception

These flashcards cover key concepts from the chapter on Senses & Perception, including mechanisms and anatomy of vision, hearing, taste, smell, touch, pain, and related disorders and treatments.

What is transduction in sensory systems?

The process of converting external stimuli (e.g., light waves, sound waves, molecules) into electrical signals the brain can interpret.

Which sense engages about 30% of the human cerebral cortex?

Vision.

Through which eye structure does light first pass to enter the eye?

The cornea.

What regulates the amount of light entering the eye by changing pupil size?

The iris.

On what retinal structure is a two-dimensional, reversed image of the visual field mapped?

The retina.

Name the three major retinal neuron types.

Photoreceptors, interneurons, and ganglion cells.

Which retinal cells perform the initial phototransduction?

Photoreceptors (rods and cones).

Which photoreceptor type is most sensitive in dim light?

Rods.

Which photoreceptors provide color vision and fine detail?

Cones.

How many types of cones are in the human eye, and to which colors are they most sensitive?

Three types—red, green, and blue.

What is the fovea?

A small pit in the center of the retina densely packed with cones (red and green) for highest visual acuity.

What eye region surrounding the fovea is crucial for reading and driving?

The macula.

What condition results from photoreceptor death in the macula and is a leading cause of blindness over age 55?

Macular degeneration.

Define a ganglion cell’s receptive field.

The portion of visual space whose stimulation affects that single ganglion cell’s activity.

What visual function is enhanced by center-surround receptive fields of ganglion cells?

Contrast detection.

Why does each eye have a blind spot?

The exit point of the optic nerve contains no photoreceptors.

Where do optic nerve fibers from both eyes cross?

The optic chiasm.

Which thalamic nucleus relays visual information to cortex?

The lateral geniculate nucleus (LGN).

Where is the primary visual cortex located?

In the occipital lobe at the back of the brain.

Cells in higher layers of visual cortex respond best to what kinds of stimuli?

Edges, bars, or motion with particular orientations and directions.

What two major cortical processing streams handle visual information?

The dorsal ("Where") stream and the ventral ("What") stream.

Which stream traditionally integrates object identity, color, and memory?

The ventral ("What") stream.

Which stream traditionally guides spatial relationships and actions without conscious thought?

The dorsal ("Where") stream.

What is binocular vision?

Depth perception achieved by overlapping visual fields from two aligned eyes.

What visual disorder involves misaligned eyes and loss of depth perception?

Strabismus (crossed eyes).

When must strabismus be corrected to prevent permanent vision loss?

Before roughly age 8 (now often before age 4).

Which sensory disorder may be addressed by gene or stem-cell therapy targeting photoreceptors?

Genetic forms of blindness, including macular degeneration.

Name the three tiny middle-ear bones that amplify sound.

Malleus (hammer), incus (anvil), and stapes (stirrup).

What membrane does the stapes press on to transfer vibrations to the inner ear?

The oval window.

Which cochlear structure is tuned along its length to specific sound frequencies?

The basilar membrane.

What sensory receptors transduce cochlear vibrations into electrical signals?

Hair cells with stereocilia.

Opening of ion channels in stereocilia leads to excitation of which nerve?

The auditory nerve.

Which brain region acts as a relay for auditory information before the cortex?

The thalamus (medial geniculate nucleus).

What temporal-lobe area processes speech comprehension?

Wernicke’s area (part of left auditory cortex).

Why does most permanent hearing loss occur?

Loss of cochlear hair cells, which do not naturally regenerate.

How many basic taste qualities are there, and what are they?

Five—sweet, sour, salty, bitter, and umami.

Taste signals reach the brain via which three cranial nerves?

Facial, glossopharyngeal, and vagus nerves.

Where in the cortex is taste perception identified?

Gustatory cortex in the frontal lobe and insula.

What distinguishes olfactory processing from other senses regarding the thalamus?

Olfactory signals reach cortex without first passing through the thalamus.

Approximately how many olfactory receptor types do humans possess?

About 1,000 types.

What brain structure first receives input from olfactory receptor neurons?

The olfactory bulb.

Which brain area combines odor and taste information to create flavor perception?

Regions near the primary olfactory cortex, including inferior frontal lobe.

What is notable about neurogenesis in the olfactory system?

Olfactory receptor neurons and some bulb neurons are continually replaced throughout life.

Which skin organ is the primary structure for touch sensation?

The skin itself, containing diverse touch receptors.

What are A-beta fibers?

Myelinated, thick sensory fibers that transmit touch signals quickly.

What mapping organizes the somatosensory cortex?

A topographic (somatotopic) map representing the body surface.

Define two-point discrimination.

The minimum distance at which two separate touch stimuli are perceived as distinct.

What specialized sensory fibers detect potentially damaging stimuli?

Nociceptors.

Which chemical released during tissue injury heightens pain sensitivity and can cause allodynia?

Prostaglandins.

Differentiate A-delta and C fibers in pain transmission.

A-delta fibers are myelinated and carry fast, sharp pain; C fibers are unmyelinated and carry slow, dull, diffuse pain or itch.

What is neuropathic pain?

Chronic hypersensitivity or pain caused by malfunctioning nerves, not an active injury (e.g., diabetic neuropathy).

Which midbrain structure activates descending pain-modulating pathways?

Periaqueductal gray matter.

Name the body’s natural opioid peptides involved in pain modulation.

Endorphins.

How does adrenaline affect pain?

Acts as a natural analgesic in stressful, fight-or-flight situations.

Why can treatments like meditation or hypnosis reduce pain perception?

They target the emotional component of pain processing rather than blocking sensory input.

Which sensory neurons are unique in being regularly replaced during life?

Olfactory receptor neurons (and taste receptor cells).

What common compound in spicy food activates nociceptors to produce a burning sensation?

Capsaicin.

Which receptors mediate itch caused by histamine release?

Histamine-sensitive nociceptors.

What therapy parallels cochlear implants for vision loss by stimulating ganglion cells directly?

Retinal prostheses that send electrical signals to the optic nerve/brain.

Which age-related change reduces taste and smell sensitivity?

Decline in regeneration of taste receptor and olfactory neurons.

How quickly can humans identify an odor after sniffing, according to research?

In as little as 110 milliseconds.