ch 10 human phys

What is a sensory receptor?

A structure that detects a stimulus and converts it into a nervous system signal.

What is a transducer?

A receptor that represents physical sensory energy in nervous-system form, usually as a change in membrane potential.

What can happen when a receptor's membrane potential changes enough?

It can reach threshold and trigger an action potential or change neurotransmitter release.

Where is sensory information integrated?

In the spinal cord or cerebral cortex.

What are the two types of sensory receptors?

Specialized neurons and specialized non-neural cells.

What is a receptive field?

The area of sensory responsibility for one sensory receptor.

What happens with large or overlapping receptive fields?

Lower discrimination ability.

What happens with small, non-overlapping receptive fields?

Higher discrimination ability.

How does sensory information reach the brain?

Through ascending spinal nerves or directly to the brain stem through cranial nerves.

What are visceral stimuli?

Stimuli coming from inside the body.

What is the perceptual threshold?

The level of stimulus necessary to cause conscious awareness.

What brain structure does most sensory information pass through before reaching the cortex?

The thalamus. Olfaction is the major exception.

What are the four properties of a stimulus?

Modality, location, intensity, and duration.

What is modality?

The type of stimulus being detected.

What is location?

Where on the body the stimulus was received.

How is stimulus intensity coded?

By the number of receptors activated and the number/frequency of action potentials generated.

How is stimulus duration coded?

By the duration of action potential generation.

What is sensory adaptation?

When a receptor stops responding to a stable or chronic stimulus.

What are the four major somatic senses?

Touch, proprioception, temperature, and nociception.

What receptors detect touch?

Mechanoreceptors.

What is proprioception?

Sensing body and limb position, stretch, and angle.

What receptors detect temperature?

Thermoreceptors.

What is nociception?

Detection of potentially damaging stimuli, including pain and itch.

Where does somatic sensory information ultimately reach the brain?

The primary somatosensory cortex (S1) in the parietal lobe.

What does it mean when sensory nerves decussate?

They cross from one side to the other.

What is pain's main physiological purpose?

To signal tissue damage and trigger protective reflexes and behaviors.

Do pain receptors normally adapt?

No. Pain does not normally adapt and can become chronic.

What are nociceptors capable of detecting?

Chemical, physical, and temperature stimuli.

How can touching a painful area reduce pain perception?

Touch can activate an inhibitory interneuron that decreases pain transmission.

What is referred pain?

Pain from an internal organ that is perceived on the body's surface.

What type of sense is olfaction?

A chemical sense.

Where are olfactory cells located?

In the olfactory epithelium of the nasal cavity.

What must happen to chemicals before they can be detected by olfactory cells?

They must dissolve in the mucus layer.

What type of receptors detect odors?

G-protein/cAMP-linked chemical receptors.

What is the pathway for smell?

Nose → olfactory bulb → olfactory tract → olfactory cortex.

What makes olfaction unique?

It has a direct pathway into the cortex and a strong connection with learning and memory.

What are the five basic taste types?

Sweet, sour, bitter, salty, and umami.

What is a population code for taste?

The collective activation of multiple taste receptors is used to encode tastes.

Where are taste receptors located?

In taste pores within taste buds of the tongue, mouth, and pharynx.

What is the basic sensory receptor for hearing?

A hair cell.

What happens when sound moves the fluid in the inner ear?

Hair-cell projections bend, changing the receptor potential and causing neurotransmitter release.

What is the pathway for hearing?

Cochlea → cochlear nerve → medulla → midbrain → thalamus → auditory cortex.

What does the outer ear do?

Funnels sound into the ear canal.

What is the tympanum?

The eardrum, which vibrates in response to sound waves.

What are the ossicles?

The small ear bones that transmit vibrations through the middle ear.

What is the cochlea?

A fluid-filled structure of the inner ear involved in hearing.

What does the basilar membrane do?

Vibrates in response to sound and helps encode different sound frequencies.

How is sound frequency encoded?

By the location on the basilar membrane where hair cells are activated.

How is sound intensity encoded?

By the number of hair cells activated.

What is conductive hearing loss?

Failure of physical sound transmission through the external or middle ear.

What is sensorineural hearing loss?

Damage to structures of the inner ear.

What is central hearing loss?

Damage to the neural pathway between the cochlea and cortex or damage to the cortex itself.

What is the vestibular apparatus responsible for?

Balance and sensing head movement/orientation.

What are the two otolith organs?

The saccule and utricle.

What do the otolith organs detect?

Linear acceleration and head position.

What do the semicircular canals detect?

Rotational acceleration.

What happens inside the vestibular organs during acceleration?

Fluid moves, causing hair-cell projections to bend.

What is the main function of vision?

To collect and process information from light.

What do photoreceptors do?

Capture light energy and convert it into changes in neurotransmitter release.

Where are photoreceptors located?

In the retina.

What controls how much light enters the eye?

The pupil.

What is accommodation?

The process of adjusting the shape of the lens to keep objects in focus.

What are the two types of photoreceptors?

Rods and cones.

What are rods used for?

Vision in low-light conditions/night vision.

What are cones responsible for?

High-acuity vision and daytime color vision.

What is the macula?

The part of the retina where light is focused during straight-ahead central vision.

What is the fovea?

The area within the macula containing the highest density of cone photoreceptors.

What is phototransduction?

The process of converting light energy into electrical signals.

What happens at the optic chiasm?

The optic nerves partially cross so visual information is organized according to the side of the visual field.

Where does the visual pathway eventually reach the cortex?

The primary visual cortex (V1) in the occipital lobe.