senses

What are the four major stages of sensory processing?

Reception, transduction, encoding & transmission, and perception.

What is reception in sensory systems?

The sampling, focusing, or amplification of environmental stimuli onto sensory receptors.

What is transduction?

The conversion of physical or chemical stimuli into electrical signals.

What is encoding and transmission?

The process by which neural signals are carried through sensory pathways.

What is perception?

The extraction and interpretation of useful information from sensory signals.

What is the principle of labelled lines?

Each sensory modality is carried by a dedicated neural pathway.

What are retinotopic maps?

Spatial maps of visual information in the brain.

What are tonotopic maps?

Spatial maps of sound frequency in the brain.

What are chemotopic maps?

Spatial maps of chemical stimuli in sensory systems.

How is stimulus intensity encoded?

By firing rate and the number of activated axons.

What are the four sensory systems covered in this lecture?

Vision, audition, olfaction, and gustation.

What is the function of the eye?

To focus light onto the retina.

Where is light focused in the eye?

On the retina.

What are the two major photoreceptor types?

Rods and cones.

What are rods specialised for?

Vision in low light conditions.

What are cones specialised for?

Daylight vision and colour vision.

What cells transmit signals from photoreceptors towards the brain?

Ganglion cells.

What is the optic nerve formed from?

The axons of retinal ganglion cells.

What is the role of horizontal cells?

Modulation of retinal signalling.

What is the role of amacrine cells?

Modulation of retinal signalling.

What is phototransduction?

The conversion of light into neural signals.

What replenishes photoreceptors with pigment?

The retinal pigment epithelium.

What is the main visual pathway in mammals?

Retina → lateral geniculate nucleus → primary visual cortex.

What does LGN stand for?

Lateral geniculate nucleus.

Where is the lateral geniculate nucleus located?

In the thalamus.

What is V1?

The primary visual cortex.

What is another name for V1?

The striate cortex.

Which cortical area receives visual information from the LGN?

Primary visual cortex (V1).

What is sound?

A series of pressure changes forming a wave.

What are the three ossicles of the middle ear?

Malleus, incus, and stapes.

What is another name for the malleus?

Hammer.

What is another name for the incus?

Anvil.

What is another name for the stapes?

Stirrup.

What is the function of the ossicles?

To transmit pressure waves from air into fluid-filled structures of the inner ear.

How much greater is the force at the oval window compared with the original pressure wave?

Approximately 22 times greater.

What is the cochlea?

A snail-shaped structure of the inner ear responsible for hearing.

What does cochlea mean?

Snail.

What structure contains the sensory receptors for hearing?

The organ of Corti.

Where is the organ of Corti located?

In the cochlear duct (scala media).

What happens when sound vibrations reach the organ of Corti?

It moves against the tectorial membrane.

Which cells are the sensory receptors of hearing?

Inner hair cells.

What part of hair cells detects movement?

Stereocilia.

What type of transduction occurs in hair cells?

Mechano-electrical transduction.

What ion is abundant in endolymph?

K+.

What happens when stereocilia bend?

K+ channels open.

What effect does opening K+ channels have on hair cells?

Depolarisation.

What opens after depolarisation of hair cells?

Voltage-gated Ca2+ channels.

What triggers neurotransmitter release from hair cells?

Ca2+ influx.

What is the main auditory pathway?

Cochlea → brainstem → thalamus → auditory cortex.

What type of map exists in the auditory system?

A tonotopic map.

What is olfaction?

The sense of smell.

What is the sensory receptor for smell?

Olfactory receptor neurons.

Where are olfactory receptor neurons located?

In the olfactory epithelium.

Through what structure do olfactory axons pass to reach the brain?

The cribriform plate.

What is the first stage of olfactory processing?

The olfactory bulb.

What is unusual about the olfactory pathway compared with most sensory systems?

It bypasses the thalamus initially.

Which brain structure involved in emotion receives direct olfactory input?

The amygdala.

Which brain structure involved in memory receives direct olfactory input?

The hippocampus.

Why are smells strongly linked to memories?

Olfactory pathways project directly to memory-related structures.

What is gustation?

The sense of taste.

What is the main organ of taste?

The tongue.

Which additional structures contribute to taste?

The pharynx, palate, and epiglottis.

What sensory system strongly contributes to taste perception?

Olfaction.

What non-chemical factors contribute to taste perception?

Visual appearance and texture.

What is the first step in taste perception?

Breakdown and solubilisation of food by saliva.

What are papillae?

Taste-sensitive structures on the tongue.

Which papillae are the largest?

Circumvallate papillae.

Where are circumvallate papillae located?

Posterior tongue.

Which papillae are located along the posterior lateral edge of the tongue?

Foliate papillae.

Which papillae are widespread across the anterior tongue and tip?

Fungiform papillae.

Where are taste buds located?

In circumvallate, foliate, and fungiform papillae.

How many basic taste modalities are detected across the tongue?

Five.

Are different tastes restricted to specific tongue regions?

No, all five modalities can be detected across the tongue.

What is the sequence of taste transduction?

Stimulus binding → depolarisation → increased intracellular Ca2+ → neurotransmitter release → activation of afferent fibres.

What initiates taste transduction?

Dissolved molecules interacting with receptors.

What electrical change occurs during taste transduction?

Membrane depolarisation.

What intracellular ion increases during taste transduction?

Ca2+.

What triggers neurotransmitter release from taste cells?

An increase in intracellular Ca2+.

What do released neurotransmitters activate in taste pathways?

Afferent nerve fibres.

Where do first-order gustatory neurons project?

The medulla.

Where do second-order gustatory neurons project?

The thalamus.

Where do third-order gustatory neurons project?

The gustatory cortex.

What is the gustatory cortex?

The cortical region responsible for taste perception.

Which sensory system projects directly to limbic structures without first relaying through the thalamus?

Olfaction.

Which sensory system relies on inner hair cells as receptors?

Audition.

Which sensory system relies on rods and cones as receptors?

Vision.

Which sensory system relies on taste receptor cells within taste buds?

Gustation.