Sensory Systems and Pathways: Key Concepts for Biology and Neuroscience

What is the difference between sensation and perception?

Sensation is the process of converting stimuli into nerve impulses, while perception is the brain's interpretation of that sensory information.

What is an adequate stimulus?

The specific type of energy or stimulus to which a sensory receptor is most sensitive, such as light for photoreceptors.

What are the functional categories of sensory receptors?

Thermoreceptors (temperature), Mechanoreceptors (mechanical changes), Nociceptors (pain), Photoreceptors (light), Chemoreceptors (chemicals).

What are the structural categories of sensory receptors?

Free nerve endings (pain, temperature, smell), Encapsulated nerve endings (pressure, touch), Specialized receptor cells (rods/cones for sight, hair cells for hearing).

What are the location-based categories of sensory receptors?

Exteroceptors (external environment), Interoceptors (internal environment), Proprioceptors (body position in space).

What is a receptor field?

The physical area that can be sensed by a single sensory unit (neuron and its receptors).

How does the size of receptor fields affect sensory discrimination?

Smaller receptor fields allow for finer localization of stimuli, while larger fields provide less precise information.

How do afferent neurons signal varying stimulus intensity?

Through Frequency Coding (increased action potential frequency with stronger stimuli) and Recruitment (activating more neurons).

What is lateral inhibition?

A process that sharpens stimulus perception by having strongly stimulated neurons inhibit their less-stimulated neighbors.

What is the Dorsal Column-Medial Lemniscal Pathway?

An ascending pathway that carries fine touch, pressure, vibration, and proprioception information to the somatosensory cortex.

What is the Spinothalamic Pathway?

An ascending pathway that carries pain and temperature information to the somatosensory cortex.

What are the three primary layers of the eye?

Outer Fibrous Layer (Sclera and Cornea), Intermediate Vascular Layer (Iris and Choroid), Deep Nervous Layer (Retina).

What is the path of light through the eye?

Cornea → Aqueous Humor → Pupil → Lens → Vitreous Humor → Fovea (on Retina).

What is the path of visual neurons to the occipital lobe?

Photoreceptors → Bipolar cells → Ganglion cells → Optic Nerve → Optic Chiasm → Thalamus → Primary Visual Cortex.

What is the function of the external ear?

To collect and conduct sound waves to the eardrum.

What is the function of the middle ear?

To convert sound waves into mechanical vibrations via the ossicles (malleus, incus, stapes).

What is the function of the inner ear?

Contains the cochlea, which transduces vibrations into neural signals and detects pitch and amplitude.

How can a single stimulus produce multiple sensations?

A stimulus can activate multiple receptor types, leading to complex perceptions, such as mouthwash stimulating both chemoreceptors and thermoreceptors.

How can two-point discrimination tests predict receptor field size?

Areas with small receptor fields will have a smaller minimum distance for two-point discrimination compared to areas with large fields.

How does lateral inhibition affect the appearance of discrete objects?

It enhances edge definition, making light areas appear brighter and dark areas darker, creating sharp contrasts.

What happens with damage to the Dorsal Columns in the spinal cord?

It causes loss of fine touch and proprioception on the same side as the injury, below the damage level.

What happens with damage to the Spinothalamic Tract in the spinal cord?

It causes loss of pain and temperature sensation on the opposite side of the body below the injury.

What is myopia?

Nearsightedness caused by an eyeball that is too long, where the focal point falls in front of the retina.

What is hyperopia?

Farsightedness caused by an eyeball that is too short, where the focal point falls behind the retina.