Chapter 6: Peripheral Nervous System: Afferent Division & Special Senses

Vocabulary-style flashcards covering the peripheral nervous system, including sensory receptors, transduction, perception, pain mechanisms, and the special senses of vision, hearing, balance, smell, and taste.

Transduction

The process of converting energy from a stimulus into electrical signals or action potentials ($A.P.$).

Sensation

The ability to send information about environmental changes to the Central Nervous System ($CNS$).

Perception

The conscious interpretation of the external world derived from sensory input, which involves the ability to interpret environmental stimuli.

Receptor Potential

A graded potential produced when a stimulus alters a receptor's membrane permeability; its magnitude represents the intensity of the stimulus.

Rapidly adapting receptors

Receptors that quickly diminish their sensation in response to a constant stimulus, such as olfactory receptors or tactile receptors in the skin.

Slowly adapting receptors

Receptors that maintain a slow response to constant stimuli, including nociceptors (pain receptors), muscle stretch receptors, and joint proprioceptors.

Receptive Field

The area of tissue monitored by a single sensory receptor; smaller fields allow for better localization of a response.

Photoreceptors

Sensory receptors responsive to visible wavelengths of light.

Mechanoreceptors

Receptors sensitive to mechanical energy, such as stretching, which can open or close mechanically regulated ion channels.

Thermoreceptors

Sensory receptors sensitive to heat and cold.

Osmoreceptors

Receptors that detect changes in the concentration of solutes in body fluids and resultant changes in osmotic activity.

Chemoreceptors

Receptors sensitive to specific chemicals, including those for smell, taste, and the detection of $O_2$ and $CO_2$ concentrations in the blood.

Nociceptors

Pain receptors sensitive to tissue damage, distortion, or extremes in temperature.

Baroreceptors

A class of mechanoreceptors that provide information on the volume and pressure of internal organs such as the carotid sinus, lungs, bladder, and digestive tract.

Proprioceptors

Receptors that provide a sense of body position by monitoring skeletal muscle length (muscle spindles), tension (Golgi tendon organs), and joint movement.

Substance P

A pro-pain neurotransmitter that activates ascending pathways to transmit nociceptive signals to higher brain levels like the somatosensory cortex and thalamus.

Glutamate

A major excitatory neurotransmitter responsible for exaggerated hypersensitivity to an injured area, such as a sunburn.

Endogenous opiates

Naturally occurring substances in the brain, such as endorphins, enkephalins, and dynorphin, that suppress pain transmission by binding to opiate receptors.

Iris

The pigmented part of the eye containing circular and radial smooth muscles that control the amount of light entering the eye.

Cornea

The structure that contributes most extensively to the eye's total refractive ability; its curvature remains constant.

Accommodation

The process of changing the strength and shape of the lens via the ciliary muscle and suspensory ligaments to focus on near or far objects.

Presbyopia

The age-related reduction in the eye's ability to accommodate or change the lens shape for focusing.

Myopia

Nearsightedness, occurring when the eyeball is too long or the lens is too strong, causing distant images to focus in front of the retina.

Hyperopia

Farsightedness, occurring when the eyeball is too short or the lens is too weak, causing near images to focus behind the retina.

Astigmatism

The blurring of vision caused by an uneven cornea.

Rods

Photoreceptors that provide high-sensitivity vision in shades of gray, dominant in night vision and found mostly in the periphery of the retina.

Cones

Photoreceptors responsible for high-acuity color vision, concentrated in the fovea and categorized into red, green, and blue types.

Fovea

A pinhead-sized depression in the exact center of the retina containing only cones; it is the point of most distinct vision.

Cochlea

The part of the inner ear containing the Organ of Corti and receptors for converting sound waves into nerve impulses.

Vestibular apparatus

The part of the inner ear necessary for the sense of equilibrium and balance.

Vertigo

A sensation of spinning while the body is stationary, often accompanied by nausea and coordination problems.

Nystagmus

Oscillating eye movements that indicate a vestibular sensation of spinning.

Umami

A basic taste quality that responds to protein-rich chemicals, often associated with a meat flavor.