Chapter 12 Nervous System III: Senses

Flashcards about the senses.

General (somatic) senses

Receptors that are widely distributed throughout the body (found in skin, various organs & joints).

Special senses

Specialized receptors confined to complex structures in the head (found in eyes, ears, nose & mouth): Hearing, Equilibrium, Vision, Olfaction (Smell), and Gustation (Taste)

Sensory receptors

Specialized cells that collect information from the environment; can be Free Nerve Endings or special Sensory Receptor Cells close to nerve endings

Sensation

A feeling that occurs when the brain becomes aware of a sensory impulse.

Perception

A person’s view of the stimulus; the way the brain interprets the information

Sensory Adaptation

Ability to ignore unimportant stimuli; involves a decreased response to a particular stimulus from the receptors (Peripheral Adaptation) or along the CNS pathways leading to the cerebral cortex (Central Adaptation)

Peripheral Adaptation

An adjustment made by Sensory Receptors, upon continuous stimulation, until no more impulses are sent out.

Chemoreceptors

Respond to changes in the chemical concentrations of different ions & molecules; some exhibit Sensory Adaptation.

Pain Receptors (Nociceptors)

Respond to tissue damage; do NOT exhibit Sensory Adaptation

Thermoreceptors

Respond to moderate changes in temperature; Exhibit Sensory Adaptation; There are Heat (Warm) receptors, and Cold receptors.

Photoreceptors

Receptors that respond to light; Found in retina of eye

Mechanoreceptors

Respond to mechanical forces that distort shape of cell membranes (or deform the receptor)

Tactile Receptors

Sensitive to touch, pressure or vibration; Free Nerve Endings; Hair Root Plexus; Merkel’s Discs; Meissner’s Corpuscles (Disks); Pacinian Corpuscles

Baroreceptors (Pressoreceptors)

Detect changes in hydrostatic pressure; Found in elastic tissue in the walls of blood vessels.

Stretch Receptors

Sense changes in the degree of stretching or inflation; Example: Receptors in lungs.

Proprioceptors

Detect changes in position of joints, tension in tendons & ligaments, and state of muscle contraction; Golgi Tendon Organs and Muscle Spindles

Somatic (General) Senses

Senses associated with receptors in skin, muscles, joints & viscera; Exteroceptive, Visceroceptive, and Proprioceptive.

Exteroceptive senses (exteroceptors)

Senses associated with body surface such as touch, pressure, vibration, temperature, & pain

Visceroceptive senses (interoceptors)

Senses associated with changes in the viscera such as blood pressure stretching blood vessels & ingestion of a meal

Proprioceptive senses

Senses associated with changes in muscles and tendons such as at joints

Sense of Pain

Pain receptors consist of Free nerve endings; Stimulated by tissue damage, chemical, mechanical forces, or extremes in temperature; Little or no Sensory Adaptation.

Antinociceptive System

Endorphins, Encephalins, Substances released from specific areas in the brain in response to pain impulses. Inhibit the transmission of pain impulses, and are a form of natural pain control.

Visceral Pain

Pain receptors are the only receptors in viscera whose stimulation produces sensations; not well localized; feels as if coming from some other part of the body (Referred Pain)

Referred Pain

Pain that feels as if it is coming from a part of the body other than its site of origin; example: Pain originating in the Heart is often felt in the left shoulder or left arm.

Acute pain

Sharp pain; Often originate in the skin; Well localized; Conducted by thin, myelinated nerve fibers rapidly.

Chronic pain

Dull, aching pain; Difficult to pinpoint; Can continue for a long time after the stimulus is removed; Conducted by thin, unmyelinated nerve fibers slowly

Pain Threshold

Intensity of pain stimulus that triggers a neural response; Is similar for different people but each person’s emotional response to pain is different.

External Ear

Auricle (Pinna); External Auditory Meatus (Canal); Tympanic Membrane

Middle Ear

Tympanic Cavity, 3 auditory Ossicles: Malleus (hammer), Incus (anvil), and Stapes (stirrup); Oval window.

Tympanic Reflex

Occurs after a loud sound begins. Reduces the pressure from loud sounds that might damage the Hearing Receptors. Tensor Tympani Muscle and Stapedius Muscle

Auditory (Eustachian) Tube

Tube that connects middle ear to throat; Helps maintain equal pressure on both sides of tympanic membrane; Allows air to pass between the Tympanic Cavity and the outside of the body.

Inner Ear

Osseous Labyrinth filled with Perilymph & Membranous Labyrinth filled with Endolymph; Vestibule, Semicircular Canals, and Cochlea

Cochlea

Spiral-shaped portion of the Bony Labyrinth; Functions in hearing; Vestibular Duct (Scala Vestibuli) and Tympanic Duct (Scala Tympani)

Cochlear Duct (Scala Media)

Portion of membranous labyrinth in cochlea between the 2 bony compartments. Filled with Endolymph; Contains Organ of Corti.

Organ of Corti

The sensory organ of hearing; Located on upper surface of Basilar Membrane; Contains Hair Cells, group of hearing receptors.

Hearing Loss

About 8% of people have some degree of hearing loss; Conductive and Sensorineural

Static Equilibrium

Senses position of head when body is not moving and maintains posture & balance; Organs are located in Vestibule (Utricle & Saccule)

Dynamic Equilibrium

Senses rotation and movement of head and body and maintains balance; Organs are located in Semicircular Canals

Olfactory Organs

Contain Olfactory Epithelium & Olfactory (Bowman’s) Glands; Found in upper parts of nasal cavity.

Olfactory Nerve Pathways

Olfactory nerves to olfactory bulbs to olfactory tracts to Limbic System and Olfactory Cortex

Anosmia

Any olfactory disorder, or inability to smell. Due to a variety of causes.

Taste Buds

Sensory receptor organs of taste; Located mainly in papillae of tongue; Taste Cells (Receptors), Taste Hairs, and Taste Pores.

Taste Sensations

Sweet, Sour, Salty, Bitter, Alkaline, Metallic, and Umami

Visual accessory organs

Eyelids, Eyelashes, Lacrimal apparatus, and Extrinsic eye muscles

Lacrimal Apparatus

System producing tears to wash surface of eye, keep it moist & remove tears from eye; Lacrimal Gland, Ducts (Canaliculi) & Sac, and Nasolacrimal Duct

Structure of the Eye

Outer Fibrous tunic, Middle Vascular tunic, and Inner Nervous tunic

Fibrous (Outer) Tunic

Cornea and Sclera

Vascular (Middle) Tunic

Iris, Ciliary Body, Choroid Coat

Accommodation

Changing of Lens shape (thickening) that occurs when eye focuses to view close objects

Nervous (Inner) Tunic

Retina; Macula Lutea, Fovea Centralis; Optic Disc

Anterior Portion (Cavity) of Eye

Space enclosed by Cornea & Lens; Filled with Aqueous Humor; Anterior Chamber, and Posterior Chamber

Retinal Neurons

Photoreceptor cells, Bipolar cells, Ganglion cells, Horizontal cells, and Amacrine cells

Visual Pigments

Rhodopsin (in Rods); Erythrolabe, Chlorolabe, & Cyanolabe (in Cones)

Light Refraction

Bending of light as it enters eye; Image focused on retina is upside down and reversed from left to right

Visual Acuity

Ability of a person to distinguish between 2 points from a certain distance; such as 20/20, 20/50, and 20/15

Stereoscopic Vision

Provides perception of distance, depth, height and width of objects

Astigmatism

Distorted vision, resulting from a defect in the curvature of the Cornea or Lens.

Night Blindness

Poor vision in dim light; due to Vitamin A deficiency.

Color Blindness

Inability to distinguish certain colors, due to a lack of normal Cone Pigments.

Detached Retina

Separation of the Retina from the Choroid Coat; May cause visual loss or blindness.