Chapter 13 Senses

Outline Types of Sensory Receptors Sense of Taste Sense of Smell Sense of Vision Focusing Integration of Visual Signals Abnormalities of the Eye Sense of Hearing Sense of Equilibrium

Sensory Receptors and Sensations Sensory receptors are specialized to detect certain types of stimuli. Exteroceptors detect stimuli outside the body. Taste, smell, vision. Interoceptors detect stimuli inside the body. Blood pressure, blood volume, pH.

Types of Sensory Receptors Chemoreceptors. Respond to chemical substances in the immediate vicinity. Pain Receptors. Respond to chemicals released by damaged tissue. Mechanoreceptors. Stimulated by mechanical forces. Thermoreceptors. Stimulated by changes in temperature.

How Sensation Occurs Sensation occurs when nerve impulses arrive at the cerebral cortex of the brain. Perception occurs when the cerebral cortex interprets the meaning of sensations. All sensory receptors initiate nerve impulses; the sensation that results depends on the part of the brain receiving the nerve impulses.

Sensation

Proprioceptors Proprioceptors are mechanoreceptors that help determine limb position in space by detecting the degree of muscle relaxation, stretch of tendons, and movement of ligaments. Muscle spindles act to increase the degree of muscle contraction, while Golgi tendon organs act to decrease it.

Muscle Spindle

Cutaneous Receptors The dermis contains cutaneous receptors, which include: Mechanoreceptors. Sensitive to touch. Nociceptors. Sensitive to pain. Thermoreceptors. Sensitive to temperature.

Sensory Receptors in Human Skin

Chemical Senses Sense of Taste. Receptors for taste are found in taste buds located primarily embedded in tongue epithelium. Four primary tastes. Sweet. Sour. Salty. Bitter.

Taste Buds

Sense of Smell Sense of smell is dependent on olfactory cells located within olfactory epithelium high in the roof of the nasal cavity. Olfactory bulbs have direct connections with the limbic system and its centers for emotions and memory. Sense of taste and smell work together to create a combined effect.

Olfactory Cell Location and Anatomy

Sense of Vision The eyeball has three layers. Sclera. Choroid. Retina. The retina contains two types of photoreceptors. Rods. Cones.

Anatomy of the Human Eye

Focusing When looking at an object, light rays pass through the pupil and are focused on the retina. Focusing starts with the cornea and continues as the rays pass through the lens and the humors.

Focusing

Photoreceptors Vision begins once light has been focused on the photoreceptors in the retina. Rods are very sensitive to light and therefore are suited to night vision. Cones allow detection of fine detail and color. Color vision depends on three different kinds of cones which contain blue, green, and red pigments.

Photoreceptors in the Eye

Integration of Visual Signals in the Retina The retina has three layers. Layer closest to choroid contains rod cells and cone cells. Middle layer contains bipolar cells. Innermost layer contains ganglion cells. Only rod and cone cells are light-sensitive, thus light must penetrate to the back of the retina before they are stimulated.

Structure and Function of the Retina

Integration of Visual Signals in the Brain The visual pathway begins in the retina and passes through the thalamus before reaching the cerebral cortex. The pathway and visual cortex take the visual field apart, and the cortex rebuilds it so we correctly perceive the field.

Optic Chiasma

Abnormalities of the Eye Color blindness. Particular type of cone is lacking. Distance Vision Nearsighted. Elongated eyeball. Farsighted. Shortened eyeball. Astigmatism. Uneven cornea.

Eye Abnormalities and Corrective Lenses

Sense of Hearing Anatomy of the Ear. Outer ear consists of the pinna and the auditory canal. Middle ear begins at tympanic membrane and ends at bony wall with a round window and oval window. Ossicles found between tympanic membrane and the oval window.

Sense of Hearing Anatomy of the Ear. Inner ear consists of semicircular canals, vestibule, and cochlea.

Human Ear

Process of Hearing When the basilar membrane (spiral organ) vibrates, stereocilia of the hair cells bend, and nerve impulses are transmitted to the brain.

Mechanoreceptors for Hearing

Sense of Equilibrium Cupula movement within the semicircular canals detects rotation and/or angular movement of the head. Rotational Equilibrium. Movement of the otolithic membrane within the utricle and the saccule detects movement of the head in the vertical and horizontal planes. Gravitational Equilibrium.

Review Types of Sensory Receptors Sense of Taste Sense of Smell Sense of Vision Focusing Integration of Visual Signals Abnormalities of the Eye Sense of Hearing Sense of Equilibrium