Human Biology Sylvia S. Mader Michael Windelspecht Chapter 14 Senses Lecture Outline Part 1 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Senses See separate FlexArt PowerPoint slides for all figures and tables pre-inserted into PowerPoint without notes 2

Points to ponder What are sensory receptors? How do we detect the sense of taste and smell? What is the anatomy of the eye? How do we focus images? What are some eye abnormalities? What is the anatomy of the ear? Which parts function in balance and which parts function in hearing?

14.1 Overview of Sensory Receptors and Sensations Sensory receptors – dendrites specialized to detect certain types of stimuli ___________: detect stimuli from outside the body (e.g., taste, hearing, vision) ___________: receive stimuli from inside the body (e.g., change in blood pressure)

Types of sensory receptors 14.1 Overview of Sensory Receptors and Sensations Types of sensory receptors Chemoreceptors – respond to nearby chemicals _____________ (pain receptors) – chemoreceptors that respond to chemicals released by damaged tissue _____________ – respond to light energy Mechanoreceptors – respond to mechanical forces such as pressure ______________ – stimulated by temperature changes

Senses and the receptors involved 14.1 Overview of Sensory Receptors and Sensations Senses and the receptors involved

How does sensation occur? 14.1 Overview of Sensory Receptors and Sensations How does sensation occur? Sensory receptors respond to environmental stimuli. Nerve impulses travel to the cerebral cortex and sensation (conscious perception of stimuli) occurs. ____________, decrease in stimulus response, can occur with repetitive stimuli (i.e., odor).

How does sensation occur? 14.1 Overview of Sensory Receptors and Sensations How does sensation occur? Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Peripheral Nervous System stimulus sensory receptor nerve impulses along sensory fiber spinal cord brain Central Nervous System Figure 14.1 The role of the CNS and PNS in sensation and sensory perception. 8

Proprioceptors 14.2 Somatic Senses Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 1 muscle spindle 2 muscle fiber 2 1 quadriceps muscle bundle of muscle fibers 3 sensory neuron to spinal cord Golgi tendon organ tendon Figure 14.2 The action of a muscle spindle.

14.2 Somatic Senses Cutaneous receptors Receptors in the dermis that make the skin sensitive to touch, pressure, pain, and temperature. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. epidermis free nerve endings (pain, heat, cold) Meissner corpuscles (touch) Merkel disks (touch) Pacinian corpuscles (pressure) Krause end bulbs (touch) Ruffini endings (pressure) dermis root hair plexus (touch) Figure 14.3 Sensory receptors of the skin.

14.3 Senses of Taste and Smell Taste receptors 4,000 taste buds are located primarily on the tongue of adult humans. We have 5 main types of taste receptors: sweet, sour, salty, bitter, and umami (savory). 80-90% of what we perceive as taste is actually due to the sense of ______.

b (both): © Omikron/SPL/Photo Researchers 14.3 Senses of Taste and Smell Taste receptors Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. tonsils epiglottis sensory nerve fiber supporting cell taste pore 10 μm papillae taste bud connective tissue taste cell microvilli a. Tongue b. Papillae c. Taste bud b (both): © Omikron/SPL/Photo Researchers Figure 14.4 The tongue and the sense of taste. 12

14.3 Senses of Taste and Smell Smell receptors Depends on 10-20 million olfactory cells (modified neurons) in the roof of the nasal cavity Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. olfactory bulb neuron olfactory tract frontal lobe of cerebral hemisphere olfactory bulb olfactory epithelium bone of skull nasal cavity odor molecules sensory nerve fibers olfactory epithelium a. supporting cell olfactory cell olfactory cilia of olfactory cell Figure 14.5 The sense of smell. b. odor molecules

Anatomy of the eye Made of 3 layers/coats 14.4 Sense of Vision Anatomy of the eye Made of 3 layers/coats ______: mostly white and fibrous except the cornea ______: darkly-pigmented vascular layer ______: inner layer containing photoreceptors 14

Anatomy of the eye 2 compartments 14.4 Sense of Vision Anatomy of the eye 2 compartments Anterior compartment: between the cornea and lens; filled with a clear fluid called _________ humor Posterior compartment: most of the eye, behind the lens; contains a gelatinous material called ________ humor 15

Anatomy of the eye 14.4 Sense of Vision Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. sclera choroid retina ciliary body retinal blood vessels lens iris optic nerve pupil fovea centralis cornea posterior compartment filled with vitreous humor anterior compartment filled with aqueous humor retina suspensory ligament choroid sclera Figure 14.6 The structures of the human eye.