Memmler’s The Human Body in Health and Disease 11th edition Chapter 11 The Sensory System

The Senses Sensory system detects environmental change Environmental change initiates nerve impulse (stimulus) Stimulus interpreted by cerebral cortex Sensation experienced

Sensory Receptors Sensory receptors Distribution of sense receptors Special senses in sense organ Vision Hearing Equilibrium Taste Smell General senses throughout body Pressure, temperature, pain, touch Sense of position Sensory receptors Chemoreceptors- respond to chemicals Photoreceptors-respond to light Thermoreceptors- respond to heat Mechanoreceptors- respond to movement

Question: Which sensory receptors respond to movement. a Question: Which sensory receptors respond to movement? a. thermoreceptors b. photoreceptors c. mechanoreceptors

Answer: c. mechanoreceptors

The Eye and Vision Eye protection structures Eye cavity bones Eyelids Eyelashes and eyebrow Conjunctiva Lacrimal glands

Checkpoint 11-1: What are some structures that protect the eye?

Coats of the Eyeball Eyeball has three separate coats (tunics) Sclera Choroid Retina

The eye. Note the three tunics, the refractive parts of the eye (cornea, aqueous humor, lens, vitreous body), and other structures involved in vision.

Checkpoint 11-2: What are the names of the tunics of the eyeball?

Pathway of Light Rays and Refraction Transparent parts of the eye that refract light Cornea Aqueous humor Crystalline lens Vitreous body

Checkpoint 11-3: What are the structures that refract light as it passes through the eye?

Question: What is the name of the fluid within the eyeball. a Question: What is the name of the fluid within the eyeball? a. aqueous humor b. vitreous c. sclera

Answer: a. aqueous humor

Function of the Retina Pigmented layer Sensitive to light Rods Function in dim light Shades of gray Blurred images Cones Function in bright light Color sensitive Sharp images Connecting neurons

Checkpoint 11-4: What are the receptor cells of the retina?

Structure of the retina Structure of the retina. Rods and cones form a deep layer of the retina, near the choroid. Connecting neurons carry visual impulses toward the optic nerve.

Muscles of the Eye Two muscle groups adjust eye so retina can receive clear image

The Extrinsic Muscles Outer surface of eyeball Voluntary Control convergence for three-dimensional vision

Extrinsic muscles of the eye. The medial rectus is not shown. ZOOMING IN • What characteristics are used in naming the extrinsic eye muscles?

Checkpoint 11-5: What is the function of the extrinsic muscles of the eye?

The Intrinsic Muscles Within eyeball Iris regulates amount of light entering eye Ciliary muscle shapes lens for near and far vision

The ciliary muscle and lens (posterior view) The ciliary muscle and lens (posterior view). Contraction of the ciliary muscle relaxes tension on the suspensory ligaments, allowing the lens to become more round for near vision.  ZOOMING IN • What structures hold the lens in place?

Checkpoint 11-6: What is the function of the iris? Checkpoint 11-7: What is the function of the ciliary muscle?

Nerve Supply to the Eye Optic nerve (cranial nerve II) Ophthalmic branch of trigeminal nerve (cranial nerve V) Oculomotor nerve (cranial nerve III) Trochlear (cranial nerve IV) Abducens (cranial nerve VI)

Nerves of the eye.  ZOOMING IN • Which of the nerves shown moves the eye?

Checkpoint 11-8: What is cranial nerve II and what does it do?

Errors of Refraction and Other Eye Disorders Hyperopia Myopia Astigmatism Strabismus Convergent Divergent Amblyopia Infections Conjunctivitis Inclusion conjunctivitis Ophthalmia neonatorum Injuries Cataract Glaucoma Disorders involving the retina Diabetic retinopathy Macular degeneration

Checkpoint 11-9: What are some errors of refraction?

The Ear Sense organ for hearing and equilibrium Outer ear Middle ear Inner ear

The ear. Structures in the outer, middle, and inner divisions are shown

The Outer Ear Pinna (auricle) Directs sound waves into ear External auditory canal (meatus) Ceruminous glands Tympanic membrane Vibrates as sound waves enter ear

Question: What is the anatomic name for the external part of the ear Question: What is the anatomic name for the external part of the ear? (that funny-looking curved part that sticks out from the side of your head) a. malleus b. meatus c. pinna

Answer: c. pinna

The Middle Ear and Ossicles Middle ear cavity contains ossicles (small bones) that amplify sound waves and transmit sounds to inner ear Malleus (hammer) Incus (anvil) Stapes (stirrup)

Checkpoint 11-10: What are the ossicles of the ear and what do they do?

Eustachian Tube Connects middle ear cavity with throat (pharynx) Allows pressure to equalize on both sides of tympanic membrane Continuous mucous membrane from pharynx to middle ear cavity

The Inner Ear Bony labyrinth Vestibule Semicircular canals Cochlea Perilymph fluid Membranous labyrinth Endolymph fluid

The inner ear. The vestibule, semicircular canals, and cochlea are made of a bony shell (labyrinth) with an interior membranous labyrinth. Endolymph fills the membranous labyrinth and perilymph is around it in the bony labyrinth.

Hearing Organ of Corti Located in membranous cochlea (cochlear duct) Ciliated receptor cells Tectorial membrane

Question: True or False: The cochlea is in the middle ear.

Answer: False: The cochlea is in the inner ear.

Cochlea and the organ of Corti. The arrows show the direction of sound waves in the cochlea.

Checkpoint 11-11: What is the name of the organ of hearing and where is it located?

Equilibrium Ciliated equilibrium sensory receptors are located in vestibule and semicircular canals Types of equilibrium Static Maculae receptors Otoliths fluid Dynamic Cristae receptors

Action of the receptors (maculae) for static equilibrium Action of the receptors (maculae) for static equilibrium. As the head moves, the thick fluid above the receptor cells, weighted with otoliths, pulls on the cilia of the cells, generating a nerve impulse. ZOOMING IN • What happens to the cilia on the receptor cells when the fluid around them moves?

Action of the receptors (cristae) for dynamic equilibrium Action of the receptors (cristae) for dynamic equilibrium. As the body spins or moves in different directions, the cilia bend as the head changes position, generating nerve impulses.

Checkpoint 11-12: Where are the receptors for equilibrium located? Checkpoint 11-13: What are the two types of equilibrium?

Otitis and Other Disorders of the Ear Otitis media Otitis externa Hearing loss Conductive hearing loss Sensorineural hearing loss Presbycusis

Other Special Sense Organs Taste and smell sense organs respond to chemical stimuli

Sense of Taste Taste receptors (buds) on tongue Stimulated by substance in solution Basic tastes Sweet Salty Sour Bitter Other tastes Water Alkaline Metallic Umami Cranial nerves Facial (VII) Glossopharyngeal (IX)

Special senses that respond to chemicals. Organs of taste (gustation) and smell (olfaction). (B) A taste map of the tongue.

Sense of Smell Smell receptors in nasal cavity Stimulated by substances in solution in nasal fluids Smells stimulate appetite and flow of digestive juices Olfactory nerve (cranial nerve I)

Checkpoint 11-14: What are the special senses that respond to chemical stimuli?

The General Senses Receptors scattered throughout the body sense Touch Pressure Heat Cold Position Pain

Sense of Touch Sense of Pressure Tactile corpuscles Found mostly in dermis of skin and around hair follicles Sensitivity varies with the number of receptors Baroreceptors in walls of large arteries monitor blood pressure and trigger responses that control BP as vessels stretch. Sense of Pressure Receptors for deep touch located In subcutaneous tissues Near joints, muscles, and other deep tissues

Sense of Temperature Temperature receptors Are free nerve endings Are widely distributed in the skin Are separate for heat and cold Occur in hypothalamus of brain Help to adjust body temperature according to temperature of circulating blood

Sense of Position Proprioceptors (position receptors) Are located in muscles, tendons, joints Relay impulses of body parts in relation to each other Send impulses to the cerebellum for coordination

Checkpoint 11-15: What are examples of general senses? Checkpoint 11-16: What are proprioceptors and where are they located?

Question: Temperature receptors in what part of the brain regulate body temperature according to circulating blood temperature? a. hypothalamus b. medulla oblongata c. cerebral cortex

Answer: a. hypothalamus

Sense of Pain Pain receptors Are free nerve endings Are found in skin, muscles, joints and (to a lesser extent) in most internal organs Pain relief Analgesic drugs Anesthetics Endorphins Heat or cold Relaxation or distraction techniques

Sensory Adaptation Occurs when receptors are exposed to continuous stimulus Some receptors can adjust themselves so sensation becomes less acute Receptors adapt at different rates Pain receptors do not adapt

End of Presentation