Upload
aaliyah-sandoval
View
218
Download
1
Tags:
Embed Size (px)
Citation preview
The Sensory System
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Introduction
A stimulated sensory receptor sends a signal to the brain
Signals are interpreted in the brain
Introduction
Five types of sensory receptorsMechanoreceptors – stimulated by changes in
pressure or body movementThermoreceptors – stimulated by changes in the
external or internal temperaturePain receptors – stimulated by damage or oxygen
deprivation to the tissuesChemoreceptors – stimulated by changes in the
chemical concentrations of substancesPhotoreceptors – stimulated by light energy
General Senses
ProprioceptorsMechanoreceptors involved in reflex actionsMaintain equilibrium and posture
Fig 9.1
General Senses Cutaneous Receptors
Located in the deepest layer of the epidermis and the entire dermis
Make skin sensitive to touch, pressure, pain, and temperature
General Senses Pain Receptors (nociceptors)
Somatic nociceptors○ Skin and skeletal muscle○ Respond to mechanical, thermal, electrical or
chemical damage
Senses of Taste and Smell
Chemical senses Sensitive to molecules in food and in the air Other chemoreceptors in the body
Govern respiratory rateSensitive to the hydrogen ion concentration of the
blood
Senses of Taste and Smell Sense of Taste
Sensory receptors located in the taste buds○ Primarily on the tongue○ Also present on the hard palate, the pharynx, and
the epiglottisTypes of taste sensations
○ Sweet○ Sour○ Salty○ Bitter○ Umami – meat
Senses of Taste and Smell
How the brain receives taste information○ Molecules in food bind with receptor proteins on
microvilli on taste cells○ Nerve impulses are generated and go to the brain○ Sensory receiving and memory areas for taste are
located in the insula
Senses of Taste and Smell
Sense of SmellDependent on olfactory cells
○ Located in olfactory epithelium in the roof of the nasal cavity
○ Modified neurons○ Olfactory cilia have receptor proteins for odor
moleculesHow the brain receives odor information
Senses of Taste and Smell
How the brain receives odor information○ Nerve fibers lead to the olfactory bulb○ Combinations of activated receptor proteins account
for different odors ○ An odor’s signature is determined by which neurons
are stimulated in the olfactory bulb○ Neurons send signals through the olfactory tract to
the olfactory areas of the cerebral cortex in the temporal lobe
Senses of Taste and Smell
Sense of taste and sense of smell○ Both work together○ Smell can enhance taste○ Part of what is referred to as smell may actually be
taste
Sense of Vision
Accessory Organs of the EyeEyebrows, eyelids, and eyelashes
○ Eyebrows shade the eyes from the sun and protect eyes from perspiration or debris
○ Eyelids are continuations of the skin○ Eyelashes can block debris from entering the eye○ Secretions from sebaceous glands associated with
eyelashes lubricate the eye○ Eyelids help keep the eye lubricated
Fig 9.5a
Sense of Vision
Lacrimal apparatus○ Lacrimal gland produces
tears○ Tears collect in lacrimal
sac○ Tears drain into the nose
by the nasolacrimal duct
Sense of Vision
Extrinsic muscles○ Contractions move the eyes○ Superior rectus rolls eye upward○ Inferior rectus rolls eye downward○ Lateral rectus turns eye outward○ Medial rectus turns eye inward○ Superior oblique rotates eye counterclockwise○ Inferior oblique rotates eye clockwise○ Three cranial nerves control these muscles
Fig 9.6
Sense of Vision Anatomy and Physiology of the Eye
Three layers○ Sclera
White and fibrousCornea is transparent
○ ChoroidMiddle, vascularized layerBecomes the iris towards the front
Regulates the size of the pupil Colored portion of eye
The ciliary body is behind the iris Contains the ciliary muscle Controls the shape of the lens
Sense of Vision
○ Lens – divides the eye into two compartmentsAnterior compartment contains aqueous humorPosterior compartment contains the retina and the vitreous
humor
○ RetinaContains photoreceptors
- Rod cells – night vision and peripheral vision- Cone cells – distinguish colors
Fovea centralis – area of retina where cone cells are densely packed
Optic nerve – formed from sensory fibers from the retina
Sense of Vision
Function of the lens○ Focuses images on the retina○ Image produced is smaller than the object○ Image on retina is inverted and reversed○ Accommodation
Maintaining focus on a distant and then near objectLens must change shape
- Controlled by the ciliary muscle- Ciliary muscle is relaxed for a distant object- Ciliary muscle contracts to view a near object
Sense of VisionVision pathway
Light is refracted by cornea, aqueous humor, lens, vitreous humor
Image is formed on the retinaNerve impulses travel to the visual area of the cerebral
cortex
○ Color visionDepends on three kinds of conesColor blindness is caused by the inherited absence of the
color pigments in the cones
Sense of Vision○ Function of the retina
Rod cells and cone cells are located in the deepest layer
Light must penetrate to the back of the retina
○ Blind spotNo rods and cones where the optic nerve leaves the retinaNo vision is possible in this area
Sense of Vision
○ From the retina to the visual cortexThe right and left visual cortex rebuilds and rights image
Sense of Hearing
Two sensory functions of the ear Sensory receptors located in the inner ear
Consists of hair cellsSensitive to mechanical stimulation
(mechanoreceptors)
Anatomy of the Ear Sound Pathway
Sense of Hearing Anatomy of the Ear
Outer ear○ Pinna○ Auditory canal
Lined with hair Modified sweat glands secret cerumen
Middle ear○ Begins at the tympanic membrane○ Ends at bony wall with two small openings
Oval window Round window
○ Three small bones (ossicles) Malleus Incus Stapes
○ Auditory tube (eustachian tube) extends from the middle ear to the nasopharynx
Inner ear○ Filled with fluid○ Three areas
Semicircular canals Vestibule Cochlea
Sense of HearingSound pathway
○ Through the auditory canal and middle earSound travels by the vibrations of air moleculesSound waves strike the tympanic membrane causing it to
vibratePressure from the tympanic membrane causes the malleus,
the incus, and then the stapes, to vibrateThe stapes strikes the oval windowVibrations from the oval window are passed to the fluid
within the cochlea of the inner ear
Sense of Hearing○ Impulses travel From the cochlea to the auditory
cortexThe spiral organ (organ of Corti) is the sense
organ for hearing- Located in cochlear canal
Pressure waves cause the hair cells to bendNerve impulses begin in the cochlear nerve and
travel to the brain stem and then the auditory cortex
Sense of Equilibrium Mechanoreceptors in the semicircular canals
are responsible for rotational equilibrium Mechanoreceptors in the vestibule are
responsible for gravitational equilibrium
Sense of Equilibrium Rotational Equilibrium Pathway
Involves the three semicircular canals Motion sickness
○ Continuous movement of fluid within the semicircular canals○ Sensory input from the inner ear that is different from visual
sensations Vertigo is dizziness and a sensation of rotation
Effects of Aging The lens of the eye does not accommodate as
well Three visual disorders seen frequently:
CataractsAge-related macular degenerationGlaucoma
The need for a hearing aid increases with agePresbycusis (age-related hearing decline)Otosclerosis is the most frequent cause of conduction
deafness in adults Dizziness and the inability to maintain balance