Anatomy and Physiology 2 - Senses PDF

ANATOMY AND PHYSIOLOGY 2 ‫االحساس‬ CHAPTER 9, PAGE 214 DR MOHAMMED BASSBOUS PALESTINE AHLIYA UNIVERSITY © 2012 Pearson Education, Inc.  The senses Our se...

ANATOMY AND PHYSIOLOGY 2 ‫االحساس‬ CHAPTER 9, PAGE 214 DR MOHAMMED BASSBOUS PALESTINE AHLIYA UNIVERSITY © 2012 Pearson Education, Inc.  The senses Our senses constantly provide us with information about the surrounding environment : We see, hear, and touch. The senses of taste and smell enable us to enjoy the flavor of our food or warn us that food has expired and may be dangerous to eat. We also get information from our senses about what is happening inside the body (hunger , thirsty). © 2012 Pearson Education, Inc.  SENSORY PATHWAY It is the way and structures that are involved in the process of sensation, from the first moment when the stimulus appearing, until the feeling formation in the brain. Sensory pathway has the following parts: 1-Receptors— it is a nerve ends of sensory neuron ,that detect changes (stimuli) and generate impulses. Receptors are usually very specific with respect to the kinds of changes they respond to. Their function is to send a signal to the sensory neuron in the CNS. © 2012 Pearson Education, Inc.  SENSORY PATHWAY 2. Sensory neurons—they are located in the CNS,or ganglia ,they receive sensory information from their end (receptors) and send them directly to the brain (cranial nerves) ,or through the spinal cord.. 3- Sensory tracts—represents nerve fibers ,that transmute the impulses to a specific part of the brain. 4. Sensory areas— the part of the brain ,that will interrupt the information. most are in the cerebral cortex.. © 2012 Pearson Education, Inc. © 2012 Pearson Education, Inc.  CUTANEOUS SENSES The dermis of the skin and the subcutaneous tissue contain receptors for the sensations of touch, pressure,heat, cold, and pain. The cutaneous senses provide us with information about the external environment and also about the skin itself. Much of the information about the environment is not of great importance and is processed at a subconscious level (suppressed by the thalamus). © 2012 Pearson Education, Inc.  Referred pain Sometimes pain that originates in an internal organ may be felt in a cutaneous area; This is called referred pain. The pain of a heart attack (myocardial infarction) may be felt in the left arm and shoulder, or the pain of gallstones may be felt in the right shoulder , the pain of the hip may be felt in the knee. © 2012 Pearson Education, Inc.  Referred pain This referred pain is actually a creation of the brain. Within the spinal cord are sensory tracts That transmit both cutaneous and visceral impulses by the same way.. Cutaneous impulses are much more frequent. When the impulses come from an organ such as the heart, however, the brain may still project the sensation to the “usual” cutaneous area. © 2012 Pearson Education, Inc.  The referred pain © 2012 Pearson Education, Inc.  SENSE OF TASTE The receptors for taste are found in on the tongue, There are five (perhaps more) general types of taste receptors: sweet, sour, salty, bitter, and savory. The impulses from taste buds are transmitted by the facial and glossopharyngeal (7th and 9th cranial) nerves to the taste areas in the brain cortex. © 2012 Pearson Education, Inc. © 2012 Pearson Education, Inc.  SENSE OF SMELL The receptors for smell (olfaction) are chemoreceptors that detect vaporized chemicals that have been sniffed into the upper nasal cavities humans have several hundred different receptors. olfactory receptors generate impulses carried by the olfactory nerves (1st cranial) to temporal lobes in the brain. It has been estimated that the human brain is capable of distinguishing among 10,000 different scents. © 2012 Pearson Education, Inc.  HUNGER AND THIRST The receptors for both senses are specialized cells in the hypothalamus. Receptors for hunger are believed to detect changes in blood nutrient levels, changes in the hormones and enzymes level secreted by stomach and small intestine, and levels of the hormone released by adipose tissue. The receptors for thirst detect changes in the body water content, which is actually the water-to salt proportion. © 2012 Pearson Education, Inc.  Naturally we do not feel these sensations in the hypothalamus: They are projected. Hunger is projected to the stomach, which contracts. Thirst is projected to the mouth and pharynx, and less saliva is produced. © 2012 Pearson Education, Inc.  The vision and The Eye Eye considers the organ of vision The eyes contain receptors for light in the retina and a refracting system of lenses that focus the light rays on these receptors. Two groups of structure working together in the eye: 1-The Eye ball 2-The Accessory structures. (eyelids ,lacrimal apparatus ,eye muscles) © 2012 Pearson Education, Inc.  The EYELIDS The eyelids contain skeletal muscle that enables the eyelids to close and cover the front of the eyeball , they are lined with a thin membrane called the conjunctiva. THE LACRIMAL APPARATUS Tears are produced by the lacrimal glands, located at the upper, outer corner of the eyeball. Tears are mostly water, with about 1% NACL, also contain lysozyme, an enzyme that inhibits the growth of most bacteria on the surface of the eye.. © 2012 Pearson Education, Inc.  Eye muscles The eye sits in a protective bony socket called the orbit. Six extraocular muscles in the orbit are attached to the eye. These muscles move the eye up and down, side to side, and rotate the eye. The extraocular muscles are attached to the white part of the eye called the sclera. This is a strong layer of tissue that covers the surface of the eyeball. These muscle innervated by cranial nerves © 2012 Pearson Education, Inc. © 2012 Pearson Education, Inc.  The Eye structure The eye consists of three layers : 1- the outer layer ( sclera and cornea) 2-middle layer (iris and the pupil , lenses ) 3-inner layer (retina) © 2012 Pearson Education, Inc.  Sclera and cornea Sclera is a tough and smooth sheet of connective tissue the covers nearly covers the eye ball ,except the anterior portion, sclera plays a protective function, and it also a site for extra-ocular muscles attachment. Cornea is the central part on the eye surface , that is colorless and is transparent for light, through cornea light x-rays enter toward the retina. © 2012 Pearson Education, Inc.  Choroid and iris, pupil Behind the cornea is a fluid filled cavity called the anterior chamber. Behind the anterior chamber is The iris which the colored part of the eye.iris controls the amount of light that will enter the eye by dilating or constricting the pupil which Is an opening through the iris (the black hole in the colored part of the eye. Behind the iris is the posterior chamber. © 2012 Pearson Education, Inc.  Behind the posterior chamber are the lenses. Behind the lens The vitreous cavity , which filled by A jellylike substance ,and located between the retina and the lenses. The Retina— the light-sensitive tissue, lining the back of the eye, there the receptor of the light are located. When light reach the retina, receptors generate an electrical impulse that is transmitted by the optical nerve to the proper area in the brain. © 2012 Pearson Education, Inc. © 2012 Pearson Education, Inc.  THE EAR The ear consists of three areas : the outer ear, the middle ear, and the inner ear. The ear contains the receptors for two senses: hearing and equilibrium , These receptors are all in the inner ear. © 2012 Pearson Education, Inc.  OUTER EAR The outer ear consists of the auricle and the ear canal. Auricle is the visible part of the ear, its function is to capture waves and amplifying them , the direct them toward the ear canal Ear canal also plays a role in waves amplifying , it also produces the ear wax , and direct waves toward the middle ear. © 2012 Pearson Education, Inc. © 2012 Pearson Education, Inc.  The middle ear Middle ear separated from the outer ear by the tympanic membrane( eardrum ) that lies in the end of the ear canal. the middle ear has three bone: 1-Incus 2-Malleus 3- Stapes The air pressure in the middle ear must be the same as the external atmospheric pressure in order for the eardrum to vibrate properly. The middle ear is connected to the nasopharynx by The Eustachian tube that permits air to enter or leave the middle ear cavity. © 2012 Pearson Education, Inc.  INNER EAR It is a cavity that contains two apparatus : 1- the cochlea: hearing apparatus 2-semicircular canals: balance apparatus © 2012 Pearson Education, Inc.  The cochlea a snail-shaped structure filled with fluid, in the inner ear. An elastic membrane ,called the basilar membrane, runs from the beginning to the end of the cochlea, splitting it into an upper and lower part. the basilar membrane ,serves as the base, on which hearing structures sit (Hair cells— sensory cells ) © 2012 Pearson Education, Inc.  MECHANISM OF HEARING 1- Sound waves enter the ear canal, which leads to the eardrum. 2-The eardrum vibrates and sends these vibrations to three bones in the middle ear. 3-The bones in the middle ear amplify, or increase, the sound vibrations and send them to the cochlea © 2012 Pearson Education, Inc.  Mechanism of hearing. Cont.. 4-vibrations from the middle ear causes the fluid wave inside the cochlea. Hair cells that cover the basilar membrane will move up and down. 5- moving of hair cells will generate electrical reaction that will be transmitted by auditory (cochlear nerve) nerve to the brain. The End © 2012 Pearson Education, Inc.