Presentation is loading. Please wait.

Presentation is loading. Please wait.

Ch 9 The Senses.

Similar presentations

Presentation on theme: "Ch 9 The Senses."— Presentation transcript:

1 Ch 9 The Senses

2 Sensory Receptors; specialized cells that monitor internal and external conditions.
Receptors CNS for interpretation Adaptation is a decreased sensitivity to the presence of a constant stimulus. I.e. not feeling your watch; jumping into cold lake (Work of RAS)

3 Your Senses can be divided into two categories
General Senses – receptors for temperature, pain, touch, pressure, vibration and body position Scattered throughout the body Special Senses – smell, taste, vision, balance and hearing Concentrated with specific structures, called sense organs

4 General Senses Part of PNS Pain Receptors (Nociceptors)
Common in the superficial portions of the skin, joint capsules, along periosteum of bones, Fast pain: carried by myelinated fibers Slow pain: carried by unmyelinated fibers Referred Pain: perception coming from other parts of body; parts of body are connected to by same spinal nerves. I.e. cardiac pain – originates in chest and left arm.

5 Temperature (thermoreceptors)
Nerve endings scattered beneath skin surface Located in skeletal muscles, liver and hypothalamus as well. Why? Receptors RAS system (Working right now in this room!!!)

6 Touch, Pressure and Position (Mechanoreceptors)
Respond to stretching, compression, twisting or other distortions of the cell membrane. 3 classes of Mechanoreceptors Tactile (touch) Baroreceptors (pressure) Proprioceptors (position) Contain mechanically regulated ion channels that open or close in response to stretching, compression, twisting or other distortions of the cell membrane

7 6 Types of Touch Receptors
Free Nerve endings Hair Plexus Merkel’s Meissner’s Pacinian Ruffini’s

8 Baroreceptors: monitor changes in pressure
Surround the walls of hollow organs. I.e. blood vessels, lungs, stomach, bladder Monitors BP – plays a role in regulating cardiac function and blood flow to tissues Baroreceptors in lungs determine degree of lung expansion, which is relayed to pons and medulla Controls urination and defecation in urinary and digestive systems

9 Examples of pressure receptors

10 Proprioceptors Monitors the position of joints,
tension in tendons and ligaments State of muscle contraction Lab Activity Most information processed subconsciously

11 Smell and Taste Chemoreceptors respond to chemical in a water solution. Olfactory organs – provide a sense of smell Consists of olfactory epithelium, receptors, supporting cells and basal (stem) cells Olfactory glands produce a mucus that covers epithelium Keeps area moist and free of dust/debris Solvent that captures and dissolves air borne molecules Constantly replaced; flushes away old odors Nose diffuses chemicals thru mucus; mouth chemicals dissolve in saliva Tissue is pseudostratified epithelium

12 Olfactory Receptors: modified neurons
An odor causes olfactory receptors to open Na+ channels and change membrane permeability. Research in the 1990’s suggests we have 1000 smell genes Genes only active in nose Each gene codes for an odor binding protein; these receptor proteins only allow certain odors to bind to it. Receptor cells replace themselves q 60 days. Function of basal or stem cells 10-20 million receptors are packed into a 5 cm2 area; animals have much larger numbers

13 Olfactory Receptors 10-20 million receptor cells are packed into a 5 cm2 area.

14 Olfactory Bulb: Cranial Nerve I
Axons leaving bulb travel to the olfactory cortex of cerebrum, hypothalamus and part of limbic system. Elicits emotional responses to odors Smells associated with danger (smoke, skunk) Pleasant smells cause increased secretion of saliva and gastric juice Unpleasant smells trigger protective reflexes (sneezing/coughing) Lab Activity Some of what we smell is really pain. Nasal cavities contain receptors that respond to irritants such as ammonia, hot of peppers, chill of menthol. Reach the CNS via the trigeminal nerve, not the olfactory bulb

15 Taste Tongue contains 3 types of cells: receptor, support and basal cells Taste buds are the gustatory receptors distributed all over tongue. Basal cells replace receptors q 7-10 days Taste hairs extend from receptor cells and are bathed in saliva Dissolved chemicals touch hair (microvilli), causing Na+ channels to open → A.P.

16 Four Primary Tastes Sweet – tip of tongue Salt – lateral tip
Sour – sides of tongue Bitter – back of tongue

17 Taste Receptors respond more to unpleasant stimuli
Taste buds are monitored by cranial nerve 7 (facial), 9 (glossopharyngeal), 10 (vagus). Taste is 80 % smell. Think of how food tastes when you have a cold. Try This! Cranial nerves send impulses to thalamus and then primary sensory cortex. Olfactory receptors play huge role in taste perception 1000 X more sensitive to tastes when organs are functioning (Think cold)

18 Vision: Eye Anatomy Eyes are hollow organs divided into two cavities.
Aqueous humor – liquid inside eyeball gives the eye shape Wall of the eye contains 3 layers Fibrous tunic – outer layer Vascular tunic – middle layer Neural tunic – inner layer

19 Fibrous Tunic Contains Functions Sclera – white of eye
6 eye muscles attach Posterior surface contains blood vessels and nerves Cornea – transparent light passes thru. Functions Mechanical support and some protection Attachment site for 6 extrinsic eye muscles Assists in focusing Fibrous Tunic Sclera is a layer of dense fibrous tissue that contains collagen and elastic fibers Blood vessels lie under the sclera; but are very small so you only see white fibers. Thus white eyeball Collagen fibers in cornea are arranged to allow light to pass through; gets oxygen by diffusing from air.

20 Vascular Tunic Functions Provide route for blood and lymph tissue
Iris – contains blood vessels, pigment cells, smooth muscle Controls the size of pupil (center of iris) in response to light Ciliary body – Thickened ring of tissue surrounding lens; forms aqueous humor and muscles maintain lens shape Glaucoma – increased pressure in eye due to imbalance of A. humor Choroid – blood vessel-rich membrane; delivers oxygen and nutrients to retina Functions Provide route for blood and lymph tissue Transmits and Regulates amount of light entering eye Circulate aqueous humor within eye Control shape of lens Smooth muscle represents all intrinsic eye muscles; 2 layers of smooth muscle Explain dilation and constriction of pupil; controlled by autonomic nervous system Muscles are responding to changes in light intensity

21 Iris Ciliary Body Vascular Tunic Choroid

22 Tunic Neural Tunic: Retina Contains Photoreceptors – respond to light
Rods – light sensitive Cones – color vision 3 types of cones Red/Green/Blue provides perception of color Give more clarity than rods Fovea – largest concentration of cones; sharpest vision Volunteers??? Anyone, Anyone!! Neural Tunic: Retina Tunic Rods allow us to see in dim light; night driving. Located along sides of eye Cones are red, green, blue; each type is sensitive to different range of wavelengths

23 Eye Anatomy

24 Color Blindness Ishihara Test
Caused by absence of certain cones. Most common, absence of red cones. Person can’t distinguish between red and green colors


26 What number do you see? Red/Green Colorblind?
Person with normal vision should see a five, Person with Red/Green should see a 2.

27 Optic disc – where the axons from neurons converge, forms optic nerve
No photoreceptors are found here. Blind Spot


29 Try this

30 How Do You See? Lens Primary function is to focus image on the retinal receptors in the back of eye. Focusing requires two steps Light is bent when it passes between mediums of varying densities Greatest refraction occurs when light passes thru cornea. Focal point – when light bends to form a point Focal Distance – distance between center of lens and focal point. Focusing is accomplished by changing the shape of the eyeball. Light bends 3 times cornea (most diffraction), entering and leaving lens. Doesn’t refract going thru V. humor

31 Pathway to the brain eye Occipital Lobe Optic Nerve II
Superior Colliculi Pathway to the brain Occipital Lobe

32 Depth Perception Two eyes are better than one, especially when it comes to depth perception. Depth perception is the ability to judge objects that are near or farther than others. To demonstrate the difference of using one vs. two eyes to judge depth, hold the ends of two pencils, one in each hand. Hold them either vertically or horizontally facing each other at arms-length from your body. With one eye closed, try to touch the end of the pencils together. Now try with two eyes, it should be much easier. (Can use fingers if you don’t have 2 pencils.)

33 What happens to the lens at close distances?
Close Images – longer focal distance; lens is rounded because ciliary muscles contract. The closer the source, the longer the focal distance

34 Distant Objects –Shorter focal distance and flattened lens.

35 Keeping Focused The lens constantly changes shape to keep the focal distance constant. – Image stays focused on retina. I.e. looking at the board and then your paper. 20/20 vision means a person can see details at a distance of 20 feet as clearly as the “normal population” would.

36 Normal Vision; what is happening in the eye.

37 Near sighted (myopia) 20/30 vision Images forms in front of retina
Vision at close range will be normal, because lens can adjust and round up to focus. Eyeball is too deep Objects in the distance will be blurry and out of focus 20/30 vision

38 Corrected by wearing a diverging lens!
Diverging lens increase focal distance

39 Far Sighted (Hyperopia) Eyeball is too shallow
Person can see distant objects; not near objects At close range the lens cannot provide enough refraction; point doesn’t focus at end of retina.

40 Corrected by wearing converging lens!
Converging lens – bends rays more.

41 Astigmatism occurs when the cornea is more oval than spherical
Astigmatism occurs when the cornea is more oval than spherical. The result is an unequal bending of the light which results in multiple focal points.                                                   

42 Test for Astigmatism To test your vision, stand about 20 feet from the chart. Test one eye at a time. If you see lines grey and other black you have an astigmatism.

43 Ear Anatomy Ear is composed of 3 anatomical regions
External Ear: Pinna – Tympanic membrane Middle Ear: Tympanum – Auditory ossicles Inner ear: Bony Labryinth

44 3 Sections of EAR

45 External Ear Organs Pinna (auricle) External Auditory Canal
Functions to collect, direct sound waves to ear drum. External Ear Hairs prevent foreign object and insects from entering canal Cerumen (ear wax) slows growth of microbes and reduces chance of infection. Ends at Tympanum

46 Middle Ear Tympanum – ear drum; Auditory Tube (Eustachian tube)
Cavity is filled with air Auditory Tube – equalizes pressure on either side of eardrum Tympanum – ear drum; Auditory Tube (Eustachian tube) Auditory Ossicles – 1. Malleus (hammer) 2. Incus (anvil) 3. Stapes (stirrup)

47 Inner Ear Vestibule – provides sensations of gravity and acceleration
Semicircular Canals – detect movement of head Cochlea – provide sense of hearing Hair Cells – receptors of inner ear for sound

48 Bony Labyrinth

49 How do we hear? Sound waves cause the tympanic membrane to vibrate which moves the ossicles. Sound energy are converted to mechanical energy. Ossicles transmit the in/out vibrations from tympanic membrane to ear’s inner fluid-filled chamber.

50 How Do you Hear?

51 What about Hearing? Sounds set up vibrations in air that beat against the tympanic membrane. Vibrations push the ossicles that press fluid in the inner ear against membranes. Fluid causes forces that pull on tiny hair cells and stimulate neurons. Neurons send impulses to the brain, which interprets them. Tympanic membrane = eardrum Ossicles = 3 tiny bones


53 Tiny Hair cells are in the cochlea in an area called the Organ of Corti.
Organ of Corti – Hair cells that cause depolarization of nerve cells when they are moved by sound waves.

54 Larger view of Organ of Corti.

55 Maintaining Equilibrium: How does it work?
When the head is upright, otoliths pushes the sensory hairs downward rather than side to side. By tilting the head, the otoliths move causing the sensory hairs to be distorted. This is sent to the CNS for interpretation. Within the vestibule and semicircular canals, tiny hairs are found along the membrane of these structures. Inside the canals, jellylike substance contains tiny calcium carbonate crystals called ear stones or otoliths. (o’to-lith)

56 Equilibrium Ear responds to various head movements. Static Equilibrium is controlled by the vestibule. Respond to straight-line changes in speed and direction, but not rotation. Dynamic Equilibrium is controlled by the semicircular canals. Respond to changes in head position; rotating the head to say no.

Download ppt "Ch 9 The Senses."

Similar presentations

Ads by Google