Presentation on theme: "Sensory Receptors; specialized cells that monitor internal and external conditions. Receptors CNS for interpretation Adaptation is a decreased sensitivity."— Presentation transcript:
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)
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
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.
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!!!)
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)
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
Examples of pressure receptors
Proprioceptors Monitors the position of joints, tension in tendons and ligaments State of muscle contraction Lab Activity
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
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.
10-20 million receptor cells are packed into a 5 cm 2 area.
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
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.
Four Primary Tastes Sweet – tip of tongue Salt – lateral tip Sour – sides of tongue Bitter – back of tongue
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!
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
Contains –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
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
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!!
What number do you see? Red/Green Colorblind?
Optic disc – where the axons from neurons converge, forms optic nerve No photoreceptors are found here.
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.
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.)
Close Images – longer focal distance; lens is rounded because ciliary muscles contract. The closer the source, the longer the focal distance
Distant Objects –Shorter focal distance and flattened lens.
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.
Normal Vision; what is happening in the eye.
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.
Corrected by wearing a diverging lens!
Far Sighted (Hyperopia) Eyeball is too shallow Person can see distant objects; not near objects
Corrected by wearing converging lens!
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.
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.
3 Sections of EAR
Organs –Pinna (auricle) –External Auditory Canal –Functions to collect, direct sound waves to ear drum.
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
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.
How Do you Hear?
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.
Tiny Hair cells are in the cochlea in an area called the Organ of Corti.
Larger view of Organ of Corti.
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.
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.