Ch 10 The Senses Distinguish between somatic senses

Ch 10 The Senses

Distinguish between somatic senses and special senses. � Somatic body ◦ ◦ Pain Touch Pressure Temperature � Special ◦ ◦ ◦ – general senses; located all over the – associated with one area of the body Hearing Sight Taste Equilibrium Smelling

Describe five kinds of receptors. � Chemoreceptors �Δ chemicals � Pain receptors � Tissue damage � Thermoreceptors � Δ temperature � Mechanoreceptors � Δ pressure/position � Photoreceptors � Δ light

Explain how sensation arises. � Sensation – Sensory receptors reach threshold and brain becomes aware of a sensory event � Perception – How your brain interprets that sensation � Projection – Cerebral cortex causes the feeling to seem to come from the affected area

Explain how sensation arises. � Adaptation – Ability of the nervous system to become less responsive to maintained stimulus. ◦ Do you feel your clothing on your body? ◦ Do you notice any sounds in the room?

Describe the receptors associated with the senses of touch, pressure, temperature, and pain. � Pg 264 � Free nerve endings � Tactile (Meissner’s) corpuscles � Lamellated (Pacinian) corpuscles

Temperature Senses � Free cold. nerves that respond to either warm or ◦ Warm: >25°C (77°F) respond heavily >45°C (113°F) shut down Near 45°C = pain (burning) ◦ Cold: 10°C-20°C (50°F-68°F) respond heavily <10°C (50°F) = pain (freezing) ◦ Adapt within about 1 minute of stimulation.

Describe how the sense of pain is produced. � Free nerve endings – stimulated by tissue damage. � Mechanoreceptors and chemoreceptors can also stimulate pain. � They’re the only type of receptors in viscera that can ilicit a sensation. � Adapt poorly.

Describe how the sense of pain is produced. � Nerve fibers: ◦ Acute pain fibers �Myelinated �Sharp pain �Quits when stimulation stops ◦ Chronic pain fibers �Unmyelinated �Dull, aching sensation �May continue after stimulation stops

Describe how the sense of pain is produced. � Awareness occurs when impulses reach the thalamus. � Cerebral cortex determines intensity, location, emotions, motor response.

Referred Pain � Can feel like it’s coming from a different part of the body. � Nerve pathways are similar.

Identify the location of the receptors associated with special senses. � Smell – � Taste – � Hearing – � Equilibrium – � Sight -

Explain the relationship between the senses of smell and taste. � Both chemoreceptors. � Both must be dissolved in fluid. � Usually associated with one another because we do them at the same time.

Explain the mechanism for smell. � Receptors each respond to different smells, then stimulate an interpretation in the olfactory bulb of the brain.

Explain the mechanism for smell. � The sensation travels to the brain along the olfactory tract to the limbic system of the diencephalon.

Explain the mechanism for taste. � Taste buds are located within papillae. � Modified epithelial cells act as receptors.

Explain the mechanism for taste. � Taste hairs portrude from openings called taste pores. � Particles must be dissolved in fluid before they can be tasted.

Explain the mechanism for taste. � Five ◦ ◦ ◦ receptors Bitter Sweet Salty Sour Umami � Nerve impulses travel to the medulla oblongata and parietal lobe of the cerebrum.

Explain the function of each part of the ear. 1. 6. 5. 8. 4. 7. 3. 2.

Cochlea to hair cells � Perilymph � Membrane � Endolymph � Hair cells

Explain the mechanism for hearing. � Hair cells bend causing a nerve impulse. � Nerve impulses travel along the auditory nerve to the auditory cortices of the temporal lobes.

Equilibrium – two types � Static – when you’re still ◦ Detected by shifting calcium carbonate grains in the vestibule of the inner ear. ◦ Sends messages to the brain, which sends messages back to muscles. � Dynamic – when you’re moving ◦ Detected by fluid within the semicircular canals of the inner ear. ◦ Messages are sent to the cerebellum for processing and response. � Mechanoreceptors equilibrium. and sight can aid in

Explain the function of each part of the eye.

Distance vs Close Vision � Accommodation – adjustment of the lens shape to focus vision ◦ Done by the ciliary muscles and suspensory ligaments. � Distance – lens is more flattened; ciliary muscles relaxed � Close – lens is more convex; ciliary muscles contracted

Photoreceptors � Rods vs. Cones � Rods – black and white/night vision ◦ Less precise images; focus on outlines of objects. ◦ One type ◦ A lot more rods (125 million) � Cones – color/daytime vision ◦ More precise images. ◦ Three types: red, green, blue ◦ Fewer (7 million)

Describe the visual nerve pathway. � Photoreceptors (rods and cones) detect light. � They are projected backward and upsidedown onto the retina, then sent to the visual cortex. � The visual cortex interprets the images so they are perceived correctly.