1. Approx how much does skin weigh? (in %) How many layers does your skin have? Where on your body is the thinnest skin found? Where on your body is the thickest skin found? Your skin renews itself entirely in how many days? How many skin cells do you lose every day? How much of the dust in your home is actually made up of skin cells? (in %) At what age do children develop their permanent skin colour? How many bacteria live on your skin? Who suffers from acne more, men or women? 15% 3 Eyelids Feet 28 days About 50 million 50% At 6 months 1 trillion Women – figures ;) The Skin You’re In

2. Skin Senses Pressure, Temperature & Pain

3. The Skin Senses Skin is the largest sense organ Makes up about 15% of your body weight Avg of about 20 feet of skin on adults You shed about 50 million skin cells every day That’s 30,000-40,000 per minute Other senses are found in specific areas of the body (eye, ear, etc) your sense of touch can be found all over your body Your skin is filled with nerve endings that send info to your spinal cord Remember Me?

4. Medulla From your spinal cord, the signal crosses in the medulla Part of the brain stem Functions are involuntary Regulates blood pressure and breathing Transfers information from spinal cord into brain

5. Thalamus Information transfers from the medulla to the thalamus The thalamus is found in each hemisphere (plural = thalami) Almost ALL sensory info goes to the thalamus FIRST before going to the rest of the brain Exception is smell Majority of ALL signals going to the brain pass through this It also receives info from the cortex, modulates it and sends it back

6. Somatosensory Cortex Thalami send info to the somatosensory cortex This is the area that processes ALL sensory info related to touch, pain, temperature Part of the parietal lobes

7. Somatosensory Cortex Each neuron takes its information to a specific place in the somatosensory cortex. Next, that part of the somatosensory cortex gets to work on figuring out what the information means. Think of it like scientists sending data to a data analyst. Each scientist, like the neuron, gathers information and sends it to a master analyzer or the somatosensory cortex.

8. Touch Four basic skin senses are Pain Temperature – warm Temperature - cold Pressure All skin sensations are a combination of these four basic senses These parts can combine to create different touch sensations. For example, burning is pain, warmth, and cold. Itching is gentle stimulation of pain receptors

9. Temperature Temperature is sensed by thermoreceptors under the skin We have warm/hot and cold receptors Warm/hot – are not stimulated above about 45 degrees celsius Then the pain receptors take over to avoid skin damage Cold – are not stimulated under about 5 degrees celsius (this is why you can start to feel numb) Way more cold receptors than warm/hot Most are in the face/ears

10. Pressure Only pressure has identifiable neural receptors (mechanoreceptors) located beneath the skin They convert pressure stimulation into neural messages to send to the brain. Constant pressure causes sensory adaptation and it either reduces the number of signals or quits sending them all together. (like the clothes on your body) - Sensory receptors are located unevenly on the body so certain areas are more sensitive than others.

11. TOUCH The amount of somatosensory cortex dedicated in the brain depends on the sensitivity of that area. This has been mapped as the somatosensory map or homunculus. Time for an EXPERIMENT!

12. SOMATOSENS ORY CORTEX