QOD – What are the two main divisions of the nervous system?

1. QOD – What are the two main divisions of the nervous system?

2. Somatic Nervous System & Special Senses Chapter 12

3. Special Senses • Touch • Taste • Vision • Hearing • Smell

4. General Senses • Somatic senses • Include tactile sensations • Touch, pressure, and vibration • Include thermal sensations • Warmth or cold • Include pain sensations • Include proprioceptive sensations • Joint and muscle position sense and movement of limbs and head • Visceral senses • Information about the conditions within body fluids and internal organs

5. Sensation • Is a conscious or subconscious awareness of external and internal conditions of the body • Stimulus • Change in the environment, capable of activating sensory neurons • Sensory Receptors • Convert the stimulus into electrical signals • Nerve impulse • Conducted along neurons in the neural pathway to the CNS • Integrate • CNS receives impulses and initiates a response

6. Classification of Sensory Receptors

7. Classification of Sensory Receptors

8. Somatic Senses • Stimulations of sensory receptors in the skin, mucous membranes, muscles, tendons, and joints • Not evenly distributed throughout the body • Areas with high number of nerve endings are: • Lips, tip of tongue, and fingertips

9. Tactile Sensations • Sensations associated with • Touch • Pressure • Vibration • Itch • Tickle

10. Touch • Result of stimulation of tactile receptors in the subcutaneous layer • Types: • Corpuscles of Touch (Meissner corpuscles) (adapt rapidly) • Located on the dermal papillae of hairless skin • Abundant in hands, eyelids, tip of tongue lips, nipples, sole, clitoris and tip of penis • Hair Root plexuses – attached to hair follicle and detect movement of hair shaft • Free nerve ending • Cutaneous mechanoreceptors (slowly adapting touch receptors) • Type I cutaneous mechanoreceptors (Merkel disks) • Type II cutaneous mechanoreceptors (Ruffini Corpuscles) • Sensitive to stretch

11. Pressure and Vibration • Pressure – is an sensation that is felt over a larger area than touch • Types of receptors • Type I cutaneous mechanoreceptor • Pacinian Corpuscle • Adapt rapidly • Vibration – rapidly repetitive sensory signal from tactile receptors • Types of receptors • Corpuscles of touch – detect lower frequencies • Pacinian corpuscles – detect high frequencies

12. Itch and Tickle • Itch – results from a stimulation of free nerve endings by certain chemicals • Often a local inflammatory response • Tickle – results from a stimulation of free nerve endings and pacinian corpuscles • Usually only arises when someone else is touching you

13. Thermal Sensations • Detect coldness and warmth • Free nerve endings • Cold receptors – located in the epidermis • Warm receptors – located in the dermis

14. Pain Sensation • Nociecptors – sensory receptors for pain • Free nerve endings • Found in every tissue everywhere except the brain • That is why they can do surgery on your brain while you are awake

15. Pain • Fast Pain • Occurs very rapidly • .1 second after stimuli • Localized • Not found in deep tissue • Slow pain • Occurs rapid • 1 second or more after stimuli • Gradually increases in intensity over time • In skin and deep tissue

16. Proprioceptive sensations • Sensations that inform you to the • degree your muscles are contracting, • tension on tendons, • position of joints, • And orientation of head • Proprioreceptors – are the receptors for proprioceptive sensation