2. Sensation- conscious (perception) or subconscious awareness of changes in environment

3. Sensory modality- unique type of sensation general senses- somatic (tactile, thermal, pain, proprioceptive) and visceral (internal organs) special senses- smell, taste, vision, hearing, equilibrium

4. Process of sensation begins with receptor (selective)- stimulus produces potential at threshold CNS integrates impulse Three types of receptors: free nerve endings, encapsulated nerve endings, separate cells- see figure 16.1

5. Can be grouped on location exteroceptor s (external surface of body), interoceptor s (internal environment ), propriocepto rs (muscles, tendons, joints)

6. Can be grouped by stimulus mechanoreceptors (mechanical stimuli) thermoreceptors (heat) nociceptors (pain) photoreceptors (light) chemoreceptors (chemicals) osmoreceptors (osmotic pressure)

7. Adaptation to maintained, constant stimulus (can be rapid or slow) A dog (red line) tracks a pheasant (yellow line). As the dog keeps leaving the odour to prevent receptor adaptation, it zigzags.

8. Somatic sensations Tactile: touch, tickle, pressure, vibration, itch (mechanoreceptors) touch: Meissner corpuscles and hair root plexuses are rapidly adapting, Merkel discs and Ruffini corpuscles are slowly adapting pressure and vibration: Meissner corpuscles, Merkel discs, and lamellated corpuscles itch and tickle: stimulation of free nerve endings Thermal: free nerve endings, cold in epidermis, warmth in dermis Pain: free nerve endings everywhere except the brain- very little adaptation two types: fast ( sharp or prickling) and slow (aching or throbbing) Proprioceptive: know where body parts are and control equilibrium

9. Somatic Sensory Pathways- from somatic receptors to cerebral cortex (somatosensory area) First-order neuron- from somatic receptor to brain stem (cranial) or spinal cord (spinal nerves) First-order neuron- from somatic receptor to brain stem (cranial) or spinal cord (spinal nerves) Second-order neuron- from brain stem or spinal cord to thalamus- decussate (cross over to other side) Second-order neuron- from brain stem or spinal cord to thalamus- decussate (cross over to other side) Third-order neuron- from thalamus to primary somatosensory area Third-order neuron- from thalamus to primary somatosensory area

11. Three pathways to cerebrum and cerebellum- table 16.3 posterior column-medial lemmniscus: fine touch, stereognosis (recognize by feel), proprioception, vibration posterior column-medial lemmniscus: fine touch, stereognosis (recognize by feel), proprioception, vibration anterolateral: crude touch impulses, pain, temperature anterolateral: crude touch impulses, pain, temperature spinocerebellar tracts: proprioceptive to cerebellum spinocerebellar tracts: proprioceptive to cerebellum

14. can map somatosens ory areas (lips and hands large area, trunk and limbs small area)

15. Somatic Motor pathways- provide imput to lower motor neurons Local circuit neurons- coordinate rhythmic activity Local circuit neurons- coordinate rhythmic activity Upper motor neurons- planning, initiating, and directing sequences of voluntary movements Upper motor neurons- planning, initiating, and directing sequences of voluntary movements Basal ganglia neurons- initiate and terminate movements, suppress unwanted movement, establish muscle tone Basal ganglia neurons- initiate and terminate movements, suppress unwanted movement, establish muscle tone Cerebellar neurons- monitor movement (posture and balance) Cerebellar neurons- monitor movement (posture and balance) Direct (cerebral cortex- voluntary) and indirect (brain stem) pathways Direct (cerebral cortex- voluntary) and indirect (brain stem) pathways

17. Integrative functions of the Cerebrum Wakefulness and sleep (circadian rhthyms): recticular formation to cerebral cortex Learning and memory: due to plasticity, occurs in stages over time