The peripheral nervous system connects the central nervous system to the rest of the body and is divided into sensory and motor divisions. It has two main subdivisions: the somatic nervous system which controls voluntary skeletal muscles, and the autonomic nervous system which regulates involuntary functions like digestion. The autonomic nervous system has two divisions - the sympathetic "fight or flight" system and the parasympathetic "rest and digest" system. Reflexes are involuntary responses to stimuli that involve reflex arcs in the spinal cord or brain.

1. Peripheral Nervous System

2. The Basics: Works together with CNS Provides a flow path to/from brain Links CNS to and from the real world Can classify sensory receptors by stimulus type or by location

3. PNS Divisions Sensory division - input; travels to CNS Motor division - output; travels away from CNS Motor subdivisions: Somatic nervous system Autonomic nervous system

4. Somatic Nervous System Also called the voluntary nervous system It allows us to consciously control our skeletal muscles….how? By providing a pathway for those signals to reach the neuromuscular junction from the CNS Major neurotransmitter: acetylcholine

5. Autonomic Nervous System Innervates cardiac & smooth muscle, and glands Major neurotransmitters: acetylcholine, norepinephrine Broken into two subdivisions; dual innervation! Both subdivisions serve same visceral organs…. But, cause opposite effect! One division stimulates, the other inhibits

6. Sympathetic Division Also called the “fight or flight” system Stressful situations cause: Deep breathing, cold/sweaty skin, dilated pupils, and electrical resistance of skin (galvanic skin resistance) GSR - used in lie detector tests Constricts blood vessels, autonomic activity decreased Provides optimal conditions to a response from a threat to homeostasis

7. Parasympathetic Division Most active in non-stressful situations Called “resting & digesting” system Tries to keep body energy use as low as possible This is why we rest after a heavy meal ….. … .digestion not interfered with by sympathetic activity Nerve fibers emerge from brain and sacral areas

8. Reflex Activity Reflex = a rapid, predictable motor response to a stimulus Involuntary & unlearned Involves “reflex arcs” Classified as somatic reflexes and autonomic (visceral) reflexes Same pathway as feedback mechanism - but integration occurs in spinal cord

9. Reflex Types/Examples Flexor (withdrawal) reflex - response when you prick your finger with a needle Crossed extensor reflex - e.g. when someone unexpectedly grabs your arm or you step barefoot on broken glass. Important in balance!! Superficial reflex - caused by gentle cutaneous (skin) stimulation - spider or tick crawling on your skin Plantar reflex - caused by pushing a blunt object downward along the sole of the foot (toes will curl)

10. Electrical Brain Activity Measured by an electroencephalogram (EEG) Unique to every individual Each of us has brain wave pattern as unique as a fingerprint But ….can group into four frequency classes:

11. Alpha Waves Low-amplitude Slow Synchronous 8-13 Hz Indicate a calm, relaxed state of wakefulness

12. Beta Waves Rhythmic More irregular than alpha waves Higher frequency; 14-25 Hz Occur when awake & mentally alert (concentrating on things)

13. Theta Waves Irregular waves Frequency of 4-7 Hz Considered abnormal in people who are awake

14. Sleep Significance not really understood Sleep requirements: 16 hrs/day for infants 7 hrs/day for adults Possible hypotheses: Recharge mechanism Dream to forget Other ….??? There are different stages of sleep

15. NREM Stages Stage 1 - eyes closed, relaxed. Drifting sensation occurs. Alpha waves. Stage 2 - EEG becomes more irregular, arousal more difficult Stage 3 - Deeper sleep, alpha & delta waves occur. Relaxed skeletal muscles. Dreaming. 20 minutes after stage 1 Stage 4 - slow wave sleep; sleepwalking & bedwetting occur here. Vital signs at lowest levels.

16. REM Sleep Very irregular brain waves Eyes move rapidly Starts approx. 90 minutes after sleep begins Often called “paradoxical” sleep. (EEG pattern looks like when we’re awake) Most dreaming occurs here

17. Memory Memory storage occurs in stages Short-term memory (STM) and Long-term memory (LTM) STM - limited to 6-7 chunks of information Transfer from STM to LTM depends on: Emotional state Rehearsal Automatic memory Memory must consolidate

18. Memory Categories Fact (declarative) memory Learning names, faces, words, dates, etc Skill (procedural) memory Less conscious learning Acquired only through practice Best remembered by doing