Chapter 5: The Peripheral Nervous System

1. Chapter 5: The Peripheral Nervous System Unit 3 – Area of Study 1 Mind, brain and body Pages 271-285

2. The Peripheral Nervous System • The Peripheral Nervous System (PNS) is the complete network of neurons located outside the CNS. • The PNS extends from the top of the head to the rest of the body. • The PNS has two main functions: • To carry information from the sensory organs to the CNS. • To convey information from the CNS to the muscles, organs and glands.

3. The Peripheral Nervous System • The PNS can be subdivided into two quite distinct nervous systems, each of which have different functions: • The Somatic Nervous System • The Autonomic Nervous System

4. The Somatic Nervous System • The Somatic Nervous System has both a sensory function and a motor function. • The Somatic Nervous System, also called the Skeletal Nervous System, is the network of neurons that transmits messages from the sensory receptors to the CNS and controls voluntary movement of skeletal muscles through messages sent from the CNS.

5. The Somatic Nervous System • Therefore the Somatic Nervous System allows you to – • Feel any sensations from your external environment. • Make any voluntary movements or actions to respond to your external environment. • Paraplegics and Quadriplegics have had their spinal cord severed at a certain point allowing no neural information to pass through the somatic nervous system below the severed cord. • Learning Activity 5.1– Review questions, pg. 273

6. The Autonomic Nervous System • The Autonomic Nervous System (ANS) is a network of neurons that connects the CNS to all the body’s internal muscles, organs and glands. • When you are suddenly frightened – your heart rate and breathing rate increases, your pupils dilate and goosebumbs appear. The Autonomic Nervous System is responsible for all of these events occurring.

7. The Autonomic Nervous System • The term autonomic means automatic, independentorself governing. • Regardless of our awareness or alertness, the ANS keeps the vital organs and systems of our body functioning, thus maintaining our survival. • This occurs automatically without our conscious control.

8. The Autonomic Nervous System • The ANS modulates (modifies or changes) the activity of visceral muscles, organs and glands. • The ANS receives constant neural activity from the CNS by either increasing or decreasing messages to bring about changes in the body. • While most of the actions controlled by the ANS are not within our control, there are a few responses of the ANS that we can voluntarily control – blinking, heart rate and breathing rate.

9. The Autonomic Nervous System • In India, it has been reported that Yogis (Hindu holy men) can change their heart rate from 75 bpm, to 300 bpm or 50 bpm. • People who aren’t Yogis can also learn to control various autonomic responses using a technique called Biofeedback Training. • Box 5.1 – Keeping the body alive pg. 275 • Learning Activity 5.3– Review questions, pg. 275 • Learning Activity 5.4– Distinguishing between the SNS and the ANS, pg. 276

10. Divisions of the ANS • Most muscles, organs and glands receive messages from two sets of neurons from two distinct divisions of the ANS. • The Sympathetic division is responsible for increasing the activity of muscles, glands and organs in times of vigorous activity, stress or threat. • The Parasympathetic branch is responsible for decreasing the activity of muscles, glands and organs and keeping the body functioning at a normal rate.

11. Divisions of the ANS • When you play a game or sport, the sympathetic nervous system speeds up your heart rate, increases metabolism and induces sweating in order for you to perform to your maximum. • When you stop playing, the parasympathetic nervous system slows your heart and breathing rate, to help the body return to its normal state. • While the sympathetic and parasympathetic nervous systems are both active at the same time, one system usually predominates over the other at any given time.

12. The Sympathetic Nervous System • The sympathetic nervous system originates in the spinal cord, and enhances survival by providing an immediate response, in a split second, to any kind of emergency. • In an emergency situation, the sympathetic nervous system sends a message to the adrenal glands to secrete the hormones adrenalin and noradrenalin. • These hormones are released into the bloodstream and activate muscles organs and glands for preparation of the potential emergency.

13. The Sympathetic Nervous System • The results of these hormones include: • Increased heart rate and blood pressure, • Increased breathing rate, • Increased pupil size, • Increased sweat production, • Decreased digestion, • Heightened senses (ie: goosebumps, see p136)

14. The Parasympathetic Nervous System • The parasympathetic nervous system has the effect of counterbalancing the activities of the sympathetic nervous system. • The parasympathetic nervous system has three main functions: • It keeps the systems of the body functioning efficiently. • It helps maintain a constant internal environment. • It restores the body to a state of calm after vigorous or strenuous activity.

15. The autonomic nervous system

16. The Autonomic Nervous System • Learning Activity 5.5– Review questions, pg. 279 • Learning Activity 5.6– Sympathetic VS Parasympathetic, pg. 279 • Learning Activity 5.7– Summarising the Activities of the Sympathetic and Parasympathetic Nervous Systems, pg. 280 (handout) • Chapter 5 Test, pg. 282-285