Nervous System Amanda Dunne

© The Institute for Optimum Nutrition Learning Outcomes At the end of this session you should be able to: Compare the sympathetic and parasympathetic nervous systems Label a neurone and describe their organisation in nervous systems Describe the mechanism and properties of a nerve impulse  © The Institute for Optimum Nutrition 2

The nervous system The nervous system is the main communication system for the body. A network of billions of nerve cells linked together in a highly organized fashion. Every thought, action and emotion reflects its activity. It communicates with the body cells through electrical impulses which are rapid, specific and cause almost immediate responses.

Basic Functions of the Nervous System Sensation: Monitors changes occurring in and outside the body. Such changes are known as stimuli and the cells that monitor them are receptors. Integration: The parallel processing and interpretation of sensory information to determine the appropriate response. Reaction: Motor output. The activation of muscles or glands (typically via the release of neurotransmitters.

Organization- 2 divisions Central Nervous System The brain + the spinal cord. The center of integration and control Peripheral Nervous System The nervous system outside of the brain and spinal cord Consists of:31 Spinal nerves- Carry info to and from the spinal cord.12 Cranial nerves - Carry info to and from the brain

Central nervous system The brain + the spinal cord. The center of integration and control © The Institute for Optimum Nutrition

The Central Nervous System (CNS) The C.N.S is effectively the center of the nervous system, the part of it that processes the information received from the peripheral nervous system. It is responsible for receiving and interpreting signals from the peripheral nervous system and also sends out signals to it, either consciously or unconsciously. © The Institute for Optimum Nutrition

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Peripheral Nervous System (PNS) The main function of the PNS is to connect the CNS to the limbs and organs. Unlike the central nervous system, the PNS is not protected by bone or by the blood brain barrier, leaving it exposed to toxins and mechanical injuries. Communication between the CNS and the rest of body, divided into: 2 divisions

Sensory & Motor Division Sensory Division - Afferent division Conducts impulses from receptors to the CNS Informs the CNS of the state of the body interior and exterior and can be somatic (from skin, skeletal muscles or joints) or visceral (from organs) Motor Division - Efferent division Conducts impulses from CNS to effectors (muscles/glands) © The Institute for Optimum Nutrition

Motor Efferent Division Somatic nervous system VOLUNTARY (generally) Somatic nerve fibers that conduct impulses from the CNS to skeletal muscles Autonomic nervous system INVOLUNTARY (generally) Conducts impulses from the CNS to smooth muscle, cardiac muscle, and glands.

Autonomic Nervous System (ANS) Involuntary or visceral nervous system Regulates the activity of: Cardiac Muscle (Heart) Smooth Muscle ( In Hollow Organs) Blood Vessels Digestive System Bronchioles Sphincters Glands Adrenal, Digestive glands The Autonomic Nervous System (ANS) * is sometimes referred to as the involuntary or visceral nervous system. It is involuntary because we do not exercise conscious control of its activities. * It regulates the activity of viscera such as cardiac muscle of the heart, * smooth muscle including that in the walls of the hollow organs of the body * such as: * the blood vessels, * the digestive system, * bronchioles and * sphincters. The Autonomic Nervous System also regulates the secretory activity of glands * such as the adrenal glands * and the digestive glands. * * 12

ANS Divisions Sympathetic: Parasympathetic: “Fight or Flight” Activated during emergencies, exercise or vigorous physical activity Revs up body to respond to situations that upset homeostasis Parasympathetic: “Rest & Digest” Reduces energy use Promotes: digestion of food storage of energy elimination of wastes homeostasis The Autonomic Nervous System has two divisions. The first of these is referred to as the sympathetic division. * The sympathetic branch of the ANS is commonly referred to as the “fight or flight” branch, * as it is activated during emergencies, exercise or vigorous physical activity. * Its purpose is the rev up the body to respond to situations,such as anger or fear, * that upset homeostasis . * The parasympathetic division of the ANS * has the opposite effects on its target organs. * It is sometimes referred to as the “rest or digest” branch, * as it strives to reduce energy consumption while promoting activities such as * the digestion of food, * the storage of energy, * the elimination of wastes and * general homeostasis. * 13

Autonomic Nervous System Can be divided into: Sympathetic “Fight or Flight” Parasympathetic “Rest and Digest” These 2 systems are antagonistic. Typically, we balance these 2 to keep ourselves in a state of dynamic balance.

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