HNU Human Body Function (HBF) 102 ANS Introduction Lecture PDF

Faculty of Medicine Academic Year: 2024-2025 Year: 1 Semester: 1 Module: Human Body Function (HBF) 102 Click to Add Lecture Title By: Abdelrahman Ismail Professor of medical physiology Department: Medical Physiology 11/21/2024 22  Obj...

Faculty of Medicine Academic Year: 2024-2025 Year: 1 Semester: 1 Module: Human Body Function (HBF) 102 Click to Add Lecture Title By: Abdelrahman Ismail Professor of medical physiology Department: Medical Physiology 11/21/2024 22  Objectives 11/21/2024 HBF - 102 33 Control of our body 1) Endocrine glands Control of our body 2) Nervous system COMPONENTS OF THE NERVOUS SYSTEM Anatomically, the nervous system consists of the:- 1) Central nervous system (CNS) 2) Peripheral nerves 7 11/21/2024 8 11/21/2024 Central nervous system 1) Brain: a) Cerebrum b) Cerebellum c) Brain stem: 1)Midbrain 2)Pons 3)Medulla 2) Spinal cord Central nervous system 1) Brain: a) Cerebrum b) Cerebellum c) Brain stem: Midbrain, Pons, and medulla 2) Spinal cord THE PERIPHERAL NERVES ANATOMICALLY: CRANIAL (12 pairs) SPINAL (31 pairs)  THE PERIPHERAL NERVES ANATOMICALLY: I. CRANIAL Nerves (12 pairs) II. Spinal Nerves (31 pairs)  FUNCTIONALLY: SOMATIC: - Sensory (afferent) - Motor (efferent) to skeletal muscles AUTONOMIC: - Sensory (afferent) - Motor (efferent) to:- 1) Cardiac muscle 2) Visceral smooth muscles 3) Glands IMPORTANT DEFINITIONS Sensory (Afferent) nerve: Conducts signals from different organs on to the CNS. Motor (Efferent) nerve: Conducts signals from the CNS on to different organs.  Interactive Question Why Autonomic nervous system (ANS) is so important? 11/21/2024 HBF - 102 19 19 20 11/21/2024 1. ANS is responsible for all the involuntary vital functions, e.g. functions of the cardiovascular, respiratory, and the gastrointestinal system. 2. Dysfunction of the ANS is responsible for many diseases and even death. 3. So many medicines that affect ANS are used to treat so many diseases. FUNCTIONAL DIVISIONS OF THE NERVOUS SYSTEM 1) THE AUTONOMIC NERVOUS SYSTEM Concerned with the involuntary control of the visceral activity. 2) THE SOMATIC NERVOUS SYSTEM Concerned with conscious perception of different sensations, and voluntary control of muscular activity (soma = body). 22 11/21/2024 FUNCTIONAL DIVISIONS OF THE NERVOUS SYSTEM 3) THE INTEGRATIVE NERVOUS SYSTEM Concerned with the sophisticated functions of the brain. These functions include memory, thinking, learning, language, speech, emotions and general behavior.  Reflex action: The basic functional unit of the nervous system. It is an involuntary action in response to a stimulus. Reflex arc: The basic structural unit of the nervous system. It is the anatomical pathway that is involved in the production of a reflex action. The reflex arc has five components 1. Receptor for identifying the stimulus. 2. Afferent nerve for conduction of signals on to the CNS. 3. Center which is a group of cells inside the CNS, which processes the coming signals, and issues the final order for the proper response. 26 11/21/2024 Components of the reflex arc (Cont.) 4. Efferent nerve for conduction of signals out from the CNS on to the effector organ. 5. Effector organ: It is the target of the action. DIFFERENCES BETWEEN THE SOMATIC AND AUTONOMIC REFLEX ARCS 1) Afferent somatic nerves relay in the dorsal or ventral horns of the gray matter of the spinal cord, whilst afferent autonomic nerves relay at lateral horn cells of the spinal cord. Differences between the somatic and autonomic reflex arcs (Cont.) 2) Efferent somatic nerves arise from the ventral horn cells of the spinal cord, whilst efferent autonomic nerves arise from the lateral horn cells. Differences between the somatic and autonomic reflex arcs (Cont.) 3) Efferent somatic fibers go directly to skeletal muscles whilst efferent autonomic fibers relay in autonomic ganglia before supplying the effector organ. 33 11/21/2024 Differences between the somatic and autonomic reflex arcs (Cont.) 4) Efferent somatic nerves supply skeletal muscles only, whilst efferent autonomic nerves supply a variety of structures, i.e. heart, smooth muscles, glands, adipose tissue, and gastrointestinal tract. Differences between the somatic and autonomic reflex arcs (Cont.) 5) Nerve impulse in the somatic motor system is excitatory only, while that of autonomic motor system is either excitatory or inhibitory. Differences between the somatic and autonomic reflex arcs (Cont.) 7) Nerve fibers in somatic system are fast- conducting, thick (9-13 μm), and myelinated. The nerve fibers in autonomic system are slow conducting; preganglionic fibers are lightly myelinated but thin (3 μm), and postganglionic fibers are unmyelinated and very thin (about 1.0 μm).  Interactive Question The efferent autonomic nerves arise in the spinal cord from which of the following? A) Posterior horn cell. B) Anterior horn cell. C) Lateral horn cell. D) Medial horn cell. E) Ventral horn cells 11/21/2024 HBF - 102 39 39 40 11/21/2024 DIVISIONS OF THE AUTONOMIC NERVOUS SYSTEM 1) THE SYMPATHETIC NERVOUS SYSTEM: It is called sympathetic because the components of this system get activated all in one time (i.e. the different components are activated in sympathy with each other). 2) THE PARASYMPATHETIC NERVOUS SYSTEM The components of this system are not activated all in one time. The actions of the parasympathetic system are generally the opposite to that of the sympathetic. 3) THE ENTERIC NERVOUS SYSTEM It is a local system located in the wall of the alimentary tract. It consists of 2 plexuses, i.e. the submucosal (Meissner’s) plexus, and the myenteric (Auerbach’s) plexus, which are interconnected by intermediary nerves.  The 3 systems are interconnected and their functions are integrated and coordinated by centers in the CNS. Autonomic nerves has sensory components Autonomic nervous system has an afferent component. These are the afferent nerves, which are part of reflex arcs of any autonomic reflex.  Interactive Question Enumerate the differences between somatic and autonomic reflex arcs. 11/21/2024 HBF - 102 50 50  Summary 1)The human body is controlled by both of the endocrine and the nervous system 2)Nervous system is anatomically composed of central nervous system (Brain and spinal cord) and the peripheral nervous system (Cranial and spinal nerves) 3)Peripheral nerves are either afferent (Sensory) or efferent (motor) nerves 4)Nervous system is functionally composed of somatic and autonomic nervous systems 11/21/2024 HBF - 102 51 51  Summary 5) The are many differences between the somatic and autonomic reflex arc, which is the structural unit of the nervous system 6) The autonomic nervous system is necessary to live a normal life. 7) The autonomic nervous system is composed of sympathetic, parasympathetic, and enteric nervous systems 11/21/2024 HBF - 102 52 52  References - Costanzo: BRS Physiology Seventh Edition, 2019 - Abu-Sitta et al.: Physiology in medical practice, Cell physiology and autonomic nervous system, 2018 - Guyton and Hall: Textbook of medical physiology: 14th. Edition; Philadelphia: Elsevier, Inc.,2020. 11/21/2024 HBF - 102 53 53