Nervous System Pt 1 2024 PDF

Structure: Organisation Of The Nervous System: Part I Mohamad Razif Othman PRH1016 Biology I LU 6: Control And Coordination In Animal And plant LEARNING OUTCOME 1 Describe the organization and the functional unit of the nervous system. Classify the receptors and effectors Describe the...

Structure: Organisation Of The Nervous System: Part I Mohamad Razif Othman PRH1016 Biology I LU 6: Control And Coordination In Animal And plant LEARNING OUTCOME 1 Describe the organization and the functional unit of the nervous system. Classify the receptors and effectors Describe the somatic and autonomic nervous system  Introduction We are constantly bombarded by thousands of changes within the body and from the external environment The survival and homeostatic maintenance depends on identifying and either ignoring or responding to these changes These responses to changes depend on neural signaling The nerves are always working, carrying astonishing amounts of information in the form of tiny electrical pulses called nerve signals. Humans, like all living organisms, can respond to their environment. The human nervous system can be divided structurally into two: The Central Nervous System (CNS) 1.Brain 2.Spinal Cord Peripheral Nervous System (PNS) 1.Sensory (afferent) neurons 2.Motor (efferent) neurons  Major functions of the nervous system Sensory Sensory receptors monitor numerous external and internal stimuli that may be interpreted as touch, temperature, taste, smell, sound, blood pressure, and body position. Action potentials input from the sensory receptor travel along nerves to the spinal cord and brain, where they are interpreted. Integration The brain and spinal cord are the major organs for processing sensory input and initiating responses. The input may produce an immediate responses. May be stored as memory, or may be ignored. The nervous system plays an important role in the maintenance of homeostasis. This function Homeostasis depends on the ability of the nervous system to detect, interpret, and respond to changes in internal and external conditions. In response, the nervous system can stimulate or inhibit the activities of other system to help maintain a constant internal environment. Mental activity The brain is the center of mental activity, including consciousness, memory, and thinking. Skeletal muscle normally contract only when stimulated by the nervous system. Controls of Thus, through the control of skeletal muscle, the nervous system controls the major muscle and glands movements of the body. The nervous system also participates in controlling cardiac muscle, smooth muscle, and many glands. Functional of nervous system (1 / 2) The changes within the body or in the outside world that can be detected by organisms → stimuli. The collecting of information from the internal and external environment is carried out by receptors, especially sense organs such as ears , eyes etc. The response to stimuli depend on activities of a network of nerve cells or neurons. These cells are specialised for transmitting neural signals which are electrical signals and chemical messages. Functional of nervous system (2 / 2) These signals are transmitted from the receptor to the CNS by sensory or afferent neurons The processing and integration of this information and determining the appropriate response is performed by the CNS Neural signals are transmitted from the CNS by motor or efferent neurons to effectors which are muscles or glands. The action be effectors is the response to the stimuli Classification of sensory receptor Classification is divided into : 1. Location 2. Structure 3. Types of stimuli detected Location: Exteroceptors, Visceroceptors , Proprioceptor 1.Exteroceptors Located on or very near the body surface and respond most frequently to stimuli that arise external to the body. Sometimes called cutaneous receptors because their placement in the skin. Examples: Receptor that detect: Pressure Touch Pain Temperature I. Location: Exteroceptors, Visceroceptors , Proprioceptor 2. Visceroceptors (interoceptor) Are located internally, often within the substance of body organs (viscera) When stimulated provide information about the internal environment. Activated by stimuli such as pressure, stretching, and chemical changes that originated in diverse internal organ, such as major blood vessels, intestines, and urinary bladder. Proprioceptor Special type of visceroceptor. Located in skeletal muscle, joint capsule and tendon. Provide us with information about body movement, orientation in space and muscle stretch.  II. Structure: Free & encapsulated nerve ending Divides sensory receptors into either those with: Free nerve endings or Encapsulated nerve ending. Free nerve endings Most widely distributed sensory receptor Include both exteroceptors and visceroceptors Primary receptors for pain - called nociceptors Primary receptors for heat and cold Tactile sensation Tactile disk Root hair plexus II. Structure: Free & Encapsulated nerve ending Encapsulated nerve ending 1. Have connective tissue capsule that surrounds their terminal or dendritic end. 2. Most common primary mechanoreceptors 3. Most activated by a mechanical or deforming type of stimuli. There are six types of encapsulated nerves: 1. Tactile 2. Bulboid 3. Bulbous 4. Lamellar 5. Muscle Spindles 6. Golgi Tendon receptors Free and encapsulated nerve endings III. Stimulus detected 1.Mechanoreceptors Activated by mechanical stimuli that “deform” or change the position of the receptor resulting the generation of receptor potential. Example: pressure applied to the skin, blood vessel, muscle, tendon, etc 2. Chemoreceptors Activated by either the amount or the changing concentration of certain chemical Example: taste and smell, blood glucose, oxygen, carbon dioxide 3. Thermoreceptors Activated by changes in temperature Stimulus detected 4. Nociceptors Activated by intense stimuli of any type that results in tissue damage Example: toxic chemical, intense light, sound, pressure or heat. 5. Photoreceptors In eye 6. Osmoreceptors Detecting change in concentration of electrolytes (osmolarity) in extracellular fluids and intracellular fluid.  Central Nervous System (CNS) The Central Nervous System is effectively the centre of the nervous system, the part of it that processes the information received from the peripheral nervous system. The CNS consists of the brain and spinal cord. It is responsible for receiving and interpreting signals from the peripheral nervous system and also sends out signals to it, either consciously or unconsciously. This information highway called the nervous system consists of many nerve cells, also known as neurons Peripheral Nervous System (PNS) The division of the nervous system containing all the nerves that lie outside of the central nervous system (CNS). The primary role of the PNS is to connect the CNS to the organs, limbs and skin. These nerves extend from the central nervous system to the outermost areas of the body. Nerves that originate from brain are called cranial nerves. Nerves that originate from the spinal cord are called spinal nerves. It connects the brain and spinal cord (CNS) to the rest of the body including the muscles, sensory organs and organs of the respiratory, excretory and circulatory system. Peripheral nervous system contains: 1) Sensory neurons Carry signals from sensory organs to the CNS 2) Motor neurons Carry signals from CNS to the organs and muscles, can be subdivided into:  Somatic nervous system  Autonomic nervous system  Somatic nervous system Part of the peripheral nervous system responsible for carrying sensory and motor information to and from the central nervous system This system contains 2 major types of neurons: 1. Sensory neurons (or afferent neurons) that carry information from the nerves to the central nervous system 2. Motor neurons (or efferent neurons) that carry information from the brain and spinal cord to muscle fibers throughout the body.  Reflex Arc Nerve cells (neurons) carry the message from the stimulated receptors to the correct effectors. A sensory neuron carries the message from the receptor to the central nervous system(the spinal cord and brain). A motor neuron carries the message from the central nervous system to the effector. In a knee-jerk reflex arc: The sensory neuron directly connects to the motor neuron in the spinal cord. This is called a simple reflex arc.  Autonomic nervous system Part of the nervous system that was once thought to be functionally independent of the brain. The autonomic nervous system regulates key functions of the body including the activity of the heart muscle, the smooth muscles and the glands. Controlled by medulla oblongata and hypothalamus of the brain  The autonomic nervous system has 2 divisions: 1. The sympathetic nervous system - accelerates the heart rate, constricts blood vessels, dilates pupils and raises blood pressure (fight or flight) 2. The parasympathetic nervous system - slows the heart rate, increases intestinal and gland activity (rest and digestion) Autonomic Effector Comparison type of neurons Comparison type of neurons LEARNING OUTCOME 2 Identify the structure of neurons Classify the type of neurons Describe the types of neuroglia Compare between the nerves & tracts, Nuclei & Ganglion. Types of nervous cells Nervous tissue is composed of two main cell types: 1.Neurons 2.Neuroglia (Glial cells) Neurons transmit nerve messages, while neuroglia are in direct contact with neurons and often surround them.  Neurons As the basic building block of the nervous system, and that the nervous system functions through transmission of information through networks of neurons. The neuron can be generally divided into three main functional parts: 1. Cell body (soma) 2. Dendrites 3. Axon Two types of neuronal processes project from the cell body: dendrites and axons  Cell body Content ribosomes, rough endoplasmic reticulum, Golgi apparatus to provide protein molecules for transmission of nerve signals from one neuron to another and for maintaining and regenerating the nerve fibers Content mitochondria for energy (ATP) for neuron; some are transported to end of axon  Dendrites Each neuron has one or more dendrites, which branch from cell body Specialised to receive stimuli and send signals to the cell body which integrates incoming signals  Axon Each neuron has one or more dendrites, which branch from cell body Specialised to receive stimuli and send signals to the cell body which integrates incoming signals  Axon Conducts nerve impulses away from the cell body to another neuron, a muscle or gland Divides at its end forming many small branches that end in synaptic terminals Synaptic terminals release neurotransmitters – chemicals that transmit signal from one neuron to another, or from neuron to effector A junction between a synaptic terminal and another neuron is called a synapse Schwann cells - wrap themselves around nerve axons, that a single schwann cell makes up a single segment of an axon's myelin sheath  Myelin sheath 1. Protection and insulation of the nerve fiber. 2. Increases the rate of transmission of nerve impulses. The gaps in the myelin sheath, called the nodes of Ranvier, occur between successive Schwann cells, axon not myelinated Question : Axons of invertebrate animals have no myelin sheaths. How do they compensate? END OF PART ONE