Nervous System Part II 2024 PDF

STRUCTURE: O R G A N I S AT I O N O F T H E N E RV O U S S Y S T E M : PA RT I I M O H A M A D R A Z I F O T H M A N P R H 1 0 1 6 B I O L O G Y I L U 6 : C O N T R O L A N D C O O R D I N A T I O N I N A N I M A L A N D P L A N T  P R E V I O U S LY I N PA RT 1  Organisation...

STRUCTURE: O R G A N I S AT I O N O F T H E N E RV O U S S Y S T E M : PA RT I I M O H A M A D R A Z I F O T H M A N P R H 1 0 1 6 B I O L O G Y I L U 6 : C O N T R O L A N D C O O R D I N A T I O N I N A N I M A L A N D P L A N T  P R E V I O U S LY I N PA RT 1  Organisation of nervous system  Classification of sensory receptor  Somatic nervous system  Autonomic nervous system  Types of cells in nervous systems STRUCTURAL C L A S S I F I C AT I O N OF NEURONS Generally divided into 3 types: Unipolar Bipolar Multipolar  U N I P O L A R N E U RO N A neuron from which only a single process leaves the cell body; this single process then divides close to the cell body into a trunk to supply the branching dendrites for incoming signals and an axon for outgoing signals; Unipolar neurons are typically sensory neurons with receptors located within the skin, joints, muscles, and internal organs; their axons are usually long, terminating in the spinal cord, while the length of their dendritic trunks vary.  B I P O L A R N E U RO N A neuron from which two processes leave the cell body; in this neuron, the dendritic tree emerges from one end of the cell body, while the axon emerges from the opposite end; The dendritic branching of bipolar neurons is typically limited, and the axons of such neurons are usually short in length. Bipolar neurons are often sensory neurons associated with receptor organs of the visual and auditory systems.  M U LT I P O L A R N E U R O N One of the structural classifications of neurons: a neuron from which multiple branches leave the cell body; the many dendrites of the multipolar neuron allow for extensive integration of information coming from many other neurons The axons of such neurons are usually long, allowing this integrated information to affect distant regions of the nervous system. This is the majority of the neurons in the body  FUNCTIONAL TYPES OF N E U RO N S Sensory neurons have long axons and transmit nerve impulses from sensory receptors all over the body to the central nervous system Motor neurons also have long axons and transmit nerve impulses from the central nervous system to effectors (muscles and glands) all over the body. Interneurons (also called connector neurons or relay neurons) are usually much smaller cells, with many interconnections. Question: What is pseudounipolar neuron?  N E U RO G L I A Glial cells, commonly called neuroglia or simply glia (Greek for "glue"), are non- neuronal cells (which do not have the property of excitability or conductivity possessed by neurons) Maintain homeostasis, form myelin, and provide support and protection for the brain’s neurons. The four main functions of glial cells are:  To surround neurons and hold them in place  To supply nutrients and oxygen to neurons  To insulate one neuron from another  To destroy pathogens and remove dead neurons.  T Y P E S O F N E U RO G L I A 1. Astrocytes 2. Ependymal cells 3. Microglial cells 4. Oligodendrocytes 5. Schwann cells All are found in CNS except Schwann cells in PNS A S T RO C Y T E S Astroglial cells, also known as "astrocytes" are found throughout the Central Nervous System (CNS), that is in the tissues of the brain and spinal cord. M I C RO G L I A L C E L L Microglial cells are sometimes known simply as "microglia" and are found in the Central Nervous System (CNS) E P E N DY M A L C E L L Ependymal cells are found in the Central Nervous System (CNS) O L I G O D E N D RO C Y T E Oligodendrocyte cells are found in the Central Nervous System (CNS)  S C H WA N N C E L L Schwann cells are found in the Peripheral Nervous System (PNS), that is around the nerves of the extremities of the body, e.g. located in the skin C O M PA R I S O N B E T W E E N O L I G O D E N D RO C Y T E S A N D S C H WA N N C E L L S Similarity: Both Oligodendrocytes and Schwann Cells facilitate the formation of myelin around the axons of nerve cells. Difference: However, Schwann Cells are found in the Peripheral Nervous System (PNS), and form myelin around a portion of a single axon only. Oligodendrocytes are found in the Central Nervous System (CNS), and each oligodendrocyte can form myelin around several axons.  NUCLEI VS GANGLIA In the central nervous system, a collection of neuron cell bodies is called a nucleus. (plural: nuclei) In the peripheral nervous system, a collection of neuron cell bodies is called a ganglion (plural: ganglia).  T R A C T V S N E RV E S A tract is a collection of nerve fibres (axons) in the central nervous system (CNS). A nerve is a collection of nerve fibres (axons) in the peripheral nervous system (PNS). N E RV E S - B U N D L E S O F P E R I P H E R A L N E RV E F I B E R S ( A X O N S ) H E L D T O G E T H E R B Y S E V E R A L L AY E R S O F C O N N E C T I V E T I S S U E. M Y E L I N AT E D V S U N M Y E L I N AT E D Nerves fibres may be myelinated or unmyelinated. In CNS myelin is formed by oligodendrocytes, and in peripheral nerves by Schwann cells (neurolemmocytes). In myelinated fibres, the regions where longitudinally adjacent Schwann cells or oligodendrocyte processes a join one another are the nerve fibre nodes (of Ranvier). M Y E L I N AT E D V S U N M Y E L I N AT E D The white matter of the nervous system is essentially a mass of nerve fibres and is so called because of the general pale appearance imparted by the fatty myelin, in the contrast to grey matter which is darker and consists essentially of cell bodies. The largest myelinated fibres may be motor or *proprioceptive and the smallest, whether myelinated or unmyelinated, are autonomic or sensory. White matter PNS- myelinated nerves CNS- myelinated tracts Gray matter: made up of cell bodies and unmyelinated fibers CNS – referred to as nuclei PNS – referred to as ganglia  LEARNING O U TC O M E S 3 Describe 2 protective covering of central nervous system. Describe the structure & function of the brain and cranial nerves Describe the structure & function of spinal cord and spinal nerves Compare the structure & function of somatic and autonomic nervous system  2 P ROT E C T I V E COVERINGS FOR CNS Outer covering is bone; cranial bones encase the brain, and vertebrae encase the spinal cord. Inner covering is the meninges; the meninges of the cord continue inside the spinal cavity beyond the end of the spinal cord  MENINGES : 3 MEMBRANOUS L AY E R S Dura mater Strong, white fibrous tissue; outer layer of meninges and inner periosteum of the cranial bones. Arachnoid mater Delicate, cobweblike layer between the dura mater and pia mater. Pia mater Innermost, transparent layer; adheres to the outer surface of the brain and spinal cord; contains blood vessels; beyond the spinal cord, forms a slender filament called filum terminale, at level of sacrum THE BRAIN CAN BE DIVIDED I N TO :  CEREBRUM Largest, most superior region of brain Divided into right and left hemispheres Connected by the corpus callosum Functionally responsible for complex processing of sensory and motor information; complex integrative functions Cerebral cortex highly wrinkled gray-matter surface of the cerebrum; divided into four major lobes per hemispheres; functionally mapped based on concept of location  CEREBRUM Cerebral tracts consist of white-matter tracts connect various region of the cortex with each other and with inferior CNS structures, conducting information between CNS areas to facilitate complex processing and integration Basal nuclei consist of gray-matter nuclei deep in the cerebrum integrating and regulating of conscious motor control, especially posture, walking, other repetitive movements; posture roles in thinking and learning.  LO B E S O F THE BRAIN Frontal Lobe - associated with reasoning, planning, parts of speech, movement, emotions, and problem solving Parietal Lobe - associated with movement, orientation, recognition, perception of stimuli Occipital Lobe - associated with visual processing Temporal Lobe - associated with perception and recognition of auditory stimuli, memory, and speech D I E N C E P H A LO N BRAIN STEM BRAIN STEM CEREBELLUM Structure 1) Second largest part of the brain 2) Contains more neurons than the rest of the nervous system. Function Coordinates many functions of cerebral cortex including: Planning and control of skilled movements, posture, balance, Coordination of sensory information relating to body position and movement. END OF PA RT I I