OS 202 Human Body & Mind 1: Integration and Control Systems - Neurons & Nervous System PDF

OS 202: HUMAN BODY AND MIND 1: INTEGRATION AND CONTROL SYSTEMS NEURONS & THE NERVOUS SYSTEM UPCM 2029 | Dr. Ronnie Baticulon | LU3 A.Y. 2024-2025 Include motor neurons and int...

OS 202: HUMAN BODY AND MIND 1: INTEGRATION AND CONTROL SYSTEMS NEURONS & THE NERVOUS SYSTEM UPCM 2029 | Dr. Ronnie Baticulon | LU3 A.Y. 2024-2025 Include motor neurons and interneurons of the brain and spinal OUTLINE cord I. What is a Neuron? III. How is the Nervous B. SYNAPSES A. Types of Neurons System Organized? Neurons communicate with each other through synapses Based on Morphology A. Central Nervous Action potential transmission: B. Synapses System ○ Axon → Axon terminal → Release of neurotransmitters → II. What are Glial Cells? B. Peripheral Nervous information is received by dendrites of succeeding neuron A. Types of Glial Cells in System the CNS C. Autonomic Nervous Myelinated axon increases the velocity of action potential B. Types of Glial Cells in System ○ Myelin acts as an “insulator” the PNS IV. How Do You Name Parts ○ Diseases that destroy myelin decrease the transmission of of the Nervous System? information across axons V. Clinical Correlates Clinical Importance[UPCM 2027 Trans] VI. References If the axon is cut, information will not be transmitted, leading to paralysis. I. WHAT IS A NEURON? Brain tumor affecting the frontal lobe can damage the cell bodies Neurons are the functional unit of the nervous system in the frontal lobe → paralysis in hands Composed of the cell body, with an axon and dendrites arising Acetylcholine (neurotransmitter) is released from the axon from it terminal and transmitted to the dendrites of the next neuron. ○ Information will not be transmitted if acetylcholine is blocked. Myelin/Sphingomyelin ○ A sphingolipid that insulates axons ○ Increases the velocity of nerve transmission Multiple sclerosis ○ A demyelinating disease wherein the body destroys its own myelin Figure 1. A Typical Neuron Cell body AKA “perikaryon” or “soma” Contains the nucleus and cell organelles The basophilic staining is contributed by Nissl bodies present within ○ Represent polysomes and rough endoplasmic reticula, signifying the high activity of protein synthesis Dendrites Receive information from other neurons There are several branches attached to the cell body Axon Transmits inputs towards other neurons’ dendrites in the form of an action potential to the axon terminal A. TYPES OF NEURONS BASED ON MORPHOLOGY Figure 3. Action potential in neurons[Blumenfeld, 2021] II. WHAT ARE GLIAL CELLS? Supporting cells of the nervous system Thought to be the “glue” which keeps the brain from falling apart A. TYPES OF GLIAL CELLS IN THE CNS Types of glial cells in the CNS: ○ Astrocytes ○ Oligodendrocytes ○ Microglia ○ Ependymal cells ASTROCYTES Most abundant cell type Serve a structural and metabolic function Help maintain the Blood-Brain Barrier (BBB) Have an important function in cellular repair processes Play a role in the migration of neurons during development of the Figure 2. Types of Neurons Based on Morphology brain and spinal cord Bipolar neurons Have one dendrite and one axon connected to the cell body Sensory-type Located in the olfactory epithelium, retina, and in the organ for hearing and balance in the inner ear Unipolar/Pseudounipolar neurons Have only one process leaving the cell body Why pseudounipolar? ○ Initially bipolar, then proximal segments fused together ○ E.g. sensory ganglia of cranial and spinal nerves Multipolar neurons Most abundant Figure 4. Astrocytes Multiple branched dendrites with a single axon on the opposite side EPENDYMAL CELLS Trans 04 TG7: Chu, Chua, A., Chua, S. Claridad, Comia, Cornelio, Cortez, A. TH: Oribello 1 of 6  Function in producing and aiding the movement of cerebrospinal fluid (CSF) Located on the lining of the ventricles and the central canal of the spinal cord Figure 9. Satellite cell III. HOW IS THE NERVOUS SYSTEM ORGANIZED Organized into two parts: Figure 5. Ependymal Cells ○ Central Nervous System ○ Peripheral Nervous System Each is separate, but interdependent with one other OLIGODENDROCYTES Termed collectively as “oligodendroglia” C. CENTRAL NERVOUS SYSTEM Produces myelin in the CNS Consisting of the brain and spinal cord ○ Increases conduction velocity of neurons There are seven major divisions: ○ Cerebral hemisphere ○ Diencephalon Thalamus Hypothalamus ○ Midbrain ○ Pons ○ Cerebellum ○ Medulla ○ Spinal cord Brain stem = Midbrain, Pons, and Medulla Figure 6. Oligodendrocytes MICROGLIA Macrophages of the CNS Unique; they do NOT originate from the nervous system Perform a defense and immune function Figure 10. Major divisions of the CNS Figure 7. Microglia B. TYPES OF GLIAL CELLS IN THE PNS Types of glial cells in the PNS: Figure 11. Different divisions of the CNS ○ Schwann cells ○ Satellite cells D. PERIPHERAL NERVOUS SYSTEM Consists of cranial nerve, spinal nerves, and their associated SCHWANN CELLS ganglia Produce myelin ○ Cranial nerves Analogue to oligodendrocytes 12 cranial nerves: 10 from brainstem ○ Midbrain: CN 3 and 4 ○ Pons: CN 5, 6, 7, and 8 ○ Medulla: CN 9, 10, 11, and 12 2 in the base of the frontal lobe ○ Olfactory nerve (CN 1) ○ Optic nerve (CN 2) Motor, sensory, and autonomic functions in the head and neck area CN 11 (spinal accessory nerve) is the only cranial nerve from the spinal cord ○ Spinal nerves Arises from the spinal cord and connects it to the external environment Motor, sensory, and autonomic functions in the trunk and rest of the body Figure 8. Schwann cell Function: help the body interact with the environment SATELLITE CELLS ○ Either transmit sensory information or help mediate more Provide support to the cell bodies of the ganglion function OS 202 Neurons & The Nervous System 2 of 6  Figure 12. Peripheral Nervous System[Martin, 2021] Nice to know[UPCM 2027 Trans] Dorsal root → sensory Ventral root → motor Dorsal root ganglion → pseudounipolar Figure 14. Parasympathetic nerves of ANS(Blumenfeld) Ganglion → collection of cell bodies in the PNS Arises from cranial nerves and 2nd to 4th sacral nerves (S2-S4) Humans have 33 vertebrae: 7 cervical, 12 thoracic, 5 lumbar, 5 For “Rest or Digest” mechanism sacrum, 4 coccyx (fused Adults only have 26 vertebrae because bones fuse as we age. SOMATIC DIVISION OF PNS Cell bodies are found in the peripheral ganglia Provides sensory innervation of the body tissues and motor ○ E.g. dorsal root ganglia and sympathetic ganglia innervation of the skeletal muscles Axons are contained in peripheral nerve There are 31 pairs of spinal nerves ○ E.g. in brachial plexus ○ 8 cervical ○ 12 thoracic AUTONOMIC DIVISION OF PNS ○ 5 lumbar ○ 5 sacral Autonomic nervous system ○ 1 coccygeal ○ Division of peripheral nervous system Dermatomes ○ Controls the glands and smooth muscles of the viscera and blood ○ Different parts of the body are subserved by different spinal vessels nerves ○ Has sympathetic and parasympathetic divisions ○ Muscles of the body are innervated by different peripheral nerves Sympathetic division of ANS arising from different segments of the spinal cord E.g. T4 spinal nerves directly affect sensation around the 4th intercostal space which is generally level with the nipples, while T10 spinal nerves directly affect sensation in the umbilical area Figure 15. Dermatomes of a person assuming a quadrupedal position (A), and Sagittal view of the spinal cord showing the origin of nerves corresponding to each of the dermatomes (B)[Sadock et al., 2018] Figure 13. Sympathetic nerves of ANS(Blumenfeld) IV. HOW DO YOU NAME PARTS OF THE NERVOUS SYSTEM? Arises from thoracolumbar levels Table 1. GRAY AND WHITE MATTER IN THE CNS From 1st thoracic (T1) to 3rd lumbar (L3) spinal nerves BRAIN SPINAL CORD For “Flight or Flight” mechanism Gray matter OUTSIDE Gray matter INSIDE (in the cortex) (contains cells bodies) White matter INSIDE (with deep gray matter White matter OUTSIDE (with components (nuclei) containing ascending and descending cell bodies and dendrites found axons) deep inside it) Parasympathetic division of ANS OS 202 Neurons & The Nervous System 3 of 6  Imaging impressions: ○ Left side is darker (hypodense) Mainly in the left frontal region of the brain Hypodensity is caused by ischemic stroke Causing aphasia and right-sided weakness Ischemic stroke Figure 16. Gray and white matter in CNS. Peripheral nervous system ○ Cell bodies are found in the peripheral ganglia E.g. dorsal root ganglia and sympathetic ganglia ○ Axons are contained in peripheral nerves Figure 19. Mechanisms of ischemic stroke E.g. in brachial plexus Remains one of the leading causes of deaths in the Philippines V. CLINICAL CORRELATES Blood clot occludes one of the major blood vessels of the brain → decrease in blood flow → decreased oxygen and nutrients to that A. IMAGING ORIENTATION part of the brain tissue → cell death Ischemic stroke histopathology Figure 17. Orientation and Planes of Sections(Blumenfeld) Axial cuts (Figure A) ○ Viewing images from rostral to caudal/top to bottom or the reverse ○ When viewing, imagine the patient lying down and you are at the foot side of the bed Coronal cuts (Figure B) ○ Viewing images anterior to posterior/front to back or reverse Sagittal cuts (Figure C) Figure 20. Red neurons in the ischemic brain tissue ○ Viewing images left to right or right to left Red neurons B. CASE 1: ISCHEMIC STROKE ○ Indicates brain tissue damage due to ischemia ○ Eosinophilic neurons seen in neuron cell death ○ Due to decreased levels of Oxygen and nutrients brought about by the occlusion of blood supply A. REFERENCES Baticulon, R.E. (2022). Neurons and the Nervous System [PowerPoint Presentation] Blumenfeld, H. (2010). Neuroanatomy through Clinical Cases (2nd Ed). Sinauer Associates, Inc. UPCM 2027 Trans (2022). Introduction to Neuroscience. Figure 18. Imaging of a patient’s brain: axial (left) & coronal (right) History, signs, and symptoms: ○ 44 y/o female ○ Sudden onset of aphasia (difficulty speaking) ○ Right-sided weakness OS 202 Neurons & The Nervous System 4 of 6  APPENDIX Figure 21. Types of Glial Cells in the CNS Figure 22. Different divisions of the CNS Figure 23. Peripheral Nervous System OS 202 Neurons & The Nervous System 5 of 6  Figure 24. Orientation and Planes of Section Figure 25. Sympathetic and Parasympathetic divisions of the PNS OS 202 Neurons & The Nervous System 6 of 6