Nervous System Lecture Outline PDF

06/12/2024 Lecture Outline Overview NERVOUS SYSTEM Structure of the Nervous System...

06/12/2024 Lecture Outline Overview NERVOUS SYSTEM Structure of the Nervous System Function of the Nervous System Neurophysiology Department of Biology College of Mathematics and Natural Sciences Caraga State University 2 Importance of the Nervous (NS) Functions of the Nervous System and Endocrine Systems (ES) Act together to coordinate functions of all body PERCEPTIONS, BEHAVIORS, and MEMORIES systems  Sensory function (detect stimuli) Maintaining homeostasis  Integrative function (integrates sensory info) Nervous system (respond rapidly via nerve impulses) for perceptions, behaviors, memories  Motor function (activate effector) Endocrine (responds slowly via hormones) Q1: what branch of medical science that deals with normal functioning and disorders of the nervous system? 3 4  06/12/2024 A. Anatomy of the Nervous System  ~3% of total body weight  is a knotlike swelling in a nerve where the cell bodies of  Highly organized network neurons are concentrated of billions of neurons and more neuroglia  a bundle of nerve fibers (axons) wrapped in fibrous connective tissue 5 6 Histology of Nervous Tissue NEURONS or Nerve Cells NEUROGLIA Functional unit of the NS It supports, nourish, & Responsible for sensing, protect the neurons and thinking, remembering, maintain homeostasis in the controlling muscle activity, & interstitial fluid that surround regulating glandular nervous tissues secretions Possess electrical excitability →action potential 7 8  06/12/2024 Parts of most Neurons Classification of Neurons 1. Structural classification – based on number of 1. Cell body/ soma/ processes extending from the cell body perikaryon  Multipolar neurons, bipolar neurons, 2. Nerve fiber: unipolar/pseudounipolar neurons Dendrites and axon 2. Functional classification – according to the direction the nerve impulse is conveyed to the CNS  Sensory/afferent neurons, motor/efferent neurons, interneurons/association neurons 9 10 11 12  06/12/2024 Neuroglia Neuroglia of the CNS 6 types 50% vol of CNS Classified based on Size; Cytoplasmic processes; Intracellular organization Smaller than Microglia – small cells with slender processes neurons, but 5-50x with spikelike projections, it function as more numerous phagocytes Do not generate Ependymal cells – cuboidal to columnar cells action potentials & arranged in single layer that have microvilli & can multiply/divide cilia, help circulating the cerebrospinal fluid 13 14 Neuroglia of the CNS Oligodendrocytes – smaller & contain fewer processes forming and maintaining myelin sheath around CNS axons Astrocytes – many processes, protoplasmic vs fibrous astrocytes. It wrapped around blood capillaries & secrete GDNF (glial-derived neurotrophic factor), SHh, FGF, etc that support BBB integrity and permeability 15 16  06/12/2024 Neuroglia of the PNS Neuroglia of the PNS Schwann cells – wrapped the PNS axons, form myelin sheath, 1SC=1axon, 1SC can enclose >20 unmyelinated axons Satellite cells – flat cells surround the cell bodies of neurons of PNS ganglia for structural support & regulate exchanges of materials between neuronal cell bodies and IF 17 18 19 20  06/12/2024 Groupings of Nervous Tissue Neuronal cell bodies grouped together in clusters The axons of neurons grouped together in bundles Gray matter vs white matter Consists of neuron cell bodies, Consists of myelinated axons of dendrites, unmyelinated axons, many neurons axon terminals, and neuroglia Distribution of gray matter and white matter in the spinal cord and brain. 21 22 23 24  06/12/2024 Gross Anatomy of the Brain Adult brain has 4 major parts: brain stem, cerebellum, diencephalon, & cerebrum Classified into 6 postembryonic divisions: telencephalon, diencephalon, mesencephalon, pons, medulla oblongata, & cerebellum Covered by the cranium and the cranial meninges Surrounded with cerebrospinal fluid (CSF) 25 26 27 28  06/12/2024 Protective Coverings of the Brain Cranium Cerebrospinal fluid Cranial meninges 1. Outer dura mater 2. Middle arachnoid mater 3. Inner pia mater CSF: Mechanical & chemical protection, circulation 29 30 Brain Blood Flow and the Blood-Brain Barrier (BBB) Blood flows to the brain via internal carotid and vertebral arteries The internal jugular veins return blood from the head to the heart 31 32  06/12/2024 Brain Gyri (ridges) and Sulci (grooves) 33 34 BRAIN STEM (Vital Link) 1. MEDULLA OBLONGATA – contains all sensory tracts and motor tracts, nuclei (reg rate and , control reflexes for vomiting, swallowing sneezing, coughing, etc); cranial nerves: BRAIN IX, X, XI, and XII 2. PONS – connects the diff parts of the brain by bundles of axons (cerebral cortex into cerebellum), nuclei (vestibular n., pneumotaxic and apneustic areas control breathing); cranial nerves: V, VI, VII, and VIII 35 36  06/12/2024 BRAIN STEM (Vital Link) CEREBULLUM (Movement & Balance) 3. MIDBRAIN – extends from the pons to the Attached to the brainstem by 3 cerebellar peduncles diencephalon, nuclei (reflex centers for visual activities; Contains the hemispheres (2 lateral lobes separated neurons that release dopamine that help control by fissures), vermis (midline structure) subconscious muscle activities; voluntary movements of the limbs); cranial nerve: III and IV Motor coordination, balance and posture, muscle tone, motor learning, cognitive functions 4. RETICULAR FORMATION – a region where white and gray matter exhibit a netlike arrangement, here include the reticular activating system (RAS) = consciousness 37 38 DIENCEPHALON (A Key Brain Region) THALAMUS – relay center for sensory & motor info by processing and integrating sensory data before sending it to the cerebral cortex HYPOTHALAMUS – regulation: homeostasis, hunger, thirst, body temp, sleep-wake cycles, hormone secretion EPITHALAMUS – involved in the pineal gland SUBTHALAMUS – motor control 39 40  06/12/2024 CEREBRUM (Seat of Intelligence) Cognitive and motor functions: Thought and perception, language, memory, emotions, voluntary movement The cerebral hemisphere is subdivided into 4 lobes after the bones that cover them: frontal, parietal, temporal, & occipital lobes 41 42 CEREBRUM (Seat of Intelligence) BASAL GANGLIA – 3 nuclei (masses of gray matter) within each cerebral hemisphere, receive input from & send output to various regions of the cerebral cortex, for motor control, learning, memory, decision-making THE LIMBIC SYSTEM – the emotional brain, olfaction & memory 43 44  06/12/2024 Cerebral Lobes CRANIAL NERVES 1. Frontal – executive functions, voluntary movement, 1. SENSORY NERVES – CN I Olfactory (smell), CN II attention and concentrations Optic (sight); CN VIII Vestibulocochlear (hearing and 2. Parietal – sensory processing, spatial awareness, balance) number sense (mathematical calculations) 2. MOTOR NERVES – CN III Oculomotor (movement of 3. Temporal – auditory processing, memory formation, eye, pupil dilation, eyelid opening, CN IV Trochlear emotional processing and regulation and CN VI (movement of eye); CN V Trigeminal (sensation of the face, chewing) cont’n… 4. Occipital – visual processing, object recognition, and color perception 45 46 CRANIAL NERVES 12 CRANIAL NERVES Olfactory nerve (CN I), optic nerve (CN II), oculomotor 2. MOTOR NERVES – CN VII Facial (facial expression, nerve (CN III), trochlear nerve (CN IV), trigeminal nerve taste, tears, saliva), CN IX Glossopharyngeal (taste, (CN V), abducens nerve (CN VI), facial nerve (CN VII), swallowing, saliva), CN X Vagus (swallowing, voice, vestibulocochlear nerve (CN VIII), glossopharyngeal heart rate, digestion), CN XI Accessory (movement of the nerve (CN IX), vagus nerve (CN X), accessory nerve head and shoulders), CN XII Hypoglossal (movement of (CN XI), and hypoglossal nerve (CN XII). the tongue) Mnemonics: Oh, Oh, Oh, To Touch And Feel Very Good Velvet, https://rotel.pressbooks.pub/biologicalpsychology/chapter/the-brain/ such-A Heaven 47 48  06/12/2024 SPINAL CORD A long, thin bundle of nervous tissue that extends from the base of the brain to the sacrum Body vertebrae & connective tissue meninges + CSF The spinal cord is divided into four regions: cervical, thoracic, lumbar, and sacral. 49 50 SPINAL NERVES 31 pairs composed of a dorsal (sensory neurons) root and ventral (motor neurons) root Spinal nerves are grouped into: - Cervical Nerves (C1-C8): Supply the head, neck, shoulders, and upper limbs. - Thoracic Nerves (T1-T12): Supply the chest, upper back, and abdomen. - Lumbar Nerves (L1-L5): Supply the lower back, hips, and legs. - Sacral Nerves (S1-S5): Supply the pelvis, genitals, and lower limbs. - Coccygeal Nerve (Co1): Supplies the tailbone. 51 52  06/12/2024 NEUROPHYSIOLOGY Electrical Signal and Neurotransmitters 53 MEMBRANE POTENTIALS Neurophysiology AND ACTION POTENTIALS the study of the function of the nervous system. It Electrical potentials exist across the membranes of virtually explores how neurons, the fundamental units of the all cells of the body. nervous system, communicate and interact to produce 1. Cells such as nerve and muscle cells, are capable of complex behaviors and cognitive processes. generating rapidly changing electrochemical impulses at their membranes, and these impulses are used to transmit signals along the nerve or muscle membranes. DIFFUSION POTENTIAL, RESTING MEMBRANE 2. glandular cells, macrophages, and ciliated cells, local POTENTIAL, AND ACTION POTENTIAL changes in membrane potentials also activate many of the cells’ functions. 55 56  06/12/2024 ION CHANNELS 57 58 Nerve Action Potential Nerve signals are transmitted by action potentials, which are rapid changes in the membrane potential that spread rapidly along the nerve fiber membrane. Each action potential begins with a sudden change from the normal resting negative membrane potential to a positive potential and then ends with an almost equally rapid change back to the negative potential. To conduct a nerve signal, the action potential moves along the nerve fiber until it comes to the fiber’s end. 59 60  06/12/2024 The successive stages of Action Potential the action potential are as follows: Resting Membrane Potential: The electrical charge difference across the cell membrane of a neuron at rest. Depolarization: A decrease in the resting membrane 1. Resting Stage. potential, making the neuron more likely to fire an action 2. Depolarization Stage. potential. Threshold: The critical level of depolarization that must be 3. Repolarization Stage. reached for an action potential to occur. Repolarization: The return of the membrane potential to its resting state.tion: 61 62 All-or-Nothing Principle Once an action potential has been elicited at any point on the membrane of a normal fiber, the depolarization process travels over the entire membrane if conditions are right, or it does not travel at all if conditions are not right. This is called the all-or-nothing principle, and it applies to all normal excitable tissues. 63 64  06/12/2024 65 66 67 68  06/12/2024 69 70 Synaptic Transmission Chemical Synapses: The most common type of synapse, where neurotransmitters are released into the synaptic cleft. Neurotransmitters: Chemical messengers that transmit signals between neurons. Examples: acetylcholine, dopamine, serotonin, glutamate, GABA 71 72  06/12/2024 Synaptic Transmission Neurotransmitters and neuromodulators 73 CHEMICAL TRANSMISSION OF SYNAPTIC ACTIVITY The final steps in the process lead to termination of the 1. Neurotransmitter - usually within the nerve terminal actions of the neurotransmitter and include diffusion and its storage within synaptic vesicles. This is followed away from the synaptic cleft , reuptake into the nerve by release of the chemical into the synaptic cleft in terminal, and enzymatic degradation. All of these response to nerve impulses. The secreted processes, plus the events in the postsynaptic neuron, neurotransmitter can then act on receptors on the are regulated by many physiologic factors and can be membrane of the postsynaptic neuron, effector organ (eg. muscle or gland), or even on the presynaptic nerve altered by drugs. terminal  06/12/2024 There are two main classes of chemical substances that serve as neurotransmitters and neuromodulators: A. Small-molecule transmitters include 1. amino acids (glutamate, GABA,glycine) 2. Neuromodulators – some chemicals released by 2. acetylcholine neurons have little or no direct effects on their own but can modify the effects of neurotransmitters. 3. monoamines (norepinephrine, epinephrine, dopamine, serotonin) 4. adenosine triphosphate (ATP) B. Large-molecule transmitters include 1. neuropeptides (substance P, enkephalin, vasopressin) Neuropeptides are colocalized with one of the small-molecule neurotransmitters Based on the direction in which they conduct action potentials, neurons split the PNS into sensory (afferent) and motor (efferent) divisions  Sensory division neurons conduct action potentials toward the CNS  Motor division neurons conduct action potentials away from the CNS. 06/12/2024