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Overview of the Nervous System: Structure, Functions, and Key Components

This chapter provides an in-depth overview of the nervous system, covering its organization into two major divisions: the Central Nervous System (CNS) and the Peripheral Nervous System (PNS). It explores the roles of neuroglia and neurons in supporting and transmitting nerve impulses. Key topics include the different subdivisions of the nervous system, types of neurons, nerve impulse transmission, and the functional anatomy of the CNS. Understand the significance of myelin, synapses, and reflex mechanisms for overall neural function.

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Overview of the Nervous System: Structure, Functions, and Key Components

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  1. Chapter 6: The Nervous System Lesson 6.1 Overview of the Nervous System

  2. Agenda & Key Points • organization of the nervous system • two major divisions • the efferent nerves-subdivisions • nervous tissues • Neuroglia-support and protection • Neurons-transmitting information (nerve impulses)

  3. Organization of the Nervous System • two major divisions • central nervous system (CNS) • peripheral nervous system (PNS) • Autonomic-(Cardiac & Smooth) • Parasympathetic-routine involuntary • Sympathetic-high alert • Somatic- (Skeletal) • sensory receptors ( special nerves- pressure, pain and temp) • afferent (sensory) nerves- From PNS to CNS • efferent (motor) nerves- From CNS to PNS

  4. Two Major Divisions

  5. The Efferent Nerves (Motor Nerves) • somatic nervous system • Voluntary • skeletal • autonomic nervous system • Involuntary • Smooth and cardiac • Sympathetic -6.4 (fight or flight) • Parasympathetic -6.4 ( rest and digest)

  6. Nervous Tissues • neuroglia • also known as glial cells • support the neurons • protect the neurons • Types: • Astrocytes- between neurons and capillaries ½ of all glials • Microglia- disposals • Ependymal cells- line, cover and protect cavities • Oligodendrocytes- produce myelin in CNS • Schwann cells- produce myelin in PNS • Satellite Cells- cushion and support

  7. Neuroglia

  8. Nervous Tissues • Neurons-transmit nerve impulses • Neuron Anatomy • Cell body-nucleus and mitochondria • Axon-sends info away from cell body • Dendrites-collect and transport stimuli • Myelin sheath-fatty insulation to increase rate on impulse transmission ( white vs gray matter) • Neurilemma-external covering of schwanncells • Nodes of ranvier-uninsulated gap between schwann cell • Synapse-gap between axon terminals and muscles or other neurons (neuromuscular junction if muscles)

  9. Neuroglia

  10. Neuron Types by Function • sensory neurons • send impulses toward CNS • motor neurons • send impulses away from CNS • interneurons • bridges between neurons

  11. Neuron Structures • bipolar • one axon and one dendrite • (eyes and nose) • unipolar • one axon • PNS • multipolar • one axon and many dendrites • CNS, Motor and interneurons

  12. Review and Assessment Match these words with 1–4 below: sympathetic nervous system, myelin, synapse, axon. 1. high alert 2. transmits impulses away from cell body 3. fatty insulating material 4. gap between neurons

  13. Chapter 6: The Nervous System Lesson 6.2 Transmission of Nerve Impulses

  14. Agenda and Key Points • Neurons are irritable too! • action potentials • change in cell membrane charge • impulse transmission • charge change travels along axon • reflexes • response to stimulus

  15. Action Potentials • Conductivity-ability to transmit nerve impulses • Polarized-difference in charge inside the cell (negative), Sodium outside, Potassium inside • Depolarized-(positive), flood of sodium ions inside • Nerveimpulse-wave of depolarization (action potential) all or none • Repolarized-return to original state • RefractoryPeriod-between impulse and repolarization (fatigue). Can’t respond

  16. Impulse Transmission • Speed of transmission: 1-119 m/s • Myelin sheath- any impulse>1m/s • Diameter of axon • Body temperature- warmer=faster • Saltatoryconduction-jump overs • Faster transmission • Nodes of Ranvier (myelin) • transmission at synapses • gap junctions • neurotransmitter • excitatory effect-acetylcholine • inhibitory effect-endorphins

  17. Reflexes • somatic • stimulate skeletal muscles, voluntary • autonomic • stimulate involuntary muscles, cardiac/smooth

  18. Chapter 6: The Nervous System Lesson 6.3 Functional Anatomy of the Central Nervous System

  19. Agenda and Key points • Brain (2.25-3.25 lb, 100 billion neurons) • Cerebrum • 2 hemispheres • diencephalon • brain stem • cerebellum • meninges • blood-brain barrier

  20. Cerebrum • cerebral cortex- outer surface=gray matter, inner= white matter • Convolutions= wrinkles • Gyrus- raises • Sulcus- grooves • Fissure- deep grooves • lobes • Frontal- • broca’s area (L) • primary motor cortex- coordination • parietal • primary somatic sensory cortex-sensory info • Occipital • vision • Temporal • Speech, hearing, vision, memory and emotion

  21. Cerebrum

  22. Diencephalon • Thalamus • Relay station • Sleep and awake • Hypothalamus • Pearl sized • Metabolism, heart rate, bp, pain and pleasure • epithalamus • Pineal gland and sleep hormones

  23. Brain Stem • Midbrain – most superior part of brain stem • Sensory and motor impulses • Vision, hearing, motor, temperature, sleep cycle • Pons- middle of brain stem • Breathing regulation • medulla oblongata- most inferior • Heart rate, blood pressure, breathing • Reflexes for cough, sneeze and vomiting • As long as the brain stem is functional, the body will live (with hydration and nutrition)

  24. The Brain • Cerebellum • Below occipital lobe • Balance and coordination, body position • blood-brain barrier • Lots of blood flow (20-25% at any given time) • Capillaries are impermeable to many substances • Water, glucose and amino acids can pass • So can alcohol, nicotine and anesthetics • Meninges- protective membranes • duramater • Tough, double layered. Inner layer extends to spinal cord • arachnoid mater • Web-like • Underneath is CSF • pia mater • Delicate. Attaches directly to brain

  25. Meninges

  26. Spinal Cord

  27. Chapter 6: The Nervous System Lesson 6.4 Functional Anatomy of the Peripheral Nervous System

  28. Functional Anatomy of the Peripheral Nervous System • nerve structure • cranial nerves • spinal nerves and nerve plexuses • autonomic nervous system

  29. Nerve Structure • endoneurium • covers axons • perineurium • bundles fascicles • epineurium • wraps nerves

  30. Cranial Nerves

  31. Spinal Nerves and Nerve Plexuses • 31 pairs • dorsal root • ventral root • dorsal ramus • ventral ramus • plexuses

  32. Autonomic Nervous System • preganglionic and postganglionic neurons • sympathetic nerves • fight-or-flight action • parasympathetic nerves • resting or digesting action

  33. Review and Assessment Match these words with 1–4 below: efferent, ganglion, optic, perineurium. 1. wraps fascicles 2. motor 3. a cranial nerve 4. enlarged junction

  34. Chapter 6: The Nervous System Lesson 6.5 Injuries and Disorders of the Nervous System

  35. Injuries to the Brain and Spinal Cord • traumatic brain injury • cerebral palsy • spinal cord injury

  36. Traumatic Brain Injury • violent impact to head • mild • moderate • severe

  37. Cerebral Palsy • damage to brain • before birth • during birth • during infancy • motor function impairment

  38. Spinal Cord Injuries • C1–C3: usually fatal • C1–C4: quadriplegia • C5–C7: paralysis of lower extremities • T1–L5: paraplegia Corepics/Shutterstock.com

  39. Common Diseases and Disorders of the CNS • meningitis • multiple sclerosis • epilepsy • Parkinson’s disease • dementia and Alzheimer’s disease

  40. Review and Assessment Match these words with 1–4 below: quadriplegia, multiple sclerosis, dementia, cerebral palsy. 1. inflammation destroys myelin sheath 2. loss of memory and thinking 3. loss of function below the neck 4. may begin before birth

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