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Nervous System Part I

Nervous System Part I. Chapters 12, 13, 14. 10.00 Describe the control and coordination of body function, including the anatomy, function and physiology of the nervous system. 10.01 Identify the general functions of the nervous system.

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Nervous System Part I

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  1. Nervous System Part I Chapters 12, 13, 14

  2. 10.00 Describe the control and coordination of body function, including the anatomy, function and physiology of the nervous system. • 10.01 Identify the general functions of the nervous system. • 10.02 Explain the organization of the nervous system including the structure and functional classifications. • 10.03 Differentiate between the Central Nervous System (CNS) and the Peripheral Nervous System (PNS) both anatomically and functionally. • 10.04 Describe the conduction of nervous impulses over the neuron and across synapses.

  3. Functions of the Nervous Systems • The sensory function of the nervous system is to sense changes in the internal and external environment through sensory receptors. • Sensory (afferent) neurons serve this function. • The integrative function is to analyze the sensory information, store some aspects, and make decisions regarding appropriate behaviors. • Association or interneurons serve this function. • The motor function is to respond to stimuli by initiating action. • Motor(efferent) neurons serve this function. Principles of Human Anatomy and Physiology, 11e

  4. Nervous System Divisions • Central nervous system (CNS) • consists of the brain and spinal cord • Peripheral nervous system (PNS) • consists of cranial and spinal nerves that contain both sensory and motor fibers • connects CNS to muscles, glands & all sensory receptors Principles of Human Anatomy and Physiology, 11e

  5. Organization of the Nervous System • CNS is brain and spinal cord • PNS is everything else Principles of Human Anatomy and Physiology, 11e

  6. Parts of a Neuron Neuroglial cells Nucleus with Nucleolus Axons or Dendrites Cell body Principles of Human Anatomy and Physiology, 11e

  7. Dendrites: • Conducts impulses towards the cell body • Typically short, highly branched & unmyelinated • Surfaces specialized for contact with other neurons • Axons: • Conduct impulses away from cell body • Long, thin cylindrical process of cell • Swollen tips called synaptic end bulbs contain vesicles filled with neurotransmitters

  8. Electrical Signals in Neurons • Neurons are electrically excitable due to the voltage difference across their membrane • Communicate with 2 types of electric signals • action potentials that can travel long distances • graded potentials that are local membrane changes only • In living cells, a flow of ions occurs through ion channels in the cell membrane Principles of Human Anatomy and Physiology, 11e

  9. Gated Ion Channels Principles of Human Anatomy and Physiology, 11e

  10. Action Potential • Series of rapidly occurring events that change and then restore the membrane potential of a cell to its resting state • Ion channels open, Na+ rushes in (depolarization), K+ rushes out (repolarization) • All-or-none principal = with stimulation, either happens one specific way or not at all (lasts 1/1000 of a second) • Travels (spreads) over surface of cell without dying out Principles of Human Anatomy and Physiology, 11e

  11. The Action Potential: Summarized • Resting membrane potential is -70mV • Depolarization is the change from -70mV to +30 mV • Repolarization is the reversal from +30 mV back to -70 mV) Principles of Human Anatomy and Physiology, 11e

  12. Chemical Synapses • Action potential reaches end bulb and voltage-gated Ca+ 2 channels open • Ca+2 flows inward triggering release of neurotransmitter • Neurotransmitter crosses synaptic cleft & binding to ligand-gated receptors • the more neurotransmitter released the greater the change in potential of the postsynaptic cell • Synaptic delay is 0.5 msec • One-way information transfer Principles of Human Anatomy and Physiology, 11e

  13. Part Two 10.05 Describe the structure and function of the brain. 10.06 Describe the structure and function of the meninges. 10.07 Describe the structure and functions of the spinal cord. 10.08 Describe the function of cerebrospinal fluid including its production, site and flow. 10.09 Discuss the structure and function of cranial nerves and spinal nerves. 10.10 Describe a reflex arc. 10.11 Explain the autonomic nervous system including the anatomy and function of its components.

  14. Chapter 14The Brain and Cranial Nerves • Largest organ in the body at almost 3 lb. • Brain functions in sensations, memory, emotions, decision making, behavior Principles of Human Anatomy and Physiology, 11e

  15. Principal Parts of the Brain • Cerebrum • Diencephalon • thalamus & hypothalamus • Cerebellum • Brainstem • medulla, pons & midbrain Principles of Human Anatomy and Physiology, 11e

  16. Medulla Oblongata Brainstem • Continuation of spinal cord • Cardiovascular center • force & rate of heart beat • diameter of blood vessels • Respiratory center • sets basic rhythm of breathing • Information in & out of cerebellum • Reflex centers for coughing, sneezing, swallowing etc. Pons • One inch long • Pneumotaxic & apneustic areas help control breathing Midbrain • One inch in length • Extends from pons to diencephalon Principles of Human Anatomy and Physiology, 11e

  17. Cerebellum • 2 cerebellar hemispheres and vermis (central area) • Function • correct voluntary muscle contraction and posture based on sensory data from body about actual movements • sense of equilibrium Principles of Human Anatomy and Physiology, 11e

  18. Thalamus Hypothalamus • 1 inch long mass of gray mater in each half of brain (connected across the 3rd ventricle by intermediate mass) • Relay station for sensory information on way to cortex • Crude perception of some sensations • Dozen or so nuclei in 4 major regions • mammillary bodies are relay station for olfactory reflexes;infundibulum suspends the pituitary gland • Major regulator of homeostasis • receives somatic and visceral input, taste, smell & hearing information; monitors osmotic pressure, temperature of blood Principles of Human Anatomy and Physiology, 11e

  19. Cerebrum (Cerebral Hemispheres) • Cerebral cortex is gray matteroverlying white matter • 2-4 mm thick containing billions of cells • Longitudinal fissure separates left & right cerebral hemispheres • Corpus callosum is a commisure (band of white matter) connecting left and right cerebral hemispheres • Each hemisphere is subdivided into 4 lobes Principles of Human Anatomy and Physiology, 11e

  20. Meninges • The meninges are three coverings that run continuously around the spinal cord and brain (Figures 13.1a, 14.4a). • The outermost layer is the dura mater. • The middle layer is the arachnoid. • The innermost meninx is the pia mater, a thin, transparent connective tissue layer that adheres to the surface of the spinal cord and brain • Denticulate ligaments are thickenings of the pia mater that suspend the spinal cord in the middle of its dural sheath. Principles of Human Anatomy and Physiology, 11e

  21. Chapter 13The Spinal Cord & Spinal Nerves • Together with brain forms the CNS • Functions • spinal cord reflexes • integration (summation of inhibitory and excitatory) nerve impulses • highway for upward and downward travel of sensory and motor information Principles of Human Anatomy and Physiology, 11e

  22. Spinal Cord & Spinal Nerves • Spinal nerves begin as roots • Dorsal or posterior root is incoming sensory fibers • dorsal root ganglion (swelling) = cell bodies of sensory nerves • Ventral or anterior root is outgoing motor fibers Principles of Human Anatomy and Physiology, 11e

  23. SPINAL CORD PHYSIOLOGY • The spinal cord has two principal functions. • The white matter tracts are highways for nerve impulse conduction to and from the brain. • The gray matter receives and integrates incoming and outgoing information. Principles of Human Anatomy and Physiology, 11e

  24. Reflex Arc • Specific nerve impulse pathway • 5 components of reflex arc • receptor • sensory neuron • integrating center • motor neuron • effector Principles of Human Anatomy and Physiology, 11e

  25. Illustration of the Stretch Reflex Principles of Human Anatomy and Physiology, 11e

  26. Cerebrospinal Fluid (CSF) • 80-150 ml (3-5oz) • Clear liquid containing glucose, proteins, & ions • Functions • mechanical protection • floats brain & softens impact with bony walls • chemical protection • optimal ionic concentrations for action potentials • circulation • nutrients and waste products to and from bloodstream Principles of Human Anatomy and Physiology, 11e

  27. Origin of the CSF: Choroid plexus There are four CSF filled cavities called ventricles

  28. Chapter 15 The Autonomic Nervous System • Regulate activity of smooth muscle, cardiac muscle & certain glands • Structures involved • general visceral afferent neurons • general visceral efferent neurons • integration center within the brain • Receives input from limbic system and other regions of the cerebrum Principles of Human Anatomy and Physiology, 11e

  29. INTRODUCTION • The autonomic nervous system (ANS) operates via reflex arcs. • Operation of the ANS to maintain homeostasis, however, depends on a continual flow of sensory input, from receptors in organs, and motor output to the same effector organs. • Structurally, the ANS includes autonomic sensory neurons, integrating centers in the CNS, and autonomic motor neurons. • Functionally, the ANS usually operates without conscious control. • The ANS is regulated by the hypothalamus and brain stem. Principles of Human Anatomy and Physiology, 11e

  30. Somatic versus Autonomic NS Principles of Human Anatomy and Physiology, 11e

  31. SOMATIC vs AUTONOMIC NERVOUS SYSTEMS • All somatic motor pathways consist of a single motor neuron • Autonomic motor pathways consists of two motor neurons in series • The first autonomic neuron motor has its cell body in the CNS and its myelinated axon extends to an autonomic ganglion. • It may extend to the adrenal medullae rather than an autonomic ganglion • The second autonomic motor neuron has its cell body in an autonomic ganglion; its nonmyelinated axon extends to an effector. Principles of Human Anatomy and Physiology, 11e

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