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  • The nervous system coordinates and directs the various organ systems of the body.
    The central nervous system includes the brain and the spinal cord.
    The peripheral nervous system consists of the nerves that connect the CNS with the rest of the body. It is located outside the CNS.
  • The sensory nerves gather information and carry it to the CNS.
    The integrative function serves to process or interpret the information brought to the CNS by the sensory nerves.
    The motor nerves convey information from the CNS to the muscles and glands to carry out the plans made by the CNS.
    Ask students to give some example of what an integrative function could be.
    Possible answers include interpreting sensory information and making a decision about what should be done.
  • Only two of the five types of glial cells are shown on the slide.
    The astrocytes form the blood-brain barrier and will be discussed as part of that topic.
    Ependymal cells help form cerebrospinal fluid (CSF).
    Insert functions of each type of cell.
  • The neuron is the second type of nerve cell and is the most important in the transmission of information.
    Neurons have many shapes and sizes. They are also nonmitotic and therefore do not replicate or replace themselves when injured.
    Ask students to identify the parts of the neuron on the slide.
    The electrical signal travels from the cell body down toward the axon terminal, as the arrow illustrates.
  • Sensory neurons are also called afferent neurons. They carry information from the periphery toward the CNS.
    Motor neurons, also called efferent neurons, carry information from the CNS toward the periphery.
    Both sensory neurons and motor neurons are found in the CNS and in the peripheral nervous system.
    Interneurons are found only in the CNS. They form connections between sensory and motor neurons.
  • Polarization: The inside of the neuron is more negative than the outside when it is polarized.
    Depolarization: This is the change inside the cell from negative to positive when the neuron is stimulated.
    Repolarization: The inside of the cell becomes negative again.
  • The movement of specific ions across the cell membrane of the neuron is responsible for the action potential, or nerve impulse.
    During the resting state, the potassium ions tend to leak out of the cell, taking the positive charge with them. This leakage is responsible for the resting membrane potential.
    The inward diffusion of sodium ions causes depolarization.
    The outward diffusion of potassium causes repolarization, returning the cell to a resting state.
  • The terms nerve impulse and action potential mean the same thing.
    A nerve impulse (or action potential) must move the length of the neuron.
    As illustrated in Figure 10-7, each nerve impulse (or action potential) has the ability to depolarize the adjacent membrane. This causes the nerve impulse to move toward the axon like a wave.
    The height of each nerve impulse is the same along the entire length of the axon. This ensures that the nerve impulse does not weaken as it travels the length of a long axon.
    The action potential is responsible for the release of neurotransmitter.
  • The action potential jumps from node to node to the axon terminal.
    The jumping kangaroo effect increases the speed of the action potential.
    The jumping of the action potential is also called saltatory conduction.
    Myelinated fibers are therefore fast conducting fibers.
    Why is the image of the kangaroo jumping appropriate when talking about myelinated fiber, but inappropriate when discussing nonmyelinated fibers?
    The action potential cannot form on a nonmyelinated area, so it has to jump from node to node.
  • Nerves must communicate with one another; they do so at the synapse.
    In the upper panel, the boxed area shows the communication at the synapse. The lower panel shows the steps
    How does communication across the synapse resemble communication at the neuromuscular junction (Chapter 9)?
    Both have the same steps, but the neurotransmitters may vary.
  • The brain is located in the cranial cavity and is pinkish-gray, is delicate, has a soft consistency, and is divided into four major areas.
    The primary source of energy for the brain is glucose.
  • The cerebrum is the largest part of the brain and is divided into the right and left cerebral hemispheres.
    The corpus callosum, bands of white matter that form a large fiber tract, joins the two hemispheres and allows them to communicate with each other.
    Each cerebral hemisphere has four major lobes that are named for the overlying cranial bones.
  • The gyri (singular, gyrus), or convolutions, looks like speed bumps on the surface of the brain. By increasing surface area, they increase the amount of tissue available for thinking.
    Fissures or sulci are grooves that separate the gyri. Of particular interest is the central sulcus, which separates the frontal lobe from the parietal lobe; it is an important landmark.
    Ask students to examine Figure 10-11A. In what cerebral lobe is the precentral gyrus found? In what cerebral lobe is the postcentral gyrus found?
    The precentral gyrus is found in the frontal lobe and the postcentral gyrus in found in the parietal lobe.
  • Most frontal lobe functions are associated with higher order intellectual functioning and motor activity.
    What do you think might happen to a person who has sustained a severe injury to the frontal lobe?
    Answers will include difficulty with memory, changes in personality and behavior, and impairment of intellectual and motor functioning. For example, a person might need to relearn reading.
  • If a person suffers a stroke involving Broca’s area, why may she understand what you are saying but be unable to respond verbally?
    The motor speech area (Broca’s area) deals with the physical aspects of producing speech, not cognitive issues such as understanding the meanings of words.
  • The homunculus represents the amount of brain tissue that corresponds to a motor function of a particular body part.
    Each part of the body is controlled by a specific area of the primary motor cortex of the precentral gyrus. Complicated movements require large amounts of brain tissue.
    Ask students to compare the size of the homunculus’s hands and feet. Why are the hands bigger than the feet?
    The hand performs more complex movements that require more brain tissue.
    One could also draw a similar homunculus on the postcentral gyrus to illustrate sensory function.
  • The parietal lobe contains the somatosensory area. This area interprets temperature, pain, pressure, light touch, and proprioception.
    The temporal lobe contains the auditory cortex and the olfactory area. Information from the taste buds is interpreted in both the temporal and parietal lobes.
    The occipital lobe contains the visual cortex.
  • Wernicke’s area is located in both the temporal and parietal lobes and is responsible for translating thought into words.
    Explain why injury to the left hemisphere is much more likely to result in speech impairment than injury to the right hemisphere?
    In most people, the speech centers are concentrated in the left hemisphere.
    The primary visual cortex allows you to see an imagefor example, a tree. What additional information does the visual association area provide?
    The visual association area allows you to interpret or apply meaning to the image, perhaps that it is an oak tree or that it needs water.
  • There are two parts of the diencephalon, the thalamus and the hypothalamus.
    The thalamus acts as a sensory pathway for information coming from the lower brain and the spinal cord to the sensory areas of the cerebrum. It is especially important with regard to pain sensation.
    The hypothalamus sits above the pituitary gland and controls endocrine function. It is also the body’s thermostat and helps regulate autonomic functions.
  • The midbrain contains nuclei that serve as reflex centers for vision and hearing.
    The pons plays an important role in regulating breathing rate and rhythm.
    The medulla oblongata descends through the foramen magnum as the spinal cord. It is called the vital center because it controls heart rate, blood pressure, and respiration. Its emetic center stimulates vomiting, either as a result of direct stimulation (e.g., fear, spinning, or distressing odors) or from indirect stimulation from the chemoreceptor trigger zone (CTZ), as in cancer chemotherapy.
  • The primary responsibility of the cerebellum is the coordination of voluntary muscle activity. It produces a smooth, coordinated muscle response after integrating all the incoming information from many areas throughout the body.
    It is also a major reflex center.
  • These three important structures are not confined to any one division of the brain. They overlap several areas.
    The limbic system is a wishbone-shaped group formed by parts of the cerebrum and diencephalon.
    The reticular formation is responsible for maintaining consciousness and activating the sleep-wake cycle. It also contains the gaze center.
    The memory areas allow the recollection of thoughts and images. Many areas of the brain are responsible for memory.
  • The cranium and the vertebral column help protect the central nervous system.
  • The pia mater, the innermost layer, is a very thin membrane containing many blood vessels.
    The arachnoid layer is a spider web–like membrane between the pia mater and dura mater. The subarachnoid space surrounds the entire CNS and is filled with cerebrospinal fluid (CSF) to cushion the CNS.
    The dura mater is a thick, tough, connective tissue that splits into sinuses filled with blood. The subdural space is located beneath the dura mater; it contains blood.
    Clinical application: A person sustains a sharp blow to the head and develops a subdural hematoma. Predict some possible symptoms.
    Because the cranium cannot expand, a subdural hematoma causes pressure on the brain. The precise symptoms depend on the location of the pressure but might include a dragging foot, blurred vision, slurred speech, or decreased level of consciousness.
  • Identify these structures on the slide: two lateral ventricles, one third ventricle, one fourth ventricle, and cerebral aqueduct.
    Cerebrospinal fluid (CSF) is formed within the ventricles of the brain by the choroid plexus (the ependymal cells). CSF is a clear fluid and is similar in consistency to plasma.
    Some of the CSF flows through the central canal, which is a hole in the center of the spinal cord. It eventually drains into the subarachnoid space at the base of the spinal cord. A second drainage path is through foramina near the brain.
  • The amount of CSF drained must equal the amount produced.
    What if the canal between the third and fourth ventricles is blocked, perhaps by a congenital malformation?
    The CSF would accumulate in the ventricles, increasing intracranial pressure and pressing on brain tissue. Treatment could include shunting the CSF around the blockage.
  • Glial astrocytes are parts of the cerebral blood vessel (capillary) wall that supplies the brain and spinal cord. The astrocytes select the substances allowed to enter the CNS from the blood.
    Some antibiotics cannot cross the blood-brain barrier. How, then, could an infection of the CNS be treated?
    The infection could be treated either by selecting an antibiotic that does cross the blood-brain barrier or injecting the antibiotic into the subarachnoid space.

Transcript

  • 1. The Human Body in Health and Illness, 4th edition Barbara Herlihy Chapter 10: Nervous System: Nervous Tissue and Brain 1
  • 2. Lesson 10-1 Objectives • Define the two divisions of the nervous system. • List three functions of the nervous system. • Compare the neuroglia and neuron. • Explain the function of the myelin sheath. • Explain how a neuron transmits information. • Describe the structure and function of a synapse. Copyright © 2011, 2007 by Saunders, an imprint of Elsevier Inc. All rights reserved. 2
  • 3. Divisions of the Nervous System • Central nervous system (CNS) • Peripheral nervous system Copyright © 2011, 2007 by Saunders, an imprint of Elsevier Inc. All rights reserved. 3
  • 4. Functions of the Nervous System Copyright © 2011, 2007 by Saunders, an imprint of Elsevier Inc. All rights reserved. 4
  • 5. Types of Nervous Tissue • Neuroglia or glia – Most abundant type – Support, protect, insulate, nourish, and generally care for neurons • Neurons – Do the communicating for the nervous system – Long shape makes them delicate Copyright © 2011, 2007 by Saunders, an imprint of Elsevier Inc. All rights reserved. 5
  • 6. Neuroglia • • • • • Astrocytes Ependymal cells Microglia Schwann cells Oligodendrocytes Copyright © 2011, 2007 by Saunders, an imprint of Elsevier Inc. All rights reserved. 6
  • 7. Parts of a Neuron • Cell body • Dendrites • Axon – Myelin sheath – Nodes of Ranvier – Neurilemma – Axon terminal Copyright © 2011, 2007 by Saunders, an imprint of Elsevier Inc. All rights reserved. 7
  • 8. Types of Neurons • Sensory (afferent) neurons – Carry information from periphery toward the CNS • Motor (efferent) neurons – Carry information from CNS toward periphery • Interneurons – Found only in CNS; connect sensory and motor nerves Copyright © 2011, 2007 by Saunders, an imprint of Elsevier Inc. All rights reserved. 8
  • 9. Nerve Impulses or Signals • Electrical signals convey information along a neuron • Also called action potential • Move along sensory or motor neurons Copyright © 2011, 2007 by Saunders, an imprint of Elsevier Inc. All rights reserved. 9
  • 10. The Action Potential • Polarization: Resting state • Depolarization: Stimulated state • Repolarization: Return to resting Copyright © 2011, 2007 by Saunders, an imprint of Elsevier Inc. All rights reserved. 10
  • 11. Ionic Basis of the Action Potential • Polarization – K+ leaks from neuron. – Determines resting membrane potential • Depolarization – Na+ rushes in. • Repolarization – K+ rushes out. Copyright © 2011, 2007 by Saunders, an imprint of Elsevier Inc. All rights reserved. 11
  • 12. Why Action Potential “Moves” • Action potential – Forms at axon’s beginning – Regenerates along axon’s length – Enters axon terminal – Releases ACh from vesicles Copyright © 2011, 2007 by Saunders, an imprint of Elsevier Inc. All rights reserved. 12
  • 13. Increasing Action Potential’s Speed • Myelin insulates axon. • Myelin exposes some axonal membrane— nodes of Ranvier. • Action potentials jump quickly from node to node, like a kangaroo. Copyright © 2011, 2007 by Saunders, an imprint of Elsevier Inc. All rights reserved. 13
  • 14. Communication across the Synapse • ACh is – Secreted from neuron A – Diffused across synaptic cleft – Bound to receptors on neuron B • Neuron B is activated. Copyright © 2011, 2007 by Saunders, an imprint of Elsevier Inc. All rights reserved. 14
  • 15. Lesson 10-2 Objectives • Describe the four major areas of the brain. • Describe the functions of the four lobes of the cerebrum. • Describe how the skull, meninges, cerebrospinal fluid, and blood-brain barrier protect the central nervous system. Copyright © 2011, 2007 by Saunders, an imprint of Elsevier Inc. All rights reserved. 15
  • 16. Four Major Areas of the Brain • • • • Cerebrum Diencephalon Brain stem Cerebellum Copyright © 2011, 2007 by Saunders, an imprint of Elsevier Inc. All rights reserved. 16
  • 17. Cerebrum: Four Lobes • • • • Frontal lobe Parietal lobe Temporal lobe Occipital lobe Copyright © 2011, 2007 by Saunders, an imprint of Elsevier Inc. All rights reserved. 17
  • 18. Cerebrum: Markings • Gyrus (convolution) • Fissures (sulci) – Central – Lateral – Longitudinal Copyright © 2011, 2007 by Saunders, an imprint of Elsevier Inc. All rights reserved. 18
  • 19. Frontal Lobe • • • • “ The executive” Behavior Personality Motor control Copyright © 2011, 2007 by Saunders, an imprint of Elsevier Inc. All rights reserved. 19
  • 20. Frontal Lobe: Motor Activity • Primary motor area – Precentral gyrus • Frontal eye field • Motor speech area – Broca’s area Copyright © 2011, 2007 by Saunders, an imprint of Elsevier Inc. All rights reserved. 20
  • 21. Frontal Lobe: Motor Homunculus • Shows percentages of frontal lobe devoted to body’s motor activities Copyright © 2011, 2007 by Saunders, an imprint of Elsevier Inc. All rights reserved. 21
  • 22. Other Cerebral Lobes • Parietal – Somatosensory area – Gustatory area • Temporal – Auditory cortex – Gustatory area – Olfactory area • Occipital – Visual cortex Copyright © 2011, 2007 by Saunders, an imprint of Elsevier Inc. All rights reserved. 22
  • 23. Functions Spanning Cerebral Lobes • Speech areas – Span temporal, parietal and occipital lobes – Usually in left hemisphere – Wernicke’s area (helps translate thought into speech) • Association areas – Helps to interpret sensory information – Examples: Visual, auditory, somatosensory Copyright © 2011, 2007 by Saunders, an imprint of Elsevier Inc. All rights reserved. 23
  • 24. Diencephalon • Thalamus • Hypothalamus Copyright © 2011, 2007 by Saunders, an imprint of Elsevier Inc. All rights reserved. 24
  • 25. Brain Stem • Midbrain • Pons • Medulla oblongata • Vital center • Emetic center • Reflex center Copyright © 2011, 2007 by Saunders, an imprint of Elsevier Inc. All rights reserved. 25
  • 26. Cerebellum • Mediates reflexes • Coordinates motor activity • Evaluates sensory input Copyright © 2011, 2007 by Saunders, an imprint of Elsevier Inc. All rights reserved. 26
  • 27. Structures Spanning Brain Divisions • Limbic system – Emotional brain • Reticular formation: Reticular activating system; sleep-wake cycle, consciousness, gaze center • Memory areas – Immediate memory – Short-term memory – Long-term memory Copyright © 2011, 2007 by Saunders, an imprint of Elsevier Inc. All rights reserved. 27
  • 28. Protecting the CNS: Four Layers • • • • Bone Meninges Cerebrospinal fluid Blood-brain barrier Copyright © 2011, 2007 by Saunders, an imprint of Elsevier Inc. All rights reserved. 28
  • 29. Protecting the CNS: Meninges • Dura mater • Arachnoid mater – Subarachnoid space • Pia mater Copyright © 2011, 2007 by Saunders, an imprint of Elsevier Inc. All rights reserved. 29
  • 30. Protecting the CNS: Cerebrospinal Fluid (CSF) • Formed in ventricles by choroid plexus • Circulates through subarachnoid space – From central canal of spinal cord – From foramina Copyright © 2011, 2007 by Saunders, an imprint of Elsevier Inc. All rights reserved. 30
  • 31. Drainage of CSF • Drainage of CSF must equal its production. • Arachnoid villi project into dural sinuses filled with blood. • CSF drains into blood and leaves the brain. Copyright © 2011, 2007 by Saunders, an imprint of Elsevier Inc. All rights reserved. 31
  • 32. Protecting the CNS: The Blood-Brain Barrier • Made of special cells (astrocytes) within cerebral capillaries. • Prevents some toxins from entering CNS from blood Copyright © 2011, 2007 by Saunders, an imprint of Elsevier Inc. All rights reserved. 32