The Human Body in Health and Illness 4
The Human Body in Health and Illness, 4 th edition Barbara Herlihy Chapter 10: Nervous System: Nervous Tissue and Brain 1
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
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
Functions of the Nervous System Copyright © 2011, 2007 by Saunders, an imprint of Elsevier Inc. All rights reserved. 4
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
Neuroglia • • • Astrocytes Ependymal cells Microglia Schwann cells Oligodendrocytes Copyright © 2011, 2007 by Saunders, an imprint of Elsevier Inc. All rights reserved. 6
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
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
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
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
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
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
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
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
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
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
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
Cerebrum: Markings • Gyrus (convolution) • Fissures (sulci) – Central – Lateral – Longitudinal Copyright © 2011, 2007 by Saunders, an imprint of Elsevier Inc. All rights reserved. 18
Frontal Lobe • • “ The executive” Behavior Personality Motor control Copyright © 2011, 2007 by Saunders, an imprint of Elsevier Inc. All rights reserved. 19
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
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
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
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
Diencephalon • Thalamus • Hypothalamus Copyright © 2011, 2007 by Saunders, an imprint of Elsevier Inc. All rights reserved. 24
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
Cerebellum • Mediates reflexes • Coordinates motor activity • Evaluates sensory input Copyright © 2011, 2007 by Saunders, an imprint of Elsevier Inc. All rights reserved. 26
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
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
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
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
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
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
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