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