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

Functions of the Nervous System Copyright © 2011, 2007 by Saunders, an imprint of

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,

Parts of a Neuron • Cell body • Dendrites • Axon – Myelin sheath

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

Cerebrum: Four Lobes • • Frontal lobe Parietal lobe Temporal lobe Occipital lobe Copyright

Cerebrum: Markings • Gyrus (convolution) • Fissures (sulci) – Central – Lateral – Longitudinal

Frontal Lobe • • “ The executive” Behavior Personality Motor control Copyright © 2011,

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

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

Brain Stem • Midbrain • Pons • Medulla oblongata • Vital center • Emetic

Cerebellum • Mediates reflexes • Coordinates motor activity • Evaluates sensory input Copyright ©

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

Protecting the CNS: Meninges • Dura mater • Arachnoid mater – Subarachnoid space •

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