Functions of the Nervous System Slide 7.1a Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings 1.Sensory input – gathering information  To monitor changes (stimuli) occurring inside and outside the body 2.Integration  To process and interpret sensory input and decide if action is needed 3.Motor Output  A response to the integrated stimuli  The response activates muscles or glands

Functions of the Central Nervous System (CNS) Slide 7.3b Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Figure 7.1 Example: As you’re driving you see a red light and automatically move your foot to the brake.

Structural Classification of the Nervous System Slide 7.2 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Central nervous system (CNS)  Brain  Spinal cord  Peripheral nervous system (PNS)  Nerves outside the brain (cranial) and spinal cord (spinal)

Functional Classification of the Peripheral Nervous System Slide 7.3a Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings 1.Sensory (afferent) division  Nerve fibers that carry information to the central nervous system 2.Motor (efferent) division  Nerve fibers that carry impulses away from the central nervous system Figure 7.1

Functional Classification of the Peripheral Nervous System Slide 7.3c Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Motor (efferent) division – has two subdivisions 1.Somatic nervous system  Voluntary  Allows us to control our skeletal muscles 2.Autonomic nervous system  Involuntary  Automatically controls our cardiac and smooth muscles Figure 7.1

Organization of the Nervous System Slide 7.4 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Figure 7.2

Types of Nervous Tissue Slide 7.5 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  There are only 2 types of nervous tissue: 1.Neuroglia – support cells; name means nerve glue 2.Neurons – the actual nerve cells Figure 7.3a

Neuroglia or Support Cells Slide 7.5 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  They can not transmit a nerve impulse  They never lose their ability to divide (most neurons do)  This means most brain tumors are formed by these cells (gliomas)  4 kinds of neuroglia support the CNS: astrocytes, microglia, ependymal cells, and oligodendrocytes  2 kinds of neuroglia support the PNS; Schwann cells and satellite cells Figure 7.3a

CNS Support Cells (Neuroglia) Slide 7.5 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings 1.Astrocytes  Abundant, star-shaped cells  Brace or support neurons  Form barrier between capillaries and neurons  Control the chemical environment of the brain Figure 7.3a

CNS Support Cells (Neuroglia) Slide 7.6 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings 2. Microglia  Spider-like phagocytes  Dispose of debris 3. Ependymal cells  Line cavities of the brain and spinal cord  Cilia help to circulate the cerebrospinal fluid Figure 7.3b, c

CNS Support Cells (Neuroglia) Slide 7.7a Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings 4. Oligodendrocytes  Produce myelin sheath (a fatty layer of insulation) around nerve fibers in the central nervous system Figure 7.3d

PNS Support Cells (Neuroglia) Slide 7.7b Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings 1. Satellite cells  Protect neuron cell bodies 2. Schwann cells  Form myelin sheath in the peripheral nervous system Figure 7.3e

Nervous Tissue: Neurons Slide 7.8 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Neurons = nerve cells  Cells specialized to transmit messages  All neurons have a:  Cell body – nucleus and metabolic center of the cell  Processes – fibers that extend from the cell body

Neuron Anatomy Slide 7.10 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Cell body & extensions outside the cell body  Dendrites – conduct impulses toward the cell body  Axons – conduct impulses away from the cell body Figure 7.4a

Axons and Nerve Impulses Slide 7.11 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  One axon ends in many axonal terminals (hundreds to thousands)  Axonal terminals contain hundreds of tiny vesicles with neurotransmitters  Axonal terminals are separated from the next neuron by a gap  This gap is called the synaptic cleft or synapse

Neuron Anatomy Slide 7.10 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Most long neurons are covered with myelin (white, fatty substance)  This forms the myelin sheath  In the PNS, Schwann cells form it while in the CNS, oligodendrocytes form it  In the CNS, myelinated neurons are called the white matter and unmyelinated neurons are called the gray matter Figure 7.4a

Multiple Sclerosis Slide 7.10 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  In this disease, the myelin sheath is slowly destroyed and hardened (called scleroses)  This short circuits the nerve transmissions and the person loses the ability to control muscles  It’s an autoimmune disease which means the body attacks the protein in the sheath for some unknown reason  There’s no cure but it’s treated with interferon and bovine myelin Figure 7.4a

Classification of Neurons Slide 7.14a Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Can classify neurons by their function: 1.Sensory (afferent) neurons – toward CNS 2.Motor (efferent) neurons – away from CNS 3.Interneurons (association) neurons – connect sensory & motor neurons

Neuron Classification Slide 7.15 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Figure 7.6

Classification of Neurons Slide 7.14a Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Can classify neurons by their structure or number of processes they have: 1.Multipolar neurons– many extensions; by far the most common 2.Bipolar neurons – 2 extensions 3.Unipolar neurons – 1 extension

Structural Classification of Neurons Slide 7.16a Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

2 Functional Properties of Neurons Slide 7.17 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings 1.Irritability – ability to respond to stimuli and convert it to an impulse 2.Conductivity – ability to transmit an impulse to other neurons, muscles or glands

Starting a Nerve Impulse Slide 7.18 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings 1.Polarized membrane – at rest a neuron has fewer + ions inside than outside = no activity 2.Depolarization – a stimulus depolarizes the neuron’s membrane which allows sodium (Na + ) to flow inside the membrane Figure 7.9a–c

Starting a Nerve Impulse Slide 7.18 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings 3. The build up of + sodium ions inside initiates an action potential in the neuron = nerve impulse 4. The nerve impulse is all or none – it travels down the entire axon 5. Repolarization – almost immediately the extra + ions are moved back out of the neuron and it becomes polarized again Figure 7.9a–c

Nerve Impulse Propagation Slide 7.20 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Impulses travel faster when fibers have a myelin sheath  Impulses cross the synapse to the next neuron by release of a neurotransmitter Figure 7.9c–e

How Neurons Communicate at Synapses Slide 7.22 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Figure 7.10

Things that affect the conduction of impulses Slide 7.22 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Alcohol, sedatives and anesthetics all block nerve impulses by not allowing sodium into the neuron.  No sodium means no action potential or nerve impulse  Cold and continuous pressure also impair nerve impulses because they disrupt blood flow  Examples: can’t write your name if hands are cold or your foot “falling asleep” Figure 7.10

The Reflexes Slide 7.23 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Reflex – rapid, predictable, and involuntary responses to stimuli  Reflex – like a one way street; always go the same direction  Reflex arc – direct route from a sensory neuron, to an interneuron, to an effector Figure 7.11a

Simple Reflex Arc Slide 7.24 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Figure 7.11b, c

Types of Reflexes Slide 7.25 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings 1.Autonomic reflexes  Regulates smooth & cardiac muscle plus glands  Regulates body functions: digestion, elimination, blood pressure & sweating  Also includes salivating & pupil dilation 2.Somatic reflexes  Involves the skeletal muscles – pulling away from a hot object