Ppt chapter 19

Introduction to Nerves and the
Nervous System
Chapter 19
Copyright © 2013 Wolters Kluwer Health | Lippincott Williams & Wilkins

Role of the Nervous System
• Controlling the functions of the human body
• Analyzing incoming stimuli
• Integrating internal and external responses

Make Up of the Nervous System
• Central Nervous System (CNS)
– Composed of the brain and spinal cord
• Peripheral Nervous System (PNS)
– Sensory receptors bring information into the CNS
– Motor nerves carry information away from the CNS
• Autonomic Nervous System (ANS)
– Uses components of the CNS and PNS to regulate
automatic or unconscious responses to stimuli

Function of the Cells that Make Up the Nervous
System
• Allow movement
• Allow realization of various sensations
• Provide response to internal and external stimuli
• Stimulate learning, thinking, and emotions

Neuron

Types of Neuron Axons
• Afferent Fibers
– Nerve axons that run from peripheral receptors into
the CNS
• Efferent Fibers
– Nerve axons that carry nerve impulses from the CNS
to the periphery to stimulate muscles or glands

Action Potential

Electrolytes Involved in Nerve Cell Action
• Sodium
• Potassium
• Calcium

Movement of Electrolytes with Action
• Rest/Repolarization
– Membrane is impermeable to sodium
– Permeable to potassium
• Action/Depolarization
– Sodium goes into the cell
– Potassium leaves the cell

Formation of Myelin Sheath

Nerve Synapse
• Presynaptic Nerve
• Synaptic Cleft
• Postsynaptic Effector Cell

Question
What nerve axons carry nerve impulses from the central
nervous system to the peripheral nervous system?
A. Somatic axons
B. Efferent fibers
C. Afferent fibers
D. Sensory axons

Answer
B. Efferent fibers
Rationale: Efferent fibers–Nerve axons that carry nerve
impulses from the CNS to the periphery to stimulate
muscles or glands

Neurotransmitters
• Acetylcholine
– Communicates between nerves and muscles
• Norepinephrine and Epinephrine
– Catecholamines released by nerves in the
sympathetic branch of the ANS
• Dopamine
– Involved in the coordination of impulses and
responses

Neurotransmitters (cont.)
• Gamma-aminobutyric Acid (GABA)
– Inhibits nerve activity and is important in preventing
over-excitability or stimulation such as seizure
activity
• Serotonin
– Important in arousal and sleep and in preventing
depression and promoting motivation

Central Nervous System
• Made up of brain and spinal cord
• Structures are covered by meninges
• Blood brain barrier
• Blood supply to the brain

Anatomy of the Brain

Hindbrain
• Runs from the top of the spinal cord into the midbrain
• Most primitive part of the brain - contains the brainstem
• Controls basic vital functions:
– Breathing
– Blood pressure
– Swallowing
– RAS

Midbrain
• Contains the thalamus, the hypothalamus, and the limbic
system
• The thalamus sends direct information into the cerebrum to
transfer sensations
• Hypothalamus acts as major sensor activity in the body
– Temperature regulation
– Water balance
– Appetite
– Endocrine function

Limbic System
• Contains high levels of neurotransmitters
– Epinephrine
– Norepinephrine
– Serotonin
• Controls expression of emotions

Forebrain
• Made up of two cerebral hemispheres joined together by the
corpus callosum
• Receives and sends nerve impulses, coordinates speech and
communication, and facilitates learning

Spinal Cord
• Made up of 31 pairs of spinal nerves
• Each spinal nerve has two components or roots
– Sensory fiber (dorsal root)
• Brings information into the CNS from the periphery
– Motor fiber (ventral root)
• Causes movement or reaction

Function of Central Nervous System
• Sensory Functions
• Motor Functions
• Intellectual and Emotional Functions

Intellectual and Emotional Function
• Two hemispheres of the brain process information differently
• Right Side
– Artistic
• Left Side
– Analytical
• When learning takes place and actual change occurs in a
neuron

Intellectual and Emotional Function (cont.)
• Some degree of stress helps facilitate learning
• Increased stress inhibits learning
• The limbic system plays a role in learning
• Emotions associated with memory as well as the present, have
an impact on stimulus response
• The placebo effect is a documented effect of the mind on drug
therapy: If a person perceives that a drug will be effective, it is
much more likely to actually be effective

Question
Which of the following documented phenomena may occur as a
result of drug therapy?
A. Action potential
B. Placebo effect
C. Expectation effect
D. Learning

Answer
B. Placebo effect
Rationale: The placebo effect is a documented effect of the
mind on drug therapy: If a person perceives that a drug
will be effective, it is much more likely to actually be
effective.

Ppt chapter 19

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