10.1_Nervous-system-part-1

Chapter 7: The Nervous System

Overview

• Copyright © 2003 Pearson Education, Inc. - Benjamin Cummings

• Author: Elaine N. Marieb

Functions of the Nervous System

• Sensory Input

  • Gathers information from internal and external environments

  • Changes in the environment are known as stimuli

• Integration

  • Processes and interprets sensory input, determining if action is needed

• Motor Output

  • A response to integrated stimuli, activating muscles or glands

Structural Classification of the Nervous System

• Central Nervous System (CNS)

  • Comprises the brain and spinal cord

• Peripheral Nervous System (PNS)

  • Consists of nerves outside the brain and spinal cord

Functional Classification of the PNS

• Sensory (Afferent) Division

  • Carries information to the CNS

• Motor (Efferent) Division

  • Carries impulses away from the CNS

  • Subdivisions of the Motor Division:

    • Somatic Nervous System: voluntary control

    • Autonomic Nervous System: involuntary control

Nervous Tissue

• Principal Cells:

  • Supporting Cells (Neuroglia):

    • CNS: Astrocytes, Microglial cells, Ependymal cells, Oligodendrocytes

    • PNS: Satellite cells, Schwann cells

  • Neurons: specialized for transmitting messages

Supporting Cells (Neuroglia)

• Astrocytes

  • Star-shaped, brace neurons, form blood-brain barrier

• Microglia

  • Phagocytes that dispose of debris

• Ependymal Cells

  • Line brain and spinal cord cavities, circulate cerebrospinal fluid

• Oligodendrocytes

  • Produce myelin sheath around CNS nerve fibers

• Satellite Cells

  • Protect neuron cell bodies in PNS

• Schwann Cells

  • Form myelin sheath in PNS

Neuron Anatomy

• Major Regions of Neurons:

  • Cell Body: contains nucleus, metabolic center

  • Processes: Fiber extensions from the cell body

  • Dendrites: conduct impulses toward cell body

  • Axons: conduct impulses away from cell body

  • Axonal Terminals: contain neurotransmitter vesicles

Nerve Impulse

• Action Potential:

  • Depolarization initiates an action potential when sodium ions flood in

  • Propagated along axon when the membrane is repolarized by potassium ions exiting

  • Requires ATP to restore the resting state via the sodium-potassium pump

Neuron Communication

• Synapse:

  • Junction between neurons

  • Neurotransmitters released from axon terminals spark action potential in next neuron

Reflex Arc

• Definitions:

  • Reflex: rapid, predictable, involuntary response to stimuli

  • Reflex Arc: direct route from sensory neuron to interneuron to effector

• Types of Reflexes:

  • Autonomic Reflexes: regulate functions such as heart rate, blood pressure

  • Somatic Reflexes: activate skeletal muscles

Central Nervous System Development

• Develops from embryonic neural tube into brain and spinal cord

• Contains ventricles filled with cerebrospinal fluid

Regions of the Brain

• Divided into four main parts:

  • Cerebral Hemispheres

  • Diencephalon

  • Brain Stem

  • Cerebellum

Cerebral Hemispheres

• Superior parts of the brain consisting of:

  • Gyri (ridges) and Sulci (grooves)

  • Divided into lobes: Frontal, Parietal, Occipital, Temporal

Specialized Areas of the Cerebrum

• Sensory Areas: for various senses (taste, vision, hearing, smell)

• Motor Areas: primary motor area sends impulses to skeletal muscles

• Interpretation Areas: for speech, language, and sensory integration

Thalamus

• Relay station for sensory impulses to correct parts of the cortex for localization and interpretation

• Regulates emotional and visceral activities through inputs from the hypothalamus

Hypothalamus

• Under the thalamus, regulates autonomic functions (temperature, water balance, metabolism)

• Part of the limbic system affecting emotions

Epithalamus

• Forms the roof of the third ventricle housing the pineal gland (endocrine function) and choroid plexus (cerebrospinal fluid production)

Brain Stem

• Connects to spinal cord; comprises midbrain, pons, medulla oblongata

• Essential for autonomic functions like heart rate, breathing, and swallowing

Medulla Oblongata

• Lowest part of brain stem; vital control centers for heart rate, blood pressure, and breathing

Reticular Formation

• Mass of gray matter along brain stem; involved in visceral motor control and consciousness regulation