Neural Tissue

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Chapter 12: Neural Tissue - An Introduction to the Nervous System Learning Outcomes
12-1 Describe the anatomical and functional divisions of the nervous system. 12-2 Sketch and label the structure of a typical neuron, describe the functions of each component, and classify neurons on the basis of their structure and function. 12-3 Describe the locations and functions of the various types of neuroglia. 12-4 Explain how the resting potential is created and maintained. 12-5 Describe the events involved in the generation and propagation of an action potential. 12-6 Discuss the factors that affect the speed with which action potentials are propagated. 12-7 Describe the structure of a synapse, and explain the mechanism involved in synaptic activity. 12-8 Describe the major types of neurotransmitters and neuromodulators, and discuss their effects on postsynaptic membranes. 12-9 Discuss the interactions that enable information processing to occur in neural tissue.

The Nervous System
Includes all neural tissue in the body
Neural tissue contains two kinds of cells
Neurons
Cells that send and receive signals
Neuroglia (glial cells)
Cells that support and protect neurons

Organs of the Nervous System
Brain and spinal cord
Sensory receptors of sense organs (eyes, ears, etc.)
Nerves connect nervous system with other systems

12-1 Divisions of the Nervous System
Anatomical Divisions of the Nervous System
Central nervous system (CNS)
Peripheral nervous system (PNS)

The Central Nervous System (CNS)
Consists of the spinal cord and brain
Contains neural tissue, connective tissues, and blood vessels Functions of the CNS are to process and coordinate:
Sensory data from inside and outside body
Motor commands control activities of peripheral organs (e.g., skeletal muscles) Higher functions of brain intelligence, memory, learning, emotion

The Peripheral Nervous System (PNS)
Includes all neural tissue outside the CNS
Functions of the PNS
Deliver sensory information to the CNS
Carry motor commands to peripheral tissues and systems

Nerves (also called peripheral nerves)
Bundles of axons with connective tissues and blood vessels
Carry sensory information and motor commands in PNS
Cranial nerves — connect to brain
Spinal nerves — attach to spinal cord

Functional Divisions of the PNS
Afferent division
Carries sensory information
From PNS sensory receptors to CNS
Efferent division
Carries motor commands
From CNS to PNS muscles and glands

Receptors and effectors of afferent division
Receptors
Detect changes or respond to stimuli
Neurons and specialized cells
Complex sensory organs (e.g., eyes, ears)
Effectors
Respond to efferent signals
Cells and organs

Somatic nervous system (SNS)
Controls voluntary and involuntary (reflexes) muscle skeletal contractions Autonomic nervous system (ANS)
Controls subconscious actions, contractions of smooth muscle and cardiac muscle, and glandular secretions Sympathetic division has a stimulating effect
Parasympathetic division has a relaxing effect
12-2 Neurons
Neurons
The basic functional units of the nervous system
The structure of neurons
The Cell Body
Cytoskeleton
Neurofilaments and neurotubules in place of microfilaments and microtubules Neurofibrils: bundles of neurofilaments that provide support for dendrites and axon Nissl bodies
Dense areas of RER and ribosomes
Make neural tissue appear gray (gray matter)

Dendrites
Highly branched
Dendritic spines
Many fine processes
Receive information from other neurons
80–90% of neuron surface area
The axon
Is long
Carries electrical signal (action potential) to target
Axon structure is critical to function
Axoplasm
Cytoplasm of axon
Contains neurofibrils, neurotubules, enzymes, organelles
Axolemma
Specialized cell membrane
Covers the axoplasm
Axon hillock
Thick section of cell body
Attaches to initial segment
Initial segment
Attaches to axon hillock...
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