Neural Tissue: Structure, Function, and Organization

Chapter 11: Neural Tissue

Introduction to Neural Tissue

The nervous system is essential for coordinating the activities of the body to maintain homeostasis. It is responsible for swift, brief, and short-term responses to stimuli, and it helps to moderate or coordinate the activities of other organ systems. The nervous system provides and interprets sensory information about both internal and external conditions.

• Homeostasis: The maintenance of a stable internal environment.

• Stimuli: Changes in the environment that elicit a response from the nervous system.

Steps of Coordination in the Nervous System

The nervous system coordinates responses through a series of steps:

1. Receives information about the internal and external environment from receptors.

2. Information is distributed to the brain and spinal cord in the form of electrical impulses transmitted along nerve fibers (Sensory information).

3. Centers in the brain/spinal cord process and interpret the information and coordinate a response if necessary.

4. Motor commands, in the form of electrical impulses, are transmitted along nerve fibers to muscles and glands (effectors) to carry out a response.

• Receptors: Specialized cells or structures that detect changes in the environment.

• Effectors: Muscles or glands that carry out the response.

Functional Organization of the Nervous System

Central and Peripheral Divisions

The nervous system is divided into two main parts: the Central Nervous System (CNS) and the Peripheral Nervous System (PNS).

• CNS: Consists of the brain and spinal cord; integrates information.

• PNS: Includes cranial and spinal nerves that link the CNS to the rest of the body; performs motor and sensory functions.

Sensory (Afferent) Division

• Somatic sensory division: Carries stimuli from skin, muscles, and joints.

• Visceral sensory division: Carries stimuli from organs (e.g., urinary bladder, stomach).

Motor (Efferent) Division

• Somatic motor division: Carries commands to skeletal muscles.

• Autonomic nervous system: Carries commands to cardiac muscle, smooth muscle, and glands.

Neurons: Properties and Structure

Fundamental Units of the Nervous System

Neurons are the basic functional units of the nervous system. They perform all communication, information processing, and control functions.

• Most neurons lack centrioles and cannot divide.

• Adult stem cells are only active in specific regions (e.g., nose, hippocampus).

• Neurons have a high metabolic rate and require a continuous supply of glucose and oxygen.

Fundamental Properties of Neurons

• Excitability: Ability to respond to stimuli and generate electrical changes across the cell membrane.

• Conductivity: Ability to conduct (propagate) electrical changes generated by stimuli along the neuron.

• Secretion: At the end of a neuron, chemical messengers called neurotransmitters are released to transmit information to the next cell.

Neuron Structure

• Cell body (soma): Contains the nucleus and organelles; site of metabolic activity.

• Dendrites: Branching extensions that receive information; account for most of the neuron's surface area.

• Axon: Long, thin process that propagates electrical impulses; may branch into axon collaterals for communication with multiple cells.

• Axon terminals (synaptic knobs): Contain vesicles filled with neurotransmitters for communication with other neurons or effectors.

Summary Table: Functional Organization of the Nervous System

Division	Main Function	Examples
Central Nervous System (CNS)	Integrates information	Brain, spinal cord
Peripheral Nervous System (PNS)	Links CNS to body; motor and sensory functions	Cranial nerves, spinal nerves
Sensory (Afferent) Division	Transmits sensory information to CNS	Skin, organs
Motor (Efferent) Division	Transmits motor commands from CNS to effectors	Skeletal muscle, cardiac muscle, glands

Example: Sensory-Motor Integration

When a soccer player sees a ball approaching (sensory input), the brain processes this information and sends motor commands to the muscles to kick the ball (motor output).

Additional info: The notes above are expanded with academic context and definitions for clarity. The table is recreated to summarize the functional organization of the nervous system as depicted in the provided images.