Fundamentals of the Nervous System and Nervous Tissue

Fundamentals of the Nervous System

• Nervous System Overview
  • Master control system of the body.
  • Functions:
  • Sensory Input: Gathers input from stimuli.
  • Integration: Processes and interprets sensory input.
  • Motor Output: Response to stimuli by activating effector organs.

Organization of the Nervous System

• CNS (Central Nervous System): Includes the brain and spinal cord.
• PNS (Peripheral Nervous System): Consists of all nerves outside the CNS.

Major Structures of the CNS

• Cerebrum: Processes sensory information, controls movements, reasoning.
• Cerebellum: Coordinates muscle movements, maintains posture and balance.
• Brain Stem: Controls autonomic functions such as heart rate and respiration.
• Spinal Cord: Transmits signals between the brain and the body.

Neuron Types

• Functional Classes of Neurons:
  • Sensory Neurons: Carry signals from sensory receptors to the CNS.
  • Motor Neurons: Transmit signals from the CNS to effector organs.
  • Interneurons: Connect sensory and motor neurons.

Nervous System Pathways

• Motor Pathways: Control voluntary movements.
• Sensory Pathways: Relay sensory information to the brain.
• Autonomic Nervous System: Controls involuntary functions, divided into:
  • Sympathetic Nervous System: Prepares the body for stress-related activities.
  • Parasympathetic Nervous System: Calms the body, conserving energy.

Structures and Types of Neuroglia

• Neurons: Excitable cells that transmit electrical signals.
• Supporting Cells (Neuroglia):
  • Astrocytes: Support neurons, regulate the environment.
  • Microglia: Immune defense in the CNS.
  • Ependymal Cells: Line the brain and spinal cord, produce CSF.
  • Oligodendrocytes: Myelinate CNS axons.
  • Schwann Cells: Myelinate PNS axons.
  • Satellite Cells: Support neuron cell bodies in ganglia.

Synapse Types and Function

• Synapse: Junction between neurons.
  • Types:
  • Axodendritic: Between axon terminal and dendrite.
  • Axosomatic: Between axon terminal and cell body.
  • Axoaxonic: Between axon terminals.

Electrical vs. Chemical Synapses

• Electrical Synapses: Allow direct ion flow between neurons.
• Chemical Synapses: Use neurotransmitter release for signal transmission.

Neurotransmitters

• Excitatory Neurotransmitters: Cause depolarization (e.g., dopamine, epinephrine).
• Inhibitory Neurotransmitters: Cause hyperpolarization (e.g., GABA, serotonin).

The Brain and Its Functions

• Cerebrum: Largest part of the brain; divided into lobes:

  • Frontal Lobe: Controls thought, movement, and reasoning.
  • Parietal Lobe: Processes sensory information.
  • Occipital Lobe: Involved in vision.
  • Temporal Lobe: Manages sensory memories and sound.

• Thalamus: Relay station for sensory and motor signals.

• Hypothalamus: Regulates homeostasis (temperature, hunger, thirst).

• Pons: Assists with motor control and sensory analysis.

• Medulla Oblongata: Controls autonomic functions (e.g., heart rate).

Structure of Nerves

• Nerve Composition:
  • Endoneurium: Encloses individual nerve fibers.
  • Perineurium: Bundles groups of fibers.
  • Epineurium: Surrounds the entire nerve.

Reflex Arc Components

• Components:
  • Receptor: Detects a stimulus.
  • Sensory Neuron: Sends impulse to the CNS.
  • Integration Center: Processes the signal.
  • Motor Neuron: Sends impulse to effector.
  • Effector: Muscle or gland responding to the stimulus.

Limbic System

• Function: Involved in emotion and memory.
• Key Components:
  • Hippocampus: Memory formation.
  • Amygdala: Emotion regulation.

Conclusion

Understanding the structure and function of the nervous system is essential for comprehending how physiological signals and responses occur in the body, influencing behavior and bodily functions. The interplay between various neuroglial cells supports neuron health and functionality, making the nervous system a complex yet organized network crucial for survival and interaction with the environment.