2A The Nervous System PP (1)

Unit 3: The Nervous System

Introduction to the Nervous System

• The human nervous system is a complex network responsible for all bodily functions including thoughts, feelings, and actions.

• It serves as the communication system between internal organs and external surroundings.

• Key functions:

  1. Receive Information: Sensory data collected by receptors.

  2. Process Information: Interpretation and integration of sensory inputs in the brain.

  3. Coordinate Response: Forming and executing appropriate responses.

Divisions of the Nervous System

• The nervous system can be categorized into two major divisions:

  • Central Nervous System (CNS)

  • Peripheral Nervous System (PNS)

Central Nervous System (CNS)

• Composed of the brain and spinal cord.

• Receives, processes, and sends neural messages to and from the PNS.

• Acts as the control center for bodily activities.

Peripheral Nervous System (PNS)

• Encompasses all neurons outside the brain and spinal cord.

• Divided into:

  • Somatic Nervous System: Controls voluntary movements by transmitting signals to skeletal muscles.

  • Autonomic Nervous System: Regulates involuntary actions such as heart rate and digestion.

Sensory and Motor Functions

• Sensory Functions: Neural pathways collect information about stimuli (e.g., light, sound, temperature) and send it to the CNS for processing.

• Motor Functions: Messages from the CNS initiate actions in muscles and glands through motor pathways.

Sensory Receptors

• Specialized receptors detect various types of stimuli:

  • Photoreceptors: Detect light (in the eyes).

  • Gustatory Receptors: Detect taste (in the mouth).

  • Cutaneous receptors: Detect touch, pressure, and pain (in the skin).

Types of Neurons

• Sensory Neurons (Afferent Neurons): Transmit sensory information from receptors to the CNS.

• Motor Neurons (Efferent Neurons): Carry signals from the CNS to effectors such as muscles and glands.

• Interneurons: Connect sensory and motor neurons within the CNS.

Autonomic Nervous System

• Sympathetic Nervous System: Activates the body's fight-or-flight responses, increasing heart rate and respiration.

• Parasympathetic Nervous System: Promotes relaxation and conservation of energy; it regulates bodily functions when at rest.

Interaction of Sympathetic and Parasympathetic Systems

• Both systems balance the body's responses to maintain homeostasis.

• The sympathetic system prepares the body for action, while the parasympathetic system helps return it to a state of rest.

Neuron Structure

• Dendrites: Receive signals from other neurons.

• Axon: Transmits impulses away from the cell body to other neurons or muscles.

• Myelin Sheath: Insulates the axon, speeding up electrical signal transmission.

• Synapse: Junction between neurons where neurotransmitters communicate signals.

Communication Between Neurons

• Neurons communicate through:

  • Electrical impulses (action potentials) travel down the axon.

  • Chemical signals (neurotransmitters) are released at the synapse to transmit signals to the next neuron.

Key Terms/Concepts

• CNS: Central Nervous System

• PNS: Peripheral Nervous System

• SNS: Somatic Nervous System

• ANS: Autonomic Nervous System

• Sympathetic NS: Division of ANS that stimulates fight or flight responses.

• Parasympathetic NS: Division of ANS that promotes rest and digestion.

Review Questions

• Evaluate the roles of the somatic and autonomic systems in voluntary and involuntary actions.

• Discuss how the nervous system maintains homeostasis during stressful situations.