Functions and Structure of the Nervous System

Functions of the Nervous System

• Detects environmental changes (sensory input)
• Coordinates actions and responses to stimuli (behaviors)
• Stores and retrieves information (memories)
• Controls voluntary and involuntary muscle activities (movements)

Functional Classifications of the Nervous System

• Sensory (Afferent): Carries signals from receptors to the CNS
• Motor (Efferent): Carries commands from the CNS to muscles and glands
• Integrative: Processes sensory info, stores it, and makes decisions

Structure of the Nervous System

• Brain: The control center for thoughts, emotions, and actions
• Spinal Cord: Transmits signals between brain and body
• Cranial Nerves (12 pairs): Control sensory and motor functions of the head and neck
• Spinal Nerves (31 pairs): Connect CNS to the rest of the body
• Receptors: Detect stimuli
• Ganglia: Clusters of neuron cell bodies in PNS

Divisions of the Nervous System

• Central Nervous System (CNS): Brain and spinal cord
• Peripheral Nervous System (PNS): Cranial and spinal nerves, receptors, ganglia

Organization of the PNS

• Somatic Nervous System (SNS): Controls voluntary muscle movements
• Autonomic Nervous System (ANS):
  • Parasympathetic: "Rest and digest"
  • Sympathetic: "Fight or flight"
• Enteric Nervous System (ENS): Controls gastrointestinal tract

Histology of Neurons

• Cell Body (Soma): Contains the nucleus
• Dendrites: Receive signals
• Axon: Transmits signals
• Axon Terminals: Release neurotransmitters

Structural Classification of Neurons

• Multipolar (Motor): Most common, found in CNS and motor pathways
• Bipolar: Specialized sensory neurons (e.g., retina)
• Unipolar (Sensory): Found in PNS; transmit sensory information

Axonal Transport

• Anterograde: Moves materials from cell body to axon terminal
• Retrograde: Moves materials from axon terminal to cell body

Neuroglia (Glial Cells)

• CNS:
  • Astrocytes: Support neurons, blood-brain barrier
  • Oligodendrocytes: Myelinate CNS axons
  • Microglia: Phagocytic cells
  • Ependymal Cells: Produce and circulate cerebrospinal fluid (CSF)
• PNS:
  • Schwann Cells: Myelinate PNS axons
  • Satellite Cells: Regulate environment around PNS neurons

Electrical Signals in Neurons

• Graded Potential: Local changes in membrane potential
• Action Potential: Large, propagate along axons

Ion Channels in Neurons

• Leak Channels: Always open
• Voltage-Gated Channels: Open with changes in membrane potential
• Ligand-Gated Channels: Open in response to neurotransmitters
• Mechanically-Gated Channels: Respond to mechanical forces

Resting Membrane Potential

• Characteristics: -70 mV, inside negative, gated channels closed
• Factors: Na+/K+ pump, ion permeability

Action Potential

• Threshold: -55 mV; initiates action potential
• Repolarization Phase: Na+ gates close, K+ gates open
• Hyperpolarization: K+ leaks out; potential drops to -90 mV

Refractory Period

• Prevents backward propagation of action potentials

Signal Transmission at Synapse

• Electrical Synapse: Direct ion flow via gap junctions
• Chemical Synapse: Neurotransmitters mediate signal transmission

Neurotransmitters

• Examples and Functions:
  • Acetylcholine: Muscle contraction
  • GABA: Inhibitory, calming effects
  • Dopamine: Reward and pleasure
  • Serotonin: Mood and sleep regulation

Spinal Cord Anatomy

• 31 Pairs of Spinal Nerves: Cervical, thoracic, lumbar, sacral, coccygeal
• Plexuses: Cervical, brachial, lumbar, sacral; control specific body regions

Reflex Arc

• Receptor → Sensory Neuron → Integration Center → Motor Neuron → Effector

Brain Anatomy

• Cerebrum: Higher functions (thought, memory)
• Cerebellum: Coordination and balance
• Diencephalon: Thalamus and hypothalamus (sensory relay, homeostasis)
• Brainstem: Basic life functions

Types of Neural Circuits

• Diverging: Amplify signals
• Converging: Integrate signals
• Reverberating: Rhythmic activities
• Parallel After-Discharge: Complex mental processes

Functional Areas of the Brain

• Motor Cortex: Movement
• Sensory Cortex: Sensation
• Association Areas: Integration

Explore the essential functions and structure of the nervous system in this quiz. Learn about sensory inputs, motor functions, and the divisions of the nervous system, including the brain and spinal cord. This quiz will test your understanding of how the nervous system operates and its functional classifications.