Biopsychology: Nervous System Overview

Biopsychology

• Focuses on the biological basis of behavior
• Explores relationships between the brain, behavior, and psychological phenomena
• Also known as "Behavioral Neuroscience"

Nervous System

• Central Nervous System (CNS): Brain and spinal cord
  • Processes and integrates information
  • Controls higher brain functions (thought, emotion)
  • Protected by the skull, vertebral column, cerebrospinal fluid, and blood-brain barrier
  • Limited ability to regenerate after injury
  • Responsible for sensory information processing and motor command generation
• Peripheral Nervous System (PNS): Nerves outside the CNS (cranial and spinal nerves)
  • Connects the CNS to the body
  • Carries sensory information to the CNS and motor commands to muscles
  • Exposed to injury; greater regenerative capacity than the CNS

Major Animal Species in Biopsychology Research

• Rodents: Rats and mice (dominant model)
• Non-human primates: Macaques and marmosets
• Aquatic vertebrates: Fish and frogs
• Squid: Used for studying neuronal communication
• Flies: Used for studying genetics and behavior
• Worms: Used for studying basic nervous system functions

Basic Cell Components

• Plasma membrane:
  • Outer layer, controls what enters and exits the cell
  • Composed of a phospholipid bilayer (hydrophobic tails inward, hydrophilic heads outward)
  • Selectively permeable (some molecules pass freely, others need channels or active transporters)
• Nucleus:
  • Contains most of the cell's DNA
  • Serves as the cell's control center
• Mitochondria:
  • Powerhouse of the cell
• Responsible for generating ATP (energy)
• Ribosomes:
  • Sites of protein synthesis

ATP and its Importance

• ATP (Adenosine Triphosphate): Primary energy source in cells
• Brain: Uses more energy than any other organ, relying heavily on ATP
• Composition: Adenine, ribose, and three phosphate groups
• Energy Release: Hydrolysis of ATP to ADP and a phosphate group releases energy
• Importance:
  • Powers cellular processes (muscle contraction, active transport, biochemical reactions)
  • Essential for metabolism, protein synthesis, and DNA replication

DNA to Protein Process

• Transcription:
  • Occurs in the nucleus
  • DNA is transcribed into mRNA by RNA polymerase
  • mRNA carries genetic information from DNA to ribosomes
• Translation:
  • Takes place at the ribosome
  • tRNA brings amino acids based on codons in mRNA
  • Ribosome links amino acids into a polypeptide chain
  • Polypeptide folds into a functional protein

Ion Terminology

• Cation: Positively charged ion (e.g., Na⁺)
• Anion: Negatively charged ion (e.g., Cl⁻)
• Monovalent: Ion with a single positive or negative charge (e.g., Na⁺, Cl⁻)
• Divalent: Ion with a double positive or negative charge (e.g., Ca²⁺, SO₄²⁻)

Understanding the Brain's Structure and Composition

• Early Observations:
  • Nissl stain: Stained cell bodies, revealing the nucleus and rough ER
  • Golgi stain: Darkened whole cells, but only a small percentage
• Microscopy:
  • Paved the way for the Neuron Doctrine (Ramón y Cajal)
  • The brain is composed of individual neurons
  • Neurons connect to each other via long projections
• Modern Techniques:
  • Neuroimaging (MRI, fMRI, PET scans): Non-invasive brain imaging
  • Electrophysiology: Measures electrical activity in neurons
  • Molecular biology: Studies the brain at the genetic and protein level

Distinct Features of Neurons

• Excitability: Ability to generate and propagate electrical impulses (action potentials)
• Synaptic Transmission: Communication via neurotransmitter release at synapses
• Unique Structure:
  • Dendrites: Receive signals
  • Axon: Transmit signals
  • Soma (cell body): Integrates signals and contains the nucleus
• Polarity: Signals flow in a specific direction (dendrites to axon terminal)

Neuron Structure

• Dendrites: Receive signals from other neurons
• Cell body (soma): Contains the nucleus and other organelles; integrates signals
• Axon: Transmits electrical impulses away from the soma
• Axon hillock: Junction between the axon and soma; where action potentials are initiated
• Myelin sheath: Insulates the axon, speeding up signal transmission
• Nodes of Ranvier: Gaps in the myelin sheath where action potentials are regenerated
• Axon terminal: Releases neurotransmitters at synapses