Biological Bases of Mental Life and Behaviour

Learning Outcomes

  • Describe the basic units of the nervous system
  • Describe the major structures and functions of the central nervous system (CNS)
  • Explain the roles of genetics and environment in psychological functioning
  • Explain sensation and perception

Biological Bases of Behaviour

  • Neurons: Basic units of the nervous system specializing in information transfer.
    • Types of neurons:
    • Sensory Neurons: Transmit information from sensory receptors to the brain (afferent).
    • Motor Neurons: Relay commands from the brain to muscles and glands (efferent).
    • Interneurons: Interconnect neurons, most common type.

Anatomy of the Neuron

  • Parts of the neuron:
    • Dendrites: Receive signal inputs from other neurons.
    • Cell Body: Contains the nucleus and processes information.
    • Axon: Transmits impulses away from the cell body.
    • Myelin Sheath: Insulates the axon to speed up transmission.
    • Terminal Buttons: Release neurotransmitters into the synaptic cleft.

Neuron Firing Process

  • Resting Potential: Neuron is polarized with a negative inside and positive outside.
  • Graded Potentials:
    • Depolarization: Increase in the neuron’s firing potential.
    • Hyperpolarization: Decrease in firing potential.
  • Action Potential: Triggered when threshold is reached, leading to neural firing.

Transmission of Nerve Impulses

  • Synapse: Junction between neurons where neurotransmitters are released.
  • Neurotransmitters (NTs): Chemicals that transmit information across the synapse.
    • Stored in vesicles and released during action potentials.
    • Bind to postsynaptic receptors, resulting in graded potentials.

Major Neurotransmitters and Their Functions

  • Glutamate: Excitatory, widespread throughout the nervous system.
  • GABA: Inhibitory, primarily in the brain.
  • Dopamine: Associated with reward, pleasure, and motor functions.
  • Serotonin: Involves sleep, mood regulation, and aggression.
  • Acetylcholine: Important for memory and muscle activation.
  • Endorphins: Involved in pain relief and mood elevation.

Endocrine System

  • Definition: A collection of glands releasing hormones into the bloodstream for intercellular communication.
  • Function: Broadcasts messages globally rather than directly targeting specific functions.

Nervous System Overview

  • Central Nervous System (CNS): Directs psychological and basic life processes.
    • Brain: Processes information and maintains life functions.
    • Spinal Cord: Receives sensory input and sends motor output.
  • Peripheral Nervous System (PNS): Carries information to and from the CNS.
    • Somatic Nervous System: Conveys sensory information to the CNS and sends motor messages to muscles.
    • Autonomic Nervous System (ANS): Manages basic life functions, divided into:
    • Sympathetic: Emergency responses (fight or flight).
    • Parasympathetic: Rest and digest functions.

Divisions of the Autonomic Nervous System

  • Sympathetic Nervous System: Prime activator during stress or threats.
  • Parasympathetic Nervous System: Restores the body to a calm state post-stress.

The Human Brain

Structure of the Brain

  • Hindbrain:
    • Medulla Oblongata: Controls autonomous functions like heartbeat and respiration.
    • Cerebellum: Manages fine motor skills and coordination.
    • Reticular Formation: Regulates arousal and consciousness.
    • Pons: Connects different brain regions and aids in sleep and respiration.
  • Midbrain: Coordinates movement and arousal and processes sensory information.
  • Forebrain: Involved in higher cognitive functions, processing sensory info, and regulating emotions.
    • Thalamus: Relay center for sensory information.
    • Hypothalamus: Regulates hunger, thirst, and emotional responses.
    • Limbic System: Vital for emotions and memory (includes the amygdala and hippocampus).

Cerebral Cortex

  • Divided into lobes with specific functions:
    • Frontal Lobe: Key in decision making, problem-solving, and planning.
    • Parietal Lobe: Processes touch and spatial orientation.
    • Occipital Lobe: Dedicated to vision processing.
    • Temporal Lobe: Involved in language and auditory processing.

Neuroplasticity

  • The brain's ability to reorganize and adapt in response to experiences and environmental changes.
  • Neurogenesis: The production of new neurons in the brain.

Behavioural Genetics

  • Studies the relationship between genetic predispositions (genotypes) and observable behaviors (phenotypes).
  • Focuses on how changes in genetics can impact psychological attributes.

Sensation and Perception

Sensation

  • Process of collecting information from the environment through sensory receptors, converting physical stimuli to neural signals (transduction).

Perception

  • The brain actively organizes and interprets sensory information.
  • Influenced by context, prior experiences, and expectations.

Thresholds

  • Absolute Threshold: The minimum energy needed to activate sensory receptors.
  • Signal Detection Theory: Involves initial sensitivity to stimuli and decision-making processes influenced by biases.

Perceptual Organization

  • Top-Down Processing: Uses prior knowledge to perceive stimuli.
  • Bottom-Up Processing: Analyzes simple features and builds to a complex perception.

Conclusion

  • Integration of complex neural activities forms the physiological foundation for psychological processes. Sensation and perception shape our understanding of the environment and our interactions with it.

Summary

  • Biological structures like neurons and neurotransmitters underpin psychological experiences, while the complex interplay of the nervous system contributes to sensations and perceptions of the world around us.