Biological bases of mental life and behaviour

Nervous System Overview

• Comprised of central nervous system (CNS) and peripheral nervous system (PNS).
• Underlies all psychological activity with an estimated 10-120 billion neurons in the brain.
• Average neuron communicates with approximately 1,000 other neurons.

Neuron Types

• Sensory Neurons (Afferent): Convey sensory information from receptors to the CNS.
• Interneurons: Typically connect sensory and motor neurons; most abundant in the brain and spinal cord.
• Motor Neurons (Efferent): Transmit commands from CNS to muscles and glands for voluntary and involuntary actions.

Neuron Anatomy

• Dendrites: Receive incoming signals from other neurons.
• Cell Body: Contains nucleus, processes input received via dendrites.
• Axon: Transmits signals away from the cell body to other neurons, muscles, or glands.
• Myelin Sheath: Insulates the axon to speed up signal transmission; appears as white matter in the brain.
• Nodes of Ranvier: Gaps in the myelin sheath that facilitate rapid signal conduction.

Neural Firing Process

• Resting Potential: Neuron at -70mV, polarized state maintained by ion concentrations.
• Graded Potentials: Changes in membrane potential due to synaptic input, allowing integration of signals.
• Action Potential: Rapid depolarization occurs if a threshold of -50mV is reached; sodium ions rush in, followed by potassium ions exiting to restore potential.

Synaptic Transmission

• Presynaptic Neuron: Sends the impulse.
• Postsynaptic Neuron: Receives the impulse.
• Neurotransmitters released from terminal buttons into the synaptic cleft facilitate communication by binding to receptors on receiving neurons.
• Excitatory neurotransmitters increase likelihood of action potential, while inhibitory neurotransmitters decrease it.

Neurotransmitters and Their Functions

• Glutamate: Major excitatory neurotransmitter; vital for learning and memory.
• GABA (gamma-aminobutyric acid): Main inhibitory neurotransmitter; regulates anxiety and prevents seizures.
• Dopamine: Influences motivation and reward; dysregulation linked to Parkinson's disease and schizophrenia.
• Serotonin: Involved in mood regulation; undersupply linked to depression.
• Acetylcholine (ACh): Key in muscle movement and memory; associated with Alzheimer's when levels are low.
• Endorphins: Natural pain relievers; enhance mood, learning, and decrease appetite.
• Epinephrine/Norepinephrine: Facilitate response to stress and arousal; impact learning and memory.

Endocrine System

• Comprises glands that secrete hormones into the bloodstream for broad intercellular communication.
• Pituitary Gland: Known as the master gland; regulates other glands.
• Adrenal Glands: Secrete adrenaline in response to stress.
• Thyroid Gland: Regulates metabolism and growth.

Peripheral Nervous System (PNS)

• Connects CNS to peripheral body parts; divided into somatic and autonomic systems.
• Somatic Nervous System: Controls voluntary movements and relays sensory information.
• Autonomic Nervous System: Manages involuntary processes; includes sympathetic (fight or flight) and parasympathetic (rest and digest) divisions.

Central Nervous System (CNS)

• Consists of the brain and spinal cord; responsible for processing information and transmitting signals.
• Spinal Cord: Mediates reflex actions and transmits signals between brain and body.
• Hindbrain Structures: Control vital functions (e.g., respiration, heart rate) and facilitate movement/balance.
• Cerebellum: Coordinates smooth, balanced movements.

Evolution of the Nervous System

• Early vertebrate ancestors exhibited simple reflex functions.
• Evolution led to the development of a more complex human brain capable of advanced cognitive functions.
• The cerebrum constitutes 82% of the brain's mass, reflecting complex thought processing.

Key Concepts in Neural Function

• Localisation of Function: Specific brain regions specialize in different functions but work collectively for actions and thoughts.
• Reflex Arcs: Quick responses bypassing the brain for rapid reaction to stimuli, often involving simple two-neuron pathways for efficiency.### Sensory and Cognitive Processes
• Learning to associate one stimulus with another involves complex sensory and cognitive processes.

Reticular Formation

• A network of neurons from the medulla to the midbrain, essential for maintaining consciousness and regulating arousal levels.
• Integrates information from various neural pathways, enhancing attention to simultaneous activity in the brain.
• Damage can cause sleep disturbances and lead to coma.

Midbrain

Tectum

• Involves structures for vision and hearing, helping orientation to stimuli.
• Blindsight phenomenon occurs with damage to visual processing circuits but intact tectum.

Tegmentum

• Contains parts of the reticular formation and functions related to movement.
• Houses the substantia nigra, which deteriorates in Parkinson's disease, affecting approach-avoidance learning.

Forebrain

• Encompasses complex sensory, emotional, cognitive, and behavioral processes.

Hypothalamus

• Located in front of the midbrain, connecting the nervous system to the endocrine system.
• Governs crucial behaviors like eating, sleeping, and emotional responses, and regulates homeostasis.

Thalamus

• Acts as a sensory information switchboard, processing and routing signals from sensory systems to higher brain centers.
• Filters and enhances the importance of sensory messages to guide attention.

Subcortical Structures

Limbic System

• Comprises structures crucial for emotion, motivation, learning, and memory.

Septal Area

• Linked to pleasure, emotional learning, and responses to stress.

Amygdala

• Involved in emotional significance, fear responses, and recognition of fearful emotions.

Hippocampus

• Vital for forming and retrieving new memories, without it, new information cannot be stored.

Basal Ganglia

• Located at the base of the forebrain, involved in movement control and automatic responses.
• Damage may lead to movement disorders and cognitive impairments.

Cerebral Cortex

• A dense layer of interneurons processed in two types: primary and association areas.

Primary Cortex Areas

• Involved in processing raw sensory information and initiating movement.

Association Cortex Areas

• Engage in complex cognitive processes, enabling object and perception recognition.

Lobes of the Cerebral Cortex

• Divided into four lobes: occipital, parietal, frontal, and temporal.

Occipital Lobes

• Specialized for vision; damage can lead to blindness.

Parietal Lobes

• Process touch, movement, and spatial awareness; damage affects sensory recognition.

Frontal Lobes

• Responsible for movement, planning, attention, and personality; damage can impair cognitive functions.

Motor Cortex

• Initiates voluntary movements and manages body movement information flow.

Broca's Area

• Essential for speech production and understanding grammar; damage may result in Broca's aphasia, impacting speech fluency.

Temporal Lobes

• Important for hearing and language; damage can lead to nonverbal deficits or Wernicke's aphasia, characterized by comprehension issues.

Neuroplasticity

• Describes the brain’s ability to reorganize and adapt in response to experiences and damage.
• Can enhance learning and recovery in individuals with brain injuries.

Neurogenesis

• The process of producing new neurons and repairing brain structures, primarily occurring in the hippocampus.

Cognitive Neuropsychology

• Aims to understand the connection between brain structure, function, and psychology.

Brain, Gene, and Behavior

• Investigates the genetic variability that affects phenotypic traits, like intelligence and personality.
• Heritability measures how much of characteristic variability is due to genetic differences.

Peripheral Nervous System (PNS)

• Composed of neurons connecting the CNS to the body, including two divisions:

Somatic Nervous System

• Manages sensory and motor neurons related to voluntary actions.

Autonomic Nervous System

• Regulates involuntary bodily functions, subdivided into sympathetic (stress response) and parasympathetic (restoration to baseline).

Central Nervous System (CNS)

• Consists of the brain and spinal cord, coordinating body functions and responses.### Nervous System Overview
• The nervous system is organized hierarchically, with higher centers regulating lower-level processes.
• The spinal cord transmits sensory info to the brain and motor messages to muscles and organs.
• Contains reflex actions that operate independently of brain input.

Hindbrain Components

• Medulla Oblongata: Controls vital functions like heartbeat, circulation, and respiration; connects the spinal cord and brain.
• Cerebellum: Involved in smooth movement coordination, learning, and stimulus discrimination.
• Reticular Formation: Maintains consciousness and regulates states of arousal and sleep cycles.

Midbrain Structure

• Comprises the Tectum and Tegmentum.
• Tectum: Processes visual and auditory stimuli and links negative emotions to escape behaviors.
• Tegmentum: Facilitates movement and associates pleasure with rewarding behaviors, involved in part of the reticular formation.

Forebrain Components

• Consists of the Hypothalamus, Thalamus, and Cerebrum.
• Hypothalamus: Regulates eating, sleeping, sexual activity, and emotional experiences.
• Thalamus: Processes sensory info and relays it to higher brain areas.
• Cerebrum: Contains subcortical structures (limbic system and basal ganglia) and the cerebral cortex.

Subcortical Structures

• Limbic System: Involved in emotions, motivation, learning, and memory (includes amygdala and hippocampus).
• Basal Ganglia: Associated with movement, mood, and memory.

Cerebral Cortex Functions

• Supports voluntary movement, complex sensory discrimination, and symbolic thinking.
• Comprises primary sensory and motor areas and association areas that integrate perceptions and plans.
• Connected by the Corpus Callosum, facilitating interhemispheric communication.

Hemispheres and Lobes

• Each hemisphere consists of four lobes: Occipital (vision), Parietal (touch, movement perception), Frontal (movement coordination, planning, personality), and Temporal (hearing, language).
• Psychological processes can be lateralized, varying by hemisphere.

Neuroplasticity and Neurogenesis

• Neuroplasticity indicates continuous brain development in response to experiences.
• Neurogenesis refers to the brain's capacity for neuron production and repair.

Genetics vs. Environment in Psychology

• Genetics and environment interact complexly in psychological traits.
• Behavioral genetics explore heritability of traits, such as intelligence and personality.
• Heritability: Proportion of trait variance attributable to genetic differences.

Key Terms

• Acetylcholine (ACh): Neurotransmitter for muscle contractions and memory.
• Action Potential: Temporary membrane polarization leading to neuron firing.
• Adrenaline: Hormone released during emergencies, activates physiological arousal.
• Neurotransmitters: Chemicals that transmit signals between neurons.
• Cognitive Neuropsychology: Studies the interplay of brain structure and psychological processes.