Psychology Unit 3 AOS 1

The nervous system is responsible for processing sensory information, coordinating responses, and maintaining homeostasis. It is divided into the Central Nervous System (CNS) and the Peripheral Nervous System (PNS).

Nervous System Functioning

Roles of Different Subdivisions of the Nervous System

Central Nervous System (CNS)

The CNS consists of:

• The Brain: Controls voluntary and involuntary processes, divided into lobes (frontal, parietal, temporal, occipital), cerebellum, and brainstem.

• The Spinal Cord: Acts as a communication pathway between the brain and body, and controls reflex actions.

Peripheral Nervous System (PNS)

The PNS connects the CNS to the body and is divided into:

• Somatic Nervous System (SNS): Controls voluntary movement and relays sensory information.

• Autonomic Nervous System (ANS): Regulates involuntary functions and is divided into:

• Sympathetic Nervous System (fight-or-flight)

• Parasympathetic Nervous System (rest-and-digest)

The role of neurotransmitters in transmission

Neurotransmitters facilitate communication between neurons across synapses.

Types of Neurotransmitters:

• Excitatory neurotransmitters (e.g., glutamate) increase neural activity.

• Inhibitory neurotransmitters (e.g., GABA) decrease neural activity.

• Neuromodulators (e.g., dopamine, serotonin) influence long-term neural function and behavior.

Synaptic Transmission

Synaptic transmission is the process by which neurons communicate with each other through synapses. It involves the transfer of electrical or chemical signals from a presynaptic neuron to a postsynaptic neuron or target cell. This process is fundamental to all neural functions, including sensation, movement, cognition, and memory.

• Steps

  1. The presynaptic neuron becomes active and sends an action potential down the axon towards the axon terminals where synaptic vesicles hold neurotransmitters.

  2. When the action potential reaches the axon terminals, the presynaptic neuron releases neurotransmitters into the synaptic cleft.

  3. Neurotransmitters then bind to the dendrites of the postsynaptic neuron.

  4a. The message has been received and processed after neurotransmitters bind to the postsynaptic neuron.

  4b. Once the postsynaptic neuron receives the message, it generates its action potential. This electrical impulse travels down the axon, transmitting the message to the next neuron, creating a chain of communication.

Types of Synapses

1. Chemical Synapses

• Use neurotransmitters to relay signals.

• More common in the nervous system.

• Can amplify signals and allow for modulation (e.g., learning and memory).

2. Electrical Synapses

• Use gap junctions to allow direct ionic current flow between neurons.

• Faster than chemical synapses but less flexible (mainly found in cardiac and some neural circuits).

Key Neurotransmitters and Their Functions

Synaptic Plasticity

Synaptic plasticity is the brain’s ability to adapt and rewire itself based on experience.

Mechanisms of Synaptic Plasticity:

1. Long-Term Potentiation (LTP): Strengthening of synaptic connections through repeated activation (important for learning).

2. Long-Term Depression (LTD): Weakening of synaptic connections due to reduced activity (helps remove irrelevant information).

Types of Neural Adaptation:

• Sprouting: Growth of new axons or dendrites to strengthen existing connections.

• Rerouting: Neurons form new pathways when old ones are damaged.

• Pruning: Elimination of weaker or unused connections to improve efficiency (common in adolescence).

Stress as an Example of a Psychobiological Process

Internal and External Stressors & Their Impact on Stress Responses

Stress can be caused by internal or external factors:

• Internal stressors: Psychological (e.g., self-doubt, overthinking).

• External stressors: Environmental (e.g., work deadlines, social conflicts).

Both can trigger psychological and physiological stress responses, including fight-or-flight activation and cortisol release.

The Gut-Brain Axis (GBA) and Its Role in Stress

• The gut microbiota communicates with the nervous system via the vagus nerve.

• Stress affects gut bacteria, influencing serotonin production (linked to mood disorders like depression).

• Disruptions in the GBA can impact mental health, cognition, and stress resilience.

The Explanatory Power of Hans Selye’s General Adaptation Syndrome (GAS)

Selye’s GAS model explains how the body responds to prolonged stress in three stages:

1. Alarm Stage: Initial fight-or-flight response, adrenaline surge, and activation of the sympathetic nervous system.

2. Resistance Stage: The body adapts to stress; cortisol is released to maintain energy, but prolonged exposure weakens the immune system.

3. Exhaustion Stage: The body’s resources become depleted, leading to burnout and increased risk of illness.

The Explanatory Power of Lazarus & Folkman’s Transactional Model of Stress and Coping

This model explains how stress is influenced by cognitive appraisal:

1. Primary Appraisal – Determines if a situation is irrelevant, benign-positive, or stressful.

2. Secondary Appraisal – Assesses whether resources are sufficient to cope with the stressor.

Effective coping depends on:

• Context-Specific Effectiveness: Choosing the right coping strategy for a given situation.

• Coping Flexibility: Adjusting strategies based on effectiveness.

Use of Strategies (Approach & Avoidance) for Coping with Stress and Improving Mental Wellbeing

• Approach Strategies: Involve actively dealing with stress (e.g., problem-solving, seeking support).

• Avoidance Strategies: Involve ignoring or escaping stress (e.g., denial, substance use).

• Coping Flexibility: The ability to adapt coping methods depending on the situation.