Chapter_5__1_

Chapter 5: Brains, Bodies, and Behavior PSY 102

1. Understanding the Body's Control Systems

• Overview: The nervous system is the body's communication network.

  • Extensive array of specialized cells.

  • Facilitates communication between the brain and body.

Components of the Nervous System

• Central Nervous System (CNS):

  • Comprises the brain and spinal cord.

  • Serves as the core processing unit of information.

• Peripheral Nervous System (PNS):

  • Network of neurons linking CNS to skin, muscles, and glands.

  • Functions as the communication corridor for CNS and body.

• Overall Influence:

  • Affects behavior and interacts with the endocrine system (hormonal signals).

2. Components of Neurons

• Introduction: The nervous system is made up of over 100 billion neurons.

• Neurons:

  • Cells responsible for receiving and transmitting information.

  • Cell Body (Soma): Contains the nucleus, sustaining cell life.

  • Dendrite:

    • Treelike fiber that receives information from other cells and transmits it to soma.

  • Axon:

    • Long fiber that sends information away from the soma to other neurons, muscles, and glands.

3. Neuron Structure: Key Components

• Diversity in Neurons:

  • Some neurons possess extensive dendritic branching for receiving multiple inputs.

• Axonal Specialization:

  • Axons can be very long, e.g., spinal cord to muscles.

  • Myelin Sheath: Fatty insulation surrounding axons to speed up signal transmission.

  • Axon Termination: Features terminal buttons at axon ends.

4. Neuronal Signaling: Electrochemical Process

• Neural Communication Process:

  • Involves both electrical and chemical signals.

  • Components:

    • Dendrites receive signals; those signals are passed to soma, then to axon.

• Synapses:

  • Junctions where neurotransmitters transfer signals between neurons.

  • Crucial for complex neural communication.

5. Action Potential Transmission in Neurons

• Nodes of Ranvier: Gaps between myelin segments facilitate faster signal transmission as action potentials jump from node to node.

• Action Potential:

  • Triggered by a significant change in electrical charge, allowing sodium influx, creating a temporary positive charge in the axon.

6. Neurotransmitters and Their Functions

• Definition: Chemicals that transmit signals across synapses.

• Lock and Key Mechanism:

  • Specific neurotransmitters fit specific receptor sites on receiving neurons.

• Types of Neurotransmitters:

  • Acetylcholine (ACh): Involved in muscle contractions and cognitive functions (memory). Low levels associated with Alzheimer's.

  • Dopamine: Associated with movement, pleasure, and learning. Linked to schizophrenia (high levels) and Parkinson’s disease (low levels).

  • Endorphins: Natural pain relievers released during exercise or stress, leading to feelings of euphoria (runner's high).

  • GABA: Main inhibitory neurotransmitter, low levels can cause anxiety.

  • Glutamate: Most abundant, involved in synaptic plasticity and learning.

  • Serotonin: Influences mood, sleep, and appetite; low levels linked to depression.

7. Influence of Drugs on Neurotransmission

• Agonists: Drugs that mimic neurotransmitters, enhancing their effects (e.g., cocaine and dopamine).

• Antagonists: Inhibit neurotransmitter action (e.g., curare blocking acetylcholine).

8. The Brain Structure and Function

Major Parts of the Brain

• Brain Stem: Controls basic life functions (breathing, heartbeat).

  • Medulla: Manages vital functions like heart rate.

  • Pons: Coordination of movement.

• Cerebellum: Involved in balance, movement, and motor coordination.

• Limbic System: Center for emotions and memory (includes amygdala, hippocampus, hypothalamus).

• Cerebral Cortex: Responsible for higher-level functions (language, decision-making).

  • Organized into lobes: Frontal (thinking, planning), Parietal (touch), Occipital (visual), Temporal (hearing).

9. Neuroplasticity and Neurogenesis

• Neuroplasticity: The brain’s ability to reorganize itself through experience.

  • Vital for learning and recovery from injury.

• Neurogenesis: Formation of new neurons; occurs in specific brain areas as a response to learning and experiences.

10. The Nervous System

• Function: Acts as the body's electrical information highway made of nerves.

• CNS: Interprets and processes sensory information and commands.

• PNS: Connects CNS to sensory receptors, muscles, and glands.

• Types of Neurons:

  • Sensory Neurons (affective): Carry information to the brain.

  • Motor Neurons (efferent): Transmit commands to the body.

  • Interneurons: Communicate within the CNS.

• Spinal Cord: Relay center for sensory and motor information; facilitates reflex actions without brain involvement.

11. Autonomic Nervous System (ANS)

• Divided into:

  • Sympathetic Division: Prepares body for stress, fight-or-flight response.

  • Parasympathetic Division: Calms body, conserves energy post-stress.

12. Endocrine System

• Overview: Regulates emotions and behaviors via hormones produced by glands.

• Hormonal Function: Influence various bodily functions (growth, metabolism).

• Major Glands:

  • Pituitary Gland: Master gland regulating growth and hormone levels.

  • Thyroid and Adrenal Glands: Regulate energy use and stress responses.

  • Testes and Ovaries: Influence sexual characteristics and reproductive functions.

13. Methods to Study the Brain

• Post-Mortem Analysis: Examining deceased brains.

• Neuroimaging Techniques:

  • CT: Structural imaging using X-rays.

  • MRI: Detailed structure using magnetic resonance.

  • fMRI: Measures brain activity by tracking blood flow.

  • PET: Studies brain function through metabolic processes.

  • EEG: Tracks electrical activity of the brain.

  • MEG: Assesses magnetic fields created by neural activity.