Study Notes on Biology and Behavior

Organization of the Nervous System

• Overview: This section covers organization of the nervous system, neuron structure and function, and the communication between neurons.

Basic Division of the Nervous System

• Central Nervous System (CNS): Includes the brain and spinal cord. The retina is also considered a part of the CNS.

• Peripheral Nervous System (PNS): Comprises all nerve cells in the body outside the CNS, including:

  • Somatic Nervous System: Controls voluntary movements and conveys sensory information.

  • Autonomic Nervous System: Regulates involuntary bodily functions and is further divided into:

  • Sympathetic Nervous System: Prepares the body for action in stressful situations.

  • Parasympathetic Nervous System: Conserves energy and restores the body to a calm state.

The Organization of the Nervous System (CNS and PNS)

• Central Nervous System: Comprised of the brain and spinal cord.

• Peripheral Nervous System: Includes somatic and autonomic systems, as well as sympathetic and parasympathetic systems.

Neurons Are the Basic Units of the Central Nervous System

• Function of the Nervous System: Responsible for all thoughts, feelings, and actions.

• Neurons: The basic units of the nervous system; they receive, integrate, and transmit information through:

  • Electrical Impulses: Activation of neurons to carry signals.

  • Chemical Signals: Communication with other neurons.

  • Neural Networks: Formation of connections between neurons.

Neuron Structure

• Neurons process and transmit information through different structures:

  • Dendrites: Branch-like extensions that detect information from other neurons.

  • Cell Body (Soma): The site where information from thousands of neurons is collected and integrated.

  • Axon: Carries messages away from the soma.

  • Myelin Sheath: Insulates axons to facilitate faster transmission.

  • Terminal Buttons: Small nodules at the axon's end that release chemicals into the synapse.

  • Synapse: The gap between the axon of a sending neuron and the dendrites of a receiving neuron, where chemical communication occurs.

Neuron Function

• Types of Neurons:

  • Sensory Neurons: Detect information from the physical world and convey it to the brain.

  • Example: Somatosensory nerves provide information from skin and muscles.

  • Motor Neurons: Direct muscles to contract or relax, thereby producing movement.

Neuron Communication: Electrical and Chemical Signal

• Electrical Signaling: Involves the activation of the action potential.

• Chemical Signaling: Involves the flow of neurotransmitters.

Electrical Signaling: Potentials

• Resting Membrane Potential: The electrical charge of a neuron when inactive;

  • Polarized State: More negative ions inside the neuron than outside, creating the electrical energy necessary for firing.

• Action Potential (Neural Firing): The electrical signal that travels along the axon and triggers the release of chemicals at terminal buttons.

Generating an Action Potential

1. Resting Membrane Potential: Approximately -70 millivolts. (no action potential/outside positively charged ions and inside negatively charged ions)

2. Depolarization: Sodium channels open allowing Na+ ions to enter, raising the potential to about +30mV.

3. Repolarization: Potassium channels open allowing K+ ions to exit, bringing the charge back down.

4. Return to Resting State: After the action potential, the Na+/K+ pump restores the original ionic concentration by pushing 3 Na+ ions out and 2 K+ ions in.

Importance of Myelin in Electrical Signaling

• Myelin Sheath: Insulates axons, speeding up electrical transmission.

• Saltatory Conduction: Action potentials jump from one node of Ranvier to the next, enhancing conduction speed.

• Example of Deterioration: Multiple Sclerosis affects myelin integrity.

Chemical Signaling: Neurotransmitter (NT) Release

• Synaptic Transmission: Neurons communicate through synapses using neurotransmitters.

• NT Functionality:

  • NTs can either stimulate or inhibit neuron firing.

  • Glutamate: The primary excitatory neurotransmitter that promotes cell firing.

  • GABA: The primary inhibitory neurotransmitter that prevents cell firing.

Effects of Drugs on Synaptic Transmission

• Alteration of Neuron Function: Drugs can change synaptic transmission by affecting neurotransmitter functionality by:

  • Stimulating or inhibiting NT release.

  • Mimicking the effects of certain NTs.

  • Blocking the effects of NTs.

  • Interfering with NT reuptake (as seen with SSRIs and serotonin).

Basic Anatomy of the Brain

• Covers various brain structures including the cerebral cortex, thalamus, hypothalamus, and more.

Brain Anatomy

• Key structures include:

  • Occipital Lobe: Vision processing.

  • Temporal Lobe: Hearing and memory functions.

  • Parietal Lobe: Touch and spatial relations.

  • Frontal Lobe: Thought processes, planning, and movement.

  • Insular Cortex, Corpus Callosum, Basal Ganglia, Hippocampus, Amygdala, Thalamus, Hypothalamus, Cerebellum, Brain Stem.

Protection of the Brain

• Meninges: Protect the brain and spinal cord from injury.

• Cerebral Spinal Fluid (CSF): Provides additional protection for the brain.

Structures of the Brain Stem

• Functions of the Brain Stem: Controls survival functions such as heart rate, breathing, swallowing, etc.

  • Medulla Oblongata: Regulates heart rate and blood pressure.

  • Pons: Involved in sleep and arousal.

  • Midbrain: Contains thalamus and hypothalamus.

  • Reticular Formation: Manages sleep and arousal.

Thalamus and Basal Ganglia

• Thalamus: Acts as a gateway to the cortex; sensory inputs (vision, hearing, touch) first go to thalamus before reaching the neocortex.

• Basal Ganglia: Collection of structures involved in voluntary movement; degeneration is linked to Parkinson’s Disease.

Cerebellum

• Cerebellum Functions: Essential for balance, motor coordination, motor learning, and memory. Involved in language, cognition, and perception.

Limbic System

• Components of the Limbic System: Controls and regulates emotions; includes:

  • Hypothalamus: Regulates motivation and body functions (temperature, thirst, hunger, etc.).

  • Hippocampus: Critical for the formation of long-term memories.

  • Cingulate Cortex and Amygdala: Involved in emotional regulation, decision-making, and response to fear/aggression.

Reward Circuit of the Brain

• Brain Areas Involved in Addiction: Nucleus Accumbens (NAc), Ventral Tegmental Area (VTA), and prefrontal cortex are activated during pleasurable activities/addiction.

Corpus Callosum

• Function: Connects both cerebral hemispheres, enabling communication between them.

Split Brain Studies

• Split Brain Condition: Occurs when the corpus callosum is cut, allowing for research into hemispheric functions. Useful for reducing seizure activity.

• Research Pioneer: Mike Gazzaniga's work on split-brain operations reveals hemispheric specializations.

Neocortex Functionality

• Role of the Neocortex: Responsible for complex thoughts, perceptions, and behaviors.

• Cerebral Cortex Structure: Outermost layer with four lobes: occipital, parietal, temporal, frontal.

Lobe Functions of the Neocortex

• Frontal Lobe: Involved in planning, decision-making, and movement; contains primary motor cortex.

• Occipital Lobe: Process visual stimuli through the primary visual cortex.

• Temporal Lobe: Responsible for auditory processing and memory; has specialized areas for recognition of familiar faces.

• Parietal Lobe: Manages sensory input for touch, pain, and body position; involved in complex visual processing.

Prefrontal Cortex Understanding

• Phineas Gage Case Study: His accident led to significant personality changes, illustrating the prefrontal cortex's role in personality and decision-making.

• Lobotomy: A controversial procedure where parts of the prefrontal cortex are damaged to treat psychological issues, leading to lethargy and emotional flatness.

Somatosensory and Motor Functions in the Neocortex

• Detailed mapping of somatosensory and motor functions, highlighting areas associated with different body parts in the primary somatosensory cortex and primary motor cortex.

Smell and Taste in the Neocortex

• Olfactory Cortex: Processes smell, while gustatory cortex manages taste, both located in the frontal lobe.

Auditory Functions in the Neocortex

• Primary auditory cortex located in the temporal lobe, specialized for sound processing, with relation to cochlear frequencies.

Visual Functions in the Neocortex

• Involves multiple visual processing areas (V1, V2, V3, V4) associated with vision in the left and right visual fields and hemispheric processing.

Human Brain Imaging and Assessment Technologies

• EEG: Measures electrical activity in the brain; offers good temporal resolution but poor spatial resolution.

• PET: A method that assesses metabolic activity; offers good spatial but poor temporal resolution.

• MRI: Provides high-quality brain images using magnetic fields.

• fMRI: Measures brain activity changes by observing blood oxygen levels; offers good spatial but poor temporal resolution.

• Transcranial Magnetic Stimulation (TMS): Interferes with normal brain activity to study brain regions.

Visual Representation of Brain Activity

• Imaging technologies like PET and MRI visualize activity in various brain regions during actions such as seeing, hearing, speaking, and thinking.