Biopsychology

  • Neurotransmission at the synapse

    • Neurotransmitters travel across the synapse and bind to receptor sites on the postsynaptic membrane (dendrites).
    • They fit like a key when the right neurotransmitter matches the receptor (specificity).
    • The postsynaptic cell responds to the neurotransmitter based on receptor activation.
    • After signaling, the neurotransmitter is (a) broken down by enzymes, (b) reabsorbed back into the presynaptic axon terminal via reuptake. Reuptake is the process by which neurotransmitter pieces are taken back across the synaptic gap to the presynaptic membrane for reuse or breakdown.
    • Key terms: synapse, postsynaptic membrane, receptor sites, enzyme breakdown, reuptake.

  • The Nervous System: Central, Peripheral, and Autonomic divisions

    • The nervous system is divided into Central Nervous System (CNS) and Peripheral Nervous System (PNS).
    • PNS splits into Somatic Nervous System and Autonomic Nervous System (ANS).
    • ANS maintains involuntary basic life processes.
    • Somatic nervous system conveys information to the CNS (sensory and motor signals for voluntary control).

  • The Autonomic Nervous System (ANS)

    • ANS (abbreviated) consists of two divisions that handle differently: sympathetic and parasympathetic.
    • Sympathetic division: geared toward threat activation (fight or flight).
    • Parasympathetic division: maintains bodily functions and regulates energy use (rest and digest).
    • In class examples, typical states: at rest, parasympathetic is more active; during perceived threat, sympathetic activation occurs (e.g., fear, anxiety, public speaking).
    • Activation changes include heart rate, respiration, digestion, saliva, sweating.
    • The sympathetic response prepares muscles to move quickly, increases heart rate and respiration, and diverts energy away from digestion to muscles and the brain.
    • The parasympathetic response reduces energy expenditure, slows heart rate, enhances digestion, and promotes rest.
    • It takes about five seconds to initiate a sympathetic response after perceiving a threat.
    • Long-term or chronic stress can keep the sympathetic system in a higher state of arousal, which is not generally good for health and can wear the body out over time.

  • Real-world and classroom examples of ANS activation

    • Threat scenarios (bear on a trail) provoke sympathetic arousal: faster heart rate, faster respiration, energy redirected from digestion, mouth goes dry, sweating.
    • Classroom speaking as a threat: similar sympathetic arousal (dry mouth, pounding heart).

  • Brain basics and neuron counts

    • The brain is densely packed with neurons: about N≈1011N \approx 10^{11}(100,000,000,000) neurons.
    • Each neuron can send/receive messages to/from thousands of other neurons.
    • Each cubic inch of cortex contains about 10,000 miles of neuron connections10{,}000 \text{ miles of neuron connections}, illustrating the extensive connectivity.
    • An excited neuron can fire up to about fmax≈1000texttimespersecondf_{max} \approx 1000 \\text{times per second} (≈ 1000 Hz).
    • This immense connectivity supports rapid processing required for basic function and complex cognition.

  • Major brain divisions and structural landmarks (overview)

    • Longitudinal fissure: the deep groove running along the midline separating the left and right hemispheres.
    • Midsagittal section: cuts down that line to reveal internal brain structures; corpus callosum connects the two hemispheres and allows communication between them.
    • Corpus callosum: a band of nerve fibers that facilitates interhemispheric communication; splitting it (callosotomy) can prevent seizures from spreading across both hemispheres.
    • Contralateral control: the left hemisphere largely controls the right side of the body and vice versa.
    • Lateralization of function: some cognitive functions are more dominant in one hemisphere (e.g., language is typically left-lateralized for many people; left-handedness can be associated with different patterns of lateralization).

  • Forebrain, limbic system, and thalamus

    • Forebrain is the largest, evolutionarily newest part of the brain and contains multiple structures including the cerebral cortex, limbic system, and thalamus.
    • Thalamus: sensory relay station; routes sensory information from the peripheral nervous system to the appropriate cortical areas for processing; integrates information from different senses to create a coherent percept.
    • Olfactory bulbs (under the brain): involved in smell; chemical information from the nose is processed here and interacts with limbic structures.
    • Limbic system: mediates motivated behaviors and emotion; critical for memory and survival-related drives.
    • Amygdala: when stimulated (electrically) in animals like rats, can evoke aggressive or fearful responses depending on the exact area stimulated.
    • Hippocampus: involved in memory; also linked to hunger, thirst drives; contributes to memory formation.
    • Other limbic roles: weight control and temperature regulation.
    • Motivated behaviors that support survival include hunger, thirst, and sex drive.

  • The cerebral cortex and cortical lobes

    • Cortex overview: the outermost layer of the brain (cerebrum) responsible for higher-order functions like thought, reasoning, and planning.
    • Four main lobes: Frontal, Parietal, Occipital, Temporal.
    • Frontal lobe (anterior, evolutionarily newer): contains the primary motor cortex, controlling voluntary muscle movements (over 600 muscles).
    • Primary motor cortex: controls voluntary movement; lesion or disruption affects motor execution.
    • Frontal lobe also supports human-specific capabilities such as social behavior, abstract thinking, goal-setting, and planning.
    • Parietal lobe: contains the primary somatosensory cortex, processing touch, temperature, pain, and other body sensations.
    • Primary somatosensory cortex: maps body areas to specific cortical regions; directionally opposite body parts controlled (from the brain’s somatotopic map).
    • Relationship of motor and sensory cortices: adjacent areas in the frontal lobe (motor cortex) and parietal lobe (somatosensory cortex) correspond to specific body parts; a given body part is represented in a particular cortical region.
    • Left-right cortical organization and the idea of contralateral control extend to how movements and sensations are processed and executed.
    • Cerebral lateralization and language: language functions are often lateralized to the left hemisphere in most people; left-handed individuals may show different patterns but not universally.
    • Cerebral cortex size and brain evolution: the cortex is highly folded; flattening the cortex would still be large, but evolutionary advantage is gained by increased surface area via folding rather than gross brain size increase.
    • Cerebellum (underlying the posterior brain): motor control and coordination; highly susceptible to alcohol; impairment of balance and coordinated movement is a sign of cerebellar disruption.
    • Medulla and pons are part of the hindbrain, but discussed here as structures close to brainstem control in basic life functions.

  • Hindbrain, midbrain, and brainstem structures

    • Hindbrain includes the medulla, pons, and cerebellum.
    • Medulla: controls vital life-sustaining functions (heart rate, respiration) and reflexes (vomiting, coughing, sneezing) to protect the body from dangerous substances; damage to this area can be life-threatening due to its role in basic autonomic control.
    • Pons: acts as a bridge between the spinal cord and the brain; involved in relay of signals and various regulatory functions.
    • Cerebellum: involved in motor control and coordination; one of the first regions affected by alcohol; impairment leads to lack of balance and impaired coordinated movement.
    • Midbrain: often referred to as containing the substantia nigra (the “black substance”); important in motor control and reward pathways.

  • Studying the brain: methods and limitations

    • Studying brain function through natural or induced brain damage (e.g., Phineas Gage) reveals how specific brain areas contribute to behavior and personality.
    • Surface electrical activity measurements provide information about which cortical areas are more active during tasks but have limited access to deeper structures (thalamus, hypothalamus, amygdala).
    • Brain imaging techniques mentioned:
    • PET scan (Positron Emission Tomography): measures metabolic activity by tracking a radioactive tracer; more active regions show higher tracer uptake because they use more energy and blood flow.
    • MRI (Magnetic Resonance Imaging): provides high-resolution images of brain structure; shows anatomy and structural details without radiation.
    • fMRI (functional MRI): combines structure and function; shows both brain anatomy and functional activity by detecting blood flow changes related to neural activity.
    • EEG and other measures were implied as available for surface electrical activity, but deeper structures are best assessed with imaging modalities like MRI/PET/fMRI.

  • How the content connects to broader concepts and implications

    • The interaction of neurotransmission and the ANS ties into stress responses, anxiety, and physiological regulation.
    • Understanding lateralization and contralateral control informs about handwriting (which hemisphere controls which hand) and language processing patterns.
    • The limbic system’s role in motivated behaviors links to basic drives (hunger, thirst, sex) and emotional memory, with relevance to health, addiction, and emotional regulation.
    • The impact of alcohol on the cerebellum highlights how substances disrupt motor coordination and broad brain function.
    • The idea of using brain scans to infer function (PET, fMRI) versus structure (MRI) reflects the difference between brain anatomy and brain activity, informing about cognitive neuroscience methods and limitations.

  • Study and test-taking tips mentioned in the material

    • The instructor provides a study guide and practice questions posted on Canvas; completing these can help anticipate exam question formats.
    • The content emphasizes understanding concepts and connections rather than memorizing isolated facts; focus on functional roles, relationships, and examples (e.g., fight/flight, language lateralization).

  • Key formulas and numerical references (LaTeX format)

    • Number of neurons in the human brain: N≈1011N \approx 10^{11}
    • Maximum firing rate of an excited neuron: fmax≈103 Hzf_{max} \approx 10^{3} \text{ Hz}
    • Cortical connectivity scale example: approximately 10,000 miles10{,}000 \text{ miles} of neuronal connections per cubic inch of cortex
    • Note: All other numerical details are qualitative in the transcript, but these quantitative points help illustrate brain scale and activity

  • Quick glossary of terms to remember

    • Synapse, postsynaptic membrane, receptor sites, reuptake, enzyme breakdown
    • Central Nervous System (CNS), Peripheral Nervous System (PNS)
    • Somatic nervous system, Autonomic nervous system (ANS)
    • Sympathetic division, Parasympathetic division
    • Longitudinal fissure, corpus callosum, contralateral control, lateralization
    • Thalamus, Olfactory bulbs, Amygdala, Hippocampus
    • Limbic system, Frontal lobe, Primary motor cortex, Primary somatosensory cortex
    • Parietal, Occipital, Temporal lobes
    • Hindbrain (Medulla, Pons, Cerebellum), Midbrain (Substantia nigra), Forebrain
    • PET, MRI, fMRI, EEG (surface electrical activity)