EPPP Exam Prep Topics: Biological bases of behavior

Electroencephalography (EEG)

• It measures brain activity to assess overall brain function. It is used to diagnosis epilepsy & sleep disorders.

Neuroangiography

• It is an invasive imaging technique to use contrast to visualize blood vessels.

• Wada Test

  • It Is using during the imaging technique to idenitity language abilities, which temporarily disables 1 hemisphere of the brain.

Anxiolytics

• Used to alleviate anxiety, targeting the CNS to promote relaxation & reduce overactivity responses.

Brain Stem

• Regulates vital life-sustaining functions (e.g., breathing; heart rate). It is the primary communication between the brain & the body.

Diencephalon

• It includes the thalamus & hypothalamus, which relays sensory information. 

• It is a crucial relay and control center for sensory, motor, and autonomic functions, linking the nervous system to the endocrine system to regulate everything from sleep and appetite to consciousness and hormone release

Cerebellum

• It coordinates motor movements, maintains balance, regulates posture & muscle tone for smooth & precise physical activity.

Apraxia

• It involves difficulty with motor tasks and affects purposeful movements.

Paresis

• Partial loss of muscle strength.

• It is an incomplete paralysis often stemming from neurological damage to the brain, spinal cord, or nerves.

• It manifests as weakness in limbs, face, or body, frequently accompanied by numbness, tingling, or balance issues.

• Common causes include stroke, multiple sclerosis, spinal cord injuries, and peripheral neuropathy

Theory of Mind

• Concept that refers to understanding that others can have different beliefs or views about the same event. It is essential for interpreting behavior & fostering effective social interactions. 

• This cognitive ability develops from childhood (ages 3-5), enabling empathy, social navigation, and interpretation of behavior, including understanding false beliefs.

• It includes first-order tasks (what someone thinks) and second-order tasks (what one person thinks about another's thoughts).

Vascular neurocognitive disorder

• It results from small strokes & has an abrupt onset & stepwise progression.

• It is the 2nd most common neurocognitive disorder.

REM Sleep

• As the night progresses, it becomes more prominent and deep sleep (stages 3 & 4) becomes less frequent.

Pseudodementia

• It is a reversible cognitive impairment caused by psychiatric conditions, most commonly depression.

• Those with this disorder complain about memory loss (whereas people with neurocognititve disorders often lack the insight). It features a faster onset.

• Patients with it often exhibit "don't know" answers and inconsistent effort, while dementia patients try hard but fail.

• Often affects recent & remote memory equally (NCD/Alzheimer’s typically presents with profound, early loss of short-term memory).

• Differences in braing imaging results (no significant atrophy to hippocampus)

Dopamine

• It regulates thought, movement (motor control), reward system, & emotion.

Glutamate

• Primary excitatory transmitter, crucial for learning and memory.

GABA

• Primary inhibitor, stabilizing brain activity.

Serotonin

• Modulates mood, sleep, and appetite.

Acetylcholine

• Stimulates muscle contraction and the autonomic nervous system.

Norepinephrine

• Controls alertness, stress response, and arousal.

Similarities between Neurotransmitters

Action: 

• All are chemical messengers released by neurons to communicate with other neurons, muscles, or glands.

Mechanism: 

• They operate by binding to specific receptors on the post-synaptic neuron.

Regulation: 

• All are regulated by reuptake (reabsorption) or enzymatic degradation to prevent continuous stimulation.

Impact: 

• Imbalances in any of these are linked to significant neurological or psychiatric conditions

  • e.g., Alzheimer's, anxiety, depression, Parkinson's

Differences between Neurotransmitters

Function: 

• Excites vs Inhibits:

  • Glutamate is primarily excitatory (promotes action)

  • GABA is primarily inhibitory (slows action)

• Mood & Behavior:

  • Dopamine (reward/movement)

  • Serotonin (mood)

  • Acetylcholine (muscle/autonomic)

Chemical Structure: 

• Catecholamines (derived from tyrosine)

  • Dopamine & norepinephrine

• Monoamine (derived from tryptophan)

  • Serotonin

• Amino acids

  • Glutamate and GABA

Brain Distribution: 

• Glutamate is widespread throughout the cortex,

• Systems like serotonin and dopamine originate from specific, smaller brain regions

  • e.g., substantia nigra for dopamine

Acetylcholine vs  Norepinephrine 

System Function: 

• Acetylcholine is the primary transmitter of the parasympathetic nervous system (calm, rest, digest)

• Norepinephrine is the primary transmitter of the sympathetic nervous system (fight-or-flight).

Degradation: 

• Acetylcholine is rapidly broken down by acetylcholine esterase in the synapse.

• Norepinephrine is broken down by enzymes or reuptaken into the presynaptic neuron.

Heart Regulation: 

• Acetylcholine (acting via muscarinic receptors) decreases heart rate and acts as an antagonist to NE-induced cardiac activity.

• Norepinephrine increases heart rate and contraction strength.

Effects on Target Tissues: 

• Acetylcholine generally facilitates muscle contraction and digestion

• Norepinephrine enhances alertness, energy mobilization, and blood flow to muscles.

Key Similarities:

Regulation of Functions: 

• Both play crucial roles in regulating involuntary functions, often acting in opposition on the same organs.

Neuroplasticity: 

• Both modulate neural plasticity and affect cognitive functions such as learning and memory.

Glutamate vs Dopamine

Function Differences: 

• Glutamate is excitatory (depolarizing), acting as the brain's main "on" switch.

• Dopamine is primarily a modulator influencing the intensity and interpretation of neural signals.

Differences in the Roles in Learning: 

• Glutamate signaling is essential for reward-related behavior

• Dopamine signaling is specifically necessary for learning about aversive stimuli.

Interaction: 

• Glutamate often regulates the release of dopamine → Dopamine can modulate glutamate-induced excitation.

Psychiatric Relevance: 

Dysfunction in both systems is strongly implicated in schizophrenia, addiction, and mood disorders.

4 types of nerves

Afferent Nerves 

• → Sensory nerves that travel from skin & organs (Peripheral receptors) to the CNS for the sense of touch, pain, & temperature.

• AFTER you touch something, a signal is sent to the brain that it is hot.

• While they often send electrical signals, they also release neurotransmitters such as glutamate (for general touch/pressure) and Substance P (for pain) into the spinal cord or brainstem to relay information.

Efferent Nerves

• → Motor nerves start in the brain or spinal cord & exits CNS to trigger muscle movement or gland secretion.

• They release Acetylcholine at the neuromuscular junction, which binds to receptors on skeletal muscles to trigger movement.

Cranial Nerves

• → They can be Afferent, Efferent, or a mix of both nerves in the brain or brainstem that control head & neck functions (e.g., vision, taste, facial expressions).

• They primarily release Acetylcholine to inhibit the heart muscle. 

Spinal Nerves

• → They are a combination of Afferent & Efferent nerves (mixed nerves) that originate in the spinal cord & control body functions below the neck (e.g., limb movement, skin sensation)

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Key Similarities:

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Peripheral Nervous System (PNS): 

• All these nerve types are part of the PNS, acting as the communication lines between the CNS and the rest of the body.

Common Goal: 

• They work together in reflex arcs and voluntary actions;

  • Afferent nerves sense a hot surface & Efferent (motor) nerves tell your hand to pull away.

Structural Units: 

• All are composed of bundles of axons (nerve fibers) protected by connective tissue.

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Critical Differences:

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Cell Body Location:

• Afferent cell bodies are usually in ganglia outside the CNS (e.g., dorsal root ganglia).

• Efferent/Motor cell bodies are typically located within the CNS gray matter (e.g., ventral horn of the spinal cord). 

Functional vs. Anatomical: 

• "Afferent" & "Efferent" are functional classifications based on signal direction.

• "Cranial" and "Spinal" are anatomical classifications based on where the nerve physically attaches to the CNS.

Nervous Systems in the Body

• Central Nervous System (CNS) 

  • It is the "command center" of the body. It is the actual processor that integrates information & makes decisions.

    • Regeneration is very limited (damage is often permanent).

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• It takes electric signals (“raw data" from your afferent nerves) & interprets it.

• It decides how to react, then sends the "command" to efferent nerves to move your muscles.

• It uses a vast array of chemicals for complex processing:

  • Glutamate: 

    • Most abundant excitatory neurotransmitter

    • Vital for memory and learning.

  • GABA: 

    • The primary inhibitory neurotransmitter

    • Acts as a "stabilizer" to prevent overexcitation.

  • Glycine: 

    • The main inhibitory neurotransmitter in the spinal cord.

  • Dopamine: 

    • Involved in reward, motivation, and motor control.

  • Serotonin: 

    • Regulates mood, sleep, and appetite. 

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• PNS (Peripheral Nervous System): 

  • Acts as the communication bridge between the CNS & the rest of the body.

    • It contains motor & sensory nerves that allow you to interact with your environment.

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• Somatic Nervous System: 

  • Responsible for conscious control.

  • It transmits sensory signals to the CNS & carries motor commands to skeletal muscles.

  • It also manages involuntary reflex arcs (like pulling your hand from a hot stove).

  • Uses only Acetylcholine.

    • Motor neurons release it directly onto skeletal muscles to cause movement.

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• ANS (Autonomic Nervous System): 

  • Operates below the level of consciousness to maintain homeostasis.

    • It adjusts internal functions (blood pressure, body temperature, and stomach secretions) without you having to think about it.

    • Both sympathetic and parasympathetic) release acetylcholine.

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• Sympathetic Nervous System: 

  • The "gas pedal" of the ANS.

    • When you are stressed or in danger, it increases your heart rate, dilates your pupils, and redirects blood to your muscles to prepare for immediate action.

      • It typically releases norepinephrine at the target organ to trigger “flight or flight” responses.

      • Adrenaline (Epinephrine) is primarily released by the Adrenal Medulla into the blood to sustain a full-body stress response.

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• Parasympathetic Nervous System:

  • The “break” of the ANS.

    • It works to "downregulate" your body, returning systems to their standard activity levels once the stressor is gone

      • • The Vagus Nerve: This is the "superhighway" of the PSNS, making up about 75% of all parasympathetic fibers from the brainstem, heart, lungs, & most of the digestive tract.

      •  It uses acetylcholine for both its pre- and post-ganglionic signaling. Because it relies on ACh, its fibers are often called cholinergic

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• Peripheral Nervous System (PNS): 

  • “Parent” It is the overarching category for all nerves outside the brain and spinal cord.

    • Somatic Nervous System (SoNS): A branch of the PNS.

    • ANS (Autonomic Nervous System): A branch of the PNS.

      • Sympathetic Nervous System: A sub-division of the ANS

      • Parasympathetic Nervous System (PSNS): A sub-division of the ANS

• They are primarily differentiated by where they start in the brain and how they affect awareness and movement.

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Focal Seizures

• The person remains fully conscious and alert. They may experience unusual sensations (auras), like a strange taste or sudden emotion.

• Awareness is affected, and the person may seem confused, dazed, or in a "dream-like" state.

  • They often perform repetitive, purposeless movements called automatisms, such as lip-smacking or picking at clothes.

• Focal to Bilateral Tonic-Clonic: 

  • A seizure that starts in one area and then spreads to involve both sides of the brain, leading to a full convulsion.

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Generalized Onset Seizures

These affect both sides of the brain simultaneously from the very start.

• Absence Seizures (Non-motor): Common in children, these involve a brief (5–10 second) "staring spell" where the person stops what they are doing and appears to "zone out". Previously known as petit mal.

• Tonic-Clonic (Motor): What most people recognize as a "grand mal" seizure. It involves a "tonic" phase (muscle stiffening) followed by a "clonic" phase (rhythmic jerking) and loss of consciousness.

• Atonic Seizures: Known as "drop attacks," these cause a sudden loss of muscle tone, making the person go limp and often fall to the ground.

• Myoclonic Seizures: Brief, shock-like jerks or twitches of a muscle or group of muscles.