Unit 1: Biological Bases of Behavior

Evolutionary Psychology

studying traits and behaviors that are common among all humans

Darwin’s theory of natural selection

individuals with advantageous, heritable traits suited to their environment are more likely to survive and reproduce, passing those traits to their offspring, which leads to populations changing and adapting over generations

Heredity (nature)

genetic mechanisms by which parents pass traits on to their children

Environment (nurture)

all the environmental variables that impact who we are

Epigenetics

the study of heritable changes in gene expression (active vs inactive genes) due from environmental causes

Methylation

process by which genes turn off/on due to protein interaction

Nervous system

body’s communication network that consists of all nerve cells

Central nervous system

• brain and spinal cord

• command center of the body

• responsible for processing information, coordinating responses, and regulating. bodily functions

peripheral nervous system

• all the nerves outside the brain/spinal cord

• communication network, transmitting sensory information from the body to the CNS

sensory pathway (in the nervous system)

carries signals from the sensory receptors in the body to the brain, relying on sensory neurons called afferent neurons that take in sensory information and transmit it to the brain and spinal cord

motor pathway (in the nervous system)

carries signals from the brain to muscles and glands, relying on efferent neurons that transmit signals away from the central nervous system (brain and spinal cord) to muscles, glands, and organs to initiate an action or response.

interneurons

neurons within the brain and spinal cord that lie between afferent and efferent neurons. act as relay station/translator between sensory input and coordinating a motor response

Autonomic nervous system

regulates involuntary and unconscious actions (e.g. breathing, blood pumping through veins, digestion, heartbeat, work of internal organs, etc.)

Sympathetic nervous system (autonomic)

arouses the body, expends energy (heart rate and blood pressure increase, pupils dilate, digestion slows)

parasympathetic nervous system (autonomic)

calming the body (decreases heart rate and blood pressure, increases digestion, decreases blood sugar, etc.)

somatic nervous system

includes nerves that transmit signals from your brain to the skeletal muscles to allow voluntary movement

neurons

specialized cell that serves as the building block of the nervous system, transmits electrical and chemical signals throughout the body

excitatory neurotransmitters

excite connecting neurons and cause them to fire, more action potentials are triggered (-70 mv to -30mv)

inhibitory neurotransmitters

prevent the next neuron from firing (hyperpolarization)

reuptake

neurotransmitters are taken back up into ending neuron to be used again

endocrine system

consists of glands that secrete chemical messengers called hormones into bloodstream. hormones travel to target organs where they bind to specific receptors, essential to communication throughout the body

pituitary gland

small pea-sized gland located at the base of the brain, often referred to as the “master gland” due to its central role in regulating hormone production and secretion throughout the body. critical role in coordinating hormonal activity and maintaining homeostasis

Adrenaline (H)

stress hormone

• from adrenal glands to bloodstream

• fight or flight

• too much: negative heart effects, hard to sleep, anxious

• too litte: limit body’s ability to respond properly in stressful situations

oxytocin (H)

pregnancy, childbirth, reproduction, breastfeeding

• human bonding especially maternal/romantic

• hypothalamus and pituitary gland

• too much: oversensitive

• too little: mental health disorders (depression, anxiety, eating)

Ghrelin (H)

Grows hunger

• released when stomach is empty

• energy regulation: burning calories and storing fat

• in the gut: secreting gastric acid, gastric mobility, pancreatic protein input

• too much: increased hunger and appetite, overeating, weight gain

• too little: reduced appetite/hunger, not enough nutrition

Melatonin

sleep hormone

• produced by the. brain

• responsible for timing circadian rhythm

• produced by pineal gland

• production triggered by light

• too much: seasonal affective disorder, sleepy during daytime

• too little: insomnia, sleeping issues

Leptin

lessens hunger

• maintains normal weight

• regulating hunger+feeling full

• amount in blood directly relates to how much body fat

• brain stem and hypothalamus to regulate hunger and energy balance

• immune system, bone formation

• too much: obesity

• too little: state of starvation- increased hunger, reduced energy expenditure

Serotonin (NT)

happiness and feeling good

• calm, focused, emotionally stable

• too much: hallucinations

• too little: depression, mood disorders, OCD

Dopamine (NT)

pleasure and reward

• motivated, satisfied, excited

• addictions

• too much: schizophrenia, addiction

• too little: parkinson’s, depression

Norepinephrine (NT)

fight or flight

• alerts to danger, increases arousal and attention

• too much: anxiety

• too little: depression, mood disorders

GABA (NT)

calm and relax

• increases sleepiness, decreases anxiety

• calms CNS

• too much: overly sleepy, sedated, normal functioning impaired

• too little: anxiety and insomnia

Endorphins (NT)

• alleviate pain, lower stress, improve mood and well-being

• eating, exercise, sex

• too much: ignoring signals of pain, risking injury

• too little: feeling significant pain

Glutamate (NT)

• important for memory, cognition, mood regulation

• metabolism is important for functioning

• too much: overstimulated brain, seizures

• too little: insomnia, concentration problems, mental exhaustion

Acetylcholine (NT)

muscle contraction, memory, learning, and autonomic functions like heart rate and blood pressure

• too much: blurred vision, nausea, diarrhea, slow heart rate, muscle weakness that can progress to paralysis, and difficulty breathing. Severe cases can result in respiratory depression, coma, and even death

• too little: problems with your muscles, including weakness, paralysis, and conditions like myasthenia gravis, and negatively impact brain function, leading to memory issues, difficulty learning, and confusion, as seen in Alzheimer's disease

Substance P (NT)

transmitting pain signals

• released by nerve cells

• inflammation and mood regulation

• too much: chronic pain

• too little: reduced sensitivity to pain

Cerebral Cortex

the outer layer of the brain, responsible for higher-order functions like thinking, reasoning, decision-making, language, memory, and voluntary movement.

Brain Stem - Medulla Oblongata

regulates vital involuntary functions such as heart rate, breathing, blood pressure, and swallowing. It also controls reflexes like coughing and sneezing.

Brain Stem - Reticular Activating System

network in the brainstem that regulates wakefulness, alertness, and attention. It filters sensory information and modulates arousal levels, sleep-wake cycles, and consciousness.

Brain Stem - Pons

relay between the cerebellum and cerebral cortex. It coordinates breathing, sleep, facial movements, and eye movements, and plays a role in dreaming and posture (body positioning)

Cerebellum

coordinates voluntary movements, balance, posture, and motor learning. It fine-tunes motor actions and contributes to some cognitive functions like attention and language. “little brain'“

Limbic System - Thalamus

Acts as a relay station for sensory and motor signals, directing them to appropriate cortical areas. It processes sensory input (except smell) and is involved in regulating consciousness, sleep, and alertness.

Limbic System- Hypothalamus

small region below the thalamus that regulates autonomic functions, including body temperature, hunger, thirst, sleep, and hormone release. It links the nervous system to the endocrine system via the pituitary gland.

reward center of the brain, regulates hunger/thirst, body temp and sex

Endocrine System- Pituitary Gland

Known as the "master gland," it produces hormones that regulate other endocrine glands, controlling growth, metabolism, reproduction, and stress responses. It’s influenced by the hypothalamus.

Limbic System- Hippocampus

Critical for forming and retrieving memories, particularly long-term declarative memories (facts and events). It’s also involved in spatial navigation and learning.

Limbic System- Amygdala

Processes emotions, especially fear and pleasure, and is key in emotional memory formation, threat detection, and the fight-or-flight response. It modulates stress and emotional behavior.

Corpus Callosum

A thick band of nerve fibers connecting the left and right cerebral hemispheres, enabling communication between them for coordinated cognitive and motor functions.

lots of axons