Biology and Behavior Comprehensive Study Guide

Neuroscience and Biological Psychology Foundations

• Neuroscience involves the comprehensive study of the brain and the nervous system. It is a multidisciplinary field that draws upon various subjects, including psychology, to understand the biological underpinnings of behavior and mental processes.

• Biological psychology, a specialized subfield within psychology, focuses specifically on how the brain and other biological systems influence human behavior. This field seeks to understand the physical and chemical factors that drive actions and cognitive functions.

• The Nervous System is defined as a communication network that conveys messages throughout the body using sophisticated electrical and chemical processes. It is composed of three primary components: the brain, the spinal cord, and the nerves.

• Neurons are specialized cells within the nervous system designed to transmit electrical and chemical signals. The human brain contains approximately $100 \times 10^9$ (100 billion) neurons, which are interconnected by an estimated $100 \times 10^{12}$ (100 trillion) links.

Communication Between Neurons and the Synapse

• Neurotransmitters are the chemical messengers used by neurons to communicate with one another at the synapse. This communication is essential for all nervous system functions.

• Receptor Sites are specific locations on the receiving side of the synaptic gap where neurotransmitters attach. The process follows a "lock and key" principle, meaning a neurotransmitter must fit into a corresponding receptor site to convey its message effectively.

• Reuptake is a process that occurs when neurotransmitters are reabsorbed by the sending axon terminal after they have completed their message delivery. This helps regulate the amount of chemicals in the synaptic gap.

Detailed Profiles of Specific Neurotransmitters

• Acetylcholine

  • Functions: It relays messages from neurons to muscles to enable movement. It is also heavily involved in memory and learning.

  • Imbalances: An excess of acetylcholine can lead to muscle spasms, while a deficiency can result in paralysis. Notably, low levels of acetylcholine in the brain are linked to Alzheimer’s disease, characterized by memory, language, and thinking problems.

  • Additional Fact: The anti-wrinkle treatment Botox works by paralyzing facial muscles. It prevents the activity of acetylcholine, which would otherwise enable muscle movement.

• Glutamate

  • Functions: As an excitatory neurotransmitter, it "kicks neurons into action" or makes them fire. It influences most brain cells and is critical for learning, memory, and thinking.

  • Imbalances: High levels are linked to strokes, while low levels may contribute to schizophrenia symptoms.

  • Additional Fact: It is a close chemical relative to the food additive monosodium glutamate (MSG). Despite urban myths, claims that MSG causes brain damage are not supported by solid scientific data.

• GABA (Gamma-Aminobutyric Acid)

  • Functions: An inhibitory neurotransmitter that acts as a brake on neuron firing. It regulates sleep-wake cycles and helps control fear and anxiety.

  • Imbalances: Disruptions in GABA activity are linked to disrupted sleep and heightened anxiety or fear responses.

  • Additional Fact: Anti-anxiety medications, including Valium and Xanax, work by enhancing the effects of GABA.

• Norepinephrine

  • Functions: Prepares the body for stressful situations. It is an excitatory neurotransmitter that regulates arousal, sleep, attention, and alertness.

  • Imbalances: High levels lead to overarousal, hypervigilance, and difficulty focusing or thinking clearly.

• Endorphins

  • Functions: These are natural opioids produced by the body. They regulate the activity of other neurotransmitters and are released in response to pain to reduce discomfort and elevate mood.

  • Factors: Production of endorphins increases with brisk exercise. Low endorphin activity results in a reduced ability to manage pain and stress.

• Serotonin

  • Functions: Regulates appetite, mood, aggression, sleep, and breathing. It supports emotional and physiological balance.

  • Imbalances: Atypical serotonin activity is linked to depression. SSRIs (Selective Serotonin Reuptake Inhibitors) like Prozac and Zoloft boost serotonin levels by preventing reuptake.

  • Additional Fact: Physical exercise may boost serotonin activity, leading to improved mood and decreased depressive symptoms.

• Dopamine

  • Functions: Supports attention and focus, facilitates learning through rewards, and regulates body movements.

  • Imbalances: Drug abuse (e.g., cocaine, amphetamines) overstimulates the brain’s pleasure circuit, potentially reducing the ability to enjoy non-drug rewards. Parkinson’s disease involves the deterioration of dopamine-producing neurons, causing tremors and stiffness.

• Oxytocin

  • Functions: Acts as both a neurotransmitter and a hormone. It is involved in social bonding and romantic love, increasing during the early stages of relationships.

  • Imbalances: Low levels are associated with difficulty forming social bonds, reduced trust, impaired romantic attachment, and increased social anxiety.

Structure of the Nervous System

• Central Nervous System (CNS): This is the major component consisting of the brain and the spinal cord.

• Peripheral Nervous System (PNS): This part connects the CNS to the rest of the body. It consists of neurons outside the CNS, bundled into nerves that act like electrical cables.

  • Sensory Neurons: Receive environmental information (sights, sounds, temperature) and convey it to the brain.

  • Motor Neurons: Carry information from the CNS to the body to produce movement.

• Spinal Cord Functions: It is a bundle of neurons that facilitates communication between the brain and the PNS. It receives information from the body to send to the brain and delivers instructions from the brain to the body. Blockages in this pathway prevent command signals and sensory communication.

Branches of the Peripheral Nervous System

• Somatic Nervous System: Controls voluntary (conscious) movements. It includes sensory nerves (gathering data on pressure/pain) and motor nerves (carrying instructions to skeletal muscles for walking, writing, etc.).

• Autonomic Nervous System: Operates automatically outside of conscious control to regulate involuntary functions like heartbeat and digestion. It is split into two divisions:

  • Sympathetic Nervous System ("Fight or Flight"): Prepares the body for action. It increases heart and breathing rates, dilates pupils, slows digestion, decreases saliva, and relaxes the bladder.

  • Parasympathetic Nervous System ("Rest and Digest"): Conserves energy and relaxes the body. It decreases heart and breathing rates, constricts pupils, stimulates digestion, increases saliva, and contracts the bladder.

Brain Regions and Their Structures

• The Hindbrain: Responsible for fundamental life-sustaining processes.

  • Pons: Regulates respiration, sleep-wake cycles, and coordinates movement between the left and right sides of the body.

  • Medulla (Medulla oblongata): Controls breathing, heart rate, blood pressure, swallowing, coughing, sneezing, and vomiting.

  • Cerebellum: Manages muscle coordination, balance, and higher-order cognitive processes like emotional control and language processing.

• The Midbrain: Involved in levels of arousal and generating movement patterns in response to sensory input.

  • Reticular Formation: A neuron network that controls arousal and analyzes sensory data heading to the cortex.

• The Forebrain: The largest part of the brain, including the cerebrum, cerebral cortex, and limbic system.

The Cerebrum and Hemispheric Lateralization

• The Cerebrum controls muscle functions, speech, thought, emotions, reading, writing, and learning. It is divided into two hemispheres linked by the Corpus Callosum, a thick band of nerve fibers that allows them to communicate.

• Lateralization: The tendency for each hemisphere to excel at different tasks.

  • Left Hemisphere: Dominant in language processing, speech production, and language comprehension. It handles language for $95 \%$ to $99 \%$ of right-handed people and $70 \%$ of left-handed people.

  • Right Hemisphere: Excels in visual-spatial tasks, identifying mirror images, mentally rotating images, recognizing faces, processing emotions, and directing attention.

• Split-brain Operations: Surgery where the corpus callosum is severed to treat severe seizures. Research shows that while the hemispheres can act independently (e.g., being unable to verbally identify an image in the left visual field while still identifying it nonverbally), they normally work as a team.

The Cerebral Cortex and the Four Lobes

• The Cerebral Cortex is the outermost wrinkled layer of the cerebrum, responsible for higher mental functions. If unfolded, it would measure $5$ to $6.5$ feet long.

• Frontal Lobe: Located at the front. Handles higher-level cognitive activities, social behavior, and personality. Phineas Gage (1848) suffered personality changes after a $3$-foot tamping rod went through his frontal lobe.

• Parietal Lobe: Located at the top/back of the head. Manages tactile processing (touch, pain) and visual-spatial reasoning. Albert Einstein's parietal lobe was noted to be $15 \%$ larger than average.

• Temporal Lobe: Located on the sides. Processes auditory stimuli, language comprehension, and face recognition. Contains the auditory cortex.

• Occipital Lobe: Located at the lower back. Contains the primary visual cortex for interpreting color, shape, and motion.

• Association Areas: Found in all four lobes; they integrate information across the brain to support complex behaviors and abstract thinking.

The Limbic System

• This system is located beneath the cerebral cortex and regulates emotions, motivation, and memory, as well as basic drives (hunger, sex, aggression).

• Thalamus: Center of the limbic system; processes and relays sensory information (except smell) to the cortex. Known as the "air traffic control tower."

• Hypothalamus: Maintains homeostasis (blood pressure, temperature, fluid balance) and regulates appetite, sexual arousal, and sleep-wake cycles.

• Amygdala: Located at the tip of the temporal lobe; processes fear and aggression and stores emotional memories. It has reflexive and voluntary threat response routes.

• Hippocampus: Forms new memories from experiences and is a site of neurogenesis (the generation of new neurons).

The Endocrine System

• The endocrine system uses glands to release Hormones into the bloodstream. Unlike neurotransmitters (which are fast and short-lasting), hormones are slower, longer-lasting, and have widespread effects. While nerve impulses can exceed $250 \, mph$, hormones take minutes to reach targets.

• Hypothalamus: Links the nervous system to the endocrine system and monitors body conditions.

• Pituitary Gland: Known as the "master gland"; it influences all other glands and secretes Growth Hormone (GH) for bone/muscle growth and metabolism.

• Thyroid Gland: Secretes Thyroxin (T4) to regulate metabolism and heart rate.

• Adrenal Glands:

  • Cortex: Secretes Aldosterone (salt balance) and Cortisol (stress management, metabolism, immune suppression).

  • Medulla: Secretes Epinephrine and Norepinephrine for the fight-or-flight response.

• Pineal Gland: Produces Melatonin to regulate the sleep-wake cycle.

• Pancreas: Produces Insulin (lowers blood sugar) and Glucagon (raises blood sugar).

• Ovaries/Testes: Produce sex hormones (Estrogen/Progesterone in females; Testosterone in males) for reproductive function and sex characteristics.