Biological Basis of Behavior - Comprehensive Study Notes
What Is the Nervous System?
The nervous system is the body’s control center.
It includes the brain, spinal cord, and nerves.
Responsibilities:
Thoughts and emotions
How we move, react
Regulation of heart beating
It allows us to take in information from the world and respond to it.
Example: When giving a speech, feeling nervous and having a faster heart rate shows the nervous system reacting to emotions.
The Two Main Parts of the Nervous System
Central Nervous System (CNS)
Includes the brain and spinal cord
Peripheral Nervous System (PNS)
Includes all nerves outside the CNS
Neurons: The Messengers
Neurons are the tiny messengers of the nervous system.
They send and receive signals throughout the body.
Structure of a neuron (often likened to a tree):
Dendrites (branches) — catch messages from other cells
Axon (trunk) — carries the message to the other end
Axon terminals (roots) — pass the message on to the next cell
Analogy: neuron as a little messenger tree: branches receive, trunk delivers, roots share.
Example: When a classmate taps my shoulder, skin neurons send a message to the brain.
Neural Impulses – The Signals
Neural impulses are electrochemical signals traveling through neurons.
Speed range: (depends on neuron type).
They are slower than electricity in wires but fast enough to send messages quickly (e.g., from toe to brain in a fraction of a second).
Example: Dropping a pencil and reaching to catch it involves neural impulses racing from eyes to brain and then to hand to help react.
Neurotransmitters - The Bridge
Neurotransmitters are chemical bridges that help one neuron pass its message to another.
They are stored in sacs (vesicles) at the ends of neurons.
When a neural impulse arrives, neurotransmitters are released into the synaptic gap and help the message continue.
Example: When answering a question, neurotransmitters enable brain communication so I can understand and respond.
To Sum It Up
Nervous system is the body’s control center.
Made up of neurons, the messengers.
Neurons carry neural impulses (signals).
Neurotransmitters act as bridges to pass signals to other neurons.
All parts work together to think, feel, move, and respond in various situations.
Divisions of the Nervous System (2.2)
Central Nervous System (CNS)
Controls thoughts, movements, and processing of sensory information.
Acts as the body’s command center.
Peripheral Nervous System (PNS)
Sends sensory information to the CNS and motor commands from the CNS.
It has two parts:
Somatic Nervous System (controls voluntary muscle movements; transmits sensory signals to CNS and motor commands from CNS)
Autonomic Nervous System (ANS) (controls involuntary functions such as heart rate and digestion; transmits sensory signals to CNS and motor commands to muscles)
Autonomic Nervous System has two branches
Sympathetic Division: prepares body for "fight or flight" (↑ heart rate, dilates pupils, slows digestion)
Parasympathetic Division: promotes "rest and digest" (↓ heart rate, constricts pupils, activates digestion)
Understanding the Brain
How Do We Know Brain Functions?
A. Accidents: brain injuries reveal which areas control speech, movement, memory, etc.
B. Animal Tests: damaging brain parts in animals shows behavioral effects.
C. Brain Stimulation (Penfield): electrical stimulation of brain areas caused memories, sensations, or movements and helped map brain functions.
Lateralization: an injury to the left side of the brain affects movement and sensation on the right side of the body, while injury to the right side affects the left.
The Voyage Through The Brain
The Hindbrain – Basic Life Support
Hindbrain structures include: medulla, pons, cerebellum, spinal cord (as part of the CNS).
Medulla: controls heart rate, breathing, blood pressure, coughing, sneezing.
Pons: bridge for nerve signals; involved in sleep, arousal, attention, and movement.
Cerebellum ("Little Brain"): coordinates balance and motor movement.
Damage to cerebellum can cause poor coordination, stumbling, and loss of muscle tone.
Reticular Formation – Brain’s Alert System (RAS)
Begins in the hindbrain and runs up to the forebrain.
Controls attention, arousal, and sleep.
Stimulation leads to instant alertness; damage can cause coma.
Depressants (e.g., alcohol) reduce its activity.
The Forebrain – Higher Thinking & Control
Forebrain structures include:
Cerebral Cortex (outer layer)
Cingulate Gyrus
Corpus Callosum
Thalamus
Hypothalamus
Limbic System (Amygdala, Hippocampus)
Thalamus
Relay station for sensory information (e.g., vision).
Regulates sleep and attention.
Hypothalamus
Regulates hunger, thirst, temperature, emotion, sex, aggression.
Notable note: historically, “pleasure centers” were discovered in rats by Olds & Milner; humans show more influence from thought and values on behavior.
The Limbic System – Emotion & Memory
Amygdala: involved in aggression, fear, emotional memory, vigilance.
Damage can produce calm; stimulation can evoke rage or fear.
Hippocampus: stores new memories; damage impairs the ability to form new memories.
The limbic system is linked to hunger, sex, and aggression.
Key Brain Areas – At a Glance
Medulla: Heartbeat, breathing
Pons: Sleep, movement, attention
Cerebellum: Balance, motor coordination
Reticular Formation: Arousal, alertness, consciousness
Thalamus: Sensory relay to cortex
Hypothalamus: Hunger, emotion, temperature, motivation
Amygdala: Fear, aggression, emotional responses
Hippocampus: Memory formation
The Cerebral Cortex and The Cerebrum
The Cerebral Cortex
Outermost layer of the brain; responsible for higher-level processes like language, memory, reasoning, thought, decision-making.
The Structure of the Cerebral Cortex
Two hemispheres: right and left.
Each hemisphere is divided into four lobes:
Frontal Lobe – involved in planning, decisions, movement, personality
Parietal Lobe – processes touch, pain, temperature, body awareness
Temporal Lobe – processes hearing, memory, emotion, focus
Occipital Lobe – processes vision
Lobe-specific Details
Temporal Lobe: located below the lateral fissure; handles hearing, emotion, memory, attention to important events.
Occipital Lobe: at the back of the brain; processes vision; stimulation can cause flashes of light even in darkness.
The Cerebrum – Human Thinking Center
Cerebral Cortex: Outer wrinkled layer; more surface area yields greater cognitive power.
Corpus Callosum: About nerve fibers connecting left and right hemispheres; enables communication between both sides.
The Cerebral Cortex – Summary
The cortex is the outer layer responsible for higher cognitive functions: language, memory, reasoning, thought, decision-making.
Each hemisphere contains four lobes with specialized functions.
The Structure of the Cerebral Cortex (Detailed)
Each hemisphere contains four lobes as listed above.
The two areas behind the central fissure:
Somatosensory Cortex (sensory area)
Motor Cortex (motor area)
Language areas:
Broca's area
Wernicke's area
Types of Aphasia:
Broca's aphasia - difficulty in forming speech
Wernicke's aphasia - difficulty in comprehension
Quick Content Review (Key Takeaways)
The nervous system integrates mental processes, motor control, and physiological regulation.
Neurons and neurotransmitters underlie neural communication.
The CNS processes information; the PNS gathers information and executes commands.
The brain is organized into hindbrain (basic life support), midline structures (e.g., reticular formation), and forebrain (cognition, emotion, memory).
The forebrain includes the limbic system for emotion and memory and the cerebral cortex for higher-order thinking.
The lobes of the cortex have distinct but integrated roles in perception, action, and thought.
Language centers (Broca’s and Wernicke’s) support speech and comprehension; damage can lead to aphasia.
Brain research uses natural experiments (accidents), animal studies, and stimulation to map functions.
Glossary of Key Terms
Neuron: basic cell of the nervous system that transmits information.
Dendrites: receive signals.
Axon: transmits signals.
Axon terminals: pass signals to next neuron.
Neurotransmitter: chemical messenger across the synapse.
Synapse: gap between neurons where neurotransmitters travel.
CNS: brain and spinal cord.
PNS: nerves outside the CNS.
Somatic Nervous System: voluntary control of muscles.
Autonomic Nervous System: involuntary control of body functions.
Sympathetic Division: "fight or flight" responses.
Parasympathetic Division: "rest and digest" responses.
Hindbrain: medulla, pons, cerebellum (basic life support, coordination).
Reticular Formation (RAS): arousal and attention.
Forebrain: thalamus, hypothalamus, limbic system, cerebral cortex.
Thalamus: sensory relay station.
Hypothalamus: drives for hunger, thirst, temperature, emotions; homeostatic regulator.
Amygdala: emotion (fear, aggression).
Hippocampus: memory formation.
Corpus Callosum: connects left and right hemispheres.
Broca’s area: language production.
Wernicke’s area: language comprehension.
Aphasia: impairment of language ability from brain damage.
sulci - grooves or indentations on the surface of the brain that separate the gyri (ridges) and play a crucial role in increasing the brain's surface area to accommodate more neurons.
gyri - the ridges of the brain's surface that are separated by sulci and are important for enhancing cognitive functioning by providing more cortical area for neural processing.