Psych 120: Biological Bases of Behaviour
Biological Bases of Behaviour - Psych 120
Learning Objectives
Label and describe the function of each part of a neuron.
Describe how neural impulses travel within a neuron.
Describe the absolute and relative refractory periods.
Differentiate between a postsynaptic potential and the relative refractory period.
Neurons and Neural Impulses
Parts of the Neuron
Dendrites
Function: Receive information from other cells.
Soma
Definition: The cell body of the neuron.
Axon
Definition: Long, thin fiber extending from the soma.
Note: Can vary in length from very short to over 1 meter.
Myelin Sheath
Definition: Insulating layer around the axon.
Terminal Buttons
Function: Release neurotransmitters into the synaptic cleft.
Myelin
Insulation properties of myelin increase transmission speed.
Speed of neural impulse:
Without myelin: 0.5 - 10 m/s
With myelin: up to 150 m/s
The Nodes of Ranvier are gaps in the myelin sheath where action potentials are propagated.
Resting State and Action Potential
Resting State:
Characterized by the presence and distribution of ions:
Na+ (sodium ions) and K+ (potassium ions).
Action Potential:
A rapid rise and fall in membrane voltage.
Process:
Resting State (around -70mV): Neuron is at rest.
Stimulus Applied: A stimulus activates the neuron, causing Na+ ions to rush in, changing the membrane potential.
Voltage Rises (to +30mV): Neuron depolarizes.
Voltage Falls: Following the peak, K+ ions are pumped out of the neuron, repolarizing it.
Return to Rest: The neuron returns to resting potential.
Characteristics:
All-or-nothing response.
Absolute Refractory Period: Period during which another action potential cannot be initiated.
Relative Refractory Period: Period during which a stronger than normal stimulus can initiate another action potential.
Synapses & Neurotransmitters
Learning Objectives
Describe how information is transferred between neurons at the synapse.
Explain postsynaptic potentials.
Define neurotransmitter and identify the functions of various neurotransmitters including:
Acetylcholine
Dopamine
Norepinephrine
Serotonin
Endorphins
Describe the roles of agonists and antagonists in neurotransmitter function.
Synapses
Definition: Junctions between neurons where information transfer occurs.
Components:
Terminal Button
Neurotransmitter (chemical messengers released into the synaptic cleft).
Synaptic Vesicles (packets containing neurotransmitters).
Receptor Site on the postsynaptic neuron.
Postsynaptic Potentials
Two types:
Excitatory Postsynaptic Potential (EPSP): Increases likelihood that the receiving neuron will fire.
Inhibitory Postsynaptic Potential (IPSP): Decreases likelihood that the receiving neuron will fire.
Depicted with changes in membrane voltage over time; firing threshold shown at -50mV.
Agonists & Antagonists
Agonists: Increase activity at receptor sites (mimic actions of neurotransmitters).
Antagonists: Decrease activity at receptor sites (block neurotransmitter actions).
Neurotransmitter Functions
Acetylcholine:
Role in movement and attention.
Associated with botulinum toxin (Botox) and curare as antagonists.
Nicotine acts as an agonist.
Dopamine:
Involved in motor control and reward-seeking behavior.
Related to conditions such as Parkinson’s disease and the use of L-Dopa.
Cocaine and amphetamines increase dopamine activity.
Norepinephrine:
Regulates mood and arousal, and attention to important stimuli.
Cocaine and amphetamines increase norepinephrine activity.
Serotonin:
Regulates sleep, appetite, and mood.
SSRIs like Prozac and Paxil influence serotonin levels; commonly connected to depression.
Endorphins:
Endogenous morphine-like substances inducing feelings of pleasure and pain relief.
Tied to phenomena such as the “endorphin rush” after exercise (runner's high), and related to drugs like morphine and heroin.
The Nervous System
Learning Objectives
Describe the organization of the human nervous system.
Differentiate between the peripheral and central nervous systems (CNS & PNS).
Distinguish autonomic and somatic nervous systems.
Describe functions of sympathetic and parasympathetic nervous systems.
Identify parts of the central nervous system and their functions.
Organization of the Nervous System
Central Nervous System (CNS):
Composed of the spinal cord and brain.
Peripheral Nervous System (PNS):
Encompasses all the nerves outside the CNS.
Divided into:
Somatic Nervous System: Deals with voluntary movement and sensation.
Autonomic Nervous System: Manages involuntary actions (e.g., heart rate)
Further divided into:
Sympathetic Division: Mobilizes energy for fight-or-flight response.
Parasympathetic Division: Conserves energy, promotes rest-and-digest responses.
Specific Functions of the Autonomic Nervous System
Parasympathetic Responses:
Pupils constricted, salivation stimulated, bronchial passages constricted, decreased heart rate and respiration, digestion stimulated, bladder contracted.
Sympathetic Responses:
Pupils dilated, salivation inhibited, bronchial passages dilated, increased heart rate and respiration, digestion inhibited.
Central Nervous System Components
Brain: Metabolic and integrative functions.
Meninges: Protective layers around the brain and spinal cord.
Cerebrospinal Fluid (CSF): Cushions and protects the brain.
Spinal Cord: Connects the brain to the body; damage can lead to loss of sensation or motor control.
The Hindbrain and Midbrain
Learning Objectives
Describe components of the hindbrain and midbrain, their locations, and functions.
Recognize the regions of the brain and their effects on behavior and function.
The Hindbrain
Cerebellum
Functions: Controls fine muscle movement and balance.
Medulla
Functions: Regulates blood circulation, breathing, muscle tone, and reflexes like sneezing and coughing.
Pons
Functions: Involved in sleep and arousal.
Reticular Formation
Functions: Affects sleep-wake cycles and arousal.
The Midbrain
Definition: Part of the brainstem responsible for integrating sensory processes.
Contains:
Superior colliculi: Involved in visual processing.
Inferior colliculi: Related to auditory processing.
Substantia nigra: Critical for dopamine production and motor control.
The Forebrain
Learning Objectives
Describe location and function of thalamus, hypothalamus, basal ganglia, amygdala, and hippocampus.
Key Structures of the Forebrain
Thalamus:
Function: Acts as a relay station for sensory information; integrates sensory input.
Hypothalamus:
Controls the autonomic nervous system and regulates basic biological drives (the four Fs: feeding, fighting, fleeing, mating).
Basal Ganglia:
Associated with movement and learning; plays a role in disorders such as Huntington's disease.
Limbic System:
Involved in emotion, memory, and motivation; includes parts of the thalamus, hypothalamus, hippocampus, and amygdala.
Amygdala:
Responsible for basic emotional responses such as fear and aggression; key role in emotional learning.
Hippocampus:
Plays a crucial role in the formation and consolidation of memories, as demonstrated by case studies like patient H.M.
The Cortex and Hemispheric Specialization
Learning Objectives
Describe the structure and functions of the cortex.
Identify functions of the lobes of the brain.
Explain the role of the corpus callosum in hemispheric communication and lateralization.
Cerebral Cortex
Definition: Outer layer of the cerebrum responsible for higher-level functions like thinking, memory, and consciousness.
Corpus Callosum
Connection that facilitates communication between the left and right hemispheres of the brain; integral for coordinated function.
Hemispheric Specialization
Left Hemisphere:
Specializes in verbal processing including speech, reading, and writing.
Mainly processes information from the right side of the body.
Right Hemisphere:
Specializes in nonverbal processing, including spatial tasks, music, and visual recognition.
Primarily processes information from the left side of the body.
Brain Lobes and Their Functions
Occipital Lobe:
Primary Visual Cortex: Initial reception and processing of visual information.
Dorsal and ventral stream pathways for movement guidance and object perception, respectively.
Parietal Lobe:
Primary Somatosensory Cortex: Processes bodily sensations and spatial relationships.
Plays a role in tactile perception and proprioception.
Temporal Lobe:
Primary Auditory Cortex: Processes auditory information.
Wernicke’s Area: Crucial for language comprehension.
Frontal Lobe:
Prefrontal Cortex: Involved in higher-order functions such as decision-making and planning.
Primary Motor Cortex: Responsible for voluntary movement control.
Broca’s Area: Specialized for speech production.
Learning, Memory, & the Brain
Learning Objectives
Identify brain regions involved in various types of learning.
Distinguish between retrograde and anterograde amnesia.
Describe the effects of hippocampal removal.
Discuss enriched environments and their effects on brain plasticity.
Key Brain Regions in Learning
Basal Ganglia: Plays an essential role in associative learning.
Amygdala: Critical for emotional learning.
Hippocampus: Vital for forming new memories.
Amnesia
Retrograde Amnesia: Inability to recall memories prior to a certain event.
Anterograde Amnesia: Inability to form new memories after an event (e.g., patient H.M. who experienced anterograde amnesia after hippocampal removal).
Long-Term Potentiation (LTP)
Concept introduced by Donald Hebb: “neurons that fire together wire together.”
Associated with increased synaptic strength, dendritic receptor sensitivity, and number of synaptic vesicles.
Consolidation of Memory
Synaptic Consolidation: Structural changes in synaptic connections may occur within hours to days after learning.
Systemic Consolidation: Processes like memory retrieval transition from hippocampal dependence to a more distributed cortical network over time, potentially taking years for maturation.