Psych 330H Exam 2 Study Guide

Criteria for Neurotransmitters—Chemicals Released onto Target Cells

• Substance is present in presynaptic axon terminals

• Synthesized within presynaptic cells

• Released when action potentials reach axon terminals

• Receptors for the substance are located on the postsynaptic membrane

• When applied externally, the substance induces changes in postsynaptic cells

• Blocking the release of the substance prevents changes in the postsynaptic cell

types of neurotransmitters

• acetylcholine (Ach)

• monoamine

  • dopamine (DA)

  • serotonin (5-HT)

  • norepinephrine (NE)

• amino acid

  • GABA (gamma-aminobutyric acid)

  • glutamate

  • glycine

• peptide

  • opioid (ex: endorphins)

  • pituitary hormones

• gas

  • nitric oxide (NO)

acetylcholine/cholinergic receptors

• nicotinic

• muscarinic

nicotinic

• named after agonist nicotine (binds receptors)

• excitatory

• ionotropic receptors

  • ACh binding opens a cation channel

  • net ion movement depolarized the postsynaptic cell

• found in skeletal muscle

  • neuromuscular junction

• antagonized by curare (dart poison)

muscarinic

• metabotropic G protein-coupled receptors

• slower, longer-lasting effects

• M1-M5

  • M1, 3, 5 are excitatory

  • M2, 4 are inhibitory

• M2 receptors help slow heart rate

• atropine (antagonist) blocks muscarinic receptors-dilates pupil

acetylcholine function

• CNS

  • learning and memory

  • widespread loss in Alzheimer’s

• PNS

  • both sympathetic and parasympathetic

  • all striated muscle movement

glutamate

major excitatory amino acid NT

• depolarization

transmission uses ionotropic receptors (applies to any NT)

• AMPA: NA+ channel

• Kainate: NA+ and K+ channel

• NMDA: Ca++ channel (slowest)

• excitotoxicity: neural injury (like stroke) causes excess release of glutamate, which is toxic to neurons

neuropeptides

small protein neurotransmitters

• often co-released with classical NT’s

• modulating effect

• released in all parts of axon terminal, not just active zone

• destroyed by enzymes after release

• most receptors are metabotropic

• endorphins: endogenous opioid peptides (analgesia and reward)

nitric oxide

• differs from other NT’s

• produced in locations other than axon terminals (mainly in dendrites and diffuses as soon as it’s produced)

• retrograde transmitter: diffuses back into presynpatic neuron

• activates 2nd messenger pathways

• modulates activity of other NT’s

dopamine

• involved in movement, attention, motivation, learning, reinforcement

• reward seeking vs reward enjoyment

• all metabotropic

• DA dysfunction associated with Parkinson’s disease, schizophrenia, autism, ADHD

• mesolimbocortical pathway: ventral gemental area to nucleus, accumbens, cortex, and hippocampus (reward + reinforcement)

• mesotriatal pathway: substania nigra to striatum (basal ganglia; important for movement; reduced in Parkinson’s disease deep brain stimulation)

Mechanisms of Neurotransmitter Action

Neurotransmitters affect targets by acting on receptors, protein molecules located on the postsynaptic membrane

Ionotropic Receptors (Fast-acting)

Open ion channels directly upon neurotransmitter binding, leading to rapid cellular responses

• neurotransmitter binds directly to channel protein and ions flow across membrane

• direct and faster

• nicotinic acetylcholine receptor

Metabotropic Receptors (Slow-acting)

Initiate chemical reactions in the postsynaptic cell, often involving G proteins, leading to

changes such as opening ion channels indirectly or modulating other cellular processes

• neurotransmitter binds G-protein coupled receptor

• more chances to modify

• amplification

• slow but widespread effects

• muscarinic acetylcholine receptor

ligand

A substance that binds to a receptor, causing one of the following effects:

• Agonist: Activates the receptor, initiating its normal function

• Antagonist: Blocks the receptor, preventing its activation by other ligands

• Inverse Agonist: Produces the opposite effect of the receptor's typical action

competitive ligands

These substances bind to the same receptor site as the endogenous ligand, functioning as agonists, antagonists, or inverse agonists

Dopamine Pathways and Functions

Mesostriatal Pathway

• Origin: Midbrain (Substantia Nigra)

• Target: Striatum

• Function: Critical for motor control. Loss of neurons in this pathway leads to Parkinson’s disease

Mesolimbocortical Pathway

• Origin: Midbrain (Ventral Tegmental Area, VTA)

• Target: Limbic system and cortex

• Function: Involved in reward, reinforcement, and learning

Serotonin (5-HT) System

• Origin: Raphe nuclei and gut

• Projections: Widely distributed across the brain

• Functions: Involved in mood regulation, sleep, sexual behavior, and anxiety

• Clinical Relevance: Antidepressants (e.g., Prozac) increase serotonin activity, with specific

  effects depending on receptor subtypes

endogenous

NT receptor closed or open (with transmitter)

exogenous

drug/agonist (open)

antagonist (closed)

non-competitive antagonist (transmitter binds but closed)

signaling changes receptor expression

neurons down-regulate in response to agonsit drug (fewer available receptors)

neurons up-regulate receptors in response to an antagonist

what did Berthold’s experiment demostrate about hormones?

a hormone released from the testes (testosterone) must be present early in life to have dramatic effects on the body and behavior

Amino Acid Neurotransmitters

Excitatory

• Glutamate is the key excitatory neurotransmitters

Inhibitory

• GABA and Glycine are major inhibitory neurotransmitters

Peptide Neurotransmitters

can function as neurotransmitters or hormones. Key examples include

• Opioid: Mimic the effects of opiate drugs like morphine, modulating pain and

  reward

• Pituitary: Influence diverse physiological processes, often released in

  response to stress or hormonal changes

Gas Neurotransmitters

NO differs from traditional neurotransmitters in several ways

• It’s synthesized in dendrites, not axon terminals

• It diffuses freely across cell membranes rather than being released from vesicles

• It can act as a retrograde transmitter, signaling back to the presynaptic neuron to

  modulate neurotransmission

Definition and Function of Hormones

chemical compounds that act as signaling molecules within the body

They are secreted by endocrine glands or specialized cells and exert their effects by

interacting with specialized receptors on target cells

Hormone Communication

• autocrine (signaling within the cell)

• paracrine (1 cell to another, short distance like NT’s)

• endocrine (through blood stream from 1 cell to another)

Characteristics of Hormonal Action

• Hormones typically act in a subtle, gradual manner, altering the likelihood that a behavior will occur rather than acting as an on/off switch.

• Hormonal action is sensitive to environmental influences, modulating physiological and behavioral responses based on external stimuli.

Hormonal vs. Neural Communication

• Hormonal messages are broadcast slowly, affecting multiple targets in an “analog” fashion

  (gradual and sustained effects). These messages travel through the bloodstream and can

  influence distant or nearby cells

• Neural messages, in contrast, are transmitted quickly over fixed pathways in a "digital" manner (all-or-none responses)

• A single target cell may contain receptors for multiple hormones, allowing it to respond to

  different hormonal signals simultaneously

Shared Features of Neural and Hormonal Systems

• Both systems manufacture, store, and release chemical messengers

• Both use specific receptors to transduce signals, often involving second messenger systems within target cell

• Some chemicals, such as certain peptides, can act as both hormones and neurotransmitters, illustrating the close relationship between these systems

Types of Hormones and Their Action

• Peptide/Protein Hormones: Act relatively quickly, typically within seconds to minutes (GCPR)

• Amine Hormones: derived from single amino acids (usually tyrosine or tryptophan); some act like peptides, others like steroids. Examples: epinephrine, norepinephrine, melatonin, thyroid hormones

• Steroid Hormones: Act more slowly, often over hours or days, as they often influence gene

  expression. Very large family of hormones all based on a cholesterol backbone

Hormonal Regulation and Feedback Mechanisms

levels are tightly controlled by negative feedback loops

• In some cases, a gland's own secretions regulate its activity (simple feedback)

• In other cases, higher centers such as the pituitary gland modulate hormone levels,

  providing more complex feedback control over gland activity

Brain Control of the Endocrine System

The hypothalamus regulates the endocrine system by controlling the pituitary gland

pineal gland

reproductive maturation; bodily rhythms

pituitary gland:

• anterior pituitary

• posterior pituitary

• hormone secretion by thyroid, adrenal cortex, and gonads; growth

• water balance; salt balance

thyroid

growth and development; metabolic rate

adrenal glands:

• adrenal cortex (outer bark)

• adrenal medulla (inner core)

• salt and carbohydrate metabolism; inflammatory reactions

• emotional arousal

pancreas

sugar metabolism

gut

digestion and appetite control

gonads (testes/ovaries)

body development; maintenance of reproductive organs in adults

sexual behavior/development

AVPV

• uptick by fat tissue

• regulate puberty

• when active, especially for women, puberty begins

growth

James matthew barrie

• short stature has been attributed speculatively to childhood emotional distress

• psychogenic dwarfism (potentially)

• trauma → reduced growth hormone

endocrine feedback loops (homeostasis)

• too little X is detected (hypothalamus)

• hormone Y is released (endocrine cells to target cells)

• hormone Y increases X (biological response)

• as X rises, hormone Y release decreases (back to beginning)

• negative feedback

Hormonal Coordination of Physiological Functions

Many, such as growth, homeostasis, metabolism, and learning/memory, involve the interaction of multiple hormones working together to maintain balance in the body

Coordination of Neural and Hormonal Signals

Many behaviors require integrated neural-hormonal coordination. Messages in the body can

be transmitted via

• Neural-to-neural communication

• Neural-to-endocrine communication

• Endocrine-to-endocrine communicatio

• Endocrine-to-neural communication

This complex interaction ensures that physiological and behavioral responses are tightly

regulated

Neuroendocrine Mechanisms and Social Behavior

mechanisms play a critical role in modulating social behavior

• For example, the hormones oxytocin and vasopressin, along with their receptors in the brain, are closely involved in regulating behaviors such as bonding, trust, and social interaction

Phylogenetic Analysis

Understanding the evolutionary history of species helps us study the behavioral and neural adaptations that allow animals to exploit specific ecological niches

• Example: A species' brain structure may evolve to accommodate the complexity of its

  environment or social structure

Brain Divisions and Species Difference

The major brain divisions (e.g., hindbrain, midbrain, forebrain) are shared across all

vertebrates. However, brain differences between vertebrate species often correlate with their

ecology and the behavioral complexity required by their environment

• Example: Species that live in complex social structures or challenging environments

  tend to exhibit more complex brain structures

Encephalization

refers to the relative size of the brain compared to the body. Vertebrate species vary widely in their degree of encephalization

• Humans exhibit an unusually high degree, with brain size far exceeding the typical proportions for mammals

Rapid Brain Expansion

The size of the hominid brain tripled in volume over the course of 1.5 million years, from the time of Homo erectus to Homo sapiens (about 200,000 years ago). Comparing the human brain to that of our closest living relatives, such as chimpanzees, reveals several unique features

• Greater cortical area devoted to hand control

• Specialized regions for language processing

• Pronounced functional asymmetry (e.g., lateralization of brain function)

• Significant expansion of association areas such as the prefrontal cortex

• New capacities for ‘cultural evolution’

Central Brain Regions for Specialized Functions

Animals often use central brain regions for specific functions, even when those functions

depend on different types of sensory input. In such cases, diverse sensory information is often

routed to the same brain regions for processing

• Different species may use the same brain regions for tasks like spatial navigation, but the input might come from different senses, such as vision or olfaction

• Optic tectum/superior colliculus: orienting behaviors in predators and prey

Neurogenesis

Mitosis produces neurons from non-neuronal precursor cells

Cell Migration

Neurons move to specific locations to form distinct brain structures

Differentiation

Cells develop into specialized neurons or glial cells (transcription factors)

Synaptogenesis

Formation of synaptic connections between neurons

• Growth cones at the tips of axons and dendrites play a crucial role in synapse formation

Neuronal Cell Death (Apoptosis)

Selective elimination of surplus nerve cells

Synapse Rearrangement

Pruning or strengthening of synapses to refine neural circuits

Process Outgrowth

Growth of axons and dendrites

Chemoattractants

Chemical signals that attract growth cones

Chemorepellents

Chemical signals that repel growth cones

Neuronal Survival and Apoptosis

Neurons compete for neurotrophic factors (chemicals produced by target cells) to survive.

Those that fail to obtain enough of these factors undergo apoptosis

Apoptosis

(programmed cell death) is a normal part of brain development:

• Controlled by specific genes, called death genes, and executed by a family of proteases

  known as caspases, which break down proteins and DNA

• Nerve Growth Factor (NGF) and Brain-Derived Neurotrophic Factor (BDNF) are

  crucial neurotrophic factors that help neurons survive and form connections

Synapse Rearrangement

A process of refining synaptic connections. Active synapses are maintained, while inactive ones are eliminated

• Neural activity and neurotrophic factors play roles in determining which synapses are

  retained

Chemoaffinity Hypothesis

Suggests that each neuron has a unique chemical identity that helps guide its synaptic connections

Glial Cells

continue to be produced throughout life and play a vital role in myelination

Myelination

by glial cells increases the speed of signal transmission in axons

• Diseases like multiple sclerosis disrupt myelin, impairing sensory and motor function

Sensitive Periods

Developmental windows during which experience or environmental input can lead to permanent changes in neural circuits

Evolutionary Timescale

Genes provide a basic developmental blueprint

Developmental Timescale

Cell-cell interactions during development refine the fate of individual cells

Neural Tube Formation

The nervous system begins with the formation of the neural tube from ectodermal tissue, which gives rise to the brain and spinal cord

Adult Neurogenesis

While slower than in early development, neurogenesis continues in the adult brain, contributing to plasticity

Glial Cell Proliferation

Most neurons are present at birth, but glial cells continue to be produced throughout life. Postnatal development involves myelination and synapse formation

Extrinsic Factors

External influences, including behavior and neural activity, shape the formation and elimination of synapses during development

Receptor Cells

Specialized cells within sensory organs that convert external stimuli into electrical signals

• Each sensory organ contains ones adapted to respond to specific types of stimuli (e.g., light, sound, touch)

Adequate Stimulus

The specific amount and type of energy capable of eliciting a response–a stimulus to which a sensory organ is particularly adapted

• Example: for photoreceptor cells in the retina is light with enough photons to elicit a response.

Adaptation

Sensory systems are optimized to detect specific stimuli relevant to the surround— can be important for filtering out irrelevant stimuli.

• This allows sensory organs to be more responsive to over a wider array of intensitie

Restricted Range of Responsiveness

Each sensory system operates within a restricted range of responsiveness, meaning it is sensitive to only certain types or intensities of stimuli

• Example: In hearing, the frequency range detectable by the auditory system varies across species

• Humans can hear sounds between approximately 20 Hz to 20 kHz, while dogs can detect higher frequencies up to 45 kHz

This range limitation reflects the environmental and ecological needs of the organism

Sensory Transduction

The process by which a receptor cell converts external energy (e.g., light, sound, pressure) into electrical energy, resulting in a change in membrane potential

• This electrical signal can then be transmitted through neurons to the brain for interpretation

• Example: In vision, photoreceptor cells in the retina transduce light into electrical signals that are relayed to the brain via the optic nerve.

Types of Attention

• Sustained Attention: Prolonged focus on a single task or stimulus

• Selective Attention: The ability to focus on specific stimuli while ignoring others (e.g., focusing on a conversation in a noisy environment)

Polymodal Cells

Specialized neurons that can process inputs from multiple sensory modalities, allowing for intersensory interactions

• Example: neurons might respond to both visual and tactile stimuli, integrating sensory information for a more comprehensive perception of the environment.

Intersensory Integration

The process by which the brain combines information from different senses to create a cohesive experience of the environment

• Example: The brain integrates visual and auditory information when watching a movie, so the sights and sounds appear synchronized.

Pure Tone Components

• Amplitude/Intensity: Perceived as loudness

• Frequency: Measured in Hertz (Hz), perceived as pitch

Sound Characteristics

• A sound comprises a fundamental frequency and harmonics, which are multiples of the fundamental frequency

• Fourier analysis: A mathematical tool to break down sounds into sine waves

External Ear

Structures: Pinna and ear canal

Function: Collect and funnel sound waves; shape enhances sound energy

Middle Ear

Function: Concentrates sound energy

• Ossicles: Malleus, Incus, and Stapes (vibrates cochlea), which connect the tympanic membrane (eardrum) to the oval window

Muscles stiffen to reduce sound impact when activated

• Tensor Tympani: Attaches to the malleus and tympanic membrane

• Stapedius: Attaches to the stapes

Inner Ear

Cochlea: Fluid-filled, spiral structure with base (near oval window) and apex

Organ of Corti: Key structure for sound transduction, comprising

Function: Converts sound vibrations into neural signals

• Hair cells (sensory cells)

• Supporting cells

• Basilar membrane: Vibrates in response to sound

Basilar Membrane

Different areas of the membrane respond to different frequencies

• High-frequency sounds displace the narrow base

• Low-frequency sounds displace the wider apex

Hair Cells

• Inner Hair Cells (IHCs: sensory to brain) and Outer Hair Cells (OHCs: amplification) are responsible for detecting sound

• Stereocilia (hairs) extend from hair cells; vibrations cause them to sway and trigger ion channels, leading to neurotransmitter release

Neural Transmission

• Afferent Nerves: Carry signals from hair cells to the brain

• Efferent Nerves: Send signals from the brain to hair cells

Auditory Pathway

From the vestibulocochlear nerve (cranial nerve VIII) to the brainstem and auditory cortex

• Tonotopic organization: Auditory processing regions are organized based on frequency response

• Techniques such as PET and fMRI reveal primary auditory cortex activation in the superior temporal lobe

Binaural Cues

Intensity differences: Variations in loudness between the ears

Latency differences: Variations in the time sound reaches each ear

• In birds, neurons in the nucleus laminaris function as coincidence detectors, forming a spatial map for sound localization

Five Basic Tastes

Salty, sour, sweet, bitter, and umami (more to be identified: e.g. fat?)

• sweet, bitter, umami → GCPR’s

• salty, sour → ion channels

Flavor

A combination of taste and smell

Taste Receptor Cells

Found in taste buds on the tongue, extending cilia into the taste pore