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Neurons and Neurotransmission: Types, Functions, and Communication, Lecture notes of Psychology

Tulane University Psychology

An overview of neurons, their functions, and the communication between them through neurotransmission. It covers the three major types of neurons: sensory, motor, and regular neurons. the structure of neurons, including dendrites, cell body, axon, and terminal buttons. It also discusses the role of glial cells in supporting neurons and the process of neurotransmission, including the release of neurotransmitters and their impact on receiver neurons. Seven major neurotransmitters are introduced: acetylcholine, norepinephrine, dopamine, serotonin, GABA, endorphins, and glutamate.

What you will learn

What are the functions and effects of the seven major neurotransmitters?
How does neurotransmission occur between neurons?
How do sensory neurons transmit messages to the central nervous system?

What are the three major types of neurons?
What is the role of glial cells in the brain?

Typology: Lecture notes

2021/2022

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Lecture 4.1 Biology of behavior

Evolutionary principles

The problem of design

Prior to Darwin, naturalists faced a number of difficult questions:

•How to account for the diversity of species

•How to explain the appearance of design among species

• Extraordinary, and clearly non-random, fit between organism and environment

Theory of evolution by natural selection

•Independently proposed by Charles Darwin and Alfred Russel Wallace

•Distinguishing “evolution” from “natural selection”

• Evolution = change over time in a population

• Natural selection = one of the mechanisms through which evolution can occur, and

the only mechanism that will produce the appearance of design

Building blocks of natural selection

1. Variation

2. Inheritance

3. Selection

Gaps in the original theory

•Problem # 1: Elaborate characteristics lacking in obvious function

•Decoration/ornamentation

•e.g., the peacock’s tail

•The Solution:Sexual Selection

•Another mechanism proposed by Darwin

•This mechanism focuses on success in mating

•Two processes

•Mate choice

•Intrasexual competition

•Problem # 2: No theory of inheritance

•Darwin preferred a blending theory, but this was not supported and faced conceptual

problems from the outset

•The Solution:Mendelian genetics

•Demonstrated particulate inheritance, giving rise to the concept of the gene

•Unknown to Darwin but rediscovered at the turn of the 20th century

•Led to synthesis of evolutionary theory with genetics (population genetics)

•Consequences of Mendelian genetics

•A gene’s eye or gene-centric view of the natural world

•On this view, organisms are machines built by genes to promote their reproduction

•Replicator dynamics

Gaps in the original theory

•The Solution:Inclusive Fitness

•Introduced by W. D. Hamilton in 1964

•A consequence of gene-centric thinking

•A gene can foster its success by promoting the reproduction of copies of itself carried by

other individuals

•Inclusive fitness = direct + indirect fitness

End products of evolution

1

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Download Neurons and Neurotransmission: Types, Functions, and Communication and more Lecture notes Psychology in PDF only on Docsity!

Lecture 4.1 Biology of behavior Evolutionary principles The problem of design Prior to Darwin, naturalists faced a number of difficult questions: •How to account for the diversity of species •How to explain the appearance of design among species

Extraordinary, and clearly non-random, fit between organism and environment Theory of evolution by natural selection •Independently proposed by Charles Darwin and Alfred Russel Wallace •Distinguishing “evolution” from “natural selection”
Evolution = change over time in a population
Natural selection = one of the mechanisms through which evolution can occur, and the only mechanism that will produce the appearance of design **Building blocks of natural selection

Variation
Inheritance
Selection Gaps in the original theory •Problem # 1: Elaborate characteristics lacking in obvious function** •Decoration/ornamentation •e.g., the peacock’s tail •The Solution:Sexual Selection •Another mechanism proposed by Darwin •This mechanism focuses on success in mating •Two processes •Mate choice •Intrasexual competition •Problem # 2: No theory of inheritance •Darwin preferred a blending theory, but this was not supported and faced conceptual problems from the outset •The Solution:Mendelian genetics •Demonstrated particulate inheritance, giving rise to the concept of the gene •Unknown to Darwin but rediscovered at the turn of the 20th century •Led to synthesis of evolutionary theory with genetics (population genetics) •Consequences of Mendelian genetics •A gene’s eye or gene-centric view of the natural world •On this view, organisms are machines built by genes to promote their reproduction •Replicator dynamics Gaps in the original theory •The Solution:Inclusive Fitness •Introduced by W. D. Hamilton in 1964 •A consequence of gene-centric thinking •A gene can foster its success by promoting the reproduction of copies of itself carried by other individuals •Inclusive fitness = direct + indirect fitness End products of evolution

•Adaptations

Inherited and reliably developing characteristics that emerged because they functioned to solve recurring ancestral problems, resulting in greater reproductive success •By-products
Side-effects of adaptations; these did not emerge directly by virtue of improving reproductive success •Noise
Chance variation; everything else The Basics of Evolutionary Psychology •By analog with other bodily organs, the brain has an overarching function •The overarching function of the brain is to process information •The brain is an information-processing device that serves to generate decisions and behaviors that are adaptive under ancestral conditions •The mind as computer •Evolutionary psychology integrates evolutionary theory with cognitive science •Research focus: identify mental adaptations AKA evolved psychological mechanisms, which use information-processing procedures to solve specific adaptive problems that recurred over time Evolved psychological mechanism Evolved psychological mechanisms deploy information-processing procedures to solve adaptive problems Much of evolutionary psychology is devoted to fleshing out the details of this kind of minimal cognitive model
How to do this?
Attempt to specify an adaptive problem
Perform a task analysis: what tasks must be done to solve the problem?
What information would be available in the ancestral environment for the execution of this task?
What operations and outputs would efficiently solve the problem? Broad Types of Adaptive Problems •Problems of survival and growth
Surviving and developing long enough to reproduce •Problems of mating
Selecting, attracting, and retaining a mate (and actually mating.. .) •Problems of parenting
Getting offspring to the point where they can reproduce •Problems of interacting with other people, including aiding genetic relatives

Neurons and Glial Cells Neurons are supported by another type of cell called glial cells •Glial cells come in different varieties and perform many functions

Improve speed of neural transmission
Promote new neural connections
Heal cells
Remove dead neurons
And more •There are estimated to be about as many glial cells as neurons in the brain. **Communication between neurons
At the end of axon, an electrical impulse (the action potential) triggers release of neurotransmitters (chemical messengers)**
Neurotransmitters cross the (synaptic gapspace between neurons) and bind to other neurons
Unused neurotransmitters are reabsorbed during reuptake
The binding of the neurotransmitters influences the response of the receiver neuron
Two types of responses, which depend on the neurotransmitter and the receptor site
Excitatory : increase activity, chance of neuron firing
Inhibitory : decrease activity, chance of neuron firing Communication Within Neurons
Neuron receives signals from sensory receptors or other neurons
Signal triggers action potential: electrical charge that travels down the axon
Positive ions are let into the cell (Na+)
Positive charge travels down axon
Action potential is an “all or none process”
Threshold = minimum intensity required to generate an action potential

How the action potential works •In its resting state, the axon is negatively charged, at about -70 millivolts. This happens because positively charged ions are kept outside the cell membrane. This state is called resting potential. •When neuron stimulation exceeds the threshold of about -55 millivolts, the action potential is triggered. Positively charged sodium ions enter the membrane, resulting in a positive charge of about +30 millivolts. This is called depolarization. •After depolarization, positive ions begin to move back outside the membrane during repolarization. Eventually, the axon returns to its resting state at -70mv. NEUROTRANSMITTERS

**- More than 100 neurotransmitters have been identified

These molecules**
- Are synthesized by the presynaptic neuron and stored in the presynaptic neuron’s terminal buttons
- Are released into the synapse by the presynaptic neuron when the action potential reaches the terminal buttons
- Bind to receptors in the postsynaptic neuron
- These receptors are specific for the neurotransmitter - Although there are 100+ neurotransmitters, we will focus on only seven major ones
- Acetylcholine (Ach)
- Norepinephrine (NE)
- Dopamine (DA)
- Serotonin (SE)
- Gamma-amino-butyric acid (GABA)
- Endorphins
- Glutamate

Lecture 4.3: BIology of behavior Brain NERVOUS SYSTEM Two main divisions:

- Central nervous system (CNS): Brain and spinal cord - Peripheral nervous system (PNS) - All nerves going to and from CNS - Somatic and Autonomic 2 subdivisions of PNS: •Somatic NS

controls voluntary movements of our skeletal muscles
e.g., movement of an arms and legs •Autonomic NS
controls involuntary movement of glands and muscles
e.g., heart, respiration
2 types: Sympathetic and Parasympathetic
Sympathetic : arouses body, uses energy
fight or flight
Parasympathetic : calms body, saves energy
rest and digest or feed and bree CENTRAL NERVOUS SYSTEM We will discuss 6 major components •Cerebral Cortex •Basal Ganglia •Limbic System •Cerebellum •Brainstem •Spinal Cord

1. CEREBRAL CORTEX

•The cerebral cortex is the thin outer layer of the brain—from the Latin cortex, meaning “bark” •Most recently evolved structure of the brain •Many wrinkles and folds—more efficient use of space •Gray in color (“gray matter”): cell bodies and unmyelinated fibers •Four lobes : frontal, parietal, occipital, and temporal. CEREBRAL CORTEX: LATERALIZATION •There are two cerebral hemispheres: left and right

Left hemisphere controls motor functions for right side of body and vice versa •Each hemisphere is somewhat specialized for different functions, but functioning is highly integrated •The corpus callosum (band of millions of nerve fibers) connects the hemispheres 2. BASAL GANGLIA •Key role in planning and initiation of motor movement •Contains such structures as the caudate nucleus, the putamen, and the substantia nigra •Features many dopamine receptors, and for that reason appears to be involved in reward-based learning •Damage to basal ganglia results in Parkinson’s disease

BRAIN DEVELOPMENT

•Our brains don’t fully develop until the mid to late 20’s •The networks of neurons in the brain changes over the course of development in 4 primary ways

Growth of dendrites and axons
Synaptogenesis: forming of new synapses
Pruning: removal of unused connections
Myelination: Insulation of axons with a myelin sheath NEUROSCIENTIFIC METHODS Surgical Lesions
Attempt to match behavioral deficits to specific areas of brain damage **Brain stimulation
Electrical:** microelectrodes are implanted at a specific brain site using a stereotaxic device (the device uses a set of three coordinates to target brain locations with great precision) - Chemical: injection via a small syringe stimulates or inhibits receptors in a specific brain region Electrical Recording
Neural electrical activity is recorded using tiny wires implanted in the brain; can be used to detect the activity of single neurons Electroencephalography (EEG)
Measurement of electrical activity at the cortex
Amplifies electrical potentials to reveal patterns called brain waves that vary based on the patient’s state
Can also identify brainwave patterns associated with specific stimuli; these patterns are known as evoked potentials Positron Emission Tomography (PET)
Uses radioactive isotopes to determine active areas of the brain Functional Magnetic Resonance Imaging (fMRI)
Measures changes in blood flow during specific tasks
Maps these changes onto detailed 3D images of the brain
The 3D images are obtained by using radio waves to create localized magnetic field changes in the brain, which are detected by a huge magnet

Lecture 4.4. Biology of behavior endocrine system y drugs Biological Foundations od Behavior The endocrine system •The endocrine system is a network of glands that release hormones into the bloodstream •Hormones are chemical signals that influence the functioning of specific body organs (“target organs”)

Some hormones are chemically identically to neurotransmitters; in these cases, the difference is whether they are released by a neuron into a synapse, or by a gland into the bloodstream
An example of a hormone that also act as a neurotransmitter is norepinephrine •Because hormones are released into the bloodstream, they influence behavior more slowly than do neurotransmitters. •However, hormones linger in the bloodstream and therefore often have longer-lasting effects
In this sense, hormones are more of a “slow burn” Glands of the Endocrine System The pituitary gland •A major player in the endocrine system, sometimes called “the master gland” •Controlled by the hypothalamus, below which it is located •Releases a large number of hormones, some of which cause other glands to release other hormones The Thyroid Gland •Located in the neck •Releases the hormone thyroxine •Influences metabolism (conversion of food into energy), as well as growth and maturation •Too much thyroxine (hyperthyroidism) can cause weight loss, anxiety, and hyperactivity

Opioids are one common type
- Hydrocodone, OxyContin, Percocet, morphine, heroin
Create feelings of euphoria
Once used up, intense withdrawal and a need to use again usually follows MARIJUANA
Classified as a narcotic, but unlike opioids it intensifies sensory experiences.
No more of a “gateway”drug than tobacco and alcohol
But...it impairs learning and memory
Active ingredient THC attaches to receptors in the hippocampus, where memories are consolidated HALLUCINOGENS
Produce sensory distortions and false sensory experiences
LSD (Lysergic acid diethylamide)
MDMA or ecstasy, acts as a stimulant at low doses and a hallucinogen at high doses.

Neurons and Neurotransmission: Types, Functions, and Communication, Lecture notes of Psychology

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Download Neurons and Neurotransmission: Types, Functions, and Communication and more Lecture notes Psychology in PDF only on Docsity!

1. CEREBRAL CORTEX

BRAIN DEVELOPMENT