Brain and Behavior (Ch. 5)

Neurotransmitter

Chemicals in the nervous system that transmit signals across a synapse from one neuron to another.

Synaptic Plasticity

The ability of synapses to change their strength or efficiency, influencing learning and memory.

Excitatory Synapses

Synapses that promote the generation of action potentials in postsynaptic cells by increasing the likelihood of neuronal firing.

Inhibitory Synapses

Synapses that prevent action potentials by decreasing the likelihood of neuronal firing.

Acetylcholine (ACh)

A neurotransmitter involved in both excitatory and inhibitory synaptic transmission in various parts of the nervous system.

Dopamine (DA)

A neurotransmitter that regulates movement, motivation, and reward.

Serotonin (5-HT)

A neurotransmitter involved in mood regulation, wakefulness, and learning.

GABA (Gamma-Aminobutyric Acid)

The primary inhibitory neurotransmitter in the central nervous system.

Ionotropic Receptors

Receptors that directly control ion channels and are involved in fast synaptic responses.

What is the principal neurotransmitter used by motor neurons in the somatic nervous system?

Acetylcholine (ACh)

That is the role of norepinephrine in the autonomic nervous system

It increases heart rate and decreases digestion as part of the fight-or-flight response.

How do excitatory and inhibitory synapses differ in their effects on postsynaptic neurons?

Excitatory synapses increase the likelihood of firing action potentials, while inhibitory synapses decrease it.

What are the main functions of serotonin in the nervous system?

Regulates mood, wakefulness, and learning.

List two major disorders associated with dysfunctions of the dopaminergic system.

Parkinson’s disease and schizophrenia.

__________ is the ability of chemical synapses to change and adapt, which is crucial for learning and memory.

Synaptic plasticity

Neurotransmitters like dopamine and serotonin are classified as __________ molecules.

Small

In contrast to ionotropic receptors, metabotropic receptors influence ion channels through __________.

G-proteins

__________ is a neurotransmitter that plays a role in pain regulation and stress response.

Endorphins

Gap Junctions

Direct electrical links between cells that allow ions and small molecules to pass directly from one cell to another.

Chemical Synapse

A junction where messenger molecules (neurotransmitters) are released to affect a neighboring cell.

Otto Loewi’s Experiment

Demonstrated that nerve impulses utilize chemical messengers, leading to the discovery of neurotransmitters.

Synapse

The junction between neurons where neurotransmitters are released.

Postsynaptic Membrane

The cell membrane opposite the synaptic cleft that receives neurotransmitter signals.

Neurotransmitter Synthesis

The creation of neurotransmitters from precursor chemicals within a neuron.

Receptor Activation

When neurotransmitters bind to receptors on the postsynaptic membrane, initiating a signal.

Synaptic Cleft

The space between the presynaptic and postsynaptic neurons into which neurotransmitters are released.

Neurotransmitter Inactivation

The process by which neurotransmitters are removed from the synaptic cleft to terminate signaling.

Cholinergic Neurons

Neurons that release acetylcholine.

Adrenergic Neurons

Neurons that release norepinephrine.

Peptide Neurotransmitters

Larger molecules used as neurotransmitters, synthesized as needed.

Ion Transmitters

Zinc and other ions that act as neurotransmitters, important for cognitive functions

Hormones

Chemicals released by glands that regulate activities in various parts of the body

Feedback System

Mechanisms by which hormones are regulated through interactions between different organs and glands

Cortisol

A steroid hormone that manages stress response and regulates metabolism

Hippocampus

A region of the brain involved in forming new memories and linked to the stress response and emotional regulation

Endocrine System

The collection of glands that produce hormones regulating metabolism, growth, mood, and sexual functions

Neuromodulators

Chemicals in the nervous system that adjust the activity of groups of neurons, altering the strength of neurotransmitter effects

Explain the difference between chemical and electrical synapses

Chemical synapses use neurotransmitters to communicate, allowing complex signal modulation and are slower, whereas electrical synapses transmit signals via direct ionic currents through gap junctions, facilitating faster but less modulable communicati

What role do neurotransmitters play in synaptic plasticity?

They alter the strength and efficiency of synaptic transmission, influencing learning and memory by modifying the response of the postsynaptic neuron to future signals.

How does serotonin influence psychological functions and name two disorders associated with its imbalance?

It regulates mood, appetite, sleep, memory, and learning. Disorders include depression and obsessive-compulsive disorder.

Describe how the balance of excitatory and inhibitory neurotransmitters affects the central nervous system

Proper balance ensures stable and efficient brain function, while imbalances can lead to neurological or psychological disorders

What are the physiological implications of norepinephrine under stress?

Increases heart rate, expands air passages in the lungs, and narrows blood vessels in non-essential organs to prepare for the fight-or-flight response

Define metabotropic receptors and describe their role in neurotransmission

They indirectly influence ion channels through secondary messengers and G-proteins, leading to slower, longer-lasting effects compared to direct ion channel modulation by ionotropic receptors.

What is excitotoxicity and what can cause it?

It is the pathological process where excessive activation of excitatory neurotransmitters, such as glutamate, leads to neuronal injury and death.

Discuss the synthesis, release, and inactivation of neurotransmitters in a typical synaptic transmission.

Neurotransmitters are synthesized in the neuron, stored in vesicles, released into the synaptic cleft upon stimulation, bind to receptors on the postsynaptic neuron, and are then deactivated or reabsorbed.

How do hormones differ from neurotransmitters in their mechanism of action and effects?

They are secreted into the bloodstream and have widespread and longer-lasting effects on multiple organs, whereas neurotransmitters act locally at synapses and have rapid, short-term effects.

What is the function of acetylcholine in the autonomic nervous system, and how is it involved in both the sympathetic and parasympathetic divisions?

It is the neurotransmitter used by preganglionic neurons in both divisions and by postganglionic neurons in the parasympathetic division, regulating various bodily functions including heart rate and digestion.

Acetylcholine (ACh)

A neurotransmitter that controls muscle action and brain function

Activating system

A group of neurons that regulates brain activity and arousal.

Alzheimer disease

A neurodegenerative disorder causing memory loss due to brain cell death

Amino acid hormone

Hormones made from amino acids, like thyroid hormones.

Anabolic steroid

A synthetic hormone that builds muscle and promotes tissue growth

Anterograde synaptic transmission

Communication of signals from the presynaptic neuron to the postsynaptic neuron

Autoreceptor

A receptor on a neuron that regulates its own neurotransmitter release.

Carbon monoxide (CO)

A gas that acts as a signaling molecule in the nervous system

Chemical synapse

A gap between neurons where neurotransmitters pass signals

Cholinergic neuron

A neuron that releases acetylcholine

Dopamine (DA)

A neurotransmitter involved in reward, motivation, and movement.

Endocannabinoid

Natural compounds in the brain that affect mood, memory, and appetite.

Epinephrine (EP)

Also called adrenaline, a hormone that triggers the body’s fight-or-flight response.

Exocytosis

Process by which cells release substances (like neurotransmitters) into the synaptic cleft.

G protein

A protein that helps relay signals from receptors to the inside of a cell.

Gamma-aminobutyric acid (GABA)

The main inhibitory neurotransmitter in the brain, reducing nerve activity.

Gap junction

A direct connection between cells that allows ions and molecules to pass.

Glucocorticoid

A stress hormone that regulates metabolism and immune response

Glutamate (Glu)

The most common excitatory neurotransmitter in the brain

Gonadal (sex) hormone

Hormones like testosterone and estrogen, produced by the ovaries or testes.

Histamine (H)

A neurotransmitter involved in immune responses and regulating sleep-wake cycles.

Homeostatic hormone

Hormones that maintain the body’s internal balance, like insulin.

Hydrogen sulfide (H2S)

A gas that acts as a neurotransmitter and influences cell function.

Ionotropic receptor

A receptor that opens ion channels when a neurotransmitter binds to it, causing quick responses.

Lipid hormone

Hormones derived from fats, like steroid hormones

Major depression

A mental disorder with prolonged feelings of sadness and lack of interest.

Mania

A mental state characterized by excessive energy, euphoria, or irritability.

Metabotropic receptor

A receptor that triggers slower, longer-lasting cellular responses via second messengers.

Neuromodulators

Chemicals that alter the strength or effectiveness of neurotransmission

Neuropeptide neurotransmitter

Small protein-like molecules that act as neurotransmitters in the brain.

Nitric oxide (NO)

A gas that serves as a signaling molecule in the nervous system and regulates blood flow.

Noradrenergic neuron

A neuron that releases norepinephrine.

Norepinephrine (NE)

A neurotransmitter involved in alertness, arousal, and the fight-or-flight response

Obsessive-compulsive disorder (OCD)

A mental disorder marked by obsessive thoughts and repetitive behaviors

Parkinson disease

A neurodegenerative disorder affecting movement, caused by dopamine loss in the brain

Peptide hormone

Hormones made from chains of amino acids, like insulin.

Postsynaptic membrane

The membrane of a neuron receiving a signal from another neuron.

Presynaptic membrane

The membrane of a neuron sending a signal to another neuron

Quantum (pl. quanta)

The smallest unit of neurotransmitter release from a neuron.

Rate-limiting factor

A step in a process that limits the speed of the entire process.

Reuptake

The process by which neurotransmitters are taken back into the presynaptic neuron after signaling

Schizophrenia

A mental disorder marked by distorted thinking, perception, and emotions

Second messenger

Molecules inside cells that help transmit signals from receptors to target molecules.

Serotonin (5-HT)

A neurotransmitter that regulates mood, sleep, and appetite.

Small-molecule transmitter

A type of neurotransmitter, like acetylcholine or dopamine, made of small molecul

Steroid hormone

Hormones made from cholesterol, like testosterone and cortisol.

Storage granule

A structure inside a neuron where neurotransmitters are stored before release.

Subunit

A component part of a larger protein, often part of receptors

Synaptic cleft

The gap between neurons where neurotransmitters are released

Synaptic vesicle

Small sacs in neurons that store neurotransmitters before releasing them into the synaptic cleft

Transmitter-activated receptor

A receptor that responds to neurotransmitters and initiates a cellular response

Transporter

A protein that moves neurotransmitters back into neurons after signaling

Tripartite synapse

A synapse where not just two neurons, but also glial cells, are involved in signaling