Chapter 5: How do neurons communicate and adapt

What is acetylcholine (ACh) known for in the nervous system?

Acetylcholine excites skeletal muscles in the somatic nervous system and may either excite or inhibit various internal organs in the autonomic system.

Who was the first to isolate a chemical messenger, and what was it?

Otto Loewi was the first to isolate a chemical messenger, which was acetylcholine (ACh).

What role does norepinephrine (NE) play in the body?

Norepinephrine accelerates heartbeat and is closely related to epinephrine (EP).

What distinguishes neurotransmitters from hormones?

Neurotransmitters are released from neurons to act locally, while hormones are released from neurons or other tissues and travel further.

What is the main function of synaptic vesicles?

Synaptic vesicles contain neurotransmitter molecules that are released into the synaptic cleft.

What is the synaptic cleft?

The synaptic cleft is the small space separating the presynaptic neuron from the postsynaptic neuron, where neurotransmitters must bridge to carry messages.

What are the five steps of neurotransmitter release?

1. Synthesis of the neurotransmitter; 2. Packaging and storage in vesicles; 3. Release into the synaptic cleft; 4. Activation of receptors on the postsynaptic membrane; 5. Inactivation or degradation.

What is the main function of astrocytes in synaptic transmission?

Astrocytes contribute to neurotransmitter synthesis, facilitate their movement to synapses, and clean up excess neurotransmitter molecules.

What are ionotropic receptors?

Ionotropic receptors are embedded membrane proteins that have a binding site for a neurotransmitter and a pore that regulates ion flow.

What are metabotropic receptors?

Metabotropic receptors have a binding site for a neurotransmitter but do not have a pore and are linked to G proteins that affect other cellular processes.

What neurotransmitter is primarily used by cholinergic neurons?

Cholinergic neurons primarily use acetylcholine (ACh) as their neurotransmitter.

What is the difference between excitatory and inhibitory neurotransmitters?

Excitatory neurotransmitters increase the likelihood of an action potential in a neuron, while inhibitory neurotransmitters decrease that likelihood.

What happens during the receptor activation step of neurotransmission?

After neurotransmitter release, it diffuses across the synaptic cleft and binds to specific receptors on the postsynaptic membrane, leading to excitatory or inhibitory signals.

How are neurotransmitters inactivated?

Neurotransmitter inactivation can occur through diffusion, degradation by enzymes, reuptake into the presynaptic neuron, or uptake by nearby astrocytes.

What are small molecule transmitters?

Small molecule transmitters are quick-acting neurotransmitters synthesized from dietary nutrients and packaged in axon terminals.

What are peptide transmitters?

Peptide transmitters, also known as neuropeptides, are synthesized from amino acids and act more slowly than small molecules, influencing various physiological functions.

What is the role of neurotransmitters in the gastrointestinal (ENS)?

Neurotransmitters in the ENS, like serotonin and dopamine, allow the system to function autonomously without CNS input, detecting chemical and mechanical conditions.

What types of receptors respond to acetylcholine?

Acetylcholine interacts with nicotinic receptors (ionotropic) for muscle excitation and muscarinic receptors (metabotropic) for regulating internal organ functions.

What is the main neurotransmitter involved in the sympathetic nervous system (SNS)?

Norepinephrine (NE) is the main neurotransmitter involved in the sympathetic nervous system.

What distinguishes electrical synapses from chemical synapses?

Electrical synapses allow action potentials to pass directly between neurons through gap junctions, while chemical synapses use neurotransmitters to communicate.

What is an autoreceptor?

An autoreceptor is a receptor located on the same neuron that released the neurotransmitter, allowing it to regulate its own release in a negative feedback loop.

What neurotransmitters are associated with mood regulation?

Dopamine, serotonin, and norepinephrine are neurotransmitters closely associated with mood regulation.

What is the function of glucocorticoids in response to stress?

Glucocorticoids, like cortisol, regulate various physiological processes during stress, including metabolism and immune response.

What triggers the fast response to stress?

The fast response is triggered by the activation of the sympathetic division of the autonomic nervous system, resulting in the release of epinephrine.

How does the body end a stress response?

The body ends a stress response through mechanisms that reduce cortisol levels and restore normal physiological functions.

What are the criteria for identifying neurotransmitters?

1. The transmitter must be synthesized or present in the neuron; 2. It must be released and produce a response; 3. The same response must be obtained experimentally; 4. There must be a mechanism for removal after its action.

What is the purpose of neuromodulators?

Neuromodulators are neurotransmitters that modify the characteristics and firing of other neurons over extended periods.

What role does the hypothalamus play in hormonal control?

The hypothalamus produces neurohormones that stimulate the pituitary gland to release hormones into the bloodstream, influencing various endocrine glands.

How are lipid hormones characterized?

Lipid hormones, such as steroid hormones, are hydrophobic and synthesized from cholesterol, diffusing across membranes to act on target cells.

What are the effects of chronic high cortisol levels?

Chronic high cortisol levels can lead to hippocampal damage, reduced cognitive function, suppressed immune response, and disrupted hormonal balance.

How do endocannabinoids function in the nervous system?

Endocannabinoids act as neuromodulators by binding to receptors on presynaptic membranes, influencing neurotransmitter release.

What is an excitatory postsynaptic potential (EPSP)?

An EPSP is a change in the neuron’s membrane potential making it more likely to fire an action potential due to the influx of positive ions.

What is an inhibitory postsynaptic potential (IPSP)?

An IPSP is a change in the neuron’s membrane potential making it less likely to fire an action potential due to the influx of negative ions.

What kind of changes do peptide neurotransmitters induce?

Peptide neurotransmitters induce slower, more prolonged changes in target cells, such as modifying cell growth and function.

What is the difference between neurotransmitter release in small and large molecules?

Small molecule neurotransmitters are synthesized at axon terminals, while larger peptide neurotransmitters are synthesized in the cell body and transported to terminals.

What are the primary neurotransmitters involved in the regulation of heart rate?

Acetylcholine slows heart rate, while norepinephrine and epinephrine increase it, demonstrating both excitatory and inhibitory effects.

What is the function of transporters in synaptic transmission?

Transporters pump neurotransmitters back into the presynaptic axon terminal for reuse after their release.

What is a synaptic vesicle?

A synaptic vesicle is a small structure that stores neurotransmitters before they are released into the synaptic cleft.

What is the role of dopamine in the brain's reward system?

Dopamine is crucial for the brain's reward system, influencing behaviors linked to pleasure and motivation.

What is the significance of gap junctions in neurons?

Gap junctions allow direct electrical communication between neurons, facilitating rapid signaling.

What hormones are released in response to stress?

Epinephrine (adrenaline) and glucocorticoids like cortisol are released in response to stress.

How does serotonin affect mood regulation?

Serotonin helps regulate mood, with alterations in its activity associated with mood disorders like depression.

What distinguishes types of synapses, such as axodendritic and axosomatic?

Axodendritic synapses involve the axon terminal of one neuron synapsing onto the dendrite of another, while axosomatic synapses connect to the cell body directly.

What role do neurotransmitters play in learning and memory?

Neurotransmitters facilitate communication between neurons, essential for encoding and retrieving memories.

What neurotransmitter is primarily involved in movement coordination?

Dopamine is primarily involved in the coordination of movement and is affected in disorders like Parkinson's disease.

What can excessive norepinephrine activity lead to?

Excessive norepinephrine activity is associated with conditions like anxiety and stress-related disorders.

What is the significance of the hippocampus in stress regulation?

The hippocampus helps regulate stress responses by detecting cortisol levels and signaling for their reduction.

What is the action of insulin in the body?

Insulin is a peptide hormone that regulates blood sugar levels by facilitating glucose uptake into cells.

What is the relationship between hormones and homeostasis?

Hormones play a crucial role in maintaining homeostasis by regulating physiological processes in the body.

Why is the synthesis of neurotransmitters important?

The synthesis of neurotransmitters is essential for signal transmission, allowing communication between neurons.

How do the actions of neurotransmitters vary between excitatory and inhibitory receptors?

Excitatory receptors result in depolarization and potential action, while inhibitory receptors lead to hyperpolarization, reducing the likelihood of action potentials.

How do G proteins influence metabotropic receptors?

When G proteins are activated by neurotransmitters binding to metabotropic receptors, they can affect ion channels and initiate second messenger signaling pathways.

What is the role of serotonin in the body?

Serotonin is a neurotransmitter that regulates mood, appetite, and sleep, and is involved in many other physiological functions.

What is the influence of the parasympathetic nervous system on neurotransmission?

The parasympathetic nervous system promotes rest and digestion, often using acetylcholine to mediate its effects on target organs.

What is the primary function of the amygdala in relation to neurotransmitters?

The amygdala processes emotions and is sensitive to neurotransmitters like dopamine and serotonin, affecting mood and anxiety.

What is the significance of the blood-brain barrier in neurotransmission?

The blood-brain barrier protects the brain from harmful substances while allowing essential neurotransmitters to affect brain function.

What are the effects of endorphins in the nervous system?

Endorphins are natural painkillers released in response to pain and stress, promoting feelings of pleasure and well-being.

What is the difference between short-term and long-term potentiation?

Short-term potentiation enhances synaptic transmission for a brief period, while long-term potentiation strengthens synapses over a longer time, important for learning.

How does dopamine relate to addiction?

Dopamine pathways are involved in the brain's reward system, and their overactivation by drugs can lead to addictive behaviors.

What is the function of oxytocin in the body?

Oxytocin, often called the 'love hormone,' plays a role in social bonding, reproduction, and childbirth.

How does GABA function as an inhibitory neurotransmitter?

GABA (gamma-aminobutyric acid) reduces neuronal excitability by allowing more chloride ions to enter neurons, making them less likely to fire.

What role does glutamate serve in the brain?

Glutamate is the primary excitatory neurotransmitter in the brain, essential for synaptic plasticity and cognitive functions like learning.

What is the role of the synaptic cleft in neurotransmission?

The synaptic cleft allows neurotransmitters to diffuse across from the presynaptic neuron to the postsynaptic neuron, facilitating signal transmission.

What is glutamate's role in synaptic plasticity?

Glutamate is crucial for synaptic plasticity, which underlies learning and memory by strengthening synaptic connections.

How do astrocytes support neurons?

Astrocytes support neurons by providing nutrients, maintaining extracellular ion balance, and regulating neurotransmitter levels.

What are the primary functions of endocannabinoids?

Endocannabinoids modulate neurotransmitter release and can influence synaptic plasticity and pain modulation.

What neurotransmitter is associated with arousal and alertness?

Norepinephrine is associated with increased arousal and alertness, playing a key role in the fight-or-flight response.

How does the sodium-potassium pump affect neurons?

The sodium-potassium pump maintains the resting membrane potential by controlling ion concentrations, crucial for action potential generation.

What is the significance of long-term potentiation?

Long-term potentiation is significant for strengthening synapses over time, playing a vital role in memory formation.

What effect does chronic stress have on neurotransmitter levels?

Chronic stress can alter neurotransmitter levels, particularly reducing serotonin, which may contribute to mood disorders.

What function do neurotransmitter receptors serve?

Neurotransmitter receptors mediate the effects of neurotransmitters by initiating cellular responses upon binding.

What are the roles of inhibitory neurotransmitters like GABA?

Inhibitory neurotransmitters like GABA decrease neuronal excitability, helping to regulate anxiety and prevent overstimulation.

What is respiratory neurotransmission?

Respiratory neurotransmission involves neurotransmitters that regulate breathing and are crucial for maintaining respiratory functions.

What role do endocannabinoids play in pain modulation?

Endocannabinoids are involved in pain modulation by influencing the release of neurotransmitters associated with pain perception.

How do neurotransmitters affect appetite?

Certain neurotransmitters, such as serotonin and dopamine, play significant roles in regulating appetite and food intake.

What is the primary function of glial cells in the nervous system?

Glial cells support neurons by providing structural support, insulating nerve fibers, and facilitating communication between neurons.

What happens during synaptic plasticity?

Synaptic plasticity refers to the ability of synapses to strengthen or weaken over time, influencing learning and memory.

What neurotransmitter is primarily involved in the sleep-wake cycle regulation?

Melatonin, influenced by neurotransmitter signaling, plays a crucial role in regulating the sleep-wake cycle.

How does chronic stress affect the hypothalamic-pituitary-adrenal (HPA) axis?

Chronic stress can dysregulate the HPA axis, leading to increased cortisol levels and impact on overall endocrine function.

What is the role of neurotransmitters in gastrointestinal (ENS) motility?

Neurotransmitters in the ENS coordinate gut motility, facilitating digestion and the movement of food through the intestines.

What neurotransmitter is associated with learning and memory enhancement?

Acetylcholine is associated with enhancing learning and memory by facilitating synaptic transmission in the brain.

How do excitatory and inhibitory neurotransmitters interact for balanced neural function?

Excitatory and inhibitory neurotransmitters interact to maintain neural balance, regulating overall neuronal excitability.

What is the function of the synapse in neurotransmission?

The synapse is the junction between two neurons where neurotransmission occurs, allowing communication via neurotransmitters.

What occurs during synaptic transmission?

During synaptic transmission, neurotransmitters are released from the presynaptic neuron, cross the synaptic cleft, and bind to receptors on the postsynaptic neuron.

What is neurotransmission?

Neurotransmission is the process of signal transmission between neurons through the release and reception of neurotransmitters.

How do neurotransmitters transmit signals across the synapse?

Neurotransmitters diffuse across the synaptic cleft and bind to specific receptors on the postsynaptic membrane, eliciting a response.

What factors influence the effectiveness of neurotransmission?

Factors influencing neurotransmission effectiveness include neurotransmitter concentration, receptor sensitivity, and the health of the synapse.

What are the consequences of disrupted neurotransmission at synapses?

Disrupted neurotransmission can lead to various neurological disorders, affecting mood, cognition, and motor control.

What is the role of glial cells in synaptic function?

Glial cells support synaptic function by maintaining the environment, recycling neurotransmitters, and providing structural support.

What are the two main categories of neurotransmitters?

Neurotransmitters can be categorized into small molecule transmitters and neuropeptides, based on their structure and function.

How do synaptic vesicles contribute to neurotransmission?

Synaptic vesicles store neurotransmitters and release them into the synaptic cleft in response to action potentials.

What is synaptic integration?

Synaptic integration is the process by which multiple synaptic inputs are combined at the postsynaptic neuron to determine its action potential firing.

What is the primary role of neurotransmitter receptors?

Neurotransmitter receptors mediate the effects of neurotransmitters by initiating cellular responses upon binding.

What is the consequence of increased glutamate activity in the brain?

Increased glutamate activity can lead to excitotoxicity, potentially resulting in neuronal damage or death.

How do neurotransmitters influence sleep patterns?

Neurotransmitters like serotonin and melatonin play crucial roles in regulating sleep-wake cycles.

What role do transporters play in maintaining neurotransmitter levels?

Transporters recycle neurotransmitters from the synaptic cleft back into neurons, maintaining balance and preventing overstimulation.

What effect does chronic stress have on neurotransmitter systems?

Chronic stress can dysregulate neurotransmitter systems, leading to mood disorders and alterations in behavior.

What are the differences in release mechanisms between classical and unconventional neurotransmitters?

Classical neurotransmitters are released through exocytosis, while unconventional neurotransmitters may diffuse or be released via retrograde signaling.

What function do excitatory neurotransmitters serve in neural circuits?

Excitatory neurotransmitters promote action potentials, facilitating communication and signal transmission between neurons.

How do glial cells modulate neurotransmission?

Glial cells regulate neurotransmitter availability, support neuronal function, and modulate synaptic signaling.