L3: Synapses and the Role of Neurotransmitters

Question 1

What is the primary role of a synapse?

Answer 1

A synapse is the contact point between neurons or between a neuron and another cell, enabling communication between them

Question 2

What is the significance of the resting membrane potential in neurons?

Answer 2

The resting membrane potential, typically around -65 to -70 mV, is the baseline electrical charge of a neuron, essential for the generation of action potentials

Question 3

What is an action potential threshold, and why is it important?

Answer 3

The action potential threshold is the critical level of depolarisation a neuron must reach to initiate an action potential, enabling neural communication

Question 4

Describe the term “hyperpolarisation” and its effect on neurons

Answer 4

Hyperpolarisation occurs when the inside of a neuron becomes more negative, making it less likely to fire an action potential, thus inhibiting the neuron

Question 5

What is a synaptic vesicle, and what role does it play in neurotransmission?

Answer 5

Synaptic vesicles store neurotransmitters and release them into the synaptic cleft upon fusion with the presynaptic membrane during exocytosis

Question 6

Define “exocytosis” in the context of neurotransmission

Answer 6

Exocytosis is the process by which synaptic vesicles fuse with the presynaptic membrane to release neurotransmitters into the synaptic cleft

Question 7

What is synaptic cleft, and what occurs there during neurotransmission?

Answer 7

The synaptic cleft is the small gap between the presynaptic and postsynaptic cells where neurotransmitters are released and bind to receptors

Question 8

Name the two types of synapses and how they differ

Answer 8

• Chemical synapses (use neurotransmitters to communicate and are unidirectional)
• Electrical synapses (use gap junctions for direct ion flow and allow bidirectional communication)

Question 9

What is the difference between excitatory and inhibitory neurotransmitters?

Answer 9

Excitatory neurotransmitters increase the likelihood of an action potential in the postsynaptic neuron, while inhibitory neurotransmitters decrease it

Question 10

What are the two main signalling mechanisms for neurotransmitters at the synapse?

Answer 10

• Ionotropic receptors (fast, involve direct ion flow)
• Metabotropic receptors (slower, use G-proteins to indirectly affect cell excitability).

Question 11

What are ionotropic receptors, and how do they function?

Answer 11

Ionotropic receptors are ligand-gated ion channels that open quickly upon binding a neurotransmitter, allowing ions to flow directly into the postsynaptic cell

Question 12

How does a metabotropic receptor differ from an ionotropic receptor?

Answer 12

Metabotropic receptors use G-protein-coupled mechanisms to trigger intracellular signalling cascades, resulting in slower but longer-lasting effects than ionotropic receptors

Question 13

What are G-protein-coupled receptors (GPCRs), and how do they function in neurons?

Answer 13

GPCRs are metabotropic receptors that activate intracellular G-proteins when bound to a neurotransmitter, leading to various cellular responses

Question 14

What is an action potential and how does it propagate?

Answer 14

An action potential is a rapid change in membrane potential that travels along the axon, initiated by depolarization due to sodium ion influx

Question 15

Describe the term “neurotransmitter receptors” and their role

Answer 15

Neurotransmitter receptors are proteins on the postsynaptic membrane that bind neurotransmitters, triggering changes in the postsynaptic cell’s excitability

Question 16

How are neurotransmitter signals terminated at the synapse?

Answer 16

• Reuptake into the presynaptic neuron
• Enzyme degradation
• Diffusion away from the synapse

Question 17

Define neurotransmitter reuptake and its importance

Answer 17

Neurotransmitter reuptake is the process by which neurotransmitters are absorbed back into the presynaptic neuron, terminating the signal and recycling the neurotransmitter

Question 18

What are glial cells and what roles do they play?

Answer 18

Glial cells support neurons by providing structural scaffolding, metabolic support, insulation, and facilitating some signalling processes

Question 19

Describe the structure of a typical neuron

Answer 19

A neuron has a cell body (soma), dendrites for receiving input, an axon for transmitting impulses, and an axon terminal that connects to other cells

Question 20

What is the function of the axon hillock?

Answer 20

The axon hillock is where action potentials are initiated, as it integrates incoming signals and determines whether the neuron will reach threshold to initiate an action potential

Question 21

Describe the term “axon” and its function

Answer 21

The axon is a long projection from the neuron’s cell body that conducts action potentials to the axon terminals, enabling communication with other cells

Question 22

Define the term “axon terminal” and its function

Answer 22

The axon terminal is the end of an axon where neurotransmitters are stored and released to communicate with other neurons or cells

Question 23

What neurotransmitter is primarily excitatory in the central nervous system?

Answer 23

Glutamate is the major excitatory neurotransmitter in the CNS

Question 24

What is the main inhibitory neurotransmitter in the central nervous system?

Answer 24

GABA (gamma-aminobutyric acid) is the primary inhibitory neurotransmitter in the CNS

Question 25

What is a GABA receptor and what effect does it have?

Answer 25

A GABA receptor binds gamma-aminobutyric acid (GABA) and typically causes an inhibitory effect by allowing chloride ions to enter, hyperpolarizing the cell

Question 26

How does calcium influence neurotransmitter release at the synapse?

Answer 26

Calcium enters the presynaptic neuron upon depolarization, triggering vesicles to release neurotransmitters into the synaptic cleft

Question 27

What is the significance of calcium ions (Ca²⁺) in neurotransmitter release?

Answer 27

Calcium ions enter the presynaptic terminal during an action potential, triggering synaptic vesicles to release neurotransmitters into the synaptic cleft

Question 28

What are gap junctions and where are they commonly found?

Answer 28

• Gap junctions are protein channels that directly connect adjacent cells
• Commonly found in cardiac tissue and during neuronal development

Question 29

What is the role of gap junctions in the heart?

Answer 29

Gap junctions allow rapid ion exchange between cardiac cells, enabling synchronized heart contractions

Question 30

What is the neocortex and its role in the brain?

Answer 30

The neocortex is the outer layer of the brain involved in high-order functions like thought, sensory perception, decision-making, and motor commands containing a high density of neurons

Question 31

What are dendrites, and what is their primary function?

Answer 31

Dendrites are branched projections from a neuron’s cell body that receive input from other neurons and transmit signals toward the cell body

Question 32

What are dendritic spines, and why are they important?

Answer 32

Dendritic spines are small protrusions on dendrites that help receive synaptic inputs and play a role in learning and memory

Question 33

Describe the function of the autonomic nervous system and its branches

Answer 33

The autonomic nervous system controls involuntary functions with branches: sympathetic (activates fight-or-flight), parasympathetic (rest-and-digest), and enteric (gastrointestinal control)

Question 34

Name two well-known neurotransmitters involved in the autonomic nervous system

Answer 34

• Norepinephrine (noradrenaline)
• Acetylcholine

Question 35

What is norepinephrine’s role as a neurotransmitter?

Answer 35

Norepinephrine modulates arousal, alertness, and the body’s response to stress

Question 36

Explain the function of acetylcholine in the nervous system

Answer 36

Acetylcholine is a neurotransmitter involved in muscle activation, autonomic nervous system function, and cognitive processes

Question 37

What is an example of a neurotransmitter that can have both excitatory and inhibitory effects?

Answer 37

Acetylcholine can be excitatory at neuromuscular junctions but inhibitory in the heart

Question 38

What is myelin, and why is it important?

Answer 38

Myelin is an insulating layer around axons that speeds up the transmission of electrical impulses along the neuron

Question 39

Explain the role of the presynaptic and postsynaptic cells in neurotransmission

Answer 39

The presynaptic cell releases neurotransmitters, while the postsynaptic cell receives the signal via receptors, initiating a response

Question 40

Describe the term “postsynaptic density” and its importance

Answer 40

Postsynaptic density is a protein-dense region in the postsynaptic membrane that anchors receptors, essential for effective neurotransmitter binding and signalling

Question 41

What are Schwann cells, and what do they do?

Answer 41

Schwann cells are glial cells in the peripheral nervous system that form myelin around axons, aiding in rapid signal conduction

Question 42

What is dopamine, and what roles does it play in the body?

Answer 42

Dopamine is a neurotransmitter involved in reward, motivation, motor control, and several other brain functions

Question 43

What are purinergic neurotransmitters, and give an example

Answer 43

Purinergic neurotransmitters include molecules like ATP, which act on purinergic receptors involved in various signaling pathways

Question 44

What are motor neurons, and what function do they serve?

Answer 44

Motor neurons transmit signals from the brain and spinal cord to muscles, causing movement

Question 45

What is a pseudo-unipolar neuron, and where is it commonly found?

Answer 45

A pseudo-unipolar neuron has one axon that splits into two branches, typically found in sensory neurons

Question 46

What are neuropeptides, and give an example.

Answer 46

Neuropeptides are small protein-like molecules used as neurotransmitters, such as endorphins, which modulate pain and pleasure

Question 47

What is synaptic plasticity, and why is it important?

Answer 47

Synaptic plasticity is the ability of synapses to strengthen or weaken over time, crucial for learning and memory

Question 48

How does the brain’s cortical folding relate to neuron density?

Answer 48

The brain’s cortical folding increases surface area, allowing for a high density of neurons in a compact space, enhancing processing power

Question 49

What is the significance of neurotransmitter vesicle recycling?

Answer 49

Recycling neurotransmitter vesicles ensures a continuous supply of neurotransmitters for repeated signalling, essential for sustained synaptic transmission

Question 50

Explain the concept of neurotransmitter specificity

Answer 50

Neurotransmitter specificity means each neurotransmitter binds to specific receptors, ensuring precise signalling pathways

Question 51

How does serotonin affect mood and where is it commonly released?

Answer 51

Serotonin helps regulate mood, sleep, and appetite, and is commonly released in brain areas associated with mood regulation

Question 52

What is acetylcholinesterase, and what role does it play in neurotransmission?

Answer 52

Acetylcholinesterase is an enzyme that breaks down acetylcholine in the synaptic cleft, terminating its action and allowing reuptake or breakdown

Question 53

Explain what an interneuron is and its function in the nervous system

Answer 53

Interneurons connect sensory and motor neurons within the CNS, playing a critical role in reflexes and neural circuits

Question 54

Explain what a “secondary messenger” is in neurotransmitter signalling

Answer 54

A secondary messenger transmits signals from receptors on the cell surface to target molecules inside the cell, amplifying the original signal