4/21/25

Flashcards covering key concepts and facts from the lecture on gut-brain axis and microbiota.

What is microbiota?

Microbiota refers to the micro-organisms, including bacteria, fungi, and viruses, that live in the human body.

How many species of bacteria do humans have in their guts?

Humans have about 1000-2000 different species of bacteria in their guts.

What are some functions of gut microbiota?

Gut microbiota modulate gut movement, metabolize complex lipids and starches, affect nutrient absorption, produce vitamins, and regulate immune responses.

What is the gut-brain axis?

The gut-brain axis is the bidirectional communication system between the gut microbiota and the brain, affecting areas such as mood, behavior, and immune response.

What is the role of microbial products in the immune pathway?

Microbial products such as short-chain fatty acids influence immune homeostasis and local responses, shaping inflammatory states in the body.

How does the gut microbiota influence brain development?

Gut microbiota plays a role in fetal brain development, immune system maturation, synaptic connections, and overall brain architecture.

What factors can affect the gut microbiota?

Diet, antibiotics, mode of delivery (vaginal vs. C-section), stress, and sleep patterns can significantly influence gut microbiota composition.

What impact does gut microbiota have on mental health?

Altered gut microbiota populations are associated with conditions such as depression, anxiety, and may influence susceptibility to disorders like autism and Alzheimer’s.

What is the effect of germ-free conditions on mice?

Germ-free mice exhibit less total body fat, hyper-responsiveness to stress, deficits in memory tasks, and altered social behaviors compared to conventional mice.

How do diet and antibiotics impact gut microbiota?

Breast-fed infants have beneficial microbiota, while formula-fed have more diversity; antibiotics can disrupt microbiota recovery, increasing disease risks.

How do gut microbes affect hormones?

By signaling through enteroendocrine cells to release neuropeptides like GLP1 and serotonin.

Can gut bacteria produce neurotransmitters?

Yes, some bacteria can synthesize neurotransmitters.

How does stress affect the microbiota?

Stress activates the HPA axis and alters gut microbial composition.

What happens to HPA function in germ-free mice?

It is altered, showing increased stress hormone levels.

What nerves are involved in gut-brain neural signaling?

Vagal and spinal afferents.

What do vagus nerve afferents control?

Satiety, hunger, and energy metabolism.

What do vagus nerve efferents control?

Gastric acid, enzymes, stomach capacity, and blood glucose.

What are characteristics of germ-free mice?

Less body fat, higher stress hormones, social/memory deficits.

What can fecal transplants in germ-free mice do?

Transfer behaviors and partially restore HPA function.

When must colonization occur to normalize stress response?

During a critical early-life window.

How does diet affect gut microbiota?

Breastfeeding promotes beneficial bacteria; formula feeding is more diverse but less stable.

How do antibiotics affect the microbiota?

They can cause long-term alterations, especially if used early in life

What is the impact of birth method on microbiota?

C-section delays colonization and may raise risk for disease.

How else can microbiota be influenced?

By sleep, stress, neurological injury, and behavior.

How does microbiota diversity relate to behavior?

Greater diversity is linked to better memory and reduced anxiety.

Can behavior be transferred via gut microbiota?

Yes, fecal transplants can transfer traits like adventurousness.

What is the role of Prevotella in the brain?

Associated with increased white matter connectivity.

How do antibiotics affect the microbiota?

They can cause long-term alterations, especially if used early in life.

What is the microbiota?

Microorganisms (bacteria, fungi, viruses) that live in the human body.

How diverse is the gut microbiota?

It contains ~1000–2000 species and ~1 trillion bacteria.

How many genes are encoded by the gut microbiota?

Over 3 million.

How is gut microbiota shared?

Among family and social groups.

What are functions of gut microbiota?

Regulate gut movement, absorb nutrients, synthesize vitamins, modulate BDNF, immune response, and energy metabolism.

What vitamins and minerals are influenced by microbiota?

Vitamin K, calcium, iron, biotin, and folate.

When does gut microbiota colonization begin?

At birth through vaginal delivery and early contact.

When does the infant microbiota become adult-like?

Between ages 1 and 3.

Whose microbiota does an infant resemble?

The mother and family.

What is the gut-brain axis?

Bidirectional communication between gut and brain.

What are afferent pathways in the gut-brain axis?

Gut to brain via microbial products, hormones, immune signals.

What are efferent pathways in the gut-brain axis?

Brain to gut via autonomic, endocrine, and immune systems.

How do microbial metabolites affect immunity?

They regulate cytokines and brain inflammation.

How does brain inflammation affect the gut?

It alters microbiota, creating a feedback loop.

How do gut microbes affect hormone release?

Through metabolites like bile acids and SCFAs that signal hormone-producing gut cells.

What hormones are influenced by microbiota?

GLP1, serotonin.

Can microbes produce neurotransmitters?

Yes.

How does stress affect the microbiota?

Stress alters HPA axis function and microbiota composition.

What happens to HPA axis function in germ-free mice?

It is altered.

How do microbial signals affect the nervous system?

They act on enteric, vagal, and spinal neurons.

What does the vagus nerve control afferently?

Hunger, satiety, metabolism.

What does the vagus nerve control efferently?

Gastric function, enzyme release, blood glucose.

What are characteristics of germ-free mice?

Reduced body fat, high stress response, memory and social deficits.

How can fecal transplants affect germ-free mice?

They can alter behavior and restore physiology.

When must gut colonization occur for normal HPA development?

During a critical early-life window.

What factors affect the microbiota?

Diet, antibiotics, birth method, sleep, stress, behavior.

How does birth method affect microbiota?

Vaginal birth provides early colonization; C-section delays it.

How does microbiota diversity relate to behavior?

Higher diversity is linked to better memory and reduced anxiety.

Can behavior be transferred through microbiota?

Yes, via fecal transplants.

What is Prevotella associated with?

Greater white matter connectivity in the brain.

What neurological conditions are linked to gut microbiota?

Stroke recovery, autism, Alzheimer's, Parkinson's.

How do antibiotics affect the microbiota?

They can cause long-term alterations, especially if used early in life.