What is the difference between the signals trasmitted by neurons and synapses
Neurons: Cells in nervous system
- Electrical signals “Action Potential” trasmitted along axon
Synapses: Neurons meet
- Chemical signals “Neurotrasmitters” trasmitted between neurons
How do neurons in the CNS, PNS, ENS communicate? What happens if they don’t have it?
ALL neurons communicate via. NT/NM
- Modulate neural activity
- Synaptic plasticity (i.e. building new synapses/alter function of old synapses)
Without these chemical signals (NT/NM)
- Action of a neuron would not influence any other neuron
Difference between NT and NM
NT:
- Excitatiory/Inhibitory
- Rapid (ms)
- Precise
- Point-to-point
NM:
- Slower (ms-s) that alter subsequent processes of neurons
How many neurons are there in the CNS
100 billion neurons in the CNS
What are hormones
Signaling molecules produced by glands and transported through the blood to regulate physiology (muscles, neurons etc) and behaviour.
4 differencses between NT and hormones
NT
- Nervous system
- Tramission between neurons (Across synapse)
- Target cells can be specific neurons or other cells
- Generally fast (ms), though sustained NT release can lead to more sustained changes in brain
Hormones
- Endocrine system
- Travel by blood
- Target cells can be some distance from endocrine gland
- Much slower, ranging from few seconds to days
- Also directly modulate NT levels and function
What is the blood-brain barrier? (Location, Function)
Location
- Exists within 600km of blood vessels in the CNS
Function
- Prevents many substances from passing between blood and brain.
- Dugs, natural chemicals and foreign infections cant pass through (but is not perfect – small amounts of many things still get through).
- However, multiple other avenues for controlled passage between blood and nervous system exist.
What is the PNS (Location, Function)
Location
- Nerves and glanglia outside of the brain and spinal cord
Function
- Receives sensory information about body position, pain and temperature etc
- Sends messages from the brain to control muscles and movement.
What is the ENS. Locaton, how many neurons, properties, function
Location
ENS (2nd brain) is part of the PNS
How many neurons
- Contains 100million neurons
Properties
- Has its own reflexes and senses and can act independently of the brain
- Does not engage in consciousness, philosophy, decision-making despite being so much like our “main” brain.
- Only part of the PNS that can act autonomously
- Nearly every neurotransmitter found in the brain is also found in the gut
- 95% of all serotonin is found in the gut
- Does not just help digestion
- 90% of connections between the brain and gut go from the gut to the brain.
Function
- Helps digestion
- Plays a major role in emotions & stress (butterflies in our stomachs) & also clinical depression / anxiety.
What are the 3 systems in the gut-brain interaction (And elaborate)
- Peripheral Serotonin
* Cells in gut produce serotonin, effecting on brain - Immune System
* Intestinal microbiome prompts immune cells to produce cytokines, effecting neurophysiology - Bacterial Molecules
* Microboes produce metabolites (e.g. butyrate), effecting activity of cells in blood-brain barrier
What is microbiome and microbiota
Microbiome
- Combined genetic material of microbiota
- > 100 times more genes than the human genome
Microbiota
- Trillions of bacteria and other microorganisms in the gut
- Impacts brain, behaviour, cognition
- Shy mice became “adventurous” after receiving gut microbiota transplant from social mice
How does the gut microbiota influence the brain, and how does the brain influence the gut (neurophysiologically)
- Gut microbiota modulates development and homeostasis of the CNS through immune, circulatory and neural pathways.
- The CNS impacts the gut via neural and endocrine response
What is the link between sickness behaviour and brain
Bidirectional link between brain to immune and immune to brain
Activation of the immune system due to illness triggers a series of temporary behavioural, cognitive and emotional changes including:
- Fever
- Increased sleep & general lethargy
- Depressed mood
- Hyperalgesia (increased pain sensations)
- Loss of interest in usual activities
- Anorexia (reduced appetite)
- Decreased social interaction
- Impaired concentration
What is sickness behaviour belived to be triggered by?
Triggered by cytokines released by the body in response to infection and travel to the brain
What are cytokines and what are some properties?
Cytokines
- Group of small proteins important in cell signaling
- Released by cells and influence behaviour of other cells
- Too big to pass through the blood-brain barrier
- Believed to enter the brain indirectly or trigger new cytokines to be released within the brain.
In experiments where volunteers were injected/infected with the common cold, what do they show impaired performance on? What do people with more severe illness have?
Impaired:
- Visual detection
- Hand-eye coordination
- General cognitive tasks
- More accidents are found to occur at work when employees are sick.
People with more severe illness had:
- Negative mood
- Fatigue
- Memory
- Attention
What is the evolution theory proposed behind sickness behaviour? What is the theory behind excessive sickness behaviour? What else can it trigger?
- Organised strategy evolved to conserve energy and improve the fight against infection
- Excessive sickness behaviour (and cytokine release) > neuropsychiatric syndromes (fatigue/MDD). Theory is based mainly on overlapping symptoms and is still speculative.
- Cytokine release can also trigger “the stress response” and stress can be linked to changes in immune function
What is an example of our integrated brains
Kissing
- Increases risk of transmitting illness
- Allows transfer of hormones like testosterone to passed on to directly increase arousal
- Others suggest it is a show of trust and close bond (either between the individuals or to the public)
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W1L1 - Introduction18
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W1L2 - Stress & The Brain24
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W2L1 - Fear Conditioning and Extinction16
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W2L2 - Sex Hormones19
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W3L1 - Motor Control14
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W3L2 - Central Control of Movement16
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W4L1 - Brain Body Connection Failure21
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W4L2 - Using knowledge of brain body interactions14
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W5L1 - Introduction to Sleep24
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W5L2 - Homeostatic and Circadian regulation of sleep20
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W6L1 - Neurobiology of Sleep13
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W6L2 - Sleep Disorders13
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W7L1 - Function of Sleep22
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W7L2 - Function of Sleep (2)26
