Week 2 Flashcards
Neurons
- Basic unit of the nervous system is the neuron
- Use chemical transmission and electrical impulses
- They process, receive and transmit signals
- established networks are faster and more efficient due to myelination
Myelination
White matter that acts as insulation in a neuron
Assists in carrying electrical chare
Neurogenesis
The birth of new neurons through cell division
Death of Neurons
- Don’t appear to have a lifespan
- Die off due to biochemical changes like:
- Too much cortisol (stress)
- Lack of blood flow
- Harmful free radicals that cause degenerative disease
Neural Systems
- Nervous System has two branches
- Peripheral Nervous System -
- Autonomic Nervous System
- Somatic Nervous System
- Central Nervous System - Brain & Spinal Chord
- Peripheral Nervous System -
ANS & SNS communicate information between the CNS and the organs, glands & body.
Autonomic Nervous System
- Has two branches:
- Sympathetic Nervous System
- Parasympathetic Nervous System
- SNS activated in response to threats (fight or flight)
- PNS acts as a balance and supports return to homeostasis (rest & digest)
Vagus Nerve
- Parallel to the PNS
- Dedicated to fine tuning bodily reactions
- Especially used in social situations
Brain Stem
- Fully Functional at birth
- Regulates temperature, heart rate and basic reflexes
- Shaped by genetic history
Cerebral Cortex
- Is Experience Dependent - shaped by countless interactions with the world
- We learn to adapt to the environment using this cortex
- As we for ideas, experiences and mental representations our cortex becomes more and more complex
Lateralisation
- Cerebral Cortex has two halves that seem to have different functions
- Left side processes information using logic - develops around 2 years
- Right side processes information holistically with whole context - fully developed at birth
- Language also processed laterally:
- Right side - communicates broadly and non verbal cues
- Left side - Involved in complex linguistics
Corpus Collosum
- Connects left and right cortex hemispheres to support communication
- Also acts as barrier to block any conflicting information
- Often left & right hemispheres have competing needs
Lobes
- Four Lobes in the Brain
- Frontal - Motor behaviour, language, directed attention
- Parietal - Links senses with motor function, creates sensation of body in space
- Occipital - Visual processing
- Temporal - Auditory processing, receptive language, memory functions
Limbic System
Sits between Brain Stem and Cortex
Involved with learning, memory, motivation and emotion
We focus on hippocampus and amygdala
Amygdala
- Key role in developing neural networks
- Attachment and appraisal and expression of emotions
- Looks at information from thalamus - sight smell, sound, kinaesthetic information
- If threatened transmits to hypothalamus to release stress hormones
- This triggers fight or flight
Neurotransmitters
- Chemical messengers to communicate between neurons
- Dopamine, Serotonin and Norepinephrine regulate cognitive process and emotion
- Too much dopamine leads to depression
- Too much norepinephrine leads to anxiety
- Serotonin functions in arousal and mediates mood
Neuropeptides
Regulate pain, pleasure and behavioural reward
Chemicals include endorphins, oxytocin, vasopressin
Endogenous endorphins serve as analgesic
Also connected to dissociation and self harm behaviour
Cortisol
Stress Hormone produced in adrenal glands
Enhances memory, energy production and helps restore homeostasis after stressful situations
Prolonged stress correlated with memory deficits, poor regulation of homeostasis and reduction in Hippocampus and Amygdala
Neural Plasticity
- Experience sculpts the brain
- Neurons that fire together wire together
- Neurons grow in strength and connectivity to create enduring networks
- Synapses that are not used are eliminated if they become inactive
- Use it or Loose it!!
Synaptogenesis
- Is genetic rapid expansion in synapse formation
- Deals with bombardment of sensory input
Synaptic Pruning
- Reduction in number of synaptic connections
- This enables more, synaptic configurations and more efficient brain function
- This is led by experience; connections not used are pruned
Cortisol Inhibition and Conscious Control
- As cortex develops so do top down circuits in neural network
- These help inhibit reflexes and bring body and emotions to be under cortical control
- This process is central to emotional regulation
Vagus Nerve
- Major part of parasympathetic system
- Controls mood, immune response, digestion and heart rate
- Connects brain to gastrointestinal tract
- Vagus Nerve Stimulation may support treatment of depression, PTSD and inflammatory bowel disease
Bi-Directional Communication
- Communication between brain and gastrointestinal track goes both ways
- Complex system which includes the Vagus Nerve
Vagus Nerve Anatomy
- Longest nerve in the body
- Runs from skull, pharynx, larynx, thorax, heart and intestines’
- Regulates organ functions like digestion, heart rate and respiratory rate
- Also vasomotor activity like reflex actions like coughing, sneezing, swallowing and vomiting
Polyvagal Theory
- Evolution of the Autonomic Nervous System provides parts of the CNS to adapt to behavioural strategies
- Our physiology limits the range of behaviours and psychological experience.
Vagus Nerve in functions of ANS
- Main contributor to the parasympathetic nervous system
- Brings information from gut, live, heart and lungs to brain
- Suggests inner organs are major sources of sensory information to the brain
Regulation of ANS
- PNS causes dilation of blood vessels and bronchioles and salivary glands
- SNS constricts blood vessels, intestines and urinary sphincters and increases heart rate
- PNS increases bowel motility and glandular secretion
- SNS activity reduces intestinal activity and blood flow reduction, allows higher blood flow to hear and muscles during stress
Stress & Brain-Gut Axis
- Vagal afferent pathways activate or regulate HPA Axis
- Co-ordinates adaptive response to any stressors
- Environmental Stress
- Elevated Systemic Proinflammatory Cytokines
- Activated through secretion of Adrenocoricotropic hormone (ACTH) from Pituitary Gland
- Releases cortisol from adrenal glands
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Cortisol
Stress hormone that affects brain, bones, muscles and body fat
HPA Axis
- Hypothalamus ⇒ Pituitary Gland ⇒ Adrenal Glands = Makes Cortisol; Ephinephrine; Norepinephrine
Proinflammatory Cytokines
- Activates the HPA Axis Pituitary Glands
- Secrete Adrenocoricotropic Hormone (ACTH)
- This stimulation leads adrenal glands to release cortisol
- Involved in the up-regulation of inflammatory reactions
- There much evidence that these cytokines are involved in the process of pathological pain
Vagus Nerve Stimulation
Application of electric impulses directly to the Vagus Nerve is being used to treat depression, anti-inflammatory disease and epilepsy
Gut Microbiota
- Psychobiotics with anti-inflammatory effects could treat:
- anti-depressive effects
- Anxiolitic Effects
- Differences in gut microbes in people with depression have been documented
Meditation
- Increased meditation has been shown to increase vagal tone.
- Social connections mediate this also
- People with chronic pain, depression, anxiety and chronic pain show benefit in improving symptoms using meditations
Yoga
- Some yoga practices stimulate the Vagus Nerve
- This increased Vagal Tone improves:
- Autonomic regulation
- Cognitive Functions
- Mood and Stress Coping
Apoptosis
- When neurons die due to a process of neural pruning
- Considered a normal part of an organism’s growth and development
Neurogenesis in Humans
- Can be regulated by environment and experience
- Found in hippocampus, amygdala, striatum and cerebral cortex
Afferent Neurons
- A structure or process that grows or progresses inward or towards a destination
- Sends messages from the nervous system to the brain
Efferent Neurons
the nerve fibers responsible for carrying signals from the brain to the peripheral nervous system in order to initiate an action
Sympathetic Nervous System
- Controls activation of the nervous system in response to a threat
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Smart Vagus System
- Operates parallel to the Parasympathetic Nervous System
- Fine tunes bodily reactions particularly in social situations
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Cingulate Cortex
- an arch-shaped convolution situated just above the corpus callosum.
- A component of the limbic system
- Involved in processing emotions and behavior regulation.
- Helps to regulate autonomic motor function.
Insula Cortex
- Long-neglected brain region that is crucial to understanding what it feels like to be human
- The wellspring of social emotions,
- Lust, disgust, pride, humiliation, guilt and atonement.
Limbic System
- Central to learning, motivation, memory and emotion
- Holds the amygdala and the hippocampus
Neuromodulators
Regulate effects of neurotransmitters on neurons
Amino Acids
Glutamate
Major amino acid that excites the brain to trigger neuroplasiticity and learning
NMDA
N-methyl-D-aspartate
regulates long term potentiation and long term depression
Believed to shape the relationship between neurons to drive learning
Monoamines
Neurotransmitters like dopamine, serotonin and norepinephrine
Are efferent in nature
Cortisol
- A stress hormone produced in adrenal glands
- Involved with glucose metabolism
- Glucocorticoid receptors (GRs) found in almost all tissue in body
- In short bursts enhances memory, mobilises energy and restores homeostasis after stress
- Too much cortisol can weaken immune system and prevent T-cells from increasing
Epigenetics
- The transformation of cells from being undifferentiated into a specific purpose
- Study of how our genotype turns into our phenotype
HPA Axis
- Hypothalamic-pituitary-adrenal Axis
- Regulates our response to stress
Neural Darwinism
- Selectionist theory of brain development and function believed to relate to consciousness
- Cells reach out to other cells to create new networks that fire together and wire together
Cortex Development
- Develops in a Top-Down fashion
- Experiences trigger neural activity in the brain
- This changes and builds the cortex
Autonomic Nervous System
We are hard wired to connect to the world
ANS is always on the alert “Is this safe?
Neuroception
The way our ANS searches for danger cues without disturbing our conscious thought
Our brain searches for meaning in everything and this drives the story of our daily life
ANS Anatomy
ANS divided into two parts: Sympathetic and Parasympathetic Systems
This system is focused on “in service of survival”
Sympathetic Nervous System
- Found in the middle of the spinal chord
- Pathway that prepares us for action
- Responds to danger cues and triggers
- Releases adrenaline which fuels fight or flight
Parasympathetic Nervous System
Found in the Vagus Nerve which is the largest nerve in the body
Vagus means wanderer
Information travels in two directions through lungs, heart, diaphragm and stomach then back up to neck throat eyes ears
Vagus Nerve
- Divided into Ventral and Dorsal vagal pathway
- Ventral responds to cues of safety and social connection
- Dorsal responds to dues of extreme danger
- Takes us out of connection and awareness
- Put us in protective state of collapse
- when we feel numb, disconnected, not here dorsal vagus has control
ANS Evolutionary Development
The hierarchy of our ANS is anchored in evolution
Dorsal Vagal Pathway of the PNS is the oldest pathway we have
Immobilisation response lies here
Sympathetic Branch developed next followed by Ventral Vagal Pathway
This brought social engagement that is unique to mammals
The Autonomic Ladder
- Top of Ladder - Ventral Vagal Pathway
- Feelings of safety, autonomy and overall sense of wellbeing
- Moving Down Ladder - Sympathetic Branch Activates
- Neuroception triggers sense of danger
- Fight or flight happens and we begin to mobilise
- Autonomic states like heart and breath rate increase
- World seems dangerous
- Bottom of the Ladder - Dorsal Vagal Pathway of Parasympathetic Branch
- Oldest pathway of response
- Feel trapped and taking action doesn’t work
- Hopeless, foggy, too tired to think, dissociation
- Mind and body in conservation mode
- Health problems like fibromyalgia, diabetes, chronic fatigue, low blood pressure
ANS Integration
- When ANS, PNS and Enteric systems all work together use the analogy of a home:
- Dorsal Vagal runs the basic utilities works in background, when things run smoothly, we function automatically, kind of like sleep mode. just enough to sustain life.
- Sympathetic Branch is the home security system; stands at attention and reacts to emergencies; triggers immediate response and returns to standyby
- Ventral Vagal allows us to soak in and savour the environment; we rest and renew when all is well, we trust that automatic systems are running correctly; physically and emotionally connected to others
ANS Mapping Personal Responses
- The social skills connected here lead us to attend to our world
- We map our responses and this leads to tracking and awareness
- When we are aware of tracking we can intentionally fine tune our ANS
- We can successfully navigate our quest for safety and connection.
