L.2.4 Flashcards
What are brain rhythms
Brain rhythms are patterns of brain activity that align with environmental and biological changes
how do brain rhythms relate to environmental factors?
these rhythms are influenced by factors such as temperature, day/night cycles, and tides.
What are some examples of brain rhythms?
Brain rhythms include sleep-wake cycles, breathing patterns, steps while walking, and stages of night sleep
What is the function of an Electroencephalogram (EEG)?
An EEG measures brain activity, particularly useful for detecting abnormal brain rhythms
How does an EEG detect brain activity?
- An EEG involves placing a mesh of electrodes on the head to detect electrical activity from neurons
- signals are then analyzed to identify abnormal brain patterns.
Why are EEGs good for detecting epilepsy?
The synchronized firing of many neurons produces a large enough signal to be detected on the scalp
Why is it difficult to record EEG signals from deeper brain layers?
harder to detect their signals via EEG, as the signal needs to travel through several cortical layers to reach the scalp.
What are the basic requirements for signal detection in EEG?
- Population Synchrony
- Parallel Alignment:
What is population synchrony
A large group of neurons must fire synchronously to generate a strong enough electrical field
What is parallel alignment
Neurons must be aligned in parallel to combine their electrical signals effectively.
What happens when neurons fire in synchrony for EEG signal generation?
- When neurons fire synchronously, it creates a strong, detectable EEG signal with high amplitude
- allows the signal to be measured effectively at the scalp
What happens when neurons fire irregularly,
- the EEG signal becomes weak because increases and decreases in electrical activity cancel each other out
how does irregular neuron firing affect EEG signals?
low amplitude and meaningless signals.
What factors influence the amplitude of EEG signals?
- Number of active neurons:
- Total excitation level in neurons
- Timing of activity
How does the number of active neurons influence amplitude of EEG signals
More active neurons generate a stronger signal.
How does the total excitation level in neurons influence amplitude of EEG signals
Higher excitation levels contribute to a stronger signal.
How does the timing of activity influence amplitude of EEG signals
More synchronous firing of neurons results in a stronger signal.
What does the alpha rhythm in EEG indicate
- the alpha rhythm (8-13Hz) occurs when a person is awake but has their eyes closed
- moderate synchronization without visual input
What does the beta rhythm in EEG indicate
- The beta rhythm (14-60Hz) occurs during mental activity and attention, especially when the eyes are open
- associated with active thinking and sensory processing
Why is the amplitude low for beta rhythm
The amplitude is lower, as brain activity is less synchronized
What do theta waves in EEG indicate
Theta waves (4-7Hz) indicate drowsiness, sleep
Why do theta waves have moderate amplitude
synchronization changes.
What do delta waves in EEG indicate
Delta waves (<4Hz) occur during deep, non-REM sleep.
What are the amplitude of delta waves like
They have very slow frequency and high amplitude due to synchronized neurons, as minimal external environmental processing occurs
What EEG patterns are observed during awake state
alpha (eyes closed) and beta (eyes open, active attention)
What EEG patterns are observed during REM sleep
Low amplitude and fast activity, indicating unsynchronized brain activity, associated with dreaming
What EEG patterns are observed during non-REM sleep
Light sleep: Theta waves.
Deep sleep: Delta waves (slow, high amplitude, synchronized neurons).
What are the 2 ways synchronisation of neurons is generated
- pacemaker activity
- collective interaction
What is pacemaker activity
when certain neurons (pacemakers) generate rhythmic discharges that help synchronise the other cells
What is the collective interaction in neuron synchronisation
neurons synchronise their firing based on the activity and rhythm of nearby neurons
How does the thalamus act as an oscillator
they have voltage-gated ion channels that enable rhythmic firing without external input
How does the thalamus act as an oscillator during awake state
when depolarised, the thalamic neurons exhibit continuous activity
How does the thalamus act as an oscillator during the sleep state
when hyperpolarised the thalamic neurons activate low threshold ca2+ channels that produce rhythmic bursts
What are the 3 main functions of brain rhythms
- regulates what sensory information reaches conscious awareness
- activity coordination of different cortical regions
- meaningless by product of feedback circuits and connections
Why do prey animals sleep in short bursts
- remain vigilant for survival
Why do dolphins and seals have unihemispheric sleep
it allows them to stay alert to environmental threats or come up to the surface to breathe
What is unihemispheric sleep
one hemisphere of the brain sleeps while the other remains awake
Why is it important for predatory animals to have uninterrupted sleep cycles
for rest and cognitive processing
What are behavioural criteria for sleep
- reduced motor activity
- decreased response to stimulation
- can easily be interrupted
What is the functional importance of the awake state
active information processing
What is the functional importance of non-rem sleep
physical recovery and memory consolidation
What is the functional importance of rem sleep
consolidating learning
What are the functions of sleep and dreaming
- conserves metabolic energy
- cognition processing
- mental health
What are the characteristics of the awake state in terms of input
External input.
What are the characteristics of the awake state in terms of modulation
Driven by aminergic neurotransmitters like norepinephrine and serotonin.
What are the characteristics of the awake state in terms of activation
high activation
What is the role of histamine in awake state
- contribute to alertness.
- antihistamines contribute to drowsiness
What are the characteristics of non-REM sleep in terms of input
Intermediate (some external processing but primarily internal).
What are the characteristics of non-REM sleep in terms of modulation
Decreased aminergic activity as the brain enters a restful state, with the thalamus beginning to oscillate
What are the characteristics of non-REM sleep in terms of activation
Moderate to low; thalamic and cortical synchrony increases, reflecting deep rest and energy conservation
What are the characteristics of REM sleep in terms of input
internal
What are the characteristics of REM sleep in terms of modulation
Low aminergic activity and high cholinergic activation, especially in brainstem regions.
What are the characteristics of REM sleep in terms of activation
High cortical activation levels, resembling those seen in wakefulness, which results in rapid eye movements and dreaming characteristic of REM sleep
What is anesthesia?
a reversible drug-induced absence of sensation and awareness
How does anesthesia work?
Anesthesia works by using any lipid-soluble agent that depresses the brain in a specific order:
What happens if cortex is under anesthesia
absence of consciousness and awareness
What happens if the spinal cord is under anaesthesia
absence of reflexes and movement)
What happens if the medulla is under anaesthesia
absence of vital autonomic functions like breathing
What is meant by range of anesthetics?
A diverse range of agents with different chemical structures and mechanisms of action
Why is lipid solubility important for anesthetics?
Determines the ability of anesthetics to cross the cell membrane (blood-brain barrier).
What are 2 ways anesthetics can be administered
Can be inhalational or intravenous.
What does it mean if anesthetic is more lipid soluble
More lipid-soluble agents have a faster onset of action.
How do anesthetics interact with membrane proteins?
Anesthetics bind to membrane proteins like receptors and regulate neuronal excitability.
What happens during the global depression of neuronal activity?
Anesthetics cause a global decrease in brain activity, leading to loss of consciousness
How do anesthetics stimulate inhibitory receptors?
- Anesthetics stimulate GABA(A) and glycine receptors in the brain
- allows Cl- ions to flow into neurons, causing hyperpolarisation
- Hyperpolarisation reduces neuronal excitability, creating a sedative and anesthetic effect.
How do anesthetics inhibit excitatory receptors?
- Anesthetics inhibit nicotinic, serotonin, and glutamate/NMDA receptors
- prevents the flow of Ca2+ and Na+ ions into neurons
- Reduced neuronal excitability and a lower likelihood of neurons firing
What does anaesthesia Inhalation entail
Patient breathes in gases; suitable for children and the elderly.
What does intravenous anesthesia mean
Administered intravenously for quick effect.
Name examples of inhalational agents
oxygen, nitrous oxide and Isoflurane & other volatile agents
Why is oxygen used during anesthesia
Maintains breathing during anesthesia
Why is nitrous oxide used during anesthesia
Provides analgesic and anesthetic effects.
Why is isoflurane used during anaesthesia
Act quickly, are controllable, and enable smooth anesthesia with fast recovery.
What are the cons of oxygen use in anesthesia?
- High concentrations increase fire risk
- O2 free radicals causing cellular damage.
What are the pros of using nitrous oxide in anesthesia?
- Highly soluble (35x more than N2), enters blood fast, and acts quickly.
- Wears off quickly, making it controllable
What are the cons of nitrous oxide use?
- High solubility can expand gas-filled spaces, unsuitable for surgeries with gas buildup risks
- Not strong enough as an anesthetic alone but effective for pain relief.
What are the physical properties of inhalational agents?
- expensive
- stable over time; resistant to breakdown.
- Easily converted to gas for inhalation
Why is chemical stability important in anesthesia
chemical stability ensures reliability over time.
Why is vaporability important in anesthesia
Vapourisability allows easy delivery during anesthesia.
What are the chemical properties of inhalational agents?
- Non-irritant: Gentle on lungs and throat.
- low blood solubility: Rapid entry and exit from the bloodstream for fast onset and recovery
- High potency (low MAC): Effective at low concentrations
Why aren’t older inhalational agents (like ether and chloroform) used anymore?
- slow onsets
- Serious side effects (toxicity)
- Newer agents are safer, more effective, and better controlled
how does isoflurorane work?
- Increases GABA activity → hyperpolarization → reduces neuronal excitability.
- CNS depression, leading to loss of consciousness and sensation during surgery
Why is isoflurane important in modern anesthesia?
- Low cost and stability: Makes it accessible and reliable.
- Controlled anesthesia: Depth can be easily adjusted during surgery.
What are the side effects of isoflurane?
- Changes in heart rate and blood pressure.
- Respiratory depression
What is sevoflurane and how does it work?
- Halogenated ether used for general anesthesia
- Increases GABA activity → hyperpolarization → reduces neuronal excitability
What are the side effects of sevoflurane?
Agitation and confusion in some patients after waking
What are the features of sevoflurane?
- High MAC → higher concentration needed for effect.
- Non-irritable to airways
- minimal toxic metabolites
Why are intravenous agents preferred for induction?
- Rapid onset: Induces anesthesia quickly.
What are the pharmacokinetics of IV anesthetic agents?
- Lipid-soluble: Easily cross cell membranes and enter the CNS.
- Quickly distribute to various tissues → short-acting process
What are the potential side effects of IV anesthetic agents?
- Cardiovascular depression: Reduced heart function.
- Respiratory depression: Requires careful monitoring during administration
What is the function of thiopentone
Helps control seizures
What are the side effects of thiopentone
- Cardiovascular and respiratory depression, allergic reactions (e.g., anaphylaxis), affects arterial pressure.
- 10 hours half-life, leading to prolonged presence in the body
What are muscle relaxants, and why are they used?
Induce muscle paralysis for procedures like intubation, surgery, and mechanical ventilation
How do depolarizing muscle relaxants work?
- Mimics acetylcholine, binding to post-synaptic receptors
- Causes rapid, sustained depolarization → muscle contraction → paralysis
- Rapid onset and offset due to short half-life
How do non-depolarizing muscle relaxants work?
- Compete with acetylcholine at receptor sites without activating them
- Block sodium channel opening → prevent muscle contraction → paralysis
- Slower onset and offset
