Psychological medicine week 1 Flashcards
What is consciousness ?
Medically: The state of being aware and responsive to ones surroundings
There are different levels of consciousness
Neurologically speaking what is consciousness ?
Neurologically speaking, the consciousness system is a series of cortical and subcortical brain networks that work in synergy to maintain attention, alertness, and awareness.
What is sleep ?
Sleep is a state of reduced responsiveness to the environment, decreased voluntary muscle activation, and largely inhibited sensory modalities.
Hence, it is a state of altered consciousness.
It is considered to be a restorative process unless its excess or insufficiency interferes with patients’ quality of life.
What is sleep in relation to consciousness ?
Sleep is a physiological state of reduced consciousness.
What is locked in syndrome ?
What is normal loss of consciousness and abnormal loss of consciousness ?
Normal loss of consciousness: sleep
Abnormal loss of consciousness:
- coma
- Anesthesia
- Unresponsive wakefulness syndrome
What is the most common cause of loss of unconsciousness worldwide ?
common cause of unconsciousness worldwide: malaria
In the UK:
- Stroke
- Dementia
- Raised intracranial pressure
- Head Injury
-Epilepsy
- Diabetes
What is the AVPU assessment ?
The AVPU scale (Alert, Voice, Pain, Unresponsive) is a system, which is taught to healthcare professionals and first aiders on how to measure and record the patient’s level of consciousness.
What is Glasgow coma scale ?
The tool we use to assess the level of consciousness is the Glasgow Coma Scale (GCS). This tool is used at the bedside in conjunction with other clinical observations and it allows us to have a baseline and ongoing measurement of the level of consciousness (LOC) for our patients.
- A fully conscious patient has a Glasgow coma score of 15
- A person in deep coma has a Glasgow coma score of 3
A bit more on the Glasgow coma scale …..
What is unresponsive wakefulness syndrome ?
The unresponsive wakefulness syndrome (UWS), formerly known as the vegetative state, is one of the most dramatic outcomes of acquired brain injury.
Patients with UWS open their eyes spontaneously but demonstrate only reflexive behavior; there are no signs of consciousness.
Can you recover from UWS ?
If diagnosed with UWS, some patients can emerge from the vegetative state within weeks. Others may improve gradually or can stay in a state of impaired consciousness for years. In a worst case scenario, patients never regain consciousness
What is brainstem death ?
If the brain stem stops working, the person will never be able to be conscious or breathe without a machine (ventilator)
How do we test for brainstem death ?
Describe the neurological basis of consciousness ?
-Neurological regulation of sleep and wakefulness is distributed between two major anatomical structures the brainstem, harbouring reticular activating system (RAS), and the hypothalamus, harbouring suprachiasmatic nucleus (SCN).
- The brainstem areas are essential for consciousness especially the Reticular Activating System (RAS) which also known as the diffuse modulatory system
- It is not one single cortical (inside) area that is crucial for maintaining consciousness
- Cerebral cortex is also essential for many attributes of consciousness (memory, language, abstraction, attention, etc.)
What is the reticular activating system ?
The reticular formation is a collection of nuclei found throughout the midbrain and extend into the hindbrain (pons and medulla ) and teh spinal cord.
The reticular activating system (RAS), located in the anterior brainstem, is the central neurological regulatory centre for the sleep-wake cycle. It plays a critical role in regulating cortical alertness, wakefulness, and attention. The RAS is composed of four main components, all of which play key roles in wakefulness and arousal.
Describe the locus coeruleus of the RAS ?
Describe the raphe nuclei area of the RAS ?
The raphe nuclei contain serotonin containing cells. It directly communicates with the hypothalamic suprachiasmatic nucleus. Hence, it has a direct role in circadian rhythm regulation together with arousal and attention.
Describe the ventral tegmental area of the RAS ?
Describe the choilnergic nuclei of the RAS ?
The pedunculopontine and laterodorsal tegmental nuclei are collectively referred to as the pontomesencephalotegmental complex. This complex is located within the pons and the midbrain, and contains cholinergic neurones that project to areas including the thalamus and cortex. Their activation is responsible for the shift from slow waves sleep rhythms to higher frequency awake rhythms.
Describe the anterior and posterior hypothalamus in relation to consciousness and sleep ?
The activity of RAS and hence sleep-wake cycle is heavily regulated by nuclei present within the hypothalamus.
The suprachiasmatic nucleus (SCN) is situated directly above the optic chiasm. It receives input from the retina regarding light intensity. This retinal input makes is well-suited for its role as the major circadian clock in the human brain. In response to light changes, it generates circadian rhythms in rest and activity.
The lateral hypothalamus contains neurones secreting a peptide neurotransmitter called hypocretin (orexin). It is believed to innervate and excite the RAS helping to establish wakefulness and inhibit REM sleep.
The ventrolateral preoptic nucleus (VLPO)is located in the anterior hypothalamus and inhibits the main components of the RAS, hence promoting sleep. It is most active during sleep when it will release inhibitory neurotransmitters such as GABA to suppress RAS-induced wakefulness.
Endocrine Regulation
Melatonin is a hormone produced by the pineal gland in response to signals from the SCN. Hence, melatonin release is based on the circadian rhythm.
Melatonin release increases at night, a few hours before sleep, and peaks around midnight. Its levels then gradually decline until the morning when wakefulness is restored. The blue light (400 and 525 nm) emitted from screens is responsible for inhibiting melatonin release to a greater degree than other wavelengths. Consequently, a lengthy and late screen time may make it more difficult for people to fall asleep!
Summary of the RAS ?
RAS and sleep
Describe the sleep wake cycle ?
The sleep-wake cycle is a cyclical variation in one’s awareness, comprising of phases of wakefulness and sleep. This is largely influenced by changes in behaviour and physical activity as well as light and dark exposure, and is an example of a circadian rhythm. Circadian rhythms are important in regulating many physiological processes including hormone release e.g. cortisol.
What is REM ?
What is NREM ?
REM : Rapid eye movement
NREM: Non rapid eye movement
These are both two types of sleep
Describe REM (rapid eye movement) sleep ?
During REM sleep, the brain appears more active on an electroencephalogram (EEG) compared to alertness. Interestingly, during this sleep phase almost all muscles of the body are paralysed (REM atonia). The exceptions are respiratory muscles and extraocular muscles.
Sympathetic activity predominates during this phase of sleep, which in turn results in an increased respiratory and heart rate.
Additionally, during the REM phase, the human brain produces vivid images and events which we know as dreams.
Describe NREM ( non rapid eye movement) sleep ?
NREM sleep is characterised by slow, low-frequency EEG patterns. This phase of sleep is additionally divided into 4 stages according to the increasing synchronisation of neural activity and lower frequency of generated waves. In contrast to REM sleep, there is usually little or no rapid eye movement and muscles are not paralysed.
Additionally, parasympathetic activity prevails – resulting in lowered heart rate, respiration rate and renal function, and increased digestion.
This table summarizes the stages of sleep
Describe sleep cycling ?
Throughout the course of the night, a person will cycle through NREM and REM sleep. The average length of the first NREM-REM cycle is 70-100 minutes, whereas the later cycles are slightly longer-lasting – approximately 90 to 120 minutes.
A sleep episode begins with a period of NREM stage 1 sleep, progressing through stages 2, 3 and 4. Subsequently the person exits the NREM stage, reversing through the stages to enter the REM sleep state as demonstrated in Figure 3. This cycle repeats throughout the night.
Describe how the proportion of REM and NREM sleep changed throughout the night ?
As the night progresses, the proportion of REM sleep per cycle increases, whereas stage 2 begins to account for the majority of NREM sleep. Stages 3 and 4 may disappear altogether in later cycles.
Oscillations in an EEG are generated by the interaction between 3 types of neurons, what are they ?
- Thalamocortical (in thalamus)
-Reticular (in reticular nucleus)
-Corticothalamic (in cerebral cortex)
Disorder of sleep examples ?
Obstructive sleep apnoea: is a relatively common condition where the walls of the throat relax and narrow during sleep, interrupting normal breathing. It can cause temporary cessation of breathing
Enuresis (urinary incontinence) : bladder control
Epilepsy (neuronal seizures) can worsen your sleep
What are the short and long term consequences of sleep deprivation ?
What is the circadian rhythm ?
A circadian rhythm, or circadian cycle, is a natural, internal process that regulates the sleep–wake cycle and repeats roughly every 24 hours.
Glutamate receptors ?
GABA and diazepam ?
Describe glycine ?
- amino acid neurotransmitter
- inhibitory neurotransmitter which acts on motor neurons of the ventral horn of the spinal cord and braisntem.
- renshaw cells are inhibitory inter neurons found in the grey matter of the spinal cord. Renshaw cells utilise the neurotransmitter glycine as an inhibitory substance that synapses on the alpha motor neurons.
Describe catecholamines ?
Catecholamines:
- Dopamine
- Noradrenaline / Norepinephrine
- Adrenaline / Epinephrine
All the catecholamines are related and one turns into the other.
What enzyme breaks down norepinephrine ?
Norepinephrine is metabolised by the enzymes MAOs and COMT.
What is serotonin produced from ?
Tryptophan
Overview of the mental health exam ?
Appearance and behavior
Speech
Mood
Thought content
