Case 10 - Yaffas Part 2 Flashcards
what are the two main forms of cholinesterase
acetylcholinesterase (AChE)
butyrylcholinesterase (BuChE)
what is AChE
mainly membrane bound
relatively specific for acetylcholine
responsible for rapid acetylcholine hydrolysis at cholinergic synapses
what is BuChE
relatively non-selective
occurs in plasma and many tissues
what is the clinical use of anti cholinesterase drugs
To reverse the action of non-depolarising neuromuscular-blocking drugs at the end of an operation (neostigmine).
Atropine/Glycopyrrolate must be given to limit parasympathomimetic effects.
To treat myasthenia gravis (neostigmine).
what are the autonomic side effects of cholinesterase inhibitors
bradycardia
hypotension
bronchocontriction
what are the muscular side effects
Muscle fasciculation
Twitch tension
Depolarisation block
what is the mechanism of action of neostigmine
blocks acetylcholinesterase
increases Ach in the neuromuscular junction (both nicotinic and muscarinic)
increases muscular junction
acts to reverse effects of muscle relaxants
what are examples of muscarinic receptor antagonists
atropine and glycopyrrolate
what do muscarinic receptor anatagonists do
antagonise the muscarinic receptor and thus inhibit cholinergic transmission
what can atropine do that glycopyrolate cannot
atropine can cross the blood brain barrier whereas glycopryrolate cannot
what are muscarinic receptor antagonists used to do
limit parasympathethomimetic effects caused by neostigmine
it prevents neostigmine muscarinic effect such as bradycardia
what is mannitol
an osmotic diuretic
it is inert in humans but it occurs naturally
the drug is used to treat raised intracranial pressure
what is the mechanism of action of mannitol
These are pharmacologically inert substances that are filtered in the glomerulus but not reabsorbed by the nephron.
They cause diuresis because they increase the solute content of the fluid in the proximal tubule and collecting tubules.
This draws fluid from the body into the proximal tubule, thus decreasing the volume of fluid inside the body.
The result of this is that less water is reabsorbed and also less sodium.
This leads to a decrease in extracellular fluid volume.
Also, they increase the plasma osmolality.
This increases the flow of water from tissues (brain and CSF included) into the interstitial fluid and plasma.
This reduces the intracranial pressure.
what is sleep
a state of physiological reversible unconsciousness
what is the change from sleep to wakefulness mediated by
the reticular activating mechanism
what is the change from wakefulness to sleep affected by
it is an active process affected by an arousal inhibitory mechanism based on a partial blockade of the thalamus and upper brainstem
what is the cognitive change between sleep and wakefulness accompanied by
changes in the autonomic system, the cerebral blood flow and cerebral metabolism
what is instant awareness
the ability to integrate all sensory information from the external environment and the internal environment of the body
what is awareness a function of
the thalami-cortical network in the cerebral hemispheres, which forms the final path of the sleep/wake mechanism
what is awareness an essential component of
total consciousness (defined as continuous awareness of the external and internal environment, both past and present, together with the emotions arising from it)
what is the circadian clock
Human sleep occurs with circadian periodicity. The biological clock detects decreases in light levels as night approaches.
Ganglion cells containing melanopsin are depolarized by light.
Projections run via axons running the retino-hypothalamic tract, which projects to the suprachiasmatic nucleus (SCN) of the anterior hypothalamus, the site of the circadian control of homeostatic functions.
what is the activation of the SCN
Activation evokes responses in neurons whose axons first synapse in the paraventricular nucleus (PVN) of the hypothalamus.
These neurons descend to the preganglionic sympathetic neurons in the intermediolateral zone (IML) in the lateral horns of the thoracic spinal cord.
These preganglionic neurons modulate neurons in the superior cervical ganglia (SCG) whose postganglionic axons project to the pineal gland.
This causes secretion of melatonin into the bloodstream.
when is melatonin increased
as the light in the environment decreases. in the elderly, the pineal gland produces less melatonin
where is melatonin found
the pineal gland
what is the ascending arousal system
increases arousal and mediates wakefulness
flows from the brainstem through the thalamus, hypothalamus and basal forebrain to the cerebral cortex
what is the first component of the ascending arousal system
Through the thalamus to the cerebral cortex.
These projections activate relay neurons and reticular nuclei (in the thalamus) essential for thalamocortical transmission.
Two cholinergic structures (PPT/LDT) in the brainstem and basal forebrainserve as the origin of these projections.
PPT/LDT neurons are most active during wakefulness and rapid eye movement (REM) sleep and discharge more slowly during non-REM (NREM) sleep, a period when cortical activity is reduced.
Transmission to the reticular nucleus promotes a state of excitability and wakefulness (“reticular activating system”).
what do projection to the thalamus use
acetylcholine
what is the second component of the ascending arousal system
Through the lateral hypothalamus (LH) and basal forebrain (BF) to the cerebral cortex.
It comprises a number of monoaminergic cell populations, including:
Noradrenergic neurons of the locus coeruleus (LC)
Serotoninergic (5-HT) dorsal and median raphe nuclei
Dopaminergic neurons of the ventral periaqueductal grey matter
Histaminergic neurons from TMN
features of neurones in the monoaminergic systems
have broad action potentials, discharging most rapidly during wakefulness, slowing during NREM sleep and showing little activity during REM sleep
what is orexin
a neurotransmitter that regulates arousal, wakefulness and appetite
orexin nucleus activity during wakefulness
strongly excite various brain nuclei with important roles in wakefulness including the dopamine, norepinephrine, histamine and acetylcholine system.
also helps stabilise wakefulness and sleep
what happens to orexin activity during sleep
the activity is reduced
what are the stages of sleep
consist of non-REM stages that vary clinically with an REM stage during which the EEG cycles between a desynchronised state and a synchronised state
how many sleep cycles are there in an 8hr period of sleep
4-6 sleep cycles
how much of the sleep cycle is spent in non-REM sleep
80% - amount decreases with each cycle
how much of the sleep cycle is spent in REM sleep
20% - and increased with each cycle
what is non-REM sleep induced by
“non-REM-on” GABA neurons in the hypothalamus.
Serotonin from the raphe nuclei.
what has decreased activity during non-REM sleep
brainstem noradrenergic neurones
what is non-REM sleep characterised by
progressively synchronised EEG
four stages of non-REM sleep
what happens to skeletal muscles during non-REM sleep
skeletal muscles relax but maintain their tone
features of parasympathetic nervous system during non-REM sleep
is active and promotes gastric motility and a decease in heart rate and BP
what is REM sleep characterised by
sudden conversion from a synchronized to a desynchronized EEG, resembling that of the awake state combined with a loss of muscle tone (atonia), which results in an active nervous system in an inactive body.
when does REM sleep commence
only after non-REM sleep progresses through stages 1-4 and back to state 2, a cycle that lasts about 90. mins
what initiates REM sleep
brainstem cholinergic neurones in the ascending arousal system act on ‘REM-on’ cells
what is activated during REM sleep
inhibitory medullary reticulospinal neurones, causing skeletal muscles to become flaccid and muscle stretch reflexes to be absent
what are the only muscles to remain active
the ocular, respiration and middle ear muscles
are all sensory systems inhibited during REM sleep
yes
what is there an increase of during REM sleep
increase in BP, metabolism, and blood flow to the brain
what are penile and clitorial erections features of
REM sleep
when do most dreams occur
during REM sleep, and the visual images precieved during dreaming are associated with PGO waves int he EEG
what initiates a transition from REM sleep back to non-REM sleep
noradrenergic and serotenergic neurones act as ‘REM-off’ cells initiating the transition
what does the amount of daily REM sleep decrease with
age
what type of sleep do we need to survive
need non-REM sleep in order to survive
what is the theory of restoration
rest and recover
prepare to be awake again
no exactly certain what is restored - cortex can achieve some form of essential rest during non-REM phases
what is the theory of adaptions
less obvious - sleep to hide from predators - out most vulnerable state
adaption for conserving energy
what is consciousness defined as
an alert cognitive state in which you are aware continually aware of the external and internal environment, both past and present, together with the emotions arising fro it
it is also the maitenance of an alert state
what does someone have to have in order to be fully conscious
have an intact ascending reticular activating system (awake) in the brainstem and a functioning cerebral cortex (aware)
what is a coma
profound state of unconsciousness that is associated with depressed cerebral activity from which the individual cannot be aorused
what is a vegetative state
is a clinical condition, in which the patient is unaware of self or surroundings, breathes spontaneously and has stable circulation and shows patterns of eye closure and opening that may simulate sleep.
However, there is no intelligent communication coming from the patient.
A persistent vegetative state is irreversible.
A person is said to be in a persistent vegetative state if they are still in one 12 months after a head injury.
what is a generalised seizure
involves the entire cerebral cortex, of both hemispheres
what is a partial seizure
involves only a limited area of the cortex, but it can spreaf
what happens in both types of seizures
the neurones within the affected areas fire with a synchrony that never occurs during normal behaviour
this is why seizures are usually accompanied by very large EEG pattens
what Is the condition known as when a person experienced repeated seizures
epilepsy
what are potent convulsants
drugs that block GABA
what drugs are potent convulsants
drugs that block GABA receptors
how do anticonvulsants work
Prolonging the inhibitory actions of GABA (e.g. barbiturates, benzodiazepines).
Decrease the tendency for certain neurons to fire high-frequency action potentials (e.g. phenytoin, carbamazepine).
what do the behavioural features of a seizure depend on
the neurones involved and the patterns of their activity
how is behavioural disrupted during generalised seizures
virtually all corticalneurones participate, so behaviour is completely disrupted for many mintues
what is the tonic-clonic seizure
consciousness is lost, while all muscle groups may be driven by tonic (ongoing) activity or by clonic (rhythmic) patterns, or by both in sequence
what can partial seizures be
instructive
what happens if partial seizures begin in a small area of the motor cortex
they can cause clonic movement of part of a limb
what can happen if seizures begin in a sensory area,
they can trigger an abnormal sensation or aura such as an odd smell or sparkling lights
what are the early signs of elevated ICP
drowsiness and a diminished Level of consciousness
what are late signs of raised ICP
coma and unilateral pupillary changes
what is emergent treatment of elevated ICP most quickly achieved by
intubation and hyperventilation which causes vasoconstriction and reduces cerebral blood volume
what is sometimes used for refractory elevations of ICP, although these have a significant side effect and not been proven to improve outcome
high dose barbiturates, decompressive hemicraniacetomy or hypothermia
what are the two principles of oedema
Vasogenic oedema refers to the influx of fluid and solutes into the brain through an incompetent blood-brain barrier (BBB).
Cytotoxic oedema refers to cellular swelling.
what does cranial oedema that is clinically significant usually represent
a combination of vasogenic and cellular components
what is the treatment for cranial oedema
elevate head to 30 degrees
intubate and hyperventilate - reduce cerebral blood flow due to vasoconstriction
IV mannitol - osmotic diuretic
ventricular damage
what is a craniotomy
this is a surgical removal of part of the cranium, performed to expose brain and meninges for inspection or biopsy or to relieve excessive intracrnaial pressure
what is the procedure of a craniotomy
The hair is shaved, the scalp is cleaned with iodine solution, and an incision is then made to expose the skull.
Burr holes are drilled through the skull at several locations.
The burr holes are then joined together.
The bone flap is removed, exposing the dura.
The dura is then carefully opened and folded back.
what is the blood supply to the scalp via
five pairs of arteries, two from the internal carotid and three from the external carotid
whast are the two arteries from the internal carotid
Supratrochlear arteryto the midline forehead. The supratrochlear artery is a branch of the ophthalmic branch of the internal carotid artery.
Supraorbital arteryto the lateral forehead and scalp as far up as the vertex. The supraorbital artery is a branch of the ophthalmic branch of the ICA.
what are the 3 arteries of the external carotid
Superficial temporal arterygives off frontal and parietal branches to supply much of the scalp.
Occipital arterywhich runs posteriorly to supply much of the posterior aspect of the scalp.
Posterior auricular artery ascends behind the auricle to supply the scalp above and behind the auricle.
how can a small scalp wound bleed profusely
the walls of the blood vessels are firmly attached to the fibrous tissue of the supericial fascial layer, hence cut ends of the vessels here do not readily retract
what is a compound fracture
when the skin is also broken
types of fracture table
what is a neuropsycholoigcal assessment (simple procedure)
Asking whether the patient is able to move and react to physical stimuli.
If so, the next question is whether the patient can respond in a meaningful way to questions and commands.
If so, the patient is asked for name, current location, and current day and time.
A patient who can answer all of these questions is said to be “oriented times three” (sometimes denoted “Ox3” on a medical chart), and is usually considered fully conscious.
what is a complex neurological examination
A formal neurological examination runs through a precisely delineated series of tests, beginning with tests for basic sensorimotor reflexes, and culminating with tests for sophisticated use of language.
what is cognition associated with
intellectual functioning
perception
memory
mood
speech and language
what are the type types of assessment
descriptive:
- type and severity of the problem
predictive:
- to explain causes and consruwneces pf defect
assessment
Intellectual Functioning
Higher executive functioning (WAIS-R).
Reduced accuracy / or speed in time pressure processing.
Reduced concentration span.
Perception
Visuo-perceptual (object recognition)
Audition (sound recognition, localisation)
Hallucinations
Altered olfactory, kinaesthetic or gustatory experiences
Memory
Impaired recent memory
Frequency estimation
Sequencing
Delayed response task
Mood
Lability (swings)
Aggression
Depression
Anxiety
Speech and Language
Lability (swings)
Aggression
Depression
Anxiety
Behaviour
Sexual disinhibition
Aggression
Uncharacteristic responses (described as personality change)
what is the rehabilitation plan
what does right temporal lobe damage and part removal do
memory/hearing/language understanding / info processing
preoperative oedema consequences
additional damage to residual tissue
what is dense hemioarwsus
on going disability / consequences
what is esteem support
whereby other peppleincrease ones own self esteem
what is informational support
whereby other people are available to offer advice
what is compqnioshup
which involves support though activites
what is instrumental support
involves physical help
what does the stress buffering hypothesis suggest
that social support helps individuals to cope with stress
