CASE 10 - temporal lobe, head trauma, anaesthesia etc Flashcards
where is the temporal lobe?
- middle cranial fossa, next to the temporal region/bone
- lies beneath the lateral fissure
what gyri are located on the lateral surface of the temporal lobe?
superior (area 22), middle (area 21) and inferior (area 20) temporal gyri
what gyri are located on the inferior surface of the temporal lobe?
inferior temporal gyrus and occipitotemporal (fusiform) gyrus
what sulci does the temporal lobe have on its lateral and inferior surfaces?
lateral surface: superior and inferior temporal sulci
inferior surface: collateral sulcus, midfusiform sulcus
what separates the superior and middle temproal gyri?
superior temporal sulcus
what separates the middle and inferior temporal gyri?
inferior temproal sulcus
where is the primary auditory area (A1)?
Brodmann area 41 — superior temporal gyrus
what area is the secondary auditory area (A2) in?
Brodmann area 42
where is the auditory association area?
brodmann area 22 (lateral to primary auditory area)
where is wernicke’s area?
posterior part of brodmann area 22 - superior temporal gyrus of dominant hemisphere
what mark the location of the primary auditory cortex on the superior surface of the superior temporal gyrus?
transverse temporal gyri (Heschl’s convolutions)
transverse temproal gyri (of Heschl) = found in the area of the primary auditory cortex buried within the ______ sulcus, occupying Brodmann areas ___ and _____
- lateral sulcus
- 41 and 42
where does the primary auditory cortex receive auditory information from?
medial geniculate nucleus of the thalamus
what is the auditory association area responsible for?
interpretation of auditory information and which, in the left hemisphere, constitutes Wernicke’s area (comprehension of the written and spoken language)
what does the temporal lobe work with in the formation of conscious memories?
amygdala (medial temproal lobe) and hippocampus (temporal lobe)
blood supply of the temporal lobe?
lateral surface supplied mainly by branches of the MCA
inferior surface supplied mainly by branches of PCA
which temporal lobe is typically dominant in most people and is associated with understanding language, learning, memorising, forming speech and remembering verbal information?
left
what is the non-dominant temporal lobe commonly associated with?
learning and memorising non-visual information (eg. drawings and music), recognising information, and determining facial expressions
how does blood reach the brain?
- anterior circulation = ICA + common carotid
- posterior circulation = vertebral arteries and subclavian artery
what vessel, if occluded, would affect both Broca’s and Wernicke’s area?
middle cerebral artery
what artery supplies blood to the occipital lobe?
posterior cerebral
what is the largest branch of the ICA?
MCA
what artery runs in midline on ventral surface of pons?
basilar artery
The scalp receives a rich arterial supply via the ________ and the _____________ (a branch of the internal carotid).There are three branches of the former involved:
- _________– supplies the frontal and temporal regions
- _________– supplies the area superiorly and posteriorly to the
auricle.
- __________– supplies the back of the scalp
Anteriorly and superiorly, the scalp receives additional supply from two branches of the ____________ – the ________ and _________ arteries. These vessels accompany the ___________ and ____________ nerves respectively.
The scalp receives a rich arterial supply via the external carotid artery and the ophthalmic artery (a branch of the internal carotid).There are three branches of the external carotid artery involved:
- Superficial temporal– supplies the frontal and temporal regions
- Posterior auricular– supplies the area superiorly and posteriorly to the auricle.
- Occipital– supplies the back of the scalp
Anteriorly and superiorly, the scalp receives additional supply from two branches of the ophthalmic artery – the supraorbital and supratrochlear arteries. These vessels accompany the supraorbital and supratrochlear nerves respectively.
photoreceptors absorb light using what?
11-cis retinaldehyde bound to opsin protein
what keeps opsin in the inactive state?
11-cis retinal
what is the G protein in photoreceptors?
transducin
what do photoreceptors respond to light with?
graded hyperpolarisation
what is the signal photoreceptors transmit in light?
reduction in Glu in response to absoprtion of light (lots of Glu released in dark as neurons release Glu when depolarised)
what provide an inhibitory link between bipolar cells and RGCs?
amacrine cells
axons from what layer project to the brain?
ganglion cell layer
what layer in the retina contains the cell bodies of rod cells?
outer nuclear layer
what layer in the retina contains the cell bodies of bipolar cells?
inner nuclear layer
what layer contains synapses between bipolar and amacrine cells?
inner plexiform layer
what layer contains synapses between photoreceptors (rod cells) and bipolar cells?
outer plexiform layer
is onset of anaesthesia faster with inhalation or iv?
iv
what is commonly used for induction of general anaesthesia?
propofol
when may inhalation be used over iv for induction?
where iv access is difficulty to obtain, where difficulty maintaining the airway is anticipated, or due to patient preference (eg. children)
maintenance of general anaesthesia is achieved by allowing the patient to breathe a carefully controlled mixture of what? how can it also be achieved?
oxygen, nitrous oxide and volatiles anaesthetic agent (isoflurane)
- can also be achieved by having a carefully controlled continuous infusion propofol through an intravenous catheter
what is the natural neurotransmitter at the NMJ which causes muscular contraction when it is released from nerve endings ?
ACh
muscle relaxants work by preventing…..
ACh from attaching to its receptor
since muscle relaxants paralyse the muscles of the larynx, how is the airway protected?
endotracheal tube
the effects of muscle relaxants are commonly reversed at the termination of a surgery by what type of drugs?
acetylcholinesterase drugs
in terms of airways, what is lost with the loss of consciousness?
- protective airway reflexes (eg. coughing)
- airway patency
- regular pattern due to the effect of of anaesthetics, opioids or muscle relaxants
what 2 things are used to reverse any muscle relaxants?
neostigmine and glycopyrrolate
what is monitored and assessed in reversal of anaesthesia?
oxygenation, pain control, fluid balance, post operative nausea and vomiting (PONV), cardiovascular stability, conscious level, urine output
- late management : wound infection, DVT, chest infection, surgical problems
what are some adverse effects of anaesthesia?
- PONV
- CV depression
- arrhythmogenesis
- hypotension : vasodilation
- loss of airway tone : airway obstruction
- malignant hyperthermia (uncontrolled temp —> if untreated, all the ATP stores are burned —> rhabdomyolysis, renal failure and cardiac arrest
- bronchial muscle relaxation and impaired cough reflex
- agitation and confusion (esp elderly)
- nephrotoxicity : RBF, GFR, UOP…. vs fluride induced nephrotoxicity
- hepatotoxicity : halothane hepatitis
- an iv anaesthetic for rapid induction = _______
- an inhalation anaesthetic to maintain anaesthesia during surgery = _______
- a perioperatie opiod analgesic = _________
- a muscarinic antagonist to prevent or treat bradycardia or to reduce bronchial and salivary secretions = _______/________
- anticholinesterase agent to reverse the neuromuscular blockade = ________
- propofol
- isoflurane
- fentanyl
- atropine/glycopyrrolate
- neostigmine
what are inhalation anaesthetics soluble in?
lipid — readily cross alveolar membranes
what are the main factors that determine the speed of induction and recovery? (properties of inhalation anaesthetics)
properties of the anaesthetic:
> blood:gas partition coefficient (solubility in blood) = speed of induction/recovery
oil:gas partition coefficient (solubility in fat) = potency
physiological factors:
> alveolar ventilation rate
cardiac output
anaesthetic potency is expressed as the what?
minimal alveolar concentration (MAC)
what is the MAC?
minimal alveolar conc
= the conc of vapour in the lungs that is needed to prevent movement (motor response) in 50% of patients in response to surgical (pain-incision) stimulus
what does the potency of a drug increase with?
increasing lipid solubility
link between lipid solubility and MAC?
the higher the lipid solubility, the lower the MAC
why does propofol have rapid recovery with a small hangover effect?
very rapidly metabolised to inactive metabolites
MOA of propofol
positive modulation of GABA through GABA-A receptor — cause an increased influx of Cl- ions into the post synaptic neuron
where do anaesthetics mainly work?
extrasynaptic GABA-A receptors
what type of receptors are GABA-A receptors?
ionotropic ligand-gated ion channels
what are common SEs of propofol?
SEs are less frequent for propofol than other iv anaesthetic agents. SEs include:
- hypotension and bradycardia
- resp depression
- pain with injection
- involuntary movement and adrenocortical suppression
- nausea and vomiting
what is the msot widely y used inhalation inducing agent and used for maintenance of general anaesthesia?
isoflurane
what is isoflurane always administered with?
air/pure O2 and nitric oxide
MOA of isoflurane
likely binds to GABA, NMDA (glutamates) and glycine receptors. NOT UNDERSTOOD
SEs of isoflurane
relatively free from SEs. major ones inc hypotension, coronary vasodilation (exacerbate cardiac ischaemia in patient with coronary disease), resp suppression
name a potent narcotic analgesic
fentanyl