Session 8 Flashcards
(37 cards)
Where do the majority of the inputs to and outputs from the cortex come from?
Inputs - Thalamus (then from other parts of the cortex)
Outputs - from pyramidal cells
What are the functions of the frontal lobes?
Motor (think precentral gyrus), expression of speech (usually left hemisphere), behavioural regulation/judgement, cognition, eye movements, continence
What are the functions of the parietal lobes?
Sensory (think postcentral gyrus), comprehension of speech (usually left hemisphere), body image (usually right), awareness of external environment (attention - also think neglect of one half of the world), calculation and writing, visual pathways project through white matter
What are the functions of the temporal lobes?
Hearing, olfaction, memory, emotion, visual pathways project through white matter
What is the commonest dominant cerebral hemisphere?
Left (95%)
Where is Broca’s area, what is it’s function and what happens when it doesn’t function?
Inferior lateral frontal lobe (near precentral gyrus)
Production of speech
Broca’s aphasia - understand but can’t articulate
Where is Wernicke’s area, what is it’s function and what happens when it doesn’t function?
Superior temporal lobe
Interpretation of speech, near border of parietal lobe
Wernicke’s aphasia - speech is effortless but meaning is impaired
What connects Broca’s and Wernicke’s areas?
Arcuate fasciculus
What are the different classifications of memory and where are the broadly stored?
Declarative - explicit, facts. Stored in cerebral cortex.
Nondeclarative - implicit, motor skills (eg guitar playing) and emotions. Stored in cerebellum.
What can determine whether a memory is short term or long term?
Emotional content, rehearsal, association
What structure helps to consolidate declarative memories?
Hippocampus
non-declarative is cerebellum
What is the basic molecular and cellular mechanism of memory?
Neuroplasticity - repeated activation of a post synaptic neurone leads to more receptors, more neurotransmitters and more branches of the presynaptic neurone.
What is required for consciousness?
Cerebral cortex and reticular formation
What is the reticular formation and what are its 2 major inputs?
A population of specialised interneurones in the brainstem. It forms the reticular activating sysyem forming a large part of arousal.
Sensory system and cortex
What are the ouputs from the reticular formation?
Basal forebrain nuclei, hypothalamus
Why do anti-muscarinics and anti-histamines cause drowsiness?
Transmission from the reticular formation to the cortex via the basal forebrain nuclei requires acetylcholine
Transmission from the reticular formation to the cortex via the hypothalamus requires histamine
How is consciousness assessed clinically?
Glasgow coma scale and electroencephalogram (EEG) Eye opening (/4) - spontaneous, to speech, to pain, nil Motor response (/6) - obey, localises to pain, withdraws from pain, abnormal flexion, extensor response, nil Verbal response (/5) - orientated, confused, inappropriate words, incomprehensible sounds, nil
How do neurones in the brain tend to fire when deprived of sensory input?
Synchronously
Describe the typical sleep cycles during a night
Pass through around 6 cycles of sleep progressing from an awake state down through to stage 4 then rapidly up to REM sleep.
Briefly describe the neural mechanism of sleep
Inhibition of the positive feedback loop between the cortex and reticular formation, which is assisted by the removal of sensory inputs
What happens during REM sleep?
It is initiated by neurones in the pons. EEG activity is similar as during arousal but the person is difficult to rouse due to strong thalamic inhibition. Eye movements and some cranial nerve funcntions are preserved. Autonomic effects are seen (eg erections)
What are the theoretical functions of sleep?
Energy conservation, body repair, memory consolidation
What are the 3 routes microorganisms can enter the CNS?
Direct spread - e.g.middle ear infection, basillar skull fracture
Blood borne - sepsis, infective endocarditis
Iatrogenic - VP shunt, surgery, lumbar puncture
What are the commonest causative organisms for meningitis in different age groups?
Neonates - escherichia coli, listeria monocytogenes
2 to 5 years - haemophilus influenzae
5 to 30 years - neisseria meningitidis
Over 30 years - streptococcus pneumoniae
