Sem2 Week 2
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How many neurons does the human brain have?
Approximately 90 billion (90 × 10⁹) neurons
What percentage of the body’s energy does the brain consume?
20% despite being only ~2% of body mass
How much power does the brain run on?
About 20 watts
What is the role of the thalamus?
It interconnects different areas of the cortex
What structures are found beneath the cortex?
The midbrain; cerebellum; corpus collosum, and other subcortical structures
What is grey matter?
Brain tissue containing nerve cell bodies (somas) appears pink in living tissue
What is white matter?
Brain tissue containing connections (axons) between nerve cells
What functions are associated with the left hemisphere?
Analytical tasks; usually speech and language (Broca’s and Wernicke’s areas)
What functions are associated with the right hemisphere?
Retrieval and maintenance of information (e.g. map reading)
What connects the two hemispheres?
The corpus callosum
What are the four main lobes of the cortex?
Frontal; temporal; parietal; and occipital
How thick is the cortex?
Between 2 and 4 mm
How many distinct areas did Brodmann map?
52 areas based on cytoarchitecture
What are the main functions of the frontal cortex?
Executive functions (guiding and planning behaviour; switching behaviours); social cognition; and possibly consciousness
What sensory functions does the temporal lobe handle?
Auditory processing and olfaction
What does the parietal lobe (somatosensory cortex) process?
Touch temperature pain proprioceptive information, and some executive function
What is the motor homunculus?
A topographic map of the body on the motor cortex where cortical area is proportional to motor complexity not body size
What is the hippocampus’s main function?
Episodic memory; acts as a buffer for long-term storage. Damage prevents new memories forming (anterograde amnesia)
Who was Phineas Gage?
A railroad worker whose left frontal lobe was pierced by a tamping iron in 1848; survived 12 years with personality changes then recovery
How many cortical neurons does the human cortex have compared to elephants?
Human: 16 billion; Elephant: 5.6 billion — humans have higher neuron density despite elephants having more total neurons
What is the connectome?
A map of all structural connections between brain regions
What methods are used today to study brain function non-invasively?
PET/MRI for anatomy, fMRI and EEG for activity
What is an action potential (spike)?
An all-or-none electrical event in a neuron — either fires fully or not at all
What are dendrites?
Branching structures that collect synaptic inputs to the neuron