Neuroanatomy Lectures PDF

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Summary

Lectures are given by Dr Kirsten McKenzie
Covered Neuroanatomy 1-4...

Description

Key Terms •

Dualism - the body is made up of matter, the mind is not (opposes monism).

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Monism - mind and body are both made of matter (opposes dualism), the mind is a product of the CNS.

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Experimental Ablation - cutting off parts of the brain to see behavioural differences.

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Emergent Properties - object as a whole has a complex system but the individual parts of it are simple.

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Plasticity - not fixed and can be changed.

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Nomenclature - anatomy/structure

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Sexual Dimorphism - two sexes of the same species have different characteristics beyond differences in sexual organs.

The Brain •

The brain is the centre of the nervous system in all animals.

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Descartes was the first to realise its importance - referred to the body as a machine being controlled by the brain. - believed in dualism of the mind and body. - believed the pineal gland controls body movement using fluid pressure.

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Galvani showed electrical stimulation causes muscle contractions in frogs - disproving the fluid theory.

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Flourens used experimental ablation to see which brain regions control which behaviours.

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Broca observed human brain injuries - looked at correlation between damaged area and impaired functions. - stroke victim showed that cerebral cortex on left hemisphere controls speech.

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The brain is an emergent property.

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Connections in the brain are plastic.

Nervous System •

Central Nervous System: - brain and spinal cord.

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Peripheral Nervous System - neurons going to the spinal cord. - contains Somatic Nervous System - controls voluntary movement and movement caused by environment - reflexes: moving away from hot object - Afferent nerves go towards CNS - Afferent = Away from the source - Efferent nerves go towards the PNS - contains Autonomic Nervous System - Autonomic = Automatic feelings - hunger, thirst, temperature etc - 2 types of efferent nerves - sympathetic nervous system = arousal - fight or flight response - parasympathetic = relaxation - rest and digest

Brain Nomenclature •

Brain is packaged under - 7 layers of skin - subcutaneous connective tissue - galea aponeurotica - loose areola tissue - pericranium - skull - meninges.

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Skull - made up of 8 cranial bones, 14 facial bones - cranial bones match with cerebral lobes - bones are connected by cranial fissures which develop after birth - bones cannot fuse before birth as head would not fit through birth canal and be no space for brain to grow - sinuses and fissures in the skull to allow neurons access to the brain.

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Meninges - dura mater, arachnoid membrane, subarachnoid space, pia mater - subarachnoid space filled with cerebrospinal fluid to stop brain collapsing (reduces weight) and removes waste (drains into spinal cord).

Lobes of the Brain 

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Frontal Lobe - The ‘Front’ Lobe - decision making - problem solving - inhibiting processes. Temporal Lobe - The ‘Time’ Lobe - primary auditory cortex - speech - auditory association. Parietal Lobe - The ‘Wall’ Lobe - somato-tactile processing - sensory integration - somatosensory association. Occipital Lobe - The ‘Back of Head’ Lobe - primary visual cortex - visual association. Cerebellum - The ‘Little Brain’ - not actually a lobe - coordination of voluntary movement.

Dividing The Brain •

Lobes are separated by fissures (deep cut)

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The longitudinal fissure divides the cerebral hemispheres.

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The lateral sulcus divides the temporal lobe and frontal lobe.

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The central sulcus divides the frontal lobe and the parietal lobe.

Commissures •

There is lateralisation of function in the brain - left hemisphere specialises in language - right hemisphere specialises in spatial processing and emotion - both hemispheres involved in most functions but not all.

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Commissural pathways connect regions of the brain - corpus callosum connects the two hemispheres - made up of white matter - bundles of myelin covered axons that link together - made up of genu (the anterior), trunk (centre), and splenium (posterior) - from genu, fibres run forward into frontal lobe - creates fork shape - from splenium, fibres run back into occipital lobe.

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Callosectomy given to patients with severe epilepsy to sever the corpus callosum - can no longer send info from one hemisphere to another - results in disconnection syndromes - Agraphia: cannot write with left hand, right hemisphere has no language access - Anomia: cannot name objects placed in left hand when blindfolded but can if placed in right hand - Unilateral Apraxia: can perform verbally instructed actions with right hand but not the left - Verbal anosmia: unable to name smell given to right nostril (smell input goes to ipsilateral hemisphere) but can use left hand to find the object that matches the smell - Anarchic Hand: non-dominant hand acts with mind of its own, both hands will receive instruction but dominant hand can no longer supress non-dominant hand - Spatial Decoupling: able to draw different shapes with each hand simultaneously

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Anterior Commissure - bundle of nerve fibres - key role in pain sensation (especially sharp pain) - sends auditory, visual, and olfactory (smell) info between temporal lobes of left and right hemisphere.

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Hippocampal Commissure - aka Commissure of Fornix - associated with memory - found above the thalamus.

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Habenular Commissure - In front of pineal gland - connects the habenular nuclei - dopamine and serotonin regulation.

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Posterior Commissure - aka Epithalamic Commissure - Controls bilateral pupillary light reflex (pupils react to light simultaneously)

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Association fibres: interconnect different fibres of cerebral cortex within a hemisphere

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Projection fibres: originate in white matter then end in grey matter or another white region.

Brain Tissue •

Grey Matter - aka substantia grisea (‘grey substance’) - thin layer around outside of brain - made up of nerve cell bodies - processing concludes in grey matter (starts in white and moves to grey) - cerebral cortex, thalamus, and hypothalamus are all grey matter - no myelin sheath so signals sent down neurons are slower.

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White Matter - very dense, 60% of brain volume - covered in substantia alba (‘white substance’) - made up of myelin covered axons - faster signals.

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Cerebrospinal fluid - retains the brain shape - drains waste into spinal cord - keeps brain floating and safe from damage.

Grey Matter Regions •

Cerebral Cortex - largest area of grey matter - most superficial layer of cerebral hemisphere

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Thalamus (‘inner room’) - involved in sensory and motor signals - regulated consciousness and sleep.

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Hypothalamus (‘below inner room’) - temperature regulation - hunger/thirst control

- monitors sleep - controls hormone release (for mood and libido) •

Basal Ganglia (‘base swelling’) - aka Basal Nuclei - controls voluntary movement, cognitive processing, learning and emotion - associated with Parkinson’s disease.

Brain Development •

Neural development starts at fertilisation - CNS starts to develop at day 18 - starts as a neural tube.

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3 primary brain vesicles: - prosencephalon (‘before brain’) - Mesencephalon (‘middle brain’) - Rhombencephalon (‘rhombus brain’)

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Primary vesicles divide to form 5 secondary vesicles - Prosencephalon becomes telencephalon and diencephalon - Mesencephalon doesn’t divide - Rhombencephalon becomes metencephalon and myelencephalon.

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At 14 weeks, brain resembles a fully formed shape.

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30 weeks, gyri (sausage) and sulci (dips between the gyri) form

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3 months, embryo displays reflexes, hormones determine the sex.

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In 1st year, brain will triple in size, development will then slow down.

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At 25 years old, brain stops developing.

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At 35 years old, brain starts to deteriorate but motor skills peak in 40s.

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Telencephalon - controls voluntary movement - cognitive and emotional responses - becomes amygdala and hippocampus.

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Diencephalon - becomes thalamus and hypothalamus - sensory and motor relay sensation (tactile) - temp regulation, hunger, thirst, sleep, hormone release.

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Mesencephalon - becomes tegmentum - homeostatic and reflex pathways - prevents unwanted movements.

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Metencephalon - becomes cerebellum and pons - voluntary movement, respiration, swallowing, sleep, and taste.

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Myelencephalon - becomes medulla - breathing, heart rate, blood pressure, sneezing, and vomiting....