N Lecture 2 - Gross Human Neuroanatomy, Comparative Anatomy

The Brain

– large clump of 86 billion neurons 

• Responsible for complex behaviours, thought, perception and emotion

• 2 hemispheres

Ventricles

(Spaces between brain)

• Cavities filled with cerebrospinal fluid (CSF)

• Sewerage system of CNS 

  • Blockages causes hydrocephalus (inflates ventricles, squashing brain)

Major Subdivision of the Brain - Brainstem

• Controls life supporting functions 

• Damage to brain stem causes loss of consciousness, coma, death - increased pressure inside the head can cause this

Major Subdivision of the Brain - Cerebellum (“Small Brain”) 

• Control of precision movements - fine accurate skills (include learned ones)

• 70% of neurons in brain in small brain for humans 

• Receiving visual input and other sensory input and learnt what muscles movements need to be sent out  

Major Subdivision of the Brain - Thalamus & Hypothalamus (Diencephalon)

• Thalamus is sensory relay to cortex – auditory, visual etc 

  • Gateway of sensory info coming into brain and allows it to participate in selective attention 

  • You can control what sensory input you are paying attention to – can regulate it 

• Hypothalamus is involved in hormonal regulation and motivational control (feeding and sex)

  • Connected to pituitary 

  • Self releases a lot of hormones 

Major Subdivision of the Brain - Limbic System

• Control of emotion and memory 

  • Fornix

  • Thalamus 

  • Hippocampus 

  • Amydgala 

  • Mammillary bodies

  • Olfactory bulb 

  • Cingulate Cortex

Major Subdivision of the Brain - Basal Ganglia 

• Action and thought 

  • Thalamus (left and right) 

  • Caudate (left and right) 

  • Putamen 

  • Globus Pallidus 

• Parkinsons and Huntingtons affect the basal ganglia 

Major Subdivision of the Brain - Neocortex

• Convoluted sheet on top of the brain 

• 4 lobes of neocortex 

  • Frontal Lobes

  • Parietal Lobes

  • Temporal Lobes

  • Occipital Lobes

Neocortex — Frontal Lobes (Red)

• Planning & executive functions (inhibitions, self control – inhibition, ability to plan for the future, memory) 

• Primary motor cortex - neurons send axons to spinal cord to send signals to muscles to move – one of main output centre in brain - voluntary movements 

Neocortex — Parietal Lobes (Blue) 

• Perception and understanding of space around us – represents space for action 

• Somatosensory cortex - when neurons are stimulated/activated you will feel touch 

  

Neocortex — Temporal Lobes (Green)

• Memory and language 

• Has the hippocampus 

• Primary auditory cortex - auditory information arrives from the thalamus here 

• Taste and smell

Neocortex — Occipital Lobes (Yellow)

• Vision - recognise things, people, understand how the vision experience is organised

Corpus Callosum 

Connecting 2 hemispheres

Comparative Neuroanatomy 

• Nervous system almost a defining feature of animals 

  • Roundworm - 302 neurons 

  • Starfish - 500 neurons 

  • Jellyfish - 5,000 to 10,000 neurons

• Nervous system has more complex organisation in insects 

  • Clusters of neurons (ganglia) forming cord or “brain” 

  • Some specialisation of neurons (e.g. motor vs sensory)

• Vertebrates have separation between PNS and CNS 

  • Among vertebrates – large diff in relative size of diff regions of brain – reflecting complexity of behaviour 

  • Large increase in size of forebrain across vertebrates 

  • Appearance & enlargement of neocortex in mammals