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What is arabidopsis thaliana?

A plant that is a very distant relative of ours - last common ancestor maybe 1.5 billion years ago.
A complex organism with 27,000 genes but no nervous system.
First to have its entire genome sequenced.
Fundamental difference between us and plants is the presence of a nervous system.


What is Corynactis californica?

A simple, sessile invertebrate animal.
Very little tissue/organ/system specialisation.
Has a "nervous system" comprising a network of nerve cells --> no separate tissue.


Why have a nervous system?

1. control the milieu interieur - homeostatic regulation
2. control movement
3. reveal the universe: conscious awareness


Historically, what organ was thought to have an important role in the nervous system?

The heart - "know it by heart"
Some people even believed it had the only role


On what was the Ancient Egyptian model of life based?

To the ancient Egyptians, the health of the body and mind, like the variability of the land, concerned the flow of fluids. Problems occur when there is too much or too little flow.
Therefore probably placed great emphasis on the great vessels.


Who was the person who really 'got us on the right track' about how we should think about 'the marrow of the head'?

Hippocrates (born 460 BCE): "from nothing else but the brain comes joys, delights, laughter and sports, and sorrows, griefs, despondency and lamentations..."

Insightful and important contribution.


Why not the brain as the seat of reason and experience?

Aristotle held a cardio-centric view of mind, contrary to Hippocrates and the growing acceptance of the brain as the seat of the mind.

Believed this because:
- the heart moves, the brain just sits there
- simple animals move and react, but have no brain
- warmth (=life) emanates from the body's core (the heart)
- all known civilisations held the heart to be the centre of conscious being

- argument against smarter animals having bigger brains: it was a cooling device for the heart which is generating more heat

- our language still contains lots of references to the heart as having a role in the nervous system


Who was Galen?

- a roman surgeon

- admired Hippocrates, accepted the brain as the seat of the intellect, and also accepted the classical explanation of the humors of the body (because of fluid filled ventricles)
- much was learnt about the brain from treating injured gladiators. Unlike the Ancient Greeks, the Romans permitted themselves direct observation and investigation, including dissection of corpses (autopsy) and animals
- the Renaissance re-instated the importance of detailed observation and questioning of doctrine, but the primacy of the humors as mechanistic explanation prevailed

- but thought that big brain does not = intelligence --> donkeys


What are the main divisions of the nervous system?

- we tend to think only of the brain when we think of the NS, but there is quite a bit more
- the nervous system (of vertebrates) comprises a central division and a peripheral division
- the Central division is the brain and the spinal cord
- the peripheral nervous system is all the nerves and clusters of neurons that interconnect the CNS and the rest of the body


What comprises the central nervous system? What is its main role?

- cerebral hemispheres
- diencephalon
- cerebellum
- brainstem
- spinal cord
Analysis and integration of sensory and motor information


What are the sensory components of the PNS?

- sensory ganglia and nerves
They sensory receptors at the surface and within the body that respond to internal and external environment


What are the motor components of the PNS?

Visceral Motor System
- sympathetic
- parasympathetic
- enteric
--> autonomic ganglia and nerves that act on smooth muscles, cardiac muscles and glands

Somatic motor system:
- motor nerves that act on skeletal (striated) muscles


What was Descarte's view of brain function?

Fluid, pumps, and the pineal
- thought that since there was fluid in the brain it pumped this around the body into muscles etc to make them do stuff
Light enters eyes - causes vibrations which trasmit into the brain.
Based on things that he knows - pumps etc and applying this to his theories


What was Paul Broca's contribution to neuroscience?

Studied a post mortem brain of a right hemiplegic patient ("Tan")
The patient was, from the age of 21, unable to produce speech
- developed the idea that we can associate certain bits of the brain being damaged with specific problems
- the ability to produce words is developed by the left frontal hemisphere, not the ability to understand
- showed that the brain was actually modular - not just one giant thing


What are technologies we can use to look at the brains of living people?

CT scan (x-ray) - 2D slices that can be put into 3D pictures

MRI (magnetic resonance imaging)
More high resolution, completely non invasive (not even worry of Xrays)

Can look in real time of the problems that people have and determine where these problems are localised

Localisation of function (without lesions): fMRI (functional MRI)
Get someone to do a task and monitor blood flow in the brain

Brain imaging, like brain lesions, tell us something about "where" but now "how"
New technology: not as a metaphor to interpret observations, but to extend them, the microscope


What is the neuron?

- the nerve cell
- there are many types of neuron arranged in various combinations in different regions of the nervous system
- most a branched
- tend to aggregate in layers
- with the discovery and characterisation of bioelectric activity, it became clear that a major functional basis of neural tissue is that neurons are excitable cells
- the nervous system receives, processes and outputs information in the form of electrical signals that travel along the processes of neurons (axons and dendrites)


How do nerve cells communicate?

Communication between neurons occurs at special structures (synapses) via chemical messengers


What sort of nervous systems do different animals have?

Features that appear to be conserved: the small scale reveals the most similarity.

Neurons operate in the same way in all animals. The mechanisms of excitability, information transmission, transfer and integration are essentially identical.

The neurons are basically the same, and are made of the same or homologous molecular and macromolecular structures


In what way is there more to genomes than genes?

Different species have different sized genomes but these do not reflect the complexity of the organisms.

Most of the genes expressed in cells are common to all cells - the "house-keep" genes that subserve essential cell function (e.g. transport, metabolism, structural and synthesis). Only a small proportion of genes contribute to the unique cell phenotypes. There are more cellular phenotypes in the nervous system than any other organ or organ system.

Our 23,000 genes make hundreds of different cell types that combine into complex tissues, organs and organ systems. Among this complexity we see cells that are specialized to detect external and internal signals, and to transmit and process information, and control actions.


What is the role of the brain in perception and awareness?

We tend to think that the external or real world has the properties we perceive, but these properties are the conscious experiences generated by the actions of the nervous.

But there are realms of experience that are not perceptions originating in the external world. What is being perceived in conscious experiences like anxiety or pain?

By what means do nervous systems, at least complex ones, produce consciousness?

And why should we bother about what metaphors we might be tacitly applying? Ou models of how things work dictate what we attend to, what observations we make.

What we do understand about the nervous system fits with the limits of the metaphors we employed to make sense of the observations. But there is nothing like consciousness, there is nothing in our observation of consciousness that suggests its components or principles of operation.

If we think that the brain is a computer, will we miss those aspects which are not computer-like? What explanatory gaps will it leave? In what way do brains and computers differ?