Flashcards in Lecture 1- Why have a nervous system? Deck (23)
What is Aridopsis thaliana and what is its significance?
-very distant relative of humans
-27 000 genes but no nervous system
-demonstrates that nervous system is not essential for life
-the first organism to have its entire genome sequenced
Where is the first primitive nervous system found?
-corynactis californica, simple sessile invertebrate
-very little organ/tissue specialization
-a "nervous system" comprising a network of nerve cells
What is the distinguishing feature of nerve cells?
-excitable cells, relay information between cells
-cells communicate with each other
What are the functions of a nervous system?
-homeostatic regulation (nervous system has a big role in that)
-control movement (-huge proportion of the human nervous system is dedicated to movement control, controlling the biochemical machine )
-reveal the universe= make us think, conscious, we don't know of any other thing capable of producing consciousness other than brain
What are the basis for the thought that heart is the center of thinking for Early Egyptians?
-early Egyptians= observed that everything that the world depended on the flow of fluids (Nile) and the heart has lot of connections of fluids= the center
Who was the first to say the brain was a center of thought?
What are the reasons for the idea that heart is the center of thinking not the brain?
-brain just sits there whereas the heart moves
-simple animals move and react when they don't have a brain (Aristotle's argument, he was cardiocentric and his thinking influenced the coming generations)
-warmth (=life) emanates from the body's core (the heart)
-all the ancient civilizations thought the heart to be the centre of conscious being
-the observation that more sophisticated animals have bigger brains was explained by saying that they needed more cooling as they have more blood= more heat (brain= coolant)
What did Galen do?
-admired Hippocrates and accepted brain as the seat of intellect but he observed that the brain has fluid filled chambers right in the middle= that's and thus said it works on fluids and flows as well, the classical explanation of bodily humours
-Galen observed the bodies of injured gladiators and unlike the Greeks the Romans were able to investigate corpses
-Galen didn't like the idea that how big brain is determines intelligence=as donkeys have a big brain and not clever!
-in the Renaissance the importance of detailed observation and questioning of doctrine was reinstated but the mechanistic explanation of humours remained
What are the two main divisions of the nervous system?
-CNS= brain and spinal cord (central because it is encased in bony structures)
-PNS= cranial nerves and spinal nerves (peripheral because it connects the central and the muscles etc.)
What systems does the CNS convey information too?
-sends information to motor components that are divided into visceral motor system and somatic motor system
What does visceral motor system convey information to and what is does it consist of?
-consists of: parasympathetic, sympathetic and enteric divisions
-the autonomic ganglia and nerves send info to:
-Effectors: smooth muscles, cardiac muscles and glands
What does somatic motor system convey information to and what is does it consist of?
-consist of motor nerves that send info to:
-effectors: Skeletal (striated) muscles
How does the CNS obtain information about the internal and external environment?
-internal and external environment conditions are detected by sensory components, first by sensory receptors (at surface of the body and within) and then info passed onto sensory ganglia and nerves that send it to the CNS
-CNS then analyses and integrates the information
What is the role of the CNS?
-analysis and integration of sensory and motor information
What was Descartes' view of the brain?
-fluid and pumped and sends fluid around the brain and out of the brain and taht is how it works the muscles
-how is it that process produces a concious being, he said= humans have a mechanical communicates with the spiritual= pineal gladn (because there is only one and directly above the ventricles with the fluid)
What did Paul Broca do?
-Paul Broca= brain is not a holistoc thing, it has modules, different bits that do different things
-figured it out from a case of a patient who was quadriplegic and had damaged bit of a brain= couldn't speak
-only make one sound= Tan
-he could understand speech but couldn't produce it
-broca collected about 11 of these cases and on the basis of that decided that bit of teh brain produces speech
How can we observe the brain today?
-MRI- harmless, radio waves
-CT scan (X-Ray)
-fMRI -follows oxygen levels in the brain to determine which areas are active,subtle changes in blood flow= to determine how active which regions of the brain are
-we can find out which bits do what but we still do not know how!
What do we have to understand to understand how an organ works?
-how the individual components and cells work
-neurons are vastly varied
How do neurons communicate?
-nervous system receives processes and outputs information in the form of electrical signals that travel along the processes of neurons (axons and dendrites)
Are nervous systems of different organisms similar?
- small scale reveals most similarity
- neurons operate in the same way in all animals
-the mechanisms of excitability, information, transmission, transfer and integration are essentially identical
What determines the complexity of an organism?
-not how many genes but how complex the brain is
What are the roles of most of the genes in the body?
-only a small number of cells determines the phenotype of a cell
-there are more cellular phenotypes in the nervous system than there are in any other organ or organ system