Lecture 2 - The Neuron Flashcards
Why do you need nerves
You need nerves in order to make a mass of flesh, blood and bones actually become an organism
- information has to flow done all these pathways
How do neurons work?
Neurons work by passing excitation along
- specifically via Chemicals
- and the imbalance of chemicals causes an electrical charge
- they have an internal structure, with chemicals inside
- they sit in cerebrospinal fluid
- At rest, a neuron is at perfect balance between inside and outside - not producing an electrical charge
Action only occurs when something disrutpes this balanced state and produces an electrical charge
Outline the process of excitation
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SO Neurons, like any other cell, are in a bath of liquid (CSF). And in this liquid are chemicals
- they also have chemicals on the inside
- these chemicals, like batteries have electrical potential
- at rest, chemicals outside and inside are in electrical balance
- A chemical ‘prompt’ comes in from a neighbouring neuron
- hits the outside, changing balance between inside and outside
- membrane becomes pourous so chemicals can come in and spread out (making difference between inside and outside spread out across the neuron) - This new Chemical changes the electrical conductivity of the cell - it’s no longer resting
- The +ve/-ve balance of electrons in the chemicals has a ‘whiplash’ effect down the neuron, spreading out the electrical charge
- THIS IS THE ACTION POTENTIAL - This whiplash travels down the neuron until it gets to the other end, where the electrical force then releases its own prompt to the next neuron
This is neuronal transmission
What are the input sites and output sites of a neuron
Each neuron has:
- Inputs via DENDRITES
which match up to the - Outputs to TERMINAL BUTTONS
which match up to next neurons dendrites etc
They are not in contact!
Why are neurons not in contact with each other?
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Otherwise it would either constantly be on or off
- need the synaptic gap to act as the connections on or off switch
- each neuron has multiple connections (switches) with multiple others
This indicates the huge amount of connections
How many neurons do we have?
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- About 100 billion in brain as a whole
- only have neurons in the CNS, but most are in the brain - Of which 10 billion are in cortical area
- this is the area of the brain that seperates us from lower order mammals
- where all things that make us human take place: thought, reasoning, imagining, language - A further 1 billion in the spinal cord
What is neuronal transmission speed?
Fast pathways = c. 300KPH (kilometres an hour)
Slow pathways = c. 3 KPH (kilometres an hour)
How are Neurotransmitters involved in this system?
Neurons send chemicals across the synapse, to proceed excitation/ inhibition
- these chemicals cross the gap and stimulate the next neuron along
- these bond with the next neuron in the chain and repeat the process
- These chemicals are neurotransmitters
They float across to the dendrite of the next neuron, where there are little ports (receptor sites)
- they wait until the NT’s arrive and change the electrical force
What are the parts of the neuron?
- Soma - Cell body, houses the DNA
- Myelin sheath - protects axon, facilitates conductino of electrical signal
- Synaptic Knob - where the signals travel along to
- NT crosses synapse - Activates receptor cells on dendrites
What are Neurotransmitters
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They are: a) Local, b) Native, c) present from birth
- but: They can be enhanced, or directly altered by external agents
E.g. Meth can release DA by fooling cell into dumping DA into the synapse, causing a surge of exhiliration
- DA in large proportions is enjoyable but can be dangerous
2 Important and widely present ones:
1. Dopamine & 2. Serotonin
• implemented in medical treatments for depression and Sz - those with depression hasn’t got enough, those with Sz have too much
By locating the problematic NT, you can either increase or reduce the amount of it
- they are building blocks that can be intervened with to change the persons state
