synapses and networks

Who were the key founders of neuroscience?

- Camillo Golgi (1943-1926): Developed histological staining of neurons

- Santiago Ramon y Cajal (1853-1934): "Father of neuroscience," neuroanatomist and artist

- Shared Nobel Prize in Medicine and Physiology in 1906

What is the Neuron Doctrine?

- Brains are composed of separate neurons and other cells

- Cells are independent

- Neurons are polarized cells

- Information is transmitted across tiny gaps between cells

What are the typical locations of synapses?

- Axo-dendritic

- Axo-somatic

- Axo-axonic

- Dendritic-dendritic (rare)

What happens during chemical synaptic transmission?

1. Action potential in presynaptic neuron

2. Opening of calcium voltage-gated channels

3. Fusion of neurotransmitter vesicle with membrane

4. Release of neurotransmitters into synapse

5. Neurotransmitters connect to postsynaptic receptors

6. Creates EPSP or IPSP

What are the two types of postsynaptic receptors?

1. Ionotropic receptors:

- Ligand-gated ion channels

- Fast acting

2. Metabotropic receptors (GPCRs):

- Coupled to G proteins

- Slower acting

- Control ion channels indirectly

- Control enzymes within cell

What are the main excitatory and inhibitory neurotransmitters?

Excitatory:

- Glutamate

- Aspartate

- Nicotinic acetylcholine

- Muscarinic ACh

Inhibitory:

- GABA

- Glycine

- Muscarinic acetylcholine

What is summation in neural signaling?

1. Temporal summation: Stronger response when neurotransmitter is released for longer time

2. Spatial summation: Combined effect when multiple synapses are activated simultaneously

What determines if a neuron will transmit a signal?

- Balance between excitatory (EPSP) and inhibitory (IPSP) inputs

- Must reach threshold through summation

- More excitatory input = stronger output signal

- More inhibitory input = weaker or no output signal

What happens in the synapse besides transmission?

- Reuptake transporters return neurotransmitters to presynaptic neuron

- Auto-receptors and hetero-receptors regulate presynaptic neuron

- Enzymes degrade neurotransmitters in the synapse

How is information coded in neural networks?

- Through spatial and temporal summation at synapses

- Network connectivity (connectome) determines signal path and strength

- Feedback loops (positive and negative) influence signals

- Pattern of connections determines information flow