Biopsychology: Neurons

100 billion neurons in the human nervous system. 

80% of them are in the brain. 

Transmits signals chemically and electrically. 

They carry information around the body. 

There are 3 types of neuron: 

• Sensory 
• Motor 
• Relay 

Are in our ears, eyes, toung, skin. 

Carry nerve impulses from the sensory receptors (PNS) to the brain and spinal cord (CNS). 

Some terminate at the spinal cord - this allows quick reflex actions. 

Are only present in the brain and spinal cord. 

Connect the sensory and motor neurons. 

Can connect to other relay neurons as well. 

Connect to the CNS to effectors eg. muscles and glands. 

Information gets passed to a motor neuron when movement is required. 

Allows muscles to move eg. in a reflex.

Are chemicals 

Each have their own particular molecular structure - that fits with a postsynaptic receptor site. 

There are a range of different neurotransmitters (that have a different effect on the body). Eg. serotonin is responsible for mood (low serotionin - deppression). 

Whole process only takes a fraction of a second. 

After neurotransmitters are either: 

- Reuptake: taken back up by the presynaptic neuron. 

- Enzyme breakdown: broken down by enzyme in th esynaptic gap. 

Excitatory: increases the recieving neurons positive charge, thus they're more likely to fire. 

- Eg. adrenaline: neurons fire: physiologically aroused state. 

Inhibitory: decrease the positive neurons positive charge, therefore less likely to fire. 

- Eg. serotonin: low mood/ lack of happiness. 

- A nerve cell can recieve both at the same time. 

- Likelihood of a cel firing = adding up the excitatory and inhibitory synaptic input.