Biology of the Mind

 Glial cells

 “Neural Glue” 

○ Support cells 

■ structural, nutritional, protection, etc. 

■ aid in communication within nervous system 

○ Constantly replacing themselves 

■ ∴ unsure how many in the brain 

■ Old researchers hypothesized there are a trillion glia 

● 90% of the brain’s cells were made up of glial cells 

■ Recent research suggests that # of glial cells = # neuron 

● 86 billion of each exist in the brain 

Neuron

○ Nerve cell/ Information processing cells 

○ Basic building block of the nervous system 

○ Responsible for receiving & transmitting electrochemical info 

○ Tightly close together in intricate groups & networks but they don’t touch one another (in terms of communicating info) 

■ Communication within neuron is electrical 

■ Communication between neurons is chemical (because 2 neurons don’t touch) 

The Neuron Structure

Dendrites

reaching arms that receive & integrate info and send impulses along to the cell body 

Cell Bodies (Soma)

contains nucleus, here chemical processes occur that keep neuron alive & nourished 

Axon

long tube like structure that allows the neuron to pass info to other neurons/bodily structures (muscles, glands) 

Axon Terminals

on branches at the end of the axon, where message leaves the neuron (they don’t touch other cells, neurons, muscles) -

Synapse/Synaptic Gap

gap between axon of one neuron and dendrite of the next

Myelin Sheath 

Many axons are covered with a tube-like MYELIN SHEATH 

◆ A fatty whitish insulation layer derived from glial cells 

◆ Insulates the axons of some neurons, and speeds up message transmission ➔ Allow electrical conduction to skip from node to node 300 km/hr ➔ Functions: 

◆ Speeds up transmission of info 

◆ Keeps message intact from soma to axon terminals 

Nodes of Ranvier

◆ Intervals where the myelin sheath is either thin or absent 

◆ These gaps are normal; however, decay of myelin sheath is abnormal ● Seen in multiple sclerosis 

● Decay of myelin sheath makes it difficult for neurons to pass on 

messages to muscles & other neurons 

○ leading to axons being exposed & breaking down 

○ Results in impaired sensation, movement & muscle control 

● Impulses slow down & mixed messages occur 

With

Electrical transmission