What is the brain ?
Vast collection of interconnected cells called neurons.
1012 neurons with 1015 synapses (connections)
cortical neurons connect to roughly 3% of surrounding neurons
cortical neuron may receive connections from up to 10000 other neurons
"Supported" by an even greater number of cells called glia (not nerve cells!)
Many different types of neurons in terms of size, shape and molecular properties (12 general types in the neocortex). Each neuron has three distinct parts:
cell body (soma) - can be the site of input, mainly inhibitory
dendrites - input zone
axon - output pathway
Neurons are connected together in particular ways to form functional circuits, much like transistors, resistors and capacitors are connected to form electronic circuits.
Neurons communicate via electrical impulses called action potentials
there are other forms of communication as well e.g. gap junctions
Effect (via an action potential) of one neuron on another can be
excitatory - encouraging the receiving neuron to emit an action potential
inhibitory - discouraging the receiving neuron from emitting an action potential.
Neurons
English: Micrograph of the visual cortex.
English: Drawing illustrating the process of synap...The parts of the brain
Spinal cord
signals to and from the muscles travel to the brain via the spinal cord
also sensory signals for touch, temperature, pain etc (somatosensory signals)
cord consists largely of axons conducting information from sensory cells to the brain, and information from the brain to motor neurons that drive muscles
cord also contains a large number of neurons, both motor neurons and interneurons
much processing takes place locally in the spinal cord giving rise to what we call reflexes
Brain stem
"half-way house" through which passes all sensory information on its way to the brain, including visual and auditory information (but not olfaction)
the main "way station" is the thalamus
much low-level (unconcious) processing takes place here
Cerebral Cortex
sight of all high...