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Thinking Through The Concepts
1. List four major parts of a neuron, and explain the specialised function of each part.
Dendrites: Ramifications protruding from the neuron’s soma that respond to stimuli from other nerve cells or from the environment.
Cell Body (Soma): It performs two important functions: It contains the organelles that are found in most cells: nucleus, endoplasmic reticulum,and Golgi complex and it also integrates the various electrical impulses it receives from the dendrites.
Axon: A long, thin strand that extends out of the soma and conveys the action potential from the cell body to the synaptic terminals at its end, where it contacts another neuron.
Synaptic Terminals: Swellings at the end of the neuron’s axon that send electrical impulses to other neurons throughsynapses.
A typical synapse consists of three parts: the synaptic terminal of the “sending” neuron, a dendrite or cell body of a “receiving” neuron and a small gap that separates the two cells. Most synaptic terminals contain a neurotransmitter that is released as a response to an action potential reaching the terminal. At a synapse, the output of the sending cell becomes the input of thereceiving cell(s).
2. Diagram a synapse. How are signals transmitted form one neuron to another at a synapse?

3. How does the brain perceive the intensity of a stimulus? The type of stimulus?
The intensity of a stimulus is coded by the frequency of action potentials, the more intense the stimulus is, the faster the neuron produces action potentials and another way of coding intensity is the numberof similar neurons that “fire” at the same time. As for the type of stimulus, the brain distinguishes them by its connectivity from the senses. The nervous system interprets what a stimulus is by monitoring which neurons are firing action potentials because normally each type of stimulus results in action potentials in different axons that end up in in different areas of the brain.

Both motorand sensory neurons are localised within the spinal cord. If the cord is severed, sensory input form below the injury cannot reach the brain, and motor output from the brain cannot reach below that point either, thereby, body parts that are innervated below the injury are paralysed.
5. Draw a cross-section of the spinal cord. What types of neurons are localised at the spinal cord? Explain whysevering the cord paralyses the body below the level where it is severed.

7. What structure connects the two cerebral hemispheres? Describe the evidence that the two hemispheres are specialised for distinct intellectual functions.
The corpus callosum connects the two cerebral hemispheres and it has been proven through PET and functional MRI that each cerebral lobe specialises for differentintellectual functions, for instance the left hemisphere controls the right side of the body, input from right visual field, right ear, left nostril and hosts the centres for language, speech, reading, mathematics and logic, whereas the right hemisphere controls the left side of the body, input form left visual field, left ear, right nostril and contains the centres for spatial perception, music,creativity, recognition of faces and emotions.
10. Why are we apparently able to distinguish hundreds of different flavours if we only have five types of taste receptors? How are we able to distinguish so many different odours?
Through two mechanisms, first, a particular substance may stimulate two or more receptor cells to different degrees, second and more important, a substance being tasted alsoreleases molecules to the air inside the mouth which diffuse to the olfactory receptors that in turn contribute an odour component to the basic flavour. We can distinguish many different odours because we produce about 500 different types of olfactory receptor proteins that specialise to bind a particular type of airborne molecule and stimulate the olfactory receptor to send a message to the brain,...