3 types of neurons: Sensory neurons, Interneurons & Motor neurons Explain the ro

Question

3 types of neurons: Sensory neurons, Interneurons & Motor neurons Explain the role of each type of neuron in a simple reflex action (note that communication with brain occurs AFTER motor neuron reacts):

The Tools of Discovery:  Having Our Head Eamined.

Summarize the type of brain imaging that can be produced by each technique.  

a.  Electroencephalogram (EEG):Response:

b.  PET (positron emission tomography): Response:

c.  MRI (magnetic resonance imaging) and fMRI (functional MRI)::

Drives, motivations, cravings and addictionsare influenced by in neural clusters in the hypothalamus.  Explain the function of the “reward center” in the hypothalamus, and explain “reward deficiency syndrome” and how it specifically influences addictive behaviors:

Explanation / Answer

Sensory neurons are also known as afferent neurons that convert specific type of stimulus, via their receptor into action potential. This process is called sensory transduction.This sensory information travels along afferent nerve fibres in an afferent or sensory nerve to the brain via spinal cord. The stimulus can come from extoreceptors outside the body for example light or sound or from interoreceptors inside the body, for example blood pressure or the sense of the body position.

Interneuron found in the spinal cord,relays signal between sensory and motor neurons.The integration of sensory feedback signals and central motor commands at several level of central nervous system play critical role in controlling movement. The most efficient way to gate sensory signals in reflex pathways is to control the firing level of interneurons.For example: during locomotion the interneuronal activity is modulated via excitation or inhibition depending on reflex pathways.

A motor neuron is a neuron whose cell body is located in motor cortex, brainstem or the spinal cord and whose axon fiber projects to spinal cord or outside the spinal cord to directly or indirectly control effector organs mainly muscle or glands. A single motor neuron may innervate many muscle fibers and muscle fiber can undergo many action potentials in the time taken for a single muscle twitch.

a. Electroencephalogram : is use to record the electrical activity of brain. It is typically non invasive, with the electrode placed along the scalp, although invasive electrodes are sometimes used such as electocorticography.

b.PET: is used to observe metabolic processes in the body as an aid to the diagnosis of disease.

c. MRI : MRI scanners use strong magnetic field, electrical field gradients and radio waves to generate images of the organs in the body.

fMRI: measure brain activity by detecting changes associated with blood flow.

The reward center isa group of neural structure responsible for motivation, craving for reward ,wanting, desire, associative learning and positive emotions. Reward is the attractive and motivational property of stimulus that induces appetitive behavior also known as approach behaviour and consummatory behaviour.

Reward deficiency syndrome: temporary imbalance of dopamine receptors in the prefrontal cortex relative to the striatum creates reward deficiency syndrome producing behaviour among young adolescent that is not unlike that seen among individuals with certain type of functional dopamine deficits.

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