TEST #2, on the nervous and endocrine systems, was completed. Scores to the FIRST part of the test (the scantron-scored part) are currently posted on the web, the correct answers are on the bulletin board outside my office (A211) and the second part of the test, the short answer questions, will be graded over the weekend.

 Next, we are going on to the topic of SENSATION

Introduction to Sensation:  This section deals with how the brain gets information about the rest of the body and the outside world. Sensory neurons are specialized cells that react to specific stimuli (energy or chemicals) in the environment, changing them into neural impulses. The frequency and intensity of the environmental stimuli are translated (transduced) into patterns of neural activity that are received by the specific areas of the brain that then organized the sensory messages to make sense out of them.

In humans, the neonatal brain is a relatively empty 'black box' which can manage the basic vegetative functions (breathing, circulation, digestion, etc) and has a few instincts/reflexes/motor patterns needed for immediate survival (the sucking reflex, for example). Initially, the assault of sensations from the environment may be overwhelming to the newborn, who does not yet have a framework for perception of the outside world. Neither can a newborn block or filter out excessive stimulation by the senses: he or she can only block them by sleeping or crying. While the newborn infant  has little ability to manage, much less understand, the flow of information, he or she both a tremendous drive and phenomenal ability to learn, forming sensory patterns that take on meaning,  and soon is also able to attend to some stimuli while ignoring or blocking out others.

Just as the brain is 'plastic', the sensory system, a specialized part of the whole nervous system, also demonstrates some plasticity. The damage or absence of one sensory system increases the sensitivity of other sensory systems, especially when it occurs early in life, but, to some degree, at all ages. The sense of hearing of a blind person can be more acute, and a person who loses his ability to hear may become extra sensitive to visual inputs.

2. The different senses: what is it they 'sense'?

• The sensory information available to humans includes energy radiation  (electromagnetic, light, heat), physical forces such as vibrations (sound) or pressure., chemicals (taste, smell and pain), kinetic (motion) and the direction of gravity (orientation in space) are some of the kinds of information available that tell us about the world outside and within our bodies.
• The senses humans use to detect this information include: sight, hearing, olfaction (smell), gustation (taste), balance, the kinesthetic senses which tell us about inertia (movement or lack of movement) and our position in space relative to gravity, and the somasthetic systems that are report pressure, pain, heat, cold and position or movement of the body's parts to the brain.

Many of the sensory systems which bring us information about the environment from outside the body, either near (taste, smell), far (sight, hearing), or of our heads' motions and position in space, are located in the head, just outside the skull. (remeber, there are no sensory receptors within the brain itself.) When there are two separate organs for a particular stimulus, the 'stereo' reception of sensation provides additional information about location, distance, movement and some more subtle kinds of information.

The somasthetic senses, which bring us information about what is going on within our bodies (pain, pressure or touch, heat and cold, and location of the body parts in space relative to the rest of the body) are dispersed throughout the body and communicate with the brain through the spinal column.

These systems must work together to enable us to balance and coordinate our movements in order to avoid (or escape from) danger and to obtain the necessities of life.

All the sensory systems go through the same steps in bringing information to the brain, but the kinds of information and details of how they do it vary from one sense to the next.

Steps to the sensory and perceptual processes:

1. Stimuli reach the sensory organs and are received/prepared/carried to... 
2. ....the sensory neurons in a particular intensity, frequency and rhythm which are converted into neural impulses in patterns that... 
3. ...are carried by way of the sensory nerves, the information about the rhythm, frequency and intensity of the stimuli to the....
4. ...specific location in the brain that is structured to receive this kind of information and pass it on to .........
5. ...the association areas of the brain that organize the neural impulses into perceptions, patterns that make sense of the information.

Writing assignment: begin drafting a detailed essay which will eventually comprise 50% OF THE GRADE FOR THE NEXT TEST on a comparison of  how visual and auditory information about your environment gets transmitted to the brain, describing the similarities and differences in processes and paths of the flow of these two types of information in detail. Nothing to hand in for the next class, but be prepared for a mini-quiz on the senses.