1) This document discusses sensation and the sensory processes through which our senses detect external stimuli and transmit that information to the brain. 2) It defines sensation and describes the sensory receptors and transduction of different energy types like light, sound, and chemicals. 3) Several factors that influence sensation are discussed, including thresholds, signal detection theory, and sensory adaptation in which we become less sensitive to constant stimuli over time.

1. How do we become aware of our External and
Internal Environment??
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2. 2

3. Lecture Objectives
1.Define the term sensation
2.Explain sensory processes
3.Describe factors that influence sensation
4.Explain the relevance of sensation in nursing
5.Compare sensation and perception processes
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4. Sensation
 The process through which the sense organs pick up:
 Visual
 Auditory
 Other sensory stimuli
and
 transmit them to the brain
 Sensory information that has registered in the brain but has
not been interpreted
• The process by which one form of energy is converted into
another form
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5. Sensation
 Sensory organs contain receptors that transduce sensory
energy into nerve impulses that are carried to the brain
 Sensory organs capture a certain type of energy which must
be of sufficient quantity to be perceived
Energy types:
 Eye: electromagnetic - photoreceptors (light)
 Ear: expanding and compressing molecules of air (waves)
 Nose and tongue: airborne or substance chemicals
Chemoreceptors (taste, smell, oxygen level)
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6. Sensation
Energy types:
 Skin: Pressure, temperature, touch , pain, stretching,
movements
• Mechanical input - mechanoreceptors (stretching,
movements)
• Thermoreceptors (cold, warmth)
– Electromagnetic - electro receptors
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7. Sensory Processes
1. Stimulus is received by sensory receptors
2. Receptors translate stimulus properties into
nerve impulses (transduction)
3. Feature detectors analyze stimulus features
4. Stimulus features are reconstructed into neural
representation
5. Neural representation is compared with
previously stored information in brain
6. Matching process results
Sensation
Becomes
Perception
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8. Factors that influence sensation
1:Threshold-lower limits of sensory experience
– Each sensory system has a threshold level of energy that
is required to activate that sense
– Different people can have widely varying sensory
thresholds
– Thresholds can change within a person over time and as a
function of hormone status
• Olfactory sensitivity during pregnancy
• Ability to taste foods as we get older 8

9. Factors that influence sensation
Absolute Threshold- the point at which a stimulus goes from
undetectable to detectable to our senses.
– It is the softest sound we can hear or the slightest touch
we can feel
– Also defined as the smallest amount of energy that can be
detected by a system. 9

10. Factors that influence sensation
Difference Threshold (Just Noticeable Difference )- amount
of change needed to recognize that a change has occurred in
the stimulus that was detected
OR
– Smallest difference between two stimuli that can be
detected
– Also defined as the smallest difference in sensory
energies that can be detected
e.g. Recognizing increasing radio sound
becoming louder
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11. Factors that influence sensation
Difference threshold can be influenced by;
– Habituation: the brain “gets used to” certain non-
threatening environmental stimuli and tunes them out
– Other factors?......................
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12. Factors that influence sensation
2: Signal Detection Theory-ability to detect what we want to
focus on and ignore or minimize everything else.
– Focusing our attention on certain things while at the same
time attempting to ignore the flood of information
entering our senses
– The point of our ‘detection’ of a stimulus varies
depending on a number of factors, including:
• Experience
• other environmental stimuli
• Fatigue
• Expectation
• Significance of stimulus 12

13. Factors that influence sensation
3: Sensory Adaptation- The process of becoming less
sensitive to unchanging stimulus:
– E.g. when we notice certain smells or sounds right away
and then after a while they fade into the background
– E.g Once we adapt to the perfume or the ticking of the
clock, we stop recognizing it.
NB: In Sensory adaptation, repeated or constant
stimulation decreases the number of sensory messages
sent to the brain, which causes decreased sensation
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14. Areas for Further Studies
Read and Write Notes on physiology of the Following Senses
• Pain including the gate control theory of pain
• Vision
• Hearing
• Olfaction
• Gustation
• Touch
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References
• Feldman, R. S., & Feldman, R. S. (2014). Essentials
of understanding psychology. New York: McGraw-
Hill.