Sensation and Perception

• Sensations are defined as the results of the triggering of a sensory organ They play a very significant role in the human body as they are the information that our basic senses accumulate, allowing us to feel and experience the world outside of our own.
• Perception

  • Involves signals that go through the nervous system, which in turn result from physical or chemical stimulation of the sensory system.
  • not only the passive receipt of these signals, but it's also shaped by the recipient's learning, memory, expectation, and attention
• Sensory Processes


  Senses provide information about the body and its environment.
• Humans have five special senses

  olfaction (smell), gustation (taste), equilibrium ( balance and body position), vision, and hearing.
• somatosensation


  Additionally, we possess general senses
• Vestibular sensation


  which is an orgnanisms sense of spatial orientation and balance, proprioception (position of bones, joints, and muscles), and the sense of limb position that is used to track kinesthesia (limb movement) are part of somatosensation
• sensory transduction


  Although the sensory systems associated with these senses are very different, all share a common function: to convert a stimulus (such as light, sound, or the position of the body) into an electrical signal in the nervous system.
• PROCESS

  • RECEPTION
  • TRANSDUCTION
  • ENCODING AND TRANSMISSION OF SENSORY INFORMATION
• RECEPTION


  Which is the activation of sensory receptors by stimuli such as mechanical stimuli (being bent or squished, for example), chemicals, or temperature. The receptor can then respond to the stimuli.
• TRANSDUCTION


  The most fundamental function of a sensory system is the translation of a sensory signal to an electrical signal in the nervous system. This takes place at sensory receptor, and the change in electrical potential that is produced is called the receptor potential.
• ENCODING AND TRANSMISSION OF SENSORY INFORMATION

  Four aspects of sensory information are encoded by sensory systems: the type of stimulus, the location of the stimulus in the receptive field, the duration of the stimulus, and the relative intensity of the stimulus. Thus, action potentials transmitted over a sensory receptor’s afferent axons encode one type of stimulus, and this segregation of the senses is preserved in other sensory circuits.
• Sight or vision (ophthalmoception) 


  is the ability of the eye(s) to focus and detect images of visible light on photoreceptors in the retina that generate electrical nerve impulses for varying colors, hues, and brightness.
• types of photoreceptors: rods and cones
• Rods are very sensitive to light, but do not distinguish colors.
• Cones distinguish colors, but are less sensitive to dim light. The inability to see is called blindness.
• Hearing or audition (audioception) is the sense of sound perception. Mechanoreceptors in the inner ear turn vibration motion into electrical nerve pulses. The vibrations are mechanically conducted from the eardrum through a series of tiny bones to hair-like fibers in the inner ear that detect the mechanical motion of the fibers.
• Sound can also be detected as vibrations conducted through the body by tactition. The inability to hear is called deafness or hearing impairment.
• Taste (gustaoception) refers to the ability to detect substances such as food, certain minerals, poisons, etc. The sense of taste is often confused with the concept of flavor, which is a combination of taste and smell perception.
• Flavor depends on odor, texture, and temperature as well as on taste.
• Humans receive tastes through sensory organs called taste buds, or gustatory calyculi, concentrated on the upper surface of the tongue.
• Five basic tastes exist: sweet, bitter, sour, salty, and umami.
• The inability to taste is called ageusia.
• interpretation of Smells Individual features of odor molecules descend on various parts of the olfactory system in the brain and combine to form a representation of odor. Since most odor molecules have several individual features, the number of possible combinations allows the olfactory system to detect an impressively broad range of smells. A group of odorants that shares some chemical feature and causes similar patterns of neural firing is called an odotope.
• Humans can differentiate between 10,000 different odors. People (wine or perfume experts, for example) can train their sense of smell to become expert in detecting subtle odors by practicing retrieving smells from memory.
• Smell and Memory Odor information is easily stored in long-term memory and has strong connections to emotional memory. This is most likely due to the olfactory system’s close anatomical ties to the limbic system and the hippocampus, areas of the brain that have been known to be involved in emotion and place memory.
• Human and animal brains have this in common: the amygdala, which is involved in the processing of fear, causes olfactory memories of threats to lead animals to avoid dangerous situations. The human sense of smell is not quite as powerful as most other animals’ sense of smell, but smell is still deeply tied to human memory and emotion.
• Touch or somatosensation (tactioception, tactition, or mechanoreception), is a perception resulting from the activation of neural receptors in the skin, including hair follicles, tongue, throat, and mucosa. A variety of pressure receptors respond to variations in pressure (firm, brushing, sustained, etc.).
• The touch sense of itching is caused by insect bites or allergies that involve special itch-specific neurons in the skin and spinal cord. The loss or impairment of the ability to feel anything touched is called tactile anesthesia.
• Paresthesia is a sensation of tingling, pricking, or numbness of the skin that may result from nerve damage and may be permanent or temporary.
• somatosensory system uses specialized receptor cells in the skin and body to detect changes in the environment. The receptors collect and convert physical stimuli into electrical and chemical signals through the transduction process and send these impulses to the nervous system for processing. Sensory cell function in the somatosensory system is determined by location.
• Mechanoreceptors in the skin give us a sense of pressure and texture. These receptors differ in their field size (small or large) and their speeds of adaptation (fast or slow).
• four types of mechanoreceptors based on the four possible combinations of

  fast vs. slow speed

  large vs. small receptive fields.