Psychology Chapter on Senses and Thresholds

Conscious vs Unconscious Senses

• Conscious senses are perceived consciously, include hearing, pain, temperature, touch, pressure, taste, and smell.
• Unconscious senses are not perceived consciously, include chemoreceptors and baroreceptors.
• Baroreceptors detect blood pressure and carbon dioxide levels.

Absolute vs Discriminative Threshold

• Absolute Threshold is the minimum stimulus needed to activate a sense.
• Discriminative Threshold is the minimum difference between two stimuli that can be perceived as different.
• Three types of discriminative thresholds are
  • Spatial Discriminative Threshold: Minimum distance between two stimuli that can be perceived as two distinct points.
  • Temporal Discriminative Threshold: Minimum time difference between two stimuli that can be perceived as two distinct events.
  • Intensity Discriminative Threshold: Minimum difference in intensity between two stimuli that can be perceived as two distinct intensities.

Phototransduction in Bipolar Cells

• Bipolar OFF Cells are sign-conserving.
• Bipolar ON Cells are sign-inverting.
• Bipolar OFF Cells respond to a lack of neurotransmitter in light conditions.
• Bipolar ON Cells respond to the presence of neurotransmitter in dark conditions.

Phototransduction in Ganglionar Cells

• Ganglionar OFF cells are sign-conserving.
• Ganglionar OFF Cells respond to the presence of neurotransmitter in dark conditions.
• Ganglionar ON Cells respond to a lack of neurotransmitter in light conditions.
• Receptive Fields are areas of photoreceptors connected to one bipolar and ganglionar cell.
  • The center of the receptive field is connected to the ganglionar cell.
  • The periphery of the receptive field is connected to horizontal bipolar cells, which are not connected to the ganglionar cell.

Weber's Test

• Weber's test is used to assess hearing loss.
• A tuning fork is placed on the forehead.
• Normal air conduction and bone conduction in both ears will result in the sound being heard equally in both ears.
• Air conduction greater than bone conduction will also indicate normal hearing.
• If the sound is not heard equally in both ears, there is either conductive hearing loss in the ear that hears the sound better or sensorineural hearing loss in the ear that hears the sound worse.

Rinne's Test

• Rinne's test is used to determine the type of hearing loss: conductive or sensorineural.
• It is performed by placing a tuning fork on the mastoid bone and then in front of the ear.
• A positive Rinne's test indicates that air conduction is better than bone conduction, which is normal.
• A negative Rinne's test indicates that bone conduction is better than air conduction, which is a sign of conductive hearing loss.

Endolymph

• Endolymph is a fluid in the inner ear.
• It has a high potassium concentration (150 mM/L) and a positive potential (+80 mV).
• Meniere's disease is characterized by decreased endolymph removal from the inner ear.
• Symptoms include vertigo, sensorineural hearing loss, and tinnitus.

Sound Transmission Through Inner Ear

• Stapes movement against the oval window creates shock waves that travel into the scala vestibuli, increasing pressure in the scala vestibuli and causing the basilar membrane to move down.
• As the pressure increases, the tectorial membrane moves inwards and the hair cell stereocilia are bent towards the shortest one.
• This closes mechanosensitive K+ channels and reduces K+ influx.
• The pressure then decreases, causing the basilar membrane to move back up.

Vestibulo-Ocular Reflex (VOR)

• The VOR ensures a stable visual world during head movements.
• If the head is turned to the right, the left eye will move to the left, and the right eye will move to the right.
• This is achieved by:
  • Excitation of contralateral abducens nucleus: This causes the lateral rectus muscle on the contralateral side of the movement to contract.
  • Excitation of ipsilateral oculomotor nucleus: This causes the medial rectus muscle on the ipsilateral side of the movement to contract.
  • Inhibition of ipsilateral abducens nucleus: This causes the lateral rectus muscle on the ipsilateral side of the movement to relax.
  • Inhibition of contralateral oculomotor nucleus: This causes the medial rectus muscle on the contralateral side of the movement to relax.

Pain Perception

• Pain perception is a complex process involving different types of receptors, neurons, and brain regions.
• Free nerve endings are specialized sensory receptors that respond to mechanical pressure, temperature, and chemicals.
• These receptors are found in the skin, muscles, and internal organs.
• When these receptors are activated, they generate electrical impulses that travel along sensory neurons to the spinal cord and then to the brain.
• The brain then interprets these signals as pain.

Explore the distinctions between conscious and unconscious senses, including the mechanisms of baroreceptors and chemoreceptors. Learn about absolute and discriminative thresholds, and discover the various types of discriminative thresholds that aid perception. This quiz will deepen your understanding of sensory processing in psychology.