Sensory%20Receptors

1
Sensory Receptors
2
Receptors

• There are millions of receptors all over the
  body. Receptors may be simple naked nerve
  endings, encapsulated nerve endings or complex
  structures.
• Receptors detect stimuli (internal or external)
  convert them to nerve impulses

3
The sensory receptors

• Each sensory system has three component parts
  1)Sensory receptors which are the branched
  endings of sensory neurons or specialized cells
  adjacent to them that detect specific stimuli.
  2)Nerve pathways lead to the brain. 3)Brain
  regions process the information into a sensation
  later, perhaps, a perception (understanding) of
  the sensation will be made.

4
How does a sensory receptor work?

• Some sensory receptors are activated when they
  are bent, squished, or disturbed in some way. 
• Others are activated by chemicals. 
• Others by temperature. 
• And others by light. 
• Whatever the outside world influence is, we can
  call it a stimulus for the receptor

5

• Whatever the appropriate stimulus is, that will
  cause a depolarization to occur in the sensory
  receptor cell
• The depolarization within the sensory dendrite
  itself (due to the stimulus) is called a receptor
  potential
• When the dendrite is deformed, its membrane
  stretches, and ions can flow through the
  stretch-gated channels.  If this occurs enough,
  there will be enough of a receptor potential to
  trigger an action potential.

6
In summary
7
Sense of touch

• Touch may be considered one of five human senses
  however, when a person touches something or
  somebody this gives rise to various feelings the
  perception of pressure (hence shape, softness,
  texture, vibration, etc.), relative temperature
  and sometimes pain.
• The term "touch" is usually replaced with somatic
  senses, to better reflect the variety of
  mechanisms involved

8

• Free nerve endings are simply branched endings of
  sensory neurons in the skin that function as
  mechanoreceptors, thermoreceptors, and pain
  receptors.
• Meissner corpuscles adapt slowly to vibrations of
  low frequencies.
• The bulb of Krause is a thermoreceptor that is
  sensitive to temperatures below 20 degrees C.
• Ruffini endings are sensitive to steady touching
  and pressure, and to temperatures above 45
  degrees C.
• Pacinian corpuscles are located both in the
  dermis and near joints they are able to detect
  rapid pressure changes associated with touch and
  vibrations.

9
Sense of vision

• Vision requires a complex system of
  photoreceptors and neural program in the brain
  that can interpret the patterns of action
  potentials
• All photoreceptors incorporate pigment molecules
  that can absorb photon energy, which can be
  converted into excitation energy in sensory
  neurons.
• The photoreceptors are located in the retina

10
(No Transcript)
11
Results

• Normal Color Vision A 29,  B 45,  C --,  D
  26  
• Red-Green Color-Blind A 70,  B --,  C 5, 
  D --  
• Red Color-blind A 70,  B --,  C 5,  D 6  
• Green Color-Blind A 70,  B --,  C 5,  D 2

12
Sense of hearing

• Hearing is the perception of sounds, which are
  traveling vibrations of mechanical energy

13
Hearing test

• Normal human hearing ranges from 20 Hz to 20 kHz
• A gradual decline with age is considered normal

14

• The middle ear contains small bones with amplify
  the sounds
• before transmittal to the inner ear.
• The external ear in mammals has a pinna for
  collecting the
• sounds.
• In the cochlea of the inner ear, acoustical
  receptors in the
• form of hair cells respond to pressure waves
  transmitted
• through the surrounding fluid.
• Impulses are sent along the auditory nerve to the
  brain for interpretation.
• The hair cells of the human ear can be
  permanently damaged by prolonged exposure to
  intense sounds

15
Sense of smell

• Olfactory receptors are responsible for our sense
  of smell.
• They respond to a variety of odour molecules
• Humans have about 5 million olfactory receptor
  neurons
• Olfactory receptor neurons reside on the
  olfactory epithelium in the nasal cavity

16
Sense of taste

• Taste receptors enable animals to distinguish
  nutritious from noxious substances. Receptors
  of some animals are located on antennae, legs,
  tentacles, or fins. In humans, taste receptors
  are often components of taste buds distributed
  mostly on the tongue.

17
Questions

• What are receptors?
• What are the three components of the sensory
  system?
• How many senses do we humans have? Five or more?
  Name them
• How does a sensory receptor work? (Brief
  description)
• What is the name of the receptor involved in your
  sense of smell?
• Where are the sense of taste receptors located in
  the human body?