THE SENSORY SYSTEM

Question 1

The sensory system

Answer 1

It is part of the nervous system the is responsible for proceeding sensory information.
* Hearing *Vision *Taste/gustation *Smell *Body position and balance *Touch

The sensory system is including all the ways an organism receives information form the environment.
Receptors are neurons that are able to generate action potential according to the stimuli they respond to.

The sensory system in an ascending pathway – a nerve pathway carrying sensory information that goes
upward from the spinal cord toward the brain to be processed. Specifically, the somatosensory cortex in
the parietal lobe.

Question 2

sensory receptors

Answer 2

sensory nerves endings that respond to stimuli inside the body as well as stimuli from the environment. Receptors receive information in the form of energy like heat, touch and chemical, and transform it into electrical signals (action potential).
All sensory receptors can be classified by:
1. Structure.
2. Type of stimuli they detect.

Question 3

Structure of the sensory receptors

Answer 3

1. Free nerve endings – neurons with free dendrites at the end that extend into tissue.
   
   • Pain, heat and cold are all sensed through free
     nerve ending.
2. Encapsulated nerve endings – a free nerve ending wrapped in a round capsule of connective tissue.
   
   • When capsule is deformed by touch or pressure,
     the neuron stimulates to send signals.
3. Specialized cells – detect stimuli from the 5 special senses. Each of the special senses has its own unique sensory cells

Question 4

Photoreceptors

Answer 4

Photoreceptors are found in the eyes and respond to light by generation action potential through the optic

nerves. Photoreceptors are found in the retina and are divided into two:
* Rods – respond for black and white light. Accounts for night vision.
* Cones – respond for colorized light waves and responsible for color vision and image sharpness.

Question 5

Mechanoreceptors

Answer 5

Mechanoreceptors are those receptors that respond to mechanical stimulation. Most of them located in
the skin.
* Hair cells – the earing mechanisms of hair cells in organ of Corti. Detecting vibration.
* Meissner – detecting light touch on the skin.
* Pacinian – detecting pressure on the skin.
* Proprioception – receptors found in muscles and tendons; sending information about the location
of the limbs relativity to the main trunk.

Question 6

Thermoreceptors

Answer 6

Thermoreceptors are sensing hot or cold temperature (inside and outside of the body) relatively to the
skin. Thermoreceptors are also related to pain receptors (nocireceptors), and are able to transmit pain
sensation in extreme temperature.
Divided into two:
* Receptors that stimulated heat.
* Receptors that stimulates cold.

Question 7

Nocireceptors

Answer 7

Free nerve endings distributing all around the body, especially, in the skin area. Nocireceptors are
responding to any breach in the integrity of a tissue, swelling or trauma.

Question 8

Osmoreceptors

Answer 8

Minor the osmolality and accounts for water salt balance in the blood. They determine the body’s hydration levels.

Question 9

Chemical Receptors

Answer 9

Chemical receptors are responding to chemical stimulation. Two organs contain those receptors:

• The nose (olfactory receptors).
• The oral cavity (taste buds).

Question 10

Olfaction

Answer 10

The sense of smell. As chemical receptors in the nose and the roof of the nasal cavity are responding to
inhaled molecules, and sending their action potential through the olfactory nerve to the limbic system of
the brain.
Every receptor is sensitive to a specific smell molecule. together they combined different odors

Question 11

Taste

Answer 11

Chemical receptors found on the tongue and pharynx. Those are responding to ingested ions or molecules
to create the following tastes:
* Salt – respond mostly to sodium.
* Sweet – respond to molecules containing carbonyl functional group.
* Sour – responds to protons.
* Bitter – responds for mixture of the above.
* Umami

Question 12

Touch

Answer 12

Tactile stimuli detected by mechanoreceptors and produce the sensation of touch and pressure.

• Meissner – encapsulated nerve ending located near surface of the skin
• Pacinian – encapsulated nerve ending located in subcutaneous layer (below the skin).

Question 13

Cranial Nerve

Answer 13

The cranial nerve are nerves that emerge directly from the brain. They exchange information between the
brain and parts of the body. (Spinal nerves emerge from the spinal cord).

Question 14

12 pairs of Cranial Nerves

Answer 14

The are 12 pairs of such nerves. Two arise from the cerebrum, and ten of the brain stem.

• Olfactory – smell.
• Optic – vision.
• Oculomotor – most eye movement.
• Trochlear – eye movement too.
• Trigeminal – face sensation and mastication
• Abducens – eye movement too.
• Facial – muscles of facial expressions.
• Vestibulocochlear – hearing and balance.
• Glossopharyngeal – taste.
• Vagus – swallowing and 𝐺𝐼𝑇 function.
• Accessory – muscle of the shoulder and neck.
• hypoglossal – movement of the tongue.