Sensory system

Human sensory system

The kind of sensors human have

• thermoreceptors
• photoreceptors
• mechanosensors
• chemosensors

• electrosensors is not in human

All the 5 types of sensors contain protein channels.

Mechanosensor:

• Has deformed protein when subjected to pressur
• Stretch receptors
• Nerve sense the stretch of muscle cells or tendons
• Stretching of the nerve cell membrane physically opens sodium channels

 which polarizes the membrane (increase in cell voltage).

Thermoreceptor:

• In our skin (dermis), bare nerve endings sense temperature
• Snake has pit organ to response to temperature with accuracy.

Chemosensors: Two main classes> 1) Direct: taste, bood sensors 2) Distance: smell, antennae

Photosensor in eyes:

• In insects such as fly has compound eyes that its own retina in each of the lens.
• In camera-type eye in human, light goes through retina. Adjustment is made by changing the length of lens
• Human have high resolution and lower feel of motion while compound eyes are in opposite.

>How does the eye works

1) Light hits rhodopsin (protein) 2) Rhodopsin activates tranducin 3) Transducin activates phosphodiesterae (PDE) 4) PDE hydrolyzes cGMP to GMP 5) Loss of cGMP closes sodium channels 6) Causes decrease in cell voltage 7) Decrease in cell voltage is signal that goes to the brain.

Types of taste sensations: salty, sour, sweet, bitter, umami.