CNS recieves infomation from internal and external environments through variety of sense cells and organs called receptors, each responding to a different tye of stimulus.
Features of sensory reception as illustrated by the Pacinian Corpuscle
- is specific to a single type of stimulus - responds only to mechanical pressure. Will not respond to other stimulus, e.g. heat, light, sound
- produces a generator potential by acting as a transducer. All stimuli are forms of infomation, but not all forms that the body can understand. Role of transducer to convert infomation from stimulus into impulses ( that the body can understand ). stimulus is always some form of energy, e.g. heat, sound. The nerve impulse also form of energy. Receptors convert, or transduce one form of energy into another. All receptors conver the energy of the stimulus into a nervous impulse known as generator potential.
Structure and function of a Pacinian Corpuscle
Pacinian corpuscles respond to mechanical stimulu such as pressure. Occur in skin, most abundant in tips of fingers, soles of feet and external genitalia. Occur in joints, legaments and tendons, where they enable the organis, to know which joints are changing direction. Insgle sensory neurone of a Pacinian corpuscle is at the centre of layers of tissue surrounded by gell.
Plama membranes contain protiens, these protiens have channels along which ions can be transported, some channels are specific and only carry one ion such as sodium channel only carry sodium ions.
Sensory neurone ending at the centre of the Pacinian corpuscle has a special type of sodiu, channel in its plamsa membrane - called streetch-mediated sodium channel
these channels are so-called because their permeability to sodium changes when they change shape, e.g. by streching.
Pacinian Corpuscle functions:
In normal (resting) state, the stretch-mediated sodium channels of the membrane around the neurone of a Pacinian Corpuscle are too narrow to allow sodium ions to pass along them, In this the state, the neurone of the Pacinian corpuscle has a resting potiential
When pressure is applied to the Pacinian corpuscle, it changes shape and the membrane around its neurone becomes streteched
This stretching widens the sodium channels in the membrane and sodium ions diffuse into the neurone