all or none principle of neural transmission

Rods are responsible for black-and-white vision and can function in lower light levels than cones. Rods are mostly located along the outside of the retina while cones are clustered together in the fovea. The human eye has two types of photoreceptors - rods and cones. Photoreceptors are connected to the optic nerve through a bipolar neurone. The region of the eye containing the optic nerve is called the blind spot since there are no photoreceptors in this region so light can’t be detected. Photoreceptors detect light as it hits the retina and send nerve impulses to the brain along the optic nerve. There is an area of the retina called the fovea which contains a cluster of photoreceptor cells. Photoreceptors are receptors which detect light and are found in the retina of the eye.

Photoreceptors - receptors which detect light (e.g. Mechanoreceptors - receptors which detect pressure (see the Pacinian corpuscle below) Thermoreceptors - receptors which detect heat We contain the following receptors in our sense organs:Ĭhemoreceptors - receptors which detect chemicals it exceeds the threshold level), it will trigger an action potential (an electrical impulse) in a sensory neuron. If the change in potential difference is large enough (i.e.

When the receptor detects a stimulus, the permeability of its cell membrane changes which changes the charge difference ( potential difference) across the membrane. When a receptor is not stimulated, there is a charge difference between the inside and outside of the membrane and it is said to be polarised. Each receptor is specific to a single type of stimulus, such as light, temperature or glucose concentration. photoreceptors are cells which are sensitive to light) or proteins molecules which are found on the cell surface membrane. Receptors can either be whole cells (e.g. Our nervous system uses receptors to detect stimuli (changes in the environment) and pass on this information to the CNS. Stimulation of an effector will produce a response such as muscle contraction or hormonal release. These organs will signal to an effector (a muscle or gland) by releasing an electrical impulse along a motor neuron. Coordination centres include the brain, spinal cord and pancreas. The coordination centre receives impulses from various receptors around the body, processes the information and coordinates a response by signalling to other parts of the body. The neuron which sends an electrical impulse from the receptor within the sense organ and the coordination centre is called the sensory neuron. When receptors detect certain stimuli, they signal to the central nervous system (CNS) through initiating an electrical impulses through a neuron (nerve cell). Receptors are sensitive to a number of different aspects of our environment, such as light, pressure (touch) and chemicals in the air (smell). The nervous system detects changes in our environment (known as stimuli) through cells called receptors.

All or none principle of neural transmission