The 5 Senses

uman Experience is effected by both internal and external stimuli and are able to distinguish among the many different types of stimuli by means of a highly developed system of sense organs.Sensory occurs when sense organs absorb energy from a physical stimulus from the environment and the sensory receptors convert this energy into neural impulses and the which gets carried to the brain for processing..One part of the nervous systems controls the body's relationship to the environment(somatic)and another part controls the body's internal organs(Autonomic)These is called the Peripheral Nervous system that falls under the Central nervous system.Our body collects information and stimuli via the senses using the sense organs.The most familiar organs are the Eyes,Ears,Nose,Skin and Taste buds which represents each of the five senses(Sight,Hearing,Smell,Taste and Touch)Human's Sensory systems represent an integration

of the functions of the Peripheral Nervous System and the Central Nervous System.The sensory division of the Peripheral Nervous System gathers information about the Body's internal conditions(Autonomic) and external(Somatic) environment.Sensory Systems translate light,sound,temperature and other aspects of the Environment to electrical signals and transmit these signals,in the form of action potentials,to the Central Nervous System(CNS),where they are interpreted!The Brain and Spinal cord composes our Central Nervous system that acts as a clearing house.Each sensory organs are packed with sensory receptors that can respond to stimuli by producing nerve impulses in a Sensory neuron.A neuron is a cedll specialized to conduct electrochemical impulses called nerve impulses or action potentials.All neurons outside the central nervous system (and many within it) conduct impulses along hairlike cytoplasmic extensions, the nerve fibers or axons.(See diagram,Motor neuron with omitted axons)

The axons connecting your spinal cord to your foot can be as much as 1 m long (although only a few micrometers in diameter)Axons grow out of the cell body, which houses the nucleus as well as other organelles such as the endoplasmic reticulum. The length of some axons is so great that it is difficult to see how the cell body can control them. Nevertheless, there is a steady transport of materials (e.g., vesicles, mitochondria) from the cell body along the entire length of the axon. This flow is driven by kinesins moving along the many microtubules in the cytoplasm within the axon.In many neurons, nerve impulses are generated in short branched fibers called dendrites and also in the cell body. The impulses are then conducted along the axon, which usually branches several times close to its end.Many axons are covered with a glistening fatty sheath, the myelin sheath. It is the greatly-expanded plasma membrane of an accessory cell, the Schwann cell. Schwann cells are spaced at regular intervals along the axon. Their plasma membrane is wrapped around and around the axon forming the myelin sheath.Where the sheath of one Schwann cell meets that of the next, the axon is unprotected. This region, the node of Ranvier, plays an important part in the propagation of the nerve impulse.There are million of neurons in the body that does not receive impulses from other neurons.There are 3major neurons types;1)Motor neurons(responsible for muscles and glands),2)Interneurons(found in Spinal cord and brain which acts as a medium between sensory neurons and itself) and lastly the sensory neurons which are the mentioned sensory receptors that reacts directly to stimulation from the environment.Examples of stimulation include;Light,sound,motion,chemical,pressure,pain or temperature changes.Once these receptors are stimulated they transform one form of energy from the environment(eg;Light,sound)into another form of energy(action potential)that can be transmitted to other neurons.These action potentials reach the Central Nervous System.There are many kinds of receptors and they can be categorized on the basis of the types of stimuli they respond to,for eg;Mechanoreceptors(responds to movement,tension,pressure),Photoreceptors(rods and cones-respond to variations in light),chemoreceptors(responds to chemicals),Thermoreceptors(responds to temperature changes),Pain receptors(responds to Pain,tissue lacerations)The receptors converts the energy of a stimulus into electrical energy that can travel into the nervous system and inform the CNS about the conditions of the body.For eg,thermoreceptors throughout the body detect changes in the temperature,this information travels to the hypothalamus which regulates body temperature.The brain is able to decipher whether the incoming nerve impulses is sound or light by the "wiring" in the pathways of the neurons that synapses with each other,and the location in the brain where the information arrives(for eg,the occipital cortex where visuals are interpreted)The brain knows if the information received is from a sensory neuron that comes from light receptors cells when it gets the message.The 1st senses,sight/vision(the Eye)whose stimulus for vision is light (electromagnetic energy).Light can be identified by wavelength (determines color or hue) and intensity (brightness)the eye consists of the cornea which is the clear and protective layer,aqueous humor(clear liquid),the iris,which is the the color part, contains muscles that change the size of the hole for light. It adjusts to light. So it opens in dim light and narrows in bright light,the pupil which is actually a hole in the iris that lets the light in,the lenses,which is clear flexible tissue that focuses the light onto the back of the eye.It also has muscles that change it's shape to see near versus far.This ability to change shape is called accommodation

which becomes less able to change shape as we age,Vitreous humor,the clear liquid filling the eyeball,the retina,which is the layer of tissue on the back of the eye. Where the light is focused.Contains photosensitive cells,Photopigments called rhodopsin that can respond to most wavelengths of lights. Rods and cones are 2 types of photoreceptors in the retina that transduce or translate the light energy into the electrochemical messages.The fovea is the central focus area, contains the highest concentration of photosensitive cells.The optics nerve makes connections to the photosensitive cells and exits the eyeball to the brain and this is also where our "blind spots" lies where the optic nerves exits.Basically in vision,lights gets bounced off objects and gets concentrated on the back of the eye.The retina contains120 million rods in each eye: they are most sensitive in low light conditions but do not distinguish colours and are concentrated on the periphery of