Homeostasis, nervous system, brain and eyes GapFill

 HyperopiaHomeostasisMyopiaNeurologyHomologyThermoregulation is the control of the internal environment of either the body or a cell, so that optimum conditions are controlled. Examples of systems controlled by this mechanism include the amount of water in the body, the temperature of the body, and the blood  cellATPantibodystarchglucosehaemoglobin concentration. Either nervous or  muscularreceptorgenetichormonalcontrolsexual systems are used to control these levels, and all include a  stimulusglandhormonemuscledetectorreceptor, a coordination centre and an effector.

The human body must work within a very narrow temperature range, as beyond these temperature ranges,  cellscell membranesthe lungsmusclesgenesenzymes are not able to function. Body temperature is detected by receptors in the  pituitary glandcerebrummedullacerebellumbrain stemthermoregulatory centre of the brain. If too high, blood vessels  are blockedlengthendilateshortenare removedconstrict and the sweat glands become activated.

The nervous system is able to respond to these systems by detecting a change and passing a signal along neurones to the CNS. At the CNS, which is composed of the brain and the spinal cord, a response is coordinated. The signal for the response is passed along neurones to effectors, which might be muscles or  glandsenzymesconnective tissuehairstendonsbones.

A typical reflex arc shows this pattern, with sensory, relay and  motortransportresponsevehicleactivemessage neurones passing a signal from the receptor to the effector. The brain is not involved in a reflex arc, and the coordinator in this case is always the spinal cord. The brain controls more complex behaviours, with the cerebellum controlling  speechmemorytaste and smellfine motor controllanguagefacial recognition, and the  medullahypothalamuspituitary glandbrain stemcerebrumamygdala controlling basic functions, such as breathing and body temperature.

The eye is a sensory organ of the central nervous system. The receptor cells of the eye are found in the  irispupilcorneascleraretinaconjunctiva, with light passing through the lens. Control of the  transparencyhardnessthicknessvolumecolourflexibility of the lens is how the eye focuses on distant or near objects. In order to focus on a near object, the  irisesoptic nervesretinassclerapupilsciliary muscles contract and loosen the  pupilsretinasciliary musclesscleranervessuspensory ligaments.