-The sense of hearing is located inside the ears. The sounds are vibrations of the air, that are received by the eardrum. The eardrum transfers this vibration to the cochlea, where some mechanoreceptors transform the vibrations into nerve impulses, that get to the brain through the auditory nerve. The sense of balance is also located inside the ear and closely related to the sense of hearing
9.6. The organization of the nervous system
The nervous system consists of the Central Nervous System (CNS) and the Peripheral Nervous System (PNS).
The Central Nervous System (CNS) consists of the brain and the spinal cord. Here, all the stimuli are evaluated and the answers are created.
The brain: is protected by the skull. It has three parts: the cerebrum (that controls the voluntary actions and the emotional and intellectual processes), the cerebellum (that controls posture and balance, and movement coordination) and the brain stem (that connects the brain to the spinal cord and controls involuntary actions such as heartbeat and body temperature)
The spinal cord is protected by the spinal column. It connects the PNS with the brain and controls reflex actions.
Peripheral Nervous System (PNS) consists of all the nerves that get into and out of the CNS.
9.6. The health of the nervous system and the sense organs
Meningitis: is an inflammation (because of an infection) of the layers that protect the brain and spinal cord (the meninges) that can lead to dead.
Multiple sclerosis: the axons of the neurosn are damaged and the transmission of the nerve impulses is reduced, which leads to paralysis.
Alzheimer’s disease: is a type of dementia caused by a loss of neurons and connections in the brain.
Parkinson’s disease: the neurons that control movement and posture die, so the patient losts the control of the muscles.
Mental disorders: they produce changes in thought, emotions and behaviour:
Phobias: irrational fears that cause anxiety
Dementia:declining brain function
Depression: a mood disorder that interferes with daily life caused by changes in the brain. IT IS NOT SADNESS. It includes mood changes, frustration, insomnia, lack of energy, pleasure doing things and hope, avoiding social interaction with other people…
Myopia: the eye becomes too long so the images cannot focus in the retina and the patient is not able to see properly distant objects. It is corrected with special lenses and glasses.
Hypermetropia: it is the oppossite of myopia. The patient does not see properly the objects that are close because the eye becomes shorter. It is also corrected with lenses and glasses (different form the ones used in myopia