Introduction. When we want to grab an object our brain gives a command and a specific muscles move the arm and the hand. This is not more complicated, but what about the lungs, heart or stomach, that are moving constantly, even when we sleep? Who gives the orders? and also what happens when without thinking we remove the hand of a place that is burning it? Who gives this order? And another topic, what happens when the function of nerves fails? And when it is our brain that fails? Can we trust what we think then? Can it be that what we see is different than reality? There are diseases that cannot consist without taking specific substances (drugs) despite that they cause damages. This topic covers all of those interesting questions.

Activities to do. Read the explanations on the effector organs and perform the first Multiple Choice Test and Connect Pictures With Names. Then read the text on the main diseases of the nervous system and perform the second Multiple Choice Test and the Crossword.

1 . The effectors. Are the organs that perform the responses of the Nervous System. There are two types of effectors, the muscles (also called "motor effectors") and exocrine glands (also called "secretory efectors"). All effectors are stimulated by nerves ie are "innervated".

The nerves are called cranial nerves if they exit from the skull or spinal nerves if they exit from the spinal cord. The set of all nerves form the Peripheral Nervous System. The motor effectors can be muscles of striated fiber and voluntary contraction or muscles of smooth fiber and involuntary contraction. The nervous system that innervates the muscles with voluntary contraction is called a Voluntary Nervous System and the nervous system that innervates involuntary contraction muscles and exocrine glands is called Autonomic Nervous System or Neurovegetative.

2 . The response of the Voluntary Nervous System. The response may be a reflex action or a voluntary action.

The reflex action. Is the one that occurs when the response is produced in the spinal cord. Its nerve coordination consists of a sensory neuron which leads a nerve impulse to the spinal gray matter, and there it is transmitted to a intercalary neuron or an association, which passes it to a motor neuron which stimulates the movement of a muscle fiber. It can also occur without the intervention of the intercalary neuron, ie with only two neurons. This is a very quick and unconscious response to the situations of danger that require an immediate response, such as when we feel a pain in the leg. The sensation of pain comes to the brain after the movement occurs. It is therefore a kind of a short circuit in the normal path of a voluntary act, in order to get a very quick response.

The voluntary action. Is the one that occurs when the response is produced in the brain. Its nerve coordination consists of a sensory neuron that connects with a spinal neuron, which connects with a neuron that goes to the brain, there several neurons are involved (association of neurons) and they emit a nerve impulse of response that goes down through the core and reaches the muscle through a motor neuron. In this case we are aware of the determined response before it is being executed.

3 . The responce of the Autonomic Nervous System. This system controls the functions performed by our organs independently of our will. For example the heartbeat, breathing, digestion, excretion, etc. It consists of some cranial nerves (exit from the skull) and some spinal nerves (exit from the spinal cord). There are two types of autonomic nervous system:

  • The sympathetic nervous system (SNS). It is in control during the dangerous situations. It causes actions appropriate for a quick response such as: increase of the heart rate, dilation of the bronchi in order to facilitate the entry and exit of gases, increase of the sweating, decrease of the intestinal peristalsis in order to reduce the energy used in digestion, vasoconstriction of the arteries, extension of the pupils in order to let in more light, etc.
  • The parasympathetic nervous system (PNS). It is in control during the situations of the rest. It causes actions appropriate for a relaxation and energetic investment in the digestive function. These actions include decrease of the heart rate, decrease of the respiration rate, decrease of the sweating, increase of the intestinal peristalsis, vasodilation of the arteries, narrowing of the pupils, etc.

The response of the autonomic nervous system is controlled by the hypothalamus but also presents reflex actions, known as visceral reflexes such as sweating and changes in muscle tension in response to localized heat or intestinal mobility in response to a stimulus.

Multiple Choice Test (Spanish activity. Activity in English is under construction)

Connect Pictures With Names (Spanish activity. Activity in English is under construction)
4 . The diseases of the nervous system. The main ones are:

Alzheimer's disease. It is a degenerative neurological disorder, progressive and irreversible, which can occur at the age of 50. The first symptoms are a severe memory loss and confusion in the speech. It causes a dementia and leads to the inability to perceive what is happening in the environment. It also may be called the "presenile dementia" since the term "senile dementia" is only used for the dementia that appears after the age of 80.

Anorexia nervosa. It is a continuous eating disorder, which consists in not wanting to eat. It usually starts with a panic sensation at the thought of getting overweight. Paradoxically this disease is stronger if the person has a strong will and is self-demanding, the two characteristics that are generally very positive for other human activities.

Autism. Is the tendency to retreat into the inner world and lose the interest in reality, accompanied by an inability to communicate. Can be a symptom of schizophrenia.

Bulimia. Is an excessive food intake in response to a state of high anxiety. The excess of weight causes the concern of the patient, thereby increasing anxiety and thus intake, closing a vicious circle.

Dependency. It involves the need to consume a specific substance, on a regular basis, in order to restore normal functioning of the body. It appears after continued use of a particular drug or medicine. It can be physical (if not consumed, may cause spasms, tremblings and sweating, called withdrawal syndrome) or mental (there is a discomfort but no real symptoms of withdrawal). Depending on the product alcoholism, smoking and drug addiction can be distinguished. The most common drugs and their effects are::

  • Cocaine (stimulant drug that produces euphoria and hyperactivity followed by a period of depression, with irritability and anxiety),
  • Heroin (numbing drug that prevents the perception of pain and helps forgetting the concerns),
  • Marijuana, hashish and LSD (hallucinogenic drugs that alter the perception of the reality we see and hear and cause unrealistic images and sounds).

Depression. It is a continuous state of profound sadness, often accompanied by anxiety, general disinterest, guilt and even impulses of self-injuring. It can be exogenous, which is natural and caused by a great misfortune and ease off after a few days, or endogenous, which is caused by an alteration of the production or reabsorption of certain neurotransmitters, and which requires several months of pharmacological treatment.

Epilepsy. It is a disorder of the brain function that causes brief, consistent attacks of the muscular convulsions, loss of consciousness and sensory disturbances.

Meningitis. It is an infection of the meninges that produces high fever, neck stiffness and acute pain.

Migraine. This disease involves repeated attacks of very strong headaches, which are usually located in the frontal and temporal area. It is often accompanied by photophobia, need for silence and sometimes vomiting.

Multiple Sclerosis. It consists in the destruction of the myelin sheath covering the axons of neurons due to an error of the patient's own immune system (autoimmune disease). Because of this the plates are scattered throughout the CNS. The first symptoms are: loss of strength, loss of sensation and difficulties in the coordination of movements.

Paranoia. It is a constant delirious feeling of being persecuted by the people around us. Paradoxically accompanied by great clarity and finesse to perceive and analyze all aspects of life that affect other people.

Parkinson's disease. It is an alteration of the grey nucleons that exist in the base of the brain, caused by the reasons still unknown. Early symptoms include hand tremblings, muscle stiffnesses and slowness of movement. It can occur from middle age.

Poliomyelitis. It is a contagious viral infection that causes paralysis and atrophy of the limbs.

Schizophrenia. It is a severe disorder of the personality, thoughts, perception of emotion and perception of the outside world. It can trigger isolated aggressive reactions.

Stress. It is a state of acute stress due to the need for responding quickly to numerous stimuli that are perceived as threatening or aggressive.

Multiple Choice Test (Spanish activity. Activity in English is under construction)

Crossword (Spanish activity. Activity in English is under construction)
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