UNIT 1 THE SENSES AND NERVOUS SYSTEM 1 2 THE FUNCTION OF SENSITIVITY Through sensitivity, we respond to changes in the external environment. These changes are called stimuli. Look at these examples: • If the Sun is too bright, we respond by shading our eyes. • If we see a large rock falling towards us, we respond by moving away. • If we walk into a room and there is a bad smell, we respond by holding our nose or leaving the room. ORGANS AND SYSTEMS THAT INTERVENE IN THE RELATIONSHIP If somebody throws a ball to us, we respond by trying to catch it. In order for this to happen, various organs and systems are involved. • Sense organs capture information from the environment. Sense organs have groups of specialized cells, called receptors, which are sensitive to stimuli. • The nervous system controls the function of sensitivity. First, the nerves carry information from the sense organs to the brain. The brain receives and interprets the information and decides how we should respond, finally, the nerves carry responses from the brain to the muscles. • The locomotor system is made up of the muscular system and the skeletal system. Muscles receive orders from the brain and work with bones to make the body move. 3 INTERNAL COORDINATION Many processes are occurring inside our body at all times, for example: • The heart pumps the blood that circulates through our body. • The kidneys make the urine. • We digest the food. • In our lungs the blood is oxygenated. This is called internal coordination, and it is part of the function of sensitivity. The nervous system is responsible for internal coordination. ELEMENTS THAT INTERVENE IN INTERNAL COORDINATION ACTIVITIES 1. Look at these examples of sensitivity at work. What is the stimulus and what is the response in each case? a. You feel hot in the Sun and you move into the shade. b. You cover your ears when a loud bell rings. c. You cross the street at a zebra crossing when the light turns green. d. You eat a meal and digest the food. 4 SENSE ORGANS AND SENSES The sense organs capture information from the environment and send it to the brain through the nerves. EYES AND SIGHT The eyes are the sense organs of sight. They detect light so we can see shapes and colours, and estimate distances. The information captured by receptors in the retina travels to the brain through the optic nerve. The brain receives and interprets this information. EARS AND HEARING The ears are the sense organs of hearing. They detect sounds and their properties and where these sounds come from. The information captured by receptors in the cochlea travels to the brain through the auditory nerve. The brain receives and interprets this information. 5 SKIN AND TOUCH The skin is the sense organ of touch. It detects temperature, pain, pressure… The information captured by receptors in the skin travels to the brain through the nerves. The brain receives and interprets this information. THE TONGUE AND TASTE The tongue is the sense organ of taste. It detects different flavours. The information captured by receptors in the taste buds travels to the brain through the taste nerves. The brain receives and interprets this information. THE NOSE AND SMELL The nose is the sense organ of smell. It detects different smells in the air that we breathe. This information captured by receptors in the olfactory epithelium travels to the brain through the olfactory nerve. The brain receives and interprets this information. 6 THE NERVOUS SYSTEM The nervous system carries out the function of sensitivity. The nervous system is in charge of three important tasks: • It receives and interprets information from external and internal environments. • It gives the appropriate orders for our body to respond to stimuli. • It controls and coordinates all organs and systems in our body, for example, the ears, the heart and the digestive system. We can see these three tasks, for example, in a race: you see another runner pass you: you try to run faster; your heart rate increases. The nervous system is made up of two parts: the central nervous system and the peripheral nervous system. It is formed by only one type of tissue, nervous tissue. NEURONS Nervous tissue consists of nerve cell or neurons. These are grouped together to form nerves. Neurons have three parts: • The body, which is the widest part of the neuron, the other parts reach out from the body like branches. • Dendrites, which receive messages from the sense organs or other neurons. • The axon, which transmits messages to other neurons. 7 THE CENTRAL NERVOUS SYSTEM The central nervous system has two parts: the brain and the spinal cord. • The brain is protected by the cranium and has three parts: - The cerebrum controls voluntary actions, like running and talking. It also stores data and memories processes thoughts and controls emotions. - The cerebellum controls movement, coordination and balance. - The brainstem controls internal organ activities that we do not need to think about, for example, heart rate and breathing. • The spinal cord is a long, thin bundle of nervous tissue, protected by the spinal column. It extends from the base of the brain to the bottom of the spine, and connects the brain and the peripheral nervous system. The spinal cord produces involuntary responses, such as when we move our hand away from very hot objects. THE PERIPHERAL NERVOUS SYSTEM The peripheral nervous system consists of nerves that extend throughout the body. It connects the central nervous system to our sense organs, muscles, internal organs… There are two types of nerves: • Sensory nerves. These receive messages from receptors in the sense organs and send these messages to the central nervous system. • Motor nerves. These send orders from the central nervous system to the other organs. 8 THE MOVEMENTS If we take into account that part of the nervous system intervenes the movements can be classified into two types: voluntary or involuntary. THE VOLUNTARY MOVEMENTS Through movement, we respond to what happens in our environment. We make movements continuously many of them, like walking, jumping, chewing, we do them consciously, are voluntary movements. In this type of movements the brain participates. The process occurs in the following steps: • The sense organs pick up a stimulus and send the information to the brain through a sensitive nerve. • The brain analyzes the information and elaborates a response through the motor nerves to the muscles. • The muscles execute the order ordered by the brain performing an adequate movement. People relate numerous voluntary movements that can be classified into two types: thin and thick. • The fine movements are small and precise as those required to pick up a piece of paper that has fallen to the ground. • The thick movements are wider and less precious than fine movements, like those we do when we greet someone. THE REFLEX MOVEMENTS In addition to the movements that we make voluntarily. These are many others that we perform involuntarily, for example, if we prick ourselves 9 with a cactus in our hands without realizing it, we quickly put it down without thinking. Reflex movements are quick and involuntary. These movements are very important for our survival because they avoid accidents and dangerous situations. In the reflex movements, the brain does not intervene, but the spinal cord, which receives the information from the outside and elaborates a very rapid response. The process occurs in several steps: • An organ of the senses captures a stimulus that can be dangerous and sends the information to the spinal cord. • The marrow receives the information and orders a movement. • The order reaches the muscles through a motor nerve and the muscles perform the movement. ACTIVITIES 1. What is the difference between the dendrites and the axon? 2. Why are injuries to the brain stem especially dangerous? 3. Choose the words related to the nervous system and write sentences Cerebrum- eyes- sensory nerves- brainstem- bones- muscles- spinal cord 10 THE HEALTH OF THE NERVOUS SYSTEM To have good health means to be well from the physical, mental and social point of view. The nervous system health disorders are caused by different causes. INJURIES AND DISEASES OF THE NERVOUS SYSTEM The most common injuries that can occur are: • The spinal cord injury. It occurs when the spine that protects the medulla is broken. • The brain injuries. They occur when the skull is hit and the brain is damaged. Some of diseases of the nervous system with the highest incidence in our society are currently: • Alzeimer. It is caused by the deterioration of certain brain neurons. It begins with slight losses of memory, orientation and reasoning, which gradually worsen. • Parkinson. It is a disease that is characterized by the appearance of involuntary shaking movements produced by the reduction of muscle strength. ALCOHOL ALTERS THE FUNCTIONING OF THE BRAIN Alcohol is a very widespread substance in our society that can pose a serious risk to health. Depending on the amount of alcohol you consume, a person may experience a loss of reflexes or vision until they get drunk. Alcohol abuse leads to a chronic disease, alcoholism. 11 REST AND LEISURE To take care of the nervous system it is essential to sleep. In general it is necessary to sleep about eight hours a day. During the night our mind and body rest so that the nervous system can recover from daily activity and be able to perform the tasks of the next day. FINAL ACTIVITIES 1. In which of the following cases does the relationship function intervene? • The traffic light turns green and we cross the street • We digest food. 2. How is the internal coordination of our body? 3. What function do the receptors of the sense organs play? 4. What tasks does the nervous system carry out? 5. What is the brain? Where is it located? 6. What is a nerve formed from? What types of nerves exist? 7. Draw a picture of the central nervous system in your notebook and put the name of its parts. 12 UNIT 2 THE LOCOMOTOR SYSTEM 13 14 THE SKELETON The skeleton is formed by all the bones of the body. The skeleton is a framework that shapes our body, allow us to maintain posture, intervenes in the movement and protects delicate organs, such as the brain, spinal cord and heart. BONES AND ARTICULATIONS Bones are rigid and resistant organs that contain mineral substances such as calcium. Despite their rigid appearance, bones are living organs that grow and whose cells need nutrients. In our body we have three different types of bones: • Flat bones, like those of the skull. • Long bones, such as the femur and the fibula. • Short bones, such as vertebrae. The ends of many skeletal bones are covered with cartilage, which is a much more flexible and soft tissue than the bone tissue that forms the bones. There is also cartilage in other areas of our body, such as the nose and ears. The bones of the skeleton are joined together by the joints. The knee or shoulder are mobile joints and the bones remain joined by the ligaments. There are also joints, such as those that join the bones of the skull, which do not allow movement between the bones that form them. THE SKELETON BONES Our skeleton is made up of more than 200 bones distributed throughout the body in three areas, head, trunk and limbs. 15 • Bones of the head. In the head we have the skull bones and the bones of the face. The skull bones are flat and curved and their function is to protect the brain. • Bones of the trunk. On the trunk are the spine, ribs, sternum, clavicles, shoulder blades and pelvis. The ribs protect the heart, lungs, stomach and liver The spine is made up of 33 bones, called vertebrae. These bones protect the spinal cord. • Limbs bones. In the arms and legs we have long bones such as the femur and humerus. In the hands and feet we have small bones, the phalanges. 16 THE MUSCLES AND THE LOCOMOTOR SYSTEM THE MUSCLES The muscles are elastics organs, that is, they can stretch and shrink and then recover their shape and their previous size. The muscles are organs that bind to the bones and make them move. THE SKELETIC MUSCULATURE There are muscles that cover different organs of our body and others, the skeletal muscles, that perform the movement of the skeleton. These are attached to the bones by tendons. • Head muscles. The muscles of the head are flat. They are allows us, for example, to gesture, chew and talk. • Muscles of the trunk. On the trunk there are flat and large muscles. They allow us, for example, to rotate and bend the waist. • Muscles of the limbs. Many limb muscles are fusiform, that is, they have an elongated shape, allow us to move arms, legs, hands and feet. THE OPERATING OF THE LOCOMOTOR SYSTEM The skeletal musculature and the skeleton form the locomotor system. This system produces movement through the joint work of muscles and bones. The musculoskeletal system performs the movements ordered by the nervous system thanks to the ability of the muscles to change their size. The muscles receive orders from the brain or spinal cord through the nerves that reach them. When a muscle receives an order, it contracts, then, when the muscles relaxes, it recovers its original size and the bones return to the previous position. 17 Skeleton movement occurs thanks to its mobile joints, often, in the movement of a joint two muscles called antagonists that perform opposite movements. For example, in the elbow joint, the biceps and the triceps are antagonistic muscles. When one of them is contracted, the other is relaxed and vice versa. 18 THE HEALTH OF THE LOCOMOTOR SYSTEM The locomotor system can suffer different injuries if we do not have the proper precautions. To keep our locomotor system in good condition, it is essential to have a series of healthy habits in our daily lives. INJURIES OF THE LOCOMOTOR SYSTEM Some of the most frequent injuries of the bones, muscles and joints are: • Fractures. They are produced by the breakage of a bone, which can split or splinter. The most common treatment consists of placing a plaster or a splint that keeps the bone in the correct position until it is repaired. If the fracture is complicated, metal plates or nails can be placed. • Sprains. They occur when the ligaments become inflamed due to a twist. They are common in the ankles, knees and writs. • Muscles contractures. They consist of involuntary and sustained contraction of a muscle. They occur when excessive effort is made with a muscle or an inadequate posture is maintained for a long time. THE HEALTHY DIET When we are children and adolescents, our bones are growing and for this, calcium and phosphorus are essential, so it is important to consume foods that give us these two elements. For calcium to be fixed in the bones and thus strengthen, vitamin D is necessary. There are two ways to get this vitamin: • Exposure to the Sun. Solar radiation means we can get this vitamin. 19 • The diet. Vitamin D is present in foods such as eggs, milk and sardines. The brain needs nutrients like glucose to be able to develop its functions. In the diet you should not miss foods such as sugar, potatoes, legumes, cereals and food derived from cereals such as bread, cookies or pasta. PHYSICAL EXERCISE The physical exercise strengthens and gives elasticity to the ligaments and fortify our muscles. When we do sports, we can avoid injuries if we always perform a good warm up before starting and do stretching at the end. THE IMPORTANCE A GOOD POSITION The back is supported by the spine with the help of several muscles. Some postures cause the column and back muscles to be forced, which can cause pain. Therefore, it is important to pay attention to our position. 20 UNIT 1 REPRODUCTION 21 SEXUAL CHARACTERISTIC AND THE REPRODUCTIVE SYSTEM Sexual characteristics are the physical differences that exist between men and women. Sexual characteristics are classified into: • Primary sexual characteristic. These are the reproductive organs, also known as the genital organs, we are born with these characteristic. • Secondary characteristic. These refer to other physical differences between men and women. For example, men have facial hair, a deeper voice, more body hair and more developed muscles. Women develop breasts and have wider hips, a higher voice and less body hair. PUBERTY Puberty is the stage of life when reproductive organs become functional and secondary sexual characteristic develop. Boys and girls both go through periods of rapid growth, and they start growing body hair. Boys develop a deeper voice, and girls develop breasts. Puberty may take place between the ages of 10 and 14 in girls, and 12 and 16 in boys. However, these ages differ from person to person. Puberty also causes emotional changes. Our mood can change quickly, and we become more sensitive and self- conscious. 22 THE FEMALE REPRODUCTIVE SYSTEM The female reproductive system consists of several organs: • The ovaries contain the female sex cells, known as egg cells or ova. • The Fallopian tubes connect the ovaries to the uterus. • The uterus or womb is a hollow organ with a muscular wall. The baby develops here during pregnancy. • The vagina is a muscular tube between the uterus and the outside of the body. • The vulva is the external part of the female reproductive system. It is formed by folds of skin called labia. The vulva protects the opening of the vagina. It also protects the opening of the urethra through which urine is expelled. THE MALE REPRODUCTIVE SYSTEM The male reproductive system consists of the following organs: • The testes produce sperm, which contains the male sex cells, known as sperm cells or spermatozoa. • The sperm ducts are fine tubes that connect the testes to the urethra. • The prostate gland produces liquids which help to transport spermatozoa and provide them with nutrients. The mixture of these liquids and sperm is called semen. 23 • The urethra is a tube that transports semen to the outside of the body. The urethra also expels urine. • The penis is the organ that contains the urethra. ACTIVITIES 2. Draw a Venn diagram to compare secondary sexual characteristic in men and women. 3. Define puberty and describe the changes that take place during this stage. Are the changes different for boys and girls? Explain. 4. Name the male and the female sex cells. Then, name the organs that produce them. 5. Read and answer the question. a. Which organ expands during pregnancy? b. Which organ produces liquids that mix with sperm? 6. Classify the reproductive organs as male or female. Then, write a description of each. Prostate gland uterus Fallopian tubes sperm ducts 24 SEX CELLS AND FERTILIZATION Sex cells are an essential part of reproduction. They are produced in the reproductive system and are different in men and women. FEMALE SEX CELLS Female sex cells are called ova. These are their main characteristic: • They are found in the ovaries from birth. • They are large, round cells that can be seen with the naked eye. • They contain all the nutrients required for the development of an embryo. • They mature during puberty. MALE SEX CELLS Male sex cells are called spermatozoa. These are their main characteristic: • They are produced in the testes, starting at puberty. • They are very small and can only be seen under a microscope. • They have a small head and a long tail which they use to move. SPERMATOZOA OVOM 25 FERTILIZATION Fertilization occurs when a sperm cell joins with an egg cell. During sexual intercourse, semen is released into the woman´s vagina. The spermatozoa travel through her uterus into the Fallopian tubes. If, at the same time, ovulation takes place and an egg cell is released from one of the ovaries into the adjacent Fallopian tube, fertilization can occur. As a result of fertilization, a new cell, called a zygote, is formed. The zygote divides repeatedly into more cells, and all these new cells form an embryo. The embryo travels through the Fallopian tube to the uterus, where it attaches itself to the wall and continues to grow. ACTIVITIES 1. Complete the sentences. Write them in order to describe fertilization. a. The embryo attaches itself to the wall of the …………………… b. An egg cell is released by one of the ……………………. c. After several divisions, an ………………………… is formed. d. A sperm cell joins with an …………….. and forms a …………………. e. During sexual intercourse, ………… is released into the woman´s ………… 26 PREGNANCY, BIRTH AND LACTATION PREGNANCY Pregnancy is the period from the moment of fertilization until the birth of a baby. It lasts about nine months. Once the embryo attaches itself to the uterus, two main changes happen: • The embryo is surrounded by a sac called the amnion, which is filled with liquid and provides protection. • A new organ, called the placenta, forms inside the uterus. It provides nutrients and oxygen from the mother to the embryo. It also eliminates waste products produced by the embryo. The embryo and the placenta are connected by the umbilical cord. The initial embryo develops into a fetus, and at about three months, all the body parts can be distinguished. The fetus continues to develop and grow until it is ready to be born. 27 BIRTH Birth happens at the end of the pregnancy, when the baby comes out of the mother´s body. The process of giving birth is called labour. These are three stages during labour: • During the first stage, the involuntary muscles of the uterus contract and cause the opening of the uterus to dilate. This allows the baby to come out through the vagina. The amnion breaks and the liquid around the fetus is expelled. This is the longest stage. • During the second stage, the baby is born. The mother helps to deliver the baby by pushing hard with her abdominal muscles. • During the third stage, the placenta is expelled from the uterus through the vagina. When there are complications during labour, a doctor performs a Caesarean section to remove the baby directly from the mother´s uterus. LACTATION Lactation is the period when the mother´s breasts produce milk. It happens after giving birth. Breast milk produces all the nutrients that a baby needs to grow, and substances that protect against diseases. Breastfeeding consist of the baby feeding on its mother´s milk. This is the best way to feed a baby, but babies can also be fed artificial milk, called formula milk. 28 REPRODUCTION AND HEALTH Reproduction can only be done when the sexual organs are fully develop. THE EXPERIENCE OF PUBERTY AND ADOLESCENCE Many changes occur after puberty. Some of physical changes can be seen externally, with the growth of the beard or the breasts, nevertheless. Other of them are not seen because they are mental and emotional. Each person has their own rate of change. Often, adolescence solve their doubts by asking their friends, who has as many doubts of trained adults, such as parents or teachers, who will be willing to listen and help you. HEALTH AND HYGIENE OR SEX ORGANS Like any other part of our body, the sexual organs must be clean. The hygiene of the reproductive devices must be taken care of and see a doctor if necessary. For any discomfort, pain or irritation, consult a doctor. The doctors responsible for the health of the sexual organs are gynecologists, in the case of the female reproductive system, and urologist, in the case of the male reproductive system. THE IMPORTANCE OF PREVENTION Increasingly, preventive medicine becomes more important, that is, what is aimed at preventing the disease before it occurs or when it is in its initial stages. Periodic reviews help prevent some diseases or detect them quickly. One type of cancer that directly affects women is breast cancer. One measure of prevention is mammography, which is like an x-ray of the breast. Older men may suffer from prostate cancer, there is also evidence to detect it. 29
