Excretory and Nervous Systems: Human Body Functions
Theme 5: The Excretory System
The excretory system includes organs responsible for eliminating waste and foreign substances. It also maintains vital signs, such as the amount of water in the organism and blood acidity.
- Liver: Eliminates products resulting from the destruction of blood hemoglobin.
- Respiratory System: Expels carbon dioxide.
- Sweat Glands: Located in the skin, they produce sweat, which cools the skin when the temperature is high.
- Urinary System: Eliminates waste products through urine.
The Urinary System
Kidneys: There are two kidneys. Each has an outer cortex, an inner medulla, and a cavity that collects urine, called the renal pelvis. Each kidney contains millions of nephrons that filter the blood. These nephrons end in collecting ducts in the renal pelvis. Each kidney has a vein (carrying blood to the heart) and an artery that receives oxygenated blood.
Urinary Tracts: These are the ducts that carry urine out of the body.
- Ureters: Two narrow tubes that end in the urinary bladder (this stores urine until it is expelled by a reflex called micturition).
- Urethra: The duct leading to the outside.
Kidney Function
Urine is formed in the nephrons and then expelled. Urine is composed of water, mineral salts, urea, and uric acid. Formation occurs in these steps:
- Glomerular Filtration: The passage of substances from the blood contained in the Malpighian glomerulus to the interior of Bowman’s capsule.
- Tubular Reabsorption: When these substances pass through the nephron tubule, they are reabsorbed and returned to the blood, except for molecules that are not reabsorbed.
Kidney Diseases
Kidney failure, nephritis, cystitis, incontinence.
Healthy Habits
Drink water and other liquids, do not eat excessive salt, avoid consuming toxic products and alcohol, exercise regularly, and maintain a healthy diet.
Theme 6: The Role of Relationships
The role of relationships is a set of processes that allow the organism to adapt to changing conditions, both external and internal, and coordinate the different parts of our body so that they act as a unit.
The Nervous System
Processes involved in the function of relationships:
- Sensory Organs: (Capture information) Eyes, nose, taste, touch, hearing.
- Send Information: The nervous system sends an order to the effector organs.
- Effector Organs: The locomotor system and the endocrine system (produces hormones).
Other Functions of the Nervous System
- Receives information from the sensory organs.
- Interprets information from the sensory organs.
- Prepares appropriate responses.
- Coordinates the functioning of our body’s organs.
- Performs mental and intellectual functions.
- Is responsible for feelings and emotions.
Neurons and the Nervous Impulse
The nervous system is formed of two parts: the cerebrospinal nervous system and the autonomic nervous system. Neurons are cells that have a part similar to other body cells, called the cell body, and then have extensions called dendrites and axons.
Types of Neurons:
- Sensory: Receptors that carry information to the most important nerves.
- Motor: Carry orders to the effectors.
- Intercalary or Association: Neurons are among the two previous types.
What is the Nervous Impulse?
Neurons have the capacity to generate a nervous impulse. When a neuron is stimulated, electrical changes occur in its membrane, arriving at the axon from the dendrites. The nervous impulse passes from one neuron to another via synapses. There is no physical contact between neurons; the impulse passes because they are very close. The small space between them is called the synaptic cleft. At the edge of the axon, there are small vesicles called neurotransmitters. When the nervous impulse arrives at the edge of the axon, the vesicles break, and the neurotransmitters are released into the synaptic cleft.