Human Nervous, Musculoskeletal, and Endocrine Systems

Posted on Nov 25, 2024 in Biology

In vertebrates, the NERVOUS SYSTEM consists of:

Nervous Centers

  • Brain and spinal cord. Responsible for receiving, processing, and developing responses to sensory information.

Nerve Fibers

  • These are the axons of neurons. Responsible for getting sensory stimuli to the nerve centers and transmitting responses of the motor fibers.

Nerves

  • Made by the union of nerve fibers.

Nodal Masses

  • Clusters of neuronal bodies located along some nerve pathways.

Central Nervous System (CNS)

The CNS is constituted from a large number of neurons that are organized and establish many connections. The gray matter is made up of neuronal bodies, and the axons form the white myelin sheaths. The structure of the CNS is not completely solid; throughout its anatomy are a series of cavities called ventricles.

  • Skull: A bony structure that protects the brain, cerebellum, and bulb.
  • Spine: A series of vertebrae that protects the spinal cord.
The Brain

The brain consists of two symmetrical masses called hemispheres. In the upper part of the brain, we can clearly distinguish a groove separating the two hemispheres called the interhemispheric fissure. The contact point between the two hemispheres is a very white, dense area composed of nerve fibers called the corpus callosum. The brain area is called the cerebral cortex. We can distinguish different regions separated by small grooves called lobes. In the central part of the brain are the thalamus and hypothalamus.

  • Thalamus: Its main function is to connect the sensory and motor functions of the brain.
  • Hypothalamus: Receives information about the general state of the organism regarding the viscera and body physiology and is controlled by the vegetative nervous system.

The Reflex Action

These are neural responses coordinated and prepared in the spinal cord. They are independent of the brain.

Phases of Reflex Implementation:
  1. A receiver captures a stimulus.
  2. A sensory nerve stimulation leads to the marrow.
  3. The stimulus reaches an association neuron located in sensory nerve ganglia.
  4. The impulse passes from neuron to neuron to a motor coordination.
  5. By the efferent (motor nerve) pathway, the impulse reaches the effector organ (muscle or gland), performing the action immediately.

The Peripheral Nervous System (PNS)

The PNS is the set of nerves that connects the receiver and the effector or central nervous system.

Vegetative or Autonomic Nervous System

It consists of a set of nodes and peripheral nerves that leave the CNS. Their primary role is controlling the internal organs of the body involuntarily (e.g., contractions and gastric secretions).

The Hormonal Response Pathway

The endocrine system is formed by endocrine glands, the functional elements of which are hormones. While neurons release neurotransmitters onto another cell, endocrine glands release chemical messengers known as hormones into the bloodstream. At the base of the brain, there are small bodies where a close relationship exists between the nervous and endocrine systems (Hypothalamic-pituitary).

  • The hypothalamus is a nervous tissue near the base of the brain connected to the pituitary gland, which regulates the entire hormonal system of our body. The hypothalamus consists of a particular type of neuron: neurosecretory cells.
  • The pituitary is a small gland located at the base of the brain, below the hypothalamus, which controls it and is connected through a set of blood vessels forming the pituitary stalk.
    • Posterior Pituitary: Consists of nerve tissue, a group of neurosecretory neurons connected with the hypothalamus. Oxytocin stimulates uterine contractions during childbirth and milk secretion in the mammary glands during lactation. Vasopressin has an antidiuretic action, stimulating kidney reabsorption of water.
    • Intermediate Pituitary: Secretes MSH (melanocyte-stimulating hormone), responsible for stimulating the production of melanocytes, which give color to the skin. Consists of glandular tissue.
    • Anterior Pituitary: Consists of glandular tissue. Secretes six hormones called tropins, which act on another gland to stimulate the secretion of a different hormone.

Locomotor System

Thanks to the coordinated action of muscles and bones, we can execute the full range of movements and displacements our body can perform. Muscles develop a set of actions on the bones, which act as levers resulting in a particular movement.

Muscles

Muscles are bodies that contract under the control of nerve impulses.

  • Muscle Tissue: Composed of muscle fibers.
  • Connective Tissue: Wraps the fibers and muscle bundles. Muscle fibers are grouped to form muscle bundles, and all these bundles constitute a muscle.
  • Striated Muscle Fiber: Fast-contracting fibers under voluntary control of the CNS.
  • Smooth Muscle Fiber: Slower-contracting fibers under involuntary control of the autonomic nervous system.
  • Cardiac Muscle Fiber: The heart is composed of cardiac muscle fibers. Control is involuntary but faster than smooth muscle contraction.

Muscle Groups

We have about 400 locomotor skeletal muscles, representing approximately 40% of body weight.

Types of Muscles
  • Long or Fusiform: Spindle-shaped (e.g., quadriceps).
  • Flat: Flat and triangular, like a fan (e.g., deltoid, dorsal).
  • Orbicular: Around a body opening (e.g., orbicularis oculi muscle of the eyelids).

Tendons: The union between bone and muscles. Muscles are inserted into the bone using tendons, which are extensions of the tissue surrounding the muscle bundle.

Bones

Our skeleton is composed of hardened bodies called bones, and we have around 206. Their functions are:

  • Form a structure that acts as a housing and provides support.
  • Lever action allows the coordinated movement of various body parts.
  • Protect internal organs like the lungs or brain.
  • Serve as the main mineral deposit.
  • Some bones act as organs for blood cell production.

Bone Tissue

We distinguish two parts: an organic matrix, representing one-third of the bone, and an inorganic matrix, occupying the remaining two-thirds.

  • Organic Matrix: Composed of three different cell types and osteoid substance, mainly collagen fibers arranged in plates.
  • Inorganic Matrix: Provides bone toughness. It is an array with mineral reserves for the body, such as calcium, phosphorus, and to a lesser degree, magnesium, fluoride, or zinc.

Bone Tissue Cells

  • Osteoblasts: Large cells responsible for producing collagen sheets and other components of the osteoid substance.
  • Osteocytes: Aging osteoblasts that become surrounded by the osteoid substance they produced. They become impregnated with calcium salts (phosphates and carbonates) and contribute to bone structure.
  • Osteoclasts: Responsible for the renewal of the internal bone structure, permitting remodeling and growth.
Types of Bones

: bones: are elongate and cylindrical shape (femur ol’húmer). Bones plans: thin and tend to be fairly wide and flat (ol’omòplat skull bones). Short bones: small bones and cuboid or cylindrical (the vertebrae)

ANATOMY OF THE STRUCTURE AND OS: diaphysis: central, allargadaEpífisi. Zone of the ends, where the bone widens and participates in the joint. Metaphysis: il’epífisi zone that separates the diaphysis.

Inside the OS: Internal area: occupied by the marrow cavity. In the epiphysis, the marrow cavity corresponds to the red marrow, which are blood cells. Yellow marrow, fatty tissue traversed by blood vessels. Cortical Area: consisting of compact bone tissue lining the marrow cavity, both the red and yellow. This consists of a units called osteons. Above this layer of compact bone tissue are the periosteum, a layer of fibrous tissue and bone that covers the whole of the bear.

THE UNION BETWEEN THE BONES: THE ARTICULACIONSLa union between two or more bones called articulation. Articulation or fixed-sinartrosis: do not have mobility. We did not find elements of separation between the bones that form (joints of the bones of the skull) .- semimòbils or anfiartrosis joints. Show a certain capacity for movement, but rather limited. – Mobile joints or diartrosis: present a wide range of movements. Are those of the limbs of the body, elbow, knee or wrist. The link between the bones of the joint is given by a long fibrous bands that are ligaments.


The cerebellum: The cerebellum is located posterior to the base of the brain. Its function is the coordination of movements, maintaining balance and posture. It consists of two hemispheres, as the brain, which are called cerebellar hemispheres Locos. The gray substance is distributed to the periphery and the inside is white. THE bulb: The bulb is located in the lower brain, surrounded by the fourth ventricle. Story centers on control of respiratory and cardiovascular reflexes. The group of nerves that leave or arrive al’encèfal called cranial nerves. There are 12 pairs. Spinal Cord: Its cylindrical shape and is positioned around the spine. Is connected to the brain through the occipital hole. His journey through the interior channel of epèndima, which is filled with cerebrospinal fluid. The marrow is the way the brain senses that connects with the rest of the body. 2 nerves: sensory nerves: consisting of afferent fibers that carry information to al’encèfal. Motor nerves: eferents comprise fibers, leading order from the brain to the effector organ. The nerves that leave or arrive in the bone marrow are called spinal nerves. There are 31 pairs.