Human Nervous and Excretory Systems

Posted on Mar 31, 2025 in Biology

The Excretory System

The excretory system is responsible for removing waste products from the body, primarily nitrogenous waste like urea and creatinine. It filters body fluids (coelomic fluid, hemolymph, blood) through specialized structures. In invertebrates, the basic unit of filtration is the nephridium, while in vertebrates, it’s the nephron.

The human urinary system has two main components:

  • Secretory Organs: The kidneys produce urine and perform other vital functions.
  • Elimination Pathway: This pathway collects and expels urine. It consists of:
    • Ureters: Carry urine from the kidneys to the bladder.
    • Urinary Bladder: Stores urine.
    • Urethra: The passageway for urine to exit the body (shorter in women than men).

The Nervous System

The nervous system, along with the endocrine system, controls the body’s functions. It receives and integrates data from sensory organs to generate responses. It also governs higher functions like memory, emotions, and volition. The nervous system is anatomically complex, and its cells lack regenerative capacity.

Divisions of the Nervous System

  • Central Nervous System (CNS):

    Consists of the brain and spinal cord. It receives stimuli, transmits impulses to processing centers, and produces effector impulses. These impulses are then transmitted to skeletal muscles.

  • Peripheral Nervous System (PNS):

    Includes cranial and spinal nerves. It transmits sensory impulses to the CNS and motor impulses to target organs.

  • Autonomic Nervous System (ANS):

    • Sympathetic Trunk: Nerve cords running along the neck, thorax, and abdomen.
    • Peripheral Ganglia: Groups of cell bodies.
    The ANS controls visceral functions, glands, the heart, blood vessels, and smooth muscle, regulating these functions according to the body’s needs.

Neuron Structure and Development

Neurons consist of a cell body, dendrites, and an axon. There are various types of neurons, each with specific functions. Nerve fibers and peripheral nerves have complex structures. Neuroglial cells support and protect neurons. Neuronal growth, survival, and differentiation involve precursor cells, cell proliferation, neural induction, cell migration, and programmed cell death during development.