The Endocrine and Nervous Systems: A Comprehensive Overview

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The Endocrine System

Hypothalamus: Produces releasing hormones, which control the activity of the pituitary gland.

Pineal Gland: Controls the daily sleep-wake cycle and produces melatonin.

Pituitary Gland: Directs the activity of other endocrine glands with a variety of hormones.

  • Gonadotropic Hormones: Act on the sex organs.
  • Oxytocin: Stimulates uterine contractions during childbirth.
  • Growth Hormones: Control the elongation of bones.

Thyroid Gland: Regulates the body's overall metabolism with thyroxine. Produces calcitonin, which increases blood calcium levels.

Adrenal Glands: Regulate metabolism with cortisol, regulate kidney function with aldosterone, and prepare the organism for high-stress situations with adrenaline.

Pancreatic Islets: Control blood glucose with two antagonistic hormones: glucagon and insulin.

Gonads: Contribute to the development of the sex organs and secondary sexual characteristics by producing sex hormones. Testes produce testosterone; ovaries produce estrogen and progesterone.


Neurons transmit messages called nerve impulses around the body. Neurons have a cell membrane, cytoplasm with a nucleus, and other organelles, giving them a unique appearance.

A nerve impulse is the electrical signal that travels rapidly through a neuron from the dendrites to the axon.

Nervous System

Central Nervous System: Comprised of the neurons within the brain and spinal cord.

Peripheral Nervous System: Comprised of all other neurons.

Autonomic Nervous System

Responsible for involuntary regulation. It is made up of two types of pathways: parasympathetic and sympathetic.

Somatic Nervous System

Responsible for sensory and motor function under conscious control. Voluntary.

Sensory Pathways

Move information from the sensory organs to the central nervous system.

Motor Pathways

Carry messages from the central nervous system to effectors.

Combined Pathways

Complete both sensory and motor functions.

Grey Matter: Formed by the cell bodies and dendrites of neurons. These are the control centers where neurological messages are processed.

White Matter: Formed by neuron axons. These are the communication cables, the connections between the control centers.

Parts of the Brain

The cerebrum is the largest part of the brain. It includes the two cerebral hemispheres, the corpus callosum, the thalamus, and the hypothalamus. The other two subdivisions are the cerebellum and the brainstem.

Reflex Arcs

In the spinal cord, synaptic transmission occurs between sensory neurons and motor neurons. This type of involuntary movement is called a reflex arc.

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