The Brain and Endocrine System
The Brain
The brain, or telencephalon, is the superior part of the central nervous system. It is divided into three parts: the mesencephalon, the protuberance, and the bulb rachidian.
Within this group, we find the thalamus, hypothalamus, and pituitary gland. The pituitary gland is the smallest gland in the body and handles the endocrine system. It secretes hormones that signal to the entire body.
The thalamus, hypothalamus, and pituitary gland are located in the center of the brain.
The Meninges
The meninges are the membranes that cover the brain. They are divided into three layers: the dura mater, the pia mater, and the arachnoid mater.
The dura mater is the outermost layer and is attached to the skull. The pia mater is the innermost layer and is attached to the brain. The arachnoid mater is the middle layer and is filled with cerebrospinal fluid.
The Spinal Cord
The spinal cord is the continuation of the brain stem. It runs through the vertebrae and regulates body temperature.
The Cerebellum
The cerebellum is located at the back of the brain and is responsible for balance and coordination.
Types of Neurons
There are three types of neurons: sensory, motor, and interneurons.
- Sensory neurons identify and collect sensations (cold, heat, etc.).
- Motor neurons respond to stimuli and cause movement.
- Interneurons connect sensory and motor neurons.
The Pituitary Gland
The pituitary gland is located at the base of the brain. It secretes hormones that regulate growth, metabolism, and reproduction.
- Growth hormone (GH) stimulates growth throughout the body.
- Prolactin stimulates milk production in the breasts.
- Luteinizing hormone (LH) and follicle-stimulating hormone (FSH) act on the ovaries and testes to produce sex hormones.
- Adrenocorticotropic hormone (ACTH) stimulates the adrenal glands to produce hormones.
- Thyroid-stimulating hormone (TSH) stimulates the thyroid gland to produce hormones.
- Melanocyte-stimulating hormone (MSH) stimulates the production of melanin, the pigment that gives skin its color.
The Posterior Pituitary Gland
The posterior pituitary gland secretes two hormones: antidiuretic hormone (ADH) and oxytocin.
- ADH acts on the kidneys to regulate water balance.
- Oxytocin causes muscle contractions in the uterus and breasts.
Direct and Indirect Action of Hormones
Hormones can have either a direct or indirect action on their target cells.
- Direct action hormones bind to receptors on the target cells and cause a response.
- Indirect action hormones bind to receptors on other cells, which then release a second messenger that causes a response in the target cells.
Hypothyroidism
Hypothyroidism is a condition in which the thyroid gland does not produce enough thyroid hormones. This can lead to a variety of symptoms, including fatigue, weight gain, and constipation.
Hyperthyroidism
Hyperthyroidism is a condition in which the thyroid gland produces too much thyroid hormones. This can lead to a variety of symptoms, including weight loss, anxiety, and heart palpitations.
The Pancreas
The pancreas is an organ that produces both hormones and digestive enzymes. The hormones produced by the pancreas include insulin and glucagon.
- Insulin lowers blood glucose levels.
- Glucagon raises blood glucose levels.
The Adrenal Glands
The adrenal glands are located on top of the kidneys. They produce a variety of hormones, including cortisol, adrenaline, and aldosterone.
- Cortisol regulates metabolism and the immune system.
- Adrenaline prepares the body for fight or flight.
- Aldosterone regulates blood pressure.
The Reproductive System
The reproductive system is responsible for producing offspring. In males, the reproductive system includes the testes, which produce sperm. In females, the reproductive system includes the ovaries, which produce eggs.
Mitosis and Meiosis
- Mitosis is the process of cell division that produces two identical daughter cells.
- Meiosis is the process of cell division that produces four haploid daughter cells. Haploid cells have half the number of chromosomes as diploid cells.
Endocrinology
Endocrinology is the medical specialty that studies the endocrine system. Endocrinologists diagnose and treat disorders of the endocrine system.