Systems Physiology - Anatomy

The "little brain" is also known as the cerebellum. The Cerebellum is responsible for allowing people to maintain their posture and ability to move effectively. The occipital lobe processes visual stimuli, the medulla controls heart rate and breathing, and the flight or fight response is mediated by the amygdala.

The choroid plexus consists of modified ependymal cells and is found within the walls of the cerebral ventricles and secretes cerebrospinal fluid. Plasma is the extracellular matrix of the blood. Urine is produced by the kidneys. Lymph is the excess fluid drained from the cardiovascular system, and mixes with blood at the level of the subclavian veins.

The basal ganglia is a structure of the cerebrum that contains grey matter called the putamen, caudate nucleus, and globus pallidus. There are also two midbrain structures called the subthalamic nucleus and substantia nigra.

The brain and spinal cord are protected by special membranes called meninges. The meninges are made up of three membranes listed from superficial to deep: dura mater, arachnoid mater, and pia mater. Note that the cerebrospinal fluid circulates in the space between the arachnoid mater and the pia mater, called the subarachnoid space.

The fourth ventricle is connected to the third ventricle via the aqueduct of Sylvius (also known as the cerebral aqueduct). The third ventricle connects with the lateral ventricles through the interventricular foramina.

The face is unique in which the sensation of touch is processed through the trigeminal nerve through the trigeminal ganglion which later synapses to the chief nucleus. Don't confuse this with fasciculus gracilus, which transmits touch info from T8 and down and cuneatus that does T8 and up.

The pulmonary veins carry oxygenated blood form the lungs to the left atrium of the heart. The pulmonary arteries carry deoxygenated blood from the right ventricle to the lungs.

Both A delta and C fibers are associated with the perception of pain. This can be broken down more specifically to A delta fibers that are slightly mylinated and carry "Fast" sharp pain that is immediately felt. While C fibers carry "slow" pain due to being unmyelinated and is associated with chronic pain.

The heart secretes atrial natriuretic peptide, which acts on the kidneys. Oxytocin is secreted by the posterior pituitary. Thymosin is secreted by the thymus gland. Androgens are secreted by the adrenal cortex.

Cortisol is the only steroid hormone listed, some other examples would be estrogen and androgens. Insulin and parathyroid hormones are peptide hormones. Epinephrine is a catecholamine, which is a tyrosine derivative.

Thyroid hormone is secreted by the thyroid and plays a role in bone growth, neural maturation, and the body's basal metabolic rate. It is released in response to thyroid-stimulating hormone (TSH) from the anterior pituitary, and targets cells throughout the body. Hypothyroidism is characterized by reduced synthesis of thyroid hormones, and can present as weight gain, fatigue, and sensitivity to cold.

Cortisol, a hormone secreted by the adrenal gland, functions to maintain blood pressure by upregulating the number of alpha-1 receptors on arterioles.

Gastrin is a hormone secreted by the G cells of the stomach that acts to increase gastric acid secretion, increases the growth of gastric mucosa, increases gastric motility, and stimulates the secretion of digestive enzymes. In addition to stimulating the release of pepsinogen, gastrin stimulates the pancreas to release digestive enzymes. Bicarbonate, however, is not an enzyme and is stimulated by another hormone.

Secretin is a hormone secreted by the S cells in the duodenum that acts to increase pancreatic bicarbonate secretion and decrease gastric acid secretion.

Remember that hormones are generally slow-acting in the body. Glands will respond to the conditions of the body by elevating hormones in a negative feedback fashion. If a person has high blood glucose levels, it is expected that the body is going to increase hormones that act to lower the blood glucose levels.

Insulin is responsible for stimulating glucose sequestration for use in cell metabolism or storage in the liver as glycogen. As a result, insulin levels would be elevated in a person with high blood sugar levels.

Glucagon is functional antagonist of insulin, and serves to elevate blood glucose levels through glycogenolysis and gluconeogenesis. Cortisol is released by the adrenal cortex in response to adrenocorticotropic hormone (ACTH) and long-term stressors, such as prolonged hunger, thirst, and heat/cold exposure. Thyroxine (T4) is a thyroid hormone that mediates basal metabolic rate and is released in response to thyroid-stimulating hormone (TSH).

While testosterone is associated with the growth spurt during puberty, it is also responsible for the closing of the epiphyseal plates on long bones. This process helps stop the growth in length of the body.

Testosterone is the primary male sex hormone and is secreted by Leydig cells of the testes. Testosterone is a steroid hormone, meaning it can enter cells and act directly on DNA as a transcription factor. In this way, it mediates the production of sperm, anatomical growth, and development of secondary sex characteristics in males.

Hypersecretion, or oversecretion, of the growth hormone during childhood can typically result in gigantism. The person will be very tall and have normal face and body proportions; the growth plates are still present at this time and they all receive a larger amount of the hormone.

Dwarfism would be a result of hyposecretion, or undersecretion, of growth hormone during childhood.

Acromegaly is caused by hypersecretion of growth hormone, but during adulthood as opposed to childhood.

Erythropoietin acts on red bone marrow to increase the amount of red blood cells being produced. Aldosterone is responsible for electrolyte homeostasis via the excretory system. Cortisol is the hormone associated with stress response, and regulates blood glucose levels. Lastly, prolactin is responsible for milk production.

Vasopressin, also known as antidiuretic hormone, is released by the posterior pituitary and targets the kidney for water reabsorption. Milk production is controlled by prolactin. Milk ejection is an effect of oxytocin. Lastly, the thymosin and thymopoietin are responsible for lymphocyte development.

ADH inserts special channels into the collecting ducts of the kidney that allow for water absorption from the fluid that is destined to become urine. An increasing amount of ADH would decrease the amount of urine voided from a person as more water is being absorbed in the distal convoluted tubule and collecting ducts of the kidneys. ADH also constricts arterioles everywhere in the body, which increases the peripheral resistance and arterial pressure.

Erythropoietin is a glycoprotein that increases the production of red blood cells. Erythropoietin is secreted by the kidneys and liver, and activates red bone marrow to induce hematopoiesis.

Oxytocin has many effects in the body. First, it stimulates contraction of the myoepithelial cells which surround mammary alveoli in the mammary gland. This causes milk to be ejected. Oxytocin is also released during labor and works to enhance uterine contractions in order to facilitate birth. Lastly, oxytocin is widely known as the "bonding hormone," and studies show that its presence establishes maternal behavior. Oxytocin does not, however, form and regulate the female reproductive system; this is done by the female sex hormone, estrogen.