The endocrine system

is made up of numerous glands that secrete hormones directly into the bloodstream. is made up of numerous glands that secrete hormones directly into the bloodstream.

Hormones

travel within the blood to target tissues, where they exert their effects it affect the growth and/or function of other target tissues or organs

pituitary gland

is the master endocrine gland located at the base of the brain, consisting of an anterior lobe, a posterior lobe, and a small middle section called the pars intermedia, which together regulate and coordinate hormone production and release throughout the body.

endocrine system

a collective group of tissues capable of secreting hormones

the hypothalamus

produces antidiuretic hormone (ADH) and oxytocin, which then travel along nerve axons to the posterior pituitary for unchanged release into the systemic circulatoin

What triggers the hypothalamus or pituitary gland to initiate hormone release?

Multiple mechanisms, such as neurotransmitters, injury and the resulting release of chemical mediators, and neuroendocrine signals provide input to the hypothalamus

The hypothalamus and pituitary act as

sensors that are constantly gauging hormone levels in the bodyand are the main regulators for most of the body's hormones

The negative feedback

mechanism is affected by environmental and body temperature, stress, nutrition, and specific body substancesA primary regulatory mechanism controlling hormone levels.

Paracrine pathway

hormones are produced in a cell, secreted, and act directly on nearby receptive cells.

Autocrine pathway

the receptor cells are also secretory cells so, in essence, the cell is able to produce the hormone and exert an effect on itself.

Endocrine pathway

hormones are produced in a cell, secreted, and travel through blood vessels to distant cells, attach to receptors, and act on that cell.

Synaptic pathway

hormones (neurotransmitters) are produced in the neuron, secreted, and travel along the axon to the synapse where they are released and taken up by a nearby neuron with the appropriate receptors to exert an effect.

Neuroendocrine pathway

hormones (neurohormones) are produced in a neuron, secreted, travel along the axon to the synapse, are released, are taken up into the vascular system, and travel to distant cells with the appropriate receptors to exert an effect.

Autonomic nervous system

heart rate, blood pressure, and respiratory rate increase; pupils dilate; and sweating increases. Blood flow is increased to the muscles, heart, and lungs in preparation of “fight or flight.”

Gastric function

is decreased to shunt blood to vital organs to shunt blood to vital organs.

Altered blood flow

decreased oxygenation to gastric tissues, and prolonged cortisol exposure may result in “stress ulcers” of the gastrointestinal tract.

Cerebral cortex

regulates cognitive activities such as intense focus, planning, attention, and persistence.

Limbic system:

regulates emotions such as fear, anxiety, anger, and excitement, and stimulates the reticular activating system

Thalamus

intensifies sensory input related to the stressor such as vision, hearing, and smell

Hypothalamus:

releases hormones to initiate the neuroendocrine response; acts on the autonomic nervous system.

Reticular activating system:

increases alertness and muscle tension and contributes to stimulation of the autonomic nervous system.

Antidiuretic hormone

SIADH

Syndrome of inappropriate antidiuretic hormone ) secretion is a condition of excessive production and release of ADH despite changes in serum osmolality and blood volume. Although ADH levels can transiently increase with certain medications and stressful stimuli, such as trauma, exposure to temperature extremes, pain conditions, surgery, or infection, the diagnosis of SIADH is typically reserved for those without such stimuli to explain excessive ADH release. The most common cause of SIADH is a tumor, somewhere in the body, which is secreting ectopic ADH.

ADH

promotes water retention by increasing the permeability of the nephrons in the kidneys. Most of the body water accumulates intracellularly and alters cell function. The CNS is most sensitive to these changes. Because water initially accumulates intracellularly, edema or fluid overload in the vascular system is uncommon. The excess circulating fluid within cells increases total body water concentration and eventually dilutes the sodium concentration in the extracellular space.