Anatomy two - chapter 17.1 - 17.3

Gap junctions, neurotransmitters, paracrines, and hormones

The body has these four principle avenues of communication from cell to cell

Gap junctions

These enable cells to pass nutrients, electrolytes, etc, from the cytoplasm of one cell to the cytoplasm of the other through pores in their plasma membrane

Paracrines

These are commonly known as local hormones

Hormones

These are chemical messengers that are transported by the bloodstream

The endocrine system

The glands, tissues, and cells that secrete hormones create this system

Endocrinology

This term refers to the study of the endocrine system

The presence or absence of ducts

This is the classical distinction between exocrine and endocrine glands

Blood capillaries

Endocrine glands have a high density of these (help carry their secretions away)

Fenestrated capillaries

This is the exact name of the type of blood capillaries found within endocrine glands (emphasizes its permeability)

Electrical impulses, neurotransmitters

The nervous system communicates by means of ________ and ___________ .

Hormones

The endocrine system communicates through __________ .

True

True or false : The nervous system releases neurotransmitters at synapses at specific target cells, while the endocrine system releases hormones into the bloodstream for general distribution.

Local / specific effects

The nervous system has these types of effects

General / widespread effects

The endocrine system has these types of effects

Nervous, endocrine

The _______ system reacted very quickly to stimuli while the _______ system reacts more slowly.

Nervous, endocrine

The _______ system stops quickly when stimuli stops while the ________ system may continue responding long after stimuli has stopped.

The nervous system

This system adapts more quickly to continual stimulation when compared to the endocrine system

True

True or false : Both the nervous system and endocrine system communicate chemically, and several chemicals function as both neurotransmitters and hormones

Neuroendocrine cells

These are cells that act like neurons in many respects, but like endocrine cells when they release their secretions

Target organs / cells

These organs or cells have receptors for a hormone and can respond to it

Enzyme

Some target organs / cells have these which convert a circulating hormone into its more active form

The hypothalamus

This brain structure regulates many primitive functions of the body ranging from water balance to sex drive

The pituitary gland

This structure carries out many of the hypothalamus's functions

The anterior and posterior pituitary

The pituitary gland is composed of these two structures

The anterior pituitary

This portion of the pituitary gland developed form a pouch that grows upward form the embryonic pharynx

The posterior pituitary

This portion of the pituitary gland developed from a bud growing downward from the brain

The hypophyseal portal system

The anterior pituitary gland is linked to the hypothalamus by a this complex of blood vessels

Primary blood capillaries within the hypothalamus, group of portal venues that travel down the stalk, and a complex of secondary capillaries within the anterior pituitary

This is a description of the hypophyseal portal system (superior to inferior)

Nervous tissue (nerve fibers and neuroglia)

The posterior pituitary is composed of this and therefore is not a true gland

Neuroendocrine cells, hypothalamus

Hormones of the posterior pituitary gland are made by ________ in the _________ .

The hypothalamo-hypophyseal tract

The axons of Neuroendocrine cells pass down the stalk and end in the posterior lobe through this tract

True

True or false : Posterior pituitary hormones are made within the hypothalamus and are stored in nerve endings located within the posterior lobe

Gonadotropin-releasing hormone, thyrotropin-releasing hormone, corticotropin-releasing hormone, growth hormone-releasing hormone, prolactin-inhibiting hormone, and somatostatin

These are the six hypothalamic hormones which regulate the anterior pituitary lobe

Oxytocin and antidiuretic hormone

These two hypothermic hormones are stored and released within the posterior pituitary

The left and right paraventricular nuclei

The hypothermic hormone oxytocin is a product of this nuclei within the hypothalamus

The supraoptic nuclei

The hypothalamic hormone antidiuretic is a product of this nuclei within the hypothalamus

Follicle-stimulating, luteinizing, thyroid-stimulating, adrenocorticotropic, prolactin, and growth hormones

These are the six main hormones produced by the anterior pituitary

Gonadotropins (FSH and LH)

The follicle-stimulating and luteinizing hormones can be categorized into this specific group

It stimulates the secretion of ovarian sex hormones within the ovaries and the production of sperm within the testes

Principle effect of the follicle-stimulating hormone

Antidiuretic hormone (ADH)

This posterior lobe hormone increases water retention by the kidneys, reduces urine volume, and helps prevent dehydration

Oxytocin (OT)

This posterior lobe hormone has a variety of functions in situations ranging from intercourse to breast-feeding

Neuroendocrine reflex

This refers to the release of posterior pituitary hormones is response to nerve signals

The hypothalamus, other regions of the brain, and target organs

the timing and amount of pituitary secretion are regulated by these...

Negative feedback inhibition

This occurs when the pituitary stimulates another endocrine gland to secrete its hormone, and that hormone feeds back to the pituitary or hypothalamus to inhibit further secretions

Growth hormones

This specific hormone is not targeted to one or a few organs but have a widespread effect on the body

Insulin-like growth factors

Growth hormones induce the liver and other tissues to secrete these...

Prolong the effects of growth hormones

This is the main function of insulin-like growth factors

Protein synthesis, lipid metabolism, carbohydrate metabolism, and electrolyte balance

These are the mechanisms of GH - IGF

They boost translation of mRNA, boost transcription of DNA, and enhance amino acid transportation into the cells

This is how growth hormones effect protein synthesis

They stimulate adipocytes to catabolize fats to release fatty acids and glycerol into the blood stream

This is how growth hormones influence lipid metabolism

Protein sparing effect

Through lipid metabolism, growth hormones create this effect which makes it unnecessary for cells to consume their own proteins

Glucose sparing effect

Through carbohydrate metabolism, growth hormones create this effect which reduces a cell's dependence on glucose so they won't compete with the brain

They promote the retention of sodium, potassium, and chloride within the kidney while also enhancing calcium absorption within the small intestine

This is how growth hormones help achieve electrolyte balance

Ghrelin

This is stimulus to growth hormone secretion which acts on the hypothalamus to produce the sensation of hunger as well as stimulate the resale of growth hormone-releasing hormones

The pineal gland

This mass of this gland rapidly regresses after the age of seven

Involution

This refers to rapid shrinkage of an organ

Melatonin

This is the main secretion of the pineal gland

Promotes sleep, directs our body's circadian rhythm, and has antioxidant / anticancer properties

These are the main functions of melatonin

The thymus

This gland plays a role within the endocrine, lymphoid, and immune system

T cells

The thymus is a site of maturation for these types of white blood cells (critically important for immune defense)

Stimulate the development of lymphoid organs and regulate development / activity of T cells

Main function of the hormones secreted by the thymus (thymopoietin, thymosin, and thymulin)

The thyroid

This is the largest adult gland to have a purely endocrine function

Isthmus

The two winglike lobes of the thyroid gland are joined together by this bridge of tissue

Thyroid follicles

Histologically, the thyroid gland is mostly composed of these sacs

Protein-rich colloid, follicular

Each thyroid follicle is filled with a __________ __________ and lined by a simple cuboidal epithelium of ________ cells.

To secrete thyroid hormones (90% thyroxine or tetraiodothyronine and 10% triiodothyronine)

This is the main function of follicular cells

To increase the metabolic rate

This is the primary effect of thyroid hormone

Calorigenic

Thyroid hormones have an ________ effect which increases heat production

Parafollicular cells

The thyroid gland also contains these cells which are commonly known as clear cells

Respond to rising levels of calcium within the blood by secreting calcitonin

This is the main function of parafollicular cells

Parathyroid gland

These glands are embedded within the posterior surface of the thyroid gland

Parathyroid hormones

The parathyroid hormones secrete this type of hormone

Regulate blood calcium levels

This is the main function of parathyroid hormones

Pituitary gland, blood

Unlike the thyroid gland, the parathyroid glands are not regulated by the __________ but they directly monitor the ___________ and secrete parathyroid hormones when calcium levels are too low

They stimulate calcium reabsorption from the bones and reduce calcium loss in the urine

These are a coupled examples of how parathyroid hormones increase blood calcium levels