anatomy chapter 17

two major control systems in the body

nervous system and endocrine system

the nervous system uses

electrical AND chemical signaling to monitor and control

the endocrine system does NOT us electrical signals but

DOES use chemicals to control the body

the endocrine chemicals are not neurotransmitter chemical (ntc's) but are called

hormones

although there are some of the same chemicals used for both the endocrine and the nervous system (ex. epinephrine, aka adrenaline)

most hormones are different, and work differently

most hormones travel

in the blood stream FAR from where they are secreted and can affect a broad area (unlike ntc's which usually travel a tiny distance - across the synapse)

there are endocrine cells and tissues but

most are found in organs/glands

endocrine glands

the pituitary, thyroid, parathyroid, adrenal, and pancreas glands - some of the major endocrine organs

the cells with receptors for a hormone are called

target cells

some cells can have receptors for

more than one type of hormone (ex. testes could be targets for GH & FSH)

The hypothalamus and pituitary gland are

literally connected to one another

Hypothalamus

nervous tissue

pituitary gland

part nervous, part glandular

although the endocrine and nervous are two separate systems

they work together to control the body

Growth hormone

GH - from the anterior pituitary gland

Prolactin

PRL - from the anterior pituitary gland

Thyroid Stimulating Hormone

TSH - from the anterior pituitary gland

Adrenocorticotropic hormone

ACTH - from the anterior pituitary gland

Follicle Stimulating Hormone

FSH - from the anterior pituitary gland

Luteinizing hormone

LH - from the anterior pituitary gland

Antidiuretic hormone

ADH - from the posterior pituitary gland

Oxytocin

from the posterior pituitary gland

Thyroxine and Triiodothyronine

T4 & T3 - from the thyroid

Calcitonin

from the thyroid

Parathyroid hormone

PTH - from the parathyroid

Aldosterone

from the Adrenal (cortex)

Cortisol, Corticosterone, Cortisone

from the Adrenal (cortex)

Epinephrine, norepinephrine

from the adrenal (medulla)

Melatonin

from the Pineal

Insulin

from the pancreas

Glucagon

from the pancreas

Testosterone

from the testes

Estrogens and progesterone

from the ovaries

Like ntc's

hormones come in groups/families

Hormone types ("families")

Amines, Peptides, Proteins, Eicosanoids, and Steroids

example of an Amines hormone

epinephrine

example of a peptide hormone

oxytocin

example of protein hormone

insulin

example of eicosanoids hormone

prostaglandins

example of steroid hormone q

estrogen

some of the most well known hormones

testosterone and estrogen

steroids and eicosanoids are both derived (made) from

lipids/fats

steroids are derived from

cholesterol

Eicosanoids are derived from

arachidonic acid

both (steroids & eicosanoids) are

NOT soluble in water

since blood is mostly water they both (steroids & eicosanoids) must

bind to transport proteins in order to make them soluble in blood

Although lipid hormones are at a disadvantage for transport, they are at an advantage for

moving out of the blood and into the cells

since cell membranes are made of fat/lipid

hormones are able to move through them (while water soluble hormones, like proteins, can not)

water soluble proteins require what is called a

second messenger

a second messenger is

a molecule that is released inside the cell once the hormone binds to the cell

the hormone is the

1st messenger

Some second messengers

Cyclic adenosine monophosphate (cAMP), Diacylglycerol (DAG), Inositol triphosphate (IP3), Calcium/calmodulin

down regulation

when target cells decrease receptors for hormone (make them less sensitive)

upregulation

when target cell increase receptors for hormone (make them more sensitive)

"command center" of the endocrine system

hypothalamus and pituitary gland - coordinates endocrine and nervous system messages

Hypothalamus

part of the brain (diencephalon), but produces/secretes hormones

pituitary gland

connects to the hypothalamus by the infundibulum

the infundibulum is also called the

hypophysis

there are two parts (lobes) to the pituitary gland

the anterior and posterior lobes

the anterior lobe is derived from

oral (mouth) glands during embryonic development

the anterior lobe is also called the

adenohypophysis (adeno means glandular)

the posterior lobe is an

out pouching. from the Hypothalamus (nervous tissue)

the posterior lobe is also called the

neurohypophysis

the posterior lobe does not produce hormone but

two types of hormones are produced in the Hypothalamus, move down into the posterior pituitary, are stored there, and secreted later

two types of hormones produced in the Hypothalamus the go into the posterior pituitary gland

oxytocin and antidiuretic

oxytocin

OT - stimulates uterine contractions and milk ejection after birth

antidiuretic hormone

ADH

A diuretic (such as caffeine or alcohol) decreases

water reabsorption by the kidneys - thus lowers blood pressure

An antidiuretic increases

water reabsorption by the kidneys - (increasing water content in blood)

The anterior pituitary gland produces and secretes

6 different hormones

two of the hormones secreted by the anterior pituitary are lumped into

what are called gonadotropins because they (LH & FSH) both affect the gonads (sex organs)

The word Tropin/tropic refers to

a hormone that causes another gland to release a hormone

the anterior hormones are controlled by

releasing and inhibiting hormones (tropic hormones) from the hypothalamus

The hypophyseal portal system

transports hypothalamic hormones to the anterior pituitary

Portal refers to

a special blood vasculature (two capillary beds in succession)

The first capillary bed

picks up tropic hormones from the hypothalamus

the second capillary bed

"drops them off" at the anterior pituitary gland

growth hormone (GH)

"feedback"

Thyroid location

anterior to trachea and inferior to larynx (Adams apple)

isthmus

medial region - connects left and right lobes

thyroid has rings of cells that

secrete hormones into the interior space

thyroid hormones

thyroxine (T4) and triiodothyronine (T3)

iodine is taken from the blood and added to

thyroglobulin (TGB) inside the follicle

thyroglolubin is made from

tyrosine

tyrosines are "conjoined" and

secreted back into the bloodstream

after the tyrosines conjoin and secrete into the blood stream

it results in T3 and T4

T3 means

there are 3 iodine (Triiodothyronine)

T4 means

there are 4 iodine (tetraiodothyronine, better known as thyroxine)

T3 and T4 are not water soluble

so they bind to TBGs (thyroxine binding globulin) for transport in the bloodstream

Calcitonin

produced by thyroid cells that are "outside" the follicle

cells "outside" the thyroid follicle are called

parafollicular cells or c cells

calcitonin secretion is not controlled

by another (tropic) hormone

blood calcium levels are monitored directly as blood flows through the thyroid

called humoral control

calcitonin decreases

blood calcium concentrations ("tones" it down)

parathyroid glands

4-6 small glands on the posterior surface of the thyroid gland

Parathyroid hormone is part of the humoral regulation of blood calcium and will lead to

increased blood calcium concentrations (opposite of calcitonin)

adrenal glands

located on top of each kidney

adrenal glands have two

divisons (cortex - outer, medulla - inner)

adrenal cortex has

3 zones

outer most zone on the adrenal cortex

zona glomerulosa - secretes mineral corticoids (mainly aldosterone)