Anatomy Exam 4 - Endocrine System

Endocrine System

all endocrine glands and structures containing endocrine cells in the body ; overseen by the hypothalamus

An endocrine gland…

secretes hormones into the bloodstream

Hormones

chemical messengers that regulate activities of other body cells, slow messengers, transported in the bloodstream, each hormone has a target+a function on that target

Targets

effectors, cells that respond to a specific hormone, have receptors for the hormone

Feedback

hormone levels are adjusted in the body by feedback, negative or positive feedback

Negative Feedback

a stimulus causes an endocrine organ to release hormones, the hormone helps bring body back to homeostasis, once homeostasis is achieved the hormone release stops

Hypothalamus

the hypothalamus controls endocrine system in 3 ways

1. produces hormones that regulate the anterior pituitary

2. produces hormones that are stored in posterior pituitary

3. oversees ANS so can stimulate adrenal medulla via sympathetic innervation

Pituitary gland

connected to hypothalamus via the infundibulum , divided into anterior and posterior pituitary

Posterior Pituitary Gland

contains axons from neurons in the hypothalamus , doesn’t produce hormones, stores 2 hormones (oxytocin and antidiuretic hormone/ADH)

Oxytocin OT

stored in posterior pituitary, targets reproductive organs, functions: stimulates uterine contractions during labor or menstrual cramps, stimulates breast milk ejection / release from mammary gland, stimulates smooth muscle contraction in male reproductive tract, “cuddling hormone”

Antidiuretic Hormone ADH

stored in posterior pituitary, targets kidneys and blood vessels , functions: stimulates water reabsorption in kidneys to produce more concentrated urine , stimulates vasoconstriction of arterioles (which raises blood pressure)

Endocrine system hierarchy

hypothalamus → secretes hormones that stimulate anterior pituitary → anterior pituitary secretes different hormones that stimulate effectors (thyroid, adrenal cortex, gonads)

Anterior Pituitary

if hypothalamus is the president of the endocrine system then anterior pituitary is the vice president, controlled by the hypothalamus via regulatory hormones, secretes different hormones that stimulate target organs such as Thyroid Stimulating hormone (TSH), prolactin (PRL), Adrenocorticotropic Hormone (ACTH), Growth Hormone (GH), Follicle Stimulating Hormone (FSH), Luteinizing Hormone (LH)

Thyroid Stimulating Hormone (TSH)

secreted by anterior pituitary, targets thyroid, stimulates thyroid gland to release thyroid hormone

Prolactin (PRL)

secreted by anterior pituitary, targets mammary glands, stimulates milk PROduction

Adrenocorticotropic Hormone (ACTH)

secreted by anterior pituitary, targets adrenal cortex, stimulates adrenal cortex to release its hormones called corticosteroids

Growth Hormone (GH)

secreted by anterior pituitary , targets most body cells but especially bone+skeletal muscle+adipose CT , stimulates growth

Follicle Stimulating Hormone (FSH) and Luteinizing Hormone (LH)

secreted by anterior pituitary, targets gonads (ovaries + testes)

All hormone neumonic

Oh, A flat PIg = [Oh(oxytocin) A(ADH) = stored in posterior pituitary] F(follicule stimulating hormone FSH) L(luteinizing hormone LH) A(Adrenocorticotropic Hormone ACTH) T(Thyroid stimulating hormone) Pi(prolactin PL) G(growth hormone GH)

Thyroid Gland

On anterior side of trachea, produces thyroid hormone and calcitonin

Thyroid Hormone TH

stimulated by TSH from anterior pituitary, targets virtually all cells of the body, functions: increases cellular activity (metabolic rate) and thus promotes heat production

Regulatory Hormone

Any hormone secreted by the hypothalamus to stimulate anterior pituitary to release its specific hormones

Calcitonin

secreted when blood calcium levels are high , targets bones , it lowers calcium levels in blood by inhibiting osteoclasts

Parathyroid Glands

4 tiny oval masses on posterior thyroid , secrete parathyroid hormone

Parathyroid Hormone PTH

secreted when blood calcium levels are low , targets bone , raises blood calcium levels by stimulating osteoclast activity

Adrenal Glands

right and left adrenal gland, kidneys sit on then (anterior pocket of kidneys), 2 layers (adrenal cortex which is the outer thick layer then the adrenal medulla which is the basement layer)

Adrenal Cortex

releases corticosteroids in response to andrenocorticotropic hormone from anterior pituitary , functions of corticosteroids: controls balance of sodium and potassium in body fluids, stimulates metabolism of glucose from fats+proteins , secretes small amounts of androgens which are male hormones that are converted to estrogen in women

Adrenal Medulla

stimulated by sympathetic innervation, secretes epinephrine (adrenaline) and norepinephrine (noradrenaline) , hormones that prolong the fight or flight repsonse started by sympathetic innervation

Pancreas

has exocrine and endocrine functions, pancreatic islets produce insulin and glucagon

Insulin

lowers blood sugar levels, secreted when you eat a meal, targets liver+ most other body cells, stimulates cells to pick up glucose , in liver:promotes conversion of some glucose into glycogen **ex.negative feedback when you eat and your blood glucose spikes, that alerts the pancreas to secrete insulin

Glucagon

raises blood sugar levels, targets liver, liver cells break down glucagon into glucose then release glucose into blood

Gonads

ovaries+testes, ovaries produce estrogen+proestrogen , testes produce andorgens mostly testosterone

pineal gland

secretes melatonin , circadian rhythm

Thymus

connected to the superior portion of the heart, hormones to stimulate and promote growth of T lymphocytes

Kidneys , heart , GI tract

they have hormones related to the functions of their systems