Biology 30 - Chapter 15

What is the endocrine system?

glands that produce hormones

Homeostasis

a constant internal environment

Function of control systems

used to maintain homeostasis

3 parts of a control system

receptor, coordinating centre, effector

2 examples of control systems

nervous system, endocrine system

nervous system uses ______ and coordinates a ________

neurotransmitters and coordinates a fast response

Hypothalamus (what is its role and what does it communicate with?)

major role in homeostasis. communicates with nervous signals (posterior), hormones (anterior)

Endocrine system uses _______ to communicate and coordinates a ________. Uses ________ to maintain homeostasis.

uses hormones to communicate. coordinates a slow response. Uses negative feedback loops.

Feedback loops

used to control the secretions from glands. There are two types, negative and positive feedback.

Negative feedback

is homeostatic, stabilizes. The response opposes or removes the stimulus and restores conditions to their original state.

General pattern

1. Hypothalamus — releases hormone

2. pituitary gland (anterior or posterior) — hormone

3. targets organ/gland

4. hormone

   (all negative feedback)

Positive feedback

not homeostatic, response reinforces the stimulus, leads to more secretions.

hormones

are chemical messengers

Endocrine hormones

are made by endocrine glands. secreted into the blood by endocrine cells. bind to receptors and triggers a cellular process.

Release of hormones is in response to…

1. nervous system signals

2. gland secretions

classification of hormones

1. active site

2. chemical nature

active site

is either target or non target

non target hormones bind to many types of cells

target hormones bind to certain cells only

Chemical nature

means what type of hormone it is, can be either water soluble or fat soluble.

water soluble hormones

made of proteins, they do NOT enter the cell. targets receptors on the cell membrane.

fat soluble hormones

called steroid hormones (made of cholesterol), pass through the cell membrane and bind to receptors in the cytoplasm. ex: estrogen

pituitary gland

It is called the master gland as it controls many glands. Two lobes: Anterior, posterior.

Anterior pituitary

signalled by hypothalamus releasing hormones

FSH (follicle stimulating hormone) — target and effect

targets the testes and ovaries. effect: stimulates follicle growth and sperm production. (anterior)

LH (luteinizing hormone) — target and effect

targets testes and ovaries. causes ovulation, formation of the corpus luteum and testosterone production. (anterior)

TSH (thyroid stimulating hormone) — target and effect

targets the thyroid, releases thyroxine. (anterior)

ACTH (adrenocorticotropic hormone) — target and effect

target adrenal cortex, release of cortisol (anterior)

prolactin

targets mammary glands, to stimulate milk production (anterior)

hGH (human growth hormone) — target and effect

targets bone, muscle and most cells. promotes bone and muscle growth (anterior)

Posterior pituitary

stimulated by the hypothalamus through nervous stimulation.

ADH (antidiuretic hormone) — target and effect

targets kidneys and increases water absorption

oxytocin — target and effect

targets uterus and mammary glands, causes contraction of uterus and secretion of milk.

4 pituitary disorders

dwarfism, gigantism, acromegaly, diabetes insipidus

Hormones that affect blood glucose levels

Insulin, glucagon, cortisol, epinephrine

controlling blood sugar levels

glucagon and insulin are hormones that regulate levels of glucose, insulin and glucagon are antagonists.

Glucagon _____ blood glucose. Insulin _____ blood glucose.

increases, decreases.

controlling blood glucose levels during stress

cortisol and epinephrine both increase blood sugar

Glands that regulate blood sugar

pancreas and adrenals

hormone producing cells (from the pancreas)

are called islets of langerhans. There are two types: beta cells and alpha cells.

beta cells

release insulin in response to high blood glucose

Insulin

lowers blood sugar, enables cells to take up glucose, causes the liver to concert glucose to glycogen. (from the pancreas)

Alpha cells

release glucagon in response to low blood glucose

glucagon

raises blood sugar levels, targets the liver and signals conversion of glycogen to glucose. (from the pancreas)

Adrenal glands

located above each kidney, involved in regulating stress. has two parts: adrenal medulla, adrenal cortex.

Adrenal medulla

stimulated by sympathetic nerves - short term stress. initiates fight or flight response. releases two hormones epinephrine and norepinephrine

effects of epinephrine

increases blood sugar, breathing+ heart rate, blood pressure and vasodilation. pupils dilate. Glycogen is converted to glucose. digestion slows.

adrenal cortex

stimulated by ACTH (which is from the anterior). stimulated during long term stress. makes three types of steroid hormones: glucocorticoids, mineralcorticoids, sex homones

Glucocorticoids

increases blood sugar levels

Mineralcorticoids

increases blood pressure. causes kidneys to increase Na+ retention (H2O follows)

Steps to target cells in kidney and muscle

1. hypothalamus sends a releasing hormone

2. anterior pituitary releases ACTH

3. ACTH targets the cells in the adrenal cortex

4. adrenal cortex cells respond by secreting glucocorticoids and mineralcorticoids into the blood which then target cells in kidney and muscle.

short term stress

nervous stimulation of the medulla, release of epinephrine

long term stress

hormones stimulating the adrenal cortex. release of cortisol

metabolism

chemical reactions that occur within a cell to support and sustain its life.

hormones that affect metabolism

There are 5:

• triiodothyronine (T3)

• thyroxine (T4)

• calcitonin

• parathyroid hormone

• human growth hormone

Glands that affects metabolism

thyroid, parathyroid, anterior pituitary

thyroid gland

located at the front of the neck. regulated rate of cellular respiration, temperature, weight, calcium levels in the blood. produces the hormones T3, T4, calcitonin.

T3 and T4

increases the rate fats, proteins and glucose are metabolized. and increases the rate of cellular respiration and mitosis. T3 regulates the amounts and activity of serotonin and norepinephrine.

T3 and T4 negative feedback steps

1. receptors in the hypothalamus detect low levels of T3 and T4

2. hypothalamus releases TRH (thyroid releasing hormone)

3. TRH stimulates pituitary to release TSH

4. TSH stimulates the thyroid to release T3 and T4

calcium metabolism

important for nerve conduction and muscle contraction. involves two glands working together to maintain homeostasis: thyroid and parathyroid gland.

Thyroid gland

releases calcitonin to lower blood calcium levels

calcitonin

causes PTH to be inhibited, bones to deposit calcium, intestines and kidneys to reabsorb Ca2+.

parathyroid glands

releases parathyroid hormone (PTH) to raise blood calcium.

PTH (parathyroid hormone)

causes calcitonin to be inhibited, kidneys and intestines to absorb more calcium, stored calcium in the bones to be released.

PTH and calcitonin are ______

antagonists, together they maintain homeostatic levels of blood calcium.

Fat metabolism

regulated by the anterior pituitary gland.

human growth hormone

affects most body cells, increases protein synthesis. stimulates cell division, growth of cartilage and bone, muscle elongation, fat metabolism— increasing blood glucose levels.

decline of hGH

results in decreased cell repair, muscle being replaced by fat.

water output

urine output must be reduced

water balance

maintains homeostasis and blood pressure

hormones affecting water balance

ADH (antidiuretic hormone)

ADH

made by the hypothalamus, stored in the posterior pituitary. targets the nephron and causes an increase in water absorption. released in response to water loss and decreases the volume of water in urine.

Water loss (steps)

1. hypothalamus stimulates the posterior pituitary to release ADH and thirst.

2. ADH targets the nephron increasing water reabsorption

Ion (Na+) loss

often caused by sweating urination or blood loss.

ion balance

is important for maintaining homeostasis, proper nerve function and maintaining blood pressure (note to self, Gillis said to only remember one)

Aldosterone

made by the adrenal cortex, causes nephron (kidney) to increase sodium reabsorption. released in response to low blood pressure

Ion loss steps

1. low bp detected by receptors in the juxtaglomerular apparatus

2. cells release renin into the blood

3. renin converts angiotensinogen to angiotensin'

4. angiotensin constricts blood vessels (increasing bp), and stimulates the release of aldosterone from the adrenal cortex

5. Aldosterone increases Na+ absorption

6. increase in blood volume

Adjustments to stress

both the nervous system and endocrine system enable the body to cope with stress

stress hormones

help respond to stressful situations. examples: epinephrine, cortisol, aldosterone, prostaglandins

epinephrine

increases breathing rate and heart rate, raises blood sugar levels by causing the release of glucagon.

cortisol

raises blood sugar levels by promoting the breakdown of proteins in the liver. reduces inflammation by suppressing the immune system.

aldosterone

increases blood pressure

prostaglandins

stimulate inflammation, increases blood flow to the area. acts locally DOES NOT TRAVEL in the blood.

problems with prolonged stress

high blood sugar, increased blood pressure, increased heart rate

exercise

is a form of short term stress. activates the sympathetic nervous system. epinephrine is released.

Anabolic steroids (chemically enhanced sports performance)

designed to mimic testosterone, provide more lean muscle mass. can cause reduced height and mood swings.

beta blockers (chemically enhanced sports performance)

slows heart rate

EPO erythropoietin (chemically enhanced sports performance)

increase red blood cell production (therefore O2 delivery)

hGH (chemically enhanced sports performance)

decreases fat and promotes muscle growth

endocrine disorders

are caused by hyposecretion or hypersecretion of a hormone from a gland. disrupts normal homeostatic conditions

pancreas disorders

hypoglycemia and diabetes

hypoglycemia

is low blood sugar, too much insulin. makes person light headed and hungry. treatment is eating small meals frequently.

diabetes mellitus

insufficient production of insulin. individuals have hyperglycemia. There are three types: type 1, 2, gestational.

type 1 (juvenile onset)

islets don’t function at all. treated with insulin pump

type 2 (adult onset)

pancreas does not produce enough insulin. treated with diet and exercise and insulin injections.

gestational

occurs during pregnancy

symptoms of diabetes

hyperglycemia (high blood sugar), tired and weak, frequent urination,excessive thirst

islet transplants (diabetic treatment)

it involves transplanting islet cells from donors into liver

adrenal gland disorders

cushings, addisons

cushing syndrome

caused by an adrenal or pituitary tumor. effect: hypersecretion of mineralcorticoids and glucocorticoids. symptoms: high blood pressure, muscle wasting in limbs

addisons disease

caused by an underactive adrenal cortex. causes low blood pressure

thyroid disorders

hyper/hypothyroidism, goiter, cretinism