Studied by 25 peopleNervous system: controls processes that happen quickly
Endocrine system: controls relatively slower processes
The two control systems of the body
Communication
Integration (information from various sources coming in to create a common desired goal)
Control
The endocrine and nervous system have three main functions that work together (or alone) to maintain homeostasis. What are the three general functions?
Hormones
Chemical messengers secreted by cells of endocrine glands; how the endocrine system communicates.
Endocrine glands
Ductless glands that secrete hormones directly into the blood
Reproduction
Growth and development
Electrolyte, water, and nutrition balance in the blood
Regulation of cellular metabolism and energy balance
Mobilization of body defenses (immune system)
What are the main processes that are controlled by hormones? [5]
Pineal gland
Pituitary gland
Thyroid gland
Parathyroid gland
Adrenal gland
What are the five main glands of the endocrine system?
Pancreas
Gonads (ovaries and testis)
Thymus
What are some organs that, in addition to their organ function, also secrete hormones? [3]
Hypothalamus
A neuroendocrine gland (has both nervous and endocrine function) that releases hormones but is also part of the nervous system.
essentially transported in water (blood and lymph)
How are hormones transmported?
How they are transported
How long they last
What receptors they act on
What does solubility of a hormone determine? [3]
how soluble the chemical is in water
What does the structure of a hormone determine?
Amino Acid based
Steroid based
What are the two broad classes of hormones?
Amino acid based hormone
Hormones that are lipid soluble and cannot cross the plasma membrane.
All hormones except for the gonadal hormones (gonads) and adrenocortical hormones (adrenal gland)
Which hormones are amino-acid based hormones?
Steroid based hormone
Hormones that are lipid soluble and can cross the plasma membrane
Gonadal and adrenocortical hormones
Which hormones are steroid-based?
Alter membrane permeability (what can get through, alters membrane potential)
Stimulate creation of enzymes or other proteins in the cell
Activate or deactivate enzymes (more of less active)
Induce secretory activity
Stimulate mitosis
What are the effects of hormones? (hormones will produce one or more of the following five effects)
Hormones are secreted by glands directly into the blood. Wherever there is blood circulating, hormones will be present
Why are hormones present in most tissues?
Target cell. the hormone will only act on cells with receptors they can bind to
Cells/tissues that have receptors for the specific hormone.
By their receptor
How are target cells identified?
Can vary depending on the target cell. Specific effect depends on target cell, makes endocrine system very complicated.
How does the effect of a given hormone vary?
Lipid soluble steroid, and thyroid: crosses plasma membrane, using intracellular receptors
water soluble: cannot cross plasma membrane, using second messenger system
What are two ways a hormone can effect a cell? How does it do what it needs to do?
Intracellular receptors
Receptors inside lipid-soluble target cells, once the hormone goes into the cytoplasm. Affects from the inside
All amino acid hormones except thyroid hormone
Which hormones use a second messenger system?
First messenger (hormone) binds to receptors on plasma membrane
Sets in place a series of events in the cytoplasm
Ultimately results in the creation of a substance called a second messenger, that has an effect inside the cell
Like a chain reaction
How does a second messenger system work? (broad) [4]
Negative feedback: Stimulus triggers hormone secretion, hormone levels rise, observable effect in target organ, feedback occurs to inhibit further hormone release.
What kind of homeostatic mechanism regulates and controls the release of hormones?
Humoral
Neural
Hormonal
Three types of stimuli that trigger hormone release by endocrine glands are:
Humoral stimulus
Refers to hormone release caused by altered levels of certain critical ions/nutrients. Means moisture of bodily fluids, presence of ions in the body.
Neural stimulus
Hormone is released by stimulus from the nervous system. Action potential stimulated a gland and hormone is released.
Hormonal stimulus
Release of a hormone stimulated by the release of another hormone. Most common type of stimulus of endocrine system. Pituitary releases hormones that stimulate thyroid, testis, adrenal cortex, etc.
Example: In times of high stress, increased levels of glucose are needed for energy (fight or flight). The nervous system overrides glucose control system to enable higher blood glucose levels. Temporary, goes back to normal once stress is over
How can nervous system have ability to override normal endocrine function?
Blood levels of the hormone (higher=greater effect)
Affinity of binding between hormone and receptor (stronger binding = greater effect)
Relative number of receptors for that hormone (more receptors=greater effect). NOT static; dynamic
The response of a targe cell depends on these three things:
If there is a consistent low level of hormone, cell will increase its number of receptors (up-regulation). If there is a consistent high level of a hormone, cell decreases its number of receptors and cell is less sensitive to that hormone (down-regulation)
Why are the number of receptors on a cell dynamic/changing?
Up-regulation
Cell increases number of receptors due to consistent low levels of a hormone (more sensitive)
Down regulation
Cell decreases number of receptors due to consistent high levels of a hormone. (less sensitive)
Removed by the kidneys (water-soluble) or metablized by the liver (lipid soluble)
How are most hormones removed from the body after having their effect?
Permissiveness
Synergism
Antagonism
Three possibilities when a cell has multiple hormones acting on the same target cell at the same time
Permissiveness
When multiple hormones act on the same taret cell at the same time and one hormone cannot exert its full effect without the presence of another hormone (ex: reproductive do not have full effect without thyroid)
Synergism
When multiple hormones have the same effect on a target cell when occurring together, Their effects are amplified. (ex: glucagon and epinephrine)
antagonism
Multiple hormones acting on the same target cell, one hormone opposes the action of another hormone (ex: insulin and glucagon). Opposite effects, will not work together.
Hypothalamus
Important role in the nervous system, also an endocrine gland. Referred to as the controller of endocrine glands. Releases hormones that are stored in the posterior pituitary, and releases hormones that inhibit activity of other endocrine glands. (ability to affect many other glands in the body
Pituitary gland
Endocrine gland that is closely related to hypothalamus, and hangs by a stalk right below it. Size of a pea, protected by sphenoid bone. 2 lobes.
Anterior pituitary: Glandular tissue, produces hormones
Posterior pituitary: Neural tissue, stores hormones that are produced in hypothalamus. Can release hormones, but they are not produced there.
Two lobes of the pituitary gland
Oxytocin (childbirth and lactation, higher in childbirth)
Antidiuretic hormone (Reduces urine production, prevents dehydration)
Two hormones released by the posterior pituitary
Tropic hormones
Hormones that regulate the action of other endocrine glands (responsible for hormone regulation and release)
Trophic hormones
What are most hormones produced by the anterior pituitary?
TSH
ACTH
FSH
LH
Four trophic hormones produced by anterior pituitary
Growth hormone (GH)
Prolactin (PRL)
Two other (non tropic) hormones produced by anterior pituitary
Thyroid gland
Largest pure endocrine gland in the body. Two lateral lobes and an isthmus on anterior neck of trachea, just inferior to larynx.
Thyroid hormone (is actually two hormones, T3 and T4)
The body’s major metabolic hormone produced by the thyroid. Controls rate at which glucose is burned and converted to body heat and chemical energy. Stimulates metabolism, tissue growth and development, maintaining blood pressure.
Calcitonin
Hormone released by the thyroid in response to a rise in blood calcium levels (no known physiological effect, does not need to be replaced in people with thyroid gland removed). When administered as a drug, decreases calcium by inhibiting osteoclast activity and stimulating calcium uptake and incorporation in to bone matrix)
Thyroid hormone
Calcitonin
Two hormones produces by the thyroid covered in this course:
4
How many parathyroid glands do most people have?
Parathyroid glands
Glands that lie on posterior surface of thyroid gland, produces PTH
Parathyroid hormone (PTH)
Hormone that is the single most important hormone in regulating blood calcium levels. Net effect is an increase in calcium levels in the blood
Adrenal glands
Glands that sit right on top of the kidney like a little had, comprised on two glands.
Adrenal medulla (inner)
Adrenal cortex (outer)
The adrenal gland is comprised of these two glands:
They produce hormones involved in stress response and electrolyte balance
What do adrenal medulla glands do?
Epinephrine
Norepinephrine
Two primary hormones produced by adrenal medulla
Hypothalamus→ medulla (reinforced fight or flight response)
Pathway for short term stress response:
triggered by the sympathetic nervous system; stressor activates
Sends signal to spinal cord, ultimately signal travels to emdulla
Fight or flight signals nerve impulse to adrenal medulla to secrete epinephrine and norepinephrine. neural stimulus
Briefly explain short term stress response[3]
cardiovascular: Increased blood pressure and heart rate, giving more blood supply to muscles. Shunts blood away from nonessential organs (norepinephrine)
Bronchodilation: bronchioles become larger, more air in lungs, more energy for muscles (epinephrine)
Metabolic: Increased glucose in the blood (epinephrine)
Effects of short term stress (epinephrine and norepinephrine) (3)
Corticosteroids (steroid hormones)
Hormones secreted by the adrenal cortex
Mineral corticoids
Glucocorticoids
Gonadocorticoids: weak sex hormones
Three main groups of corticosteroids
Mineral corticoids
Corticosteroid that regulates electrolytes (mainly sodium and potassium) in extracellular fluid
Aldosterone. Makes up 95% of mineralcorticoids secreted by adrenal cortex.
Primary mineralcorticoid that regulates sodium and potassium. Works mainly by reducing secretion of sodium in urine
Amount of sodium in extracellular fluid determines volume of extracellular fluid. Can impact blood pressure and blood volume
Why is control of sodium levels important?
Determines resting membrane potential which is essential for action potential generation.
Why is control of potassium levels important?
Glucocorticoids
Corticosteroid released by adrenal cortex that influences the energy metabolism of most cells and helps to resist stressors.
Cortisol
Main glucocorticoid in humans
When stress occurs, cortisol secretion also happens.
Prepares for stress because it increases blood glucose levels.
Causes fats and proteins to break down, and can be sued for energy, make more glucose, cell repair, etc.
Effects of cortisol on the body [3]
anti-inflammatory and auto-immune effects. These can result in:
Depressed cartilage and bone formation
Depress immune system/ inhibit inflammation
Disrupt normal cardiovascular, neural, and digestive function
Too much cortisol can lead to… [3]
Hypothalamus→ Pituitary → Adrenal cortex (HPA)
Long term stress pathway
Mineral corticoids cause kidneys to retain water, Increase blood volume blood pressure. If this is prolonged, can have serious effects:
High blood pressure
Breakdown of proteins: muscle wasting and loss
Elevated blood glucose for too long: Diabetes
Fatty acids: increased fatty acid levels in blood can lead to clogged arteries and arteriosclerosis
Renal effects of long term stress [4]
Pineal gland
Gland that secretes melatonin that regulates circadian rhythms.
Pancreas
Mixed gland located partially behind the stomach that has both exocrine and endocrine glands.
Majority of pancreas secretes digestive enzymes
Exocrine function of the pancreas
Pancreatic islet cells secrete glucagon and insulin
Endocrine function of the pancreas
Glucagon
Hyperglycemic hormone secreted by pancreas that increases blood glucose levels
Insulin
Hypoglycemic hormone secreted by pancreas that decreased blood glucose
Cells need it to survive (pathways start with glucose)
If pathways are inadequate, they cannot produce energy and cannot survive
Why is glucose important?
High glucose is sensed by pancreas
Pancreas secretes insulin
Insulin causes cells to take more glucose in, removing it from bloodstream.
Also stimulates glucose to be moved/ stored as glycogen in liver
Insulin works as second messenger
Glucose falls, blood levels back to normal
What happens if blood glucose levels get above desired range? [6]
Low glucose is sensed by pancreas
Pancreas secretes glucagon
Acts on liver, stimulating release of glucose back into the blood stream
Net effect: blood glucose rises and returns to normal
What happens if blood glucose levels fall below desired range?
Type 1 diabetes. Blood glucose keeps rising.
What happens if no insulin is secreted by the pancreas?
Gonads (ovaries and testis)
Important organs of the reproductive system that also produce hormones
Estrogen and progesterone (ovaries)
Testosterone (testis)
Hormones produced by gonads
Thymus
Endocrine gland key to immune response
Placenta
Temporary hormone organ, secretes hormones that influence the course of pregnancy
Neurotransmitters: relatively short distance
Hormones: relatively long distances
Relative distances that neurotransmitters and hormones travel
Note
Flashcard