Lecture 25- Endocrine System and Hormones
Key Terms.
● Homeostasis where we maintain a relatively constant internal environment that supports
optimal cell functioning and life processes
● Relies on regulatory mechanisms that control a regulated variable within a set point/range that
is considered normal/optimal for a bodily function.
● Eg. core body temperature, ion concentrations (Na+, K+, Ca2+ etc.), fluid balance,
● blood sugar levels.
● Imbalance is loss of homeostasis when our cells function and use up nutrients and produce
waste caused by growth, reproduction, exercise, stress and illness.
● Regulated variable is a variable for which there is a sensor and a system to ensure it is kept
within a normal range, around a set point.
● Examples of regulated physiological variables include:
○ Core temperature
○ Plasma glucose concentration
○ Plasma calcium concentration
○ Basal metabolic rate etc.
● Normal range is the restricted set of values for a regulated variable that permits optimal cell
functioning
● Set point is the physiological value of any given variable around which, its normal range
fluctuates/hovers around
● Each individual has a unique set point for each variable based on genetics and other factors
● Population Reference range is a set of values for a regulated variable that are considered normal
and/or healthy.
● Population Reference range tends to be wider than individual’s normal range as…
○ It’s based on test results from large groups of healthy people
○ It’s based on the breadth of individual normal ranges within the population sample
● Approx 95% of individuals will have a set point that can be found within the population reference
range
● If the variable moves outside an individual's normal range, it may lead to illness, disease or
disorder symptoms, even if the variable remains within population reference range
Charact Negative Feedback Loop (for balance) Positive Feedback Loop (for completion)
eristics
, Keeps regulated variable within its normal range, Drive a process to completion by amplifying
around its set point the change to a regulated variable
- If variable goes up, neg feedback loop brings it down - If variable goes up, pos feedback loop makes it
- If variable goes down, neg feedback loop brings it up go up more
- If variable goes down, pos feed loop makes it
go own more
-Eg. blood clot process starts and keeps going
until clot if formed (outcome achieved)
Sensors Monitor the variable and detect changes/ deviation from set point
eg. thermoreceptors that detect change in temperature eg. nerve cells erect suckling around nipple
areola
- Sends signals (action potentials or hormones) to
control center
Control Compares variable’s changed value to its set point Send signals to effectors to amplify the
Center - eg. brain cells compare 40 degrees to set point of 37 change
degrees, and - eg. pituitary gland triggers release of hormone
- Sends signals to effectors if correction is required to stimulate milk producing cells
Effector Act to oppose the effect of the stimulus, correcting Effector action amplifies the changes to drive a
s the change and restoring variable to set point process to completion
-eg. effectors produce sweat for convective heat loss and - eg. milk producing cells send milk to ducts for
dilate blood vessels for heat loss via radiation release from nipple, causing child to suckle more
(goal achieved)
Nervous System and Endocrine Systems work together to control the body and maintain
homeostasis
Nervous System Endocrine System
Functions Directs immediate responses to stimuli usually by Directs long term changes in other organ
coordinating activities of other organ systems systems with hormones/chemical messengers
- Sensory detection and interpretation - Cellular metabolism (BMR)
- Control of muscle and movement - Reproduction
- Higher function (eg thinking, speech, learning, - Growth and development
memory, emotion etc.) - Immunity and stress management
Homeostatic Breathing, core temperature, blood pressure Controlling certain concentrations in blood like
controls Ca2+ Glucose pH of plasma
Mechanism *Only communicates with things it touches *Don't have to be connected to what it controls
Neurons produce action potentials and release Targeting allowed as endocrine cells release
neurotransmitter at synapses (with neurons, muscle hormones into the bloodstream to travel to targe
or glands) cells to allow hormones to bind to specific
membrane or intracellular receptors of target
Neurotransmitter binds to chemically-gated ion cells
channels on postsynaptic cell
Speed Extremely fast signaling (within milliseconds) but Relatively slower, but longer lasting action
short lived compared to the nervous system
, Hormones
● Hormones are chemical synthesized and released by the endocrine gland cells
● Made from amino acids or cholesterol (think egg being endocrine cells that have amino acids/
protein and cholesterol to make hormones)
● They are released into the blood in response to certain stimuli and travel through blood
● They bind to specific receptors that are found either on the target cell membrane (extracellular)
or within the target cell in cytoplasm or nucleus (intracellular)
Two types of hormones:
Lipid/fat soluble hormones Water soluble hormones (COMMON)
Chemical Amines (Thyroid hormones) Amines (Catecholamines /adrenaline)
Classification Steroids eg. cortisol, testosterone, estrogen, Peptides and proteins
Synthesis and Thyroid hormones are pre made and stored All are pre made and stored until needed
storage Steroid are made as required/ not stored cuz
they diffuse easily through lipid bilayer
HOW DO THEY WORK?
1) Transport: Require and bind to carrier proteins to Don’t require carrier proteins as they travel
Hormones travel travel in the blood (eg. thyroid hormones freely in blood (eg. adrenaline released from
through blood release from thyroid glands) adrenal gland)
towards target
organs
2) Hormones - Easily diffuse across plasma membrane Cannot cross cell membranes so they bind to
bind to target (phospholipid bilayer) specific extracellular receptors on the target cell
cell receptors - Bind to specific intracellular receptors inside membrane
cell’s cytosol (cytoplasmic receptor) or
nucleus (nuclear receptor)
- Each hormone binds only to a receptor specifically designed to receive it
- Receptor is a protein in or on the target cell (cell with receptor for specific hormone)
3) Action Binding of lipid soluble hormones stimulates Binding of water soluble hormones activate a
mechanism: gene activation, transcription mRNA 2nd messenger system:
Hormones production and translation to make new - Activates G protein (attached to receptor) that
stimulate target proteins (enzymes) to produce a response activates or inhibits 2nd messengers
cells to produce a (eg. increased metabolic rate where cell (production to ⬆cAMP or breakdown to⬇ cAMP
response makes ATP faster) OR release stored CA2+ from ER or open CA2+
channels)
- 2nd messenger affect action of other proteins
like enzymes or ion channels (activate or inhibit)
- open ion channels
- start alternativE cascades
- to produce a response (eg. increased heart
rate)
Speed and - Slow Response because protein synthesis - Fast response because 2nd messenger are
Duration takes time premade and ready
- Last hours to days - Lasts milliseconds to minutes
- Small amount of hormone= big response
Key Terms.
● Homeostasis where we maintain a relatively constant internal environment that supports
optimal cell functioning and life processes
● Relies on regulatory mechanisms that control a regulated variable within a set point/range that
is considered normal/optimal for a bodily function.
● Eg. core body temperature, ion concentrations (Na+, K+, Ca2+ etc.), fluid balance,
● blood sugar levels.
● Imbalance is loss of homeostasis when our cells function and use up nutrients and produce
waste caused by growth, reproduction, exercise, stress and illness.
● Regulated variable is a variable for which there is a sensor and a system to ensure it is kept
within a normal range, around a set point.
● Examples of regulated physiological variables include:
○ Core temperature
○ Plasma glucose concentration
○ Plasma calcium concentration
○ Basal metabolic rate etc.
● Normal range is the restricted set of values for a regulated variable that permits optimal cell
functioning
● Set point is the physiological value of any given variable around which, its normal range
fluctuates/hovers around
● Each individual has a unique set point for each variable based on genetics and other factors
● Population Reference range is a set of values for a regulated variable that are considered normal
and/or healthy.
● Population Reference range tends to be wider than individual’s normal range as…
○ It’s based on test results from large groups of healthy people
○ It’s based on the breadth of individual normal ranges within the population sample
● Approx 95% of individuals will have a set point that can be found within the population reference
range
● If the variable moves outside an individual's normal range, it may lead to illness, disease or
disorder symptoms, even if the variable remains within population reference range
Charact Negative Feedback Loop (for balance) Positive Feedback Loop (for completion)
eristics
, Keeps regulated variable within its normal range, Drive a process to completion by amplifying
around its set point the change to a regulated variable
- If variable goes up, neg feedback loop brings it down - If variable goes up, pos feedback loop makes it
- If variable goes down, neg feedback loop brings it up go up more
- If variable goes down, pos feed loop makes it
go own more
-Eg. blood clot process starts and keeps going
until clot if formed (outcome achieved)
Sensors Monitor the variable and detect changes/ deviation from set point
eg. thermoreceptors that detect change in temperature eg. nerve cells erect suckling around nipple
areola
- Sends signals (action potentials or hormones) to
control center
Control Compares variable’s changed value to its set point Send signals to effectors to amplify the
Center - eg. brain cells compare 40 degrees to set point of 37 change
degrees, and - eg. pituitary gland triggers release of hormone
- Sends signals to effectors if correction is required to stimulate milk producing cells
Effector Act to oppose the effect of the stimulus, correcting Effector action amplifies the changes to drive a
s the change and restoring variable to set point process to completion
-eg. effectors produce sweat for convective heat loss and - eg. milk producing cells send milk to ducts for
dilate blood vessels for heat loss via radiation release from nipple, causing child to suckle more
(goal achieved)
Nervous System and Endocrine Systems work together to control the body and maintain
homeostasis
Nervous System Endocrine System
Functions Directs immediate responses to stimuli usually by Directs long term changes in other organ
coordinating activities of other organ systems systems with hormones/chemical messengers
- Sensory detection and interpretation - Cellular metabolism (BMR)
- Control of muscle and movement - Reproduction
- Higher function (eg thinking, speech, learning, - Growth and development
memory, emotion etc.) - Immunity and stress management
Homeostatic Breathing, core temperature, blood pressure Controlling certain concentrations in blood like
controls Ca2+ Glucose pH of plasma
Mechanism *Only communicates with things it touches *Don't have to be connected to what it controls
Neurons produce action potentials and release Targeting allowed as endocrine cells release
neurotransmitter at synapses (with neurons, muscle hormones into the bloodstream to travel to targe
or glands) cells to allow hormones to bind to specific
membrane or intracellular receptors of target
Neurotransmitter binds to chemically-gated ion cells
channels on postsynaptic cell
Speed Extremely fast signaling (within milliseconds) but Relatively slower, but longer lasting action
short lived compared to the nervous system
, Hormones
● Hormones are chemical synthesized and released by the endocrine gland cells
● Made from amino acids or cholesterol (think egg being endocrine cells that have amino acids/
protein and cholesterol to make hormones)
● They are released into the blood in response to certain stimuli and travel through blood
● They bind to specific receptors that are found either on the target cell membrane (extracellular)
or within the target cell in cytoplasm or nucleus (intracellular)
Two types of hormones:
Lipid/fat soluble hormones Water soluble hormones (COMMON)
Chemical Amines (Thyroid hormones) Amines (Catecholamines /adrenaline)
Classification Steroids eg. cortisol, testosterone, estrogen, Peptides and proteins
Synthesis and Thyroid hormones are pre made and stored All are pre made and stored until needed
storage Steroid are made as required/ not stored cuz
they diffuse easily through lipid bilayer
HOW DO THEY WORK?
1) Transport: Require and bind to carrier proteins to Don’t require carrier proteins as they travel
Hormones travel travel in the blood (eg. thyroid hormones freely in blood (eg. adrenaline released from
through blood release from thyroid glands) adrenal gland)
towards target
organs
2) Hormones - Easily diffuse across plasma membrane Cannot cross cell membranes so they bind to
bind to target (phospholipid bilayer) specific extracellular receptors on the target cell
cell receptors - Bind to specific intracellular receptors inside membrane
cell’s cytosol (cytoplasmic receptor) or
nucleus (nuclear receptor)
- Each hormone binds only to a receptor specifically designed to receive it
- Receptor is a protein in or on the target cell (cell with receptor for specific hormone)
3) Action Binding of lipid soluble hormones stimulates Binding of water soluble hormones activate a
mechanism: gene activation, transcription mRNA 2nd messenger system:
Hormones production and translation to make new - Activates G protein (attached to receptor) that
stimulate target proteins (enzymes) to produce a response activates or inhibits 2nd messengers
cells to produce a (eg. increased metabolic rate where cell (production to ⬆cAMP or breakdown to⬇ cAMP
response makes ATP faster) OR release stored CA2+ from ER or open CA2+
channels)
- 2nd messenger affect action of other proteins
like enzymes or ion channels (activate or inhibit)
- open ion channels
- start alternativE cascades
- to produce a response (eg. increased heart
rate)
Speed and - Slow Response because protein synthesis - Fast response because 2nd messenger are
Duration takes time premade and ready
- Last hours to days - Lasts milliseconds to minutes
- Small amount of hormone= big response
