Title:
URL Source: blob://pdf/81f05b77-5fed-4ac0-b942-7cd9f7d3172d
Markdown Content:
1
# Unit 4:
# Homeostasis 2
# Homework Guidelines for the Homeostasis Unit
Since you are receiving the notes for this unit, your major responsibility will not be to
make notes but instead to pre -read them along with the textbook and then answer
assigned homework questions. These homework questions will test how well you have
pre -read the notes , paid attention, and participated during class, and did a bit of extra
research.
The questions will have to be completed and submitted at the very start of the
assigned classes. It is expected that answers are written in full sentences and include
detail that would allow the reader to know what the question was asking. All answers
will be marked for accuracy, detail, and proper spelling and sentence structure.
Late submission of these homework questions will not be accepted. Copied or
otherwise plagiarized work (includ ing work copied from classmates ) will not be
acc epted . So, it is imperative that you work through these questions on your own.
Homework Questions:
Section Questions (marks)
8.1 (p.348)
#2 (6A )4 -7 sentences
#9 (2 A)3 -6 sentences
#10 (5 I)4-7 sentences
8.2 (p.362) #9 (5 I)4 -7 sentences
#11 (2 I)3 -5 sentences
9.1 (p.395) #3 (3 I) 4 -7 sentences
#11 (2 I)3 -5 sentences
9.2 (p.403) #6 (2 A)3 -6 sentences
#10 (2 I)3 -6 sentences
9.3 (p.413) #4 (3 A)4 -7 sentences
#9 (8 A)8 -11 sentences
9.4 (p.425) #6 (2 I)3 -6 sentences
#11 (2 I)3 -5 sentences
10.1 (p.448) #5 (2I )3 -5 sentences
#10 (2 I)2 -4 sentences
10.2 (p.455) #10 (4 A)6 -9 sentences
#11 (2 I)3 -5 sentences
10.3 (p.465) #4 (3A )3 -5 sentences
#5 (4 I)4 -6 sentences
TOTAL 33I and 28A
# The marks for this work will be tallied and the
# total will be counted towards your marks .3
# 8.1: Human Body Systems and Homeostasis
# (p.344 -348)
Learning Goals:
Explain the purpose of homeostasis with respect to survival.
Discuss negative and positive feedback systems.
Discuss different body systems with respect to their role in survival.
Body systems are important for survival as they each perform a vital role in the
body. All body systems work together in order to maintain and control all the
necessary functions for life.
Examples of body syste ms that assist in maintaining homeostasis:
Circulatory system : transport materials throughout the body (nutrients,
hormones, waste, oxygen, )
Immune system : protects the body against disease and foreign substances
Digestive systems : breaks down food and a bsorbs its nutrients
Respiratory systems : takes in oxygen and releases carbon dioxide
Excretory system : removes waste material from the bloodstream, regulates
blood pH, and fluid levels in the body
Nervous system : allows the body to respond to external and internal stimuli
Endocrine system : secrete chemicals (ex. hormones) to body functions
Other systems include reproductive , integumentary , lymphatic ,
muscular , and skeletal .
Homeostasis is the maintenance of a stable internal environment within an
organism, regardless of internal or external stresses or conditions . This
stability is achieved by internal regulatory mechanisms countering the effects of
external forces that would change conditions is known as dynamic
equilibrium . Large external fluct uations will only lead to small internal
fluctuations. 4
Why must homeostasis be maintained?
so organs and organ systems can function optimally
allows for responses to constant stresses and stimuli encountered by living
things
allows life to continue
# LACK OF HOMEOSTASIS = DEATH
Feedback Systems
Feedback systems allow organisms to constantly monitor themselves for
changes and then mak e appropriate adjustments to maintain homeostasis.
The steps to any feedback system involves the following:
stimulus receptor /sensor regulatory /control center effector response 5
Negative Feedback (most common)
stimulus produces a reaction reducing the stimulus or its effects.
e.g. iris control
stimulus is intense light
receptors are the eye
regulatory center is the brain
effector is the iris of the eye
response is that the pupils constrict to reduce light
feedback is closing pupils which the original stimulus
e.g. temperature control
stimulus is cold temperature
receptors are the skin and many other organs
regulatory center is the brain
effector are the muscles, bl ood vessels, and others
response is that muscles shiver, blood vessels constrict
feedback is heat generation, loss prevention which the original
stimulus
Positive Feedback (least common)
The stimulus produces a reaction increasing the stimulus or its effects.
e.g. childbirth (uterine contractions stimulated by the hormone oxytocin)
baby's head pushes against cervix
impulses from the cervix send a mes sage to the brain
brain tells pituitary gland to release oxytocin
oxytocin stimulates uterine contraction
pushes baby's head farther into the uterine opening
more oxytocin is released & a stronger contraction occurs
e.g. blood clotting control
stimulus is platelets collecting at a site of a cut
receptors are the platelets that release chemicals
regulatory center is the brain
effector is the other platelets
response is that more platelets go to the clotting site
feedback is more platelets which increases the original stimulus
Success Criteria :
I can to e xplain the purpose of homeostasis with respect to survival.
I can d iscuss negative and positive feedback systems.
I can d iscuss different body systems with respect to their role in
survival. 6
# 8.2: Structures and Processes of the Nervous
# System (p. 349 -362 )
Learning Goals:
Discuss the parts and function of the nervous system.
Be able to draw and label a neuron.
Discuss the roles of a neuron, its parts, and glial cells.
What is a reflex arc, give examples, and how is it different from other
nervous system reactions?
Discuss (in writing and with diagrams) the steps of neuron action and
the factors that affect it.
Explain how the message from one neuron is passed to the next
neuron.
# The Nervous System
The nervous system provides a high -speed communication system to and
from almost every part of the body. A series of sensory receptors (ex. eye)
provides information about changes in the external/internal environment
that may affect the bodys responses.
Nervous Sys tem
The nervous system can be broken down into two key parts:
o Central Nervous System (CNS) brain and spinal cord
o Peripheral Nervous System (PNS) nerves that lead into/out of the
CNS
PNS
The PNS consists of two parts:
o Autonomic Nervous System not consciously controlled
o Somatic Nervous System consciously controlled
Autonomic Nervous System
The autonomic nervous system consists of two parts:
o Sympathetic fight or flight responses
o Parasympathetic resting responses 7
Nervous System Summary
# How the Neuron Works
The nervous system is composed of specialized cells called neurons .
Neurons are specialized for the transmission of information at rapid rates.
Maintenance of homeostasis depends on this transmission and response.
Glial cells are the cells that are associated with neuron cells. Their job is
to support the needs of the neur on (waste removal, feeding, ) so that
the neuron can solely focus on conducting messages. An example of a
glial cell is the Schwann cell.
Nerves
Numerous neurons held together by connective tissue.
90% of the bodys neurons are found in the CNS.
Sensory Neurons carry impulses from the bodys sense organs to the
CNS
Motor Ne urons transmit commands from the CNS to the muscles
Interneurons nerves that link sensory and motor nerves 8
A neuron consists of the following basic parts:
Dendrites th read -like projections that pick up information from other
neurons
Cell Body /Soma contains nucleus and other cell organelles necessary
for proper cell functioning in signal interpretation
Axon long stalk through which impulse travels
Myelin Sheath some neurons possess a fatty covering over the axon
which allows impulse to be transmitted much faster
Schwann Cells present in myelinated neurons
they are cells which produce myelin
specialized n eurological cells which provide
nutrients for neurons
Types of Neurons :
Sensory Neurons receptors; detect change in the environment
Interneurons connect sensory neurons to motor neurons
Motor Neurons activate muscles and glands 9
# Reflex Arcs
A reaction that allows to body to react to a situation even before you
are consciously aware of the situation. These are different from the
typical nervous system reaction since the brain does not
interpret/process the information before the reaction occurs. Only
after the reaction occurs will the brain process what has just
happened.
Examples of some human reflexes are:
Blushing : reddening of the face because of embarrassment or stress
Yawning : deep drawing in of air followed by deep exhalation
Diving : the closing of the mouth and air pathway when the face is put
in watermainly in children under 6 months old
Accommodation : the pupils and the lenses of the eyes change shape
to foc us
Blinking : eyes blink when something suddenly comes at the eyes
Suckling : causes an infant to suck as soon as anything touches the
roof of the mouth 10
## Transmission of a Nerve Impulse
Information is picked up by the dendrites and is transmitted towards
the axon and AWAY from the dendrites of the neuron by a wave of
polarization or difference in electrical potential.
Resting Potential (the conditions when the neuron is not firing)
At rest, neurons contain high concentration of K + ions inside and a
high concentration of Na + ions outside
cell expends energy to do this at rest via active transport
(ACTIVE TRANSPORT) (RECALL: Na +/ K+ pump)
it is the Na +/K + pump that actively transports 3 Na + out of a neuron
for every 2 K + transported into the neuronmore + out then in
this creates a " resting potential " and a charge difference of -70mV
inside the neuron when compared to the outside
cytoplasm of the neuron also has many negatively charged molecules
such as Cl - ions (therefore the inside of the neuron is negatively
charged at rest)
at rest, the neuron is said to be polarized 11
Action Potential (the conditions when the neuron is firing)
a nerve impulse is transmitted only when the resting potential voltage
is altered or "depolarized" facilitated passive transport
this is called an " action potential "
response to a stimulus alters the membrane permeability
voltage -sensitive protein channels in membrane open and admit Na +
ions in to enter the neuron in a small a rea changing the relative
charge from -70mV to +50mV
in response K + ions flow out as a result causing repolarization from
+50mV to -90mV
takes milliseconds to occur
There is a minimum level of stimulus required to cause a depolarization
(threshold potential ) this is known as the all or none law.
o the stimulus must increase the voltage from -70mV to at least -
55mV for the nerve to fire 12
There is always a resting period of several milliseconds before neuron is
ready to fi re again or produce another nerve impulse. This resting
period is called the refractory period (~2ms).
Saltatory conduction occurs in myelinated neurons
action potential are only generated at Nodes of Ranvier
impulse skips from one node to the next
speeds of up to 270 mph or 120 m/s !!! (no wonder we react so
quickly to stimuli) 13
## The Synapse (electrical chemical electrical)
Between each axon and the neighboring dendrite there is a space called a
synaptic cleft . This space and the axon and dendrite on either side of it
are called the synapse . There is no physical contact between adjacent
neurons. In the axon (presynaptic kno b) there are small vesicles
containing chemicals called neurotransmitters .
The neurotransmitter moves across the synaptic cleft via diffus ion ([high]
to [low]). Depending on the neurotransmitter, then effect could be either
excitatory (triggers action potential in the next neuron) or inhibitory
(causes the next neuron to become hyperpolarizedresting). Special
enzymes will break down neurotransmitters from the receptor to prepare
the neuron to receive the next nerve impulse. 14
There are over 50 chemicals that can act as neurotransmitter in the
human body:
acetylcholine : the main neurotransmitter that causes excitation of
neurons the lead to muscle contraction
dop amine : controls many body movements and the feeling of pleasure
serotonin : controls body temperature and mood
endorphin : controls pain blocking and emotional reactions
norepinephrine : controls fight or flight response
Effects of Psychoactive Drugs (ones that affect brain function)
Drugs can affect the nervous system in several ways:
1. decrease the amount of neurotransmitter released
2. block neurotransmitter release
3. increase amount of neurotransmitter or its effects
Success Criteria :
I can d iscuss the parts and function of the nervous system.
I am able to draw and label a neuron.
I can discuss the roles of a neuron, its parts, and glial cells.
I can explain a reflex arc, give examples, and how is it different from
other nervo us system reactions?
I can discuss (in writing and with diagrams) the steps of neuron action
and the factors that affect it.
I can explain how the message from one neuron is passed to the next
neuron. 15
# 9.1 : The Glands and Hormones of the Endocrine
# System (p. 390 -395 )
Learning Goals:
Be able to compare and contrast the nervous and endocr ine
systems.
Explain and distinguish between steroid and non -steroid
hormones with respect to their structure and how they function.
Locate and explain the roles of major endocrine glands.
Discuss the role of tropic hormones.
> Both the endocrine and nervous system enables our bodies to maintain
> homeostasis, but these two systems work differently.
Endocrine vs. Nervous 16
Hormone s
Chemical substances that circulate through the blood and exert some
measure of control over virtually every organ and tissue in the body.
Exocrine Gland
Glands that secrete their hormones through ducts or tubes. (ex. sweat gland,
salivary gland, tear gland)
Endocrine Gland
Glands that are ductless and secrete their hormones directly into the
bloodstream. Since they are in the bloodstream, these hormones will affect
the activity of every organ and tissue in the body. 17
## The Parts/Functions of the Human Endocrine System
Hormone Regulation
Hormone production increases or decreases in response to changing
metabolic needs of the body and by activity of the nervous system and other
endocrine glands.
Hormone secreting cells have receptors that are sensitive to regulatory
hormones form other parts of the body.
The following are factors that impact on the effect a hormone has on the
target organ: rate of hormone production and secretion, [hormone] in the
blood, rate of blood flow to the target, half -life of the hormone. 18
Steroid Hormones (lipid -based)
All are manufactured from cholesterol and as a result they are composed of a
central structure of four carbon rings. A unique side chain differentiates between
thes e hormones and their specific function.
Made in the SER and quickly transported through the bloodstream. They enter
the target cells (some directly), then the nucleus where it activates genes that
results in a specific chemical reaction in the cell.
Ex. c ortisol, estrogen, testosterone, aldosterone, progesterone
Non -Steroid Hormones (amino acid -based)
Made of proteins, peptides, or amino acids and they usually do not enter the
cell. They bind to membrane receptors that initiate a chain of reactions
within the target cell.
This chain reaction of events causes a greater and faster effect than steroid
hormones.
Ex. epinephrine, HGH, thyroxine, insulin 19
Tropic Hormones
Hormones that regulate the hormone production of other endocrine glands in
the body.
In most cases, the hormone that the tropic hormone has caused the release
of will have a negative feedback effect on the tropic hormone.
Interdependence between the nervous and endocrine systems
Some parts of the brain (hypothalamus) are part of the nervous system, but
also release a variety of hormones (TRH, CRH, GnRH) .
Epinephrine is both a hormone and a neurotransmitter.
Both systems dep end on feedback mechanisms.
Most homeostatic processes require both the nervous and endocrine systems
to work together.
Success Criteria :
I am able to compare and contrast the nervous and endocrine
systems.
I can explain and distinguish between steroid and non -steroid
hormones with respect to their structure and how they function.
I can locate and explain the roles of major endocrine glands.
I can discuss the role of tropic hormones. 20
# 9.2: Hormonal Regulation of Growth,
# Development, and Metabolism (p. 396 -403 )
Learning Goals:
Iden tify the different parts of the pituitary gland and explain why
it is considered the master gland.
Outline the different hormones that are released by the anterior
and posterior lobes of the pituitary gland.
Identify the location of the thyroid gland and explain in detail how
it regulates metabolism.
Discuss the conditions of hyperthyroidism and hypothyroidism.
Explain in detail how the thyroid and parathyroid glands regulate
calcium use in the body.
Discuss t he role of Vitamin D in calcium use by the body.
# Pituitary Gland (the Master Gland)
The hypothalamus and pituitary gland work together to regulate many of the
critical physiological processes (metabolic rate, kidney function, appetite,
mental alertness, reproduction, growth, and development). They secrete
hormones that influence the activity of other hormone -producing glands.
Anterior Pituitary
Makes 4 tropic hormones:
o TSH stimulates thyroxine production
o FSH stimulates sperm production, estrogen production
o LH stimulates testosterone production, ovum release, progesterone
release,
o ACTH regulates cortisol and aldosterone production
Also makes HGH which calcium absorption, cell division and
development, lipid metabolism and protein synthesis, conserves proteins
and carbohydrates.
o increases the growth and development of the organism
Also makes prolactin (non -steroid) stimulates the production of mammary
gland tissue and milk production. 21
Posterior Pituitary (considered part of the nervous system)
Only stores the hormones listed below.does not make its own hormones
ADH
o regulates sodium levels in the bloodstream
o increased sodium causes ADH release which makes the kidneys
reabsorb more water . concentrates urin e
o also released when blood pressure drops due to damaged blood vessels
causing vasoconstriction
Oxytocin
o triggers muscle contractions during childbirth and the release of breast
milk 22
**Think about what happens if any of these hormones is released in
inappropriate amounts (too little/too much).**
# Thyroid Gland
The primary function of the thyroid is to regulate metabolic rate.
It does this through the production of the hormone thyroxine (contains 4
iodine atoms).
This hormone increases metabolic rate and oxygen use, especially in the
heart, skeletal muscle, liver, and kidney.
Thyroxine production is regulated by the release of TSH from the anterior
pituitary via a negative feedback mechanism based on the [thyroxine] in the
blood.
TSH cau ses an increase in iodine uptake by the thyroid gland from the blood
to produce thyroxine (to increase metabolism). 23
*T4/T3 are forms of thyroxine 24
Hyperthyroidism (Graves Disease)
Too much thyroxine production. An autoimmune disease where the
antibodies attach to TSH receptors on the thyroid cells and cause them to be
turned on at all times.
As a result, the thyroid enlarges, muscles weaken, metabolic rate increases
(constantly hungry, but losing weight), excessive heat production, sweating
and warm skin due to vasodilation, protruding eyes.
Treated by thyroid removal, thyroid -blocking drugs, or radioactive iodine to
destroy overactive thyroid tissue.
Hypothyroidism (Myxedema)
Not enough thyroxine production. Can be caused by an iodine deficiency in
the diet. Low thyroxine causes more TSH to be released by the anterior
pituitary. This in turn causes the thyroid cells to undergo mitosis. more
cells for thyroxine production
Symptoms are the opposite of hyperthyroidism: reduced metabolic rate
(weight gain but little appetite), no tolerance for cold, decreased heart rate
and output, general weakness and fatigue, poor physical development,
decreased mental capacity.
Lack of iodin e in the diet can also lead to goiter formation (enlarged thyroid
gland). 25 26
# Thyroid and Parathyroid Glands
Calcium is important not just for bones and teeth but also in blood clotting,
nerve impulses, and muscle contractions.
The thyroid also produces the hormone calcitonin while the parathyroid
produces PTH. These hormones are antagonistic in their effect on calcium
levels in the blood.
[Ca 2+ ] in the blood causes calcitonin production and as a result Ca 2+ will be
deposited in bones , not abso rbed from food as well, and also excreted in
urine. Therefore [Ca 2+ ] is lowered in the blood.
[ Ca 2+ ] in the blood causes PTH production and as a result bones will
release Ca 2+ , Ca 2+ will be absorbed by the kidney and duodenum , and
vitamin D will be acti vated . Therefore [Ca 2+ ] is raised in the blood.
*Ca 2+ level regulation
Vitamin D
A hormone that regulates blood [calcium] and [phosphate]. It works by
increasing Ca 2+ release from bones and increasing absorption of Ca 2+ by the
kidneys (blood Ca 2+ ).
Creating vitamin D: Skin (UV light interacting with cholesterol) Liver
(precursor is made into an intermediate) Kidney (converts intermediate
into active form).
PTH stimulates vitamin D production in the kidneys.
Lack of vitamin D in the diet or lack of sun exposure = rickets. 27
Success Criteria :
I can i den tify the different parts of the pituitary gland and explain
why it is considered the master gland.
I can outline the different hormones that are released by the
anterior and posterior lobes of the pituitary gland.
I can identify the location of the thyroid gland and explain in detail
how it regulates metabolism.
I can discuss the conditions of hyperthyroidism and
hypothyroidism.
I can explain in detail how the thy roid and parathyroid glands
regulate calcium use in the body.
I can discuss the role of Vitamin D in calcium use by the body. 28
# 9.3 : Hormonal Regulation of the Stress
# Response and Blood Sugar (p. 404 -413 )
Learning Goals:
Locate the adrenal gland and identify its different parts.
Explain in detail the role of the adrenal medulla in the fight or
flight response.
Explain in detail the role of the adrenal cortex in long -term stress
response.
Discuss the roles of the alpha and beta cells of the Islets of
Langerhans of the pancreas.
Discuss in detail how the pancreas regulates glucose levels.
Compare and contrast Type 1 and Type 2 diabetes.
# The Adrenal Glands and Stress
> The adrenal glands are located on top of each kidney, and each consists of two
> parts each with unique functions but both regulated by the hypothal amus:
> an outer part -the adrenal cortex
> an inner core -the adrenal medulla .29
Adrenal Medulla (fight or flight response)
It receives messages from the sympathetic nervous system .
In response to this stimulation the adrenal med ulla releases epinephrine
(adrenaline) and norepinephrine (noradrenaline) .
These hormones cause an increase in breathing rate, heart rate, blood
pressure , blood glucose levels, and muscle excitation.
In addition, these hormones will cause pupil dilation and the reduction of
blood flow to the extremities .
Epinephrine is also the hormone that is present in the EpiPens of people
with severe allergie s.
Since this part of the adrenal gland is stimulated by the nervous system, its
action is quick but short term.
Adrenal Cortex (long -term stress response)
It is controlled by adrenocorticotropic hormone (ACTH) which is released by
the anterior pituitary and then transported through the blood system. In
addition, ACTH secretion is stimulated by corticotrophin releasing hormone
(CRH) which is released by the hypothalamus.
Since this part of the adrenal gland is stimulated by the endocrine system,
its action is slow er but long term.
The adrenal cortex produces over 30 different steroids, of which the following
are the most important:
mineralocorticoids (ex. aldosterone) increase blood pressure
glucocorticoids (ex. cortisol ) increase blood gluco se levels
gonadocorticoids hormones that help those released by the gonads 30
Aldosterone (mineralocorticoid) causes the kidneys and colon to reabsorb
sodium ions (and therefore retain water) and to secrete potassium ions. It is
secreted in response to decreasing blood pressure and blood volume.
Cortisol (glucocorticoid) promotes conversion of protein and lipids in to
carbohydrates. This replenishes energy reserves in the body. In addition,
cortisol also serves as an anti -inflammatory agent and as a suppressant of
the immune system. Its anti -inflammatory properties make it ideal for use
in asthma medication.
## Adrenal Gland Function Summary 31
# Regulating Blood Sugar
# Pancreas
Exocrine function is the secretion of digestive enzymes into the duodenum.
Endocrine function relates to the production of two hormones (glucagon and
insulin) that act antagonistically to regulate the blood sugar levels in the
blood.
Insulin
Produced in the Beta Cells within the Islets of Langerhans of the pancreas
and then directly secreted into the bloodstream.
blood sugar level by making cell more permeable to glucose uptake.
Plus glycogen formation and storage in the liver .
Also metabolism glucose consumption.
Converts glucose to fat.
Insulin release is controlled by a negative feedback mechanism. The more
glucose in the blood and interstitial fluid, the more insulin that is released.
Glucagon
Produced in the Alpha Cells within the Islets of Langerhans of the pancreas
and the directly secreted into the bloodstream.
blood sugar level by stimulating the breakdown of glycogen stored in the
liver into glucose and converts fat into glucose . This glucose is then released
into the bloodstream.
These two hormones are antagonistic because they have opposite effects on the
body. 32 33
# Diabetes
Ketosis Process by which the body converts fats (instead of carbohydrates)
into energy. The by -products are ketones which gives your breath a sweet,
fruity smell that may be mistaken for alcohol.
Type 1 Diabetes
Also known as Juvenile Diabe tes. The persons immune system attacks the
beta cells within the Islets of Langerhans in the pancreas.
The person can no longer produce insulin and therefore cannot lower blood
sugar level.
Type 2 Diabetes
Also known as Adult -Onset Diabetes. The perso n will either not produce
enough insulin OR the cells of the body do not recognize insulin and
therefore are not affected by it. 34
Success Criteria :
I can l ocate the adrenal gland and identify its different parts.
I can explain in detail the role of the adrenal medulla in the fight
or flight response.
I can explain in detail the role of the adrenal cortex in long -term
stress response.
I can discuss the roles of the al pha and beta cells of the Islets of
Langerhans of the pancreas.
I can discuss in detail how the pancreas regulates glucose levels.
I can compare and contrast Type 1 and Type 2 diabetes. 35
# 9.4 : Hormonal Regulation of the Reproductive
# System (p. 414 -425 )
Learning Goals:
Discuss the roles of GnRH, LH, FSH, inhibin, and testosterone in
the male reproductive cycle.
Discuss the roles of GnRH, LH, FSH, estrogen, and progesterone
in the female ovarian cycle.
Discuss the roles of GnRH, LH, FSH, estrogen, and progesterone
in the female menstrual /uterine cycle.
## Male Reproductive Cycle
Unlike in females who only release eggs periodically, males continually produce
sperm. As in females, the release of GnRH from the hypothala mus regulates
the reproductive cycle.
o The release of GnRH triggers the release of LH and FSH from the anterior
pituitary gland.
o FSH stimulates the productions of sperm (spermatogenesis) as well as the
release of inhibin from the testes .
o Inhibin acts in a negative feedback loop on the anterior pituitary to inhibit
FSH production . this maintains a relatively constant level of sperm
production.
o LH triggers the release of testosterone from the testes.
o Testosterone plays a role in sperm production and the devel opment of male
secondary sex characteristics.
o Testosterone levels work as a negative feedback mechanism to stop the
release of LH by the anterior pituitary .36 37
## Female Reproductive Cycles
Unlike males who continually produce sperm, females only release eggs
periodically. This periodic release of eggs involves two reproductive organs
(ovaries and uterus), the pituitary gland, the hypothalamus, and a series of
hormones that all work together using feedback mechanisms to maintain
homeostasis.
Two cycles, the menstrual cycle in the uterus and the ovarian cycle in the
ovaries, are both regulated via hormone action.
o The ovarian cycle begins when the hypothalamus releases gonadotropin
releasing hormone (GnRH) into the bloodstream.
o GnRH then stimulates the release of luteinizing hormone (LH) and follicle
stimulating hormone (FSH) from the anterior pituitary gland.
o FSH and LH trigger the growth and maturation of follicles in the ovaries and
the slow release of estrogen.
o As the follicle matures, it st arts to secrete large amounts of estrogen just
before the release of the egg (ovulation).
o This sudden rise in estrogen levels, works as a positive feedback mechanism
by turning GnRH production to higher levelswhich leads to a sudden jump
in LH and FSH lev els too.
o Just after ovulation (release of the egg from the follicle) , LH now triggers the
empty follicle to become the corpus luteum (yellow body) , which will then
release both progesterone and estrogen.
o The presence of high levels of these two hormones in the blood works as a
negative feedback mechanism in causing the hypothalamus to stop the
further production of GnRH.
o At the end of the ovarian cycle, the corpus luteum will disintegrate, thereby
stopping its production of estrogen and progester one.
o With the drop in both estrogen and progesterone, the hypothalamus is no
longer inhibited from releasing GnRHand the cycle can begin again. 38
o As you can see in the illustration above, the levels of estrogen and
progesterone also affect the uterus to prepare the body for a possible
pregnancy.
o The high estrogen level causes the endometrium to thicken and to be
supplied with more blood vessels.
o This thickening and preparation for possible pregnancy continues as
progesterone levels rise .
o If fertilization does not occur, then progesterone levels drop leading to the
endometrium breaking down and then being shed from the body.
o If fertilization does occur, then a developing embryo will embed itself into the
endometrium and thereby initiating pregnancy. 39
Success Criteria :
I can d iscuss the roles of GnRH, LH, FSH, inhibin, and
testosterone in the male reproductive cycle.
I can d iscuss the roles of GnRH, LH, FSH, estrogen, and
progesterone in the female ovarian cycle.
I can d iscuss the roles of GnRH, LH, FSH, estrogen, and
progesterone in the female menstrual /uterine cycle. 40
# 10.1: Overview of the Excretory System (p.444 -448)
Learning Goals:
Explain the different roles of the excretory system.
Identify a kidney and its different parts?
Identify a nephron and its different parts?
Functions of the Excretory System
Main function is to filter the blood to remove nitrogen based cellular waste
products from the body in the form of:
Urea from the breakdown of excess amino acids
Uric Acid from the breakdown of nucleic acids
Creatinine muscle action waste product.
Control the water balance (osmoregulation) , pH, and levels of sodium,
pot assium, bicarbonate s, and calcium ions in the blood.
Secrete a hormone stimulating RBC production.
Activate vitamin D production in the skin.
Path of Urine
kidneys ureters urinary bladder urethra outside
(bladder is controlled by two rings of muscles: sphincters) 41
Kidney Structure
Kidneys have three sections:
Renal Cortex contain the upper portion of nearly one million nephrons
Renal Medulla contain the loop of Henle of nearly one million nephrons
Renal Pelvis hollow area that collects urine before going to the ureters
The renal artery brings blood to the kidney, whereas the renal vein takes the
filtered blood away from the kidney.
* Renal = anything relating to the kidneys 42
Nephron Structure
The nephron is the filtering unit of the kidney, and it has the following parts:
o Bowmans Capsule (renal cortex) a cup -like structure that allows
components of blood to enter the nephron
o Proximal Tubule (renal cortex) allows material to be reabsorbed back
into the blood
o Loop of Henle (renal medulla) concentrates the urine and reabsorbs
many of the essential ions
o Distal Tubule (renal cortex) further reabsorption of essential
materials and the location for blood pH regulation
o Collecting Duct further urine concentration
Success Criteria :
I can e xplain the different roles of the excretory system.
I can i dentify a kidney and its different parts?
I can i dentify a nephron and its different parts? 43
# 10.2: Urine Formation in the Nephron (p.449 -455)
Learning Goals:
Explain in detail the step -by step process of urine formation by
nephrons.
Nephron Structure and Function
1. Blood plasma and other small particles enter the nephron at the Bowmans
capsule from a network of tiny porous capillaries called the glomerulus.
(nephric filtrate)
2. Nephric filtrate moves into the proximal tubule where re -absorption begins
to remove and return necessary materials from the filtrate back to the
bloodstream via active (glucose, amino acids , cations ) and passive transport
(an ions, water) while removing H + from the bloodstream .
3. The filtrate now moves to the loop of Henle where more water is reabsorbed
into the bloodstream via osmosis. The water concentration is always higher
in the loop of Henle because the cells of the renal medull a have a very high
Na + concentration.
4. The high [Na +] is the result of active transport out of the ascending loop of
Henle.
5. Cl - also leaves since it is attracted to the leaving Na + and because it is higher
in concentration in the loop of Henle.
6. Once in the distal tubule, the filtrate has low [Na +], low [Cl -], and low [H 2O].
7. At this point, K+, H+ (pH related), creatinine (by -product of muscle action) ,
and drugs (antibiotics and other s) are actively transported into the filtrate
from the bloodstream. The reabsorption and secretions by the distal tubule
is very much affected by hormones in the blood.
8. Once in the collecting duct, more water can be reabsorbed based on the need
by the bod y. The removal of more water from the urine can concentrate it up
to four times more than it was entering the collecting duct. Once again,
hormones have a big effect on this part of the nephron.
9. Nephrons now empty the filtrate into the urine collecting part of the kidney
(pelvis). 99% of water has been recovered into the bloodstream along with all
other nutrients (glucose, amino acids). 44
> *the lumen is the inside of the nephron*
Success Criteria :
I can e xplain in detail the step -by step process of urine formation
by nephrons. 45
# 10.3 : Other Functions and Disorder of the
# Excretory System (p. 456 -465 )
Learning Goals:
Discuss the effect of anti -diuretic hormone of urine production.
How do alcohol and caffeine affect urine production?
Discuss the effect of aldosterone on urine production.
Explain in detail how the kidneys help to regulate blood pH .
Explain the link between blood pH and respiratory system.
Osmoreceptors
Types of cells that sense the osmotic pres sure (pressure exerted by water
movement). When blood plasma is too concentrated (lack of water), then the
osmotic pressure increases)
Anti -Diuretic Hormone (ADH) [water] regulation
ADH is secreted by the posterior pituitary gland, which is controlled by the
hypothalamus.
ADH increases the permeability of the distal tubule and collecting ducts to
water allowing more water to be re -absorbed when the body requires more
water. As a result, the osmotic pressure is lowered.
Too much water in the body ADH production is inhibited by the
hypothalamus and more water is excreted in the urine. As a result, the
osmotic pressure is increased.
Alcohol and caffeine block ADH release increase amount of water in urine
( amount of u rine) 46
Aldosterone [salt] regulation
Aldosterone is secreted by the adrenal cortex.
Aldosterone causes the distal tubules and collecting ducts to reabsorb Na +.
At the same time, it causes the excretion of K +.
An indirect effect of Na + reabsorption is water reabsorption ..concentrates
urine
Blood pH Regulation
Blood pH needs to remain around 7.4 for proper enzyme activity.
H+ can be actively transported into the filtrate to balance pH.
Kidneys work with the respiratory system and a car bonic acid buffer system
to help buffer blood pH.
The main blood pH buffer is carbonic acid (H 2CO 3).
Low pH HCO 3- take up excess H + to form H 2CO 3
High pH H2CO 3 dissociate s into HCO 3- and H +
The link to the respiratory system is that H 2CO 3 breaks down into CO 2 and
H2O. CO 2 levels in the body are controlled by our breathing.
H+ + HCO 3- H 2CO 3 H 2O + CO 2
This reaction goes towards equilibrium!
High pH decreased breathing rate ( CO 2 release) which causes H 2CO 3 to
dissociate to lower pH
Low pH increases breathing rate (CO 2 release) which causes H 2CO 3
formation to raise pH 47
Blood pH Scenarios
High Blood pH (low [H +])
Body needs to increase [H +].
As a result, breathing rate slows down.
o This leads to an increase in [CO 2] and [H 2O] in the body.
[CO 2] + [ H2O] H2CO 3 HCO 3- + H +
The kidneys also work to reabsorb more H +.
As a result, [H +] increases and blood pH .
Low Blood pH (high [H +])
Body needs to lower [H +].
As a result, breathing rate speeds up.
o This leads to a decrease in [CO 2] and [H 2O] in the body.
[CO 2] + [ H2O] H2CO 3 HCO 3- + H +
The kidneys also work to secrete more H +.
As a result, [H +] decreases and blood pH .
Success Criteria :
Discuss the effect of anti -diuretic hormone of urine production.
How do alcohol and caffeine affect urine production?
Discuss the effect of aldosterone on urine production.
Explain in detail how the kidneys help to regulate blood pH .
Explain the link between blood pH and respiratory system.