Transcript Human Systems

Human Systems
Nervous, Endocrine, & Reproductive
The Nervous System
OH MY!!!
CONSISTS OF THE BRAIN AND SPINAL CORD
Receive sensory information
from various receptors & then
interpret & process the
information.
If a response is needed some
portion of the brain or spinal
cord initiates a response =
motor response.
The cells that carry this
information are neurons
Spinal Nerves:
•There are 31 pairs
•Emerge from the spinal cord
•Some are motor nerves & some are sensory nerves
Cranial Nerves:
• There are 12 pairs
• Emerge from the brain stem of the brain
•EX: optic nerve pair (carry visual information from
retina to the brain)
Broken down to the somatic nervous system-voluntary activities
Autonomic nervous system- controls involuntary activites (ex: heartbeat)
COMPARE THE ORGANIZATION OF NERVOUS SYSTEMS
Nerve net + nerves
Neurons today are the same structurally &
functionally as they were 600 mya. Why?
With cephalization came more complex
nervous systems like the CNS
In what phylum do we 1st
see an organization of cells
to tissues?
What the heck do they do differently?
• Sensory neurons: transmit information from
external stimuli and internal conditions.
– Send the info to the CNS.
• Interneurons: analyze & interpret sensory
input
• Motor neurons: motor output leaves through
these & communicate with effector cells.
• Effector cells: muscle cells or endocrine cells.
Activity surrounding a reflex response
Typical Pathway of Nervous System
Explain in as much
detail as possible the
pathway if you should
touch something hot.
As soon as you touched the pot of boiling water a sensory
receptor began an action potential or “nerve impulse”.
Each receptor in your body is designed to transform a particular kind of stimulus into
an action potential
There are a chain of neurons which take the impulse towards the CNS. In this case the
spinal cord.
Once at the spinal cord the action potential is routed to the appropriate area of the
CNS for interpretation.
During its stay in the CNS the action potential is carried by interneurons.
Your brain has now made the decision to remove your hand.
Relay neurons send the action potential to the spinal cord & out one of the spinal
nerve pairs (motor neuron).
The motor neuron is taking the impulse/action potential to the muscle and a chemical
signal is sent to the muscle (effector cells) which results in a contraction, moving your
hand.
The name for the muscle (in
this case) is the effector.
Junction where a
neuron sends a
chemical to muscle
tissue is called:
motor end plate
The Mad Mad Neuron
Nervous system pathway is a one way road from
dendrite to synaptic terminals.
Functions
• Dendrites: receive signals
• Axon: transmits signals
• Synapse terminals: location where
neurotransmitters are released
• Neurotransmitters: chemical messengers that
travel out of the presynaptic neuron and into
the postsynaptic neuron.
– Ex: acetylcholine, epinephrine, norepinephrine,
dopamine, serotonin, and GABA
Neurons of Vertebrates & Most
Invertebrates
• Have cells that are helper cells to the neurons
called: Glial or glia cells
– Nourish neurons, insulate the axons, & regulate
the extracellular fluid around the neurons.
– Outnumber the neurons in the mammalian brain
10-50 fold.
– During a synapse some neurotransmitters are sent
to the glial cells to be metabolized for fuel
Types of Glia Cells
Astrocytes: found in the brain and spinal cord. They are star-shaped neuroglia that reside in
endothelial cells (inner layer of vessels) of the CNS that form the blood-brain barrier. This
barrier restricts what substances can enter the brain; protecting it against toxins.
Schwann cells & oligodendrocytes: cover axons with a myelin sheath which provide
electrical insulation.
Microglia: protect against pathogens.
How do neurons communicate with each other?
This occurs through a chemical communication called a synapse.
-examples of chemicals: acetylcholine, epinephrine, dopamine,
norepinephrine, serotonin, and GABA
Different communication synapse
patterns may occur…
Let’s look a bit closer….
• Neurotransmitters:
chemical messengers
that travel out of the
presynaptic neuron and
into the postsynaptic
neuron.
– Ex: acetylcholine,
epinephrine,
norepinephrine,
dopamine, serotonin, and
GABA
• They are either
stimulatory or inhibitory
Generations of Postsynaptic Potentials
• Neurotransmitters which generate action potentials are known as
Excitatory Neurotransmitters.
– Are stimulatory to the brain's nerve fibers.
– Cause Na+ to diffuse into the postsynaptic neuron
– EX: acetocholine
• Neurotransmitters which prohibit action potentials are known as
Inhibitory Neurotransmitters.
– Are calming brain chemicals. They help balance our mood; they can be
diminished in the face of too many excitatory brain chemicals.
– Causes hyperpolarization of a neuron by allowing Cl- move across
postsynaptic cell into the membrane or cause K+ to move out of the
postsynaptic cell
– EX: GABA
GABA- Inhibitory neurotransmitter
•
•
•
•
•
•
Brain’s natural valium
Linked with relaxation, anti-anxiety
Provides calmness to your body
Involved in the production of endorphins
Controls muscle movement
Used to help with symptoms of Huntington’s
Disease
Acetylcholine
• Common neurotransmitter to vertebrates &
invertebrates.
• Helps with muscle stimulation, memory formation,
learning, heart rate, energy level.
• Released by motor neurons
• Controls your brain speed by determining the rate at
which electrical signals are processed throughout your
body
– Alzheimer’s disease is associated with an imbalance
• If it remained in the synapse, the postsynaptic neuron
would keep “firing” indefinitely.
– Acetylcholinesterase breaks down the acetylcholine in the
synapse.
Dopamine- inhibitory/stimulatory
• Both an inhibitory and excitatory neurotransmitter
depending upon where in the brain and at which
particular receptor site it binds to.
• Dopamine is the main player in:
– regulating our reward circuitry and pleasure centers
(hence dopamine's role in addictions).
– Critical for memory and motor skills.
– responsible for motivation, interest, and drive.
– involved in muscle control and function
A shortage of dopamine, particularly the death of dopamine neurons in the
nigrostriatal pathway, is a cause of Parkinson's disease, in which a person loses
the ability to execute smooth, controlled movements.
Problems can ensue if dopamine is too
high or too low.
• Dramatically elevated levels, the so-called
"dopamine storm,"
• associated with hallucinations, delusions, agitation…
• Low levels of dopamine
–
–
–
–
–
–
don't feel alive,
have difficulty initiating or completing tasks,
poor concentration,
no energy, and
lack of motivation.
cause memory, concentration, and attention
problems
• Stimulants such as prescription medications
for ADD/ADHD, & caffeine address symptoms
of low dopamine
– Pushes existing (but dwindling) supply into the
space between two neurons (synpase).
• Can improve symptoms(for a short time)
– if continued for any length of time it can inhibit
natural transmission and actually cause/hasten
dopamine depletion
Serotonin- Inhibitory
• Associated with
anger regulation
• Body temperature
• Mood
• Sleep
• Pain control
• Appetite
• Provides a satisfied
feeling in the body
Sustain levels of high stress, lack
of sleep, poor nutrition,
inflammation, genetic
mutations, and certain
prescription medications can
slowly erode your levels of
serotonin leading to depression,
worry, insomnia, obsessive
thoughts, compulsive behaviors,
carbohydrate cravings, PMS, and
exaggerated response to pain.
How do these neurotransmitters
work?
How do these neurotransmitters
work?
7.5
The neurotransmitters
binding to the receptor
protein initiates to ion
channel opening and Na+
diffusing in which starts
the action potential down
the postsynaptic neuron
9.5
The neurotransmitter is
broken down by enzymes
& is released from the
receptor protein. They will
diffuse back across the
synaptic gap.
9.75
Sodium channel closes
This causes the nerve impulse in
the postsynaptic membrane
Decision making
• A neuron is on the receiving end of many
excitatory and inhibitory stimuli.
• The neuron sums up the signals
– If the sum is excitatory the axons will “fire”
– If the sum is inhibitory the axons will not
• The summation of the messages is the way
decisions are made by the central nervous
system.
What is a nerve impulse?
• Nerve impulse = action potential
• Can be measured in the same way as electricity is
measured
– Voltage
• Millivolts
• The conductor of a neuron is the axon
– Is covered by a myelin sheath
• Increases the rate at which an action potential passes down
an axon.
• Membrane potential: the electrical potential
difference across the plasma membrane.
• When babies are born, many of their nerves lack
mature myelin sheaths.
– As a result, their movements are jerky, uncoordinated,
and awkward.
• In adults, the myelin sheath can be damaged or
destroyed by:
– stroke, inflammation, immune disorders, metabolic
disorders, nutritional deficiencies (such as a lack of
vitamin B12). Poisons, drugs, and excessive use of alcohol
can damage or destroy the myelin sheath.
• Disorders that cause demyelination in the central
nervous system and have no known cause are called
primary demyelinating disorders. Multiple sclerosis
is the most common of these disorders.
Resting potential
• Area of a neuron that is ready to send an action
potential but is not currently sending one.
• This area is considered polarized (-70mV)
– Characterized by the active transport of sodium ions
(Na+ ) out of the axon cell & potassium ions (K+) into
the cytoplasm.
– There are negatively charged ions permanently
located in the cytoplasm
– This collection of charged ions leads to a net positive
charge outside the axon membrane & negative charge
inside.
There are also gated ion channels
• Stretch-gated ion
channels: in cells that
sense stretch
• Voltage-gated ion channels:
located in axons &
open/close when
membrane potential
changes.
• Ligand-gated ion
channels: located at
synapses & open/close for
a specific chemical.
Action Potential
• Described as a self-propagating wave of ion movements in and
out of the neuron membrane
• This is the diffusion of the Na+ & the K+ .
– Sodium channels open & then potassium ones do too.
• This is the “impulse” or action potential
• It is a nearly instantaneous event occurring in one area of the
axon = depolarization
– This area initiates the next area on the axon to open up the channels.
• This action continues down the axon.
• Once an impulse is started at the dendrite end that action
potential will self-propagate itself to the far axon end of the
cell.
Depolarization opens the activation gates on
most Na+ channels, while the K+ channels
activation gates remain closed. Na+ influx makes
the inside of the membrane positive with respect
to the outside.
The inactivation gates on most Na+
channels close, blocking Na+ influx. The
activation gates on most K+ channels
open, permitting K+ efflux which again
makes the inside of the cell negative.
A stimulus opens the activation gates on some Na+
channels. Na+ influx through those channels
depolarizes the membrane. If the depolarization
reaches the threshold, it triggers an action potential.
The activation gates on the Na+ and K+ channels are closed, & the
membrane’s resting potential is maintained.
Both gates of the Na+ channels are closed, but the
activation gates on some K+ channels are still open. As
these gates close on most K+ channels, & the
inactivation gates open on Na+ channels, the
membrane returns to its resting state.
Return to Resting Potential
• Remember that one neuron may send dozens of
action potentials in a very short period of time.
• Once an area of the axon sends an action
potential it cannot send another until the Na+ &
K+ have been restored to their positions at the
resting potential.
• Active transport is required to move the ions =
repolarization
– The time it takes for a neuron to send an action
potential & then repolarize is called: the refractory
period of that neuron.
Inside of
membrane
becomes less -
Inside of
membrane
becomes more Action Potential video
What makes it go faster:
• Different sized axons
– Bigger = faster
Saltatory conduction: By jumping
from one node to the next, this increases the
conduction velocity, allowing the signal to
travel faster
Lights…Camera…Action
Potential!!
Time for an activity 
The Endocrine System
Glands that secrete hormones as a
chemical signal which is sent to
different parts of your body.
Helps maintain homeostasis
What are hormones?
• Chemical messengers that have a
physiological effect far from where
they originated.
• They travel through the bloodstream
• Can affect every cell in your body.
• Most are under the control of a
feedback mechanism.
The Nervous System & The
Endocrine System
Work cooperatively in order to
ensure homeostasis.
Just to mess with you a little…
• Neurosecretory cells (aka neurohormones)– Nerve cells located in endocrine glands that
release hormones
• A few chemicals serve as both hormones and
neurotransmitters.
– EX: epinephrine/adrenaline & norepinephrine
• “fight or flight” hormone produced in adrenal gland
• Serves as a neurotransmitter
Difference between neurotransmitters
& endocrine signals
• Neurotransmitters: usually small, nitrogencontaining compounds that are conveyed from
one specialized nerve cell to another along
specific nerve highways throughout the body
& are designed to elicit immediate responses.
• Endocrine signals: usually hormone secreted
from glands that use blood vessels to disperse
their signal molecules, to elicit a slower
response.
Group Work!!!!
• Each group will be in charge of teaching about their
chosen hormone.
–
–
–
–
•
•
•
•
•
Testosterone
Thyroxin
Progesterone
Human growth hormone
-Leptin
-Estrogen
-Oxytocin
-Antidiuretic hormone
You will discuss where they originate
Where they go
What their purpose is
How is homeostasis maintained.
Use drawing to help with presentation
Sometimes the
glands come in
pairs…
Sometimes they
are alone…
Endocrine system’s main job…
Help maintain homeostasis!!!
Aka: your happy levels 
Types of Hormones & Their
Function
• Steroid hormones:
– Example is estrogen
– Function: increases thickness of uterine lining
• Proteins & Peptide hormones:
– Example is insulin
– Function: stimulates glucose uptake by body cells
• Amines derived from amino acids hormone:
– Example is thyroxin
– Function: increases metabolic rate
Basic Signal Transduction
Pathways
• INCLUDE:
– Reception
– Signal Transduction
– Response
Cell-Surface Receptors for Water-Soluble Hormones
• The receptors for most
water-soluble
hormones
• Are embedded in the
plasma membrane,
projecting outward
from the cell surface
• Peptide/protein
hormones
• Amine hormones
Intracellular Receptors for Lipid-Soluble Hormones
• Steroid hormnoes, thyroid
hormones, and the hormonal form
of vitamin D
• Enter target cells and bind to specific
protein receptors in the cytoplasm or
nucleus
• The protein-receptor complexes then
act as transcription factors in the
nucleus, regulating transcription of
specific genes
Figure 45.3b
(b) Receptor in cell nucleus
The same hormone may have
different effects on target cells
that have
• Different receptors for the hormone
• Different signal transduction pathways
• Different proteins for carrying out the
response
• The hormone epinephrine
• Has multiple effects in mediating the body’s response to short-term stress
Different receptors
different cell responses
Epinephrine
Epinephrine
Epinephrine
a receptor
b receptor
b receptor
Glycogen
deposits
Vessel
constricts
(a) Intestinal blood
vessel
Vessel
dilates
(b) Skeletal muscle
blood vessel
Different intracellular proteins
Glycogen
breaks down
and glucose
is released
from cell
(c) Liver cell
different cell responses
Homeostasis is maintained by:
Positive and Negative Feedback
Loops
Homeostatic control of body temperature
Negative feedback: physiological changes that bring a value back
closer to a set point.
Message is sent by
thermoreceptors
Possitive
Feedbackamplifies the response
What type of feedback is this??
Let’s take a look at how our blood
glucose levels are maintained.
If blood glucose is too low
• Alpha cells in pancreas synthesize & secrete
glucagon.
• This hormone stimulate the breakdown of
glycogen into glucose in liver cells & its release
into the blood.
If blood glucose is too high
• Beta cells synthesize and secrete insulin into
the bloodstream.
• This hormone stimulates the uptake of
glucose by various cell types.
– Particularly : skeletal muscle and liver cells
• Stimulates the conversion of glucose to
glycogen
What type of feedback loop is
this?
Negative feedback
Diabetes
• A disease characterized by hyperglycemia
– High blood glucose
TYPES OF DIABETES
Type I
β cells do not produce enough insulin
Type II
Body cell receptors do not respond
properly to insulin= insulin resistance
Can be controlled by diet
Can be controlled by the injection of
insulin
Autoimmune disease- immune system
attacks β cells & destroys them
Less than 10% of diabetics have this type. Most common form of diabetes - 90%
Most often occurs in children & young
adults
Associated with genetic history, obesity,
lack of exercise, advanced age, & certain
ethnic groups
TREATMENT FOR DIABETES
Type I
Testing the blood glucose concentration
regularly
Inject insulin when high or likely to
become high
Type II
Adjust diet to reduce the peaks & troughs
of blood glucose
Smaller amounts of food should be eaten
frequently rather than infrequent large
meals.
Injections are often given before a meal to Avoid foods with high amounts of sugar
prevent a peak of blood glucose
Timing is very important because insulin Starchy food should only be eaten if it has
molecules do not last long in the blood
a low glycemic index indicating it is
stream
digested slowly
High fiber foods should be included to
A permanent cure may be achievable by slow the digestion of other foods
coaxing stem cells to become fully
Strenuous exercise & weight loss are
functional replacement beta cells.
beneficial as they improve insulin uptake
and action
Rhythms & Clock
Circadian Rhythm
• are physical, mental and
behavioral changes that
follow a roughly 24-hour
cycle.
• responding primarily to
light and darkness in an
organism's environment
Biological clock
• are groupings of interacting
molecules in cells throughout
the body. A "master clock" in
the brain coordinates all the
body clocks so that they are in
synch.
• group of nerve cells in the
brain called the
suprachiasmatic nucleus, or
SCN (located in the
hypothalamus)
Our biological clocks drive our circadian rhythms.
You are set to respond to the circadian rhythm based on an inner biological clock.
Melatonin
sleep
sleep
awake
at night
Controls circadian rhythms
sleep
awake
Secreted
here
These cells (SCN) set
a daily rhythm by
controlling the
secretion for
melatonin
Jet lag: circadian rhythm is set for
the departure not the destination.
Only lasts for a few days
The ganglion in the retina send
impulses to the SCN when light is
detected aids in readjusting the
rhythm.
Other effects:
-found in kidneys suggests it controls urine production -Taking melatonin helps with jet lag
-controls core body temperature (drops it at night)
Leptin video
Thyroxin
•
•
•
•
Secreted by the thyroid gland
Regulates metabolic rate
Helps control body temperature
Hormone contains 4 iodine molecules so
prolonged deficiency of iodine in the diet
prevents the making of thyroxin
• All cells are target cells
– Mainly muscle, liver, and brain cells
Growth Factors
• Stimulate cell
division & growth
(proliferation) and
differentiation
• Must be present
in the
extracellular
environment
Prostaglandins help regulate
the aggregation of platelets
• An early step in the formation
of blood clots
• Help sperm reach the egg
• Help induce labor
• Send out an alarm by inducing
a fever and or inflammation
Figure 45.5
• The hypothalamus and pituitary integrate many functions of the vertebrate
endocrine system
• The hypothalamus and the pituitary gland
• Control much of the endocrine
system
The hypothalamus works in
conjunction with the nervous
system. It receives information
from the nerves and initiates
hormone production depending
on environmental conditions.
Figure 45.7
Hypothalamus
Neurosecretory
cells of the
hypothalamus
Axon
Posterior
pituitary
Anterior
pituitary
HORMONE
TARGET
ADH
Kidney tubules
Oxytocin
Mammary glands,
uterine muscles
Pituitary Gland:
-posterior: releases neurohormones made in the hypothalamus
-anterior: regulated by trophic hormones produced in the hypothalamus.
What hormones does the
posterior pituitary gland release?
Oxytocin-contract uterine muscles
during childbirth & mestration
Antidiuretic hormone (ADH)- acts on
kidneys to increase water retention
REMEMBER: THESE HORMONES ARE MADE IN THE HYPOTHALAMUS AND
STORED IN THE POSTERIOR PITUITARY GLAND
Antidiuretic Hormone (ADH) –produced in the
hypothalamus; stored & released from the posterior
pituitary gland
• Controls how much water is
reabsorbed & back into the
bloodstream.
– If ADH is secreted, the collecting
duct of the kidneys becomes
permeable to water & water leaves
by way of osmosis into the highly
hypertonic medulla of the kidney.
• Little to no urine volume
– Water is then reabsorbed back into
the bloodstream
- If ADH is not secreted, the collecting
duct remains impermeable to water
- Urine will then contain a high
amount of water.
What hormones does the anterior
pituitary gland release?
• Other hypothalamic cells produce tropic
hormones-these are hormones that
stimulate other endocrine glands &
stimulate them to secrete their own signals,
such as the anterior pituitary gland & are
produced by neurosecretory cells in the
hypothalamus
• These hormones are secreted into the blood and
transported to the anterior pituitary (aka
adenohypophysis)
Nontropic Hormones
The nontropic hormones produced
by the anterior pituitary include:
• Prolactin stimulates lactation in
mammals
• But has diverse effects in different
vertebrates
• MSH influences skin pigmentation
in some vertebrates
• And fat metabolism in mammals
• Endorphins
• Inhibit the sensation of pain
Growth Hormone
• Similar in structure
to prolactin
– Indicates they
evolved from the
same ancestral gene
(too much)
(too little)
*Some athletes take growth hormones to enhance performance but research shows
it has little impact provided the athlete is not deficient in GH to begin with.
Nonpituitary hormones help
regulate metabolism, homeostasis,
development, and behavior
• Thyroid Hormone
• Parathyroid Hormone
• Insulin and Glucagon
• Adrenal Hormones
• Gonadal Sex Hormones
• Melatonin
Nonpituitary hormones help regulate
metabolism, homeostasis,
development, and behavior
• The thyroid gland
–
–
Hypothalamus
Consists of two lobes located on the ventral surface of the
trachea
Produces two iodine-containing hormones, triiodothyronine
(T3) and thyroxine (T4)
• The hypothalamus and anterior pituitary
– Control the secretion of thyroid hormones
through two negative feedback loops
Anterior
pituitary
• The thyroid hormones
TSH
– Play crucial roles in stimulating
metabolism and influencing development
and maturation
Thyroid
T3
+
T4
• Hyperthyroidism, excessive secretion of thyroid
hormones
• Can cause Graves’ disease in humans
Figure 45.10
• Hypothyroidism, minimal to no secretion of thyroid
hormones
• Can cause weight gain, lethargy, & intolerance to cold
• In infants it can cause cretinism (low skeletal growth &
poor mental development
Parathyroid
Hormone
Why is the parathyroid
important?
Adrenal Hormones: Response to Stress
• Epinephrine & norepinephrine stimulate the
“fight or flight” response.
– Nerve impulses from the brain stimulate the adrenal
medulla to release both hormones
– These hormones are released into the blood stream.
– They travel to the liver and muscle cells to break down
glycogen and release glucose.
•
•
•
•
Increase energy
Blood pressure
Breathing rate increases
Cellular metabolic rate rises
ALL PROMOTE
THE FLIGHT OR
FIGHT RESPONSE
More Adrenal
Hormones:
Response to
Stress
Steroid hormones from the
adrenal cortex are secreted
because of the stress stimulus
initiated by the hypothalamus
Hormones from adrenal cortex
are corticosteroids.
-EX: glucocorticoids (cortisol)
mineralocorticoids
(aldosterone)
It is suggested that both of
these hormones work together
to maintain homeostasis when
the body is under stress over a
long period of time.
REPRODUCTION
HUMAN REPRODUCTION (sexual reproduction):
sperm, egg, & fertilization ensures genetic
variation in our species.
Vas
defrens
bladder
Seminal vesicle
penis
prostrate
urethra
epididymis
testes
scrotum
ureter
Vas defrens
Seminal vesicle
prostate
scrotum
epididymis
testes
penis
Bladder
Ureter
Seminal
Vesicle
Urethra
Ejaculatory
Duct
Vas Deferens
(sperm duct)
Penis
Epididymis
Testes
Scrotum
Prostate
Gland
Bulbourethral
Gland
Testosterone: Male Hormone
• Determines the development of male genitalia
during embryonic development
• Ensures development of secondary sex
characteristics during puberty.
• Maintains the sex drive of males throughout
their lifetime.
Fallopion tubes/oviducts
ovary
cervix
uterus
vagina
vulva
Oviduct (Fallopian Tube)
Ovary
Uterus
Bladder
Clitoris
Cervix
Urethra
Vagina
Rectum
A LOOK AT WHAT HAPPENS TO
A WOMAN’S BODY DURING
PREGNANCY
AWESOME PICTURES FROM ON CONCEPTION TO
JUST BEFORE BIRTH
Reproductive organ functions
Male Reproductive Organs & Functions
Testis
Produces sperm & testosterone
Scrotum
Holds testes at lower than core body
temperature
Epididymis
Stores sperm until ejaculation
Sperm duct/vas deferens
Transfers sperm during ejaculation
Seminal vesicle & prostate gland
Secretes fluid containing alkali, proteins &
fructose that is added to sperm to make semen
Urethra
Transfer semen during ejaculation & urine during
urination
Penis
Penetrates the vagina for ejaculation of semen
near the cervix
Reproductive organ functions
Female Reproductive Organs & Functions
Ovary
Produces eggs, estrogen & progressive
Oviduct/Fallopian tubes
Collects eggs at ovulation, provides a site
for fertilization then moves the embryo to
the uterus
Uterus
Provides for the needs of the embryo &
then fetus during pregnancy
Cervix
Protects the fetus during pregnancy &
then dilates to provide birth canal
Vagina
Stimulates the penis to cause ejaculation &
provides a birth canal.
Vulva
Protects internal parts of the female
reproductive system
The menstrual cycle
• Starts at puberty
• It’s a hormonal cycle lasting for ~28 days
– Times the release of the ovum (egg)
• For fertilization & implantation
• The inner lining of the uterus (endometrium)
grows thick (becomes highly vascular)
• If no implantation then blood vessels
breakdown (menstruation)
What are the hormone
levels at ovulation?
FSH, LH & estrogen= high
Progesterone = low
FSH- follicle stimulating hormone
LH- luteinizing hormone
Graafian follicle
Oocyte + zona pellucida
(glycoprotein coat)
For 10-12 days
Gonadotrophin
releasing hormone
Complete this chart
Hormones involved in the female menstrual cycle.
Hormone
Origin
Target
Causation
GnRH
Hypothalamus
Anterior
pituitary gland
Production of FSH & LH
FSH
Anterior
pituitary gland
Ovaries
Stimulate follicle growth &
production of oestrogen
LH
Anterior
pituitary gland
Ovaries
Stimulate follicle growth &
production of oestrogen
Oestrogen
Ovaries
Endometrium
Make endometrium highly
vascular
Progesterone
Corpus luteum
Endometrium
Maintains endometriums highly
vascular state
During ovulation what is happening
with the 4 hormones?
LH: is high
FSH: is high
Estrogen: is high
Progesterone: low
What is happening with the hormones
during menstruation?
All are low except FSH
As long as progesterone is being produced the endometrium will
not break down.
The hypothalamus will not produce GnRH as long as progesterone
levels & estrogen levels are high.
Therefore FSH and LH will remain at non conducive levels to
produce any other Graafian follicle.
Once the corpus luteum begins to break
down this lowers the levels of progesterone
and estrogen which signals the hypothalamus
to secrete GnRH
Natural Fertilization
• Occurs in the fallopian tubes 24-48 hours after
ovulation
• Zygote begins dividing and has divided many
times by the time it reaches the uterus for
implantation.
• As long as the endometrium is in a highly
vascular state, implantation will occur.
Problems couples may face with
having a baby
•
•
•
•
Low sperm count (in males)
Failure to achieve or maintain an erection
Do not ovulate regularly
Blocked fallopian tubes
One way to solve the problem…
• In-vitro fertilization:
– 1ST the female will take a drug that stops her pituitary gland secreting FSH
or LH.
• This stops estrogen & progesterone production as well.
• The goal is to suspend the females normal menstrual cycle & allows the doctors to
control the timing & amount of egg production.
– Female is then injected with FSH & LH for 10 days
superovulation
• Ensures development of several more Graafian follicles
– Several eggs are harvested surgically
– Male ejaculates into a container
– Harvested eggs are mixed with the sperm
– Observed under a microscope to determine which eggs have been
fertilized and are mitotically dividing normally.
– 2 to 3 embryos are placed in the female uterus
– Leftovers are frozen & used later, if needed.
Ethical issues concerning IVF
FOR
• Allows couples who
normally would not be able
to have children to have
them.
• Unhealthy embryos are
eliminated for consideration
• Genetic screening can be
done prior to implantation
AGAINST
• Embryos not used are either
frozen or destroyed
• Legal issues with regards to
unused embryos if there is a
divorce.
• Genetic screening at embryo state
could lead to choosing desirable
characteristics
• IVF bypasses natures way of
decreasing the genetic frequency
of that reproductive problem
• IVF increases the chances of
multiple births & with it the
problems associated with multiple
births.
Reproduction & rearing of offspring
require free energy beyond that
used for maintenance & growth.
Reproductive strategies in response to
energy availability
• Food availability and ambient temperature
determine energy balance, and variation in
energy balance is the ultimate cause of
seasonal breeding in all mammals and the
proximate cause in many. Photoperiodic
cueing is common among long-lived mammals
from the highest latitudes down to the midtropics.