Organisms and Their Environment Area of Study 1: Adaptations of Organisms UNIT 2 BIOLOGY.
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Transcript of Organisms and Their Environment Area of Study 1: Adaptations of Organisms UNIT 2 BIOLOGY.
Organisms and Their Environment
Area of Study 1: Adaptations of Organisms
UNIT 2 BIOLOGY
WEEK 2: Learning OutcomesBy the end of the week, you should be
able to: Describe the structure of the endocrine
system. Explain hormonal control in complex
multicellular organisms. Explain how organisms regulate water
balance (osmoregulation).
Feedback Systems: Hormonal ControlFeedback systems are the general mechanism
of nervous or hormonal regulation in animals. Feedback occurs when the response to a
stimulus has an effect of some kind on the original stimulus. The nature of the response determines how the feedback is 'labelled'.
Negative feedback: is when the response reduces the effect of the original stimulus. It works in the opposite direction.
Positive feedback: is when the response enhances the original stimulus. It works in the same direction.
Negative FeedbackNegative feedback is most
common in biological systems. Examples of this are:Blood glucose concentrations
rise after a sugary meal (the stimulus), the hormone insulin is released and it speeds up the transport of glucose out of the blood and into selected tissues (the response), so blood glucose concentrations decrease (thus decreasing the original stimulus).
Draw a flowchart to illustrate this
Another example of negative feedback
Exercise creates metabolic heat which raises the body temperature (the stimulus), cooling mechanisms such as vasodilation (flushed skin) and sweating begin (the response), body temperature falls (thus decreasing the original stimulus).
Draw a flowchart to illustrate this
Positive FeedbackPositive feedback is less common, which is
understandable, as most changes to steady state pose a threat, and to enhance them would be most unhelpful. However, there are a few examples:A baby begins to suckle her mother's nipple and
a few drops of milk are released (the stimulus). This encourages the baby and releases a hormone in the mother which further stimulates the release of milk (the response). The hungry baby continues to suckle, stimulating more milk release until she stops. (Positive feedback, it would not have helped the baby if suckling decreased milk flow, as in negative feedback!)
Another example...A ripening apple releases the volatile plant
hormone ethylene (the stimulus). Ethylene accelerates the ripening of unripe fruit in its vicinity so nearby fruit also ripens, releasing more ethylene (the response). All the fruit quickly becomes ripe together. ("One 'bad' apple has ruined the whole lot." The biological explanation - positive feedback - for an old saying!)
Draw a flowchart!
Yet another...Fever is an example of a positive feedback
mechanism.
Explain to the person next to you how you
think it works...
The Endocrine (Hormonal) SystemHormones act by altering biochemical
reactions in target cells.Exocrine glands secrete their products
straight onto the target tissue via a duct.Endocrine glands secrete their products
into the circulatory system via the capillary network. These hormones are carried by the
bloodstream, to target tissues elsewhere in the bodies, which then interpret the messages and act on them.
The Endocrine SystemThere are many different glands in the body that
release hormones.Hypothalamus – midbrain.Pituitary gland – base of the brain; beneath the
hypothalamus.Thyroid gland – in the throat.Parathyroid gland – rear surface of the thyroid
gland.Thymus – just behind the sternum, over the
heart.Adrenal glands – above the kidneys.Pancreas – organ attached to the small intestine.Ovaries – in females.Testes – in males.
Label me! Hypothalamus
ENDOCRINE EXOCRINE
Hypothalamus Sweat glands
Pituitary gland Mammary glands
Thyroid and Parathyroid glands Salivary glands
Pancreas Digestive glands
Adrenal Glands
Testes and Ovaries
HormonesThere are 2 types of hormones which differ
slightly in their mode of action.Amino acid hormones - these are
proteins, which act by binding directly to receptors on the cell membrane. E.g. insulin and glucagon.
Steroid hormones - these are lipid based, they act by crossing the plasma membrane. E.g. testosterone and oestrogen.
HormonesSPECIFICITYThe stimuli will only affect a particular group of
hormone secreting cells. The hormone released will then only affect
those cells with the appropriate receptor.E.g. growth stimulating hormone produced in
the pituitary gland only affects bone and muscle and promotes protein synthesis.
SPEED OF ACTIONThe hormonal system is slower than the
nervous system because the molecules have to be passed through blood or tissue to reach the target cells.
MODE OF ACTIONOnce hormones have entered the cell they
can bind to internal receptors.They then cause the release of second
messengers or they can enter the nucleus and regulate the production of other proteins by switching genes on or off.
ANTAGONISTIC HORMONESPairs of hormones with opposite effects.
ANTAGONISTIC HORMONES
E.g. insulin converts glucose to glycogen and glucagon converts glycogen back into glucose when needed.
Interaction of Glands - Hypothalamus
The hypothalamus is:
located in the brain and controls the release of hormones from the pituitary gland.
an important link between the endocrine and nervous systems.
Pituitary Gland
FUNCTIONIt secretes nine hormones that directly regulate
many body functions and controls functions of other glands.
Two distinct portions:Anterior (front)Posterior (back)
HOW IT IS CONTROLLED Hypothalamic releasing hormones stimulate cells
of anterior pituitary to release hormones. Nerve impulses from hypothalamus stimulate
nerve endings in the posterior pituitary gland to release hormones.
Pituitary Gland
Pituitary Gland
Disorders: Too much growth
hormone (GH) in early childhood can result in a condition called gigantism from a hyperactive anterior pituitary gland.
Too little GH can result in Pituitary Dwarfism.
Robert Wadlow1918 - 19402.7m tall
Thyroid GlandFunction: plays a major role in regulation the body’s metabolism.
Thyroid Gland
Thyroid Gland
Disorders: If the thyroid gland produces too
much thyroxin, it can cause a condition known as Hyperthyroidism - fast heart beat resulting in palpitations, a fast nervous system with tremor and anxiety symptoms, a fast digestive system resulting in weight loss and diarrhoea. – Graves’ disease
If too little thyroxin is produced it is called hypothyroidism – weight gain, fatigue and constipation – Hashimoto’s Thyroiditis
PancreasFunction: Glycogen in the Pancreas help to
keep the level of glucose in the blood stable.
Disorders: When the Pancreas fails to produce or properly use Insulin, it can cause a condition known as Diabetes Mellitus.
Functions: The adrenal glands
release Adrenaline in the body that helps prepare for and deal with stress.
Also regulates kidney function.
Adrenal Gland
OvariesFunctions: Pair of reproductive organs found in women that
produce eggs.Also secrete oestrogen and progesterone, which
control ovulation and menstruation.
Testes
Functions: Pair of reproductive glands that produces sperm. Also secrete testosterone to give the body its
masculine characteristics.
Pineal Gland
Functions:Secretes Melatonin
Regulates circadian rhythms (helps with sleeping)Promotes sexual developmentInfluences skin pigmentation
ThymusProduces the hormone thymosin, which
promotes the development of T lymphocytes (white blood cells) that are involved in immunity.
The thymus helps establish the immune system in the first few years of life, but stops working after puberty. It will then gradually reduce in size as we get older.
HORMONE SOURCESITE OF ACTION
REGULATES
InsulinPancreas – islets of
Langerhans (β cells)
Body cells Blood sugar level
GlucagonPancreas – islets of
Langerhans (α cells)
Liver Blood sugar level
Antidiuretic hormone (ADH)
Pituitary gland Kidney Water absorption
Thyroid stimulating
hormone (TSH)Anterior pituitary Thyroid gland
Thyroid hormone production
Thyroxine Thyroid Body cells Metabolic rate
Adrenaline AdrenalHeart and Muscles
Heart rate and oxygen uptake
QuestionsWhat is an endocrine gland?What is a hormone? How does it bring
about a response?
Words To KnowEndocrine SystemHormoneEndocrine gland
Comparison of Nervous System and Endocrine System
Neurons release neurotransmitters into a synapse, affecting postsynaptic cells.
Glands release hormones into the bloodstream.
Only target cells of hormone respond.
Comparison of Nervous System and Endocrine System
Complete this Table
FEATURE NERVOUS SYSTEM ENDOCRINE SYSTEM
Similarity
Medium of transmission
Speed of travel
Effectors
Duration of response
Example
Involves electrical transmission
Involves chemical transmission
Hormones in circulatory system
Nerves
Slow Fast
Tissues and glands
Specific location – muscles and
glands
Long Short
Water BalanceWater is the fluid medium in which
everything happens at the cellular level in organisms.
There must be a balance between loss and gain.
How can water be lost?
How can water be gained?
OsmoregulationThe regulation of water is described as
osmoregulation, a feedback mechanism that is under the control of hormones.
Effectively controlling the amount of water available for the cells to absorb.
Osmoregulation in Mammals
Water balance in mammals is directly link to blood pressure
It is also link to maintaining the salt levels in the body
Involves the kidney
OsmoregulationIncreased water raises the blood pressure
and decreased water lowers the blood pressure.
Two chemical compounds play a part:The hormone vasopressin is an ADH (Anti-
Diuretic Hormone) that aids reabsorption of water.
Renin is an enzyme that helps regulate sodium levels, and thus water levels in the blood.
LinksMcGraw-Hill animationMr Anderson explainsDetailed animation
How does vasopressin (ADH) work when we are dehydrated?
1. Osmoreceptors in the hypothalamus detect high concentrations of solutes in the blood (low water).
2. A thirst sensation is generated by the osmoreceptors.3. ADH is released from the hypothalamus.4. ADH travels to the posterior pituitary gland where
it is released into the blood.5. ADH travels to the kidneys where it increases the
permeability of the tubules to water.6. The kidneys reabsorb more water; the solute
concentration decreases.7. Water concentration in the blood increases.8. Negative feedback leads to a decreased secretion of
ADH from the hypothalamus.
How does renin work when we are dehydrated?1. Blood volume decreases and blood pressure falls.2. This reduces filtration taking place in the
glomerulus in the kidneys.3. Pressure-sensitive receptors in the kidneys detect
this.4. Renin is released into the blood by the kidneys.5. Renin initiates chemical reactions in the adrenal
glands which releases the hormone aldosterone.6. Aldosterone increases sodium ion reabsorption by
the kidneys back into the blood.7. Due to osmosis, water travels in the same
direction as the sodium ions.8. The blood pressure rises.
To sum it upDraw a negative feedback diagram showing
the stimulus, receptor, control centre, transmission of message, effectors and response.
Osmoregulation in WaterSome marine organisms body fluids are
isotonic to there external environmentAs long as they remain in their external
environment their internal environmental will stay stable
These organisms are called Osmoconformers
What happens then when the external environments are hypotonic or hypertonic to the internal environment of an organism?
Lets have a look
Do you remember this term?
Can you remember
these terms?
Osmoregulation in Fish
Murray CodFresh Water Fish
SnapperSalt Water Fish
With your knowledge of osmosis describe what would happen to each of these animals in terms of their salt and water levels if they did not have
ways to control it?
Osmoregulation in FishMurray CodFresh Water FishWould take in too much water. Would lose too much salt.
WHY?
WHY?
What types of adaptations are
these?
How does it maintain its salt water balance?Gills that are highly permeable to water and
salt. Scales that are impermeable to water and
salt.Rarely drinking water.Excreting large amounts of dilute urine.Actively absorbing salts by specialised cells in
the gills.
Osmoregulation in Fish
SnapperSalt Water FishWould lose too much waterWould take in to much salt
WHY?
WHY?
What types of adaptations are
these?
How does it maintain its salt water balance?Scales that are impermeable to water and
salt. Gills that are highly permeable to water and
salt.Drinking almost continuously.Producing small amounts of urine.Actively excreting salts from specialise cells in
the gills.
Adaptations to Regulate Water Balance
TO DO:Come up with a list of
Structural, Physiological and Behavioural
Adaptations that could help an organism regulate water
balance.
Adaptations to Regulate Water Balance
StructuralWaterproof
layerHairs or valves
guarding openings
CocoonsStore it
PhysiologicalReabsorb water
from faecesProduce highly
concentrated urine
Rely on metabolic water
Osmoconformers
Osmoregulators
BehaviouralSpend most time
in burrowsDrinking water
from environment
Words To KnowOsmoregulationOsmoregulatorOsmoconformer