1. Homeostasis, Hormones & Excretion
6.6, 11.3, D.5

2. Homeostasis The human body works best under the following conditions:
Body temperature of 37°C
0.1 % blood sugar level
Blood pH level of ~7.4
The external environment can alter these levels
Ex: Outside temperature, physical activity, meals…

3. HOMEOSTASIS
HOMEOSTASIS is the maintenance of the internal environment within an acceptable range, despite fluctuations in the external environment.
It creates a dynamic equilibrium: a stable condition with fluctuating limits

4. Homeostasis
Requires constant monitoring and feedback about body conditions.
Homeostasis requires the interaction of several regulatory systems
I.e.: Nervous system, respiratory system, endocrine system, the excretory system, the circulatory system….

6. Ex of Biological Homeostasis:
Blood pH
Carbon dioxide concentration
Blood glucose concentration
Body temperature
Water balance
Blood pressure

7. What’s wrong with this graph?

8. Blood pH Homeostatic level is pH 7.4
Narrow acceptable range:
< 7.35 = acidosis
>7.45 = alkalosis
Non-homeostatic levels can cause blood proteins and enzymes to ionize and change shape and function.

9. Blood pH
Blood pH is maintained by the carbonic acid-bicarbonate buffer system
BUFFER: substance that maintains pH
H2O CO H2CO HCO H+
water carbon carbonic bicarbonate hydrogen
dioxide acid ion ion

10. Low pH
Ex: after eating a vinaigrette salad, H+ ions will enter the bloodstream, and the blood will become too acidic (pH to low!)
The increase in H+ means that there is a greater chance of HCO3- ions finding a H+ and forming H2CO3, thus increasing the pH

11. High pH
When a base enters the blood stream, the pH will rise making it more basic because the base will bond with H+ and remove them from the blood.
To compensate, H2CO3 ionizes to replace the missing H+ and lower the pH back to acceptable ranges

12. Carbon Dioxide Concentration
Oxygen and Carbon Dioxide concentration are maintained with the aide of chemoreceptors in the walls of certain blood vessels that can cause an increase or decrease in breathing rate.

13. Negative Feedback Systems
Mechanisms that make adjustments to bring the body back within an acceptable range (like a thermostat)
With negative feedback, the result of a process causes a reversal of the result.
Homeostasis relies on negative feedback systems to maintain homeostatic levels

14. Negative Feedback A thermostat is an example of negative feedback.
Temperature
Rises
Temp change
Detected by Thermostat
Heater switched off
Temp Decreases
Temp Decreases
Temp change
Detected by Thermostat
Heater switched on
Temperature
Rises

15. All homeostatic control system have 3 functional components
A monitor/sensor
Measure the current situation
A coordinating center
Compares the current situation to the homeostatic norm
Can activate a mechanism to adjust situation
Regulator
A mechanism to restore normal balance

16. Example During exercise, CO2 levels increase
Chemoreceptors in the arteries are stimulated (sensor)
They send a message to the medulla oblongata (coordinating center)
The medulla sends impulses to the intercostal muscles (regulator) to increase the rate of breathing to flush out excess CO2 from the body

17. Thermoregulation
Maintenance of body temperature within a range that allows cells to function efficiently
Different optimal temperatures and ranges exist for each animal

18. Thermoregulation and Invertebrates
Invertebrates, most fish, amphibians, and reptiles are also known as ECOTHERMS
These animals depend on air temperature to regulate metabolic rates.
Ex: reptiles sun themselves on rocks or retreat to shaded areas to regulate their body temperature

19. Thermoregulation and Vertebrates
Mammals and birds are ENDOTHERMS
They are able to maintain a constant body temperature regardless of surroundings.
Thermoreceptors in the skin and in the hypothalamus of the brain monitor temperature changes in the environment and in the blood.

20. If an organism is too hot, it can cool down by using one or more of the following mechanisms:
Vasodilation
Sweating
The evaporation of fluid from the skin requires energy, which is taken from body heat.
Decreased metabolism
Many biochemical reactions produce heat as a by-product
Behavioural adaptations

21. Vasodilation Blood vessels in the skin dilate (become wider)
This increase blood flow to the skin.
Blood will bring heat.
Skin will become warmer and the heat will dissipate into the environment

23. Behavioural Adaptations
Birds: bathing
Dessert Rodents: retreat into burrows
Dogs: dig holes and allow cool earth to absorb heat from belly

24. If an organism is too cold, it can warm up using one or more of the following mechanisms:
Vasoconstriction
Shivering
Muscular contractions that produce heat a by-product
Increased metabolism
Biochemical reactions often produce heat as a by-product
Fluffing of hair or feathers
Thick layer of brown fat or blubber
Provides insulation, and generates heat
Special structures
Ex: polar bears have hairs that can absorb UV light

25. Vasoconstriction Blood vessels in the skin contract (get narrower)
This decreases blood flow to the skin
Less heat loss to the environment

27. Fluffing of hair or feathers
Increases the thickness of the insulating layer of air
Goosebumps:
when you are cold, nerve message are carried to the muscle that surround the hair follicles in your skin – causing the hair to “stand up”
The small bump made by the contraction of the muscle creates the goose bump
The hair traps warm air next to the surface of your skin and helps reduce heat loss

28. The Endocrine System

29. Endocrine System: a system of glands that secrete hormones to regulate body function
HORMONES: chemical messengers or regulators
- they are released by cells in one part of the body and affect cells in other parts of the body to speed up or slow down processes.
Endocrine Hormones – are produced in endocrine glands and secreted directly in the blood and distributed by the circulatory system.

30. Makes hormones and regulates the pituitary gland
Pineal gland (makes serotonin which regulates sleep patterns)

31. Endocrine Gland

32. How do Hormones Signal Cells?
Note: Hormones do not affect ALL cells
Depends on whether or not that cell has a receptor for the particular hormone.
(TARGET CELLS are the cells hormones act on)
There are 2 types of hormones:
1. Steroid Hormones
2. Protein Hormones (including polypeptides, glycoproteins, amines or tyrosine derivatives)

33. Steroid Hormones
made from cholesterol (lipid); Complex ring of C, H, and O
Soluble in fat but NOT water – so can dissolve through cell membrane or nuclear membrane
Inside the cell they bind to receptor in the cytoplasm or nucleus to form the hormone-receptor complex

34. Steroid Hormones
The receptor-hormone complex can then switch certain genes on or off by promoting or inhibiting the transcription of genes in the nucleus
ex: sex hormones: estrogen, testosterone
ex: cortisol
LIVER: cortisol activates the genes for glucogenesis (the conversion of amino acids to glucose)
CELLS: prevents the expression of the insulin receptor gene (preventing glucose storage)
PANCREAS: inhibits the transcription of the insulin genes

35. Steroid Hormones

36. Steroid Hormones
SECRETORY
CELL
HORMONE
TARGET CELL
RECEPTOR

37. Protein Hormones Made of chains of amino acids or modified amino acids
Soluble in water but insoluble in fats (can’t dissolve through cell membrane)
Ex: insulin, growth hormone

38. Protein Hormones
The protein hormones attach to receptor sites on the cell membrane
The hormone-receptor complex leads to the release of a secondary messenger in the cell that can spread throughout the cell and relay messages
Ex of secondary messengers: Ca2+ and cyclic adenosine monophosphate (cyclic AMP)
Secondary messengers then activate enzymes in the cell.

39. Protein
Hormones

40. Example Ex: epinephrine Involved in the “fight or flight” response
Under a threat, an organism needs a supply of blood glucose as an energy source
In the liver, once cAMP is created, it activates enzymes which will activate the process of glycogen breakdown and inhibit glycogen synthesis (thereby increasing blood glucose levels)

41. Animations

42. Control Systems
The body relies on the nervous system and the endocrine system for control of organs and tissues
The nervous system allows the body to adjust quickly to environmental changes
The endocrine system is designed to maintain control over longer durations

43. Hypothalamus
The hypothalamus in the brain is part of both the nervous system and the endocrine system
As an endocrine gland it creates hormones that either
a) are stored in the (posterior) pituitary gland
b) control the release of hormones from the (anterior) pituitary gland

44. Pituitary Gland (The Master Gland)
“master gland” because it controls the other endocrine glands
(However, it is controlled by the hypothalamus)
Located at the base of the brain; connected to the hypothalamus by a stalk
The pituitary produces and stores hormones
The hypothalamus stimulates
their release when necessary

46. Posterior Lobe
Stores and releases hormones that are actually made by the neurosecretory cells of the hypothalamus
The hormones travel from the hypothalamus to the pituitary via specialized nerve cells
They are stored in the pituitary and released into the blood when necessary
(The hypothalamus will send a nerve response to have the hormones released)
Ex: ADH (antidiuretic hormone), oxytocin

47. Posterior Lobe Ex: ADH release
Hypothalamus creates ADH and stores it in pituitary gland
Osmoreceptors in hypothalamus recognize osmotic pressure (solute concentration of blood)
Impulses are sent to pituitary to increase or inhibit the release of ADH into blood stream accordingly

49. Anterior Lobe Produces its own hormones
However, the hypothalamus regulate their release with inhibiting or releasing hormones made by the hypothalamus
The inhibiting and releasing hormones are transported to the anterior lobe of the pituitary via a portal vein
This stimulates the release of pituitary hormones which will travel through the blood to target cells

50. Anterior Lobe Ex: TSH and TRH
The anterior lobe produces and stores TSH (thyroid stimulating hormone)
TSH is released by the anterior lobe when the hypothalamus releases TRH (thyroid releasing hormone)

53. Thyroid Stimulating Hormone (TSH) Thyroid Gland
Target Organ
Primary Function
Thyroid Stimulating Hormone (TSH)
Thyroid Gland
Releases hormones made in the thyroid (such as thyroxine)
Adrenocorticotropic Hormone (ACTH)
Adrenal Cortex
Stimulates the release of hormones involved in the stress response (such as cortisol)
Somatotropin (STH) also known as Growth Hormone (GH)
Most body cells
Promotes growth
Follicle Stimulating Hormone (FSH)
Gonads (ovaries and testes)
Females: stimulates follicle development in the ovaries
Males: Promotes the development of sperm cells in the testes
Luteinizing Hormone (LH)
Females: stimulates ovulation and the formation of the corpus luteum
Males: stimulates the production of testosterone
Prolactin
Mammary Glands
Maintains milk production in lactating females

54. Posterior Pituitary Hormones
Target Organ
Primary Function
Antidiuretic Hormone (ADH)
kidneys
Increases water reabsorption in the kidney
Oxytocin
Uterus, mammary glands
Initiates strong uterine contractions
Triggers milk release in lactating females

55. Hormones that Affect Blood Sugar

56. Maintaining Blood Glucose
The pancreas is both an exocrine gland (producing digestive enzymes) and an endocrine gland
As an endocrine gland it produces 2 hormones essential to maintaining blood sugar levels within homeostatic ranges

57. The islets of Langerhans, are the cells in the pancreas that produce insulin and glucagon
α cells of Islets of Langerhans: secrete glucagon
β cells of Islets of Langerhans: secrete insulin

58. Insulin When blood glucose levels are too high, insulin is secreted.
It causes
the muscle cells to absorb more glucose (from the bloodstream)
hepatocytes and muscle cells to covert glucose to glycogen
In fat tissue (adipose tissue) , glucose to be converted into fat
Insulin is broken down by the cells it acts upon so it must be continuously secreted

59. Glucagon Secreted by the pancreas when glucose levels are too low.
It travels throughout the body but its main target is the liver.
Causes hepatocytes to convert glycogen to glucose and release it to the blood

61. Diabetes Mellitus
Disorder in which a person does not produce enough insulin or in which a person does not react to insulin.
Can lead to hyperglycemia: high blood glucose
Can cause nerve damage, retina damage, blood vessel damage, kidney failure, comas, and even death.

62. Signs of Diabetes
High, unregulated glucose levels means high levels of glucose in your urine
This will prevent water reabsorption in the kidneys
This leads to frequent urination
This leads to a person being constantly thirsty and craving sugary drinks

63. Type I Diabetes
Also called “juvenile diabetes” because diagnosed as a child
Individual doesn’t make insulin, or makes insufficient levels of insulin.
Causes: often by the body producing antibodies against insulin or β cells of Islets of Langerhans; the destruction of the β cells of Islets of Langerhans
Treatment: insulin injections, pancreas transplant, diet regulation

64. Type II Diabetes Occurs later in life, as an adult
Insufficient amounts of insulin are produced or the body has become less sensitive to insulin
Causes: obesity, age, family history, lifestyle
If the individual has a high glucose diet, their body will become desensitized to insulin.
Treatment: regulated diet, exercise, medications to increase insulin production and lower blood glucose levels.

65. Diet (As Treatment)
Reduced sugar intake and avoiding foods with high sugar contents
Smaller more frequent meals
High-fibre foods (prevents sugar absorption)

66. Gestational Diabetes Temporary; Develops during pregnancy
Increased risk that the mother and child will develop type 2 diabetes

67. Stress Hormones

68. Adjustments to Stress
Stress may be physical, mental, emotional or psychological
When stress is identified, both the endocrine and nervous system make adjustments that enable the body to cope with the problem.
The body requires more ATP energy to deal with stressful situation, and thus requires more glucose and oxygen

69. Adjustments to Stress
The nervous system rapidly adjusts to stress by increasing heart rate and diverting blood (carrying glucose and oxygen) to the needed muscles.
Although somewhat slower in response, hormones from the endocrine system provide a more sustained response to the stimulus.
Stress hormones provide more blood glucose to cope with the elevated energy requirements brought on by stress.

70. Response To Stress Glucagon : secretion increases
Converts glycogen to glucose so more ATP is available to deal with situation
Insulin: - Secretion decreases
Prevented from lowering blood glucose

71. The Adrenal Gland Located above the kidneys
2 glands in one shell: adrenal medulla and the adrenal cortex

72. Adrenal Medulla Inner gland Regulated by the nervous system
Produces epinephrine (adrenaline) and norepinephrine which are known as your “fight or flight” hormones and released during stressful situations.

73. Adrenal Cortex The outer casing of the adrenal gland
Regulated by other hormones (i.e. ACTH)
Produces 3 different hormones

74. 1. Glucocorticoids
Ex: Cortisol: Increases the amount of amino acids in the blood which can then be broken down into glucose for energy or used for protein synthesis
Cortisol increase glucose uptake by the brain, and reduces it in the muscles (so brain can respond to stress)
Glucocorticoids are also involved in suppressing inflammation in the immune response

75. 2. Mineralcorticoids 3. Sex Hormones
Ex: aldosterone: increases Na+ retention and water reabsorption in the kidneys
Androgens including testosterone and estrogen precursors.
3. Sex Hormones

77. It is more difficult to adjust to emotional or psychological stress because the increased energy supply is not always used up.
Although increased nerve activity requires greater energy, the ATP provided by homeostatic adjustment is greater than the demand.
Prolonged exposure to high blood glucose, high blood pressure, and an elevated metabolic rate can create more problems for the body

78. Problems Associated with Long-Term Stress
Problem Created
High Blood Sugar
Alters osmotic balance leading to an increased fluid uptake by blood and increased blood pressure
Increased Blood Pressure
Possible rupture of blood vessels due to higher pressure
Increased Heart Rate
can lead to higher blood pressure
possible destruction of heart muscle