Biology 3 Flashcards
- Immune System
- Define Acquired Immunity
- A specific response to one particular virus, bacteria or other pathogen based upon prior exposure.
- There are two types of acquired immunity:
- humoral
- cell-mediated.
- Digestive System
- Stomach
- Chief Cells
- Stomach
- Make and secrete the zymogen PEPSINOGEN (into gastric pits/stomach lumen)
- Integumentary System
- Functions
- What parts of the body does this system include?
- Protection against abrasion
- physical barrier to pathogens
- vitamin D synthesis
- insulation/cushioning (due to subcutaneous fat)
- prevention of water-loss
- temperature regulation.
- Includes the hair, nails, skin, and the oil and sweat glands located within the sk
- Musculoskeletal System
- Describe Skeletal Muscle anatomy
- A muscle group, such as the bicep, is a bundle of many fasciculi.
- Each fascicle is a bundle of many long, tubular cells
- called muscle fibers.
- Each fascicle is a bundle of many long, tubular cells
- Around each muscle cell is a specialized cell membrane
- …called the sarcolemma.
- Inside each muscle cell are many nuclei (multinucleate).
- Nearly the entire volume of each cell is filled with smaller round tubes called myofibrils.
- Myofibrils are long bundles of proteins mainly composed of actin and myosin fibers interconnected in repeating units
- …called sarcomeres.
- Bundles of myofibrils are interwoven among portions of the muscle cell’s endoplasmic reticulum
- called the sarcoplasmic reticulum.
- Myofibrils are long bundles of proteins mainly composed of actin and myosin fibers interconnected in repeating units
- It is the sarcoplasmic reticulum that
- stores and
- releases Ca2+
- to control the contraction process
Integumentary System
- Skin
- Dermis vs. Epidermis
- What is the Epidermis mostly made up of?
- What 5 things comprise the Dermis?
- What is the dermis an example of?
- Dermis vs. Epidermis
Epidermis
- Is avascular and made up of mostly dead or dying, keratinized cells
Dermis
- Contains:
- blood vessels
- hair follicles
- sebaceous glands (oil)
- sudoriferous glands (sweat)
- nerve endings
The dermis is an example of CONNECTIVE TISSUE!
- Digestive System
- Function=?
- To separate food molecules from each other (i.e., physical digestion) and break up those molecules into their monomers for absorption (i.e., chemical digestion).
- These monomers are then used for both energy and as a source of carbon chains and amino acids.
- Immune System
- Acquired Immunity
- Humoral Immunity
- Describe the Secondary response
- Humoral Immunity
- Acquired Immunity
- the immune system’s response to that same pathogen DURING SUBSEQUENT EXPOSURES
- Musculoskeletal System
- Skeletal Muscle
- The Sarcomere
- Describe the arrival of the Action Potential
- The Sarcomere
- Skeletal Muscle
- The junction between a skeletal muscle and a motor (i.e., somatic) nerve is called the neuromuscular junction.
- Acetylcholine (ACh) is the ONLY neurotransmitter used at neuromuscular junctions.
- When Ach is released from the motor neuron at the neuromusclular junction
- ….an action potential is initiated.
- The action potential will then spread along the muscle cell sarcolemma and down specialized invaginations of the sarcolemma
- called T-tubules
- that dive deep into the muscle cell
- causing the release of Ca2+
- that dive deep into the muscle cell
- called T-tubules
- Musculoskeletal System
- Smooth Muscle
- Characteristics
- Smooth Muscle
- Characteristics
- involuntary, non-striated, one nucleus
- Smooth muscle is what controls the gut, viscera, blood vessels, etc.
- Reproductive System
- Menstrual Cycle
- Describe Fertilization
- Menstrual Cycle
- Fertilization usually occurs in the fallopian tubes.
- Sperm and egg, traveling toward one another, generally meet here.
- Implantation normally occurs in the uterus, but can occur in the fallopian tubes, leading to a “tubal” or “ectopic” pregnancy
- This is bad– only the uterus can support a growing fetus with nutrients
- Ectopic pregnancies can lead to miscarriages
- Digestive System
- Stomach
- Functions?
- Stomach
- Functions include:
- food storage
- mixing
- Is the first site of protein digestion
- Without an adequate stomach, food moves too fast through the digestive system
- resulting in incomplete digestion and absorption.
- Musculoskeletal System
- Cardiac Muscle
- Provide a conceptual definition for the term “autorhythmic.”
- Do heart muscle cells contract in response to innervation by a NERVE?
- Cardiac Muscle
The SA node acts like a natural pacemaker for the heart.
The action potential for each heart beat ORIGINATES IN THE SA NODE
NOT with a nerve from the nervous system.
Nerves do innervate the heart, but they only regulate its rhythm up or down—they do not initiate that rhythm.
- The vagus nerve (parasympathetic) slows the heart rate, and sympathetic nerves increase heart rate.
- Reproductive System
- Describe The Egg
- Eggs are the female gametes.
- Singular scientific name is “ova”
- Plural form is “ovum”
- An immature egg is called an “oocyte”
- An egg begins meiosis as a germ line cell in the ovary of a female fetus
- Is arrested at Prophase I of Meiosis at birth.
- Not until puberty and menstruation is Meiosis I completed
- Even then, all cells remain in this arrested state
- …except for those that begin maturing in a follicle in preparation for ovulation.
- Even then, all cells remain in this arrested state
- Meiosis II is not completed until after the sperm fertilizes the ovum.
- Digestive System
- Epiglottis
- Describe
- Epiglottis
- This is the organ that caused the debunking of the “honey soothes the vocal chords” myth discussed in the previous lesson
- This u-shaped flap of cartilage and membrane is oriented nearly vertical in its default position
- This allows air to proceed past it and into the trachea
- During the act of swallowing, this flap folds down over the opening to the portion of the larynx that contains the “voicebox” and trachea
- Disallowing food down the trachea and allowing food down the esophagus
- Digestive System
- Stomach
- Name the 4 Stomach Lining Cell Types
- Stomach
- Mucous Neck Cells
- Chief Cells
- Parietal Cells
- G-cells
- Immune System
- Describe the Imflammatory Response
- First, macrophages, mast cells and dendritic cells are residents of nearly ALL tissues.
- When damage is caused
- by injury, bacterial invasion, etc.
- Mast Cells & Dendritic cells are activated to release chemicals such as:
- histamines
- leukotrienes, and
- prostaglandins
- These chemicals increase:
-
blood flow to the injury site
- creating heat and redness.
-
permeability of veins and lymph vessels
- This causes plasma and interstitial fluid to flood the infection site
- resulting in swelling (a.k.a., edema).
- This causes plasma and interstitial fluid to flood the infection site
-
blood flow to the injury site
- This swelling and increase in chemicals lead to:
- the pain associated with inflammation as well.
- Neutrophils are recruited via chemotaxis in very large numbers to the inflammation site.
- The Gallbladder
- Define
- What is its relation with Bile?
- What does Bile do?
- Is Bile’s action an example of physical or chemical digestion?
-
Stores and concentrates bile, but does NOT produce bile.
- Bile is produced IN THE LIVER
- Bile emulsifies fats
- i.e., separates fat molecules from each other
- increasing the surface area available for enzymatic digestion
- i.e., separates fat molecules from each other
- Bile emulsifies fats, but it does not break any bonds
- therefore it is an example of physical rather than chemical digestion
- Immune System
- Tissues of the Immune Sys
- Thymus
- Tissues of the Immune Sys
- Location where T-lymphocytes (a.k.a., T cells):
- Acquire immunocompetency
- Differentiate, and
- Mature
Acquired Immunity
-
Humoral Immunity
- Describe B-cells
- Where do they develop?
- Where do they mature?
- Each B-cell produces only ONE of a certain kind of _____ ______ on its ______
- What is this thing called?
- Describe B-cells
When you see “B-cells” or “antibody,” THINK of humoral immunity
B-cells develop in
- bone marrow
mature in:
- Bone marrow, or
- lymph tissues
Each B-cell produces only ONE of a certain kind of protein receptor on its membrane
called an antibody (a.k.a., immunoglobulin)
Each antibody will recognize and bind with only one foreign particle
called an antigen
- Bone
- Define:
- Hematopoeisis
- red bone marrow
- yellow bone marrow
- spongy bone
- compact bone
- Define:
-
Hematopoiesis
- is the name given to the formation and differentiation of blood cells in the bone marrow.
-
Red bone marrow
- Hematopoesis occurs in the red bone marrow that fills the pockets of spongy bone.
- Hematopoiesis does NOT occur in the yellow bone marrow that fills the medullary cavity of long bones.
-
Yellow bone marrow
- consists mostly of fat.
-
Spongy bone
- contains many open spaces, formed by the interwoven trabeculae.
- These spaces are filled with red bone marrow
- The interior of flat and irregular bones, as well as the bulbous ends of the long bones, is filled with spongy bone
- contains many open spaces, formed by the interwoven trabeculae.
-
Compact bone
- Is the dense bone that surrounds the outside of all bones, and constitutes the shafts of long bones.
- is many times more compact than spongy bone
- It is organized into orderly units called osteons
- the only spaces it contains are:
- Haversion canals, and
- canaliculi.
Digestion of Lipids
- Where does it BEGIN & where is it COMPLETE by?
- In the place where digestion begins, what 2 things do lipids encounter?
- Do these things enter the bloodstream or lacteal?
- In order to be transported across the membrane, _______s are broken down to ___
- WHAT happens once they’re across the membrane?
- BEGINS in the small intestine (duodenum)
- COMPLETE by the end of the small intestine
- Lipids enter the LACTEALS (NOT the blood stream)
Digestion of lipids CANNOT begin prior to their reaching the small intestine–
- where they encounter bile and lipase
Triglycerides are broken down to fatty acids, transported across the membrane, then reformed into triglycerides
- Immune System
- Tissues of the Immune System
- Spleen
- Tissues of the Immune System
- Somewhat analogous to a lymph node that filters blood instead of lymph
- high concentration of:
- leukocytes (WBCs)
- platelets
- Storage of a considerable amount of blood
- …that can help combat hemorrhagic shock
- Breaks down and recycles parts of old erythrocytes (RBCs)
- Musculoskeletal System
- Functions
- Movement
- support and stabilization
- generation of heat
- aide to circulation
- maintenance of homeostasis.
- Musculoskeletal System
- Cardiac Muscle
- What do both cardiac & skeletal muscle utilize?
- What is in high [] in cardiac muscle?
- How are cardiac muscle cells connected?
- What’s one difference b/t skeletal & cardiac muscle cells?
- Cardiac Muscle
- Like skeletal muscle, cardiac muscle utilizes myoglobin
- It also contains very large numbers of mitochondria to prevent fatigue
- Cardiac muscle cells/fibers are connected by intercalated discs containing gap junctions.
- It is through these junctions that the ions used to initiate action potential pass effectively making the heart muscle cells into a functional syncitium.
- Allowing them to act as a single unit.
- It is through these junctions that the ions used to initiate action potential pass effectively making the heart muscle cells into a functional syncitium.
- Unlike skeletal muscle cells, cardiac cells continue dividing after differentiation
- Musculoskeletal System
- Skeletal Muscle
- The Sarcomere
- Following contraction, is calcium pumped into, or out of, the SR?
- The Sarcomere
- Skeletal Muscle
- Contraction occurs when calcium is present
- After contraction is complete, calcium must be actively transported back INTO the sarcoplasmic reticulum and sequestered there until the next contraction.
- The myofibrils are NOT located inside the sarcoplasmic reticulum
- Some students seem to have developed the idea that they were, due to the use of phrases such as: “the sarcoplasmic reticulum surrounds each myofibril.”
- This is true, an extensive network of SR does “wrap around” each myofibril, but the myofibrils are not INSIDE of the sarcoplasmic reticulum.
- Compare this to wrapping your gloved hand around a ball.
- The glove could be said to be “around” the ball, but the ball is clearly not INSIDE of the glove.
- It can be said that the myofibrils are inside of the sarcolemma (i.e., muscle cell membrane) and surrounded by sarcoplasm.
- Immune System
- Describe:
- macrophages
- neutrophils
- eosinophils
- basophils
- mast cells
- Describe:
-
Macrophages
- white blood cells, the mature form of a monocyte.
- They phagocytize (“engulf”):
- pathogens
- cellular debris
- Participate in INNATE IMMUNITY by:
- their non-specific engulfing of foreign material
- Participate in ACQUIRED IMMUNITY by:
- present antigens from the pathogens they consume on their cell membrane,
- which are recognized by B and T cells
-
Neutrophils
- are one of three kinds of granulocytes
- are phagocytes that are recruited to areas of infection and inflammation by chemotaxis.
- They live for only about 5 days, but are the most abundant of all white blood cells.
- The pus created at a wound is mostly dead neutrophils.
-
Eosinophils
-
are recruited to areas of parasitic invasion,
- particularly multicellular parasites
- where they release their granules containing peroxidases and other enzymes that digest tissue.
- This would destroy the pathogen but could also destroy host tissue.
- Note that ALL granulocytes:
- are shortlived and
- do not reside permanently in the tissues.
- circulate in the blood
- are recruited to areas of infection/inflammation.
-
are recruited to areas of parasitic invasion,
-
Eosinophils
Basophils
- are the least common white blood cell.
- Their granules contain mostly histamine
- which they release along with other chemicals when activated.
- These chemicals promote inflammation and are integral in the allergic response
- ∴ many think of basophils as roughly associated with allergies.
-
Mast cells
- contrary to granulocytes, are permanent resident cells within many tissues.
- They are activated by allergens and other antigens to:
- release histamine and
- other chemical mediators.
- They are usually associated with severe allergic reactions
- including anaphylactic shock.
- Immune System
- Acquired Immunity
- Describe Cell-Mediated Immunity
- Acquired Immunity
- INVOLVES T-CELLS (T-Lymphocytes)
- When you see T-cells, THINK of cell-mediated immunity
- T-cells are made in the bone marrow like B-cells, but mature in the thymus.
- T-cells have receptor proteins embedded in their cell membrane.
- Unlike B-cells, they never produce free antibodies.
- Instead, they are “tested” in the thymus against the host’s own membrane proteins (called “self-antigens”)
- All T-cells matching a self-protein are destroyed, leaving only cells that will recognize invaders.
- T-cells that pass this test will differentiate into one of the T-cell types previously described in this lesson.
- Pancreas
- Describe the function of the 6 digestive enzymes it secretes:
- Trypsin
- Chymotrypsin
- Pancreatic amylase
- Lipase
- Ribonuclease
- Deoxyribonuclease
- Describe the function of the 6 digestive enzymes it secretes:
- Trypsin and chymotrypsin
- are both proteases.
- Each enzyme cuts proteins at its own specific amino acid sequence.
- Pancreatic amylase
- catalyzes the hydrolysis of carbohydrates.
- Lipase
- catalyzes the hydrolysis of fats.
- Ribonuclease
- catalyze the hydrolysis of RNA
- Deoxyribonuclease
- catalyzes the hydrolysis of DNA
- Some students find this (ribo & deoxyribonucleases) odd, thinking “Who eats DNA and RNA?”
- While its true we don’t think of either as a food group, anything made of living cells—plant, fungi, animal, etc.–will contain both of these polynucleotides
- Reproductive System
- Sperm
- Ejaculation Pathway
- Describe the specific purpose of each substance secreted into the ejaculate by the seminal vesicles, prostate gland, and bulbourethral gland.
- Ejaculation Pathway
- Sperm
-
Seminal Vesicles
- During ejaculation the first addition to the ejaculate comes from the seminal vesicles.
- They release the majority of the fluids that make up semen
- including fructose and alkaline fluids that make the semen BASIC.
- The alkaline nature of semen
- helps neutralize the acidic environment of the vagina
- fructose
- provides nutrients for the sperm
- The vas deferens continues into the prostate gland, which secretes a milky white fluid that is slightly acidic and contains proteases.
-
Prostate Gland
- The prostate gland secretions play a protective role, as sperm have been shown to have longer survival rates and better protection of their genetic material in the presence of prostate secretions as compared to without them.
- The vas deferens then dumps its contents into the urethra where it passes the bulbourethral glands (a.k.a., Cowper’s glands).
- The bulbourethral glands do not add fluids to the ejaculate at this point.
-
Bulbourethral Gland
- They secrete a fluid called pre-ejaculate that lubricates and neutralizes any acidic urine in the urethra prior to the arrival of the other semen components.
- The term semen refers to the entire ejaculate with all contributed fluids plus the sperm
- Digestive System
- Stomach
- G-cells
- Is gastrin a peptide, a steroid, or a tyrosine derivative?
- Is gastrin likely to bind at a membrane receptor?
- If so, where would you expect that receptor to be located?
- G-cells
- Stomach
- Gastrin is a peptide hormone
- Therefore, we would expect it to be soluble in blood without a carrier molecule and to…
- Require a membrane receptor because it cannot dissolve through the non-polar interior of the bi-layer membrane
- Musculoskeletal System
- Skeletal Muscle anatomy
- Diagram the following:
- fasciculi
- muscle fibers
- sarcolemma
- myofibrils
- sarcomeres
- sarcoplasmic reticulum
- Diagram the following:
- Skeletal Muscle anatomy
- Immune System
- Tissues of the Immune Sys
- Bone Marrow
- Tissues of the Immune Sys
- All erythrocytes and leukocytes are made in the red bone marrow via hematopoiesis
- Yellow bone marrow is primarily adipose tissue and does NOT produce blood cells.
- B lymphocytes mature in the bone marrow
- T lymphocytes migrate to the thymus to mature.
- Immune System
- Acquired Immunity
- WHEN YOU SEE “CELL-MEDIATED” THINK: ?
- WHEN YOU SEE “HUMORAL” THINK: ?
- Acquired Immunity
- WHEN YOU SEE “CELL-MEDIATED” THINK:
- **self-attack of diseased cells **
- WHEN YOU SEE “HUMORAL” THINK:
- antibodies and primary/secondary response
- Integumentary System
- Skin
- Describe the role of skin in thermoregulation
- Skin
- Blood vessels closer to the surface of the skin dilate when heat needs to be released and constrict when heat needs to be retained.
- Blushing is the result of the dilation of these superficial blood vessels.
- Arrector pili muscles cause erection of hair follicles (resulting in “goose bumps”), that traps an insulating layer of air next to the skin
- Contraction of Arrector pili muscles can also generate a small amount of heat.
- Subcutaneous fat provides insulation.
- Sweating, followed by evaporation of that sweat, carries away a significant amount of heat due to the high heat of vaporization of water and its high specific heat capacity.
- Bone
- Functions
- Physical support and movement
- Protection of vital structures
- Mineral storage
- Regulation of:
- blood mineral concentration
- blood cell formation
- Large Intestine
- When you see “Large Intestine,” think:
- “water absorption” or “vitamin absorption”
- In addition to absorbing vitamins from food, the large intestine also absorbs some vitamins produced by beneficial symbiotic E. Coli bacteria that live in the large intestine
- (e.g., vitamin K, thiamin, riboflavin, and B12).
- Musculoskeletal System
- Skeletal Muscle
- What are some important things that skeletal muscle does for the body?
- Skeletal Muscle
- Skeletal muscles store large amounts of glycogen
- They also require a lot of oxygen and thus have THEIR OWN oxygen storage molecule, myoglobin.
- Myoglobin is basically one subunit of a hemoglobin molecule, capable of holding one O2 molecule.
- Mature (differentiated) skeletal muscle cells are frozen in Go phase and do not divide (similar to neurons)
- Bone
- Skeletal Structure
- What is Hydroxyapatite?
- Skeletal Structure
- Hydroxyapatite is an inorganic compound of:
- calcium
- phosphate
- (PO43-)
- hydroxide
- (OH-)
- Is the mineral matrix responsible for a bone’s strength
- Is the form in which most all of the body’s calcium is stored.
- Large Intestine
- The relationship between humans and the E. Coli in the colon is an example of what type of inter-species relationship?
- Mutualism
- Recall that mutualism is a form of symbiosis where both participants benefit.
- The bacteria benefit by consuming the food in our intestines
- We benefit because the bacteria produce vitamins that we absorb.
- Digestion
- Describe
-
Colon (4 parts)
- ascending
- transverse
- descending
- sigmoid
- Rectum
-
Colon (4 parts)
- Describe
-
Colon
- rises upward along the right wall of the abdomen
- ascending colon
- traverses across the abdomen
- transverse colon
- descends along the left wall
- descending colon
- rises upward along the right wall of the abdomen
- The final segment of the colon is somewhat twisted
- sigmoid colon.
- The primary function of the colon is:
- the absorption of water and vitamins.
- The colon contains resident commensal bacteria that secrete:
- vitamin K
- thiamin
- riboflavin
- vitamin B12
-
Rectum
- the final segment of the large intestine
- Functions:
- connects to the anus
- stores feces.
- Liver
- In reponse to high/low glucose levels, the Panc reas secretes what 2 hormones?
- What do they generally do IN THE LIVER?
- How else can the liver produce glucose?
- What is the name of the process when the liver produces new glucose?
- In response to low blood glucose levels alpha cells in the pancreas secrete glucagon.
- Glucagon stimulates glycogenolysis in the liver—the breakdown of glycogen stored in the liver to form free glucose for release into the blood.
- In contrast, high blood glucose levels stimulate beta cells in the pancreas to secrete insulin.
- Insulin stimulates glycogenesis in the liver—the synthesis of glycogen for storage in the liver.
- Insulin also stimulates the uptake of glucose from the blood into the cells.
- Finally, the liver also makes glucose out of lactate, glycerol, amino acids, and some TCA cycle intermediates.
- Liver producing new glucose=GLUCONEOGENESIS
- Digestion
- Describe
- Pepsin
- Small Intestine
- duodenum
- jejunum
- ileum
- Describe
-
Pepsin catalyzes the hydrolysis of proteins.
- The partially digested food mix, now referred to as chyme, passes through the pyloric sphincter and into the upper portion of the small intestine
- called the duodenum.
- The partially digested food mix, now referred to as chyme, passes through the pyloric sphincter and into the upper portion of the small intestine
- The common bile duct and the pancreatic duct both dump into the duodenum.
- As a result, the duodenum receives:
- bile from the liver/gallbladder
- a bicarbonate rich solution
- six digestive enzymes from the pancreas
- As a result, the duodenum receives:
- The chyme progresses through the small intestine to its middle section,
- called the jejunum,
- …and then to the final section,
- called the ileum.
- There are no distinct boundaries marking these three sections
- Most digestion occurs in the duodenum
- most absorption (of food molecules, not water) occurs in the jejunum and ileum
- Immune System
- Acquired Immunity
- Describe Antigen Presentation
- Acquired Immunity
- Antigen presentation
- the process by which a cell that has engulfed an antigen or microbe, (via receptor-mediated endocytosis or phagocytosis) takes protein portions of that microbe or antigen and “presents” them on MHC (Major Histocompatability Complex) proteins embedded in its own cell membrane for other cells to “see.”
- Macrophages, dendritic cells, and B-cells can all “present” antigens
- (Note: Other cells types can also “present” to a small extent, but they do not play a major role in immune system function)
- Bone
- Skeletal Structure
- Name the 4 Bone Types
- Skeletal Structure
- Long bones
- (e.g., femur, humerus)
- Short bones
- (e.g., tarsals, carpals)
- Flat bones
- (i.e., skull, sternum)
- Irregular bones
- (e.g., hip, vertebrae)
- Immune System
- Define Innate Immunity
- The non-specific attack of pathogens.
- All forms of innate immunity are present at birth
- NOT acquired in ANY WAY
- Musculoskeletal System
- Smooth Muscle
- Describe the difference between single unit (a.k.a., “unitary” or “visceral”), and multi-unit smooth muscle types
- Smooth Muscle
-
Unitary (or single-unit) smooth muscle
- is group of smooth muscle fibers that are innervated by a single nerve and contract simultaneously as a single group.
- These are the most common smooth muscle unit
- Are found in :
- most organs
- around most blood vessels
- the digestive tract, etc.
-
Multi-unit smooth muscle
- innervated by multiple nerves and does not act as a single unit.
- This allows for more precise control
- remember, however, that all smooth muscle is involuntary, so it is not conscious control
- This allows for more precise control
- Multi-unit smooth muscle is quite rare.
- It is found in some of the larger vessels such as:
- the aorta
- in the retina of the eye
- It is found in some of the larger vessels such as:
- innervated by multiple nerves and does not act as a single unit.
- Digestive System
- Stomach
- Parietal Cells
- Stomach
- Secrete HCl (into gastric pits/stomach lumen).
- HCl is responsible for the extreme acidity (pH = 2) of the stomach and for the conversion of pepsinogen to pepsin, the ACTIVE FORM of the enzyme.
- Reproductive System
- Menstrual Cycle
- What portion of the menstrual cycle illustrates a positive feedback mechanism?
- Menstrual Cycle
- Around day 14 of the menstrual cycle high estrogen levels stimulate a rapid increase in luteinizing hormone (LH), a good example of a positive feedback mechanism.
- This does not happen during other stages of the cycle where LH stimulates estrogen, and estrogen provides negative feedback to the hypothalamus inhibiting further LH secretion (i.e., classic negative feedback loop).
- However, as mid-cycle approaches estrogen levels provide positive feedback to the hypothalamus, stimulating it to secrete more LH, which in turn stimulates the production of more estrogen.
- This causes the “LH surge,” which results in ovulation.
- Digestive System
- Stomach
- What prevents the tissues lining the stomach from being digested by pepsin?
- Stomach
- The lining cells of the stomach are protected by a thick layer of mucus secreted by the mucus cells that line the gastric pits (one of four cells found there)
- Bone
- Describe the 2 hormones that regulate bone cells.
- Which hormones affect which cells and in what specific ways?
-
CALCITONIN
- Remember that “calcitonin tones your bones.”
- When blood levels are above normal calcitonin inhibits osteoclast activity
- Osteoblast activity continues and thereby a net increase in bone structure results.
- The calcium used by osteoblasts to build new bone matrix comes from the blood
∴ blood calcium levels decrease
-
**PARATHYROID HORMONE (PTH) **
- Parathyroid hormone has the opposite effect
- Parathyroid hormone stimulates osteoclast activity
- resulting in the breakdown of bone matrix and release of calcium into the blood
- As a result, blood calcium levels rise
- Parathyroid hormone stimulates osteoclast activity
- Parathyroid hormone has the opposite effect
- The two hormones also have predictable impacts on the absorption of calcium at the gut and the reabsorption of calcium in the kidney