Tuesday, April 28, 2009

Chapter 43- The Body's Defenses

In innate immunity, recognition and response rely on shared pathogen traits

Innate immune responses include barrier defenses as well as defenses to combat pathogens that end the body

1. Barrier defenses skin and the mucous membranes cover the surface and line the openings of the animal body, and they provide an external barrier against infecting agents

First Line of Defense
Specifically, skin, antimicrobial proteins are in the saliva, cilia lines the lungs to sweep invaders out, gastric juice of the stomach kills most microbes, and symbiotic bacteria in the digestive tract also serve as first line of denfense

Microbes that get through the skin-- for instance, in a cut-- encounter certain types of white blood cells called neutrophils that ingest and destroy them in a process called phagocytosis

Here is a link to a video showing neutrophil phagocytosis


2. Cellular innate defenses combat pathogens that get through the skin-- for example, in a cut. They include phagocytic white blood cells and antimicrobial proteins.

Phagocytic White
Blood Cells
  • Neutrophils are white blood cells that ingest and destroy microbes in a process called phagocytosis
  • Monocytes are another type of phagocytic leukocyte. They migrate into tissues and develop into macrophages, which are giant phagocytic cells
  • Eosinophils are leukocytes that defend against parasitic invaders such as worms by positioning themsleves near the parasite's wall and discharging hydrolytic enzymes

Antimicrobial Prot

Inteferon proteins provide innate defense against viral infections. They cause cells adjacent to injected cells to produce substances to inhibit viral replication

The complement system consists
of roughly 30 proteins with a variety of functions. One function is to lyse invading cells.

The major histocompatibility complex, or MHC, is the mechanism by which the immune system is able to differentiate between self and nonself cells. The MHC is a collection of glycoproteins that exists on the membranes of all body cells.

3. The inflammatory response occ
urs where physical injury occurs to a tissue, and occurs in response to chemical signals (Second line of defense). For example, histamines are released by basophils and most cells (two ypes of leukocytes) in response to injury. Histamines trigger the dilation and permeability of nearby capillaries. This aids in delivering clotting agents (white blood cells) to the injured area. Vasodilation causes redness, and increase in temperature, and and swelling. Histamines cause watery, itchy eyes, and sneezing. We fight histamine reactions with antihistamines.

The third line of defense is the immune response and it differs from the inflammatory response in that it targets specific antigens.

4. Natural Killer (NK) cells help recognize and remove diseased cells

In acquired immunity, lymphocyte receptors provide pathogen- specific recognition

Vertebrates have two types of: B lymphocytes (B cells) which proliferate in the bone marrow, and T lymphocytes (T cells) where lymphocytes mature in the thymus. They circulate through the blood and lymph, and both recognize particular microbes and are said to show specificity.

Antigens are foreign molecules that elicit a response by lymphocytes

Antibodies are proteins secreted by B cells in an immune response. Each anitibody is specific to a particular antigen. There are five classes of anitbodies (or immunoglobins): IgA, IgD, IgE, IgG, IgM.

Antigen receptors are located on the antigen and allow B and T cells to recognize them as antigen receptors on T cells are called T cell receptors, which combat the antigen, and the other consists of memory cells, which are long-lived and bear receptors for the same antigen.

Plasma cells are B cells that release their specific antibodies which then circulate through the body, binding to antigens.

Memory cells are lon-lived B cells that do not release their antibodies in response to the immediate antigen invasion. Instead, the memory cells circulate in the body and respond quickly to eliminate any subsequent invasion by the same antigen. This mechanism provides immunity to many diseases after the first occurence of the disease.

Here is a link to a video about white blood cells, T-cells, NK cells, and cancer cells


Multiple Choice Questions

1. Which if these cells produce and secrete antibodies?

a) macrophages
b) cytotoxic T cells
c) helper T cells
d) bacterial cells
e) plasma cells

2. What kind of white blood cells defend against parasitic invaders?
a) basophils
b) monocytes
c) eosinophils
d) neutrophils
e) histamines

3. ________ proliferate in the bone marrow and ________ mature in the thymus.

a) B cells, T cells
b) NK cells, T cells
c) T cells, B cells
d) B cells, NK cells
e) NK cells, B cells

4. Histamine is secreted by ________.

a) eosinophils
b) monocytes
c) basophils
d) T lymphocytes
e) B lymphocytes

Answers: 1. e, 2. c, 3. a, 4. c

Notes reposted from March 30th, due to technical difficulties with my blog account.

Monday, April 27, 2009

Review: Cellular Respiration

Today in class we did interactive slides on the smart board to start our review for the AP test.
Here are the topics the slides covered:
-sources and sinks
-hydrogen bonds
-the four properties of water:
+cohesion and adhesion (transpiration)
+the fact that water is less dense as a solid than as a liquid
+surface tension
+high speific heat
-modes of selection
-speciation (*a lot of people seemed to need to review this one)
-apoplastic and symplastic routes
-recombinant DNA and vectors
-guttation, xenophytes, C3 C4 and CAM plants
-stages of mitosis
-animal junctions
+tight junction
+gap junction
-plant junctions
-monomers, polymers, and bonds
-the structure of a protein

I, personally, feel that I need to brush up on CELLULAR RESPIRATION. Here is a quick review. Hopefully it helps everyone out!

Cellular respiration is the breakdown of sugars that occurs in teh presence of oxygen. Carbohydrates, fats, and proteins can all be broken down to release energy in cellular repsiration. However, glucose is the primary nutrient fuel molecule that is used in cellular respiration to release energy.

Below is the standard equation for cellular respiration:
C6H12O6 + O2CO2 + H2O + Energy (as ATP)

Cellular respiration is aerobic respiration (oxygen is present).
Glycolysis is the first process in cellular respiration:
Glycolysis is the decomposition of glucose to two pyruvate molecules. The 6-carbon glucose molecule is split into two 3-carbon sugars through a long series of steps.

There is an ATP consuming phase and an ATP producing phase.
First, 2 ATP are consumed. In the next phase, 4 ATP are produced as well as 2 NADH. The net gain of ATP is 2.
*NADG is a conenzyme that forms when NAD+ combines with two energy-rich electrons and H+.

The Krebs Cycle is the second process:
It occurs in the mitochondrial matrix. In it, glucose is completely broken down and the final product is CO2.
The cycle has 8 steps, and each is catalyzed by a different enzyme:
1. Acetyl CoA adds iots two-carbon acetyl group to oxoaloacetate, producing citrate.
2. Citrate is converted to its isomer, isocitrate, by removal of one water molecule and addition of another.
3. Isocitrate is oxidized, reducing NAD+ to NADH. Then the resultinf compound loses a CO2 molecule.
4. Another CO2 is lostm and the resulting compound is oxidized, reducing NAD+ to NADH. THe remaining molecule is then attached to coenzyme A by an unstable bond.
5. CoA is displaced by a phosphate group, which is transferred to GDP, forming GTP, a molecule with functions similar to ATP.
6. Two hydrogens are transferred to FAD, forming FADH2 and oxidizing succinate.
7. Addition of a water molecule rearranges bonds in the substrate.
8. The substrate is oxidized, reducing NAD+ to NADH and regenerating oxaloacetate.

Each cycling requires the input of a 2-carbon acetyl co-a molecule, and two carbons are released in the course of the cyle as CO2.
For every 1 turn of the cycle, the net results are:
2 CO2

For every 2 turns of the cylce, the net results are:
4 CO2
**Both glycolysis and the Krebs Cycle are substrate level phosphorylation. This means that a phosphate group and its associated energy is transferred to ADP to from ATP. The substrate molecule (the one with the phosphate group) donates the high energy phosphate group.

Oxidative phosphorylation is the last process of the cellular respiration:
Oxidative phosphorylation is the process of extracting ATP from NADH and FADH2. Electrons from NADH and FADH2 pass along an electron transport chain.

The electron transport chain consists of molecules (mainly proteins) embedded in teh inner mitochondrial membrane. Sitting on top of these proteins embedded in the membrane are associated molecules that are alternately reduced and oxidized as the accept and donate electrons.
* In oxidation, electrons are loast. In reduction, they are added.

The first electron acceptor in the ETC is a flavoprotein called flavin mononucleotide (FMN) and it accepts and electron from NADH.
The electron is passd down a series of molecules to oxygen, the final electron acceptor. Then, it is combined with hydrogen atoms to form water.
*FADH2 and NADH both donate electrons in the chain

The ETC does not make any ATP itself. Its reactions are coupled to others to make ATP in chemiosmosis.

In chemiosmosis, a hydrogen pump pumps H+ ions against their concentration gradient across the mitochondrial membrane. This creates a proton gradient. Protein complexes called ATP synthases embedded in the membrane use the energy from the proton gradient. The H+ ions flow back into the mitochondrial matrix through the ATP synthase. The flow drives the oxidative phosphorylation of ADP to ATP. Oxidative phosphorylation results in about 34 ATP molecules.

This makes the total number of ATP produced by cellular respiration about 38.

To sum it up, here are the products of each step of cellular respiration:



KREB'S CYCLE: 2 net ATP, 6 NADH, 2 FADH2, 4 CO2
* Here is a really good video that Mrs. Lyon showed us in class when we first learned cellular respiration: http://www.youtube.com/watch?v=Biq1xo-1eyo&feature=related.
1. Which of the following sequences correctly indicates the potential ATP yield of the indicated molecules from greatest ATP yield to least ATP yield?
a) Pyruvate, ethanol, glucose, acetyl CoA
b) Glucose, pyruvate, acetyl CoA, NADH
c) Glucose, pyruvate, NADH, acetyl CoA
d) Glucose, FADH2, acetyl CoA, pyruvate
e) Glucose, FADH2, NADH, pyruvate
2. Cells do not catabolize carbon dioxide because
a) its double bonds are too stable to be broken
b) CO2 has fewer bonding electrons than other organic compounds
c) CO2 is already completely reduced
d) CO2 is already completely oxidized
e) the molecule has too few atoms
3. In mitochondria, exergonic redox reactions
a) are the source of energy driving projaryotic ATP synthesis
b) are directly coupled ot substrate-level phosphorylation
c) provide the energy that establishes the proton gradient
d) reduce carbon atoms to carbon dioxide
e) are coupled via phosphorylated intermediates to endergonic processes
4. When electrons flow along the electron transport chains of mitochondria, which of the following changes occurs?
a) the pH of the matrix increases
b) ATP synthase pumps protons by active transport
c) the electrons gain free energy
d) the cytochromes phosphorylate ADP to form ATP
e) NAD+ is oxidized
5. The final electron acceptor of the ETC that functions in aerobic oxidative phosphorylation is
a) oxygen
b) water
c) NAD+
d) pyruvate
e) ADP
1- B
2- D
3- C
4- A
5- A
This Week:
Review, review, and more review.
Remember: Chapter 50 take home is due Friday.
Only 2 more weeks until the exam! Keep up the hard work!

Sunday, April 26, 2009

The End (of Chapter 50)

Alright girls, here are the final notes!

Chemoreception – Taste and Smell
Taste buds are modified epithelial cells situated on different parts of the tongue and mouth

Movement and Locomotion

Locomotion is the movement from place to place.
Hydrostatic skeletons consist of fluid held under pressure in a closed body compartment
Exoskeletons are hard encasements on the surface of an animal, such as is found in the grasshopper. Endoskeletons consist of hard supporting elements buried within the soft tissues of an animals. Ex: the human body skeleton
http://www.cartage.org.lb/en/themes/sciences/LifeScience/GeneralBiology/Physiology/TheBones/MuscularSkeletal/exoskel.gif http://affordablehousinginstitute.org/blogs/us/wp-content/uploads/imageshuman-endoskeleton-small.jpg

Skeletal muscles are attached to bones and responsible for the movement of bones they consist of long fibers, each of which is a single muscle cell. A muscle fiber is a bundle of myofibrils which are composed of myofilaments called actin (thin filaments) and myosin (thick filaments).
The sarcomere is the basic contractile unit of the muscle. Z lines make up the border of the sarcomere. The I band is the area near the end of the sarcomere where only thin filaments exists. The A band is the entire length of the thick filaments.
Muscle contraction occurs when the length of the sarcomere is reduced.
There are two different types of muscle fibers: fast-twitch muscle fibers, which are used for fast, powerful contractions and slow-twitch muscle fibers, which are used for slow, long-lasting contractions
The sliding filament model states that the thick and thin filaments slide past each other so that their degree of overlap increases. This is dependent on the interaction between the actin and myosin molecules that make up the thin and thick filaments
Muscle cells contract when stimulated by a motor neuron.
In the first stage of muscle contraction, muscle contraction is stimulated by an action potential in a motor neuron that makes as synaptic connection with the muscle cell releases acetylcholine at the neuromuscular junction. This depolarizes the muscle cell and triggers the action potential.
In the second stage of muscle contraction, the action potential spreads along T tubules (transverse tubules); changes the permeability of the sarcoplasmic reticulum to calcium ions, and the newly released calcium ions bind to troponin and cause it to move, exposing the myosin sites on the actin; the muscle contracts.

The End

Review Questions:
1. All of the following are involved in the contraction of muscle cells EXCEPT:
a) actin
b) cAMP
c) mysoin
d) tropomyosin
e) troponin

2. Muscle cells are stimulated by neurotransmitters released from the tips of
A) T tubules
B) motor cell axons
C) motor cell dendrites
D) sensory cell dendrites
E) sensory cell axons

3. Which of the following does not form part of the thin filaments of a muscle cell?
a) tropomyosin
b) calcium-binding site
c) troponin
d) myosin
e) actin

1. b
2. b
3. d

Don't forget that the chapter 49 and 50 take home quiz is due on Friday!

We only have two weeks left until the AP Exam so it's time to start reviewing. . . Remember, about 25% of the exam will be on Molecular and Cellular Biology (Chemistry of Life, Cells, Cellular Energy), about 25% will be on Genetics and Evolution (Heredity, Molecular Genetics, Evolutionary Biology) and about 50% will be on Organisms and Populations (Structure and Function of Plants and Animals, Ecology, Taxonomy of Organisms).

Friday, April 24, 2009

CHAPTER 50: Sensory and Motor Mechanisms

Hello AP Bio, These are yesterdays (Thursdays) notes. It's not a lot we kinda ran through them pretty fast. Mrs. Lyon will go more into depth today.
are receptors stimulated by physical stimuli, such as pressure, touch, stretch, motion, or sound
Thermoreceptors respond to either heat or cold and help maintain body temperature by keeping the core temperature stable.

Chemoreceptors transmit information about solute concentration in a solution. Gustatory (taste) receptors and olfactory (smell) receptors are two types of chemoreceptors.

Photoreceptors and Vision

Compound Eyes (in insects and crustaceans) consist of up to several thousand light detectors called ommatidia, each of which has its own lens.

Single-lens eyes are found in vertebrates and some invertebrates.

The eyeball in single-lens eyes is made up of two outer layers, the sclera (which in the front of the eye is the cornea-responsible for acting as a lens) and the choroid. The eyeball also contains the pupil, which is the hole in the center of the iris, and the retina, which contains the photoreceptor cells.

The sclera is an extension of the cornea.
Aqueous humor fills the anterior cavity of the eye, and the vitreous humor fills the posterior cavity of the eye.

The retina contains rod cells and cone cells, two types of photoreceptors.

Rhodopsin is the light-absorbing pigment that triggers a signal transduction pathway that ultimately leads to sight.

Identify the part of a single-lens eye with this link:

Hearing and Equilibrium

There are three regions in the mammalian ear.

1. The outer ear, which is the external pinna and auditory canal. These collect sounds and bring them to the tympanic membrane (eardrum), which separates the outer ear from the middle ear.

2. The middle ear, in which vibrations are conducted through three small bones collectively called ossicles (individually, the malleus, incus, and stapes) and through the oval window.

3. Then the vibrations are conducted to the inner ear, which consists of a labyrinth of channels lined by membrane and containing fluid, all situated in bone.

The inner ear contains the cochlea, a two-chambered organ, which is involved in hearing.

The organ of Corti, which is in the cochlea, contains the receptors of the ear, which are hair cells with hairs that project into the cochlear duct.

The cochlea transduces the energy of the vibrating fluid into action potentials, in a wave that dissipates at the round window.

Some organs in the inner ear are responsible for detecting body position and balance. These are the semicircular canals.

~Quick Quiz~
1. The Ossicles in the ear contain three bones. What are they called?
a. the malleus, incus, and staple
b. the incas, mallus, and stapes
c. the malleus, incus, and stapes
d. the stepes, incas, and mallous

2. What part of the ear gives us balance?
a. semicircular canal
b. the pinna
c. the malleus
d. the incus

3. Which part of the eye reacts to color?
a. cornea
b. rod cell
c. rhodopsin
d. cone cell

answers: c,a,d

Wednesday, April 22, 2009

Sensory and Motor Mechanisms

Hello children of AP Biology-
Today both blocks went over the most recent packet (chapters 46 through 48 I believe). Then, B, I think you guys started chapter 50. Ms. Lyon decided she was done teaching C block shortly after the packet, so we did nothing else. I'm assuming chapter 50 is one of our last... ah the beginning of the end. I'm just going to give everyone a quick overview of it. Also, chapter 50 vocabulary quiz is tomorrow as I'm sure you knew. Meghan kindly posted all the words yesterday, so I'll just pick several for a short quiz at the end. STUDY UP!

Chapter 50: Sensory and Motor Mechanisms
section 50.1
-basically, your body has two parts to its nervous system: the PNS and CNS
-the PNS is the peripheral nervous system (everything but the brain and spinal column): sensory reception occurs in this system
-a sensory receptor (made of specialized neurons or epithelial cells) detect stimuli--either internal or ext
-the receptor converts the stimulus energy to a change in t
he membrane potential of that receptor (look back at the action potential graph)
-this stimulus signal is passed along through action po
tentials to the CNS: the central nervous system (consisting of your spinal column and brain)
-the brain now goes through a process called PERCEPTION: it understands what is happening (the sound, smell, etc.)
-the signal is amplified and then the receptor cell either produces action potentials or releases a neurotransmitter
-there are numerous types of chemoreceptors (detect solute concentrations), mechanoreceptors (pressure, touch, stretch, motion, sound), electromagnetic receptors (electromagnetic radiation), thermoreceptors (temperature), and pain receptors

Alright guys, there's a baby intro to chapter 50. Here is a quiz over a few of the words for the vocab quiz tomorrow.

1. The broad region that corresponds to the length of the thick filaments of microfibrils is __________.
a) Z Line
b) A Band
c) I Band

2. The photoreceptor in the vertebrate eye that detects color during the day is _________.
a) Cone Cell
b) Trypomyosin
c) Rod Cell

3. A type of mechanoreceptor that detects sound waves and other forms of movement in air and water is _________.
a) Rhodopsin
b) Thin Filament
c) Hair Cell

Answers: (1) B (2) A (3) C

Good luck on the quiz! 


Hey sorry I forgot to post this last night... but here are the potential bio shirts morgan and I designed. If you have any suggestions for changes, just post them as a response to this, and I'll get on it asap. I think all of C block is getting them. If anyone from B block wants one let me know.

CLICK HERE to take a gander.

Tuesday, April 21, 2009

Nervous System

Hi ladies! Sorry for posting this so late. Don't forget that ch 50 is due tomorrow, the ch 46-48 take home is due tomorrow, and we have a ch 48/49 vocab quiz. IT'S ALSO LATE START! :)

Today in C block Lindsey showed us the awesome design for the AP Bio t-shirt. They are really cute and everyone should get one! She's going to post the link on the blog so that B block can see the shirts, too. We also took a vocab quiz and took more notes on the nervous system.

Chapter 50 Vocab:
Cardiac muscle
a type of muscle that forms the contractile wall of the heart. Its cells are joined by intercalated disks that relay each heartbeat

sarcoplasmic reticulum
a specialized endoplasmic reticulum that regulates the calcium concentration in the cytosol

Z lines
The borders of a sacromere

the regulatory protein that blocks the myosin-binding sites on the actin molecules

A band
the broad region that corresponds to the length of the thick filaments of myofibrils

I band
The area near the edge of the sacromere where there are only thin filaments

the fundamental, repeating unit of striated muscle, deliminated
By the Z lines

Cone cell
one of two types of photoreceptors in the vertebrate eye; detects color during the day

thick filament
a filament composed of staggered arrays of myosin molecules; a component of myofibrils in muscle fibers

Hydrostatic skeleton
a skeletal system composed of fluid held under pressure in a closed body compartment; the main skeleton of most cnidarians, flatworms, nematods, and annelids

rod cell
one of two kinds of photoreceptors in the vertebrate retina; sensitive to black and white and enables night vision

thin filament
the smaller of the two myofilaments consisting of two strands of actin and two strands of regulatory protein coiled around one another

the thick and thin filaments that form the myofibrils

Hair cell
a type of mechanoreceptor that detects sound waves and other forms of movement in air or water

a visual pigment consisting of retinal and opsin. When rhodopsin absorbs light, the retinal changes shape and dissociates from the opsin, after which it is converted back to its original form

the strengthening of stimulus energy that is otherwise too weak to be carried into the nervous system
pic n/a

A class of naked dendrites in the epidermis of the skin

a sensory receptor that detects stimuli within the body, such as blood pressure and body position

tympan-a drum
sacc-a sack
omma-the eye
mechano-an instrument
coch- a snail
utric- a leather bag
fovea- a pit
Graph from class:

This is an action potential graph. An action potential or impulse can only be generated in the axon of a neuron. When the neruon is stimulated the sodium channels open and sodium ions flood into the cell. As a response, potassium channels open allowing potassium ions to leave the cell. This rapid movement (the upward line in the graph) is called depolarization. As you can tell, this lasts a very short amount of time. The potassium pump respores the membrane to its original polarized condition by pumping sodium and potassium ions back to their original location. This period is called repolarization. When the potential drops back down it goes through short period of time called the refractory period during which the neuron can't respond to another stimulus. Once the potential levels out, the neuron has reached it's resting state.
Questions from Ch 46-48 Take Home
1) Genetic mutations in asexually reproducing organisms lead to more evolutionary change than do genetic mutations in sexually reproducing ones because
A) asexually reproducing organisms, but not sexually reproducing organisms, pass mutations to their offspring
B) More genetic variation is present in organisms that reproduce asexually than is present in those that reproduce sexually
C) sexually reproducing organisms can produce more offspring in a given time than can sexually reproducing organisms
D) asexually reproducing organisms devote more time and energy to the process of reproduction than do sexually reproducing organisms
E) asexually reproducing organisms have more dominant genes than organisms that reproduce sexually
2) The Small portion of the embryo that will become its dorsal side develops from
A) morula
B) primitive streak
C) gray crescent
D) blastocoel
E) archenteron
3) Action potentials move along axons
A) by reversing the concentration gradients for sodium and potassium ions
B) more rapidly in myelinated than in non-myelinated axons
C) by the direct action of acetylcholine on the axonal membrane
D) by activating the sodium-potassium "pump" at each point along the axonal membrane
E) more slowly in axons of large than in small diameter
Answers: 1) A 2) C 3)A

Related FRQ


FRQ grading key

Beginning Ch. 48

An overview of the Nervous System

Sensory receptors collect information about the world outside the body as well as proscess information inside the body.

The Central Nervous System consists of the brain and the spinal cord. The conduction of signals from the central nervous system (CNS) to the effector cells is called motor output. Effector cells are target cells that produce some sort of response. They are generally gland or muscel cells.

The Peripheral Nervous System (PNS) consists of the nerves that commonicate motor and sensory signals in and out of the CNS. This reaches throughout the rest of the body. The PNS is divided into 2 groups

  • Somatic nervous system- directs contraction of muscles

  • Autonomic nervous system- controls organs and various involuntary muscles. broken into 2 parts

  1. Sympathetic nervous system- involved in stimulation of activities that ready the body for action (for example increasing heart rate)

  2. Parasympathetic nervous system- activates tranquil functions (stimulating secretion of saliva)

The Neuron is the functional unit of the nervous system. They are nerce cells. Neurons consist of 3 parts.

  • Cell body- contaqins the nucleus and other organelles

  • Dendrites- typically short, abundantly branched cell extensions that recieve incoming messages from other neurons

  • Axon- a single , long, slim extension of the cell body that sends nerve impulses. Covering most axons is a myelin sheath which insulates and protects it. At the end of an axon is a synaptic terminal which transmits signals to other neurons via neurotransmitters, or chemical messengers

There are 3 groups that neurons are classified in:
  1. Sensory neurons- recieve initial stimulus Ex. those in the hand stimulated by touch
  2. Motor neurons- stimulate effector cells Ex. those stimulating sweat glands to cool the body
  3. Association neurons- located in the spinal cord or brain to recieve impulses from sensory neurons or send impulses to motor neurons. (aka interneurons)

The transmitting neuron is called the presynaptic cell and the recieving neuron is called the postsynaptic cell. Ganglia are clusters of nerve cells.

Reflex arc- a rapid involuntary response to a stimulus in which a sensory nerve recieves information and passes it along to the spinal cord and then to a motor neuron, which signals an effector cell.

Glial cells are support cells. They are necessary for the proper functioning of nerve cells, and perform different functions depending on the type of glial cell.

  • Astrocytes- provide support for neurons

  • Oligodgendrocytes- form myelin sheaths around axons in the CNS

  • Schwann Cells- form myelin sheaths around axons in the PNS

1. What are the basic building blocks of the brain?

A. brain cells

B. neurons

C. neurotransmitters

D. axons

2. What is most likely to be found in a synapse?

A. cells

B. neuron

C. neurotransmitters

3. Which is/ are true?

A. a neuron doesn't go through the cell cycle

B. a nephron transmits signals throughout the body

C. the 'fight or flight' response is atributed to the sympathetic nervous system

D. A & C

1. B ; 2. C ; 3. D

Thursday, April 16, 2009

End of 46 and Beginning of 47

End of 46
The egg cell is released into the oviduct, or fallopian tube, and cilia lining the fallopian tube convey the egg cell down to the uterus. The inner lining of the uterus is called the endometrium.

At the base of the uterus is cervix, which leads to the vagina, the canal through which a baby is born.

Spermatogenesis is the production of mature sperm cells, and it occurs in the seminiferous tubules. The cells that give rise to sperm are called spermatogonia. They undergo meiosis and differentiation eventually to form mature, motile sperm.

The head of the sperm is tipped with an acrosome, which secretes enzymes that help the sperm penetrate the egg.

Oogenesis is the development of mature ova. Oogonia are the cells that develop into ova; they multiply and begin meiosis, but they stop at prophase I of meiosis I. These egg cells are called primary oocytes, which are quiescent until puberty. From puberty onward, FSH periodically stimulates a follicle to grow and its egg cell to complete meiosis I and begin meiosis II. This forms the secondary oocyte.

At birth, a female’s ovaries contain about 1 million follicles, each with an ovum that has begun meiosis but is arrested in Prophase I of the first meiotic division.

At this stage, the ova are called primary ooctes. Some of these primary oocyte-containing follicles are stimulated to develop during each cycle.

During each follicular phase several follicles are stimulated to grow under FSH stimulation, but only be achieves full maturity as a tertiary, or Graafian, follicle by ovulation.

Graafian follicle

The primary oocyte completes the meiotic division during the follicular phase. Instead of forming two equally large daughter cells, however, it produces one large daughter cell, the secondary oocyte, and one tiny daughter cell, called a polar body.

Polar body formation

Thus the secondary oocyte acquires almost all of the cytoplasm from the primary oocyte (unequal cytokinesis), increasing its chances of sustaining the early embryo should the oocyte be fertilized.

The polar body disintegrates and the secondary oocyte then begins the second meiotic division, but its progress is arrested at Metaphase II. It is in this form that the egg cell is discharged from the ovary at ovulation, and it does not complete the second meiotic division unless it becomes fertilized in the fallopian tube.

Humans and other primates have menstrual cycles, and other mammals have estrous cycles. Menstruation occurs when the endometrium is shed from the uterus through the cervix and vagina.

The menstruation flow phase of the female cycle is the phase during which menstruation bleeding occurs.

The proliferative phase of the menstrual cycle is that during which the endometrium begins to regenerate and thicken.

In secretory phase, the endometrium continues to thicken, and is the embryo has not implanted in the lining by the end of this phase, menstruation flow occurs.

The ovarian cycle parallels the menstrual flow cycle, and begins with the follicular phase, in which several follicles begin to grow.

At the end of the follicular phase, ovulation occurs, during which the secondary oocycte is released from the ovary.

During the luteal phase of the ovarian cycle, endocrine walls in the corpus luteum secrete hormones.

Pregnancy (gestation) is the condition of carrying at least one embryo.

Start of 47 Animal Development

Animal Development: The stages of early embryonic development
After fertilization, there are three successive stages in early development

1. Cleavage which is a period of rapid mitotic cell division, partitions the cytoplasm of the zygote into smaller cells called blastomeres each which has its own nucleus.

Continued cleavage leads to a ball of cells called a morula, and then a fluid-filed central cavity called the blastocoel forms within the morula to produce a blastula.

2. Gastrulation is a drastic rearrangement of the cells in the blastula. In gastrulation, three (germ) cell layers are produced—ectoderm (later forms the nervous system and outer layer of skin). The endoderm (later develops to line the digestive tract). The mesoderm (later develops into most organs and tissues).

Multiple Choice Questions:

1. Storage and maturation of human sperm occur in the
A. Epididymis
B. interstitial cells
C. seminiferous tubules
D. sertoli cells
E. vas deferons

2. The function of the acrosome in the sperm head is to
A. provide ATP for flagellar movements
B. control DNA replication in the sperm
C. store enzymes used for penetrating the egg during fertilization
D. enclose the genetic material
E. provide a sharp head of the sperm to penetrate the egg

3. The dorsal lip of the blastopore induces development of the
A. trophoblast
B. mesoderm germ layer
C. mouth in deuterostomes
D. coelom
E. notochord

Answers: 1. A, 2. C , 3. E

Wednesday, April 15, 2009

Practice FRQ's

Hello fellow students of biology!
I found some sites that have practice FRQ's for the exam. Hope they help! :)
Video: http://videos.howstuffworks.com/hsw/24727-animal-reproduction-the-fertilization-of-an-egg-video.htm

Chapter 46

Mechanisms of Sexual Reproduction

Mechanisms of Sexual Reproduction

Fertilization is the union of sperm and egg

External fertilization occurs when eggs are shed by the female and fertilized by the male outside the female's body

Internal fertilization occurs when sperm are deposited in the female reproductive tract and fertilization occurs within the tract

Gonads are the organs that produce gametes in most animals

Mammalian Reproduction

The Male:

The male's external reproductive organs are the scrotum and penis, and the internal organs are gonads (which produce gametes and hormones), accessory glands (which secrete necessary fluids), and ducts (which carry sperm and glandular secretions).

The testes are made up of many highly coiled tubules surrounded by connective tissue. The tubules are seminiferous tubules, the sites of sperm production. In between the tubules are Leydig cells, which produce testosterone and other androgens.

The testes are held in the scrotum (equivalent to the female labia majora), which is located outside the lower abdominal pelvic cavity

The sperm from the seminiferous tubules into the epididymis (where it is stored). During ejaculation, the sperm is propelled through the vas deferens, which ultimately meets up w/a duct from the seminal vesicle and forms an ejaculatory duct, which opens into the urethra (which serves as an excretory and reproductive duct)

The seminal vesicles, the prostate gland, and the bulbourethral gland all contribute secretions to create semen. These secretions which are usually alkaline supply necessary nutrients and a medium for the sperm cells

The penis is composed of three masses of spongy tissue derived from modified veins and capillaries

The Female:

The female gonads are the two ovaries. Each ovary contains many microscopic follicles. The ovaries secrete estrogen and progesterone

Follicles consist of one egg surrounded by one or more layers of follicle cells, which help to develop, nourish, and protect the egg cell. All of the follicles a woman has are formed before her birth. One follicle matures and releases its egg cell during each menstrual cycle

The follicle cells also produce estrogens, the female hormones

The egg cell is released from the follicle during ovulation. The remaining follicle tissue heals and grows in the ovary to form a body called a corpus luteum. This secretes estrogens and progesterone. Progesterone helps to maintain the uterine wall during pregnancy. If the egg cell isn't fertilized, the corpus luteum disintegrates

Multiple Choice Questions:

1. Why is sexual reproduction important?
A) It can result in numerous offspring in a short amount of time.
B) The resulting diverse phenotypes may enhance survival of a population in a changing environment.
C) It allows animals to conserve resources and reproduce only during optimal conditions.
D) It enables isolated animals to colonize a habitat rapidly.
E) Both A and D are important.

2. Which of the following is not required for internal fertilization?
A) internal development of the embryo
B) copulatory organ
C) sperm receptacle
D) behavioral interaction
E) All of the above are necessary for internal fertilization.

3. Why is internal fertilization considered more advantageous than external fertilization?
A) Usually fewer offspring are produced, so ample food supply is available.
B) The increased survival rate results in rapid population increases.
C) The smaller number of offspring often receive a greater amount of parental protection.
D) Usually a smaller number of genes are present, which promotes genetic stability.
E) The time and energy devoted to reproduction is decreased.

4. Internal and external fertilization both
A) produce a zygote.
B) occur in vertebrates.
C) occur in eutherian animals.
D) A and B only are correct.
E) A and C only are correct.

5. Which reproductive method is the most prevalent in mammals?

A) fragmentation

B) budding

C) regeneration

D) external fertilization

E) internal fertilization

6. The _______is (are) the site of testosterone production in the testis

A) seminiferous tubules

B) epididymis

C) Leydig cells

D) seminal vesicle

E) prostate gland

7. Which structure is part of the excretory and reproductive systems in males?

A) Ureter

B) Urethra

C) Seminal vesicle

D) Urinary bladder

E) Vas deferens


1. B 2. A 3. C 4.D 5.E 6. C 7.B