Anatomy 8-18-26

Anatomy and Physiology, Grades 11 and 12

Feedback Review and the Structure of the Cell

Module 1  |  Reading: pages 11 to 13  |  40 Minutes  |  Mr. Gibbs

At a Glance

• 0:00 to 0:04  Feedback review, rapid

• 0:04 to 0:12  Build the Loop handouts returned and corrected

• 0:12 to 0:36  The structure of the cell, refresher lecture

• 0:36 to 0:40  Close and reading assignment

Materials: whiteboard, graded Build the Loop handouts, a cell diagram projected or on the board. This is review from Biology, so pace it accordingly.

1. Feedback Review

4 minutes. Rapid, cold call, no board work.

• Define homeostasis in one sentence. Push back if anyone says constant rather than relatively stable.

• Name the six components of a control system in order.

• What does negative feedback do to the stimulus? What does positive feedback do?

• Why can a positive feedback loop not end itself?

• One synthesis question: why is the variable never exactly at the set point? Because correction cannot start until deviation is detected.

2. Build the Loop Handouts, Returned and Corrected

8 minutes. Hand papers back first, then work through the errors as a class. Students correct their own in a different color.

• Set the expectation: they are correcting, not just receiving. Anything left blank or wrong gets fixed on the page before it goes in the binder.

The four errors to address, in this order

• Error 1, the blank or duplicated control center. This is the most common by a wide margin. Students name the effector twice and leave the integrating center empty. Ask the room what a control center actually does, and get to three things: it holds the set point, it compares the actual value to it, and it issues the command.

• Error 2, the glucose scenarios. Pairs with scenarios C and D either left boxes blank or wrote pancreas three times. Both are defensible. Explain again that a pancreatic beta cell senses glucose, integrates, and secretes insulin, so receptor, control center, and effector are the same cell. The six component model is a framework, not an anatomical requirement.

• Error 3, response versus effector. The effector is the structure. The response is what it does. Sweat gland is an effector, sweating is the response. Students routinely write the same thing in both boxes.

• Error 4, the clotting justification. Ask a pair with scenario F to read what they wrote. Correct justification names what the response does to the stimulus: each activated platelet activates more, so the response increases the original signal. Then ask for the terminating event, which is the vessel being sealed.

• Close the review with the fever question again, verbally: a febrile patient shivers while already hot. Negative feedback defending a raised set point. Ask whether anyone has changed their mind since last class.

Do not spend more than eight minutes here. If several pairs have deeper confusion, note it and address it during the next quiz review rather than sacrificing the cell material, which they need before the reading.

3. The Structure of the Cell

24 minutes. This is refresher, not first teaching. Move briskly, ask more than you tell, and use their Biology knowledge as the starting point.

• Open by putting the course principle back on the board: structure determines function. Tell them that today they are going to see it at the smallest scale in the course, and that every organelle on the list is a shape built for a job.

• Set the frame so this is not a list: group the organelles by what they do. Control. Manufacturing. Processing and shipping. Power. Movement and division. Write those five headings on the board and fill them in as you go.

• Ask before you begin, to gauge the room: "Which of these do you actually remember from Biology?" Adjust your pacing to the answer.

Cytoplasm  (2 min)

• Everything between the plasma membrane and the nuclear envelope. Cytosol is the fluid, and the organelles sit in it.

• Name the cytoskeleton here, briefly: microfilaments, intermediate filaments, and microtubules. It gives the cell shape, anchors organelles, and provides tracks for movement. Microtubules matter later today for centrioles and cilia.

• One functional note worth keeping: glycolysis happens here, in the cytosol, not in an organelle. That becomes relevant when you compare it to what mitochondria do.

Nucleus  (3 min)  — Control

• The control center. Houses DNA and directs essentially everything the cell does by determining which proteins get made.

• Nuclear envelope is a double membrane, perforated by nuclear pores. DNA does not leave. Messenger RNA does.

• Nucleolus is a dense region inside where ribosomal subunits are assembled.

• Chromatin is the uncoiled working form of DNA. It condenses into chromosomes only for division.

• Two exceptions worth naming, since both come back later: a mature red blood cell has ejected its nucleus, which is why it cannot repair itself and lasts about 120 days. A skeletal muscle fiber is multinucleate, because it forms from many cells fusing.

Ribosomes, RER, and SER  (7 min)  — Manufacturing

• Ribosomes: the site of protein synthesis. Made of ribosomal RNA and protein, assembled in the nucleolus. Note they have no membrane, which makes them unusual on this list.

• The distinction that matters: free ribosomes floating in the cytosol make proteins the cell will use itself. Ribosomes bound to the rough ER make proteins destined for export, for the membrane, or for lysosomes. Same machine, different destination.

• Rough ER: continuous with the nuclear envelope, studded with ribosomes, which is what makes it rough. Proteins enter its interior, get folded and checked, and leave in transport vesicles. It also manufactures membrane.

• Where it is abundant, and this is the structure to function argument: cells that secrete large amounts of protein are packed with it. Pancreatic acinar cells making digestive enzymes. Plasma cells making antibodies. Ask them what they would expect to find inside a cell whose whole job is export.

• Smooth ER: no ribosomes, and a different set of jobs entirely. Lipid and steroid synthesis, detoxification, and calcium storage.

• Give one example for each job, because the SER is where students are weakest: the adrenal cortex and gonads are rich in SER because they synthesize steroid hormones. Liver hepatocytes are rich in it because they detoxify drugs and alcohol, and chronic exposure increases the amount of SER, which is one mechanism behind drug tolerance.

• Flag the preview explicitly: in muscle cells the smooth ER is called sarcoplasmic reticulum and its job is storing and releasing calcium. That release is what triggers contraction. Tell them to remember this, because Modules 4 and 5 depend on it.

Golgi apparatus  (2 min)  — Processing and shipping

• Stacked flattened membranous sacs. Receives vesicles from the ER at the cis face, modifies and sorts the contents, and ships from the trans face.

• Three destinations: secreted from the cell, inserted into the plasma membrane, or packaged as lysosomes.

• The useful comparison: the ER manufactures and the Golgi finishes, labels, and addresses. Ask which one you would expect to be enlarged in a cell that secretes heavily. Both.

Mitochondria  (3 min)  — Power

• Site of aerobic cellular respiration and the great majority of ATP production.

• Double membrane. The inner membrane folds into cristae, which multiply the surface area available for the reactions. Ask why surface area matters here and let them answer.

• Contains its own DNA and ribosomes and replicates independently of the cell. Mitochondrial DNA is inherited maternally.

• The structure to function payoff: mitochondrial density tracks energy demand. Cardiac muscle, skeletal muscle, and liver cells are dense with them. Ask which cell in the body they would expect to have the most, and why the heart is the obvious answer.

Centrioles and cilia  (4 min)  — Movement and division

• Centrioles: paired cylinders oriented perpendicular to each other, built from nine triplets of microtubules, sitting in the centrosome near the nucleus.

• They organize the mitotic spindle during cell division, and they serve as basal bodies that anchor and generate cilia and flagella.

• Cilia: short, numerous, motile projections built from microtubules in the nine plus two arrangement. They beat in coordinated waves to move material across a cell surface.

• Two locations to name: respiratory epithelium, where cilia move a mucus sheet upward and out, and the uterine tube, where they move the oocyte toward the uterus.

• The clinical hook, and this one lands: the mucociliary escalator clears trapped debris continuously. Smoking paralyzes and eventually destroys the cilia, so the mucus is no longer moved and the person has to clear it by force. That is a smoker’s cough, and it is a direct consequence of losing an organelle.

• Distinguish from flagella in one line: same basic construction, but long and typically one per cell. In humans, the sperm cell is the only example.

• Wrap the lecture by returning to the frame: point at the five headings and ask them to name one organelle under each without notes.

4. Close

4 minutes.

• Ask the question that makes this an anatomy course rather than a vocabulary list: given a cell you have never seen, packed with smooth ER and mitochondria, what would you guess it does for a living? Take two or three answers and press for reasoning.

• Assign the reading: pages 11 to 13. Tell them the reading covers what we just walked through, so it should confirm rather than introduce. If any of it feels new, that is the section to bring a question about.

• Preview the connection: tissues are next, and a tissue is defined by the cells that build it. What an organelle does at this scale determines what a tissue can do at the next one.

• Dismiss by procedure.

Objectives

• Students will correct their feedback loop diagrams, identifying the control center and distinguishing effector from response.

• Students will name the major organelles and group them by function.

• Students will distinguish rough from smooth ER by structure and by the jobs each performs.

• Students will explain how organelle abundance reflects a cell’s function, using secretory cells, liver cells, and cardiac muscle as examples.

• Students will describe the roles of centrioles and cilia and explain the clinical consequence of ciliary loss in respiratory epithelium.