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LSU / Biological Sciences / BIOL 2160 / Which ions are the highest concentration in the ecf?

Which ions are the highest concentration in the ecf?

Which ions are the highest concentration in the ecf?

Description

School: Louisiana State University
Department: Biological Sciences
Course: Human Physiology
Professor: K. thompson
Term: Fall 2019
Tags: HP, Physiology, Urinary, Gastrointestinal, immune, and immune system
Cost: 50
Name: BIOL 2160/HUMAN PHYSIOLOGY FINAL EXAM STUDY GUIDE
Description: Includes all notes/key concepts. Includes Kahoot & quiz questions.
Uploaded: 12/08/2019
52 Pages 157 Views 2 Unlocks
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PHYSIOLOGY ​FALL 2019 FINAL EXAM COMPREHENSIVE STUDY GUIDE 


Which ions are the highest concentration in the ecf?



CHAPTER 18-19: 

THE URINARY SYSTEM 

Lecture given on November 21st.

Kidneys

● Main kidney functions

○ Primarily responsible for maintaining stability of ECF volume, electrolyte composition, and osmolarity

■ Kidneys are the main organs of the urinary system.

■ ECF → extracellular fluid. Fluid outside the cell.

○ Main route for eliminating potentially toxic metabolic wastes and foreign compounds from the body If you want to learn more check out What is the pathway of urine from the collecting ducts to the exterior of the body?

● Overview of some kidney functions

○ Maintain H2O balance (water levels) in the body


Which structure would urine flow out of the kidney?



■ The most important thing they do. If your kidneys aren’t functioning

correctly, you’ll have problems with dehydration.

■ When we lose water/become dehydrated, one of the main places we lose it from is the blood… the plasma.

○ Maintain proper osmolarity of body fluids (including blood), primarily through regulating H2O balance We also discuss several other topics like What was the ten percent plan also known as?
If you want to learn more check out What types of research would you use if you were interested in studying visibility of tattoos on perceptions of competence for work?

■ If you get dehydrated, blood becomes too thick and clots easily.

○ Regulate the quantity and concentration of most ECF ions

○ Maintain proper plasma volume

○ Help maintain proper acid-base balance in the body

○ Excreting (eliminating) the end products (wastes) of bodily metabolism


What leaves the kidney and goes to the urinary bladder?



Keep in mind:

When we start talking about the kidneys, it’s human nature to become fixated on the fact that they produce urine. But, that is not the important part.

Understand that: urine leaves the body. What matters is what stays in the body.

If you’re looking for a function of the kidneys, rather than saying they produce urine, focus on their main goal.

Their main goal → to make perfect blood. Your kidneys filter your blood. Urine is just a byproduct.

Urinary System

● Consists of

○ Urine forming organs

■ Kidneys

○ Structures that carry urine from the kidneys to the outside for elimination from the body If you want to learn more check out Which molecules have london dispersion forces?

■ Ureters

■ Urinary bladder

■ Urethra

○ Ureters

■ Smooth muscle-walled duct

■ Exit each kidney and carry urine to the urinary bladder

■ Hollow tubes that lead the kidney and flow into urinary bladder.

○ Urinary Bladder

■ Temporarily stores urine

■ Hollow, distensible, smooth muscle-walled sac

■ Periodically empties to the outside of the body through the urethra ■ Strictly for storage. Nothing happens to the urine once it gets to the bladder. Once it leaves the kidneys, we’re done messing with it. All the

changes to urine take place in the kidney.

Bladder just keeps you from going to the bathroom every 5 seconds.

Urethra

● Conveys urine to the outside of the boyd

● Urethra is straight and short in females

● In males

○ Much longer and follows curving course from bladder to outside

○ Dual function

■ Provides route for eliminating urine from bladder If you want to learn more check out How do we increase food production with limited resources?

■ Passageway for semen from reproductive organs

Urinary System

Nephron

Wehaveayellowpartanda

purplepartsurrounding it.

The purple part is your blood

supply→Thebloodentering

thekidneystogetfiltered.

It is called the vascular (blood)

component.

In yellow, isthetubular

component.

It carries thefiltrate.

What we will talk aboutforthe

restofthechapter istheback If you want to learn more check out What type of business buys in bulk from a manufacturer and sells smaller quantities to a retailer?

andforththatoccurs inthe

bloodandurine.

We have things leavingblood,

going intotheurineandthings

leaving urine, going into the

blood.

Nephron

● Vascular component

○ Dominant part is the glomerulus

■ Ball of capillaries

■ Water and solutes are filtered through glomerulus as blood passes

through it

● Blood enters nephron through glomerulus and most the water gets

filtered out. That becomes the filtrate → becomes the urine.

The pathway it takes: 

Filtrate gets collected in Bowman’s capsule (surrounding glomerulus) → It enters the Proximal tubule →

Loop of Henle →

Distal tubule →

Collecting duct (where it leaves the kidney.)

● Tubular component

○ Hollow, fluid-filled tube formed by a single layer of epithelial cells

■ Pay attention to this sentence. A single layer means → it is leaking.

Anything we want to be waterproof will have more than 1 cell.

A single layer (like capillaries) is where exchange occurs.

This tubule (yellow part) is one cell layer thick, because we want things to be able to pass through.

○ Components

■ Bowman’s capsule

■ Proximal tubule

■ Loop of Henle

● Descending limb

● Ascending limb

■ Distal tubule

■ Collecting duct or tubule

Basic Renal Processes

● Glomerular filtration

○ Happens in glomerulus. Water and solutes get filtered out.

● Tubular reabsorption

○ Reabsorption: that is something going from the urine → blood.

If you reabsorb something, you want to keep it.

● Tubular secretion

○ Opposite of reabsorption. Something going from blood → urine.

It is something we want to get rid of, something we don’t need anymore.

● Concentration

Urine results from these 4 processes.

Important: written in red. 

Of the total plasma that enters the glomerulus, 80% leaves

unfiltered.

Only 20% of the plasma gets filtered.

You may say, why do we only need to

clean 20% of our blood?

We don’t. We need to clean it all.

We just can’t do it all at once.

If 20% gets filtered at a time, the rest of it goes to your organs, and eventually it all gets filtered.

Glomerular Filtration

● Fluid filtered from the glomerulus into Bowman’s capsule passes through three layers of the glomerular membrane

● During this step, almost everything that CAN be removed from the blood is removed. Filtrate, which will become urine, is formed in this process.

During filtration (the 1st step), just about everything we can reabsorb, we do. We remove as much water and solutes as possible.

This is collected in the tubule outside the glomerulus called Bowman’s capsule.

Tubular Re-absorption

● Involves the transfer of substances from tubular lumen into peritubular capillaries ● Highly selective and variable process

● Involves trans-epithelial transport

○ Reabsorbed substance must cross five barriers

■ Must leave tubular fluid by crossing luminal membrane of tubular cell ■ Must pass through cytosol from one side of tubular cell to the other

■ Must cross basolateral membrane of the tubular cell to enter interstitial fluid

■ Must diffuse through interstitial fluid

■ Must penetrate capillary wall to enter blood plasma

When we reabsorb something, it goes from the urine → blood.

It has to cross five different layers/barriers. They can be seen in the picture below.

Steps in Trans-Epithelial Transport

The yellow part on the left that looks like a horseshoe is Bowman’s capsule. The red teardrop → glomerulus.

- We filter out water & solutes, it’s collected in Bowman’s capsule → moves to the Proximal tubule. (Which is zoomed in on the right.)

The lumen → the interior part of something. The inside of the tubule.

This tubule is made up of epithelial cells, just a single layer.

Any time something leaves tubule → into capillaries or leaves urine → blood, it has to first cross the luminal membrane, the cytoplasm of the cell, then the outer membrane called the basolateral membrane (facing interstitial) → interstitial fluid → capillary wall. Anytime something gets reabsorbed, it has to cross those five barriers before it goes from urine → blood.

What do you think happens when something gets secreted?

The exact same process, but in reverse order.

Goes through all 5 barriers and goes from blood → urine.

Tubular Reabsorption

● Passive reabsorption

○ No energy is required for the substance’s net movement

○ Occurs down electrochemical or osmotic gradients

● Active reabsorption

○ Occurs if any one of the steps in transepithelial transport of a substance requires energy

○ Movement occurs against electrochemical gradient

Two types of reabsorption: passive and active.

Passive: no energy needed. Active: energy needed.

- If at least one barrier requires energy, then that whole thing is active reabsorption.

Na+ Reabsorption

● A Na+ -K+ ATPase pump in basolateral membrane is essential for Na+ reabsorption ● Of total energy spent by kidneys, 80% is used for Na+ transport

● Na+ is not reabsorbed in the descending limb of the loop of Henle

● Water follows reabsorbed sodium by osmosis which affects blood volume and blood pressure

One of the most important things that gets reabsorbed is sodium.

Remember, if we are reabsorbing Na+, it is staying in the blood.

If it’s in the blood, it’ll eventually make its way to the outside of the cells.

Remember there’s always more Na+ outside the cell than in… this is why: - We keep reabsorbing it to maintain that gradient. If we stop reabsorbing it, eventually it would equal out.

Na+ is mostly absorbed (about ⅔) in the proximal tubule, right outside Bowman’s capsule. Approximately ¼ is reabsorbed in the Ascending limb of the loop of Henle. Distal and collecting tubules / 8% → you only reabsorb Na+ when you need to, when you’re dehydrated. That is the only time you reabsorb Na+ in the Distal tubule.

Sodium Reabsorption

Size of the icon will give you an

indication of the ion gradient.

There’s more Na+ outside the cell

than in.

So moving across the Luminal

membrane, passive.

But there’s more Na+ outside the

cell than in.

So moving from low → high, across

the Basolateral membrane is

active.

The Na+/K ATPase uses a lot of

energy to transport Na+.

Everything else is passive, but if at least 1 step requires energy, then the sodium reabsorption is active. If even 1 step requires energy, then the whole thing’s active.

Reabsorption

● Glucose and amino acids are reabsorbed by sodium-dependent, secondary active transport.

● The reabsorption of water into the blood surrounding the proximal tubule increases the concentration of urea inside the tubule, as water is lost from the tubule. This produces a concentration gradient for urea from the tubule into the interstitial fluid.

- Sodium being reabsorbed provides the energy to reabsorb glucose and amino acids → two things that we need.

- So, we reabsorb sodium because we need it.

But also, it allows us to also reabsorb glucose and amino acids.

Passive Reabsorption of Urea at the End of the Proximal Tubule

Urea is toxic and poisonous. We don’t want it.

So why would be reabsorb it into our blood?

- Well, we don’t want to reabsorb it.

But it’s a means to an end. →

Filtrate coming out of Bowman’s capsule, we have to

have Na+.

That will put a lot of Na+ in the blood, and water will

follow since it’s an area of higher-solute

concentration.

So then, we also reabsorb a lot of water.

When that happens at the end of the Proximal tubule,

since we reabsorbed all that water, that makes a very

steep concentration gradient for urea.

So we also reabsorb some of it.

We don’t want to reabsorb urea, we want to know

how to stop it.

But we have to have Na+, we have to have water,

glucose, and amino acids → if that means we have

to reabsorb some urea in the process, so be it.

Small amounts of urea does not hurt us.

Tubular Secretion

● Transfer of substances from peritubular capillaries into the tubular lumen ● Involves trans-epithelial transport (steps are reversed)

● Kidney tubules can selectively add some substances to the filtrate

● Most important substances secreted into the tubules:

○ H+ 

- Important in regulating acid-base balance

- Secreted in proximal, distal, and collecting tubules

○ K+ 

- Keeps plasma K+ concentration at appropriate level to maintain normal membrane excitability in muscles and nerves

- Secreted only in the distal and collecting tubules

○ Organic ions 

- Secreted only in the proximal tubule

Passes through the same 5 barriers, but in the opposite direction.

This is getting rid of anything we don’t want — could be toxic or just a surplus of something.

What types of things get secreted?

1. Protons

- Get secreted from our blood into our urine.

If you add protons to a solution, you’re making it more acidic, lowering the pH. Urine is sterile because the pH is so low, bacteria can’t grow.

- If our blood gets too acidic, we secrete protons in our urine.

If it gets too basic, we stop secreting protons.

(Remember: we don’t care about pH in urine, we just care about the pH in the blood.

So we can speed it up or slow it down to make sure the pH in the blood is between 7-8.)

Test question. 

Protons lower pH. Protons make it acidic.

2. Potassium/K+

- There’s always more K+ inside the cell than out.

But if we kept reabsorbing K+, there wouldn’t be.

We want to keep K+ concentrations outside the cell pretty low.

So, we secrete K+ into the urine.

3. Organic ions

- Can be byproducts from metabolism, toxins, or drugs.

Some drugs are detected in urine is because of secretion.

Review of Nephron activity

First three processes we’ve already talked about.

● Filtration → blood enters through glomerulus. Water & solutes get filtered out. Collected in Bowman’s capsule.

● Reabsorption → taking everything from the urine, putting it back in the blood that we wanna keep. Lots of Na+, water, glucose, amino acids, and some urea.

● Secretion → putting things into the urine that we don’t want anymore. Lots of protons, K+, and inorganic ions.

1. Filtration: Water and small dissolved substances removed from glomerular capillaries. Filtrate collected in Bowman’s capsule.

2. Tubular reabsorption: In the proximal tubule, sodium, water, and nutrients are transported from the filtrate to the blood.

3. Secretion: Occurs in the proximal and distal tubule and actively moves H+, K+, some drugs, and organic ions from the blood back into the filtrate.

4. Concentration: Maintenance of a large osmotic gradient around the Loop of Henle allows for water to be retained and urine to become highly concentrated.

● Last step, Concentration → ability to concentrate our urine when we become dehydrated.

Drawn on board in class.

Explanation on next page.

Descending limb (descend → go down) and the Ascending limb (go up).

Descending limb 

● Permeable to water, but not Na+.

○ Water flows down. So on the way down, we reabsorb lots of water.

● If we keep taking water out filtrate, by the time you get to the bottom, it’s very concentrated. (If you remove water from something, it makes it more concentrated.)

Ascending limb 

● Permeable to Na+, but not water.

○ On the way up, we don’t reabsorb water. We reabsorb Na+.

But why do we do this? 

If you don’t drink enough water or sweat too much, you become dehydrated. One of the things that happens is a hormone gets released by brain called ADH. - Antidiuretic hormone → keeps you from peeing.

Another name for it is Vasopressin.

The whole purpose of it is to make sure you don’t urinate too much and if you do, to make sure what’s coming out is very concentrated.

(Because you don’t wanna lose water when already dehydrated.)

- ADH causes these protein channels, aquaporins (water channels), to be inserted into the Distal tubule membrane.

Now, on the way up (since we lost all this solute,) the urine is very dilute.

- When we are dehydrated, we don’t want to lose water. We want concentrated urine. So, since we have this huge ion gradient outside the Distal tubule, once we put these aquaporins in the membrane, water will naturally (through osmosis) get reabsorbed. That is water not leaving kidneys. That’s water staying inside the body.

So whenever urine comes out kidneys, it’s very concentrated (dark yellow). Hardly any water in it. This is why → vasopressin.

- If you couldn’t concentrate your urine and are constantly losing water → when you become dehydrated, every time you urinate, you’d just lose more water.

The following slides are the above explanation, but just written out from the Powerpoint.

Loop of Henle

● Descending limb highly permeable to water, but not to NaCl.

As filtrate flows down, water leaves the tubule as the osmolarity of the extracellular fluid increases.

Loss of water increases the osmolarity of the filtrate.

At the bottom of the loop, the concentration of the filtrate and the extracellular fluid is equal (1200 mOsm).

● Ascending limb is impermeable to water, but permeable to NaCl.

As highly concentrated filtrate flows up, NaCl diffuses, then is actively transported out of the tubule.

But water does not follow. Filtrate becomes more dilute than extracellular fluid

Role of Vasopressin

● Vasopressin-controlled, variable water reabsorption occurs in the distal tubule and the collecting duct.

● 65 percent of water reabsorption is obligatory in the proximal tubule. In the distal tubule and collecting duct it is variable, based on the secretion of ADH (antidiuretic hormone / vasopressin).

● The secretion of vasopressin increases the permeability of the tubule cells in the distal tubule and collecting duct to water by inserting aquaporins. An osmotic gradient exists outside the tubules for the transport of water by osmosis.

● Vasopressin is produced in the hypothalamus and stored in the posterior pituitary. The release of this substance signals the distal tubule for the reabsorption of water. ● During a water deficit, the secretion of vasopressin increases. This increases water reabsorption. Alcohol is a vasopressin inhibitor (frequent urination)

● During an excess of water, the secretion of vasopressin decreases. Less water is reabsorbed. More is eliminated.

Water Retention

● Kangaroo rats are so efficient at reabsorbing water (they have such a long Loop of Henle) that they can recover nearly all of the water filtered out by the kidneys. ● They never have to drink water at all; the water contained in their food is enough for survival.

Alcohol and ADH

● Alcohol is an ADH inhibitor. ADH tells the body to conserve water. So, when alcohol inhibits ADH, it stimulates your body to get rid of water, in the form of urine. ● For every 250 MLs of alcohol consumed, your body eliminates about 1,000 mLs of water in your urine.

● This quickly dehydrates you, which is what causes the hangover the next day. ○ You pee a lot when drinking. When your urine is clear after immediately drinking, the alcohol inhibits vasopressin so pure water just leaves your bladder.

○ That’s why you’re so dehydrated when drinking. The next day, your urine is dark yellow.

Micturition

● Urine stored in body is eliminated by micturition

● Urine in bladder stimulates stretch receptors

● Contraction of bladder pushes urine out of the body

● Micturition reflex

○ Relaxation of external urethral sphincter muscle allowing urine to pass through the urethra and out of the body

● Under voluntary control but cannot be delayed indefinitely

○ It’s limited. You can only contract is so much. When that bladder overfills, you won’t be able to hold any longer.

● Urinary incontinence

○ Inability to prevent discharge of urine

CHAPTER 20: 

THE GASTROINTESTINAL SYSTEM 

Lectured on December 3rd.

Digestive System

● Primary function

○ Transfer nutrients, water, and electrolytes from ingested food into body’s internal environment

■ The function of the human digestive system → mechanically & chemically break down food into nutrients that can be absorbed into bloodstream

and transported to your cells.

■ In order to accomplish this, the human digestive system performs 4

functions.

● The Digestive System Performs Four functions

○ Motility

○ Secretion

○ Digestion

○ Absorption

Digestive System → Motility

Motility → movement

The digestive system is made of several different layers. Muscular layer is able to contract & initiates 2 different types of movements: propulsive and mixing. 

● Motility 

○ Muscular contractions that mix and move forward the contents of the digestive tract

○ Two types of digestive motility

■ Propulsive movements

● Push contents forward through the digestive tract

■ Mixing movements -- the back and forth.

● Serve two functions

○ Mixing food with digestive juices promotes digestion of

foods

○ Facilitates absorption by exposing all parts of intestinal

contents to absorbing surfaces of digestive tract

■ Exposes more surface area & facilitates absorption.

Digestive System → Secretions

● Secretions What gets secreted?

○ Consist of water, electrolytes, and specific organic constituents (enzymes) ○ Secretions are released into digestive tract lumen and are normally reabsorbed in one form or another back into blood after their participation in digestion

■ Recycled

Digestive System → Digestion

● Digestion breaking large molecules into small molecules to be absorbed ○ Biochemical breakdown of structurally complex foods into smaller, absorbable units

○ Accomplished by enzymatic hydrolysis

○ Complex molecules and their absorbable, broken-down units

■ Carbohydrates → monosaccharides

■ Proteins → amino acids

■ Fats → glycerol and fatty acids

- The whole goal of digestion → breaking food down into a small

enough unit to be able to absorb into the blood.

- Large molecules that we eat get broken down into simple sugars,

proteins, and fats.

Digestive System → Absorption

● Absorption the most important step.

● In the small intestine, most absorption is complete

○ Small units resulting from digestion, along with water, vitamins, and electrolytes are transferred from digestive tract lumen into blood

- If you can’t absorb nutrients, you will starve to death.

Digestive System

● Digestive tract

○ Continuous from mouth to anus

○ Consists of

■ Mouth

■ Pharynx

■ Esophagus

■ Stomach

■ Small intestine

■ Large intestine

● Cecum

● Appendix

● Colon

● Rectum

■ Anus

These are organs that make up the digestive tract from beginning to end. Food enters them.

● Accessory digestive organs

○ Salivary glands

○ Exocrine pancreas

○ Bilary system

■ Liver

■ Gallbladder

Food does not actually enter these organs, but they do play a big role in

digestion.

Digestive Tract

● Wall has same general structure throughout length from esophagus to anus ● Four major tissue layers that make up the digestive tract of a human being. ○ Mucosa

■ Innermost layer, Lumina

○ Submucosa

○ Muscularis externa (layer of muscle)

○ Serosa

■ Outer layer

What does each layer accomplish? What are their goals?

Mucosa, Submucosa, Muscularis externa, Serosa 

● Mucosa

○ Lines luminal surface of digestive tract

○ Highly folded surface greatly increases absorptive area

- Mucosa is folded up. Increased surface area increases absorption.

Think of a mop, there are multiple pieces of cloth.

One piece of cloth vs multiple pieces = more absorbent.

● Submucosa

○ Thick layer of connective tissue

○ Provides digestive tract with elasticity

- Layer just outside. Its main job is elasticity.

It allows your digestive tract to stretch without easily tearing.

Why would we want that?

Having a digestive tract that can expand and stretch without tearing is a

huge advantage in terms of eating.

If it was smaller, there is a higher risk of starvation.

● Muscularis externa

○ Major smooth muscle coat of digestive tube

○ In most areas consists of two layers

■ Circular layer (on inside)

● Inner layer

● Contraction decreases diameter of lumen

■ Longitudinal layer

● Outer layer

● Contraction shortens the tube

- When they contract, overall, length of digestive tract

shortens. Mainly happens in intestines.

Why do we care about these contractions so much?

Without them, food would never get from your mouth to

your stomach.

Contractile activity produces propulsive and mixing movements

● Serosa (outermost layer)

○ Secretes serous (thick) fluid

■ Lubricates and prevents friction between digestive organs and

surrounding viscera

■ Supports digestive organs in proper place while allowing them freedom for mixing and propulsive movements

- With all these different contracting parts touching each other,

there is a risk of friction damaging these organs.

The serous fluid lubricates, keeps tissues from rubbing into each

other & damaging digestive tract.

- Also, these organs are not attached to bone. This fluid gives them

something to float in.

Mouth

Lips 

● Form opening

● Help procure, guide, and contain food in the mouth

● Well-developed tactile sensation

- Lips procure food, keeping it from falling out.

Palate 

● Forms the roof of the oral cavity (separates mouth from nasal passages) - Palate keeps food from going into your nasal passages.

Tongue 

● Forms floor of the oral cavity (separates mouth from nasal passages) ● Composed of skeletal muscle

● Movements aid in chewing and swallowing

● Taste buds

○ Allows you to taste your food, enhancing enjoyment.

○ But it also plays a much more important role → keeps you from swallowing something harmful.

How?

Well, the human tongue can detect a few different tastes: sweet, sour, salty, bitter, and umami.

The one taste that just about everyone dislikes is bitter.

Most poisons in nature have a very bitter taste. We don’t enjoy that taste, so we avoid.

- Tongue, one of the strongest muscles in the body, moves food around & facilitates chewing.

Pharynx Anything that goes in your mouth ends up in the pharynx eventually. ● Cavity at rear of throat

● Common passageway for digestive and respiratory systems

● Tonsils

○ Within side walls of pharynx

○ Lymphoid tissue

Teeth 

● Responsible for chewing (mastication → mechanical breakdown of food) ● First step in digestive process

● Functions of chewing

○ Grind and break food into smaller pieces to make swallowing easier and increase food surface area on which salivary enzymes can act

○ Mix food with saliva

○ Stimulate taste buds

Chewing does a couple different things → breaks food up mechanically, and facilitates the breaking down chemically. Breaking food into smaller pieces makes it easier to swallow. - But by breaking it into smaller pieces, it also helps expose it to digestive enzymes in the mouth, as well as the rest of the digestive tract.

It allows your food to mix better with saliva.

Without saliva, you wouldn’t really be able to taste anything.

So what even is saliva?

Saliva 

● Produced largely by three major pairs of salivary glands

● Composition

○ 99.5% H2O

○ 0.5% electrolytes and protein

● Functions

○ Salivary amylase begins digestion of carbohydrates

■ Salivary amylase → an enzyme that breaks down sugar.

○ Facilitates swallowing by moistening food

○ Antibacterial action

■ Lysozyme destroys bacteria

● Lysozyme → an enzyme that destroys bacteria.

■ Saliva rinses away material that could serve as a food source for bacteria ● When your mouth gets very dry & you get bad breath, it’s because

you don’t have a lot of saliva, bacteria thrives & releases sulfur

gas.

○ Solvent for molecules that stimulate taste buds

○ Helps keep mouth and teeth clean

○ Rich in bicarbonate buffers

■ A buffer helps control pH. If something acidic in your mouth, often the saliva will neutralize it. Buffers help mediate + control pH.

Pharynx and Esophagus

● Swallowing

○ Motility associated with pharynx and esophagus

○ Initiated when food or drug is voluntarily forced by tongue to rear of mouth into the pharynx

○ Most complex reflex in body

○ Can be initiated voluntarily but cannot be stopped once it has begun

○ Process divided into two stages

■ Oropharyngeal stage

● Happens in the back of the mouth.

■ Esophageal stage (moves substance from the mouth, through the

pharynx, and into esophagus)

● Happens past the pharynx, in the esophagus.

- Swallowing is one of the most complex reflexes in body. Once you start it, you can’t stop. - Gravity has very little to do with swallowing food. When you picture the esophagus (tube coming from pharynx and going into stomach), it is really a narrow tube.

The food is not going anywhere without muscle contractions forcing it into the stomach.

● Esophagus

○ Fairly straight muscular tube

○ Extends between pharynx and stomach

○ Sphincters at each end (Sphincter → circular muscle)

■ Pharyngoesophageal sphincter

● Keeps entrance closed to prevent large volumes of air from

entering the esophagus and stomach during breathing

○ Contracts and keeps air from entering the stomach.

■ Gastroesophageal sphincter

● Prevents reflux of gastric contents

○ Very important.

It’s a circular muscle right where the esophagus goes into

the stomach. It contracts to keep things that are entering

the stomach in the stomach, because everything there is

covered in hydrochloric acid which burns.

If you eat too fast or too much, a lot of the time the

sphincter can’t contract strong enough to keep the

contents inside. Acid reflux.

■ (Tums helps just because it has a high pH! It

neutralizes.)

○ Peristaltic waves push food through esophagus

Peristalsis in the Esophagus

Once you swallow your food and it’s inside the

esophagus, it’s called a bolus.

The diameter of the bolus is wider than the diameter

of the esophagus.

Again, it won’t just fall down into the stomach -- you

have to have rhythmic contraction called peristalsis.

Stomach

● J-shaped sac-like chamber lying between esophagus and small intestine ● Divided into three sections

○ Fundus

○ Body

○ Antrum

- We mainly care about the function of the stomach.

Storage is a big purpose. Why would we want to store food in the stomach? - To give it a longer time to digest and to allow digestion/absorption to occur past the stomach, in the intestine.

If we can hold food longer in stomach, it allows enough time in the small intestine to completely digest & absorb food.

- Digestion takes a long time. Stomach stores food to allow it!

● Three main functions

○ Store ingested food until it can be emptied into small intestine

○ Secretes hydrochloric acid (HCl) and enzymes that begin protein digestion ■ Break down protein. When you think stomach, think protein.

That’s where most protein gets digested.

○ Mixing movements convert pulverized food to chyme

■ Back and forth movements in stomach to allow food to mix together with HCl. Once food is mixed with HCl, it’s called chyme.

● Pyloric sphincter (one of the most important muscles in the body)

○ Serves as a barrier between the stomach and the upper part of small intestine - This sphincter muscle acts like a release valve.

When it relaxes, it allows food to leave the stomach and go into small

intestines.

When it contracts, it keeps it in the stomach.

This muscle is extremely important, it is like the gatekeeper for the small intestine.

Here is what it looks like! 

Again, it’s like a valve.

- When it’s contracted, everything

stays in the stomach.

- When relaxed, chyme can leave the

stomach and go into the first part of

the small intestine.

What do these stomach movements accomplish?

Gastric Motility

● Four aspects

○ Filling

■ Involves receptive relaxation

● Enhances stomach’s ability to accommodate the extra volume of

food with little rise in stomach pressure

● Triggered by act of eating

● Mediated by vagus nerve

- When you swallow food/are about to, your stomach starts

to relax so it can receive that food.

○ Storage

■ Takes place in body of stomach

- Keeping that chyme in there long enough until the small intestine

is ready for it.

○ Mixing

■ Takes place in antrum of stomach

- Back and forth mixing of chyme with HCl, digestive enzymes.

○ Emptying

■ Largely controlled by factors in duodenum

- Whenever the stomach empties into the duodenum/small

intestine, what is going on in there controls whether food or

chyme can leave the stomach.

The conditions in the duodenum control gastric emptying.

Gastric Emptying

● Factors in stomach (only thing in stomach that plays a role)

○ Amount of chyme in stomach is the main factor that influences strength of contraction — Amount of chyme promotes gastric emptying.

■ If you got a lot of chyme in the stomach (a full stomach), the stomach will want to empty.

- That is the only factor that promotes gastric emptying.

Everything else on the list prevents it.

● Factors in duodenum → all of these prevent stomach from emptying. ○ Fat 

■ Fat digestion and absorption takes place only within lumen of small

intestine

● Fat = energy. Fat is important.

■ When fat is already in duodenum, further gastric emptying of additional fatty stomach contents is prevented

● When fat is in duodenum, it needs a chance to break it down

before emptying.

○ pH 

■ Un-neutralized acid in duodenum inhibits further emptying of acidic

gastric contents until neutralization can be accomplished

● If there is un-neutralized acid in the duodenum (coming out of

stomach)... it has a very low pH.

The only organ in the body that can handle that low pH is the lining

of the stomach. Everything else will get burned through.

So if we have un-neutralized acid in the duodenum, it gets

pancreas involved to neutralize so that the small intestine is not

damaged.

○ Hypertonicity (a lot of solute)

■ Gastric emptying is inhibited when osmolarity of duodenal contents starts to rise

● A lot of solute (food particles, chyme) in the duodenum.

The duodenum needs time to absorb nutrients & signals the

stomach to not empty. 

○ Distension (stretching)

■ Too much chyme in duodenum inhibits emptying of even more gastric contents

● If there is a lot of chyme in the stomach & it stretches, the

duodenum cannot take more.

● Additional factors that influence gastric motility

○ Emotions

■ Sadness and fear - tend to decrease motility

- If you’re sad or afraid, your stomach doesn’t contract as much.

■ Anger and aggression - tend to increase motility

- If you’re angry, it contracts a lot.

○ Intense pain, tends to inhibit motility

- Your body is more concerned about finding the source of pain,

rather than digesting food.

Gastric Secretions

● Alkaline mucus: protects stomach lining from other secretions

○ Alkaline = high pH, basic.

○ It helps neutralize acid & keeps it from damaging the lining of the stomach as quickly as it would without it.

● Pepsinogen: begins protein digestion when activated

○ Pep = peptide, proteins. This is an enzyme that helps break down proteins. ○ Pepsinogen is activated by HCl.

● HCl: activates pepsinogen, breaks down connective tissue, kills microorganisms ○ HCl helps break down pretty much everything it comes in contact with.

● Intrinsic factor: facilitates re-absorption of Vitamin B12

● These secretions are released from secretory cells that are under the control of endocrine/paracrine cells elsewhere in the stomach and intestine.

○ All these are released by cells in the stomach.

Gastric Hormones

Three big ones.

These are all hormones released by stomach based on what’s going on in duodenum. ● Secretin: stimulated by acidic chyme in the duodenum. Release stimulates the pancreas to release bicarbonate buffer.

○ Secretin gets released & tells pancreas to release bicarbonate buffer → which neutralizes acid.

● Gastrin: stimulated by the presence of protein in the duodenum. Release stimulates chief and parietal cells to secrete more HCl.

○ If there’s protein in duodenum, it means it hasn’t been digested properly in stomach. Gastrin gets released & signals to the stomach to release more HCl to activate more pepsinogens, to break down more proteins.

● Cholecystokinin (CCK): stimulated by presence of fat and protein in the duodenum. Release stimulates pancreas to release lipase, as well as proteolytic enzymes. ○ If there’s proteins or fat in duodenum → cholecystokinin (CCK) gets released and tells the pancreas to release the enzyme lipase to break down fats and proteases to break down proteins.

Phases of Gastric Secretion

● Cephalic phase (refers to head)

○ Refers to increased secretion of HCl and pepsinogen that occurs in response to stimuli acting in the head before food reaches the stomach

■ You start to digest your food before you even eat it.

When you see, smell, or think about food → your stomach will growl.

That is basically your stomach releases more HCl in preparation for the

food that is on its way.

● Gastric phase (this is what happens while the food is in the stomach) ○ Begins when food actually reaches the stomach

○ Presence of protein increases gastric secretions

● Intestinal phase (when something is in duodenum, it says to shut it down) ○ Inhibitory phase

○ Helps shut off flow of gastric juices as chyme begins to empty into small intestine

■ Fat, proteins, too acidic chyme say to shut it down.

Pancreas

One of the worst types of cancer you can get is pancreatic. High mortality rate. ● Mixture of exocrine and endocrine tissue

● Elongated gland located behind and below the stomach

● Endocrine function

○ Islets of Langerhans

■ Found throughout pancreas

■ Secrete insulin and glucagon

● Exocrine function

○ Secretes pancreatic juice consisting of:

■ Pancreatic enzymes

■ Aqueous alkaline solution actively secreted by duct cells that line

pancreatic ducts

- Without the pancreas, you cannot digest your food properly.

The pancreas releases enzymes that breaks down proteins, sugars, and fats. It also releases the buffer to neutralize chyme.

So if your pancreas fails completely, your chances of survival drop to 0% — it is an organ you cannot live without.

Pancreatic Enzymes

● Proteolytic enzymes

○ Digest protein

■ Trypsin

■ Chymotrypsin

■ Carboxypeptidase

● These are proteolytic enzymes, which break down proteins

● Pancreatic amylase (breaks down sugars)

○ Converts polysaccharides into disaccharides

● Disaccharides → 2 simple sugars

● Pancreatic lipase

○ Only enzyme secreted throughout entire digestive system that can digest fat ● In the entire human body, this is the only enzyme that can break

down fat.

If the pancreas isn’t working, you can’t eat proteins, sugars, or fats.

What is left to eat? Not much.

Liver

Another organ you cannot live without.

Liver secretes bile + bile salts, which is secreted in gallbladder.

● Bile

○ Actively secreted by liver and actively diverted to gallbladder between meals ○ Stored and concentrated in gallbladder

○ After meal, bile enters duodenum

- Bile is a derivative of cholesterol. Cholesterol → fat.

Bile breaks down fat because like dissolves like.

Question asked on final: 

A person that has their gallbladder removed will need to closely

monitor their intake of what?

Fats.

● Bile salts

○ Derivatives of cholesterol

○ Convert large fat globules into a liquid emulsion

○ After participation in fat digestion and absorption, most are reabsorbed into the blood

Small Intestine

● Site where most digestion and absorption take place

● Motility includes

○ Segmentation

○ Migrating motility complex

■ Two different types of contractions that occur

Just about everything gets digested and absorbed in the small intestine. Most important organ in the digestive tract.

Small Intestine → Segmentation 

● Primary method of motility in small intestine

● Consists of ring-like contractions along length of small intestine

● Within seconds, contracted segments relax and previously relaxed areas contract ● Action mixes chyme with digestive juices throughout small intestine lumen and exposes chyme to all absorptive surfaces of small intestine mucosa

● Also sweeps intestines clean between meals

All segmentation means → the small intestine is not 1 long muscle.

It is thousands of tiny muscles that can contract at different times.

Segments can contract independently of each other.

They can contract, move food & chyme back and forth to be digested + absorbed.

Digestive enzymes → yellow.

Chyme → maroon

Small Intestine → Absorption 

● Absorbs almost everything presented to it

● Most occurs in duodenum and jejunum

● Adaptations that increase small intestine’s surface area

○ Inner surface has permanent circular folds

○ Microscopic finger-like projections called villi

● Lining is replaced about every three days

- Small intestine absorbs just about everything that goes into it.

Again, this is the most important step in digestion, because if you don’t absorb, it’s like you didn’t eat at all.

- The inside has finger-like projections that face the lumen, kind of like a billion little mops that increase surface area & absorption.

It also sweeps intestines clean between meals.

These microvilli are like tiny hairs that absorb all these nutrients into the bloodstream.

Large Intestine (also referred to as colon)

● Primarily a drying and storage organ

○ When you think of large intestine, think drying. This is a drying organ. It removes water.

● Consists of

○ Colon

○ Cecum

○ Appendix

○ Rectum

● Contents received from small intestine consists of indigestible food residues, unabsorbed biliary components, and remaining fluid

○ You have undigested food, waste, bile, and water entering the large intestine. ■ You want to be able to reabsorb as much water as you can.

A lot of the water, salt, vitamins get reabsorbed in the large intestine.

● Colon

○ Extracts more water and salt from contents

○ Feces → what remains to be eliminated

■ What is left, is a solid waste with most water removed → feces (what leaves the body.)

- If large intestine starts contracting to vigorously, you don’t have

time to reabsorb all the water.

The water leaves with the feces, resulting in diarrhea.

That is one of the quickest ways to get dehydrated.

● Mass movements

○ Massive contractions (large muscle contractions)

■ The whole goal is to push solid waste out of the body.

○ Moves colonic contents into distal part of large intestine

● Defecation reflex

○ Initiated when stretch receptors in rectal wall are stimulated by distension (too much contracting)

○ Causes internal anal sphincter to relax and rectum and sigmoid colon to contract more vigorously

○ If external anal sphincter (skeletal muscle under voluntary control) is also relaxed, defecation occurs

■ Under voluntary control, but not permanently.

Eventually defecation will occur.

CHAPTER 23: 

THE IMMUNE SYSTEM 

Lectured on December 5th.

In innate immunity, recognition and response rely on traits common to groups of pathogens

The immune system can be broken into

2 broad categories:

Innate Immunity: The immune system you were born

with (all animals have it)

Adaptive Immunity: The immune system you acquired

throughout your lifetime from being exposed to

pathogens

(only vertebrates have)

Let’s start with what you were born with → Innate Immunity

We have physical barriers that make sure pathogens don’t make it into our body. As long as they are outside our body, they aren’t doing any harm.

Barrier Defenses

● Skin is a barrier to microbes

○ Continuously shed, removing microbes that gain a foothold on skin

- All the skin you see outside your body are dead cells, not getting blood flow. If they aren’t getting blood, they aren’t getting glucose or oxygen.

- It makes it very difficult for anything living to survive on that.

○ Many skin secretions contain natural antibiotics

■ Give the skin a pH between 3-5 (very acidic)

■ Also has lysozyme (can break down microbes)

● Mucous membrane secretions contain lysozymes

○ Mucous membranes secrete mucus which:

■ traps microbes entering the nose or mouth

■ Dissolves with lysozyme

● Respiratory tract cilia sweep mucus and microbes away from lungs

○ These are barrier defenses with the goal to keep microbes from entering your body.

Internal Defenses: Phagocytes

Phagocytic cells → cells that perform phagocytosis

- Physically eat pathogens/other cells

● Phagocytes: types of leukocytes

● Phagocytosis: ingestion of invading

microorganisms by certain types of white blood

cells

● 4 types of phagocytic WBCs

1. Neutrophills

2. Macrophages

3. Eosinophils

4. Dendritic cells

- All capable of performing process of

phagocytosis which is extremely important

to immune system.

We also have proteins that make it more difficult for microbes to be successful. → Antimicrobial proteins.

Internal Defenses: Antimicrobial Proteins

● These proteins function by attacking microbes directly or by impeding reproduction ○ Interferons: released by virally-infected cells

■ Helps healthy cells resist infection

■ Believed to be caused by fever

■ Activates macrophages

One of the most important is a protein called interferon.

- When a cell becomes infected with a virus, the cell releases interferon. Interferon activates macrophages to come to that area and engulf that cell. (with the idea that if it gets eaten before the virus can replicate,

it prevents neighboring cells from being infected.)

- This is believed to be caused by fever.

This is why taking something to relieve your fever with a slight

fever sometimes makes you stay sick longer.

Internal Defenses: Inflammatory Response

The other thing you’re born with that everyone has experienced is the inflammatory response. Anything in your body that is swollen and red, is inflamed.

Example shown in figure: 

Puncture wound that introduces pathogens into your body.

So they breach that skin barrier.

1. Chemical signals released by macrophages (cytokines) and mast cells (histamines) which cause capillaries to become more permeable

- Macrophages come in the area to clean up bacteria, and when they see the wound, they release a chemical signal called cytokine.

Cytokine → a signal that makes a cell do something.

It releases cytokines that produce other macrophages and mast cells

which release histamine.

Histamine makes your capillaries more permeable/leaky, because

we need to get these WBCs that are in the blood out of the

capillaries and into the area where the wound is.

- Histamine helps increase blood flow, that’s why it’s warm, red,

and swollen.

2. Antimicrobial proteins and clotting elements enter site

- Proteins that are antimicrobial (ex. antibodies) are released as well as clotting elements, to allow the blood to clot without you bleeding to death from a simple wound.

This clot (scab) does 2 things:

1. keeps the blood from flowing out

2. temporarily closes up opening to the inside of the body

- If you have an open wound without a clot, anything can enter the blood & go all over the body.

3. Cytokines attract more phagocytic cells

4. Phagocytic cells engulf microbes and damaged cells

Let’s say something does breach these barriers, it makes its way into your body. - We also have (nonspecific) internal defenses we are born with that will destroy any infected cell.

Internal Defenses: Natural Killer Cells

● Natural Killer cells

○ Attacks body cells that are virally infected or cancerous

○ Releases chemicals that initiate apoptosis (programmed cell death)

■ Any cell infected/damaged are destroyed by NKCs.

It will make these cells undergo apoptosis (cell suicide).

All information above was Innate Immunity.

What about the stuff you acquire throughout a lifetime? Adaptive Immunity. In adaptive immunity, lymphocyte receptors provide pathogen-specific recognition

We have 2 different cell types (lymphocytes) that

control this in different areas.

Key Characteristics of the Acquired Immune Response

1. The immune system must recognize an invader

- Your immune system has to recognize pathogen.

(Time it takes varies, but eventually pathogen is recognized.)

2. The immune system must launch an attack

3. The immune system must remember specific invaders to ward off future infections - Some of the cells from the pathogen stick around, so that the next time you’re exposed to it, it recognizes quicker (maybe before you get symptoms).

This is essentially what happens when you get vaccinated.

Adaptive immunity defends against infection of body fluids and body cells

Adaptive immunity.

You have two different immune systems here.

The Humoral Immunity → will attack things floating around the blood.

(Bacteria, viruses, fungi, protists.)

- Anything floating in the blood is Humoral Immunity.

Cell-Mediated Immunity → once something gets inside of the cell (like a virus infecting a cell), then your Cell-mediated Immune system destroys it.

Your immune system has no interest in saving a cell.

- If a cell gets infected, it’s gone.

All your body cares about is making sure that virus doesn’t replicate.

When a cell gets infected, there are no measures to try to save it. It gets destroyed. That is what cell-mediated response is.

Antigens & Epitopes

● Antigen: any foreign molecule that is specifically recognized by lymphocytes and elicits a response from them

○ Any foriegn molecule your immune system will respond to.

● Epitope: accessible region of an antigen to which an antigen receptor or antibody binds ○ The part of the antigen that actually touches/is recognized by immune cells.

This illustration explains what Dr. C was saying 

about the flu shot. 

In yellow is the pathogen, let’s call that the

flu virus.

They don’t inject that into you.

They don’t even inject the antigen.

They inject the epitope, which is basically

part of the antigen, which is part of the

pathogen that your immune system

recognizes.

- You can get a piece of a piece of a piece and develop the exact same immune response as if you saw the entire virus.

- The epitope is not enough to make you sick.

Antigen Recognition by Lymphocytes

● Vertebrates have two main types of lymphocytes

○ B lymphocytes (B cells)

■ If you want to pretend that “B” stands for blood, that’s a good way to think about it.

■ These cells patrol the blood. They move around looking for pathogens in the blood.

○ T lymphocytes (T cells)

■ T-cells look for infected cells.

● B cells and T cells both have antigen receptors on their plasma membranes

Student question: What’s the difference between an antigen receptor and an antibody? - Structurally, nothing. They’re identical.

If it’s attached to a cell, it’s a receptor.

If it’s just floating around, it’s an antibody.

(But it’s the same exact protein).

Antigen Receptors

Notice: the shapes at the end of these antibodies and receptors, they’ve got to recognize and bind to a specific epitope.

If they don’t recognize it, they don’t fight it.

Recognition → if you don’t recognize it, it will take awhile for you to find something that does, that’s time for you to get sick.

Antibodies

Antibodies (or immunoglobulins)

● Y-shaped molecules made of light peptide chains and heavy peptide chains ● Antigens bind to the variable regions of antibodies in a lock-and-key fashion

Antibodies can be compared to a key.

The light red part (constant region) is like the part of the key

you’re holding when you unlock door.

That part can be any shape.

What makes key unique are the variable regions, that’s like the

teeth to the key.

That’s why that key opens that door.

From 1 antibody to the next, the only thing that really differs are

the variable regions. 

Major Histocompatibility Complex (MHC)

One of the most important concepts in the chapter.

● T cells must bind to an antigen presented by infected cell or antigen-presenting cell ● Infected cells present antigen using MHC

Think of the MHC as a name tag holder.

- Normally, ordinary cells have their own proteins on this MHC and it tells the immune system to go attack.

But whenever a cell gets infected, it puts part of that antigen on its MHC and it’s kinda like waving a flag → come attack, i’ve been infected.

- It’s how your immune cells recognize a cell’s been infected.

They put it on the Class I MHC. Infected cells do this.

Role of MHC

There are 2 types → Class I MHC and Class II MHC.

● Class I MHC 

○ Produced by infected body cells (a normal cell in the body that got a virus) ■ It takes part of the virus, puts on Class I MHC, and then tells a cytotoxic T cell to kill it.

○ Presents to cytotoxic T cells, which then kills the infected cell.

● Class II MHC 

○ Produced by antigen-presenting cells (macrophages, dendritic cells, B cells) ■ Any one of these macrophages or phagocytic cells that eats a pathogen now has pathogen inside of it.

Still a danger, so we have to also destroy that cell.

■ The antigen-presenting cell puts part of the antigen on its Class II MHC. ○ Recognized by cytotoxic and/or helper T cells.

Here’s how Dr. C keeps them straight: 

Class I → infected. (1 word)

Class II → antigen-presenting (2 words)

Clonal Selection

This is what happens whenever you have a pathogen that enters the body.

- You have all these B cells floating around the blood, which have all different receptors/antibodies on their membrane.

They’re not all going to fit or recognize the antigen. But one will eventually. And when it does, the immune system makes a thousand of the cells. These cells divide over and over again, and start to release tons of antibodies.

You may only have a handful of these cells to recognize that pathogen, but once you have one to recognize it, it divides & now you’ve got a couple hundred thousand to recognize the pathogens.

Cells of the Immune System Remember Past Victories

● Memory B and T cells remain long after the infection

● Upon subsequent infection:

○ Memory B cells form active plasma cells that quickly produce many antibodies ○ Memory T cells form active cytotoxic T cells

All this graph is showing is that when your body is seeing a pathogen for the first time, it could take a week or two before it finds a receptor that fits it.

And during that time, you develop symptoms & get sick.

But, the next time you’re exposed to that pathogen, you already have cells in your body that recognize it.

They find it very quickly, within a day or two, and start to divide and neutralize it before you get sick. That’s why you don’t get the same sickness twice. That’s why vaccines work.

Role of Helper T cells in Acquired Immunity

● Activated helper T cell

○ Secretes cytokines that stimulate other lymphocytes

● Clonal selection produces many active helper T cells and memory helper T cells

Without a doubt, the most important cell in the Adaptive Immune system is the helper T cell. Example: What is the difference between HIV and AIDS? 

- HIV+ becomes AIDS once your helper T cell count drops below a certain number. You can be HIV+ positive, and as long as you have plenty of helper T cells, you’re not sick. But once these helper T cells drop below a certain number, now you’ve got AIDS. That’s what defines it → your helper T cell count.

Can you die of AIDS directly? No.

You die of some secondary infection → Staph, Pneumonia, the flu.

Helper T cells are basically the tattle tales of the immune system.

● That helper T cell releases a ton of cytokines that say to get involved + destroy cell. ● B cells respond to these cytokines by making more plasma cells & antibodies. ● Cytotoxic T cells then respond by coming in & destroying the whole thing.

But without helper T cells, these antigen-presenting cells don’t get recognized & infection runs wild.

Cell-Mediated Response: Cytotoxic T Cells

The way these cytotoxic T cells destroy another cell is pretty savage.

● Bind to virally-infected cells, cells infected by other internal parasites, cancer cells, and transplanted tissues

● Uses perforin, which forms pores in cell membrane, and granzymes - hydrolytic enzymes ● Clonal selection produces many active cytotoxic T cells and memory cytotoxic T cells

Summarized from above:

● They attach to a cell, then they punch holes in the cell using a protein called perforin. ● Then, they essentially pour acid into the cell and dissolve it from the inside out. ● These granzymes break down the cell from the inside out.

The Humoral Immune Response

Humor = blood.

You’ve got: 

antigen-presenting cell (which is a phagocytic cell) → helper T cell, which becomes activated → B cell, which makes more plasma cells → releases a ton of antibodies, and also some memory cells that stick around for the next time.

B Cells

● Activated by cytokines secreted by helper T cells & antigens binding directly to B cells ● B cells attack antigens & microorganisms that are floating in the plasma ● Clonal selection of B cells generates many identical plasma cells and long-lived memory cells

These antibodies bind up these pathogens & that will neutralize pathogen, keeping it from entering another cell.

- The other thing it does → So many of these antibodies will stick to it and make it easier to see other cells.

Look at the clump of cells with all the antibodies on it.

That lets other immune cells recognize it easier.

Disruptions in immune system can elicit or exacerbate disease

● If your immune system fails, this of course can lead to disease or make disease worse. ○ An example of this: allergies, which are hypersensitive immune responses.

Allergies

● Allergies are exaggerated (hypersensitive) responses to antigens (called allergens) ○ If you get exposed to an allergen (which binds to receptors on mast cells), mast cells release histamine.

Histamine is part of the inflammatory response, that’s why allergies make you sniffle, eyes red, nose run. All of those things are a product of inflammation. ■ If you have bad allergies, what type of medicine do you take?

Antihistamines → like Sudafed, Benadryl.

Antihistamines prevent histamine from binding to its receptor causing

inflammatory response.

Autoimmune Diseases

● Conditions where antibodies and immune system cells mistakenly attack the body’s own cells

○ In some cases, your immune system/immune cells are unable to recognize your own cells as being your own cells, so they attack these cells as if they were pathogens.

● Examples:

○ Insulin-dependent diabetes mellitus — Type I diabetes

○ Multiple sclerosis

○ Rheumatoid arthritis

KAHOOT QUESTIONS 

1. Ureters are surrounded by ___________ muscle.

a. Smooth 

b. Skeletal

c. Cardiac

d. Urinary

2. The urethra is longer in ___________.

a. Males 

b. Females

c. Gerbils

d. Nick Saban

3. The dominant vascular component of the nephron is:

a. Bowman’s Capsule

b. The Loop of Henle

c. The Glomerulus 

d. The Collecting Duct

4. What percentage of plasma passes through the glomerulus unfiltered? a. 20%

b. 80% 

c. 67%

d. 25%

5. Transport across the ___________ requires energy.

a. Luminal membrane

b. Interstitial fluid

c. Basolateral membrane 

d. Capillary wall

6. Reabsorption of urea at the end of the proximal tubule is: a. Active

b. Passive 

c. Filthy

d. Disgusting

7. Na+ reabsorption in the proximal tubule is:

a. Variable

b. Obligatory 

8. Reabsorption of glucose and amino acids involves: a. Passive transport

b. Primary active transport

c. Secondary active transport 

d. Tertiary active transport

9. Vasopressin promotes ___________ of water.

a. Reabsorption 

b. Secretion

c. Drying

d. Freezing

10.Filtrate at the bottom of the Loop of Henle is:

a. Dilute

b. Concentrated 

c. Cherry-flavored

d. Pee-flavored

11.Which molecule gets digested first during the digestive process? a. Carbohydrates 

b. Lipids

c. Proteins

d. Crack cocaine

12.Which of these is an accessory organ?

a. Stomach

b. Small intestine

c. Large intestine

d. Pancreas 

13.Which tissue layer provides the most elasticity?

a. Mucosa

b. Submucosa 

c. Muscularis externa

d. Serosa

14.Which enzyme breaks down carbohydrates?

a. Chymotrypsin

b. Amylase 

c. Lipase

d. Bile salts

15.Which sphincter prevents food from exiting the stomach into the duodenum? a. Pharyngeosophageal

b. Gastroesophageal

c. Pyloric 

d. External urethral

16.In which region of the stomach does storage take place?

a. Fundus

b. Body 

c. Antrium

d. Colon

17.Sodium bicarbonate has a ___________ pH.

a. Low

b. High 

c. Beautiful

d. Neutral

18.Which of the following activates pepsinogen?

a. Alkaline mucus

b. HCl 

c. Intrinsic factor

d. Chymotrypsin

19.Which of the following is NOT digested by enzymes released from the pancreas? a. Carbohydrates

b. Lipids

c. Proteins

d. None of the above

20.What are bile salts made from?

a. Sugars

b. Proteins

c. Cholesterol 

d. Enzymes

21.What do chief and parietal cells secrete?

a. HCl 

b. Pepsin

c. Pepsinogen

d. Mucus

22.If you consume 500 mls of alcohol, how much water do you lose? a. 1,000 mls

b. 2,000 mls​ ​(4:1 ratio)

c. None. you’re dead.

d. Too drunk to do math.

23.When the filtrate reaches the distal tubule, it is:

a. Very concentrated

b. Very dilute 

24.Which is considered a ‘drying organ’?

a. Dry valve ductus

b. Large intestine 

c. Small intestine

d. Pancreas

25.During the inflammatory response, cytokines are released by: a. Capillaries

b. Most cells

c. Autoimmune cells

d. Macrophages 

26.Which of the following would NOT attack a cancer cell in your body? a. B cell lymphocyte 

b. Natural Killer cell

c. T cell lymphocyte

d. Your mama

27.Which is smallest?

a. Antigen

b. Epitope 

c. Your dad

28.Class I MHC presents to:

a. Cytotoxic T cells only 

b. Helper T cells

c. None of the above

29.An antigen-presenting cell would present an antigen using its ___________. a. MHC I

b. MHC II 

QUIZ QUESTIONS 

1. The dominant vascular component of the Nephron is:

● Glomerulus

2. Substances moving from the tubule to the blood is tubular __________. ● Reabsorption

3. Transport of Na+ across the __________ cell membrane is active. ● Basolateral

4. Glucose and amino acids are reabsorbed by __________ active transport. ● Secondary

5. Which of the following is typically NOT secreted into the tubule? ● Na+

6. Which of the following is NOT an accessory organ?

● Pharynx

7. Which tissue layer provides the digestive tract with elasticity? ● Submucosa

8. Saliva contains a specific enzyme that begins digestion of __________. ● Carbohydrates

9. Which sphincter muscle, if not contracted, can lead to acid reflux (heartburn)? ● Gastroesophageal

10.The presence of fat in the duodenum will __________ further gastric emptying. ● Prevent

11.Phagocytic cells are an example of __________ immunity.

● Innate

12.During the inflammatory response, capillaries become __________ permeable. ● More

13.Which cells in the Innate immune system attack cancerous cells? ● Natural killer cells

14.True or False: Both B cells and T cells have antigen receptors on their plasma membrane.

● True

15.Class _______ MHC is produced by antigen-presenting cells. ● II

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