Homeostasis And Cell Function Flashcards
Define homeostasis.
- Refers to the maintenance of nearly constant conditions in the internal environment
- it is the condition in which the body’s internal environment remain relatively constant within limits
A homeostatic mechanism is made up of which types of responses?
Adaptive responses
An organism is said to be in homeostasis when its internal environment is?
- contains the optimum concentration of gases, nutrients, ions, and water
- has an optimal temperature
- has an optimal pressure for the health of the cells
Define stress.
- stress is any stimulus that creates an imbalance in the internal environment
Which cation is the most abundant in the extracellular fluid?
- Na+ (sodium)
Which cation is the most abundant int the intracellular fluid?
- K+ (potassium)
Which anion is the most abundant in the extracellular fluid?
- Cl- (chloride)
Define a feedback system.
- Circular situation in which the information about the status of something is continually reported to a central control region
Define a negative feedback loop (Fig. 1-3).
- A change in some parameter (I.e., blood pressure) that causes a response that results in a return of that parameter to normal (baseline)
- The response reverses the direction of the initial condition
What are the characteristics of a a negative feedback loop?
- Diminishes the original change
- Stabilizing
Give an example of a negative feedback loop.
Regulation of arterial blood pressure:
> baroreceptors (type of stretch receptor located in arterial walls) associated with the carotid system sense an increase in arterial pressure
> baroreceptors send inhibitory signals to vasomotor receptors in medulla
> heart pumping capacity is reduced and blood vessels dilate
> arterial pressure decreases
Review figure 1-4 : Recovery of heart pumping caused by negative feedback
Pic
Define a positive feedback loop.
> A change in some parameter causes a responses that continues to change that parameter in the same direction as before
> The input is intensified
What are the characteristics of a positive feedback loop?
> enhance the original change
> destabilizing and can lead to runaway effects
Give an example of a positive feedback loop.
Childbirth
> stretch of the cervix during delivery sends signals that increase the force of uterine contractions which then increase the stretch on the cervix
> NOTE that in this example, there is a natural end to the initial stretch in the form of childbirth, which then terminates the feedback loop
> in most instances, there is no natural end to the feedback, and the process exceeds limits conducive to life
An increase in the production of TSH releasing facto results in an increase in the release of thyroid stimulating hormone, which results in the release of mere thyroxine, which results in a decrease in the production of TSH releasing factor. Is this a negative or positive feedback loop?
This is an example of a negative feed back loop
What is gain?
Gain is the effectiveness with which a control system maintains constant conditions
How is gain calculated?
Gain = correction/ error
> error is the amount of uncorrected increase
> correction is the amount of counteracted increase
Baroreceptors (pressure receptors) in the carotid system sense changes (increases) in the arterial pressure. These baroreceptors send signals to the brainstem where the cardiac centers are located. A feedback system then activates a number of responses that result in a lowering of arterial pressure. Two dogs are used in a study to test the effects of a drug that causes hypertension as a possible side effect. In one of the dogs the baroreceptor feedback system has been inactivated. In the dog with the intact feedback system the arterial pressure increases Fromm 100-110. In the animal with the inactivated control system, the pressure increases from 100-150. What is the effectiveness with which the baroreceptor system controls increase in blood pressure? A. -1 B. -2 C. -4 D. -5
C. -4
Describe the structure of a typical cell membrane with respect to phospholipids and proteins.
Structure:
> All cell membranes (plasma as well as those around organelles) have the same basic structure, referred to as the “unit membrane”
> the unit membrane is a phospholipid bilayer with cholesterol inserted among the phospholipids
> proteins are associated with the membrane
» integral proteins
» peripheral proteins
How are integral proteins associated with the cell membrane?
> Integral proteins are either inserted into the membrane on one side or the other or pass all the way through and are exposed on either side of the membrane
How are peripheral proteins associated with the cell membrane?
> Peripheral proteins are loosely attached to one surface of the membrane or the other and are easily removed
Many peripheral proteins are attached to the membrane via what?
> Glycophosphatidylinositol
What is the purpose of cholesterol in the cell membrane?
> Cholesterol is relatively inflexible and REDUCES MEMBRANE FLUIDITY
List some of the basic functions of the plasma membrane.
> serves as a selective filter and limits what can pass from one side to the other
» lipid soluble substances can general pass readily across the membrane
> plays an integral role in defining the intracellular and extracellular fluid composition
> plays a role in information exchange between the cell and its environment
> intimately involved in exocytosis and endocytosis (pinocytosis and phagocytosis). (Refer to fig. 2-11)
List the major functions of each of the membrane-bound organelles
Nucleus ER Golgi Mitochondria Lysosomes Peroxisomes and endosomes
With which function is clathrin associated? (Fig. 2-11)
> endocytosis (pinocytosis and phagocytosis)
» coated pits (with clathrin) with or without receptors
» form phagocytic vesicles
Describe the characteristics of lysosomes.
Involved in cellular digestion:
> contain hydrolytic enzymes at a low pH
» result in a hydrogen-ion pump
> primary lysosomes fuse with phagocytic vesicles to form secondary lysosomes
> undigested material is left behind within residual bodies
> residual bodies may be eliminated via exocytosis
What organelles are associated with protein synthesis?
> involves ribosomes and endoplasmic reticulum (ER)
» proteins bound for lysosomes or secretion are synthesized on rough ER (RER) to which the ribosomes attach
» proteins bound for the cytoplasm, nucleus, mitochondria, or to other cell membranes are synthesized on free ribosomes
What is the role of the Golgi apparatus?
> plays a role in packaging proteins for secretion:
»I.e., O-glycosylation
> forms lysosomes
> modifies proteins from the RER
What are the ways in which energy is produced?
> glycolysis (anaerobic respiration)
> kreb’s cycle and ETC (aerobic respiration)
Summarize glycolysis.
> glycolysis (anaerobic respiration) >>> begins with glucose >>> occurs in the cytoplasm of all cells >>> does not require oxygen >>> produces pyruvic acid (lactic acid) and a small amount of ATP
Summarize the kreb’s cycle and ETC.
> Kreb’s cycle and ETC (aerobic respiration):
» utilizes pyruvic acid from glycolysis
» can only occur in the mitochondria
» requires oxygen as the final electron acceptor
» produces carbon dioxide and water
» produces much more ATP than glycolysis
What are the types of ways in which cells are able to move?
> ameboid movement
cilia and flagella
microtubules
Summarize ameboid movement.
> ameboid movement (fig. 2-16):
|»_space;> used by macrophages and some other leukocytes
Summarize locomotion via cilia and flagella.
> cilia and flagella (figs. 2-17 and 2-18)
» flagella move cells (The only flagellated cells in humans and other mammals are sperm cells.)
» cilia move other material, usual through a layer of mucous that coats a layer of ciliated cells
» the cells remain stationary
What are the only flagellated cells in humans and other mammals?
> the only flagellated cells in humans and other mammals are sperm cells
Summarize movement via microtubules.
> provide tracks on which motor molecules can move cargos
