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Chapter 21
Endocrine System
60
Physiology
Undergraduate 1
04/28/2010

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Term
Anabolism
Definition
  • or biosynthesis, is the process by which living organisms synthesize complex molecules of life from simpler ones
  • together with catabolism, are the two series of chemical processes in cells that are, together, called metabolism
  • requires input of energy "uphill process"
Term
Catabolism
Definition
  • produce smaller molecules used by the cell to synthesize larger molecules
  • "downhill" process during which energy is released
Term
Describe Glucose Tranporters in the blood
Definition
  1. Inside cells, glucose can be oxidized for energy
  2. which generates carbon dioxide as a waste product; provides substrates for other metabolic reactions
  3. or be converted to glycogen for storage
  4. if glucose levels in the cell decrease, glycogen can be broken down to glucose by glycogenolysis

 

Term
Describe amino acids in the blood
Definition

 

  1. amino acids are used for the synthesis of proteins
  2. or catabolized for energy by proteolysis
  3. the proteins function as amino acid stores that can subsequently be broken down to amino acids
  4. which can then be catabolized for energy or released into the bloodstream for use by other cells
Term
What three metabolic pathways ar necessary for the handling of glucose
Definition
  • Glycolysis
  • Krebs cycle
  • Electron transport chain
Term
Triglycerides are  transported in the bloodstream in
Definition
lipoproteins, small protein- and lipid- containing particles
Term
To facilitate entry into cells, triglycerides at the outer surface of lipoproteins are broken down by the enzyme
Definition
  • lipoprotein lipase
    • which is located on the inside surface of capillaries throughout the body and is particularly dense in capillaries running through adipose tissue (body fat)
Term
Lipoprotein lipase breaks down triglycerides into
Definition
  • fatty acids and monoglycerides
    • fatty acids are then taken up by nearby cells
    • monoglycerides remain in the bloodstream and are eventually metabolized in the liver
Term
Adipocytes
Definition
adipose tissue cells that are specialized for fat storage
Term
On entering cells, fatty acids may be oxidized fo energy or combined
Definition
  • with glycerol to form new triglycerides
    • which are stored in fat droplets in the cytosol
    • storage occurs mainly in adipocytes
Term
Stored triglycerides can subsequently be broken down to glycerol and fatty acids which can be
Definition
  • catabolized for energy or released into the bloodstream for use by other cells
Term
The catabolism of glycerol and fatty acids produce
Definition
carbon dioxide as a waste product
Term
Positive energy balance
Definition

When a person takes in energy at a rate greater than that at which it is expended as heat and work.

 

Increase body weight

Term
Negative energy balance
Definition

when the rate of energy intake is less than the rate at which energy is expended as heat or work, the quantity of stored energy decreases

 

decreases in body weight

Term
Absorptive State
Definition
  • 3-4 hours after a typical meal, nutrients are absorbed
  • rate of energy input generally exceeds energy input
  • body is in postive energy balance
  • glucose serves as the primary energy source for cells, while fats amino acids, and excess glucose are takin up by the liver, muscle, and fat cells and converted to energy storage molecules
Term
Postabsorptive State
Definition
  • between meals, when nutrients are not being absorbed
  • glucose serves as the energy source for cells in the central nervous sytem
  • other cells in the body utilized other energy sources sparing glucose for the central nervous sytem

 

Term
The absorptive state is primarily an anabolic state; that is the majority of reactions involve synthesis of
Definition
macromolecules
Term
What nutrient molecules does live convert
Definition
  • glucose to glycogen (fatty acids)
  • fattyacids to triglycerides
Term
VLDLs
Definition

very low density lipoproteins

 

transport triglycerides to the cells of the body

Term
Triglycerides synthesized in the liver are transported to
Definition
adipocytes by VLDLs for storage
Term
Because glucose is derived from the breakdown of glycogen, which is in relatively short supply (enough to last only a few hours), how is glucose made available for longer periods?
Definition
The body synthesizes new glucose from amino acids, glycerol, and other breakdown products of catabolism, a process known as gluconeogenesis
Term
Glucose Sparing
Definition
Most tissues turn almost exclusively to other energy sources, primarily fatty acids, thereby conserving glucose for use by the central nervous system
Term
When the liver converts amino acids, lactate, or pyruvate to glucose, what type of process is occuring
Definition
Gluconeogenesis
Term
What does the central nervous system acquire the ability to use for energy
Definition

Ketones

 

The production of ketones is important because during prolonged fasting, the central nervouls system acquires the ability to use ketones for energy, thereby freeing it from some of its dependence on glucose

Term
When glucose or amino acids are absorbed in excess of the quantities oxidized or stored as glycogen or proteins, what happens to them
Definition
fats, amino acids, and excess glucose are stored in the liver, muscle, and fat cells and converted to energy storage molecules
Term
During the absorptive state, energy is stored in
Definition
macromolecules
Term
Insulin promotes the synthesis
Definition
of energy storage molecules and other processses characteristic of the absorptive state
Term
The metabolic adjustments that occur as the body switches between the postabsorptive and absorptive states are largely triggered by changes in the
Definition
plasma concentration of insulin, a peptide hormone secreted by beta cells located in the pancreatic islets of Langerhans
Term
During the absorptive period, plasma glucose levels do what
Definition
  • increase, as glucose is transported into the bloodstream from the GI tract
  • this stimulates insulin secretion by a direct effect of  glucose on beta cells
Term
During the postabsorptive period, plasma glucose levels do what
Definition
  • decrease, causing insulin secretion to fall
Term
What happens to insulin secretion when plasma amino acid concentration rises
Definition
increases insulin secretion
Term
What happens to insulin secretion when plasma amino acid concentration decreases
Definition
decreased insulin secretion
Term
What else stimulates insulin secretion
Definition
  • hormones
  • input from the autonomic nervous system
    • parasympatheitic
  • glucose-dependent insulinotropic peptide (GIP)
    • a hormone secreted by cells in the wall of the gastrointestinal tract
Term
Insulin promotes energy storage by stimulating the synthesis of
Definition
  • fatty acids and triglycerides in the liver and adipose tissues
  • glycogen in the liver and skeletal muscle
  • proteins in most tissues
Term
Insulin opposes the catabolism of energy stores by
Definition
  • inhibiting the breakdown of proteins, triglycerides, and glycogen
  • suppressing gluconeogenesis by the liver
Term
Insulin affects the transport of nutrients across the membranes of all body cells except
Definition
  • those of the liver and central nervous system
Term
GLUT 4
Definition

Glucose transport proteins in cell plasma membranes

 

found in

  • skeletal muscle
  • adipose tissue
Term
What does insulin stimulate the uptake of
Definition
  • amino acids - which facilitates the hormone's stimulatory effect on protein synthesis
  • glucose - increases the number of glucose transport proteins in cell membranes (GLUT 4)
Term
What does insulin not have an effect on
Definition
  • transport of glucose in the central nervous system and liver
  • glucose permeability of cells in exercising muscle
Term
Glucagon
Definition

a peptide hormone secreted by alpha cells of pancreatec islets of Langerhans

 

promotes processes of the postabsorptive state

Term
Insulin and glucagon are antagonists, hormones whose actions oppose each other, what does what
Definition
  • insulin promotes processes of the absorptive state
  • glucagon promotes processes of the postabsorptive state
Term
Decrease in blood glucose stimulate what in gucagon secretion and insulin secretion
Definition
  • stimulate glucaton secretion
  • inhibit insulin secretion
Term
Glucagon secretion is stimulated by
Definition
  • sympathetic nervous activity and epinephrine
    • which have a suppressive effect on insulin secretion
Term
In the liver, glucagon promotes
Definition
  • glycogenolysis and gluconeogenesis (which increase blood glucose levels)
  • ketone synthesis
  • breakdown of proteins

while inhibiting the opposing processes of glycogen and protein synthesis.

Term
Actions of glucagon in adipose tissue
Definition
glucagon stimulates lipolysis and suppresses triglyceride synthesis
Term
What is the normal fasting level of glucose in the blood
Definition
70-110 mg/dL
Term
Hyperglycemia
Definition

Fasting blood levels greater than 140 mg/dL

 

indicative of diabetes mellitus

Term
Hypoglycemia
Definition

Fasting blood levels below 60 mg/dL

 

 

has widespread deleterious effects on nervous system function because the nervous system uses glucose almost exclusively as its source of energy

Term
Insulin and glucagon together control what
Definition

plasma glucose concentration through negative feedback

 

  • increase in plasma glucose concentration increases insulin secretion and decreases glucagon secretion from the pancreas, both of which cause a decrease in plasma glucose
Term
A decrease in plasma glucose concentration does what
Definition

decreases insulin secretion

increases glucagon secretion

 

both of which cause an increase in plasma glucose

Term
Insulin decreases plasma glucose concentration in three ways during insulin negative feedback
Definition
  1. by promoting the uptake of glucose into cells by in creasing the number of glucose transporters in the plasma membrane
  2. by reducing the concentration of free glucose within cells by converting it to glycogen, which promotes glucose uptake by increasing the size of the glucose concentration gradient
  3. by suppressing gluconeogenesis, thereby reducing the rate at which new glucose is released into the bloodstream
Term
Insulin decreases plasma glucose concentration by promoting the uptake of what during insulin negative feedback
Definition
glucose into cells by increasing the number of glucose transporters in the plasma membrane
Term
By reducing the concentration of free glucose within cells by converting it to glycogen, promotes what during insulin's negative feedback
Definition
glucose uptake by increasing the size of the glucose concentration gradient
Term
by suppressing gluconeogenesis this does what during insulin negative feedback
Definition
reduces the rate at which new glucose is released into the bloodstream
Term
If plasma glucose concentation deceases, insulin does what during insulin negative feedback
Definition
secretion deceases, causing a increase in plasma glucose
Term
Glucagon's negative feedback
Definition
  • decease in plasma glucose stimulates glucagon secretion from alpha cells of the pancreas
  • and the actions of glucagon increase plasma glucose
Term
During glucagon's negative feedback, glucagon
Definition
  • increases plasma glucose concentration by promoting gluconeogenesis and glycogenolysis in the liver
    • which directly increases plasma glucose concentration
  • by stimulating lipolysis in adipose tissue
    • which provides fatty acids as an alternate energy source to glucose
Term

During glucagon's negative feedback, glucagon

       increases

Definition
  • plasma glucose concentration by promoting gluconeogenesis and glycogenolysis in the liver
    • which directly increases plasma glucose concentration

 

Term
During glucagon's negative feedback, glucagon stimulaties lipolysis in
Definition
  • adipose tissue
  • which provides fatty acids as an alternate energy source to glucose
  • Term
    An increase in plasma amino acids stimulates
    Definition

    the release of both insulin and glucagon

    • nutrients are absorbed, plasma amino acid levels rise
    • glucose levels do not change
    • stimulation of insulin
      • promotes amino acid uptake by cells
      • promotes decease in plasma glucose
    • rise in plasma amino acids stimulates secretion of glucagon
      • increase inplasma glucose
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