Homeostasis Flashcards
Maintenance of relatively stable internal conditions
Homeostasis
“homeo” means
same
Regulates and maintains balance through hormonal signals
endocrine system
“stasis” means
standard scale
Responsible for analyzing and
responding to information.
Nervous system (brain)
→ A disturbance in homeostasis results
in disease
→ Maintaining balance is vital for
normal physiological functions.
→ Disruptions can lead to conditions
like diabetes, where blood sugar levels are not properly regulated, or affect heart rate and blood pressure.
Homeostatic imbalance
receptors send information to control center using what kind of pathway
afferent pathway
→ Sensory neurons in the body that
detect or responds to changes in the
environment (stimuli)
Receptor
→ Determines set point
→ Analyzes the information
→ Usually the brain, which processes
the information received and determines on the appropriate response to the stimulus
Control center
Provides a means of response to the
stimulus
effector
Includes most homeostatic control
mechanisms
→ Shuts off the original stimulus or reduces its intensity
→ This is the body’s way of reducing the intensity of a stimulus to restore balance. It works like a thermostat in a household.
Negative feedback
information flows from control center to effector along what kind of pathway
efferent pathway
This produces change in variable
Stimulus
→ Rare in the human body
→ Increases the original stimulus to
push the variable farther
→ Reaction occurs at a fasterr ate
Positive feedback
Homogenous mixture of two or more components
Solution
Dissolving medium present in the larger quantity; the body’s main solvent is water
Solvent
Solution inside the plasma membrane
Nucleoplasm and cytosol
→ Solution containing gases, nutrients
and salts dissolved in water
intracellular fluid
components in smaller quantities within a solution
solutes
→ Is a selectively permeable barrier
→ Controls what substances can pass
through it, allowing certain materials
in and keeping others out.
Plasma membrane
→ Substances are transported across
the membrane without any input from the cell
→ Movement of molecules across the cell membrane without requiring energy (ATP).
→ Molecules move from areas of higher concentration to areas of lower concentration.
Passive transport
→ Fluid on the exterior of the cell
→ Contains thousand of ingredients
such as nitrogen, hormones neurotransmitters, salts, waste products
extracellular fluid
2 types of passive transport
Diffusion and osmosis
→ The cell provides the metabolic
energy (ATP) to drive the transport
process
→ Molecules move from areas of lower
concentration to areas of higher concentration.
Active transport
2 types of active transport
exocytosis and endocytosis
Movement of small, soluble
molecules through the plasma membrane without energy.
diffusion
Have the same solute and water concentrations as cells and cause no visible changes in the cell
Isotonic
→ An unassisted process
→ Solutes are lipid soluble or small
enough to pass through membrane pores without the need for energy (ATP).
Simple diffusion
highly polar water molecules easily cross the plasma membrane through _____
aquaporins
→ Simple diffusion of water across a
selectively permeable membrane
osmosis
Contain more solutes than the cells do; the cells will begin to shrink
→ There is greater concentration outside the cell; molecules always tend to a higher concentration
Hypertonic solutions
in hypotonic solutions, water moves into the cell, causing it to swell. This is known as ______.
cytolysis
In hypertonic solutions, water moves out of the cell causing it to shrink. This is called
plasmolysis
molecules pass through the cell membrane via protein channels or carriers without the need for energy (ATP).
facilitated diffusion
→ Water and solutes are forced through a membrane by fluid, or hydrostatic, pressure
→ A pressure gradient must exist that pushes solute-containing fluid (filtrate) from a high-pressure area to a lower-pressure area
→ This is critical for the kidneys to work properly
filtration
→ Contain fewer solutes (more
water) than thee cells do; cells
will plump
→ Lower concentration of solutes
outside the cell
hypotonic
Movement of molecules across the
membrane against their concentration gradient, which requires energy (ATP).
Active transport
→ Necessary for nerve impulses
→ It uses ATP to transport sodium out of
the cell and potassium into the cell.
→ ATP phosphorylates the pump protein, causing a change in shape that moves sodium out of the cell. When the phosphate group is released, the protein returns to its original shape, allowing potassium to enter the cell.
sodium-potassium pump
The _______ binds to the molecule, changes shape, and transports it across the membrane.
protein carrier
→ substances are moved across the
membrane “in bulk” without actually
crossing the plasma membrane
Vesicular transport
→ Mechanism cells use to actively secrete hormones, mucus, and other products
→ Material is carried in a membranous
sac called a vesicle that migrates to and combines with the plasma membrane
→ Contents of vesicle are emptied to the outside
→ The vesicle, containing proteins or other substances, moves to the plasma membrane. DOcking proteins on both the vesicle and the membrane ensure proper fusion, and the vesicle releases its contents outside the cell
Exocytosis
→ The process by which the cell engulfs
external substances, forming a vesicle that detaches from the membrane and enters the cell.
→ Extracellular substances are enclosed (engulfed) in a membranous vesicle
→ Vesicle detaches from the plasma membrane and moves into the cell
→ Once in the cell, the vesicle typically fuses with a lysosome
→ Contents are digested by lysosomal enzymes
→ In some cases, the vesicle is released by exocytosis on the opposite side of the cell
endocytosis
→ “Cell eating”
→ A form of endocytosis where pseudopods (extensions of the cell membrane) engulf large particles, such as bacteria, forming a vesicle inside the cell. This is a key mechanism for the immune system to remove invaders.
Phagocytosis
The cell engulfs droplets of extracellular fluid, including dissolved
substances.
Pinocytosis
→ A highly selective form of endocytosis
where specific molecules, such as hormones or nutrients, bind to receptors on the cell surface and are brought into the cell.
→ Method for taking up specific target molecules
Receptor-mediated endocytosis
