parts of a feedback loop, positive & negative feedback loops, passive & active transport, osmosis, hypertonic/isotonic/hypotonic solutions

units 1 and 2 test review topics

what is positive feedback and negative feedback?

• positive feedback-

  • tends to enhance the triggering stimulus

  • keeps the action going and continues it

• negative feedback-

  • returns to body to a homeostatic balance or ideal level

  • start and end are opposites

what are the 6 parts of the feedback loop?

1. variable

2. stimulus

3. receptors/sensors

4. control center

5. effector

6. response

what is the variable in the feedback loop?

the regulated factor or event

what is the stimulus in the feedback loop?

anything that causes change in the variable

what are receptors/sensors in the feedback loop?

• receptors monitor changes

• send signals to control center

• detects change

• ex: nerve endings and receptors

what is the control center in feedback loops?

• compares the value to the normal range

• if the value deviates too much from the set point, then the control enter activates an effector

• determines what is “normal”

• ex: brain or spinal cord

what is the effector in feedback loops?

• structure that carries out the directions from the control center

• causes a change to reverse the situation

• returns the value to the normal range

• ex: glands, muscles, organs

what is the response in feedback loops?

• the effect or output of the system

• release of a substance/action

passive transport conditions and examples

• the movement of substances across the membrane WITHOUT energy

• concentration gradient for movement

• high con. (many solutes) → low con. (few solutes)

• simple and facilitated diffusion

• osmosis (hypertonic, isotonic, hypotonic)

• examples of simple diffusion: O2 and CO2 (2 gases)

• examples of facilitated diffusion: movement of glucose into the cell

active transport conditions and examples

• requires energy from ATP to move materials across membrane

• low con. (few solutes) → high con. (many solutes)

• uses protein channel pumps

• examples-

  • sodium-potassium pump-

    • transports sodium out of a cell while moving potassium into the cell

    • against their concentration gradients

  • endocytosis

  • phagocytosis

  • pinocytosis

  • receptor mediated endocytosis

  • exocytosis

how will molecules/ions spread and diffuse in a concentration gradient?

from an area where there is high concentration → low concentration to balance out and distribute themselves (diffusion)

what is simple diffusion (passive) and examples?

• movement of molecules directly through the membrane

• small and uncharged

• examples (2 gases)-

  • O2 diffuses into cells because it is more concentrated outside of O2

  • CO2 diffuses outside of cells because it is more concentrated inside of CO2

what is facilitated diffusion (passive)?

• requires a protein channel/carrier

• larger and polar molecules

• cannot cross the membrane because of their size, charge, polarity

• examples-

  • the movement of glucose into the cell, where it is used to make ATP

    • glucose transporter transfers glucose into the cell

what is osmosis?

• the diffusion of water through a semipermeable membrane down its concentration gradient

• high con. → low con.

• concentrations of water in osmosis-

  • hypertonic

  • isotonic

  • hypotonic

what is isotonic in relation to osmosis?

• 2 solutions that have the same concentration of solutes and water molecules outside and inside the cells

• cells maintain their normal shape and function

when does osmosis occur?

• when there is an imbalance of solutes outside the cell vs. inside the cell

• low solute con. → high solute con.

• high water con. → low water con.

what is hypertonic solution?

• higher solute concentration outside the cell

• water moves out of the cell

• cells shrink and dehydrate

• high con. to low con. for balance

what is a hypotonic solution?

• lower solute concentration outside of the cell than inside

• water moves into the cell

• cells swell and burst