Bio 108 Quiz 5

Homeostasis

the process by which biological systems maintain stability while adjusting to changing conditions

What are internal environment challenged by?

external environment and metabolic activities

What do physiological systems aim to maintain?

optimal physical and chemical environment for all metabolic processes

Control systems

sense when conditions deviate from ‘normal’ and initiate physiological mechanisms to correct the error

Control systems components

Sensors/receptors, control center and effectors

Sensors/receptors

monitor conditions and send info

Control Center

obtain, integrate and process info

effectors

issue commands

Controlled variable set point

reference point

Feedback information

info that is compared to the set point by the sensor

error signal

any difference between the set point and feedback info

Effector

tissues or organs that can alter the internal environment

Positive feedback

amplifies a response and increases deviation from a set point (pushes systems away homeostatic balance)

Negative feedback

info that returns to set point (returns system to homeostatic balance). Most physiological systems relay on negative feedback.

Example of positive feedback loop

Childbirth: progressively increasing uterine contractions stimulated by stretching of the cervix by the head of the baby

Cell signaling

Cells can send/receive, process, and respond to information from the intracellular and extracellular environments. Responsible for maintaining homeostasis.

Steps of signaling pathways

1. Reception

2. Transduction

3. Response

Steps of signaling pathways: Reception

Step 1. info is transmitted by signal and received by receptor

Steps of cell signaling: transduction

Step 2. conversion of signal to a cellular response

Steps of signaling pathways: response

step 3. changes in cell behavior in response to the signal

Cell signaling modes of source and delivery

juxtacrine, autocrine, no response, paracrine and endocrine

Juxtacrine

cell signaling requiring physical contract

autocrine

cell signaling at a local level, effects cell that produced the signal (self-signaling)

No Response

not the target cell, thus no receptors

Paracrine

cell signaling at a local level, signal affects nearby cells

Endocrine

cell signaling from a distance, signal travels to distant cells - hormones

Receptors

protein structures that wait for specific signals. They can be found in two main locations: intracellular or embedded in the membrane

Intracellular receptors

Located inside the cell (within the cytoplasm or nucleus). These bind to ligands that are small and non-polar enough to pass through the cell membrane

Embedded receptors

Embedded directly in the plasma membrane. These bind to ligands that stay on the outside of the cell because they cannot pass through the lipid bilayer.

Where do cell signals come from?

Ligands can come from the environment (outside organism), chemical or physical stimuli.

Receptors and ligands relationship

Receptors are highly specific, meaning they will only bind to a specific type of ligand. This ensures that cells only respond to the signals meant for them.

What happens when a receptor binds to a specific ligand?

triggers a conformational change in the receptors shape, acts as a switch that activates the receptor. When activated, the receptor initiates subsequent events inside the cell, starting the process of signal transduction

When a signal molecule binds to a membrane-bound receptor, what properties does it have?

Large and polar