BIO 321 Exam 1

Homeostasis

Process of maintaining relatively stable internal conditions in your body, even when things around you change

The human body’s internal temperature is

near 37º C

What is a receptor

Protein on or inside a cell that detects a specific signal and helps trigger a response

What is the main function of a receptor?

To receive signals and help the cell respond appropriately

Where are receptors located?

On the cell membrane or inside the cell

When acetylcholine binds to certain receptors on a muscle cell, it helps initiate muscle contraction.—> what is this an example of?

A receptor in the nervous system

What is a ligand?

A molecule, such as a hormone or neurotransmitter, that binds to a receptor

What happens when a ligand binds to a receptor?

The receptor may become activated and start a response inside the cell

How does acetylcholine help trigger muscle contraction?

Acetylcholine binds to receptors on the muscle cell, initiating events that lead to contraction.

Hypothalamus

the body's control center that helps keep internal conditions stable

When your body temperature rises, the ___________ detects the change and activates responses such as sweating to help cool you down

hypothalamus

homeostasis + autonomic nervous system + hormone regulation =

Hypothalamus

What does hypertonic mean?

A solution that has a higher concentration of nonpenetrating solutes compared to another solution, such as the inside of a cell.

What happens to a cell placed in a hypertonic solution?

Water moves OUT of the cell by osmosis, causing the cell to shrink.

Why does water leave a cell in a hypertonic solution?

Because the outside has a higher concentration of nonpenetrating solutes, water moves out of the cell by osmosis.

What is a nonpenetrating solute?

A dissolved substance that cannot cross the cell membrane, so it stays on its side of the membrane.

What is a nonpenetrating solution?

A solution containing solutes that cannot pass through the cell membrane.

What is osmosis?

The movement of water across a selectively permeable membrane from an area of lower nonpenetrating solute concentration to an area of higher nonpenetrating solute concentration.

Why are nonpenetrating solutes important in osmosis?

They create differences in effective solute concentration across the membrane, which cause net water movement.

What happens when a cell is placed in a hypertonic solution?

The outside has a higher concentration of nonpenetrating solutes. Water moves OUT of the cell by osmosis, causing the cell to shrink.

__________ specifically refers to water moving across a selectively permeable membrane.

Osmosis

____ is the net movement of particles down their concentration gradient

Diffusion

A membrane that allows substances, such as water and certain molecules, to pass through it.

Permeable membrane

Membrane that does not allow a particular substance to pass through.

Impermeable

Membrane that allows some substances through but prevents others.

Selectively permeable

osmosis =

passive movement of water

negative feedback =

a regulated response that opposes a disturbance

sensor =

detects

integrating sensor =

processes

effector =

responds

If the effector fails, the body may detect a __________ but cannot properly correct it through that pathway.

disturbance

Homeostasis prevents all changes.

False

Homeostasis operated during extreme conditions. True or false?

False

Why is homeostasis considered a dynamic process?

the body continuously adjusts its physiological processes to maintain stable internal conditions within a normal range

Phospholipid bilayer consists of:

Hydrophilic heads and hydrophobic tails

Why can oxygen cross through the phospholipid bilayer?

It is small, non polar, and uncharged

True or false

Oxygen can pass directly through the phospholipid bilayer through simple diffusion

True

Sodium cannot easily cross phospholipid bilayer because

Na⁺ is positively charged and surrounded by water molecules in solution

True or false

Because the membrane's interior is hydrophobic, sodium cannot easily cross without a transport protein.

True

Why can oxygen cross the cell membrane directly, but sodium cannot?

Oxygen is small and nonpolar, allowing it to pass through the phospholipid bilayer. Sodium is charged and requires a membrane transport protein.

What is diffusion?

The net movement of molecules from an area of higher concentration to an area of lower concentration.

What are the two types of diffusion?

Simple and facilitated

Do simple and facilitated diffusion require ATP?

No

True or false

Both simple and facilitated diffusion are forms of passive transport

True

Does diffusion stop when equilibrium is reached?

No

Why does diffusion not stop when equilibrium is reached?

Molecules continue moving randomly in both directions, but there is no net movement because the opposing rates are equal.

What is the difference between simple diffusion and facilitated diffusion?

Both are passive transport processes that move substances down their gradients. Simple diffusion does not require a transport protein, while facilitated diffusion does.

Carrier proteins have a limited number of binding sites and take time to complete each transport cycle.

If all carriers are working at their maximum rate, adding more substrate will not increase transport speed further.

This is called ___________.

transport saturation

At high glucose concentrations:

More glucose molecules are available.

More carriers become occupied.

Eventually, nearly every carrier is operating at its maximum rate.

Adding additional glucose no longer increases transport speed significantly.

This is called ___________.

carrier saturation

Why does carrier-mediated transport reach a maximum rate?

carrier proteins are limited in number. Once all carriers are operating at maximum capacity, increasing substrate concentration cannot significantly increase transport speed.

What is the net water movement and result of hypertonic solution?

Water moves OUT, and cell shrinks

What is the net water movement and result of hypotonic solution?

Water moves IN, and cell swells

What is the net water movement and result of isotonic solution?

No net movement, and cell stays approximately the same size

Water moves into the cell through osmosis, and the red blood cells swells and may eventually burst, this is called…

Hemolysis

What happens when a red blood cell is placed in a hypotonic solution?

Water enters the cell by osmosis, causing it to swell and potentially burst.

Osmolarity

The total concentration of dissolved particles in a solution ( includes both penetrating and non penetrating solutes)

Tonocity

The effect a solution has on cell volume based on the concentration of effectively nonpenetrating solutes.

What does tonicity tell you about what a cell will do?

It tells you whether it will shrink, swell, or stay approximately the same size.

Imagine two solutions that both have an osmolarity of 300 mOsm/L.

~Solution A contains 300 mOsm/L of nonpenetrating solutes.

~Solution B contains 300 mOsm/L of freely penetrating solutes.

Although both have the same osmolarity, they may affect cell volume differently.

Because penetrating solutes can move across the membrane and may not sustain the osmotic gradient that determines the cell's final volume.

Can two solutions have the same osmolarity but different tonicities?

Yes! Osmolarity counts all dissolved particles, while tonicity depends on effectively nonpenetrating solutes and predicts changes in cell volume.

What is active transport?

Active transport uses energy to move substances against their concentration or electrochemical gradients.

Passive or active transport?

Down a gradient, no direct energy input required

Passive

Passive or active transport?

Against a gradient, requires an energy source

Active

What are the two types of active transports?

Primary and secondary

Primary or secondary active transport?

Uses energy directly from ATP hydrolysis.

Primary

For every ATP molecule hydrolyzed, the pump moves:

3 Na⁺ OUT of the cell.

2 K⁺ IN to the cell.

Both are transported against their electrochemical gradients under typical physiological conditions.

This helps maintain ion gradients necessary for membrane potential and electrical signaling.

The following is describing what? It is an example of what?

Sodium-potassium pump, and primary active transport

Primary or secondary active transport?

Uses energy stored in an ion gradient, commonly the sodium gradient, instead of directly hydrolyzing ATP at the cotransporter

Secondary

Sodium moves down its electrochemical gradient, and that energy helps move glucose against its gradient.

The sodium gradient is maintained by the sodium-potassium pump, so secondary active transport still depends indirectly on ATP.

This is an example of what?

Sodium-glucose cotransporter is an example of secondary active transport

Does primary active transport directly use ATP?

Yes

Does secondary active transport directly use ATP?

No

What is the energy source of primary active transport?

ATP hydrolysis

What is the energy source for secondary active transport?

Existing ion gradient

what is a dynamic process?

a process involving continuous movement or change over time

How does the sodium-potassium pump work?

It’s a protein in the cell membrane that uses energy from ATP to move ions against their concentration gradients

For every sodium-potassium pump cycle, how many Na + and K+ are moving? In which direction? Is any ATP being used?

• 3 Na⁺ move OUT of the cell.

• 2 K⁺ move IN to the cell.

• 1 ATP is used

3 Na⁺ OUT, 2 K⁺ IN, 1 ATP

is for what?

every cycle of the sodium-potassium pump

Finish the sentence:

The sodium-potassium pump helps ______ the Na⁺ and K⁺ _______ ________ that are essential for membrane potentials and action potentials.

However, the rapid changes during an action potential occur mainly through__________, not directly through the _______.

maintain, concentration gradients, voltage-gated ion channels, pump

How does calcium control skeletal muscle contraction?

Calcium binds to troponin, causing tropomyosin to move away from the myosin-binding sites on actin, allowing myosin to bind and generate force.

SERCA =

Sarcoplasmic reticulum calcium pump

Temporal summation

The muscle fibers receive repeated signals close together, so their force responses overlap.

Motor-unit recruitment

Your nervous system activates additional groups of muscle fibers to produce more total force.

Electrical refractory period

A short period after an action potential when the muscle fiber cannot immediately generate another normal action potential.

Mechanical relaxation

The longer process during which muscle force decreases as calcium is removed from the cytosol

Muscle twitch

A brief contraction and relaxation following one stimulus.

EMG stands for

electromyography

_______ is a technique used to record the electrical activity associated with muscle activation.

electromyography

List out how EMG differs from muscle force

measures electrical activity, records using electrodes, can reflect muscle activation, can increase w/o force doubling

List out how muscle force differs from EMG

Measures mechanical output, measured using a force sensor or dynamometer, shows how much force a muscle produces, and cannot be calculated directly from EMG amplitude alone

EMG applitude can change because of… (4 reasons)

the # of active motor units, motor-unit firing patterns, electrode position and signal detection, and other physiological conditions

dynamometer

a device used to measure force or torque, depending on its design

what are two ways to measure force directly?

dynamometer and force transducer