Cell Physiology
What is the movement of water across a selectively permeable membrane called?
Osmosis
What ion enters a neuron during depolarization?
Na⁺
What protein makes up the thin filament and what protein makes up the thick filament?
Thick- Myosin
What organ pumps blood throughout the body?
The heart
Which two systems work directly together to produce voluntary movement?
Nervous and muscular systems
What is the difference between diffusion and active transport?
Diffusion moves substances down their gradient without energy; active transport uses energy to move substances against their gradient.
Why does opening Na⁺ channels depolarize a neuron?
Na⁺ enters the cell, bringing positive charge inside and making the membrane more positive.
What does Ca²⁺ do during muscle contraction?
Ca²⁺ binds to troponin, causing tropomyosin to move and expose binding sites on actin.
What is the difference between arteries and veins?
Arteries carry blood away from the heart; veins carry blood toward the heart.
You start exercising. Why does your heart rate increase?
To increase blood flow and oxygen delivery to active tissues.
A cell is placed in a solution with a much higher solute concentration than the cell. What happens to the cell?
Water leaves the cell, causing it to shrink.
If a neurotransmitter causes the next neuron to become more negative, would it be more or less likely to fire an action potential?
Less likely.
What would happen if Ca²⁺ were not released from the sarcoplasmic reticulum?
The actin binding sites would remain blocked, so normal contraction could not occur.
During exercise, why does the heart rate increase?
To increase cardiac output and deliver more oxygen and nutrients to active tissues.
Trace a nervous signal from the brain to a skeletal muscle.
Brain → motor neuron → axon terminal → neurotransmitter release → muscle fiber → Ca²⁺ release → contraction.
Explain how the Na⁺/K⁺ pump helps maintain the conditions necessary for cell function.
It maintains Na⁺ and K⁺ concentration gradients across the membrane, which are important for membrane potential, transport, and cell signaling.
Explain the basic sequence of an action potential.
Threshold → Na⁺ channels open → Na⁺ enters → depolarization → Na⁺ channels inactivate → K⁺ exits → repolarization → hyperpolarization → return toward resting potential.
Explain how a signal from a motor neuron causes a muscle fiber to contract.
ACh is released → muscle membrane depolarizes → signal travels through the muscle → Ca²⁺ is released → Ca²⁺ binds troponin → tropomyosin moves → actin/myosin interact → contraction occurs.
Explain how blood gets from the heart to body tissues and back.
Heart → arteries → arterioles → capillaries → venules → veins → heart.
What would happen if voltage-gated Na⁺ channels could not open?
Normal action potentials could not be generated.
A cell's Na⁺/K⁺ pump stops working. WHY would this eventually affect the cell's membrane potential?
The pump maintains Na⁺ and K⁺ concentration gradients. Without it, the gradients gradually break down, disrupting the membrane potential.
WHY does the nervous system need ion gradients to communicate?
Ion gradients create the electrical differences across cell membranes → those differences allow action potentials → action potentials allow neurons to communicate and control muscles and organs.
WHY does exercise require both ATP production and oxygen delivery?
ATP powers muscle contraction → exercise increases ATP demand → cardiovascular and respiratory systems deliver O₂ → cells use O₂ for aerobic ATP production → ATP supports continued contraction.
WHY does exercise increase both heart rate and breathing rate?
Exercise increases muscle ATP demand → muscles need more O₂ and produce more CO₂ → breathing increases gas exchange → heart rate increases O₂ delivery and CO₂ removal.
You suddenly stand up after lying down. Explain WHY your body has to make adjustments to maintain blood pressure.
Standing causes blood to pool in the lower body due to gravity, temporarily reducing venous return and potentially lowering blood pressure. The cardiovascular and nervous systems respond by adjusting heart rate, cardiac output, and blood vessel diameter to help maintain adequate blood pressure and blood flow.