Comprehensive Human Physiology: Homeostasis, Circulatory, Respiratory, and Muscular Systems

What are the three types of fluids in the body?

Intracellular fluid, extracellular fluid, and external environment.

What is the significance of managing interactions between body fluids?

It is key to maintaining homeostasis.

Why is equilibrium considered a theoretical concept in the human body?

Because the amounts of substances are always changing.

What is compartmentalization in the context of body fluids?

It refers to anatomical cavities and functional body fluid compartments.

What does the thoracic cavity contain?

The diaphragm and organs for breathing, including the pericardial sac which contains the heart.

What are tight junctions?

Connections that bind cells tightly enough to prevent fluid circulation between them.

What is the function of gap junctions?

They allow fluid to move between cells for communication.

What do anchoring junctions do?

They hold cells together and to the extracellular matrix.

What is epithelial tissue?

Boundary tissues that divide the body from the outside environment.

What is the structure of epithelial cells?

They are long and thin, with an apical side facing the lumen and a basolateral side anchoring to other cells.

What is the role of the apical surface in epithelial tissue?

It often has adaptations to protect against harsh conditions, such as stomach acid.

What are the five functional categories of epithelial tissue?

Exchange, transporting, ciliated, protective, and secretory epithelium.

What is the function of exchange epithelium?

To facilitate passive exchange of substances, such as in capillaries.

How does transporting epithelium function?

It uses tight junctions to prevent movement between cells and transports substances actively.

What is the role of ciliated epithelium?

To create fluid currents that help move substances across the tissue surface.

What defines protective epithelium?

It consists of many stacked layers of cells that protect the interior of the body.

What is secretory epithelium?

Tissue that produces and releases substances, such as mucus from goblet cells.

What is connective tissue?

A diverse category that includes tendons, bones, adipose tissue, and blood.

What are excitable tissues?

Nervous tissue and muscle tissue that can respond to stimuli.

What is osmosis?

The movement of molecules across a membrane until concentration is equal on both sides.

What is osmotic pressure?

The pressure required to prevent the movement of water across a selectively permeable membrane.

What drives osmosis?

Entropy, as the solute is diluted by water.

What is the typical physiological osmolarity value for humans?

280-296 mOsM, commonly rounded to 300 mOsM.

What is tonicity?

The effect of a solution on cell volume, considering selectively permeable membranes.

What happens to a cell in a hypotonic solution?

The cell swells as water moves in due to a higher solute concentration inside.

What occurs in a hypertonic solution?

The cell shrinks as water moves out due to a lower solute concentration inside.

What is facilitated transport?

The process of moving substances across a membrane, either passively or actively.

What is the sodium-potassium pump?

A mechanism that pumps three sodium ions out of the cell and two potassium ions in, using ATP.

What is exocytosis?

The process of expelling substances from a cell via vesicles.

What is endocytosis?

The process of taking substances into a cell by engulfing them in a vesicle.

What is local communication in cells?

Communication that occurs through mechanisms like gap junctions, contact-dependent signals, and autocrine/paracrine signaling.

What are gap junctions?

Cytoplasmic connections between adjacent cells that allow for direct communication, often used in muscle tissues.

What is the role of contact-dependent signals?

They require direct contact between the membranes of adjacent cells to transmit signals, such as stopping cell division.

What is the difference between autocrine and paracrine signaling?

Autocrine signals act on the same cells that secrete them, while paracrine signals act on nearby cells.

How do neurons use paracrine signaling?

Neurons release neurotransmitters that diffuse across small gaps to communicate with adjacent cells.

What is the function of nitric oxide in vascular endothelial cells?

It controls vasodilation and constriction by signaling local cells based on their oxygen needs.

What is long-distance communication in the body?

Communication that involves hormones which travel through the bloodstream to affect distant target cells.

What are the two main types of hormones?

Water-soluble peptide hormones and steroid hormones.

How do peptide hormones function?

They bind to receptors on the cell membrane and act quickly.

What is the mechanism of action for steroid hormones?

They often bind to cytosolic or nuclear receptors and tend to act more slowly, influencing gene expression.

What is the role of epinephrine in the body?

It binds to different receptors causing various responses, such as constriction in intestinal blood vessels and dilation in skeletal blood vessels.

What are neurohormones?

Substances released by neurons into the bloodstream that reach target cells, such as vasopressin and oxytocin.

What is signal transduction?

The process by which an external signal is transmitted across the cell membrane, often involving transmembrane proteins.

How do ion channels relate to cell signaling?

Ion channels can be opened or closed by extracellular signals, affecting cellular responses like muscle contractions.

What is the role of vasopressin in the kidney?

It increases water absorption into the bloodstream, thereby raising blood pressure.

What is the significance of the fed state in blood sugar regulation?

In the fed state, glucose levels rise, triggering insulin release to promote glucose uptake by cells.

What happens in the fasting state regarding blood glucose?

Glucagon is released to stimulate the liver to convert glycogen into glucose, raising blood sugar levels.

What is the relationship between insulin and glucagon?

They are antagonistic hormones that work together to maintain blood glucose homeostasis.

What triggers the release of insulin from beta cells?

Increased extracellular glucose levels lead to ATP production, closing potassium channels and causing depolarization.

What is GLP-1 and its role in insulin regulation?

GLP-1 is a hormone released by the digestive system that enhances insulin secretion and promotes satiety.

How does insulin promote blood glucose uptake?

Insulin signals cells to absorb glucose from the bloodstream, facilitating its use for energy.

What effect do amino acids have on beta cells?

Amino acids can also cause depolarization of beta cells, leading to insulin release.

What is the role of feed-forward mechanisms in insulin production?

They prepare the body for increased insulin secretion in anticipation of rising glucose levels after meals.

What is the function of stretch receptors in the heart?

They detect changes in blood pressure and transmit signals to the brain for regulation.

What is the significance of mechanical signals in cell communication?

Mechanical signals can directly open or close ion channels, influencing cellular responses.

What do insulin receptors do?

They promote glucose transporters to move to the plasma membrane but do not activate them.

What is a major consequence of diabetes?

Sugar cannot move into the cells, leading to cell death.

How does exercise help with Type 2 Diabetes?

It promotes the insertion of glucose transporters (GLUT4) into membranes without needing glucose.

What happens in the liver without insulin?

The liver breaks down glycogen into glucose and releases it through GLUT2 transporters.

What is the effect of the insulin signal on glucose?

It reverses the direction and brings glucose into the cells.

What does insulin do to free glucose?

It phosphorylates free glucose, preventing it from leaving the cell.

What causes Type 1 diabetes?

It results from the autoimmune destruction of beta cells.

What causes Type 2 diabetes?

It is caused by insulin insufficiency and/or insulin resistance.

What are muscle cells primarily made of?

Myofibrils, which contain filaments.

What initiates muscle cell depolarization?

A neuron releases acetylcholine.

What is released from the sarcoplasmic reticulum during an action potential?

Calcium ions.

What are the two types of filaments in muscle cells?

Myosin (thick filaments) and actin (thin filaments).

What is the role of myosin in muscle contraction?

Myosin walks and pulls on actin fibers, causing the sarcomere to shorten.

What blocks myosin from binding to actin when the muscle is relaxed?

Tropomyosin covers the myosin binding sites.

What happens when calcium binds to troponin?

It causes tropomyosin to move away from the myosin binding sites.

What is the sliding filament mechanism?

Myosin heads walk along actin filaments, pulling them towards the center of the sarcomere.

What is the rigor state in muscle contraction?

It occurs when myosin heads are stuck to actin before ATP binds.

What are the three types of muscle contractions?

Concentric, isometric, and eccentric contractions.

What characterizes Type 1 muscle fibers?

They are slow-twitch, oxidative fibers packed with mitochondria and myoglobin.

What characterizes Type 2 muscle fibers?

They are fast-twitch, glycolytic fibers that fatigue easily and have less myoglobin.

How is force controlled in muscles?

By contracting some motor units while others remain inactive.

What is the difference between single-unit and multi-unit smooth muscle?

Single-unit is controlled by one neuron, while multi-unit has individual motor units not electrically linked.

What is the role of calcium in smooth muscle contraction?

Calcium has a slower signal transduction pathway, leading to slower contractions.

What happens to calcium levels during an action potential in muscle cells?

Calcium is released from the sarcoplasmic reticulum.

What is the role of CTSB in exercise?

CTSB levels increase during exercise and are related to spatial memory.

What happens to sodium and potassium during neuronal action potentials?

Sodium rushes in while potassium rushes out, creating a current.

What must happen for a neuron to fire?

There must be enough voltage change to generate sufficient current in the trigger zone.

What is the role of excitatory and inhibitory signals in neuron firing?

They can add together to prevent the neuron from firing.

What happens to unused synapses after birth?

Unused synapses are pruned out.

What is axon propagation?

The process where current travels down the axon, facilitated by sodium channels that open sequentially.

How do novacaine and lidocaine affect sodium channels?

They block specific sodium channels involved in the pain response.

What are the two gates of a sodium channel?

An activation gate and an inactivation gate.

What occurs when a cell depolarizes due to a stimulus?

The activation gate of the sodium channel opens, allowing sodium to rush in.

What is the absolute refractory period?

A period after an action potential during which inactivation gates are closed, preventing further action potentials.

What is the relative refractory period?

A period where sodium channels reset, but potassium channels are still open, requiring a stronger stimulus to fire.

How does myelin affect signal transmission?

It insulates the axon, reduces current leak, and allows signals to move faster by 'hopping' between sodium channels.

What is hyperkalemia?

A condition with excess potassium in the extracellular compartment, making it easier for neurons to fire.

What is hypokalemia?

A condition with low potassium, making it harder for neurons to reach the firing threshold.

How do electrical signals trigger neurotransmitter release?

They open voltage-gated calcium channels, leading to exocytosis of neurotransmitter vesicles.

What terminates neurotransmitter signals in the synaptic cleft?

Reuptake, degradation, and diffusion.

How does cocaine affect neurotransmitter levels?

It increases the amount of dopamine released into the synaptic cleft.

What is temporal summation?

When two stimuli occur close together in time, allowing them to sum and potentially trigger a neuron to fire.

What is spatial summation?

The strength of a signal depends on the distance from the cell body; closer signals have a greater effect.

What is the significance of synaptic connections in learning?

Learning changes the strength and number of synaptic connections in the brain.

What is a mutation in the context of sodium channels?

A single codon change that alters the amino acid sequence, affecting channel function.