Which of the following chemicals is released by one type of immune cell to directly activate another type of immune cell?

The approximate threshold value for mammalian neurons is -55mV.

One of the ways that cells regulate their water balance is by adjusting to different solute concentrations in their environment. When a cell is placed in a solution that has a higher concentration of solutes than the cell itself, the solution is called hypertonic. In this case, water will tend to move out of the cell through special channels called aquaporins, which are embedded in the plasma membrane. This movement of water across a selectively permeable membrane is a type of passive transport called osmosis. Osmosis does not require any energy input from the cell, unlike other forms of transport such as diffusion, facilitated diffusion, or active transport.

When a muscle cell is stimulated by a nerve impulse, calcium ions are released from the sarcoplasmic reticulum into the cytoplasm. The calcium ions bind to the troponin complex, which is a protein that regulates the interaction between actin and myosin filaments. The binding of calcium to troponin causes a conformational change that exposes the binding sites for myosin on the actin filaments. This allows the myosin heads to attach to the actin and pull the filaments past each other, resulting in muscle contraction.

Osteoporosis is a condition that affects the bones, making them weak and brittle. It occurs when the balance between bone formation and bone resorption is disrupted. Bone formation is carried out by cells called osteoblasts, while bone resorption is done by cells called osteoclasts. Osteocytes are mature bone cells that maintain the bone matrix. Osteoporosis results from a decline in osteoblast activity while osteoclast activity continues at expected levels, leading to more bone loss than bone gain. This reduces the bone density and increases the risk of fractures.

Terminal velocity is the maximum speed achieved by an object freely falling through a gas or liquid. At terminal velocity, the forces acting on the object are balanced so it is no longer accelerating. Terminal velocity is achieved when the force of gravity is equal to air resistance. From the data table you provided, we can see that as the mass of the coffee filters increases, so does the terminal velocity. This means that heavier objects fall faster than lighter objects. Therefore, conclusion D is supported by the data in the table.

A tsunami is a series of large waves that are caused by the displacement of a large volume of water in the ocean or a large lake. The most common cause of tsunamis is earthquakes, which can generate seismic waves that travel through the water and create sudden changes in water level.

The pleura is a thin membrane that surrounds the lungs and lines the chest cavity. It protects the lungs from friction and infection, and helps them expand and contract during breathing. The other organs listed are not covered by the pleura, but by other types of connective tissue sheaths, such as the pericardium for the heart, the peritoneum for the spleen and liver, and the mesentery for the intestines.

The number of protons in an atom is equal to its atomic number. In this case, lithium has an atomic number of 3, so it contains 3 protons.

The other choices (A, C, and D) do not represent the correct number of protons for a lithium atom.

Antidiuretic hormone (ADH) is a peptide hormone that regulates the water balance in the body by increasing the reabsorption of water by the kidneys. ADH is synthesized by the hypothalamus, a part of the brain that controls many functions, such as appetite, sleep, and body temperature. ADH is then stored and released by the posterior pituitary gland, which is located at the base of the brain.

The process in which an ovarian follicle matures and releases a reproductive egg is called ovulation. Ovulation is one of the phases of the menstrual cycle, which also includes follicular phase, luteal phase and menstruation