Nonspecific immune response include skin, mucus and lysozyme’s. B and T cells are used in specific immune responses. T cell receptors and antibodies produced by B cells bind to specific antigens. Each T cell and B cell is for a specific antigen. As T cells mature a mechanism deletes those carrying receptors that would act as self-antigens. T cells secrete interleukin-2 and stimulates the activity of natural killer cells, cytotoxic T cells and B cells... The invading pathogen is to be destroyed or neutralized. Antibodies work to stop and destroy pathogens once they have entered the body. B cells can produce antibodies but need exposure to foreign antigens to do so.
There are four lobes of the brain, the frontal, temporal, occipital, and parietal. They all have different functions, the frontal lobe deals with speech and motor control. The temporal lobe deals with taste, face recognition and hearing. The occipital lobe deals with vision. The parietal lobe deals with body awareness. Motor neurons receive signals from the brain and spinal cord, if the signal is interrupted or messed up, motor skills would be ruined.
A synapse is a small gap that allows neurons to communicate. Neurons can communicate with electrical signals or with neurotransmitters. Neurotransmitters chemical signaling molecules.The neuron sending the information is the presynaptic neuron while the neuron receiving the information is the postsynaptic neuron. In the chemical synapse the neurotransmitter is released from a presynaptic cell bind to receptors of postsynaptic cell and changes will occur in the postsynaptic cell. Pre and postsynaptic cells join through gap junctions. Synapses between motor neurons and muscle cells are excitatory. The motor end plates respond to ACh with greater positive charge. Synapses between neurons can be inhibitory and cause hyper-polarization.
Neurons are nerve cells, these cells are important and have different parts on them that have different functions. Dendrites are on the end of the neuron, they receive information from other neurons. The nucleus and most cell organelles are in the cell body. The axon hillock uses information that was collected by the dendrites. The axon conducts action potentials away from the cell body. Axon terminals are at the other end of the neuron and synapses with a target cell. The sodium potassium pump of neurons pumps Sodium and Potassium into the cell, and Hydrogen is pumped out of the cell through an antiport. Myelin sheaths are made of Schwann cells. Schwann cells produce layers of myelin. There are gaps called Nodes of River that separates the Schwann cells. Action potentials travel by jumping from node to node. Electron potentials polarizes the neuron membranes.
A signal transduction pathway is a sequence of molecular events and chemical reactions that lead to a cell’’s response to a signal. First a signaling molecule arrives at the target cell, and activates a specific protein on the cell membrane. Then a signal molecule binds to a receptor protein in the cell surface or in the cytoplasm. After that, the signal binding changes the shape of the receptor and the active site is exposed. Then finally the activated receptor activates a signal transduction pathway to bring cellular changes. Short term responses include enzyme activation and cell movement. Long term responses include altered DNA transcription. Signaling at the plasma membrane usually causes many events in the cell and proteins interact with other proteins until the final response happens. The many different events can cause a signal to be amplified and cause different response in the target cell. Second messengers regulate target enzymes and bind to them noncovalently. Some small molecules have to be transmitted through second messengers. Second messengers can be used to amplify a signal.
Endocrine signals can be given at a small area or wide area. Cells can secrete substances in endocrine secretion or a body cavity that can send signals to the outside world. Exocrine secretion happens in the external world, while endocrine secretion happens inside the body. Through endocrine signals, cells are able to communicate at long or short distances. Hormones are long distance endocrine signals. They are released into the bloodstream and travel through the whole body. There are different types of hormones such as steroid hormones (do not dissolve well in blood plasma), amine hormones (small molecules) and peptide and proteins hormones (Large molecule, easily transported in the blood). They all perform different functions but they all are long distant signals that can travel throughout the body. Endocrine cells of the anterior pituitary are under negative feedback control. The hormones of the target glands they stimulate are the reason they have negative feedback. The hormone CRH, is released by the hypothalamus it releases the ACTH from the anterior pituitary, which stimulates the release of the cortisone hormone... Once it's released in the body it inhibits further release of CRH and ACTH, which helps to maintain homeostasis.