Nervous and Endocrine by James Myers https://padlet.com/jameschmyers/1r3euzy47qf6 en-us 2018-05-08 08:16:55 UTC 2018-06-12 15:16:47 UTC hello@padlet.com jameschmyers https://padlet.com/jameschmyers/1r3euzy47qf6/wish/258815148
The nervous system is the part of an animal that coordinates its actions by transmitting signals to and from different parts of its body. The nervous system detects environmental changes that impact the body and then works in tandem with the endocrine system to respond to such events. In vertebrates it consists of two main parts; the central nervous system and the peripheral nervous system. The CNS consists of the brain and spinal cord. The PNS consists mainly of nerves, which are enclosed bundles of the long fibers or axons that connect the CNS to every other part of the body. Nerves that transmit signals from the brain are called motor or efferent nerves, while those nerves that transmit information from the body to the CNS are called sensory. Spinal nerves serve both functions and are called mixed nerves.

Action potential depends on positive ions continually traveling away from the cell body, and that is much easier in a larger axon. A smaller axon, like the ones found in nerves that conduct pain, would make it much harder for ions to move down the cell because they would keep bumping into other molecules increasing the resistance and making pain one of the slowest feelings to feel.

]]> 2018-05-08 08:19:04 UTC https://padlet.com/jameschmyers/1r3euzy47qf6/wish/258815148 jameschmyers https://padlet.com/jameschmyers/1r3euzy47qf6/wish/265628141 The PNS is divided into three separate subsystems, the somatic, autonomic, and enteric nervous systems. Somatic nerves mediate voluntary movement. The autonomic nervous system is further subdivided into the sympathetic and the parasympathetic nervous systems. The sympathetic nervous system is activated in cases of emergencies to mobilize energy, while the parasympathetic nervous system is activated when organisms are in a relaxed state. The enteric nervous system functions to control the gastrointestinal system. Both autonomic and enteric nervous systems function involuntarily. Nerves that exit from the cranium are called cranial nerves while those exiting from the spinal cord are called spinal nerves]]> 2018-06-05 13:00:05 UTC https://padlet.com/jameschmyers/1r3euzy47qf6/wish/265628141 jameschmyers https://padlet.com/jameschmyers/1r3euzy47qf6/wish/265628234 At the cellular level, the nervous system is defined by the presence of a special type of cell, called the neuron, also known as a nerve cell. Neurons have special structures that allow them to send signals rapidly and precisely to other cells. They send these signals in the form of electrochemical waves traveling along thin fibres called axons, which cause chemicals called neurotransmitters to be released at junctions called synapses. A cell that receives a synaptic signal from a neuron may be excited, inhibited, or otherwise modulated. The connections between neurons can form neural circuits and also neural networks that generate an organism's perception of the world and determine its behaviour. Along with neurons, the nervous system contains other specialized cells called glial cells, which provide structural and metabolic support.]]> 2018-06-05 13:00:26 UTC https://padlet.com/jameschmyers/1r3euzy47qf6/wish/265628234 jameschmyers https://padlet.com/jameschmyers/1r3euzy47qf6/wish/265628334 The endocrine system is a chemical messenger system consisting of hormones. It consists of grouped glands in an organism that carries hormones directly into the circulatory system to be carried towards major organs. In humans the major endocrine gland is thyroid gland which secretes hormones to regulate the metabolism. In vertebrates, the hypothalamus is the neural control centre for all endocrine systems.
Special features of endocrine glands are their ductless nature or granules that store their hormones. In contrast, exocrine glands, such as salivary glands, sweat glands, and glands within the gastrointestinal tract, tend to be much less vascular and have ducts or a hollow lumen. 

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A number of glands that signal each other in sequence are usually referred to as an axis, for example, the hypothalamic pituitary adrenal axis.

In addition to the specialized endocrine organs mentioned above, many other organs that are part of other body systems, such as bone, kidney, liver, heart and gonads, have secondary endocrine functions. For example, the kidney secretes endocrine hormones such as erythropoietin and renin.


The endocrine system is regulated by feedback in much the same way that a thermostat regulates the temperature in a room. For the hormones that are regulated by the pituitary gland, a signal is sent from the hypothalamus to the pituitary gland in the form of a releasing hormone, which stimulates the pituitary to secrete a stimulating hormone into the circulation. The stimulating hormone then signals the target gland to secrete its hormone. As the level of this hormone rises in the circulation, the hypothalamus and the pituitary gland shut down secretion of the releasing hormone and the stimulating hormone, which in turn slows the secretion by the target gland. This system results in stable blood concentrations of the hormones that are regulated by the pituitary gland.
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