Is sympathetic activity considered a feedforward mechanism??
961315
Hormonal activity is usually a negative feed back mechanism. You would think exercise would feed forward, though, as the rate would keep increasing. Not my area, though, so a functional biologist is needed here.
351086
I kind of had a hard time understanding the last part of the question, but I tried to answer anyway.\n\nThe Sympathetic Nervous System (SNS) is also called the "fight or flight" system. It helps the body cope with emergency situations where it might have to defend itself (fight) or escape (flight). It causes increased heart rate, bronchodilation (your airways to get smaller), shaking, dry mouth, and blood to go to the skeletal muscle (muscle we use voluntarily).\n\nAs for the gastrointestinal tract, it will slow or completely stop digestion and defecation (pooping). Like I said before, you have an increased heart rate, and most of the blood goes to your skeletal muscle (the SNS is getting the body ready to fight or run). This is why people look pale; a majority of the blood has gone away from their skin into the muscles. Since most of the blood is in the muscles, and the SNS almost stops the GI tract, there is very little blood flow to the gastrointestinal tract when your sympathetic nervous system is heightened. Normal blood flow is resumed when you are calmed down.\n\nI hope this helps!
375099
Spinal\n\n\n\nErection is basically a spinal reflex that can be initiated by recruitment of penile afferents, but also by visual, olfactory, and imaginary stimuli. The reflex involves both autonomic and somatic efferents and is modulated by supraspinal influences. Several central transmitters involved in the erectile control have been identified. Dopamine, acetylcholine, nitric oxide (NO), and peptides, such as oxytocin and adrenocorticotropic/alpha-melanocyte-stimulating hormone, seem to have a facilitatory role, whereas serotonin may be either facilitatory or inhibitory, and enkephalins are inhibitory.
643712
I. COMPARISON OF SOMATIC AND AUTONOMIC NERVOUS SYSTEMS (ANS)\n\n     A. Sensory neurons of the somatic nervous system receive input from the special senses, general somatic senses, and proprioceptors; sensory neurons of the ANS receive input from the special senses, general visceral senses, and general somatic senses.\n\n     B. The somatic nervous system operates under conscious control; the ANS operates without conscious control.\n    \n     C. The axons of the motor neurons of the somatic nervous system extend from the CNS synapse directly to an effector and release acetylcholine, whereas autonomic pathways consist of two sets of motor (efferent) neurons.\n\n        1. The axon of the first (preganglionic) motor neuron of the ANS extends from the CNS and synapses in a ganglion with the second neuron.\n        2. The second (postganglionic) motor neuron synapses on an effector. Preganglionic fibers release the neurotransmitter acetylcholine and postganglionic fibers release acetylcholine or norepinephrine. \n\n     D. Somatic nervous system effectors are skeletal muscles, and ANS effectors include cardiac and smooth muscle, and glands.\n    \n     E. The somatic nervous system responds to neurotransmitters as excitation while the ANS response to neurotransmitters is excitation or inhibition.\n\n     F. A summary of the similarities of and differences between the somatic and autonomic nervous systems is presented.\n\n     G. The output (efferent) part of the ANS is divided into two principal parts: the sympathetic and the parasympathetic. Organs that receive impulses from both sympathetic and parasympathetic fibers are said to have dual innervation. III. \n\nANATOMY OF AUTONOMIC MOTOR PATHWAYS\n\n     A. Overview\n\n        1. Preganglionic neurons are myelinated; postganglionic neurons are unmyelinated.\n         2. The first of two autonomic motor neurons is called a preganglionic neuron.\n             a. Its cell body is in the brain or spinal cord.\n             b. Its myelinated axon, called a preganglionic fiber pathway, passes out of the CNS as part of a cranial or spinal nerve, later separating from the nerve and extending to an autonomic ganglion where it synapses with the postganglionic neuron.\n        3. The postganglionic neuron pathway, the second neuron in the autonomic motor circuit, lies entirely outside the CNS.\n            a. Its cell body and dendrites are located in an autonomic ganglion, where it makes synapses with one or more preganglionic fibers.\n            b. The axon of a postganglionic neuron, the postganglionic fiber, is unmyelinated and terminates in a visceral effector. \n         4. The cell bodies of sympathetic preganglionic neurons are in the lateral gray homs of the 12 thoracic and first 2 or 3 lumbar segments; the cell bodies of parasympathetic preganglionic neurons are in cranial nerve nuclei (III, VII, IX, and X) in the brain stem and lateral gray horns of the second through fourth sacral segments of the cord.\n         5. Autonomic ganglia are classified as:\n              a. sympathetic trunk (vertebral chain) ganglia (on both sides of spinal column)\n              b. prevertebral (collateral) ganglia (anterior to spinal column);\n              c. parasympathetic terminal (intramural) ganglia (near or inside visceral effectors). 6. In addition to autonomic ganglia, the ANS contains autonomic plexuses. \n\n     B. Sympathetic and Parasympathetic Divisions\n\n         1. Sympathetic preganglionic neurons synapses with postganglionic neurons in ganglia of the sympathetic trunk or prevertebral ganglia.\n         2. Parasympathetic preganglionic neurons synapses with postganglionic neurons in terminal ganglia.\n        3. The salient anatomical features of the sympathetic and parasympathetic divisions are compared. \n\nTransmission of Autonomic Stimuli\n\nLike other nerves, those of the autonomic nervous system convey their messages to the appropriate end organs (blood vessels, viscera,
723247
There are specific neurons specialized for cold sensations- under hot water, there is ectopic activation of these neurons from the physical effects of heat on the synaptic membranes- These are then communicated through the spinal cord and mis-interpreted.
232618
I have never heard of that feedback mechanism and I am not sure it makes logical sense.  I can see where someone might suppose it though - our sexual drive is temporarily satisfied; testosterone is responsible in both sexes for sex drive.  But no, hormone levels do not decrease.  \n\nI do know that after orgasm oxytocin is secreted which actually promotes our interest in being close and cuddling...in some cases, snooze.  \n\nOur bodies are amazing!
1095854
Yeah, increases heart rate, pulse, blood pressure. Not a reason to start, though.
1115590
Your heart has signals that travel to it telling it when to beat.  The things that signal are called nerves, which you probably know, but I am going to explain how I look at it.  The nerves have high  sodium (Na+) on the outside (making it positive).  On the inside of the nerve axon, there are high levels of potassium (K+) (making it negative).  The "inside" and "outside" are seperated by a membrane which has gates and channels that allow the K+ to move out and the Na+ to move in.  When the "charge" changes enough in the axon of the nerve, you get a signal sent "down the line".   If you are low in K+, the signals can't work right because enough K+ doesn't move in/Na+ doesn't move out to cause a signal or signals at the wrong time.  Your heart gets out of sync and things get all messed up, arrhythmias and such.
804419
My best knowledge would be excitment, which gives a boost of adrenaline, causing the heart to have to pump harder due to the adrenaline rush, causing it to sometimes skip a beat.
405596
I know that sympathetic nerves innervate what juxtaglomerular cells that are part of the renal blood vessels.  These cells release renin in response to sympathetic stimulation.  This question is a little particular.  Because the juxtaglomerular "apparatus" includes both the vessels and the thick ascending limb of Henle. I would choose A if it was on my test, but if I could make a second guess I could say E.
603832
Sex is very strange physiologically.  It is the only activity I know of that involves BOTH sympathetic and parasympathetic nervous stimulation.  Of course, your question was about endocrinology, so that doesn't help you much.  The sex hormones are most definatley involved (testosterone, progesterone, estrogen, luteinizing hormone, and follicle stimulating hormone).  This is really an interesting question.  I hope someone can give a more specific answer.
765525
no, this is too low of a stimulus or intake if it was to be a cause, you could talk to the doctor for possible causes of the exact heart beat problem, good luck
320947
The adrenal medulla secretes adrenalin and noradrenalin.\nUnlike the cortex it is derived from neural crest cells, but unlike a previous answer they are NOT neurons: believe me I look at them every week!\nIt is the 'fear, flight, fright' hormone and is essential: responsible for butterflies in the stomach and more postive reactions to stress. It elevates the blood pressure.\nTumours of the medulla are called Phaeochromocytomas. They are rare, 10% are malignant and they cause flushing and high blood pressure and are dangerous unless removed by a skilled surgeon.\nHope that helps!
182252
I believe the answer about the heart being independent is incorrect. The heart is controlled by the autonomic nervous system, which is not consciously controlled. This same system also makes you stomach digest food among other things. Adrenaline (a hormone released by the pituitary gland in the brain) makes the heart beat faster at times and noradrenaline relxes it. When the heart is taken out of the body, neurons are still firing within the heart, but without the central nervous system, it will cease to beat.
608590
Generally, caffeine will stimulate the Sympathetic Nervous System, thus raising the heart rate
1023363
Phentermine, as many other prescription drugs, works with neurotransmitters in the brain. It is a centrally-acting stimulant chemically related to the amphetamines. It stimulates neuron bundles to release a particular group of neurotransmitters known as catecholamines; these include dopamine, epinephrine (also known as adrenalin), and norepinephrine (noradrenaline). The anorectic activity seen with these compounds would thus seem likely due to this effect on Central Nervous System, which is consistent with current knowledge about Central Nervous System systems and feeding behavior. This is the same mechanism of action as other stimulant appetite suppresants such as diethylpropion, and phendimetrazine.\n\nThe neurotransmitters signal a fight-or-flight response in the body which, in turn, puts a halt to the hunger signal. As a result, it causes a loss in appetite because the brain does not receive the hunger message.
71569
I agree with earlthek and babydoll. Electrical synapses in the body that affects the polar imbalance.