Autonomic Nervous system

positive feedback loop

A positive feedback loop is a system where one variable increases the quality of another variable which in turn increases the quantity/occurrence of the first variable. Positive feedback loops are processes which occur within feedback loops in general, and their conceptual opposite is a negative feedback loop.

body cavities

Humans have four body cavities: (1) the dorsal body cavity that encloses the brain and spinal cord; (2) the thoracic cavity that encloses the heart and lungs; (3) the abdominal cavity that encloses most of the digestive organs and kidneys; and (4) the pelvic cavity that encloses the bladder and reproductive organs.

negative feedback loop

Negative feedback loops play an important role in how many of the systems of the human body stay in control. A negative feedback loop is a type of self-regulating system. In a negative feedback loop, increased output from the system inhibits future production by the system. In other words, the system controls how much product it makes by shutting down manufacturing when levels of output or the amount of accumulated product gets too high.

neurotransmitter

Neurotransmitters are often referred to as the body's chemical messengers. They are the molecules used by the nervous system to transmit messages between neurons, or from neurons to muscles. Communication between two neurons happens in the synaptic cleft (the small gap between the synapses of neurons). Here, electrical signals that have travelled along the axon are briefly converted into chemical ones through the release of neurotransmitters, causing a specific response in the receiving neuron. A neurotransmitter influences a neuron in one of three ways: excitatory, inhibitory or modulatory.

autono,ic nervous system

The autonomic nervous system (ANS) controls the activities of organs, glands, and various involuntary muscles, such as cardiac and smooth muscles.

Autonomic Nervous System

The autonomic nervous system controls the insides of the body: the viscera or gut. It carries information about the inside of the body to the CNS and controls the action of internal organs, including the gut, the heart, the secretion of epinephrine (adrenalin) and norepinephrine (noradrenalin) from the medulla (middle part) of the adrenal gland, etc. The autonomic nervous system plays an essential role in keeping the body's internal environment (temperature, salt concentration, blood sugar, oxygen and carbon dioxide level in blood, etc) in proper balance, a condition called homeostasis. The autonomic nervous system also plays a major part in emotional experience and expression. When you are emotionally excited, the body shows many changes: blood pressure and heart beat increase, mouth is often dry, stomach has "butterflies" in it. These and other body actions are controlled by the autonomic nervous system.

Neurotransmitters of the A.N.S.

The most common are norepinephrine (NE) and acetylcholine (Ach). All presynaptic neurons use Ach as a neurotransmitter. Ach is also released by some sympathetic postsynaptic neurons and all parasympathetic postsynaptic neurons.

Parasympathetic Nervous System

The parasympathetic division, shown at the right, is the "housekeeping" division. It acts to replace and recover from the activities of living. Its action is (almost always) the opposite of the sympathetic division. It activates the gut for digestion, slows the heart rate, decreases the blood pressure, etc.

sagital

The sagittal plane is an anatomical boundary that exists between the left and right sides of the body. The sagittal planes runs parallel to the longitudinal axis of the organism, or from the mouth to the tail.

Sympathetic Nervous System

The sympathetic division, shown at the left, is the emergency system. It prepares the body to put out energy and to protect it from effects of injury. It shuts the gut down, speeds up the heart, increases blood pressure, dilates (makes bigger) the pupils of the eyes, makes more glucose (blood sugar) available in the blood for energy, etc. Cannon described these reactions as preparation for fight or flight (running away).

gross anatomy

the branch of anatomy that deals with the structure of organs and tissues that are visible to the naked eye.

ventral

underside