Body reactivity
From Wikipedia, the free encyclopedia
Body reactivity is usually understood as an organism's functional ability of its body to react adequately in response to influence the environment. It is not to be confused with resistance, which is its physiological stability against the influence of pathogenic factors. The body reactivity can range from homeostasis to a fight or flight response. Ultimately, they are all governed by the nervous system.
Central nervous system
The central nervous system (CNS) consists of parts that are encased by the bones of the skull and spinal column: the brain and spinal cord. The peripheral nervous system (PNS) is found outside those bones and consists of the nerves and most of the sensory organs.[1]
The CNS can be divided into the brain and spinal cord. The CNS processes many different kinds of incoming sensory information. It is also the source of thoughts, emotions, and memories. Most signals that stimulate muscles to contract and glands to secrete originate in the CNS. The spinal cord and spinal nerves contribute to homeostasis by providing quick reflexive responses to many stimuli. The spinal cord is the pathway for sensory input to the brain and motor output from the brain.[2] The brain is responsible for integrating most sensory information and coordinating body function, both consciously and unconsciously.[3]
Peripheral nervous system
The PNS can be divided into the autonomic and somatic nervous system. The autonomic nervous system can be divided into the parasympathetic, sympathetic, and enteric nervous system. The sympathetic nervous system regulates the "fight or flight" responses. The parasympathetic nervous system regulates the "rest and digest" responses. The enteric nervous system innervates the viscera (gastrointestinal tract, pancreas, and gall bladder). The somatic nervous system consists of peripheral nerve fibers that send sensory information to the central nervous system and motor nerve fibers that project to skeletal muscle. The somatic nervous system engages in voluntary reactions, and the autonomic nervous system engages in involuntary reactions.[4]
| Structure[5] | Sympathetic Stimulation[5] | Parasympathetic Stimulation[5] |
|---|---|---|
| Iris (Eye Muscle) | Pupil Dilation | Pupil Constriction |
| Salivary Glands | Saliva Production Reduces | Saliva Production Increases |
| Oral/ Nasal Mucosa | Mucus Production Reduced | Mucus Production Increases |
| Heart | Heart Rate and Force Increased | Heart Rate and Force Decreased |
| Lung | Bronchial Muscle Relaxed | Bronchial Muscle Contracted |
| Stomach | Peristalsis Reduced | Gastric Juice Secreted, Motility Increased |
| Small Intestine | Motility Reduced | Digestion Increased |
| Large Intestine | Motility Reduced | Secretion and Motility Increased |
| Liver | Increased Conversion of Glycogen to Glucose | |
| Kidney | Decreased Urine Secretion | Increased Urine Secretion |
| Adrenal Medulla | Norepinephrine and Epinephrine Secreted | |
| Bladder | Wall Relaxed, Sphincter Closed | Wall Contracted, Sphincter Relaxed |
