Evolutionary biologists believe that the "fight or flight" response was crucial for the survival of many species throughout Geologic Time.
Both the sympathetic and parasympathetic nervous systems are vital to our health and survival.
The neural system of all animals is composed of highly specialised cells called neurons which can detect, receive and transmit different kinds of stimuli.
When the "fight or flight" response has been activated of the autonomic nervous system called the sympathetic division controls this response.
What is human nervous system?
The human nervous system is divided into two parts,
1. The Central Neural System(CNS)
2. The Peripheral Neural System(PNS)
The CNS includes the brain and the spinal cord and is the site of
information processing and control.
The PNS comprises of all the nerves of the body associated with the CNS i.e., brain and spinal cord.
The nerve fibres of the PNS are of two types :
1. Afferent fibres
2. Efferent fibres
The PNS is divided into two divisions called;
a. Somatic neural system
b. Autonomic neural system
The somatic neural system relays impulses from the CNS to skeletal muscles while the autonomic neural system transmits impulses from the CNS to the involuntary organs and smooth muscles of the body. The autonomic neural system is further classified as;
First nucleus in pollen grain divide to form generative nucleus and tube nucleus. the generative nucleus divide to form two sperm nuclei, while tube nucleus help in the development of pollen tube.
Allosteric activators bind to locations on an enzyme away from the active site, inducing a conformational change that increases the affinity of the enzyme's active site(s) for its substrate(s). Allosteric inhibitors modify the enzyme's active site so that substrate binding is reduced or prevented.
