Stimuli/Senses
The Nervous System
The nervous system is the reason living organisms can feel and tell their muscles to move. It is made up of three parts, the central nervous system(brain and spinal cord), Peripheral nervous system(all neurons) and the five sense organs. These parts work together to act on internal and external stimuluses.
Neurons
Neurons are the specialised cells in which the electric and chemical impulses travel through the organism to allow it to react and move. Neurons are made up of a cell body containing a nucleus at the centre as well as a dendron and axon connecting it on either sides to the dendrites at the ends.
There are three types of nerves; sensory, motor and relay. All these neurons are made up of the same parts but slightly differ in size in some places for the job they are doing. Relay neurons are the same size the on both sides but sensory neurons have long dendrons to allow to take in the message and motor neurons have short dendrons so that it can send the message to the muscle or gland quickly.
Stimulus
Internal-
Internal stimuluses is a stimulus that originates from inside the organism causing action to need to take place. This can be seen when an animal is dehydrated and the sensory neurons send a message to the brain that it is thirsty. In response the body tells the muscles to search for liquid to drink. Another example is when the in internal temperature of the body changes causing headaches.
External-
External stimuluses can be any number or various objects in the environment that the five senses detect. In a red fox it might smell the scent of prey or see it it nearby, the nose connects with the sensory neuron and this sends it to the relay neuron through synapsis between the dendrites. In the relay neuron it travels to the brain and out after deciding that it needs to send a message to all four of it's limbs to pounce upon the prey. This message is sent through the motor neurons that connect to the muscles associated with this movement. This process will be repeated until the fox does not need to do it anymore. There is also a second way in which a movement can be created by bypassing the brain and is called a reflex arc. This works by sending the message to the spine instead and because the fox has already done it before it doesn't to think and so it is a reflex. An example of this in a fox is when it is chewing on it's previously caught prey, the jaw moves in a repeat action where nothing changes unless of course it finds something unusual.
Internal stimuluses is a stimulus that originates from inside the organism causing action to need to take place. This can be seen when an animal is dehydrated and the sensory neurons send a message to the brain that it is thirsty. In response the body tells the muscles to search for liquid to drink. Another example is when the in internal temperature of the body changes causing headaches.
External-
External stimuluses can be any number or various objects in the environment that the five senses detect. In a red fox it might smell the scent of prey or see it it nearby, the nose connects with the sensory neuron and this sends it to the relay neuron through synapsis between the dendrites. In the relay neuron it travels to the brain and out after deciding that it needs to send a message to all four of it's limbs to pounce upon the prey. This message is sent through the motor neurons that connect to the muscles associated with this movement. This process will be repeated until the fox does not need to do it anymore. There is also a second way in which a movement can be created by bypassing the brain and is called a reflex arc. This works by sending the message to the spine instead and because the fox has already done it before it doesn't to think and so it is a reflex. An example of this in a fox is when it is chewing on it's previously caught prey, the jaw moves in a repeat action where nothing changes unless of course it finds something unusual.
Synapsis
Secretion
Secretion is the reaction to either an internal or external stimulus through the glands or organs. Many humans see it in effect in everyday life through sweat. It is used to cool the body and expel water. Another things secreted is hormones throughout animals bodies for instance when the fox sees it prey, adrenaline is released to the muscle that enable it to pounce on it's food.