The nervous system and animal behaviour

Nervous system:

The nervous system is a complex network of nerves and cells (neurons) that carry messages to and from the brain and spinal cord to various parts of the body. It controls and coordinates all essential functions of the body, including voluntary actions (like moving muscles) and involuntary actions (like breathing).

Nervous system and animal behavior:

The nervous system relies on electrical impulses. It causes quicker responses including behavioral responses. This field of work is called Neuroethology.

Neuron:

Animals possess specialized nerve cells called neurons. Neurons have a similar structure.

1.    Neuron:

Each neuron has a cell body. This cell body contains a nucleus and one or more nerve fibers. These nerve fibers are called axons.

2.    Axons:

1.Transmit electrical information from one cell to another. Axons can range in size from less than a millimeter to over a meter long. Axons also differ in diameter. This variation is important. The speed of the nervous impulse affect the speed at which animal respond behaviorally. Thicker the diameter of an axon  the faster the nerve impulses travel along it. Each neuron has only a single axon. The first section is called as the axon hillock. Its last section consist of Axon terminals (Sometimes called Synaptic terminal).

2.There may be many branches of Axon terminal from these branches information leaves a neuron as it passes along the nervous system.

3.Neurons receive impulses from another cell Via fibers called dendrites. a neuron may have thousands of dendrites. They form a dendritic tree. each branch on this dendritic tree may  have many dendritic spines. These spines receives input from other neurons.

Read more about Types of behaviors in animals

Nervous impulse:

The nervous system of an animal transmit signals from environment to the point, behavioral response occurs due to this transmission.

Stimulus:

suppose the external stimulus is tactile (Animal is touched by something). It responds to this stimulus, A wave of electrical activity moves down along the axons of sensory nerve cells That are in contact with the skin. Not all stimuli produce such a response. The stimulus must exceed The nerve cell’s threshold. Then nerve  impulse starts. Threshold is a function of amount of change  in the voltage across the neuron’s membrane. The stimuli that don’t meet this  Threshold Fail to cause the nerve cell to fire. The stimuli above the Threshold  always Causes the nerve cell to fire. The nerve cell Threshold  are equivalent of on off  switches, Rather than a diameter switch. any stimulus greater than threshold causes the nerve cell to fire. the nerve cell fires in exactly the same manner weather stimulus 1 percent  greater than  threshold or 1000 percent greater. The nerve cell fires by same way each time it’s threshold is reached but  Organisms are still able To use their nervous system to Measure  strength of a stimulus in two ways.

1.The number of times and neuron fires increases with the strength of the stimulus.

2.Number of neurons that fire in response to a stimulus also increases. it shows stimulus strength.

Transmission on impulse:

Once an impulse has reached the end of an axon, It is transmitted to other neurons. This transmission may involve.

A.   An electrical impulse jumping across the synaptic gap between neurons.

B.   Or, release of a neurotransmitter like acetylcholine.

Neurotransmitter is  released from  thousands of synaptic vesicles. These vesicles  are located on the tips of branches at the end of Axon terminals.

Response:

The neural  pathway was initiated by touching of an animal.  it may end when the Terminal neuron  in the pathway innervate some effector like muscle. Effector takes action, in this case Terminal neuron stimulates foraging behavior by opening or closing the jaw muscle. It may initiate fight behavior  by innervating muscles Associated with such fight  aggressive,  dominant group member.

Excitatory and inhibitory effect:

Our example involve the  neuropathological  response to touch.  it is focused on a stimulus  that causes an excitatory response  along the nervous system.  It is eventually  translated  into an animal taking some behavioral action. (For example  Foraging , fleeing). But some stimuli cause  inhibitory effects. In an inhibitory effect neuron sends a signal  that does not meet  threshold of the cell.  The cell receives such signal. It results in the inhibition of behavior. such inhibitory response may be lifesaving.