Which structure is at work when the body deals with reflex actions? the heart the brain stem the vertebral column the spinal cord

The answer is spinal cord

Its spinal cord

Explanation:

Reflex action is an instantaneous involuntary response to a stimuli. Like when you touch a hot object, instantaneously you move your hand away from the heat source, such action is reflex action. It happens suddenly without much thinking. Spinal cord plays a major role in this. Please look at the reflex arc below for further clarification. The path followed by reflex action is called reflex arc.

Stimulus -> sensory receptor -> sensory neuron -> relay neuron (in spinal cord) -> motor neuron -> effector -> response

white blood cells or wbc s are mainly 2 types-

1.agranulocytes

2.granulocytes

the monocytes or macrophages of agranulocytes , dendritic cells which are accessory leucocytes, and b cells which is one type of lymphocytes   identify the antigens present on the pathogen's surface. these three cells are called antigen presenting cells(apc) which are phagocytes and destroy the antigens by secreting antitoxins. besides this leukocyte is always plays vital role in the immunity of the body.

sheep is a herbivore animal whereas grasshopper belongs to the class chordates but both of them feed on greens.  

if grasshopper and sheep feeding on a pasture land, i do not think both of them will have any impact on each other. however, the number of the species can make difference. since sheep feed on greens, there is a possibility there left no pasture land for the grasshoppers or they may get extinct.