The sensory system signals the changes to the mind which elicit a response. The response can be in the form of physical activity move, run, change shape, etc. Moreover, the stimulus can be detected by an organism only if it is higher than an absolute threshold.
The strength of the stimulus defines whether a nerve fiber will fire. The stimulus will affect only if a certain threshold is reached. Below that threshold, the neurons will not transmit any data to the brain.
There are two main types of stimulus —the external stimulus and the internal stimulus. The response to any type of stimulus is either learned or instinctual in nature. For example, a deer will flee as a response after seeing a predator whereas a human response can be different, such as hiding, or driving the car away, or firing a bullet. All of these responses are learned responses while the response of deer was instinctive.
The external stimulus includes touch and pain, vision, smell, taste, sound, and balance equilibrium. These sensory stimuli are activated by external changes.
As the name implies, the internal stimulus comes from within the organism. For example one of the internal stimuli is hunger which is the sign of low energy in the body.
It stimulates us to eat something to regain the needed energy. Read: Homeostasis — Definition and Examples. The major requirements of a plant are water and sunlight. The plant responds to many types of external stimuli such as light, gravity, weather, and touch. The response of a plant is either positive grow towards the stimulus or negative grow away from the stimulus.
Similarly, gravitropism in plants responds to the stimulus, i. Ideally, the plant should remain in an upright position to gain the required nourishment. If a plant falls, the auxin levels in the lower part of the stem will increase stimulating cell elongation causing the stem to bend towards the sky. An example of stimulus in animals is the sight of another animal especially predators where they respond by fleeing away or fighting.
In animals, most of the responses as a result of stimulus are of instinctual nature. Dogs can be trained to respond to certain words such as sit, stand, eat, etc. The voice of the human acts as a stimulus for the dog and it responds accordingly. Humans are supreme in terms of mental capabilities and thus respond to several stimuli apart from basic ones such as taste, smell, temperature, sound, etc. The stimulus in humans can be a sight of a picturesque scene or the smell of food.
Human behavior itself is a stimulus for another human. A kind and soft behavior will have a positive impact on others. A sensory system is a part of the nervous system consisting of sensory receptors that receive stimuli from the internal and external environment, neural pathways that conduct this information to the brain and parts of the brain that processes this information.
Know the different sensory systems of the human body as elaborated by this tutorial Read More. Neurons generate electric signals that they pass along to the other neurons or target tissues. In this tutorial, you will find the basic structure of a neuron, the different classes of neurons, and membrane potentials. It also includes the structure of the nervous system Homeostasis is the relatively stable conditions of the internal environment that result from compensatory regulatory responses performed by homeostatic control systems.
Know the different components of homeostatic control systems, homeostatic regulators, and the various biological processes that homeostasis entail Plants, like animals, produce hormones to regulate plant activities, including growth. They need these hormones to respond well to their environment and to sustain growth, development, and dispersal. Plant biologists recognize five major groups of plant hormones: auxins, gibberellins, ethylene, cytokinins, and abscisic acid.
Find out in this guide the importance of each hormone in the life of a plant Some of the body movements can be controlled at will, others cannot. The body has a motor program, which is the pattern of neural activities required to perform a movement. Learn more about this topic in this tutorial. Find out the mechanisms involved in length-monitoring systems, alpha-gamma coactivation, and withdrawal reflex Human consciousness and behavior are an interesting topic since they are determined and controlled by the brain.
Consciousness can be defined by behavior or by electrical pattern of brain activity. Read this tutorial to learn about brain activities, such as sleep, attention, emotion, motivation, consciousness disorders, learning, and memory Effects of Gravity on Sleep. Skip to content Main Navigation Search.
These rapid changes, called stimuli , provoke reactions in living organisms that are often very different from those expected from nonliving things. For example, if a pound rock a nonliving object is pushed across a smooth surface the stimulus , it will respond in a predictable manner by moving a predictable distance in a straight line the response.
The force of the push and the result it produces can be reduced to a mathematical formula which can then be used to make accurate predictions about the behavior of this rock, and then other rocks, under similar sets of circumstances. If, however, the same force or stimulus is applied to a large growling dog, the dog may move away or, equally well, turn and attack the person applying the force!
The response obtained is certainly not predictable from simple mechanical laws. Similarly, if a bird is pushed it will probably fly. Push a frog and it will jump.
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