Sensitivity/Stimuli
Every living organism needs some sort of stimuli or sensitivity. Without this stimuli, organisms will not be able to defend themselves when they are in danger, eat when they are hungry, grow when they need to and so much more.
Sensitivity is what many animals, plants and even ourselves need so that we can detect all these problems or situations we may have. To understand the use and ability of stimuli, you must gain knowledge of the most important part: The Nervous System.
Sensitivity is what many animals, plants and even ourselves need so that we can detect all these problems or situations we may have. To understand the use and ability of stimuli, you must gain knowledge of the most important part: The Nervous System.
Coordination/Response
Organisms are stimulated to different kinds of things.
- External (outside the organism) and Internal (inside) stimuli
External stimuli is anything that happens outside the actual organism. E.g. Sting of a bee, a falling cup. Internal stimuli is anything that happens inside. E.g. Change in temperature, digestion
Information gained from any stimulation can produce different impulses or messages. There are chemical and electrical responses. Chemical responses can take longer times and can take maybe a few minutes or hours after the stimulation. Electrical responses happen very quickly and can take seconds to milliseconds to stimulate.
- External (outside the organism) and Internal (inside) stimuli
External stimuli is anything that happens outside the actual organism. E.g. Sting of a bee, a falling cup. Internal stimuli is anything that happens inside. E.g. Change in temperature, digestion
Information gained from any stimulation can produce different impulses or messages. There are chemical and electrical responses. Chemical responses can take longer times and can take maybe a few minutes or hours after the stimulation. Electrical responses happen very quickly and can take seconds to milliseconds to stimulate.
Bee Example
1) A bee lands on your skin 2) Receptors detect this pressure 3) Information from dendrites travel along the sensory neuron 4) Information travels to the relay neurons 5) Relay neurons send information to the brain 6) Brain sends commands back to the motor neuron 7) Motor neuron initiates command - the hand flicks bee off.rweq |
The Nervous System
How the Nervous System Works
The nervous system is the head department of stimuli. The nervous system consists of two important aspects. There are the the PNS (Peripheral Nervous System) and the CNS (Central Nervous System)
The process of stimulation follows on like this:
Senses (receptors) --> Peripheral Nervous System (PNS- Neurons) --> Central Nervous System (CNS)
The nervous system is the head department of stimuli. The nervous system consists of two important aspects. There are the the PNS (Peripheral Nervous System) and the CNS (Central Nervous System)
The process of stimulation follows on like this:
Senses (receptors) --> Peripheral Nervous System (PNS- Neurons) --> Central Nervous System (CNS)
Peripheral Nervous System:
The peripheral nervous system or the PNS is the part of the nervous system which consists of the nerves and neurons which help to transfer signals to muscles and other parts of the body. Neurons: Neurons are a specialized cell in the nervous system. They are used to transmit signals from different parts to the body (from receptors) to the brain and back. Essentially they are like little bridges. A connection from one neuron to another is called a synapse. There are three types of neurons - motor, sensory and relay. Sensory neurons what senses different things. It works with the five sense organs: Eyes (see) , Ears (hear) , Nose (smell) , Tongue (taste) , Skin (feel). Each organ has certain things called receptors. They are small cells that turn energy into impulses which then travel down the neurons, to the CNS. Eyes have light receptors (enabling us to see) Ears have sound receptors (enabling us to hear) Nose have smell and taste receptors (enabling us to smell. They have taste because it is connected with the mouth) Tongues have taste receptors and skin has touch, pressure and temperature receptors. Once receptors indicate some kind of energy and translate this into impulses - the impulses travel down the sensory neurons to the CNS. Relay neurons or inter neurons are neurons which relay information. Sensory neurons pass the impulses down to these relay neurons. the relay neurons will then either process this information and pass it down to a neuron or send it to the brain and then pass it down to another neuron. Motor neurons are neuron which receives the signals from CNS and tells muscles and glands what to do and they will carry out the response. |
Central Nervous System:
The central nervous system or the CNS is the main part of the nervous system. It consists of the two most important parts of a living organism, the brain and the spinal cord. The brain is the master control - it is what tells everything to do what. Signals are sent to the brain and the brain sends signals back giving a certain part of the body to do something. The spinal cord is where all these signals go through. The spinal cord is like the middle of a crossroad, it connects them all together. Without the spinal cord, most of our body will be disabled. The function of a neuron
Dendrites: Dendrites are parts of the neuron which branch off. They are sticky looking thing in where impulses are created. Axon: Once these impulses are created, they travel down the axon. The axon is the stem like part of a neuron in where the end is.] Synapse: A connection from one neuron to another. Cell Body: The part of a neuron and any cell which contains the nucleus and many more parts of a cell. |
In Addition to the 3 Neurons...
In addition to the 3 types of neurons, there is an extra type of neuron with equal vitality. Pyramidal neurons are neurons which are located in the brain. They connect with relay neurons and are what enable the commanding or computing of the brain.
In addition to the 3 types of neurons, there is an extra type of neuron with equal vitality. Pyramidal neurons are neurons which are located in the brain. They connect with relay neurons and are what enable the commanding or computing of the brain.
Plant Stimuli
Despite looking fragile and weak, plants actually have their own kind of stimuli. Remember, any organism must have the aspects of MRS GREN. S = Stimuli, meaning that every single living organism must have stimuli - including a plant.
Auxins
Plants have things called auxins, which act as growth hormones located at the tips of stems and roots. This auxin is produced in tips and are what stimulate growth. If a tip of a shoot is broken off, no auxin will be left because those are where those are made therefore stopping the process of growth. If a tip of a shoot is exposed to sunlight, the shaded part of the shoot will be provided with more auxin. The auxin on the shaded side will produce growth on the side - resulting the plant to grow towards the light. If a plant is growing sideways, the amount of auxin is produced on both side, but the auxin is moved downwards due to gravity. The lower side will grow faster and the shoot will grow upwards. Roots will experience a distribution of even auxin on the lower side - but extra auxin causes the root to grow downwards. Roots also grow towards moisture. If moisture ends up on one side, more auxin is produced. |
Plants react to things called tropisms. Tropisms are responses from a plant by an outside stimulus.
There are about 3 main types of tropisms.
Thigmotropism is the response to touch. Thigma in greek actually means touch. An example of thigmotropism is with prickles. When touched, their leaves shriver. Gravitropism is the response to gravity. If plants grow downwards, that is called positive gravitropism. But if it grows upwards, it is negative gravitropism. Phototropism is when a plant responds to light. If a plant grows towards light, it is called positive phototropism. If it's growing away from the light, it is called negative phototroprism |
Bear stimuli
Bears and humans have very almost the same nervous system. Though they use these in different ways.
Sweat
Bears are much like dogs and do not have sweat glands. Unlike a human who needs sweat glands to get rid of a rise of temperature in the body- bears have their own techniques. Instead, high rises in body temperature stimulates them to:
All these are electrical or physical responses.
- Pant
- Submerge in water
- Maintain a certain diet
- Sleep in cool areas
All these are electrical or physical responses.
Sight/Hunting
It is very common for people to think that the bear doesn't have good eyesight. But this is a normal misconception. The grizzly bear actually has a fairly decent eyesight which can be compared to humans.
A bear biologist in Alaska was able to record and witness this:
“It was late September and the ground was snow-covered when we peeked just our heads above a ridge that was a quarter-mile distant from the bears,” he said. “The adult male immediately stopped what he was doing, stared our direction, and ran – and kept on running until he was out of sight. If there was a wind it was only slight, and I don't recall it being at our backs. We were very aware of bears’ extremely perceptive sense of smell, but from the evidence available to us at the time, it seemed most likely that the bear was alerted by its eyesight.”
(http://www.adfg.alaska.gov/index.cfm?adfg=wildlifenews.view_article&articles_id=135)
The grizzly bears eyes have very good light receptors which is what enables them to see from miles away.
A bear biologist in Alaska was able to record and witness this:
“It was late September and the ground was snow-covered when we peeked just our heads above a ridge that was a quarter-mile distant from the bears,” he said. “The adult male immediately stopped what he was doing, stared our direction, and ran – and kept on running until he was out of sight. If there was a wind it was only slight, and I don't recall it being at our backs. We were very aware of bears’ extremely perceptive sense of smell, but from the evidence available to us at the time, it seemed most likely that the bear was alerted by its eyesight.”
(http://www.adfg.alaska.gov/index.cfm?adfg=wildlifenews.view_article&articles_id=135)
The grizzly bears eyes have very good light receptors which is what enables them to see from miles away.