NS TEST 1 HUMANS AS RESPONDERS PDF

Introduction: Humans and all living organisms are constantly being bombarded with information from the environment. These little bits of information are known as stimuli and can come from our external environment (outside our bodies) or our internal environment (inside our bodies)....

Introduction: Humans and all living organisms are constantly being bombarded with information from the environment. These little bits of information are known as stimuli and can come from our external environment (outside our bodies) or our internal environment (inside our bodies). Reproduction Humans need to respond to stimuli to reproduce and maintain Animals respond to stimuli related to mating opportunities, such homeostasis in order to survive. Here are the main reasons why as visual displays, scents, or sounds, ensuring the continuation this ability is crucial: of their species. Avoiding Danger Homeostasis Responding to harmful stimuli, such as predators or Maintaining a constant internal environment. This requires environmental hazards, helps animals escape or protect responding to stimuli like temperature, light, or dehydration. For themselves. example, sweating or shivering helps regulate body temperature. Finding Food and Water Responding to the Environment Stimuli, like the smell of food or the presence of water, guide Animals must adjust their behaviour to t their surroundings animals toward resources necessary for survival. EG: seasonal changes, weather, or the presence of competitors, ensuring they can be successful in ever-changing environments. 3 fi  Communication and Social Behavior In this section will focus on how humans respond to Many animals rely on responding to signals from others, such as their environment: alarm calls, social bonding cues, or territorial warnings, to External Environment: navigate social structures and group dynamics. The nervous system A typical nervous response Without the ability to respond to stimuli, animals would be How drugs affect the brain unable to adapt to changing environments, avoid threats, or Responding to external threats ful l their biological needs. This capability is a fundamental part Predators and prey of life. Responding to changes in temperature Internal Environment: The Endocrine System Responding to changes in sugar The Excretory System Responding to changes in salt Removing excess wastes The Immune System Responding to infections Vaccines Communication: Ants communicating through the physical touch of their antennae and through chemicals known as pheromones. 4 fi External Environment Nervous System A Typical Nervous Response Responding to external threats Responding to changes in temperature 5 Nervous System Responding to Stimuli Being able to respond to any stimulus requires the ability to gather or receive the stimulus, interpret it, and then respond to it correctly. We will look at the nervous system as a whole, nerves and what happens in a typical nervous response. We will also look at how drugs affect the brain. Lastly, we will look at how we respond to threats and regulate our internal body temperature. 6 Nervous System The Structure of the Nervous System The nervous system is made up of special cells that send nerve impulses, known as neurons. The nervous system can be divided into two major regions: Central Nervous System (CNS): The brain and spinal cord Peripheral Nervous System (PNS): Nerves branching off of the CNS Sensory pathways / neurons Motor pathways / neurons Neurons are typical animal cells in the sense that they have a nucleus and membranes, but their shape is adapted to be able to carry nerve impulses over long distances in the body. For example, the sciatic nerve runs from the lower back down to the toes (± 1 meter long, depending on your height). Neuron Structure: Nucleus: Contains DNA, controls the functioning of the cell Cell Body: The main body of the cell containing organelles Dendrite: Carry nerve impulses towards the cell body Axon: Carry nerve impulses away from the cell body Axon Terminal: Where the neuron connects to a muscle or a gland Myelin Sheath: Insulates the neuron and speeds up the nerve impulse 7 Nervous System A Typical Nervous Response Stimulus It all starts when our bodies receive a stimulus. Receptors are special cells that can receive different sorts of stimuli. Receptor Receptors in our eyes gather the stimulus of light. Receptors in our ears gather the stimulus of sound. There are many receptors in our skin that can pick up many stimuli like: Sensory Neuron touch, pressure, hot and cold. Once received, the stimulus needs to make it to the brain so we can decide Brain what to do with the information. Sensory neurons are special nerve cells that carry the stimulus from the receptor to the brain. Motor Neuron Once interpreted, the brain can decide how to respond. It sends a nerve impulse via a different kind of nerve cell, a motor neuron, to an effector. Effectors are most often our muscles or our glands. Effector When the effector does its thing (move, secrete a substance) a response to the stimulus is brought about. Response 8 Nervous System A Typical Nervous Response Let’s look at an example to make sure we understand this properly. Suppose you are walking along, and suddenly, you see a snake. You immediately jump backwards to a safe distance to avoid being bitten. Here, the stimulus is the light entering your eyes that allows you to see the snake. The receptors are the special cells in your eyes that actually receive the light. You may have heard of them before; they are known as rods and cones. The sensory neuron sends a nerve impulse to the brain, which quickly interprets the visual information as “snake, dangerous”, and sends a nerve impulse via motor neurons to the muscles, the effectors, getting you to jump back, the response. You try: Draw a ow chart like the one on the previous page but with 7 empty boxes. Fill in the steps of a typical nervous response for the following scenario: It’s just before lunch, and you can smell the delicious food being cooked in the dining hall. You begin salivating. 9 fl Nervous System How Do Drugs Affect the Brain 10 Nervous System Responding to External Threats - Predators & Prey Our ancestors lived in a world where large predators were a real threat. From sabertooth cats and cave lions in the past to wolves, bears, lions, leopards and tigers, more recently, our ancestors had to learn to compete with and survive amongst top predators. Today, the threat of being taken down by a predator, for most humans, is not a real threat. We will take a look at how predators and prey interact and some of the senses that allowed us to thrive and outcompete these animals. 11 Nervous System Responding to External Threats - Predators & Prey A predator is an organism that hunts and kills another organism, the prey, for food. Predators play an important in environments. By hunting and killing their prey, they prevent prey numbers from getting too high and damaging ecosystems. Also, because they often prey on weak, slow and/or sick individuals, they help to keep the prey population genetically t. Of course, only the predators successful at hunting survive, so the predator population remains genetically t too. Predators would have posed a huge threat to early predators, A line graph showing a predator-prey relationship: but as humans learned to use re, learned to make better The predator and prey populations change constantly, and one will weapons and got better at tracking and understanding animal always in uence the other. behaviour, the tables began to turn. The populations tend to change in predictable, cyclical patterns. The predator population lags slightly behind the prey population. How high and low the peaks and troughs get can be in uenced by Nowadays, predators pose little threat to the daily existence of factors such as drought, rain, disease, and res. Think about how the introduction of a different predator or prey most people. species to an area might affect the above relationship. 12 fl fi fi fi fi fl So, how did early humans survive against the odds? ever better tools and weapons. However, one of the main ways our brains gave us an advantage was in the ability to interpret The main ways that early humans would have detected things from our surroundings. predators were through their eyes (sight) and through their ears (sound). By looking at tracks on the ground, early humans learned to understand which animals had been through an area and how However, in comparison to wild animals, our senses generally recently. They could analyse and predict where the animals are not that acute. We do not see, hear or smell better than were going, and so, became more successful at hunting. most other animals, and yet, humans evolved to become among the most dominant of organisms on the planet. How did this They learned animal behaviours and how to read signals that happen? ultimately kept them alive. Thus, our brain’s ability to interpret stimuli gave us an edge in coexisting with animals and The real secret was the development of our brains. Our high outcompeting the predators that once ate us. intelligence allowed us to develop complex language and make Listen to this podcast episode on lion tracking to get some idea of how experienced trackers read signs and energy levels within animals: YouTube Link / Podcast Link 13 Nervous System Responding to Changes in Temperature Humans must maintain an internal body temperature of 37°C to ensure that the chemical reactions taking place in our bodies occur fast enough to be ef cient. We will take a look at how the body responds when the internal temperature rises above or falls below 37°C. 14 fi Nervous System Responding to Changes in Temperature Controlling our internal body temperature comes down to controlling two main physical processes: radiation and evaporation. Radiation: Heat loss through the emission of infrared waves. Think of heating up next to a re or being warmed by the sun. Because we generate energy internally through all the chemical reactions taking place in our bodies, we must be able to lose that energy to avoid overheating. The body loses heat passively to the environment all the time, and we must constantly eat food to provide the energy we need to maintain our body temperature at 37°C. If the external environment is warmer than the body, then heat loss via radiation slows down. Evaporation: the process of losing heat through the conversion of water to gas. Water in our sweat takes in heat energy from our bodies until it becomes a gas and evaporates. As the warmed up water molecules leave the surface of the body, they carry away heat, which in turn, cools the body down. 15 fi Nervous System Responding to Changes in Temperature: Above 37°C When our internal body temperature rises above 37°C, it Temp above 37°C must be brought back down so that important proteins in our bodies, like enzymes and proteins, are not damaged. We do this by increasing blood ow to the skin, which Heat receptors increases heat loss through radiation. In addition, we begin sweating, which helps take heat away from the body via evaporation. Sensory Neuron Brain Motor Neuron Motor Neuron Blood vessels in the Sweat glands produce skin dilate more sweat More heat lost 16 fl Nervous System Responding to Changes in Temperature: Below 37°C When our internal body temperature drops below 37°C, it Temp below 37°C must be brought back up so that important chemical reactions can occur fast enough. We do this by decreasing blood ow to the skin, which Heat receptors decreases heat loss through radiation. In addition, we stop sweating and may even begin to shiver. Shivering moves the muscles, and this generates heat. Sensory Neuron Brain Motor Neuron Motor Neuron Blood vessels in the Sweat glands produce skin constrict no sweat Less heat lost 17 fl Internal Environment Endocrine, Excretory & Immune Systems Responding to changes in sugar Responding to changes in salt Removing excess wastes Responding to infections 18 Endocrine System Responding to Changes in Sugar Humans must maintain their blood sugar levels at less than 100 mg/dL (5.6 mmol/L) to ensure that there is enough sugar to supply the cells with energy, but not too much or too little, as this is dangerous to our health. We will take a look at how the body responds when blood sugar levels go above or below normal and at what diabetes is. 19 Endocrine System What is the deal with blood sugar anyway? It is important that our blood carries sugar. This, in turn, can cause problems like: Kidney disease The speci c sugar we refer to when we talk about blood sugar Stroke levels is glucose. Heart attack Glucose is converted by all the cells of the body to energy, Vision loss / blindness which the cells use to perform their tasks. This energy allows us Poor blood ow to legs and feet to move, make proteins and send the nerve impulses that get Slow wound healing the nervous system to function. If blood sugar drops too low, there is not enough glucose to sustain the neurons in the brain, which can cause it to “shut down” and go into a coma. If this is not reversed quickly, then it may cause damage to the brain and eventually death. If blood sugar is too high, it can cause plaque to build up in arteries, making it dif cult for blood to ef ciently pump through the arteries and reach areas like the eyes, legs, feet, and kidneys. This plaque build-up, or hardening of the arteries, is known as atherosclerosis. 20 fi fl fi fi Endocrine System Blood Glucose Levels Fasting: This is where the doctor requires you to eat nothing for 10-16 hours before testing for glucose 21 Endocrine System Extension: What is a Mole? Answer: A mole is… 22 Endocrine System Responding to Changes in Sugar: Above Normal When our blood sugar level rises above normal, the pancreas Blood sugar above normal detects this. A nerve impulse is sent to the brain, which sends an impulse back to the pancreas, causing it to secrete insulin. Insulin is a hormone that causes the liver and the muscles to Pancreas detects high blood sugar take glucose out of the blood and store it in the cells. Because glucose is being removed from the blood, blood glucose levels drop back down to normal. Sensory Neuron Brain Motor Neuron Pancreas secretes insulin Blood sugar levels decrease 23 Endocrine System Responding to Changes in Sugar: Below Normal When our blood sugar level drops below normal, the pancreas Blood sugar below normal detects this. A nerve impulse is sent to the brain, which sends an impulse back to the pancreas, causing it to secrete glucagon. glucagon is a hormone that causes the liver and the muscles to Pancreas detects low blood sugar release stored glucose into the blood. Because glucose is being released into the blood, blood glucose levels rise back up to normal. Sensory Neuron Brain Motor Neuron Pancreas secretes glucagon Blood sugar levels increase 24 Endocrine System What is Diabetes Diabetes is a condition that happens when your blood sugar (is Type 2 Diabetes: too high. It occurs when your pancreas doesn’t make The pancreas produces insulin, but the cells it affects in the enough insulin or when your body isn’t responding to the effects muscles and liver become resistant to it. It is most often brought of insulin properly. on by poor diet and health choices. Taking insulin injections, therefore, has no effect, and treatment If your blood sugar after fasting is 5.6 to 6.9mmol/L, then you focuses on a healthy diet and regular exercise. may be at risk of diabetes. 7mmol/L or higher, and you are said to have diabetes. Some early warning signs include increased thirst, frequent urination and numbness/tingling in hands or feet. Type 1 Diabetes: Usually occurs in adolescence. The pancreas produces little or no insulin, so the body has no way to control high blood sugar levels. Treatment involves monitoring glucose levels, taking insulin, eating healthy foods and exercising regularly. 25