Homeostasis RW.pptx
Transcript
Homeostasis and Disease Concept review What do all cells require in order to survive? Concept review What do all cells require in order to survive? Ability to: Obtain oxygen - respiration Obtain energy – food, nutrition, light respond to stimuli - Control system/Sensitivity reproduce excrete waste g...
Homeostasis and Disease Concept review What do all cells require in order to survive? Concept review What do all cells require in order to survive? Ability to: Obtain oxygen - respiration Obtain energy – food, nutrition, light respond to stimuli - Control system/Sensitivity reproduce excrete waste grow move Concept review In groups, explain how our main organ systems e.g. circulatory system, digestive system, excretory system, work together to ensure all cellular needs are met? Use the puzzles to help you visualise the main body systems, create and create a flowchart/concept map to help explain your answer Hint: Focus on oxygen and nutrition Homeostasis Homeostasis is the term we use to describe the maintenance of a relatively constant internal state despite changes in an organism's external environment. All organisms/cells function best within set tolerance limits, Examples: optimum human conditions body temperature = 36.5 – 37.5 °C blood glucose levels = 79 to 110 mg / 100mL Factors that affect homeostasis There are a number of different factors that affect the body’s internal balance. Examples include Exposure to extremely high or low temperatures Lack of nutrition Lack of water Presence of disease Types of Disease Infectious: can be transmitted from one person to another E.g. flu, measles, chicken pox Non-infectious: cannot be transmitted from one person to another E.g. cancer, genetic disorders, mental health disorders How do we maintain homeostasis when our bodies are exposed to different conditions? Organisms, particularly complex organisms like humans use a range of structural, functional and behavioural mechanisms to maintain homeostasis. Task In small groups, discuss some of the ways in which our bodies respond to factors that affect homeostasis. Record at least 5 examples in your notes. Mechanisms to maintain homeostasis: Examples Structural (structures you body has) Presence of fat tissue to insulate internal organs Functional (how your body works) Sweating or shivering to regulate temperature Decreasing urine output when dehydrated Immune system response when exposed to a pathogen Behavioural (things you choose to do) Seeking shade when its hot How is homeostasis controlled? In humans homeostasis is controlled by the nervous system and endocrine system These systems work to detect changes and relay messages to other body systems (e.g. the circulatory system), in order for them to respond. They also interact with your immune system to help keep you free of disease. Stimuli Stimuli that the body can detect include: ○ ○ ○ ○ ○ ○ Temperature Light Touch Smell Sound Pain For every stimuli that is detected by the body there is a response, although you may not be aware of it. Eg; when your pupils contract when exposed to bright light Stimulus & Response Stimuli are detected by receptors in the body. These include: ○ Chemoreceptors ○ Mechanoreceptors ○ Photoreceptors ○ Thermoreceptors Depending on where the receptors are located, they can: receive signals from the external environment (outside the body). ○ E.g. taste buds receive signals from the body’s internal environment. ○ E.g. the hypothalamus (a part of your brain) can determine your internal body temp. Responding to stimuli is necessary for: ○ Major development processes, including growth and reproduction ○ Homeostasis ○ Surviving the external environment Practical Activity: Feeling hot, feeling cold See page 99 in your text books. Nervous system Comprised of: Central nervous system ○ brain and spinal cord ○ Responsible for processing, storing and coordinating information Peripheral nervous system ○ all other neurons in the nervous system ○ Responsible for transmitting information to and from the CNS. Organisation of the nervous system The nervous system is made up of trillions of nerve cells, called neurons. Neurons are responsible for passing electrical messages - from the receptors - to the central nervous system for processing - then to the effectors (the muscles or organs) that respond Stimulus (input) receptor Processing centre (transfer of signal) effector Response (output) Neurons are generally made up of: A cell body where the nucleus is located. Dendrites – branching extensions that receive signals from adjacent neurons or a receptor. Axon – an extension of a nerve cell that transmits nerve impulses away from the cell body. Myelin sheath – acts as insulation; assists in transmission of electrical impulses; increases speed of impulses. Axon terminals – pass electrical impulses onto adjacent neurons or muscles/organs Task Research and wrrite a brief description of the structure (including a diagram) and function of: Sensory neurons: Motor neurons: Connector neurons: Types of neurons Sensory neurons: transmits information from sensory receptors to the CNS. Motor neurons: Transmits signals from the central nervous system to effector cells/organs. Connector neurons: connect with other neurons to help transmit messages. How messages travel along nerve cells Your neurons carry messages in the form of electrical signals called nerve impulses. To create a nerve impulse, your neurons have to be excited. Sensory neurons are excited by messages they receive from receptors, whilst other types of neurons are excited when receptors on their dendrites detect chemicals released by other neurons. The detection of specific signals triggers a nerve impulse which travels down the cell, through the axon to the axon terminal. Adjacent neurons do not touch but have a gap between them called a synapse. When the electrical impulse reaches the end of one neuron it triggers the release of chemicals called neurotransmitters. The neurotransmitters cross the synapse and bond to receptors on the dendrites of the following neuron. This triggers an electrical impulse to start travelling down the following neuron, passing the message on. Main types of neurotransmitters There are many different types of neurotransmitters. They can be classified as: ○ Excitatory: which cause the neurons to fire more ○ Inhibitory: those that stop the neurons firing Application Task: Neurotransmitters Part 1: Using the internet to help you, complete the table below. Type of Neurotransmitter Dopamine Serotonin Melatonin GABA Acetylcholine Excitatory or Inhibitory Role in the body Application Task: Neurotransmitters Part 2: Using you knowledge of neurotransmitters gained in part 1, answer one of the following. 1. Most teenagers would agree that the school day should start at 10am rather than 9am (or for those poor students in America at 7.30am). Use Science to justify why this should occur. 2. Many sedative/tranquilizing drugs act by enhancing the effects of GABA. Explain why this is the case and justify why it is important to ensure that these types of drugs are only used at the correct levels. 3. Explain why the Evil Queen most likely used hemlock (a poison which blocks the acetylcholine receptors on muscle cells) when she tried to get rid of Snow White. 4. Much to her disgust, Emma’s parents have banned her from using her phone and computer after 9.30 pm because they say it will help her sleep. Explain to Emma why they are correct. 5. Is she “hangry” or just lacking in serotonin? Justify your response. Endocrine system The endocrine system is made up of a series of glands that produce hormones. The endocrine system is coordinated by the pituitary gland which responds to information sent to it by the hypothalamus. Class activity: Endocrine debate In groups of students will be assigned one of the endocrine glands. Groups will have 15 mins to research their allocated gland. It is recommended that you research an overview of the normal gland function; including hormones produced and the action of these hormones in the body. You can also look up info related to what would happen to the body of the gland doesn’t work properly. Groups will then have 10 mins to use their notes to put together a convincing argument as to why their gland is the most important gland in the body. Hypothalamus The hypothalamus plays a vital role in maintaining homeostasis. It links the nervous system and the endocrine system It monitors the bodies internal conditions and controls body temperature, metabolism and water content. When the hypothalamus detects a change, it secretes hormones that act on the pituitary gland. The pituitary gland then responds by producing more or less of it’s own hormones. Hormones Hormones are chemical messengers They are produced in very small amounts by the glands and excreted into the blood stream. They travel through the bloodstream to your cells. Hormones are specific in their action. Each hormone type will only recognise a specific type of receptor on the cells. When the hormone binds to it’s receptor it activates a specific response. Feedback mechanisms The way in which the body responds to a change is described as a feedback mechanism. Feedback can be classed as: Negative: when the response is to reverse the original change. E.g. When body temperature rises, the response it to bring it back down. Positive: when the response is to produce more of the change. E.g. Contractions during child birth. Small contractions trigger stronger ones, until the baby is born. Blood glucose regulation Controlled by two hormones: Insulin: When glucose levels are high. Controls the uptake of glucose from the blood into the cells, where it is stored as glycogen. Glucagon: When glucose levels are low. Triggers the break down of glycogen and the release of glucose into the blood. Water balance Controlled by the hypothalamus. When the body is dehydrated the hypothalamus releases Antidiuretic Hormone (ADH) ADH travels to the kidneys where it stimulates the reabsorption of more water.
