Biology101 Exam #4 Study Guide
Biology101 Exam #4 Study Guide BIO101
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This 17 page Study Guide was uploaded by emilyecclestone on Thursday February 11, 2016. The Study Guide belongs to BIO101 at Wake Forest University taught by Dr. Carole Gibson in Fall 2015. Since its upload, it has received 21 views. For similar materials see Biology 101 in Biology at Wake Forest University.
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Date Created: 02/11/16
Biology Exam #4 Notes Physiology Homeostasis 1. What is it? • Maintenance of a relatively stable internal environment even when the external environment changes, including: o Blood pH o Carbon dioxide concentration o Blood glucose concentration o Body temperature o Water balance 2. How does it work? • Body temperatureànegative feedback o HIGH temperature § Stimulusà increased body temperature § Thermostat in hypothalamus activates cooling mechanisms § Option A: Skin blood vessels dilate àcapillaries fill with warm blood; heat radiates from skin surface § Option B: Sweat glands activated, increasing evaporative cooling § Body temperature decreases àthermostat shuts off cooling mechanisms o LOW temperature § Stimulusà decreased body temperature § Thermostat in hypothalamus activated warming m echanisms § Option A: Skin blood vessels constrict àdiverting blood from skin to deeper tissues and reducing heat loss from skin surface § Option B: Skeletal muscles activated àshivering generates more heat § Body temperature increases àthermostat shuts off warming mechanisms • Blood glucose levels o HIGH blood glucose levels -‐ Hyperglycemic >120mg% § Stimulusà rising blood glucose level • After eating a carbohydrate rich meal § Beta cells of pancreas stimulated to release insulin into the blood § Insulinà Body cells take up more glucose OR liver takes up glucose and stores it as glycogen § If body cells take up more glucoseàblood glucose level declines to set point § Stimulus for insulin release diminishes o LOW blood glucose levels-‐ Hypoglycemic <80mg% § StimulusàRemoval of excess glucose form blood, low blood glucose level • After skipping a meal § Alpha cells of pancreas stimulated to release glucagon into the blood § Glucagonà liver breaks down glycogen and releases glucose to the blood § Blood glucose level rises § Stimulus for glucagon release diminishes 3. What does it do? Why is it important? • Thermoregulation 1. What is it? • Maintenance of a relatively stable internal body temperature (98.6*F, 37*C) 2. How does it work? • Hypothalamus releases hormones acting on the pituitary gland to release hormones • Pituitary gland sends hormones to thyroid • Thyroid stimulating hormone o Thyroid gland § Releases thyroxinàregulates metabolic rate • Animals capable of temperature regulation maintain a constant body temperature through a negative feedback loop o The hypothalamus acts as a control center by responding to fluctuations in body temperature o The skin possesses thermoreceptors also and relays this information to the hypothalamus • When body temperature rises, the following cooling mechan isms occur: o Vasodilation § The skin arterioles dilate, bringing blood into closer proximity to the body surface and allowing heat transfer (convective cooling) o Sweating § Sweat glands release sweat, which is evaporated at the cost of latent heat in the air, thus cooling the body (evaporative cooling) • When the body temperature falls the following heating mechanisms may occur: o Vasoconstriction § Skin arterioles constrict, moving blood away from the surface of the body, this retaining heat carried within the blood o Shivering § Muscles begin to shake in small movements, expending energy through cell respiration (which produces heat as a by -‐product) 3. What does it do? Why is it important? • Hypothalamus 1. What is it? • master coordinator region of the brain responsible for a variety of physiological functions 2. How does it work? • 3. What does it do? Why is it important? • Feedback loop 1. What is it? • A pathway that involves input from a sensor, a response via an effector, and detection of the response by the sensor 2. How does it work? • Positive feedback loop: o • Negative feedback loop: o When a variable deviates from the norm the result of the effector mechanism is to return the variable back to the norm § Deviation from norm àreceptoràcoordinating centeràeffectorsàreturn to norm o Body temperature is an example (see Homeostasis) 3. What does it do? Why is it important? • Pituitary gland 1. What is it? • An endocrine gland in the brain that secrets many important hormones 2. How does it work? • 3. What does it do? Why is it important? • Glycogen 1. What is it? • An energy-‐storing carbohydrate found in muscle and liver 2. How does it work? • 3. What does it do? Why is it important? • Stores glucose in the liver • Glycogen is stored in the liver Glucagon 1. What is it? • A hormone produced by the pancreas that causes an increase in blood sugar 2. How does it work? • Stimulates transportation of glycogen to blood stream • When blood glucose levels are low (after exercise) o Released from alpha cells in the pancreas § Causing an increase in blood glucose concentration 3. What does it do? Why is it important? • Raises blood glucose by triggering release of glycogen • May increase glycogen breakdown • May decrease rate of cell respiration • May increase release from adipose tissue Kidney 1. What is it? • An organ involved in osmoregulation, filtration of the blood to remove wastes and production of several important hormones 2. How does it work? • Filtration o Nephron § Glomerulus & bowman’s capsule § Proximal tubule § Loop of henle • Ultrafiltration • Excretion 3. What does it do? Why is it important? • Excretes waste • Balances water and salt excretion • Removes waste and extra fluid from the body to maintain the concentration gradient of body fluids • Most dispensable because there are two kidneys within the organ system, therefore, the body can continue to function proper ly with only one Osmoregulation 1. What is it? • Maintenance of relatively stable volume, pressure, and solute concentration of bodily fluids, especially blood 2. How does it work? • 3. What does it do? Why is it important? • Inability to osmoregulate may result in edemaàswelling of tissues or organs with fluid Metabolism 1. What is it? • Rate the body processes 2. How does it work? • Skinny personàhigh metabolism 3. What does it do? Why is it important? • Digestive System Digestion 1. What is it? • Mechanical and chemical breakdown of food into subunits, enabling absorption of nutrients 2. How does it work? • Glucose molecule enters the mouth, it begins as a carbohydrate (i.e. starch) in food • The macromolecule is broken down into a micromolecule by the e nzymes in saliva (salivary glands) to be easily absorbed by cells to be used by the body • The molecule then passes through laryngopharynx via the glottis, to be swallowed • It then travels down the esophagus and into the stomach to be broken down by proteins (through pepsin enzymes) • The molecule then passes through pyloric end, the end of the stomach that em pties into the small intestine • While in the small intestine, it passes through the duodenum leaving the pyloric end, into the jejunum and then the ileum • As it finishes passing through the small intestine, the glucose is absorbed into the blood stream • The blood stream then carries the glucose to a muscle with the help of insulin to enter the muscle 3. What does it do? Why is it important? • Most food is solid and in the form of large complex molecules which are insoluble and chemically inert o Large molecules need to be broken down into smaller molecules that can be readily absorbed across the membrane and into cells o Small molecules can be reassembled into new produc ts Pepsin 1. What is it? • Protein-‐digesting enzyme that is active in the stomach 2. How does it work? • 3. What does it do? Why is it important? • Lipase 1. What is it? • Fat-‐digesting enzyme active in the small intestine • Source: pancreas • Substrate: triglycerides 2. How does it work? • 3. What does it do? Why is it important? • Villi/Villus 1. What is it? • Fingerlike projections of folds in the lining of the small intestine wall that are responsible for most nutrient and water absorption 2. How does it work? • 3. What does it do? Why is it important? • Increase the surface area to help absorption o Absorptionàtransfer of nutrients from the digestive tract into the blood stream, usually through villi in the small intestine • The villus has surface cells with large numbers of mitochondria, whi ch active uptake of end products of digestion • Holds a dense capillary network beneficial for good blood supply to remove water -‐ soluble absorbed nutrients • The lacteal of the villus removes the end products of fat digestion and lipid soluble vitamins Insulin 1. What is it? • Hormone secreted by the pancreas that causes a decrease in blood sugar 2. How does it work? • When blood glucose levels are high (after eating) o Released from beta cells in the pancreas § Causing a decrease in blood glucose concentration 3. What does it do? Why is it important? • May increase glycogen synthesis • May increase rate of cell respiration • May increase uptake into adipose cells Diabetes 1. What is it? • Disease characterized by chronically elevated levels of blood sugar 2. How does it work? • Type 1 Diabetes: o Geneticàmutation § Usually early onset (childhood?) o Insulin dependent o Body does not produce insulin § Requires insulin injections o Caused by destruction of beta cells o Too much glucose in blood because of alpha cells o Takes water out of blood o Pancreas cells don’t function properly o Stem cells can help • Type 2 Diabetes: o Brought on by obesity § Usually late onset (adulthood?) o Is not insulin dependent o Body does not respond to insulin § Receptor malfunction o Caused by down regulation of insulin receptors (dietary cause?) o Controlled by monitoring diet § Weight lossàcure o Stem cells can’t help 3. What does it do? Why is it important? • Organs in the Digestion System: Digestive Organ Function Features Stomach Stores, mechanically break Strongly acidic, kills pathogens, down and digests proteins in pepsin stored in stomach wall foods, acts as a “storage tank,” (activated by presence of HCl) where protein digestion begins, turns food into a paste called chyme, empties into small intestine Small Intestine Site of where bulk of chemical Wall of small intestine c ontains digestion and absorption of villi to increase surface area and food, absorbs nutrients into the optimize absorption, enzymes bloodstream, empties into large needed for digestion come from intestine small intestine wall, bile from liver is released here Pancreas Produces enzymes (i.e. lipase) Alpha islet cellàproduce that act in the small intestine glucagon and secretes a juice that Beta islet cellsàproduce insulin neutralized acidic chyme , (islet cells are in the pancreas) carries digestive enzymes, releases insulin and glucagon Liver Produces bile salts that emulsify Stores glycogen fats Gallbladder Stores bile salts (from liver) and released them as needed into the small intestine Large Intestine Absorbs remaining water and water used in digestive process solid waste is formed, breaks is reabsorbed back into body down waste (via osmosis) Cardiovascular System Pulmonary Circuit 1. What is it? • Circulation of blood between the heart and the lungs 2. How does it work? • 3. What does it do? Why is it important? • Systemic Circuit 1. What is it? • Circulation of blood between the heart and the rest of the body 2. How does it work? • 3. What does it do? Why is it important? • Heart 1. What is it? • Muscular pump that generates force to move blood throughout the body • Myogenic muscle 2. How does it work? • Blood flow o Blood returning from all parts of the body (except lungs) enter the right atrium via the vena cavaàthis blood is relatively deoxygenated o Blood passes from the right atrium to the right ventricle and then by the pulmonary artery to the lungs (where blood is reoxygenated) o Blood returns to the left atrium via the pulmonary vein and passes through the left ventricle to the aorta, where it is pumped around the body • Heart valves o Maintain one way flow of blood § When atria contracts à atrioventricular (AV) valves open § Blood flows from the atria into the ventricles § When ventricles contract àAV valves close and semilunar valves open § This forces blood out of the ventricles and into the a rteries § Arterial pressure rises à semilunar valves close, ensuring one way blood flow 3. What does it do? Why is it important? • Control of heart beat • Contraction of heart tissue is myogenic o Signal for cardial contraction arises within heart muscle itself • SA nodeàsinoatrial node o Initiates contraction of the cardiac muscle o Acts as a pacemaker § Regulating sinus rhythm Regulation of heart rate • Pacemaker is under autonomic control from the brain o From the medulla oblongata (brain stem) • Sympathetic nerves speed up heart rate by releasing neurotransmitters(i.e. noradrenaline)àincrease heart rate • Parasympathetic nerves slow down heart rate by releasing a neurotransmitter (i.e. acetylcholine)àdecrease heart rate • Heart rate may be increased by chemical release of adren aline hormone into the blood (from adrenal gland) Blood vessels • Arteries o Cary blood at high pressure o Outer layer contains collagen to prevent artery from rupturing due to high pressure of blood flow • Veins o Carry blood under low pressure o Have valves to prevent blood pooling at extremities • Capillaries o Involved with material and gas exchange with surrounding body tissue o Blood pressure is relatively low o Wall is made up of a single layer to allow for easy diffusion o May contain pores to aid the transport of m aterial Cholesterol 1. What is it? • Lipid that is transported in the blood by specialized proteins 2. How does it work? • 3. What does it do? Why is it important? • Respiratory System Lungs 1. What is it? • Major respiratory organ in humans 2. How does it work? • 3. What does it do? Why is it important? • The site of gas exchange between air and the blood Respiration • Respiration is the transport of oxygen to cells where energy production takes place and involves three key process: Ventilation, Gas Exchange and Cell Respiration o Ventilation § The exchange of air between the lungs and the atmosphere; achieved by the act of breathing o Gas Exchange § The exchange of O2 and CO2 in the alveoli and the bloodstream; it occurs passively via diffusion o Cell Respiration § The release of ATP from or ganic molecules; it is greatly enhanced by the presence of oxygen (aerobic respiration) Alveoli 1. What is it? • Air sacs in the lungs 2. How does it work? • Attached to the bronchiole in the lungs • During gas exchange in the lungs, oxygen is diffused from alveoli into the blood stream and carbon dioxide is diffused from the blood into the alveoli 3. What does it do? Why is it important? • Gases diffuse between air and blood • Increase surface area to volume to ratio o Why? à spherical-‐shape improve surface exchange • The alveoli’s thin wall is made of a single layer of flattened cells so that the diffusion distance is small • Alveoli are covered by a dense network of capillaries that help to mai ntain a concentration gradient • Some cells in its lining secret fluid to allow gasses and to prevent an alveoli fro m collapsing (through cohesion) Erythropoietin (EPO) 1. What is it? • Hormone that stimulates red blood cell production 2. How does it work? • 3. What does it do? Why is it important? • Risks and benefits of using EPO (erythropoietin ) and blood transfusions to improve performance in sports o Erythropoietin (EPO)à a glycoprotein hormone produced in the kidneys that is responsible for red blood cell production (erythropoiesis) o Blood transfusionsà involve the intravenous injection of blood components (i.e. red blood cells) into the body Benefits Risks • Both increase levels of red blood cells • Too many red blood cells can produce (EPO increases production, blood damage in capillaries by increasing transfusion increases supply) blood clotting, leading to heart failure and strokes • More red blood cells means more • Risk of disease transmission or hemoglobin, allowing for greater levels possible rejection when undergoing of oxygen transport to respiring blood transfusions muscles • Improves performance and endurance • Increased blood viscosity (due to compared to athletes that do not use higher cell count) increases blood these methods pressure • Limited information on long-‐term health effects (more relevant to EPO) • Unfair advantage to athletes can result in banning or disqualification from competitions Central Nervous System Nervous System • Central Nervous System àbrain and spinal cord • Peripheral Nervous System • The nervous system is composed of cells called neurons that carry rapid electrical impuls es Neuron 1. What is it? • Specialized cells of the CNS that generate electrical signals in the form of action potentials 2. How does it work? • Dendritesàbranched extensions from the cell body of a neuron, which receive incoming information • Axonàlong extension of a neuron that conducts action potentials away from the cells body toward the axon terminal 3. What does it do? Why is it important? • Sensory neuronàcells that convey information from both inside and outside the body to the cells • Motor neuronàneuron that control the contractions of skeletal muscles How Nerves Conduct Impulses • From receptors to the CNS by sensory neurons • Within the CNS by relay neurons From the CNS to effectors by motor neurons Synaptic Transfer • The junction between two neuro ns is a synapse, it forms a physical gap between the pre -‐ and post-‐synaptic neurons • An action potential (electrical signal) cannot cross the synaptic gap, so it triggers the release of chemicals (neurotransmitters) to continue the signal • Chemical transfer across the membrane o When an action potential reaches the axon terminal, it triggers the opening of voltage-‐gated calcium channels o Calcium ions (Ca2+) diffuse into the cell and promote fusion of vesicles (containing neurotransmitters) with the plasma membra ne o The neurotransmitters are released from the axon terminal by exocytosis and across the synaptic cleft o Neurotransmitters bind to receptors on the post -‐synaptic membrane, opening ligand-‐gated channels o The combination of chemical messengers received by de ndrites determines whether the threshold for an action potential is reached o Neurotransmitter molecules released into the synapse are either recycled (by reuptake pumps) or degraded • Synaptic transmission 1. Action potential reaches axon terminal 2. Calcium channels open 3. Ca2+ causes vesicles to release neurotransmitter 4. Neurotransmitter crosses synapse 5. Neurotransmitter binds to neuroreceptors 6. Trigger signal in post-‐synaptic neuron Resting Potential • The charge difference across the membrane when a neuron is not firing, as maintained by the sodium-‐potassium pump Action Potential • The charge difference across the membrane when a neuron is firing o Depolarization § The charge from a negative resting potential to a positive action potential (caused by the opening of sodium channels) o Repolarization § The charge from a positive action potential to a negative resting potential (by opening of potassium channels) Nerve Impulses • Generation of a Resting Potential o The NA+/K+ pump maintains the electrochemical gradient of the r esting potential o It uses active transport to exchange Na+ and K+ ions across the membrane (antiport mechanism) o It expels 3 Na+ ions for every 2 K+ ions admitted o This makes the inside of the membrane relatively negative compared the outside • Transmission of an Action Potential o Na+ and K+ channels are voltage -‐gated, meaning they open and close depending on voltage o In response to a signal at a receptor or dendrite, Na+ channels open and Na+ enters the neuron passively o The influx of sodium causes the membrane potential to become positive (depolarization) o If a sufficient change in membrane potential is achieved (threshold potential), adjacent voltage-‐gated Na+ channels open o This generate a wave of depolarization (action potential) that spreads down the axon o The change in membrane potential also activates voltage -‐gated K+ channels, causing potassium to exit the neuron passively o The efflux of potassium causes the membrane potential to become negative again (repolarization) o Before a neuron can re -‐fire, the original distribution of ions (Na+ out, K+ in) must be re-‐established by the Na+/K+ pump o Then inability to propagate another action potential during this time (refractory period) ensures nerve impulses only travel in one direction • Stages of an action potential 1. Resting potentialàNa+/K+ pump 2. Depolarizationàvoltage-‐gated Na+ channel 3. Repolarizationàvoltage-‐gated K+ channel 4. Resting potentialàNa+/K+ pump Glial cell 1. What is it? • Supporting cells of the nervous system 2. How does it work? • 3. What does it do? Why is it important? • Maintain constant environment for axons Neurotransmitter 1. What is it? • Chemical signaling molecule released by a neuron to transmit a signal to a neighboring cell 2. How does it work? • Dopamineàneurotransmitter that is involved in conveying a sense of pleasure in the brain 3. What does it do? Why is it important? • Electrochemical gradient 1. What is it? • Charge gradient 2. How does it work? • Whenever there is a positive charge it can work • More positive outside than inside 3. What does it do? Why is it important? • The Brain/Mental Health Parts of the brain: Part of the Brain Function Location Cerebellum Part of the brain that processes sensory information and is involved in movement, coordination and balance Brain Stem Part of the brain that is closest Midbrain to the spinal cord and which controls vital functions: Heart rate, breathing and blood pressure Diencephalon Brain region located between brain stem and cerebrum that includes thalamus and hypothalamus and regulates homeostatic functions: Body temperature, hunger, thirst, and sex drive Cerebrum Region of the brain that controls intelligence, learning, perception and emotion ; integration Cerebral Cortex Outer layer of the cerebrum; Frontal involved in many advanced brain functions, “the boss” Hippocampus Subregion of brain involved in learning and memory Amygdala Subregion of brain that processes emotions, especially anxiety and is the seat of emotional memories Thalamus Sorts data Occipital • Function o Eye sight Temporal • Function o Sensesàsmell, taste, touch Right Hemisphere • Function o Face recognition Left Hemisphere • Function o Mathematical o Linearly processes o language Basal ganglia • Function o Motor control o Problems with basal ganglia àParkinson’s disease Mental Health Disorder Symptoms Genetic Epigenetics Neurotransmitters Location Component Effected Schizophrenia Delusions Many genes Prenatal Dopamine-‐ excess Prefrontal Hallucinations 10% family stress of dopamine cortex-‐ Disorganized members Physical, Glutamate excess-‐ planning, etc. thinking or 50% for mental or hippocampus Basal ganglia-‐ speech identical twins sexual where abuse antipsych Drug use drugs target dopamine Bipolar Dramatic Multiple genes Trauma or a Serotonin Prefrontal mood swings involved traumatic Dopamine cortex is less Mania (high 20-‐25% if event, or norepinephrine active energy & parents other impulsive Serotonin & experiences norepinephrine (the reward Alcohol or system) too drug use high or too low Depression Hopelessness Serotonin Stressful life Serotonin Amygdala-‐ Loss of transporter event, (happiness) emotion interest gene (SSRIs) death, Dopamine (reward center Sadness & Very heritable social system) Thalamus-‐ anxiety Very likely in isolation sensory & Loss of families Relationship recovery energy 100% in conflict Hippocampus-‐ Changes in identical twins Health memory & appetite issues chronic stress Autism Trouble Over 200 genes Inutero Serotonin-‐ non interacting affected difficulty synthesized Delayed A spectrum normally development Very heritable, Glutamic Inappropriate up to 100% imbalance language use Conclusionà mental healthà largely genetic Schizophreniaà geneticàenvironment determines if the genes are expressed Reproductive System Hormones in the menstrual cycle • FSH and LH are released from the anterior pituitary and act on ovaries • Estrogen and progesterone are released from the ovaries and act on the uterus (endometrium) Hormone Function FSH • Stimulates follicle growth • Stimulates estrogen secretion (from follicles) Estrogen • Development of endometrium • Stimulate LH secretion (follicular phase) • Inhibit LH and FSH secretion (luteal phase) LH • Surge causes ovulation • Development of corpus luteum • Stimulates progesterone secretion Progesterone • Thickening of endometrium • Inhibits LH and FSH (luteal phase) Summary of menstrual cycle 1. Follicular phase • FSH stimulates growth of several follicles • Dominant follicle secrets estrogen • Estrogen stops other follicle’ growth (and FSH) • Estrogen stimulates endometrial development 2. Ovulation • A surge in LH causes o vulation (egg release) • Rupturing of follicle creates an corpus luteum 3. Luteal phase • Corpus luteum secrets estrogen/progesterone • Progesterone stimulates endometrial growth • Estrogen and progesterone inhibit FSH and LH • Corpus luteum degrades over time • Progesterone levels drop • Endometrium is sloughed away (menstruation) Testosterone in males • Pre-‐natal development of male genitalia • Development of secondary sex characteristics • Maintenance of sex drive In Vitro Fertilization • In vitro fertilization refers to fertilization outside of the body o Stop menstrual cycle (with drugs) o Hormone treatment to develop follicles o Extract multiple eggs from ovaries o Sperm selection (capacitation) o Fertilization occurs in glass dish o Implantation of embryos into uterus o Test for pregnancy • Advantages o Allows infertile couples to have children o Genetic screening of embryos could reduce occurrence of genetic diseases o Spare embryos can be stored for future attempts or used in stem cell research • Disadvantages o IVF is expensive and might not be equally accessible to all o Success rate is low and hence may be stressful for couples o It could lead to eugenics (gender choices) o Often leads to m
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