Chapter 38 Homeostasis & Thermoregulation PDF

# Chapter 38 Homeostasis & Thermoregulation ## Muticellular Animals - **Advantages** - Access larger prey/resources - Resist environmental forces - **Disadvantages** ## 4 Tissues - Cells with same characteristics or specializations - **Connective** - epithelial tissue - tightly connected...

# Chapter 38 Homeostasis & Thermoregulation ## Muticellular Animals - **Advantages** - Access larger prey/resources - Resist environmental forces - **Disadvantages** ## 4 Tissues - Cells with same characteristics or specializations - **Connective** - epithelial tissue - tightly connected cells - muscle tissue - nervous tissue - **epithelial tissue** - tightly connected cells - Covers body surfaces and lines hollow organs - functions include protection, secretion, and absorption - **Muscle tissue** - generates force and cause movement - contains contractile proteins actin & myosin - **Cardiac muscle cell** - Contracts heart pumping blood - **skeletal muscle cell** - responsible for movement & breathing - **Smooth muscle cell** - Lines gut, bladder - **Connective Tissue** - often dispersed in an extra cellular matrix (plasma) - Functions include structural support, stored energy, carrying respiratory - Bones, Blood cells, ligaments / tendons, & adipose tissue. - **Nervous Tissue** - **Neurons** - Communicate information - Sensory neurons: Collect information - **Glial cells**: Support neurons ## Organs - Consist of epithelium & 7 1 other tissue ## Physiological System Organization - Cells → Tissues → organs → Organ Systems (group of organs that work together to carry out functions) ## Homeostasis - Maintenance of a narrow range of physical and biochemical conditions needed by life to survive - As multicellular organisms evolved, cells became enclosed in an internal fluid environment - Fluid provided for cells needs, allowing cells to specialize - As organisms became larger & more complex, advanced systems evolved to maintain homeostasis - **Homeostasis** - Extracellular fluid surrounds cells buffering them from changes and allowing for exchange. - **Homeostasis** - In humans, extracellular fluid surrounds cells - Absorbs wastes & delivers nutrients - buffers tissue from fluctuations in conditions - Your body is -60% water: 2/3 in cells and 1/3 outside cells - **Homeostasis**; - Physiological systems regulate homeostasis allowing multicellular animals to evolve larger, more complex forms & to occupy many different environments ## Maintaining Homeostasis - **Regulatory systems**: gather information & control activities of body - Examples: nervous & endocrine system ## Maintaining Homeostasis - **Set point**: desired reference level (temp., plt, etc..) for homeostasis. 7.35-7.45 normal blood plt range. - **Feedback information** from sensors on current level - **Ennor signal**: difference between the two levels ## Maintaining Homeostasis - **Effectors**: controlled systems that effect changes as directed by regulatory systems. - Example: Blood pressure; muscles in heart & blood vessels are effectors ## Maintaining Homeostasis - **Negative feedback**: Information used to counteract cause of error signal; Tells effectors to reduce / reverse processes to set point. - Most common type of feedback. ## Case Study: Blood Sugar - How does your body regulate blood sugar levels? ## Case Study: Blood Sugar - What happens when this feedback system malfunctions? - Diabetes. ## Case Study: Blood Sugar - Diabetes - Type 2: difficulty responding to insulin (resistance) ## Maintaining Homeostasis - **Positive feedback**. tells a regulatory system to amplify a response (no set point) - **Positive Feedback Loop** - Birth ## Maintaining Homeostasis - **Feedforward information**: signals to change set point in anticipation of changing (negative feedback only) ## Learning Objectives (Ch. 38) ## Influence of Temperature - Most cells only function between 0-40°C - Ice crystals cause damage when tissue freezes ## Influence of Temperature - Reaction rates ↑ with temp. - ↑ temps, denature proteins, but heat shock proteins can provide some protection ## Influence of Temperature - **Acclimatization** - Adjusting to long-term changes - Different enzymes (isozymes) in winter vs. summer - **Changing insulation**: storing fat, gaining / losing fur - **Modifying physiological Responses** ## Thermal Classification - What types of animals do you see? ## Thermal Classification - **Ectotherms** - Body temp. determined by external heat sources. - Reptiles, amphibians, invertebrates, and many fish - **Endotherms** - Body temp. regulated by metabolism and active mechanisms - mammals, birds, and some fish ## Thermal Classification - **Heterotherms** - Switch between endo-and ecto-thermy between night vs, day or even for longer penods (hibernation) - bat squirrels that?? ## Why do Endotherms Produce more Heat? - Endotherm cell membranes are more leaky to ions (less energy efficient) - Expend more energy than ectotherms to maintain concentration gradients produce more heat - Results in greater metabolic rate and energy needs. ## Benefits of Endothermy - Endotherms can occupy colder regions and remain active during periods unavailable to ectotherms. - Disadvantages: greater energy requirements due to metabolic heat production ## Leaming Objective (Ch. 38) ## Ectotherms vs. Endotherms - **Ectotherm**: Body temp, varies with surrounding temp - **Endotherm Body temp. remains constant as surrounding temp. varies.** ## Metabolic Rate and Temperature - **Ectotherm**: resting metabolic rate decreases with temp. drop - **Endotherm**: resting metabolic rate increases as temp. drops below threshold to generate additional metabolic heat. Graph will be on test ## Behavioral Thermoregulation - Primary method for ectotherms, but also used by endotherms - Move to microhabitats for heating or cooling - Orient body to increase / decrease sun exposure ## Behavioral Thermoregulation - Nest construction and huddling used to retain heat ## +4 ways heat lost and gained 1. Conduction 2. Convection 3. Radiation. 4. Evaporation ## Heat Energy Budget - Balance of heat production and exchange - for maintaining constant temp. Heat = Heat, out or - (metabolism & Rabsorbed) = (Rout + convection + conduction & evaporation) ## R= Radiation - Heat loss is dependent on animal surface temperature which can be altered by changing blood flow to skin. ## Thermoregulation and Blood Flow - Vaso-constriction and dilation along with heart rate alters blood flow to skin and limbs changing heat loss rate. - used by both ecto-endo therms ## Ectothermic marine iguana: - alternate between feeling in cold water and basking on hot rocks. ## Vary heart rate and blood flow to skin to maintain body temp. under different conditions. ## Thermoregulation and Blood Flow - Heat loss via vasodilation aided by structures with less insulation and increased blood vessel density (radicators) ## Countercurrent Heat Exchange - Structure that allows exchange of heat between warm and cold blood via conduction between nearby arteries and veins - Reduces heat loss by keeping warmth in body core - Common in polar and aquatic species such as hot fish. ## Ectothermic Heat Production - A Few ectotherms can increase temp. with metabolic heat - Honey bees: Generate heat as a group ## Endothermic Thermoregulation - Endotherms use negative Feedback mechanisms to regulate body temp. - What mechanisms are used for heat loss or production? ## Metabolic Rate - Metabolic rate (MR): Measured us O2 Consumption or CO2 production - Index of an animal's heat production - Thermoneutral zone (TNZ): range of temp, where extra energy is not needed to thermoregulate (lowest MR) - Basal metabolic rate (BMR): MR when animal is at rest in TNZ. ## Body Size & Metabolic Rate - Larger animals usually have greater total BMR than smaller ones - BMR does not linearly vary with body size: Why elephant 100,000 times bigger than mouse, but BMR only 7,000 times greater. - Larger animals have smaller surface area to volume ratio - Harder to dissipate heat as size increases so lower than predicted BMR may prevent overheating - Larger animals have greater proportion of support tissue (skin, bone, etc) than that are less metabolically active contributing to lower than predicted BMR ## How do Endotherms Thermoregulate: - BMR is stable within thermoneutral zone. - Lower and upper critical temp. mark bounds where more energy via active mechanisms is needed to maintain temp - Within thermoneutral zone, temp. is maintained via passive mechanisms requiring little energy - Behavioral strategies - Fluffing insulation - Altering blood flow to skin ## How do Endotherms Keep warm? - Below lower ontical temp, metabolic heat production. increases - Shivering: muscles contractions - other body movements - Non shivering heat production in specialized adipose tissue (brown) used by many mammals. - Other adaptations reduce heat loss: - Smaller thicker appendages & round bodies (reduces surface area to volume ratio) - Insulation: more fat, fur, feathers, & oil secretions - Countercument heat exchangers. ## How do Endotherms Keep Cool? - Above upper critical temp. active mechanisms include - Sweating & panting - Eraporative cooling removes heat - But generates metabolic heat & water, & energy loss. - Blue = cool ## Think-Pair-Share - Explain the general patterns in metabolic rate of endothermic ground squirrels as temperature Changes. When does it increase or remain flat?. - Explain why metabolic rate changes at different temperatures. What physiological mechanisms drive these changes in MR? ## Thermoregulatory System - In mammals, the hypothalamus integrates external and internal info. & directs thermal effectors to regulate temp. via negative feedback - Located at base of brain. ## Mammalian Thermostat - Hypothalamus: varies set points of heat production & other activities depending on internal a surface temperature & biological cycles - Feed Forward info. from sensors can lead to high lover set points for heat production - set point lower during hot temps, & sleep. ## Regulated Hypothermia - Deliberate lowering of body temperature below normal - Reduces energy expenditures to survie. ## periods of cold & food scarcity - Daily torpor by hummingbirds & bats - Body temp. & MR drop during inactivity. - Reduces energy expenditures to survive periods of cold and food scarcity - Longer hibernation by squirrels - Body temp. & MR drop for days/ weeks. ## Questions 1. Explain what heat loss mechanisms contribute to Joel's feelings of coldness. 2. What physiolohic responses will occur to help Joel maintain a norma body temperature? 3. What mechanisms and / or structures are responsible for inital initiating and controlling these. physiologic responses 4. Adipose tissue/brown fat - Joel ## Turn in 1.00pm before class. ## Animal Chemical Signals - Allow cell to cell communication - Chemical signal binds to target cell receptors - Control Body's - Growth and development - Immune, endocrine, & nervous systems ## Animal Chemical Signals - Applications - Health - Sports - Conservation ## Hormones (endocrinol) - Produced by endocrine cells - Enter blood stream - Target cells Far from release site ## Paracrines - Affect nearby cells - Usually released in small quantities or broken down by enzymes quickly. - Do not enter bloodstream ## Autocrines - Influence cell that secretes them - Provide negative feedback loop for their own secretion. - may also be a hormone or paracrine ## Endocrines - Endochine cells can exist as - Single cells in a tissue: Ex. Cells in digestive tract wall - Endocrine glands: aggregations of cells. ## Neurotransmitters - Neurohormones: Chemical signal released by neurons that acts like a hormone - Selective Permeability: - Hydrophobic interior of cell membrane prevents large, polar or charged molecules from easily crossing - EX.Cl, proteins, etc. - Small, non-polar molecules diffuse easily. ## Hormone Chemical Groups - Peptide (z 2 amino acids) & protein (≥ 50D) - most common hormone - water soluble: easily transported in blood, cannot easily pass through cell membranes. - Exocytosis release - target receptors on cell surfaces - Majority of hormones - Ex. Insulin & Growth hormone. ## Hormone Chemical Groups - Steroids - Lipid soluble (nonpolar): can pass through cell membrane - Transported by camer molecules in blood - Intracellular receptors at target cell - Estrogen and testosterone - Amine - made from one amino acid tyrosine (simple molecules) - Either lipid-or water-soluble depending on structure - Various release a receptor mechanisms depending on structure - EX. Epinephrine & dopamine ## Hormone Actions - Water-soluble hormones bind to receptors on cell membrane composed of large glycoprotein Complexes that extend into cytoplasm - Secondary messengers then activate a cascade of intracellular events leading to cell response De gene expression. - Lupid, soluble hormones diffuse into cells, bind to receptors, & Initiate cell response. ## Response to Hormones - Hormones will bind to any specific receptor it encounters, but response differs among different cell types - Slow compared to electrical signals, but can reach all cells within body. ## Evolution of Hormones - Likely important to evolution of multicelluanty - Ex. Slime mold formation: individual amuebae form an aggregate during food scarcity. CAMP chemical signal coordinates individual cells. ## Evolution of Hor mones - Same chemical compounds found in many taxonomic groups, but functions diff indicating that signal structure is highly conserved. ## Endocrine System - Endocrine system is composed of gland's &, embedded tissues that direct sustained body responses. - Nervous system is better at generating complex rapid responses. - Hypothalamus & Pituitary ## Nervous & endocrine systems work together to coordinate, many behavioral a physiological responses. - Pituitar gland. is communication link between both systems, attached to hypothalamus ## Hypothalamus? Pituitary - Posterior pituitary releases hormones created by hypothalamus: derived from neural tissue. - Anterior pituitary creates & releases hormones as directed by hypothalamus (derived from epithelial tissue. ## Posterior Pituitary - Axons of neurons in hypothalamus extend into posterior pituitary. - Electrical signals enter hypothalamus triggering neurons to produce neurohormones - Neurohormones diffuse into capillaries of posterior pituitary entering blood stream - Neurohormones travel to receptors in target tissue that effects response - APH (vasopressh): water conservation & blood pressure - Oxytocin: birth and lactation. ## Anterior Pituitary - Hypothalamo neurons do not extend into anterior. pitultury - Electrical signals enter hypothalamusiutig triggering a release of news hormones: (releasing hormones) - Travel through portal blood vessels to anterior pituitary - Neurohormones trigger release of hormones in anterior pituitary - Hormones travel to receptors in target tissue, usually other endocrine glands controlling body responses (tropica hormones) - LH Lutenizing hormone - FSH: Follicle stimulating hormone - tot: Thyroid-stimulating hormone - ACTH- Adrenocorticotropin hormone - GH: Growth Hormone - Tropic, hormones cause additional hormone release in target glands - EX: testosterone - Hormone secretion is controlled by negative feedback loops through multiple pathways. ## Sex Steroids - Androgens (male steroid hormones). - Direct sexual development as embryo. - At 7 weeks, testes produced androgens (genes on Y chromosome) that cause male Features to develop - If androgens fail to be released then female development occurs. - Gonadotropins (LIt? FSH) - At puberty, sex steroid production increases- resulting in both sexes developing secondary Sexual characteristics - Hypothalamus become less sensitive to negative Feedback at puberty increasing hormone production. ## Case Study: Thyroid - Hypothalamus secretes thyrotropin-releasing hormone. (THR) triggering production of thyroid-stimulating hormone (ISH) in antenor pituitary.. - TSH activates thyroid hormone production in thyroid ## In thyroid, epithelial cells that form follicles produice thyroid hormone's - Regulates cell energy metabolism - Calcitonin produced by other thyroid Cells: regulate's blood calcium ## Thyroid hormone also called thyroxine:. - derived from tyrosine & contains iodine - Ty low actruity form, secreted at 10 times rate of T3 - T3: more active form - Target cells can control effects by converting between forms. ## Cold exposure stimulates thyroxine production & conversion of ty to To causing transcription of genes related to metabolism & increasing metabolic rate - Negative. Feedback loop. wal acts on hypothalamus (TRH) & pituitary (TSH) to prevent over/under production of thyroxine. ## Thyroid disease: most common hormonal problem. - Golter; enlarge thyroid, ## Hyperthyroidism - Graves' Disease - Autoimmune disease produces. antibudresu that bind to TSH receptor in thyroid. - Causes uncontrolled production of thyroxine; thyroid can grow bigger - Negative feedback leads to lower TRH & TSH. - Causes high metabolic rate, feeling hot, & bulging eyebans - Treated with drugs, radioactive iodine or Surgery. ## Hypothyroidism - Too little thyroxine produced - leads to high levels of TRH & TSH - thyroid can grow bigger - Causes tow metabolic rate, intolerance to cold, & sluggishness - Can result from lack of dietary iodide or autoimmune disorder that attacks thyroid (tashimoto's. disease) ## Asexual vs. Sexual Reproduction - Asexual: I parent produces genetically identical offspring to itself. - Sexual: 2 parents give rise to offspring that have unique combinations of genes inherited from each. ## Asexual reproduction Benefits - Energy efficient. no time/ energy wasted on mating - Faster reproduction: All individuals produce offspring - preserves good allele combinations - Can rapidly colonize new areas ## Asexual Reproduction - Less genetic diversity is produced - Disadvantage if environment is variable. ofeping with encounter diferent conditions. from purent ## Asexual Reproduction - Budding: outgrowth creates new individual. - Regeneration: regrowth of lost tissue ## Asexual Reproduction - Parthenogenesis: develop from unfertilized eggs - often still linked with sexual reproduction or behavior. ## Sexual Reproduction - Disadvantages: Greater costs of time & energy, disrupts potentially good allele combinations, & lover population growth - Advantages: Produces highy variable offspring, some may be better aclapted to current. ehuronment conditions. ## Sexual Reproduction - Some organisms switch between Sexual and asexual reproduction depending on environmental conditions. - EX. Aphids: Asexual in summer, sexual in winter. ## Dawadah ## Sexual Reproduction - Two life stages - Diploid (2n): Adult - Haploid (n): Gametes - Three main step - Gametogenesis ## Gametogenesis - Occurs in gonads wa meiosis: primary sex organs - male: testes produce sperm - Females: ovaries produce OVA(egg) ## Spermatogenesis: - 4 sperm are produced via meiosis - Sperm are produced throughout male lifespan - Cytoplasmic bridge allows sharing of gene products on X chromosome.. ## Oogenesis - Only I ovum produced - Primary cocyte develops & remains in prophase I until needed (puberty until menopause) - Second mejotic division not completed until after fertilnation. - All primary oocytes created as embryo ## Fertilization - Haploid sperm & egg fuse to form diploid Zygote (2n) - Proteins on sperm head digest egg's protective layers, next steps include. - sperm & egg must chemically recognize each other. - Sperm & egg plasma membranes fuse - Egg prevents further sperm entry.. ## Fertilization - Next, egg completes meiosis e becomes metabolically active - Sperm a, egg nudei then fuse. ## Dubingroogenesis tour cells - External Fertilization (Outside Body) - Aquatic species primanly, produce lots of gametes - Release of gametes synchronized Cues include weather, day, length, & mutual simulation ## Internal Fertilization (Within Budy) - all mammals, birds, & reptiles. - Some invertebrates, amphibians, & fish - Evolution of genitalia to deliver & accept Sperme ## Direct via Copulation. joining of genitalia, "Key fits the lock" ## Indirect via sperm package in some species - Allows for evolution of greater parental care because eggs remain in female longer. ## Amniote Egg - Nounshing yolk with additional membrane & shell. - Prevents desiccation while allowing for gas exchange. - Contains water & food for embryo - found in reptiles (including birds) & mammals ## Egg care - Oviparous: Lays eggs, embryos develops Outside mother. - Many insects &, reptiles (including birds) - Viviparous: embryo develops inside mother - Common in many vertebrates & all mammals except monotremus. - fertilization occurs in the ovat ducts. Duducts, ## Vivi parous - in placental mammals, embryos housed in utens - Placenta exchanges nutrients & wastes between retus a mother. ## Human Male Anatomy