HUBS LECTURES 1-16, Homeostasis & Anatomy

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1 HUBS LECTURES 1-16, Homeostasis & Anatomy Homeostasis L2 Amoeba. Lack of control of its situation, as is a single cell organism. However, as cells begin to cooperate they begin to gain the ability to control the situation. Environmental factor; *Nutrients *Toxins, including own waste *Temperature *Predators Human Cells = Specialised, cooperative Amoeba. Cell membrane, active part of cell, controls transfer of substances between intra and extracellular fluid, control of nutrients etc. Multicellular is a solution to environmental factors, supplying cells with a stable environment inside the body. History -Claude Bernard ( ), recognised importance of the internal environment ie. Extracellular fluid. ECF. Homeostasis of ECF allows organism as a whole to explore a wide range of environments, whilst controlling the body. Role of organs is to perform homeostasis. Humans; Integumentry System; separates external from internal ie. Skin Nervous System; senses changes in system etc. Digestive System; removes nutrients from food etc. and removes waste from body Respiratory System; exchanges CO2 for O2 Muscle System; powers and directs skeleton Skeletal System; stores materials and supports Endocrine System; regulates internal system by secreting hormones Immune System; defends internal environment Lymphatic; drains excess fluid from tissues, cleans it, returns it to blood Origins of Ill-Health and a Health Professionals Role

2 Infection Organ System Failure Failure of Homeostasis Recovery Treatment by removing source of problem or allowing time for homeostasis to occur. Treatment by taking over homeostatic control either; Temporarily, whilst body heals eg. Coma OR Permanently, control homeostasis eg. Diabetes Treatment by repairing or replacing defective tissues. Important concepts of homeostasis; - Controlled variable ; the variable that the system tries to keep stable ie. Speed of a car - Set-Point variable ; target variable ie. Speed limit - Reference range of variable ; variable controlled within limits of set range ie. Speed limits - Variation of variable ; different people have different levels ie. Different cars, speeds Reference range is obtained by measurements from healthy people. Values within two standard deviations of the mean. Ie. 95% of healthy individuals fall within range. Genetic factors determine different set points in different individuals. Within individuals, variables fluctuate around the set point in response to normal activity (within range) eg. Your core temperature drops at night. These may change due to biological rhythms. Clinical implications of variability; When interpreting lab tests, we must know the history, sex, height, weight, context etc. before we can make a judgement. Eg. Blood glucose tests must be done after a period of fasting so food consumed doesn t affect the test results. Principles of Homeostasis L3 *Describing negative feedback and feed-forward control systems to operate homeostasis *Control systems of homeostasis; - Achieved by a combination of feedback and feed-forward control systems - Most important control system feedback is negative feedback, whereas positive feedback isn t really a control system ; used to magnify response ie. Blood clotting *Basic principles of physiological control are similar to those in engineering eg. House temp and body core temp!! Communication Systems

3 Intergration centre; same cells Communication pathways; nerve axons Effector; muscles shivering to produce warmth, regulate warmth Feedback control is ubiquitous in physiology ie. It is everywhere Heart/snake blood pressure Diabetes mellitus blood Ph Exercise CO2 blood CO2 Brain isn t always the integrator, in some cases other organs do integrate the values. CONTROLLED VARIABLE; the variable being controlled ie. Core temp SENSOR; the thing sensing change in variable ie. Hypothalamus INTERGRATER; compares actual value (AV) to set-point value (SPV) to assess what changes need implicated EFFECTOR; implicates the changes ie. Shivering muscles to warm up cold person Positive Feedback - Change in variable causes the variable to change even more, in the same direction - Unstable feedback, causes continual increase rather than just returning AV to SPV - Used in physiological control systems for specific purposes - Must be carefully controlled to prevent inappropriate activation, could be dangerous to being - Works towards specific endpoint Eg. Blood clotting, uterine contractive during birth Feed-forward Control Action takes place in advance to prevent or minimise change Involves prediction Not precise *Physiological Anticipatory *Behavioural Innate Biorhythm, entrained Learned

4 Homeostasis in Action L4 POWERPOINT has case points for reference. Diabetes Mellitus; a failure of homeostasis Importance of blood glucose; Brain can only use glucose for energy Too much glucose in blood can cause tissue damage however Supply of glucose from meals is intermittent Therefore the level of glucose in blood must be regulated to ensure safe levels of glucose are present. After meals have passed glucose must still be in bloodstream for brain to function, otherwise serious problems may occur Diabetes mellitus is still unable to be cured, as it has undiscovered mechanisms contributing to the control. Treatment of type 1 diabetes mellitus involves a homeostatic take over ie. We control the homeostasis. Control by measurement and injection has more time delay than natural control and insulin administered at intervals, not continuously like normal control. Each insulin dose is calculated based on current blood glucose level and predicted food intake. If a meal is unexpectedly missed, insulin level may be too high, blood glucose too low, and the person may faint. Hypothermia; core body temperature Why is core body temperature so important? At high temperature proteins start to denature ie. Breakdown At lower temperatures, chemical reactions slow down preventing cell function. Nerve cells are particularly sensitive so control functions and processes etc. are affected first This can lead to an escalation of heat loss, as positive feedback starts, rapidly causing death Temperature regulation Sources of heat; - Metabolism, especially muscle food Routes of heat loss; - Radiation - Evaporation/conduction/convection

5 ! Regulated by; - Controlling blood flow to skin (increase/decrease loss from radiation/conduction/ convection) - Sweating (evaporative loss) - Muscle activity (extra heat from shivering) Feed-forward control of core body temp Behavioural/cultural/technologic; Keeping fire and other sources of heat Clothing Shelter Weather forecasting End of Homeostasis Structure of Body L6 Skeleton; - Support - Movement - Protection - Storage - Red blood cell formation Structure of bones; There are two types of tissue Compact bone shaft of long bones, important for strength and resisting tension Cellulous bone sheets of bone tissue arranged in honeycomb formation (spongy bones). Resisting compression and helping for shock absorption, head of bones. Bone classes; based on shape, not size Long bones longer than they are wide, have extremities or epiphyses (heads) at ends, have a shaft or diaphysis, used as levers for movement Short bones nearly equal in width and length, weight bearing, mostly cellulous bone

6 Pectorial girdle (shoulder) for arm = Clavicle (acts as a strut) + scapula Pelvic girdle = Hip bones (2) and sacrum, designed for stability, due to weight bearing - Hand consists of; Carpals (8) Metacarpals (5) Phalanges (3) - Foot consists of; Tarsals (7) Metatarsals (5) Phalanges (3) Microscopic Structure and Bone Tissue L7 Bone tissue; - Has cells living within extracellular matrix - Bones grow from cartilidgenous model - It remodels and changes its shape slightly in response to external forces - Repairs itself: after injury, cells respond to fracture and repair it - It is a connective tissue, holds/separates structures, where support is needed has a lot of extracellular matrix and not a lot of cells - Has two cellular components: Organic (33% of matrix) Collagen (protein) made of fibres, embedded in ground substance (protoglycans), tensile strength to resist tension Inorganic (67% of matrix) Made up of hydroxyapatite (mineral salts), these are what give bones their hardness, resists compression Cellular component; 1. Osteoblasts: build the ECM (extracellular matrix) and create new bone tissue 2. Osteocytes: mature osteoblasts, important for signalling to other bone cells for when remodelling needs to occur (these are trapped in the ECM) 3. Osteoclasts: break down/destruction of ECM, part of turnover of bone Gross structure of bones; Compact Cancellous

7 Compact bone; Gross level Outer surface, foramina (holes) provide entranceway into bone for blood vessels to provide nutrience Microscopic level Lamella = sheets of bone tissue, the bone forms cylinders which longitudinally run down the shaft of the bone, collagen fibres aligned/orientated in different directions to resist tension/forces, osteons - made up of many components, many sheets of lamella, provides a pathway for nutrients to pass through. This H2O and nutrients comes through the central canal in osteon, lucanae (lake), canalicoli (channels that run between lakes), 1000 s of osteons in bone Cancellous bone; Trabeculae, sheets of lamella bone (sheets of ECM), marrow fills the cavities - osteocytes housed in lacuna on surface of trabeculae Bone Tissue L8 Organic collagen, resists tension Inorganic mineral salts resist compression 3 cells, osteoblasts, osteocytes, osteoclasts Osteon is the functional unit of compact bone responsible for bone maintenance. Components of osteon are; 1. Lamellae 2. Central canal 3. Lacuna 4. Canaliculi Bone growth; Cartilage perform Ossification, turning cartilage into bone. This begins in the diaphysis (shaft). This is known as the primary centre of ossification. Secondary centre of ossification is at the epiphysis (head) or at major muscle site attachment Growth plates made of cartilage remain as cartilage as the bone continues to grow Growth in length, growth plate Growth in width, periosteum (osteoblasts), endosteum (osteoclasts) removing bone on the inside Osteocytes signal when the osteoblasts or osteoclasts are needed Osteoporosis;

8 Bone deficiency disease in which the osteoclasts overtake the osteoblasts, weakening bone structure. Primarily result of ageing, women are more susceptible, lack of exercise, nutritional factors, we develop peak bone mass in our 20 s Bone fractures; there are four stages of healing for bone fractures *Stage 1 Haemotoma, capillaries invade site to help with blood clot *Stage 2 Fibroblasts move into fracture, some differentiate into cartilage cells called chondroblasts, these cartilage cells form a soft callus Fibrocartiliginous *Stage 3 Osteoblasts change soft callus into bony callus *Stage 4 Remodelling Pseudoarthrosis happens if joint isn t splinted properly ie. Is allowed to move There are 3 types of fractures we re expected to know;! 1. Simple, closed fracture 2. Open, compound fracture (complete, possible break of skin) 3. Greenstick fracture (splintering) Soft Tissues L9 A joint is to hold bones together. Where they meet the bones articulate, also allowing for shock absorption and movement (facilitate free or resist) Cartilage; 2 types Hyaline: also known as articular, found at free moving joints ie. It covers where the bones meet, also found at the growth plates Fibrocartilage: found in the knee (meniscus) Composition; - Collagen fibres found in ground substance - Chrondrocytes produce this - Cartilage doesn t have blood vessels running through it, nutrients have to diffuse through cells (movement helps this diffusion) Structure; Hyaline: collagen fibres form a non-visible network, high water content resists compression, amorphous Fibrocartilage: bundles of collagen fibres, orientation of fibres aligns with stresses, resists compression and tension Function;