topic 6 chapter review

(6.1) digestion & absorption, role of enzymes

(6.1) digestion & absorption, role of enzymes

ingestion - food taken in through the mouth as large particles. digestion - broken down by enzymes in saliva, excreted by salivary glands, in the stomach and small intestine. absorption - broken down products absorb across the gut wall. egestion - unwanted material is eliminated by excretion. food is broken down mechanically (chewing) or chemically (enzymes). each digestive enzyme hydrolyses a different macromolecule (amylase - carbohydrates, protease - proteins, lipase - lipids). amylase hydrolyses starch into maltose, maltase hydrolyses maltose into glucose for absorption and usage. intestinal villi increase the SA of the small intestine for more efficient rate of absorption. amylase produced by salivary glands denatures in the stomach so pancreas secrete more. liver produces bile, metabolises macromolecules, stores iron, copper, vitamins.

(6.2) describe the structure of the heart and the blood vessels

the heart is a four chambered organ, composed of the right and left atria and ventricles, vena cava, pulmonary artery, aorta. it has a pulmonary (heart to lung) circuit and a systemic (heart to other organs) one. the left side has thicker muscles to pump oxygenated blood to the entire body. SAN is the pacemaker which initiates the cardiac cycle by contracting the atria. AVN delays the signal for bundle of His to contract the ventricles. blood vessels consist of veins, arteries, capillaries. arteries carry blood away from the hart to capillaries, narrower lumen, thicker wall, and higher pressure to pump. veins collect blood from capillaries and bring it back to the heart, wider lumen, tinner wall, lower pressure, and valves to prevent backflow. capillaries - exchange O2 and nutrients in the blood for CO2 and waste from the cells, thin & low pressure for exchange.

(6.3) non-specific and specific diseases, the role of antibiotics in treating disease

non-specific: 1st & 2nd. 1st: the skin provides a physical barrier due to low pH and chemical secretions (eg. sebum). tears and mucus also wash away bacteria. 2nd: a range of defence mechanisms that target any pathogen which crosses the physical barrier; white blood cells most involved. also includes the complement system - plasma proteins bind pathogens and induce an inflammatory response. specific (3rd): specialised lymphocytes (B & T cells) initiate specific responses, including production of specific antibodies to each type of antigen (foreign substance) and memory cells. antibiotics act against bacterial infections by either killing the bacteria (bactericidal) or preventing them from growing (bacteriostatic). only bacteria are targeted due to their specific metabolic pathways. bacteria may develop antibiotic resistance, therefore, it is best to use several drugs and at higher concentrations, otherwise it may get very difficult to treat and become life-threatening.

(6.4) mechanisms and role of breathing, how lung disease affects gas exchange

gas exhange - oxygen is acquired, needed for cellular respiration, and CO2 is removed by diffusion. gas exchange surfaces have thin membranes and large SA for maximum diffusion rates. the general region of gas exchange is alveoli. breathing is achieved by; inhalation - external intercostal muscles contract, diaphragm contracts and moves down, thoracic volume increases, air flows in; exhalation - external intercostal muscles relax, diaphragm relaxes and moves up (quiet breathing) or abdominal muscles contract (forced breathing), thoracic volume decreases, air flows out. lung disease causes shortness of breath and higher risk of heart disease. alveoli lose their elasticity/become damaged.

(6.5) how are electrical impulses transmitted in and between neurons?

sensory input from stimuli is received by receptors, impulses travel via sensory neurons to the CNS, where input is processed and an appropriate response is produced. the response travels via motor neurons to effector cells. nervous control is rapid and short-lived, impulse is received by dendrites and travels through the axon to the axon terminals as action potentials. larger axon diameter and myelin sheaths speed up transmission. neurons have a slight negative charge, known as the resting state/potential. the action potential begins with depolarisation - Na+ channel opens and there is a rapid influx of Na+ ions. then repolarisation - Na+ channel closes, K+ channel opens and K+ ions move out. then it returns to the resting state again after both channels close.

(6.6) the role of hormones in homeostasis and repoduction.

endocrine cells produce hormones and secrete them into the bloodstream which act on target cells. the stimulus for hormone production may be: humoral - a blood component, hormonal - another hormone (e.g. insulin of glucagon), or neural - a nerve impulse. homeostasis is the process by which the extreme fluctuations of internal conditions are limited, by for example hormones. thyroxin is produced by the thyroid gland, involved in metabolism, growth, and temperature regulation. melatonin is produced by the pineal gland, regulates the sleep-wake cycle. leptin is produced by adipose tissue, inhibits hunger. glucagon secreted by alpha cells of panncreas increase blood sugar content, insulin secreted by beta cells decrease blood sugar content. estrogen and progesterone secreted by ovaries are part of the female reproductive system. testosterone secreted by testes are part of the male reproductive system.