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Fluctuating External Conditions
- Features that influence internal environment have a set level → norm
- Any changes from the norm is called deviation
- Negative feedback / caused by deviation from norm / change results in return to norm
- External environment is changing → experienced by body
- Homeostatic system even out variations experienced by body
- Liver can store or release glucose
- Liver can store or release glucose
- Blood is kept at a constant, ideal state
- Glucose conc. of 80mg cm-3
- Glucose conc. of 80mg cm-3
- Tissue fluid surrounds working cell with constant ideal conditions
- Optimum glucose for respiration
- Optimum glucose for respiration
- Homeostatic system even out variations experienced by body
- Homeostasis is achieved by a negative feedback and involves
- Change in level of an internal factor (change from norm level)
- Detected by receptors / impulse send to hypothalamus
- Activates effectors / stimulates corrective mechanism
- Level of factor returns to norm
- Change in level of an internal factor (change from norm level)
- Factors in blood and tissue fluid must be kept constant:
- Temp and pH
- Change affects rate of enzyme-controlled/biochemical reactions
- Extreme changes denatures proteins
- Humans maintain constant core body temp between 36-37.8°C
- Body temp refers to core body temp → limbs may be cooler than 37°C
- Change affects rate of enzyme-controlled/biochemical reactions
- Water potential / avoids osmotic problems → cellular disruption
- Conc of ions (Na, K, Ca)
- Temp and pH
- Blood flows through receptors in the hypothalamus
- Deviation causes the autonomic nervous system to initiate an appropriate response
- Receptors in hypothalamus detect increase in core temp/temp of blood
- Heat conversation centre stimulated
- VASOCONSTRICTION of arterioles
- Arterioles leading to capillaries in the skin narrow
- SHUNT VESSELS DILATE
- Less blood flows to skin surface / less heat is lost by RADIATION
- Hair raising / greater insulation / humans have less dense hair, therefore, no effect
- Shivering / rapid contraction and relaxation of muscles / heat produced by RESPIRATION
- Adrenaline INCREASES METABOLIC RATE of cells //Mammals in cold climates can increase secretion of thyroxine / hormone increases metabolic rate on a more permanent basis
- VOLUNTARY CENTRE: put on clothes / seek warmer areas / warm drink
- Receptors in hypothalamus detect increase in core temp/temp of blood
- Heat loss centre stimulated
- VASODILATION of arterioles
- Arterioles leading to capillaries in the skin dilate (expand)
- SHUNT VESSELS CONSTRICT
- More blood flows to skin surface (capillaries) / heat loss by RADIATION
- Heat loss by EVAPORATION of sweat / by using energy
- High(er) rate of sweating leads to a low(er) skin temp
- High(er) rate of sweating leads to a low(er) skin temp
- VOLUNTARY CENTRE: remove clothing / seek cooler area / cold drink
- Hypothalamus detects temp fluctuation inside the body/internal environment
- Skin receptors detect temp changes in external environment
- Information is sent by nerves to voluntary centres of the brain
- Voluntary activities (jogging, moving into a shade) are initiated
- Changes behaviour of human
- Voluntary activities (jogging, moving into a shade) are initiated
- Surface area is very large and in direct contact to external environment
- Skin is divided into two layers: outer epidermis and inner dermis
- MALPIGHIAN layer is the boundary between these two layers
- Cells of this layer divide repeatedly by mitosis
- Older cells are pushed towards the surface/EPIDERMIS
- Cytoplasm of old cells becomes full of granules / cells die
- Cells become converted into scales of keratin (waterproof)
- Cells of this layer divide repeatedly by mitosis
- DERMIS is thicker than epidermis and contains
- Nerve endings (temp receptors)
- Blood vessels held together by connective tissue
- Nerve endings (temp receptors)
- Beneath dermis is a region which contains some subcutaneous fat
- Adipose tissue (fat storage tissue) provides vital insulations in humans
- Adipose tissue (fat storage tissue) provides vital insulations in humans
- Body temp falls dangerously below normal
- Heat energy is lost from body more rapidly than it can be produced
- Heat energy is lost from body more rapidly than it can be produced
- Brain is affected first → person becomes clumsy and mentally sluggish
- As body temp falls, metabolic rate falls as well
- Makes body temp fall even further, causing a POSITIVE FEEDBACK
- Temp is taken further away from the norm
- Temp is taken further away from the norm
- Death when core body temp is below ≈25°C / by ventricular fibrillation / normal beating of the
- heart is replaced by uncoordinated tremors
- Most at risk are (1) babies and (2) elderly
- (1) High surface area:volume ratio, undeveloped temp regulation mechanisms
- (2) Detoriated thermoregulatory mechanisms
- (1) High surface area:volume ratio, undeveloped temp regulation mechanisms
- Deliberate hypothermia is sometimes used in surgical operations on heart
- Patient is cooled by
- Circulating blood through a cooling machine
- Placing ice packs in contact with the body
- Circulating blood through a cooling machine
- Reduces metabolic rate / O2 demand by brain + other vital tissues is lowered
- Heart can be stopped without any risks of the patient suffering brain damage through lack of O2
- Tissues may be permanently damaged if patient is cooled to long
- Patient is cooled by
- Digestion of carbohydrates in diet
- Digestion → polysaccharide → glucose
- Fluctuation of glucose blood level depend on amount + type of carbohydrate eaten
- Digestion → polysaccharide → glucose
- Breakdown of glycogen
- Excess glucose → glycogen → glucose
- Storage polysaccharide made from excess glucose by glycogenesis
- Glycogen is abundant in liver + muscles
- Excess glucose → glycogen → glucose
- Conversion of non-carbohydrates to glucose by gluconeogenesis
- Oxidation of glucose by respiration
- Glucose → ATP → energy
- Rate of respiration varies for different activities
- This affects glucose uptake from blood into cells
- Glucose → ATP → energy
- Brain is unable to store carbohydrates
- Lack of glucose in blood → no respiratory substrate → insufficient energy for brain
- Short period of time already causes brain to malfunction
- Lack of glucose in blood → no respiratory substrate → insufficient energy for brain
- Normal glucose level in blood ≈90mg per 100cm²
- After a meal it rarely exceeds 150mg per 100cm²
- Endocrine role is to produce hormones
- Contains islets of Langerhans → sensitive to blood glucose conc
- Islet cells contain
- α-cells → secrete glucagon and β-cells → secrete insulin
- capillaries into which hormones are secreted
- delta cells → produce hormone somatostatin → inhibits secretion of glucagon
- α-cells → secrete glucagon and β-cells → secrete insulin
- Insulin mainly affects muscles, liver, adipose tissue
- Exocrine role is to produce digestive enzymes
- Active trypsin damages pancreas / digests proteins that make up pancreas / amylase leaks into blood from damaged tissues / amylase conc in blood higher
- Detected by β-cells in islet of Langerhans (receptor) → secrete insulin
- Increase in insulin secretion (corrective mechanism → effectors bring about a return to norm)
- Speeds up rate of glucose uptake by cells from blood
- Glucose enters cells by facilitated diffusion via glucose carrier proteins
- Cells have vesicles with extra carrier molecules present in their cytoplasm
- Insulin binds to receptor in plasma membrane
- Chemical signal → vesicles move towards plasma membrane
- Vesicle fuses with membrane → increases glucose carrier proteins
- Glucose enters cells by facilitated diffusion via glucose carrier proteins
- Activates enzymes / Converts glucose to glycogen / Promotes fat synthesis
- Speeds up rate of glucose uptake by cells from blood
- Detected by α-cells in islets of Langerhans → secrete glucagon
- Increase in glucagon secretion
- Hormone activates enzymes in the liver → convert glycogen to glucose
- Stimulates formation of glucose form other substances such as amino acids
- Hormone activates enzymes in the liver → convert glycogen to glucose
- Glucose passes out of cells into blood, raising blood glucose conc until norm is reached
- Diabetes mellitus → inability of control of blood glucose level
- High levels of blood glucose because
- Pancreas becomes diseased → fails to secrete insulin
- Target cells lose responsiveness to insulin
- Pancreas becomes diseased → fails to secrete insulin
- Kidney is unable to reabsorb back into blood all the glucose filtered into its tubules
- Glucose secreted into urine
- Craving for sweet food and persistent thirst
- Glucose secreted into urine
- DIAGNOSTIC: glucose tolerance test
- Patient swallows glucose solution
- Blood glucose level measured at regular intervals
- Patient swallows glucose solution
- Type I → insulin dependant/juvenile-onset
- Occurs in childhood
- Autoimmune reaction → immune system attacks and destroys own cells
- Destroys β-cells in islet of Langerhans → unable to produce insulin
- TREATMENT: insulin given must match glucose intake and expenditure
- Overdose causes hypoglycaemia (to much glucose withdrawn from blood)
- Diabetics need to manage their diet and levels of exercise
- Need to monitor blood glucose conc
- Overdose causes hypoglycaemia (to much glucose withdrawn from blood)
- Occurs in childhood
- Type II → insulin independent/late-onset
- Occurs late in life, more common than type I
- Causes by gradual loss in responsiveness of cells to insulin
- TREATMENT: regulated diet
- Sugar intake must balance with amount of exercises taken
- Sugar intake must balance with amount of exercises taken
- Occurs late in life, more common than type I
- Glycogen levels are lower
- Little insulin / no glucose to glycogen
- Insulin receptors no longer functional / less glucose taken up by cells
- Little insulin / no glucose to glycogen
- Glycogen is an effective storage molecule
- Insoluble → no osmotic effect
- Large → cannot diffuse out of cell
- Branched → easy to break down / hydrolyse to glucose
- Compact → large amount of glucose stored in small space
- Insoluble → no osmotic effect
- Insulin → peptide chains → digested if swallowed by peptidase → had to be injected
- Treat skin area with ultrasound → disrupts underlying fat tissues
- Insulin is not soluble in fat
- Disrupting tissues allows movement through skin
- Insulin is not soluble in fat
- Apply patch containing insulin to that area