chapter 16 Flashcards
receptor (sensor)
detects a stimulus that is involved with a physiological factor
coordinator system
transfer information between different parts of the body
effector (muscle gland)
to carry out a response
negative feedback
when any deviation from normal values are reasoned back into their original values
positive feedback
when change away from the normal initiates a response to increase change
hormones
Chemical messengers, often made of protein, secreted into the bloodstream from our endocrine glands.
Hormones travel to target organs / tissues via the bloodstream.
glycogenesis
the conversion of glucose to glycogen
glycogenolysis
the conversion of glycogen to glucose
gluconeogenesis
the conversion of non-carbohydrates to glucose
adrenaline
is a hormone released by the adrenal gland in response to stress or excitement
how does adrenaline increases blood glucose concentration
By attaching to receptors on the surfaces of target cells
and
activating enzymes involved in the conversion of glycogen to glucose - glycogenolysis
why must pH must be controlled
to maintain protein/ enzyme activity
diabetes
a medical condition where the patient is unable to control their blood glucose concentration
the second messenger model
- Adrenaline, the first messenger, binds to specific receptors on target cell surface membrane to form a hormone-receptor complex
- The hormone receptor complex activates an enzyme, adenylate cyclase, inside the membrane
- the activated adenylate cyclase converts ATP into cyclic AMP (cAMP)
- cAMP acts as the second messenger and activates another enzyme in the cytoplasm- a protein kinase- which causes the conversion of glycogen to glucose
factors that influence blood glucose concentration
- the breakdown of the carbohydrates ingested in the diet
- the breakdown of glycogen stored in the liver- glycogenlysis
- new glucose molecules synthesised from substances other than carbohydrates, such as glycerol and amino acids- gluconeogenesis
- level of mental and physical activity
insulin
hormone that lowers blood glucose concentration. beta cells in the insets of langerhans in the pancreas detect raised blood glucose levels and secrete insulin in response
how does insulin reduces blood glucose concentration
- Causing more glucose channels to be inserted into the cell membrane, so increasing the uptake of glucose, especially by muscle cells
- increasing the rate of respiration, so more glucose is used
- activating enzymes involved in the conversion of glucose to glycogen- glycogenesis- in muscle and liver cells
- causing excess glucose to be converted into fat
glucagon
increases blood glucose concentration. it is secreted by alpha cells in the islets of langerhans in the pancreas when blood glucose concentration is below the normal
how does glucagon raises blood glucose concentration
- attaching to receptors on the surface of target cells, such as liver and muscle cells
- activating enzymes involved in the conversion of the glycogen to glucose- glycogen-lysis
- activating enzymes involved int eh conversion of glycerol and amino acids into glucose - gluconeogenesis
- causing the body to use more fatty acids in respiration
type 1 diabetes
insulin dependent
cause: the pancreas stops producing insulin, usually in childhood
treatment: - injections of insulin, 2-4 times a day
- blood glucose concentration is monitored using biosensors
type 2 diabetes
insulin independent
cause: glycoprotein receptors on the cell surface membranes are lost or lose sensitivity; sometimes there is a reduction in insulin production
treatment : - regulate dietary carbohydrates, especially refined sugars
- may require insulin or drugs to stimulate insulin production.
what is osmoregulation
the balancing and control of water potential of the blood
what controls osmoregulation
- antidiuretic hormone (ADH)
- hypothalamus
- posterior pituitary gland
hypothalamus
a part of the brain that contains osmoregulatory receptor and produces ADH
posterior pituitary gland
the back part of the pituitary gland that secretes ADH
what are nephrons
are tiny tubules that make up the majority of a kidney. Nephrons remove waste products from the blood and produce urine
how the kidney maintain water potential of the plasma and hence tissue fluid
- formation of glomerular filtrate by ultrafiltration
- reabsorption of glucose and water by the proximal convoluted tubule
- maintenance of a gradient of sodium ions in the medulla by the loop of Henle
- reabsorption of water by the distal convoluted tubule and collecting ducts
the movement of glomerular filtrate out of glomerulus is restricted by
- epithelial cell
- connective tissue
- epithelial cells of the renal capsule
- hydrostatic pressure of the fluid in the renal capsule space
- the low water potential of the blood in the glomerulus
how is the resistance of the glomerular filtrate is overcome by…
-the renal capsule is made up of podocytes. the spaces between these cells and their and their branches allow filtrate to pass through
- the endothelium of the glomerular capillaries spaces between cells
- the resulting the hydrostatic presence of the glomerulus is sufficient to overcome the resistance and filtrate pass through
3 things that which increases solute concentration
- too little water being consumed
- too much perspiration
- excess in ion consumption
blood supply to the glomerulus
- blood arriving in the glomerulus
- it travels via the efferent arteriole
- the afferent arteriole is wider than the efferent arteriole
- this creates a high hydrostatic pressure in the glomerulus
- this pressure causes ultrafiltration
describe how ultrafiltration produces glomerular filtrate
- high hydrostatic pressure
- water/ glucose/ ions/ urea are filtered out
- through pores in the capillary endothelium
- and through podocytes
- large protein remains in the blood
How are epithelial cells in PCT adapted for selective absorption
have many microvilli- provides a large surface area
has many carrier protein in the cell membrane for active transport
there are many mitochondria for aerobic respiration which means that cells make lots of ATP for aerobic respiration
effect of adrenaline
causes :
-activates enzymes that causes glycogenolysis which causes blood sugar levels to increase
- heart rate and breathing rate to increase
- dilated pupils
- diverts blood away from the digestive system and towards skeletal muscles
actions of insulin
- attaches to receptors on the surface of target cells and causes changes on the tertiary structure of channel protein- more glucose is absorbed by facilitated diffusion
- more channel proteins creates larger surface area for glucose = more glucose is absorbed
- activate enzyme - catalyses conversion of glucose to glycogen
why is glucose found in the urine of a person with untreated diabetes
- there’s a high concentration of glucose in the blood
- not all glucose is absorbed at the proximal convoluted tubule
- carrier protein are working at a maximum rate
how increasing a cells sensitivity to insulin will lower the blood glucose concentration
- more insulin binds to receptors
- stimulates uptake of glucose by channel protein
2 reasons why pancreas transplants are not used for the treatment of type II diabetes
- insulin is still produced by type 2
- it is treated by controlling diet
2 ways in which people with type I diabetes control their blood glucose concentration
- having regular insulin injections
- control sugar intake
osmoregulation
controlling water potential of the blood
Hypertonic
blood with too low water potential- cells shrivel
- more water is absorbed by osmosis into the blood from the tubules of the nephron this means the urine is more concentrated as less water is lost in the urine
hypotonic
blood with a high water potential- cell burst
- less water is reabsorbed by osmosis into the blood from the tubules of the nephron. this means urines is more dilute and more water is lost in urine
role of the hypothalamus
changes in water concentration in the blood is detected by osmoreceptors in the hypothalamus
what happens if the water potential is too low
water leaves osmorecptors by osmosis
this stimulates hypothalamus to produce more ADH
what happens if water potential is too high
water enters osmoreceptors by osmosis this stimulates hypothalamus to produce less ADH
what is the role of ADH
increase permeability of the walls of collecting duct and distal convoluted tubule
-ADH binds to complementary receptors in the cell membrane of the kidneys
- this activate enzymes phosphorylase
- vesicles move towards membrane
- aquaporin embeds on membrane
- more water passes through
how ultrafiltration occurs in a glomerulus
High hydrostatic pressure
small substances pass out water, glucose, ions, urea;
Through small pores in capillary
endothelium;
And through capillary basement membrane;
