Communication/Homeostasis Flashcards
Definition of homeostasis?
The maintenance of a constant internal environment within a narrow limit despite conditions changing
What external factors need to be monitored?
Temperature, light intensity, humidity, pH
What internal factors must be kept fairly constant?
Temperature, blood glucose, blood pressure, blood salt, water potential of blood and CO2 concentration
Why must factors be kept within certain limits?
So cells function normally and enzymes work at optimum level/don’t denature
How does the body know when to remove a waste product?
The accumulation of waste products acts as a stimulus and causes the removal of these wastes into the blood so they can be excreted
What is the definition of a stimulus?
Change in the environment that requires a response
What part of a body detects a change?
Receptors
What is the sequence from stimulus to response?
Stimulus, receptor, sensory neurone, co-ordinator, motor neurone, effector, response
What is negative feedback?
When a deviation from the set point cause a sequence of events that counteracts the change and restores the set point
What 2 systems are used to respond to a stimulus?
Hormonal
Nervous
What 2 things does the body do to regulate respiratory gases during exercise?
Increase breathing rate
Increase heart rate
What is the definition of positive feedback?
When a deviation from the set point causes changes that result in an even greater deviation.
How is childbirth an example of positive feedback?
Oxytocin stimulates uterine contractions and pushes baby towards cervix, head of baby pushes against cervix, nerve impulses from cervix are transmitted to the brain, brain stimulates pituitary gland to secrete oxytocin, oxytocin carried in bloodstream to uterus
What will a good communication system do?
Cover the whole body Enable cells to communicate with each other Enable specific communication Enable rapid communication Enable short and long term responses
How do cells communicate with each other?
Cell signalling
What 2 ways can cell signalling occur?
Electrical (neurones) very quick, rapid response to stimuli that may change quickly
Chemical (hormones) uses blood to transport signals, longer responses to specific target cells
Why is it important to maintain solute/glucose levels?
Otherwise changes the water potential and therefore amount of osmosis that occurs in cells
What is thermoregulation?
Process whereby animals regulate their temperature
What can some animals do in order to prevent ice crystals forming in their cells?
If cells cool below 0 degrees some animals produce antifreeze
What is the core temperature of humans?
37 degrees
What is a homeotherm?
Regulate body temperature about a set point
What is a poikilotherm?
Allowed their body temperature to conform to the environment, fluctuates
When are poikilotherms better than homeotherms?
In an environment with a stable temperature (deep sea fishes) may have a more constant body temperature than homeotherms
What are ectotherms?
Animals that use external heat sources to regulate temperature. They have a relatively low metabolic rate, do not use metabolism to generate heat and have a body temperature that conforms to the ambient temperature.
What are endotherms?
Animals that use metabolism to generate body heat and maintain their temperature above the ambient temperature
What are features of ectotherms?
Body temperature depends on environment
Have a variable metabolic rate so generate little heat
Temperature determines their activity levels
Regulate temperature by changing their behaviour
What are features of endotherms?
Efficient mechanisms for thermoregulation
Less affected by surrounding temperature
Constantly high metabolic rate so generate lots of heat
Can also change behaviour to control temperature
What behavioural things can an animal do to maintain body temperature?
Reorientation of the body varies surface area exposed to the sun. Thermal gaping - open mouth, more evaporation Colour change - dark absorb more heat Body raising - less conduction Burrowing - more stable environment Bask in the sun to warm up Find shade to cool down Go in water to cool down
Why do most ectotherms live in water?
Water has a high specific heat capacity so doesn’t change temperature quickly/often
Why do endotherms need more food?
Use metabolic reactions in order to produce heat which requires energy from food
What part of the brain receives sensory input about the temperature?
Hypothalamus
What receptors detect a change in temperature?
Thermoreceptors
Where are thermoreceptors found?
Hypothalamus
Skin (peripheral)
What do thermoreceptors in the hypothalamus detect?
Temperature of the blood
What do peripheral thermoreceptors detect?
External air temperature
What is the effect of thermoreceptors?
Send nerve impulses along sensory neurons to the hypothalamus. This sends nerve impulses along motor neurons to the effectors. These then respond to restore the body temperature
What is the main advantage of having the two thermoreceptors?
Respond to both external and internal changes
What are the two temperature control centres in the hypothalamus?
Heat loss centre
Heat gain centre
When is the heat loss centre activated?
When the temperature of the blood flowing through the hypothalamus increases
When is the heat gain centre activated?
When the temperature of the blood flowing through the hypothalamus decreases
What neurons are impulses sent along in the heat loss centre and the heat gain centre?
Autonomic motor neurons
What response does the heat loss centre trigger?
Triggers responses to lower core body temperature
What response does the heat gain centre trigger?
Triggers responses to increase core body temperature
What do endotherms use to keep warm?
Internal exothermic metabolic reactions
What do endotherms use to cool down?
Energy requiring physiological responses
How does your body use smooth muscle in arterioles when it is too hot?
Smooth muscle in arterioles vasodilate to divert more blood through the capillaries near the skin so heat is lost through radiation.
How does your body use sweat when it is too hot?
Sympathetic nerves stimulate secretion of sweat from the arteriole and cells of the glandular tube, it goes to the surface of the skin via the sweat duct where evaporation takes heat away from the blood.
How does your body use the thyroid gland when it is too hot?
The thyroid gland produces less thyroxine which reduces the metabolic rate so less energy is released by metabolic reactions.
How does your body use smooth muscle in arterioles when it is too cold?
Smooth muscle in arterioles vasoconstrict to divert blood away from the capillaries near the skin so less heat is lost from the blood through radiation.
How does your body use shivering when it is too cold?
Muscles contract more and release heat in respiration.
How does your body use piloerection when it is too cold?
Erector pili muscles contract so hairs stand up trapping an insulating layer of air.
How does your body use its liver when it is too cold?
The liver becomes more active so there are more metabolic reactions that generate heat by respiration.
What is Allen’s rule?
Endotherms from colder climates usually have shorter limbs than the equivalent animals from warmer climates.
What is topor?
It is the deliberate lowering of the set point so food isn’t needed to meet the demands of thermoregulation.
Why is brown fat useful for babies and infants?
Nonshivering thermogenesis occurs in brown fat, lots of mitochondria generate heat and make the cell brown. Babies don’t have fully formed thermoregulatory system so have to generate heat another way.
What is regional heterothermy?
Cold climate homeotherms can allow their appendages to cool to reduce heat loss.
What does counter-current mean and how does it lead to regional heterothermy?
Counter-current heat exchange occurs between warm out-flowing blood in a central artery and cold in-flowing blood in surrounding veins.
What is the definition of a response?
Caused by a stimulus and alters the physiology or behaviour of an organism
Why do cells need to communicate?
So that cells can work together in a coordinated manner in multicellular organisms
What physiological things do ectotherms do to maintain temperature?
Increase/decrease breathing movements to cool down/stay warm
What are the advantages of being an ectotherm?
Don’t need to use energy to maintain temperature
Not as much food required (e.g. snake)
More energy used for growth
What are the disadvantages of being an ectotherm?
Reliant on weather conditions to be active Time needed to regulate temperature Locations for habitats ate limited Risk of predation when cold Not active in winter
What are the advantages of being an endotherm?
Always at optimum body temperature No time needed to regulate temperature Less risk of predation when cold More habitats available Not reliant on weather conditions to be active
What are the disadvantages of being an endotherm?
Need to use own energy to regulate temperature
Need to eat lots of food
Not as much energy for growth
What are the two fluids cells are surrounded by?
Interstitial fluid
Plasma
What is the definition of gland?
An organ that synthesises a substance (hormone or enzyme) for release
What is the definition of secretion?
Production and release of a useful product from cells
What is the definition of excretion?
Getting rid of metabolic waste products that the body makes
What is the definition of egestion?
Getting rid of a waste product that the body hasn’t made
What is the definition of hormone?
A chemical which is produced by one part of the body travels in the bloodstream and has and effect on the target organ
What are the two types of gland?
Exocrine gland
Endocrine gland
What are exocrine glands?
Glands that secrete substances to a surface/cavity via a duct
What are endocrine glands?
Ductless glands that secrete hormones into the blood
What are some examples of substances that exocrine glands secrete?
Enzymes
Sweat
Milk
What are some characteristics of endocrine glands?
No duct Rich blood supply Only interact with specific receptors on target cells Eg adrenal glands secrete adrenaline Thyroid glands secrete thyroxine
Why do only some cells respond to a hormone?
Hormones are specific to receptors on target cells
Why can hydrophobic hormones pass out of the cell by simple diffusion?
Dissolves through the phospholipids
What hormones does the pituitary gland secrete?
ADH
Oxytocine
What hormones does the thyroid gland secrete?
Thyroxine
What hormones does the thymus gland secrete?
Thymosin
What hormones does the adrenal gland secrete?
Adrenaline
What hormones does the pancreas secrete?
Insulin
Glucagon
What hormones does the ovaries secrete?
Oestrogen
What hormones does the testes secrete?
Testosterone
What does the hormone thymosin do?
Promotes production and maturation of white blood cells
What does the hormone adrenaline do?
Prepares the body for action (fight or flight)
What does the hormone thyroxine do?
Controls metabolic rate
Hypothyroxine - too little, gain weight
Hyperthyroxine - too much, lose weight
What does the hormone oestrogen do?
Prepares the uterus for fertilised egg
Controls ovulation
What does the hormone testosterone do?
Regulates sperm cell production and secondary sex characteristics
What are protein/peptide hormones?
Protein based. They are not soluble (hydrophilic) in the membrane, so don’t enter the cell. They need to bind to the cell surface membrane and release a second messenger
What is a steroid hormone?
Cholesterol based. Can pass through the membrane (hydrophobic) and into the cell. The receptor is in the cytoplasm. Act upon the DNA in the nucleus.
Examples of peptide hormones
Adrenaline
Insulin
Examples of steroid hormones?
Oestrogen
Testosterone
What does adrenaline act as?
First messenger
What happens when the adrenaline binds with the glycoprotein receptor on the cell surface membrane?
The shape of the receptor is changed which causes it to interact with a G protein
What does the G protein do?
Splits and part of it combines with an inactive enzyme called adenylyl cyclase
What does adenylyl cyclase do?
Converts ATP to cyclic AMP
What is cyclic AMP?
Second messenger
What does CAMP activate?
A cascade of enzymes. The last enzyme is a kinase
What does a kinase do?
Adds a phosphate to an enzyme which alters the activity of the enzyme, changing the cells metabolism
How does the secretion of adrenaline help the body prepare for action?
Increases hydrolysis of glycogen so increased blood glucose level increased rate of respiration so more energy released
How can adrenaline have different effects?
Binds to different specific complimentary receptors which have different second messengers so activate different enzymes
What are some effects of adrenaline?
Relaxes smooth muscle of the bronchioles
Increases stroke volume of the heart
Increases heart rate
Cause general vasoconstriction to raise blood pressure
Simulate conversion of glycogen to glucose
Dilate the pupils
Increases mental awareness
Decreases action of the gut
Cause body hair to become erect
What are the two parts of adrenal glands?
Cortex (outside)
Medulla (inside)
What three types of hormones does the cortex of the adrenal gland secrete?
Mineralocorticoids
Glucocorticoids
Sex hormones
What hormone does the medulla of the adrenal gland secrete?
Adrenaline
What do mineralocorticoids do?
Maintain concentration of mineral ions in the blood
What do glucocorticoids do?
Long term maintenance of glucose concentration in the blood
What part of the adrenal gland gives long term effects?
Cortex
What part of the adrenal gland gives short term effects?
Medulla
When are the hormones of the medulla released?
After the sympathetic nervous system is stimulated which occurs when you’re stressed
Under what conditions is adrenaline released?
Stressful/threatening conditions
Why are the effects of adrenaline widespread?
Adrenaline receptors are on the cell surface membrane of many cells and tissues
What is the release of glucocorticoids triggered by?
Hypothalamus and pituitary gland
When are glucocorticoids released?
In response to stress or as a result of low blood glucose concentration
What are mineralocorticoids triggered by?
Kidneys
Where is aldosterone produced?
Adrenal cortex
What organ does aldosterone target?
Distal convoluted tubules of kidney
What effect does aldosterone have on the distal convoluted tubules of kidney?
Sodium conservation
Where is cortisol produced?
Adrenal cortex
What organ does cortisol target?
Liver
What effect does cortisol have on the liver?
Stimulates gluconeogenesis
What are the other names for type one diabetes?
Insulin dependent diabetes
Juvenile onset diabetes
What are the other names for type two diabetes?
Insulin independent diabetes
Late/mature onset diabetes
What happens regarding insulin with type one diabetes?
The body doesn’t produce insulin
What happens regarding insulin with type two diabetes?
They produce insulin but glycoprotein receptors on the body cells lose their responsiveness to insulin.
It may be due to an inadequate supply of insulin from the pancreas.
Who mainly suffers from type one diabetes?
Children
Who mainly suffers from type two diabetes?
Adults over 40
What causes type one diabetes?
Normally a result of an autoimmune disease whereby the body’s own immune system attacks its own beta cells.
The cells being attacked are the beta cells that produce insulin.
What causes type two diabetes?
Obesity/lack of exercise.
Diet high in sugars particularly refined sugars.
Being of Asian or Afro-Caribbean origin.
Family history.
How do you treat type one diabetes?
Regular injections of insulin, dose must match patient so biosensors monitor blood glucose.
Managing carbohydrate intake.
Exercising carefully.
How do you treat type two diabetes?
Controlling intake of carbohydrates.
Matching carbohydrate intake with exercise.
May also inject insulin/use drugs that stimulate insulin production.
Drugs can be used to slow down the rate at which the body absorbs glucose from the intestine.
What are the future treatments of type one diabetes?
Using stem cells to produce insulin.
Gene therapy, gene for insulin is inserted into the diabetic’s cells.
What are the future treatments of type two diabetes?
Artificial pancreas that secretes insulin/glucagon.
Islet of Langerhans transplants.
Manipulating other cell types to replace beta cells.
What is glycogenolysis?
Hydrolysis of glycogen
What is gluconeogenesis?
Making glucose from non-carbohydrate molecules
What is glycolysis?
First step in respiration
What is glycogenesis?
Making glycogen from glucose
What is lipogenesis?
Making lipids in order to store excess glucose
How does the pancreas act as an endocrine gland?
Secretes hormones (insulin/glucagon) directly into the blood
How does the pancreas act as an exocrine gland?
Cells secrete digestive enzymes into duct that leads to the stomach
What cells secrete enzymes in the pancreas?
Acinar cells
What tissue secretes endocrine hormones in the pancreas?
Islets of Langerhans
What cells are in the Islets of Langerhans?
Alpha cells - secrete glucagon
Beta cells - secrete insulin
What is the normal level of glucose in the blood?
70-110 mg/dL or 4-6.1 mmol/L or 90 mg per 100cm³ of blood
What will happen if there’s too little glucose in the blood?
Affect the rate of respiration, especially in the brain
What will happen if there’s too much glucose in the blood?
Water potential of blood decreases drawing water out of tissues.
Decreases blood pressure
How do you recognise the Islets of Langerhans in a micrograph?
They are patches scattered through the exocrine tissue that are lightly stained
What percentage of the pancreas is made up of the Islets of Langerhans?
15%
What detects an increase in glucose levels?
Beta cells in the Islets of Langerhans in the pancreas
How do beta cells react to an increase in glucose levels?
Secretes insulin into the blood, the insulin then travels around the body
What cells have receptors for glucose?
Skeletal muscle cells
Liver cells
Adipose tissue
How does glucose enter the cells?
Through carrier proteins
How does insulin increase the uptake of glucose?
It increases the number of carriers for glucose
What happens to the extra glucose entering the cells when there is insulin?
Activate enzymes to convert glucose to glycogen (glycogenesis)
Activates enzymes to convert glucose to fat (lipogenesis)
Increase use of glucose used in respiration
What time of feedback is used to maintain glucose?
Negative feedback
What detects a decrease in glucose levels?
Alpha cells in the Islets of Langerhans in the pancreas
How do alpha cells react to a decrease in glucose levels?
Alpha cells secrete glucagon into blood that then travels around the body
What cells have receptors for glucagon?
Liver cells
What does glucagon do to increase glucose?
Activates enzymes that hydrolyse glycogen to glucose (glycogenolysis)
Gluconeogenesis
Respiration of non-glucose sources
What happens when glucose enters a beta cell?
Activates glucokinase so more respiration occurs producing more ATP
When more ATP is in the beta cell, what happens?
ATP sensitive potassium channels close preventing K+ from leaving making the cell less negative
What happens when a beta cell becomes less negative/depolarised?
Voltage gated calcium channels open so calcium enters the cell
What happens when calcium enters a beta cell?
Calcium fuses with vesicles containing insulin, this makes them move to the membrane, fuse with it and release insulin from the cell by exocytosis
What is hypoglycemia?
When there’s very low concentration of glucose, for example after exercise
What is hyperglycemia?
Very high concentration of glucose
What was the problem with using insulin from cows or pigs to treat type one diabetes?
Religious reasons
Ethical reasons
Slightly different from human insulin so some immune responses.
How do we get insulin to treat type one diabetes?
Use genetic engineering so the insulin gene from human DNA is inserted into the DNA of a bacterium. The bacterium is then cultivated.
Two advantages of treating type one diabetes using insulin that has been produced by genetically modified bacteria instead of extracted from pigs or cows.
Cheaper
No ethical objections
Advantage of using stem cells to treat type one diabetes instead of using insulin injections.
It is more of a long term solution
