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37 Cards in this Set

  • Front
  • Back
Outline the need for communication systems within multicellular organisms
Multicellular organisms have internal cells that are not exposed to the external enviroment. Enzymes are required for cellular activities but they can only work at certain conditions; temp., pH etc.. This has to be maintained in order for the internal cells to be kept alive.
Define stimulus and response
Stimulus - Any change in the enviroment that causes a response
Response - A change in behaviour or physiology as result of a change
Define the terms negative/positive feedback and homeostasis
Negative feedback is the reversal of any change in conditions
Positive feedback is the increase of any change in conditions
Homeostasis is the maintenance of a constant internal enviroment despite external changes
Explain principles of homeostasis in terms of receptors, effectors and negative feedback
1.Stimulus - change away from optimum
2. Sensory receptors detect change
3. Communication system transmits information from receptors to effector cells
4. Effector makes a response to reverse any change
Distinguish between ectotherms and endotherms
An ectotherm is an organism that relies on external sources of heat
An endotherm use internal sources of heat
Outline the advantages and disadvantages of ectotherms
Use less food for respiration and more food can be used for growth
Ability to survive for long without food
Less active in cooler temperature e.g. winter
Outline the advantages and disadvantages of ectotherms
Fairly constant body temperature despite external temperature
Ability to inhabit colder habitats of the planet
Lots of energy is used
More food is needed
Less food for growth
Describe the physiological and behabvioural responses that maintain a constant core body temperature in ectotherms
Expose body to/away from sun
Hide in burrow
Alter body shape
Increase breathing movements
Describe the physiological and behabvioural responses that maintain a constant core body temperature in endotherms
Remain inactive and spread out limps/Move to gain heat from muscles respiring
Move into shade/towards sun
Sweat glands and panting remove latent heat as water evaporates
Hairs on skin provide insulation
Vasodilation dilates capillaries allowing more heat to be radiated
Vasoconstriction constricts capillairies - less close to surface
Liver cells - Rate of respiration can be increased/decreased
Skeletal muscles - spontaneous contractions causes muscles to respire more
Describe the mechanism for controlling body temperature
1. Stimulus is detected by thermoregulatory in hypthalamus
2. Nervous/hormonal system carry signals to skin, liver and muscles
3. More/less heat is generated so temperature goes back to optimum
Outline the roles of sensory receptors in mammals in converting different forms of energy into nerve impulses
Sensory receptors are also known as energy transducers that convert one form of energy to another. Each type of transducer is adapted to detect changes in particular form of energy. The stimulus energy is converted into a nerve impulse.
Describe how the structure of the neurones relate to their function
Neurones are very long so they can transmit action potential over a long distance
The plasma membrane has gated ion channels and Na/K pumps
Myelin Sheath insulates from electrical activities
Cell body contains many mitochondria
Describe and explain how the resting potential is established and maintained
The potential difference inside the cell is -60 mV compared to the outside. ATP is used to pump 3 Na+out and 2 K+in. As a result of this and anions inside the cell, a negative potential is maintained.
Describe how an action potential is generated
Na+ diffuse into cell causing a depolarisation. A small depolarisation will have no effect but if it reaches the threshold value at -50 mV an action potential will be generated with a potential difference of +40 mV.
Describe the stages of an action potential
1. Resting potential at -60 mV
i.e. 3Na+out & 2K+in using ATP
2. Na+ channels open and Na+ diffuse in causing depolarisation
3. Threshold at -50mV is reached
4. Voltage-gated channels open and Na+ influx occurs
5. Action potential is generated at +40 mV
6. Na+ channels close and K+ channels open
7. K+ influx causes repolarisation
8. Potential difference overshoots slightly - hyperpolarisation
9. Back to resting potential
Describe and explain how an action potential is transmitted along a myelinated neurone with reference to voltage-gated Na+ and K+ channels
An action potential arrives
Na+ channels open and Na+ diffuse across membrane
The balance of ionic concentrations is affected at that particular point
Na+ ions diffuse sideways
The movement is known as a LOCAL CURRENT
The movement of these Na+ causes a decrease in potential difference which opens voltage-gated channels and Na+ enters the cell which moves the action potential along the neurone
Ionic exchanges can only occur at Nodes of Ranvier -> saltatory conduction
Outline the stages during transmission of an action potential across the synapse
1. Action potential arrives at synaptic knob
2. The voltage-gated Ca2+ channels open
3. Ca2+ diffuses into synaptic knob
4. Ca2+ cause synaptic vesicles to fuse with presynaptic membrane
5. Neurotransmitter is released by exocytosis and diffuses across cleft
6. They bind to receptor sites on Na+ channels on postsynaptic membrane
7. Na+ channels diffuse into postsynaptic neurone
8. A generator potential is generated
9. If threshold value is reached new action potential is generated
Outline the roles of synapses in the nervous system
Ensure signals only transmit in one direction
Persistent low-level signals can be combined to generate action potential - Summation
After repeated stimulation a synapse may run out of neurotransmitter and the synapse is fatigued - Acclimatisation
Define endocrine gland, hormone and target tissue
Endocrine Gland
A gland that secretes hormones directly into the blood - no ducts
Released by endocrine glands and acts as messengers carrying a signal from the endocrine gland ti a specific target organ or tissue
Target tissue consist of many target cells which contain specific receptor for a complemtary hormone
State the two types of hormones
Two main types
Protein hormones
Stereoid hormones
Describe the functions of the andrenal glands
Andrenaline binds to complementary receptor site (first messenger)
This activates adenyl cyclase
This then converts ATP to cAMP (second messenger which activates other enzymes

Increases heart rate
Dilates pupils
Increases mental awareness
Outline the pancreas' role as an endocrine and exocrine gland
Exocrine Gland
Releases digestive enzymes into pancreatic duct that carries it to the first part of the small intestine
Endocrine gland
Islet of Langerhans contain alpha cells that secrete glucagon and beta cells secrete insulin into the blood.
Explain how glucose concentration is regulated
If blood glucose is too high
Beta cells secrete insulin
Target cells are hepatocytes, muscle cells and other cells
More glucose enters
More glucose channels open
More respiration of glucose
More glucose to fats

If blood glucose is too low
Alpha cells secrete glucagon
Target cells are hepatocytes
More fatty acids are respired
Outline how insulin secretion is controlled
Beta cell membranes consist of Ca2+ and K+ channels
1. K+ channel open and K+ diffuse out
2. Glucose move into cell
3. Glucose is respired to produce ATP
4. K+ channels close by ATP
5. The potential difference inside becomes less negative
6. This opens Ca2+ channels
7. Ca2+ cause vesicles with insulin to fuse with membrane, releasing insulin by exocytosis
Compare and contrast causes of type 1 and type 2 diabetes mellitus
Type 1 - Insulin-dependent
Auto-immune response
Viral attack

Type 2 - Insulin-independent
Diet - high in sugars
Asian or afro-carribean origin
Family history
Discuss two relatively new way to treat diabetes
Advantages of genetically manufactured insulin
Faster and more affective
Lower risk of infection
Less chance of rejection
No animal welfare issues
More adaptable to demand
Outline the hormonal and nervous mechanisms involved in the control of heart rate in humans
Accelerator nerve increases heart rate
Vagus nerve decreases heart rate
Adrenaline is secreted to increase heart rate
Define excretion
Removal of metabolic waste from the body
Explain importance of removing waste from body including co2 and nitrogenous waste
Carbon dioxide compete with oxygen to bind to haemoglobin
It can also cause respiratory acidosis
It is therfore breathed out from alveoli as we breathe

Excess amino acid is toxic
Amino acid + oxygen -> keto acid + ammonia
Ammonia + co2 -> urea + water
Describe the formation of urea in the liver
Orithine to Citrulline
Addition of Co2 and ammonia
Forms H2O
Citrulline to Arginine
Addition of ammonia
Forms H2O
Arginine to Ornithine
Addition of H2O
Forms Urea
Describe the roles of the liver in detoxification
In hepatocytes

Ethanol ---> Ethanal
NAD is reduced
Ethanal ---> Ethanoic acid
NAD is reduced
Ethanoic acid ---> coA
Describe and explain the processes of ultrafiltration
Endothelium has narrow gaps between its cells that blood plasma and substances can pass through
Basement membrane acts as a filter and prevent the passage of molecules woth a relative molecular mass greater than 69,000
Podocytes have major processes. Fluid can pass between these cells.
Describe and explain the process of selective reabsorbtion
1. Sodium ions are actively transported out of cells into tissue fluid
2. Glucose or amino acids enter cells with Na+ by facilitated diffusion
3. Water potential is reduced so water will diffuse in by osmosis
4. Glucose and amino acids diffuse into blood capillary
5. Water moves by osmosis into blood
Explain the control of water content of the blood
Loop of Henle
Descending limp
Water is lost by osmosis
Na+ and Cl- are diffused out
At the base
Na+ and Cl- diffuse out
No water movement
Thick ascending limp
Na+ and Cl- are actively transported out

The Collecting Duct
Water moves out by osmosis

The water potential of the blood is monitored by osmoreceptors in the hypthalamus. When the water potential is low the osmoreceptor cells will lose water and shrink which releases neurosecretory cells. They release ADH which is stored at the posterior pituitary gland until needed. ADH makes collecting duct walls more permable to water.
Outline the problems that arise from kidney failure
Unable to remove excess water and waste products
Leads to death
Discuss the use of renal dialysis and transplants for the treatment of kidney failure
Exchange of substances between dialysis fluid and blood

Advantages of kidney transplant
Diet is less limited
Feeling better physically
A better quality of life

Need immunosuppressants
Need major surgery
Risks of surgery e.g infection
Describe how urine samples can be used to test for pregnancy and detect misuse of anabolic stereoids
Human chorionic gonadotrophin (hormone) is released
Specific antibody bind to hCG and moves up strip till it reaches immobilised antibodies. They carry a blue bead forming a blue line

Testing for anabolic stereoids involves mass spec and gas chromotography