4674949
Descripción
Fichas por Laura Perry, actualizado hace más de 1 año
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Creado por Laura Perry
hace casi 9 años
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| Pregunta | Respuesta |
| How are action potentials transmitted? | An action potential causes sodium ion channels to open causing sodium ions to diffuse into the neurone. The concentration of sodium ions increases causing them to diffuse sideways down the concentration gradient (local current). This increases voltage causing voltage gated sodium ion channels to open causing the action potential to move down the neurone. |
| What is saltatory conduction and what are the advantages of it? | It means jumping conduction. When action potentials appear to jump from one node of Ranvier to the next. This causes the speed of transmission of action potentials to increase, as the action potentials only appear in the gaps between Schwann cells. |
| Target Tissue | A group of cells that have receptors embedded in the plasma membrane that are complementary in shape to specific hormone molecules. |
| What is the structure of a sensory neurone? | |
| What are the two parts of the adrenal glands? How are the arranged? | The adrenal medulla is in the center of the adrenal gland whilst the adrenal cortex is found around the outside of the adrenal medulla. |
| What is a pre-synaptic knob (or membrane)? | A swelling at the end of the pre-synaptic neurone that contains a large number of mitochondria, SER, neurotransmitters and voltage gated calcium ion channels. |
| How does frequency affect impulse of transmission? | The more intense a stimulus, the more frequent the action potentials will be. |
| What are the roles of synapses in the nervous system? | -To connect two synapses together. -To ensure action potentials only travel in the correct direction. -Summation -Acclimatisation |
| How is the transmission of action potentials different in a myelinated neurone? | The myelin sheath prevents sodium and potassium ions diffusing into the neuron, except where there are gaps in the myelin such as between Schwann cells (nodes of Ranvier). Ionic exchange only occurs here, elongating the local currents. |
| What is the definition of negative feedback? | A process in which any change in a parameter brings about the reversal of that change, so conditions are kept constant. |
| Exocrine Gland | A gland that secretes hormones into a duct that carries molecules to where they are used. |
| What happens when blood glucose levels drop too low? | The change is detected by alpha cells, which secrete the hormone glucagon. This converts glycogen into glucose (glycogenolysis) and amino acids into glucose (gluconeogenesis). |
| How is an action potential transmitted across the synaptic cleft? | The action potential arrives at the synaptic knob causing voltage gated calcium ion channels to open. Calcium ions diffuse in. This causes the vesicles containing the neurotransmitter to move to and fuse with the membrane (exocytosis). The neurotransmitter diffuses across the cleft and binds to sodium receptors. Sodium ion channels open and sodium ions move into the neurone. If enough ions move in creating generator potentials, then the threshold potential will be reached and the action potential will continue. |
| Second Messenger | A molecule that transmits a signal inside the cell, such as cyclic AMP. It causes an effect in cells by activating enzyme action. |
| What happens when blood glucose levels rise too high? | The change is detected by beta cells which secrete insulin. Adrenaline activates adenyl cyclase in the cell. converting it to ATP and the cAMP. Glucose then enters the cell causing glucose to turn into glycogen (glycogenesis), reducing blood glucose concentration. |
| What is the function of a sensory neurone? | To carry the action potential from a sensory receptor to the cell body. |
| How is an action potential generated? | Sodium ion channels open, allowing some sodium ions to diffuse into the cell. This depolarises the membrane until it reaches the threshold potential (-50mV). The voltage gated sodium ion channels open, allowing more sodium ions into the cell until it reaches +40mV. This causes the sodium ion channels to close and the potassium ion channels to open. The membrane is repolarised until the is a slight over soot (hyperpolarisation). The cell then returns to resting state. |
| What is the structure of a motor neurone? | |
| First Messenger | The hormone that transmits a signal around the body, such as adrenaline. |
| What are the exocrine and endocrine functions of the pancreas? | Exocrine- digestive enzymes are secreted into the pancreatic duct/ Endocrine- islet of langerhans. Alpha cells secrete glucagon and beta cells secrete insulin. These hormones are secreted directly into the blood capillaries. |
| What is the role of acetylcholinesterase? | It is an enzyme found in the synaptic cleft which hydrolyses acetylcholine into ethanoic acid and choline which the re-enter the synaptic knob by diffusion. It stops the transmission of signals. |
| What is the definition of positive feedback? | A process in which any change in a parameter brings about an increase in that change. |
| Hormone | A molecule released into the blood which acts as a chemical messnger. |
| How is transmission effected in a non-myelinated neurone? | The sodium ions can diffuse into the neurone at any point so the local currents are generally much shorter and the speed of transmission is slower. |
| What are the roles of sensory receptors? | Specialised cells that detect changes in the surroundings.The are energy transducers, so change one type of energy into another. |
| What are the functions of the adrenal medulla? | Manufactures and releases adrenaline in response to shock or stress. This increases heart rate and stroke volume. It also causes vasoconstriction and increased mental awareness as well as dilating pupils. |
| How is insulin secretion controlled? | Glucose levels rise and enter the cell. The glucose is then metabolised into ATP which causes the potassium channels to close, increasing the voltage inside the cell to become more positive. Calcium ions then enter the cell causing insulin to be secreted, lowering blood glucose levels. |
| What is an ectotherm? | An organism that relies on external sources of heat to regulate its body temperature. |
| What is an endotherm? | An organism that can use internal sources of heat (e.g. metabolism) to maintain body temperature. |
| What are the advantages of genetically engineered insulin? | Less chance of having an intolerance to it. More effective. Cheaper to manufacture and to fit demand. There are less ethical issues. |
| How can stem cells be used to treat diabetes? | New stem cells in the pancreas could be used to produce new beta cells. |
| What causes type two diabetes? | The body can still make insulin, but it no longer responds to it. It is controlled through diet and insulin injections. |
| What causes type one diabetes? | The body destroys its beta cells so insulin cannot be made (auto immune). Insulin levels are controlled through injections and blood level monitoring. |
| What is the mechanism of homeostasis? | A change is detected by the receptors, the communication system transmits a message from the receptors to the effectors, causing the change to be reversed. |
| Cell signalling | Communication between cells. It involves a ligand being secreted and transported from the signalling cell to the target cell where it binds to the receptor sites. This creates a response. |
| How is resting potential established and maintained? | Three sodium ions are pumped out of the cell by diffusion for every two potassium ions pumped in. The membrane is also slightly permeable to potassium ions. The large negative anions maintain the -70mV charge. |
| Endocrine Gland | A gland that secretes hormones directly into the blood- there are no ducts. |
| What is the function of a motor neurone? | To carry the action potential to the effector. |
| Homeostasis | The maintenance of the internal environment despite changes to the outside environment. |
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