« Mike Goikhberg Reflex Physiology Lab Report Introduction Our experiment was concerned with the reflex response in humans, and how it compares to a voluntary ...» Document abstract
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Language : english
medical studies
case study
date published
23/10/2007
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SummaryOur experiment was concerned with the reflex response in humans, and how it compares to a voluntary neural pathway as well as how it is enhanced by what is known as the Jendrassik Maneuver. Our hypothesis was that the reflex response would be faster than the voluntary response, and that with the Jendrassik maneuver, the reflex would be even more responsive. We predicted the latency to be lower for the reflex as compared to the voluntary response, and the amplitude to be higher for the reflex with the Jendrassik maneuver as compared to the reflex on its own. We conducted this experiment with the help of an apparatus that measured the angle during leg movement after the reflex. Specifically, flexion of the quadriceps (the reflex response) would cause the leg to kick out. The apparatus was basically two pieces of plastic connected to each other at a joint. One piece was attached to the calf and the other to the thigh. When the leg kicked out, the angle at which the two pieces of plastic connected changed, and the magnitude of change was recorded on a computer hooked up to the device. It would serve well to understand some background information about the neuron, neurotransmitters and their receptors, excitatory/inhibitory reflexes, and involuntary reflexes.
Table of Contents- The neuron consists of the soma (cell body), axon, dendrites, and in some cases myelin sheaths.
- The knee jerk reflex tested in this experiment was one such involuntary movement.
- Materials and Methods
- Results
- The average latency for the reflex knee jerk was .32 seconds.
- Discussion
- Our results were consistent with our hypothesis and our predictions.
- As for the voluntary knee jerk vs. the reflex knee jerk, our predictions also held up.
« Reflex Physiology Introduction A human specimen can contain a number of involuntary responses (responses not consciously controlled) to outside stimuli ...» Document abstract
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medical studies
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date published
02/10/2007
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SummaryA human specimen can contain a number of involuntary responses (responses not consciously controlled) to outside stimuli; science calls this response a reflex. Some reflexes disappear as e mature into adults, such as suckling, grasp reflex, Moro reflex and several others (Wikipedia, the Free Encyclopedia, Wikimedia Foundations, Inc. Reflex. http://en.wikipedia.org/wiki/Reflex#Significance, Viewed 04/22/07). Other reflexes, such as the knee jerk response stay with us for ever. Doctors use reflexes such as the knee jerk reflex, also called the Patellar Reflex, to see if the person’s sensory neurons, motor neurons and spinal cord are working properly.
Table of Contents- A human specimen can contain a number of involuntary responses (responses not consciously controlled) to outside stimuli; science calls this response a reflex.
- In this particular reflex, the tendon connected to the quadriceps is tapped causing the muscles of the quadriceps to stretch.
- Procedures were followed exactly as detailed in Foundations of Biology
- Based solely on our experiments our hypothesis for the Patellar reflex was confirmed.
- As with any experiment, human error can always influence results, making the conclusions not as apply able, especially since a small sample size was used.
« More specifically the knee-jerk reflex properly working is an indication that there is an appropriate Foundations of Biology: Cell and Organ Physiology. ...» Document abstract
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Language : english
medical studies
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date published
09/10/2007
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Summary Reflexes are the body’s involuntary responses to various stimuli. They are controlled in large part by the human nervous system which has three main functions: sensory input, integration, and motor output. Sensory input is due to sensory receptors throughout the body collecting information about one’s external surroundings and internal environment, and relaying them to various information centers. A sensory receptor recognizes some form of stimulus in the external or internal environment and responds by creating graded potentials or action potentials in the cell or in the cell adjacent to it. These action potentials consequently lead to integration. Integration is mainly carried out within the Central Nervous System, which consists of the brain and spinal cord in humans. (Campbell, 1024) Motor output is what occurs when the central nervous system makes sense of the sensory input due to integration, and sends information to effector cells in the body. Effector cells are the gland cells or muscle cells that make sure the body’s responses to certain stimuli are carried out. (Campbell, 1024) Nerves conduct these signals. Specifically speaking, the particular nerves that relay the motor and sensory information from the central nervous system jointly make up what is called the peripheral nervous system.
Table of Contents- Introduction
- Reflexes are the body's involuntary responses to various stimuli.
- Neurons are the main unit of the nervous system.
- The whole process of a knee jerk reflex requires only three neurons.
- Results
- Table 2 shows the results of the first test, during which we delivered a tap to the patellar tendon with the hammer.
- In the third experiment on a human subject, we incorporated the Jendrassik maneuver.
- Two important terms to define are flexion and extension.
- Discussion
- Even though sources of error do exist, our results closely mimic our hypothesis.
- In the third experiment, we combined the use of the Jendrassik maneuver with the involuntary knee jerk reflex, once again striking the patellar tendon directly with the hammer.
- Negative feedback is the process where a change in a physiological variable triggers a response that counteracts the initial reaction.
« during acute behavioral sensitization of the gill-withdrawal reflex in Aplysia An important principle in K+ channel physiology is that certain neurotransmitters ...» Document abstract
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Language : english
biology
research papers
date published
26/11/2007
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level : Advanced
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SummaryStructure and Function of Voltage-Gated Ion Channels Voltage-gated ion channels allow the flow of ions in response to changes in membrane voltage and are key elements in neuronal excitation and inhibition. Although ion channels can usually pass more than a single type of ion, voltage-gated channels are named according to the predominant ion that flows when the channel is open. Ion channels that are selective for Na+, K+, Ca2+, or Cl– have been described in neuronal membranes. Certain ion channels that are gated directly by chemical neurotransmitters such as glutamate and acetylcholine are selective for Na+, K+, and Ca2+ but exclude Cl– and are called nonselective cationic channels.
Table of Contents- Sodium (Na+) Channels Na+ channels are primarily responsible for the fast upstroke of action potentials, although in some neurons Na+ channels also contribute to lower-level depolarizations and pacemaker firing.
- Relations between primary protein structure and ion channel function in Na+ channels have been examined using mutations of specific amino acid residues.
- The net effect is similar to the scorpion toxins. Finally, certain local anesthetic drugs, including lidocaine and procaine, block Na+ channels by binding reversibly to sites within the hydrophobic regions of the ion channel.
- Delayed-rectifier channels open slowly and show little inactivation during prolonged depolarizations.
- M channels represent a class of K+ channels that are activated in a time- and voltage-dependent fashion but are blocked by the neurotransmitter, acetylcholine, acting at muscarinic receptors.
- KATP channels exist in the CNS and appear to be involved in regulating the release of certain neurotransmitters and perhaps in determining the response of some neurons to changes in intracellular energy levels.
- Calcium (Ca2+) Channels Because Ca2+ is involved in numerous cellular events including enzyme activation, gene expression, and neurotransmitter release, the regulation of intracellular Ca2+ levels is of major importance to neurons.
- Most structural information about Ca2+ channels comes from skeletal muscle HVA Ca2+ channels.
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