ib-biology-optione

[ib-biology-optione]

Objectives

E.1.1 Define the terms stimulus, response and reflex in the context of animal behaviour. E.1.2 Explain the role of receptors, sensory neurons, relay neurons, motor neurons, synapses and effectors in the response of animals to stimuli. E.1.3 Draw and label a diagram of a reflex arc for a pain withdrawal reflex, including the spinal cord and its spinal nerves, the receptor cell, sensory neuron, relay neuron, motor neuron and effector. (Include white and grey matter, and ventral and dorsal roots.) E.1.4 Explain how animal responses can be affected by natural selection, using two examples. E.2.1 Outline the diversity of stimuli that can be detected by human sensory receptors, including mechanoreceptors, chemoreceptors, thermoreceptors and photoreceptors. E.2.2 Label a diagram of the structure of the human eye. ( The diagram should include the sclera, cornea, conjunctiva, eyelid, choroid, aqueous humour, pupil, lens, iris, vitreous humour, retina, fovea, optic nerve and blind spot.) E.2.3 Annotate a diagram of the retina to show the cell types and the direction in which light moves. ( Include names of rod and cone cells, bipolar neurons and ganglion cells.) E.2.4 Compare rod and cone cells E.2.5 Explain the processing of visual stimuli, including edge enhancement and contralateral processing. E.2.6 Label a diagram of the ear. (Include pinna, eardrum, bones of the middle ear, oval window, round window, semicircular canals, auditory nerve and cochlea.) E.2.7 Explain how sound is perceived by the ear, including the roles of the eardrum, bones of the middle ear, oval and round windows, and the hair cells of the cochlea. E.3.1 Distinguish between innate and learned behaviour. E.3.2 Design experiments to investigate innate behaviour in invertebrates, including either a taxis or a kinesis. E.3.3 Analyse data from invertebrate behaviour experiments in terms of the effect on chances of survival and reproduction. E.3.4 Discuss how the process of learning can improve the chance of survival. E.3.5 Outline Pavlov’s experiments into conditioning of dogs. ( The terms unconditioned stimulus, conditioned stimulus, unconditioned response and conditioned response should be included.) E.3.6 Outline the role of inheritance and learning in the development of birdsong in young birds. E.4.1 State that some presynaptic neurons excite postsynaptic transmission and others inhibit postsynaptic transmission. E.4.2 Explain how decision-making in the CNS can result from the interaction between the activities of excitatory and inhibitory presynaptic neurons at synapses. E.4.3 Explain how psychoactive drugs affect the brain and personality by either increasing or decreasing postsynaptic transmission. E.4.4 List three examples of excitatory and three examples of inhibitory psychoactive drugs. E.4.5 Explain the effects of THC and cocaine in terms of their action at synapses in the brain. E.4.6 Discuss the causes of addiction, including genetic predisposition, social factors and dopamine secretion. E.5.1 Label, on a diagram of the brain, the medulla oblongata, cerebellum, hypothalamus, pituitary gland and cerebral hemispheres. E.5.2 Outline the functions of each of the parts of the brain listed in E.5.1. E.5.3 Explain how animal experiments, lesions and FMRI (functional magnetic resonance imaging) scanning can be used in the identification of the brain part involved in specific functions. E.5.4 Explain sympathetic and parasympathetic control of the heart rate, movements of the iris and flow of blood to the gut. E.5.5 Explain the pupil reflex. E.5.6 Discuss the concept of brain death and the use of the pupil reflex in testing for this. E.5.7 Outline how pain is perceived and how endorphins can act as painkillers. E.6.1 Describe the social organization of honey bee colonies and one other non-human example. E.6.2 Outline how natural selection may act at the level of the colony in the case of social organisms. E.6.3 Discuss the evolution of altruistic behaviour using two non-human examples. E.6.4 Outline two examples of how foraging behaviour optimizes food intake, including bluegill fish foraging for Daphnia. E.6.5 Explain how mate selection can lead to exaggerated traits. E.6.6 State that animals show rhythmical variations in activity. E.6.7 Outline two examples illustrating the adaptive value of rhythmical behaviour patterns.

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[ib-biology-optione]

Neuro in Topic 6

This is a summary of the neuro content in Topic 6: Human health and physiology "6.5.1 State that the nervous system consists of the central nervous system (CNS) and peripheral nerves, and is composed of cells called neurons that can carry rapid electrical impulses. The nervous system consists of the central nervous system (CNS) and peripheral nerves, and is composed of cells called neurons which carry rapid electrical impulses. 6.5.2 Draw and label a diagram of the structure of a motor neuron.

6.5.3 State that nerve impulses are conducted from receptors to the CNS by sensory neurons, within the CNS by relay neurons, and from the CNS to effectors by motor neurons. Nerve impulses are conducted from receptors to the CNS by sensory neurons, within the CNS by relay neurons, and from the CNS to effectors by motor neurons. 6.5.4 Define resting potential and action potential (depolarization and repolarization). Resting potential: the electrical potential across the plasma membrane of a cell that is not conducting an impulse. Action potential: the reversal and restoration of the electrical potential across the plasma membrane of a cell, as an electrical impulse passes along it (depolarization and repolarization). 6.5.5 Explain how a nerve impulse passes along a non-myelinated neuron. Sodium is found in greater concentrations outside of the cell while potassium is found in greater concentrations inside the cell. Sodium-potassium pumps exist in the plasma membrane to maintain the the concentration gradients and the membrane potential. Nerve impulses have a domino effect. An action potential in one part of the neuron causes another action potential in the adjacent part and so on. This is due to the diffusion of sodium ions between the region of the action potential and the resting potential. It is the movement of sodium and potassium that reduce the resting potential. If the resting potential rises above the threshold level, voltage gated channels open. Voltage gated sodium channels open very fast so that sodium can diffuse into the cell down its concentration gradient. This reduces the membrane potential and results in more sodium channels opening. Sodium ions are positively charged and so the inside of the cell develops a net positive charge compared to the outside of the cell. This results in depolarization as the potential across the membrane is reversed. A short while after this, voltage gated potassium channels open and potassium ions flow out of the cell down the concentration gradient. Since potassium ions are positively charged, their diffusion out of the cell causes a net negative charge to develop again inside the cell compared to the outside. The potential across the membrane is restored. This is called repolarization. Finally, the concentration gradients of both ions are restored by the sodium-potassium pump. Sodium is pumped out of the cell while potassium is pumped in. The resting potential is restored and the neuron is ready to conduct another nerve impulse. Summary: 1.Resting potential rises above threshold level. 2.Voltage gated sodium channels open. 3.Sodium ions flow into the cell, more sodium channels open. 4.Inside of cell develops a net positive charge compared to the outside and results in depolarization. 5.Voltage gated potassium channels open. 6.Potassium ions flow out of the cell. 7.Cell develops a net negative charge compared to the outside and results in repolarization. 8.Concentration gradients restored by sodium-potassium pumps. 9.Resting potential is restored. 6.5.6 Explain the principles of synaptic transmission. A synapse is a junction that permits a neuron to pass an electrical or chemical signal to another cell. At a synapse, the plasma membrane of the signal passing neuron (presynaptic neuron) is closely related to the plasma membrane of the target cell (postsynaptic neuron). Between the two there is a narrow fluid filled space called the synaptic cleft. Chemical signals called neurotransmitters pass from the presynaptic neuron to the post synaptic neuron. This is how a synaptic transmission occurs: An action potential travels along the neuron and reaches the end of the pre-synaptic neuron. The depolarization of the pre-synaptic membrane results in the opening of voltage gated calcium channels. Calcium ions flow into the presynaptic neuron and cause vesicles with neurotransmitters inside the neuron to fuse with the plasma membrane and release the neurotransmitters into the synaptic cleft via exocytosis. These neurotransmitters then diffuse within the synaptic cleft and some will bind to specific receptors located on the postsynaptic plasma membrane. The receptors are transmitted-gated ion channels which open and let sodium and other positively charged ions into the postsynaptic neuron when the neurotransmitters bind. As these positively charged ions enter the postsynaptic neuron they cause its membrane to depolarize. This depolarization results in an action potential which passes down the postsynaptic neuron. The neurotransmitters in the synaptic cleft are then quickly degraded and the calcium ions are pumped back into the synaptic cleft from inside the presynaptic neuron.

Summary: 1.Action potential reaches the end of a presynaptic neuron. 2.Voltage gated calcium channels open. 3.Calcium ions flow into the presynaptic neuron. 4.Vesicles with neurotransmitters inside the presynaptic neuron fuse with the plasma membrane. 5.Neurotransmitters diffuse in the synaptic cleft and bind to receptors on the postsynaptic neuron. 6.The receptors are channels which open and let sodium ions into the postsynaptic neuron. 7.The sodium ions cause the postsynaptic membrane to depolarize. 8.This causes an action potential which passes down the postsynaptic neuron. 9.Neurotransmitters in the synaptic cleft are degraded and the calcium ions are pumped back into the synaptic cleft." From source # 1

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[ib-biology-optione]

Sources

1. http://www.ibguides.com/biology/notes/nerves-and-hormones 2. IB HL Biology Pearson Book 3. http://www.scribd.com/doc/51159010/IB-Biology-Option-E-Notes 4. http://www.ib.bioninja.com.au/options/option-e-neurobiology-and-2/ 5. Scientific American 6. National Geographic 7. http://www.youtube.com/user/SCScienceVid 8. http://www.sandi.net/cms/lib/CA01001235/Centricity/Domain/2936/2009Objectives/Option%20E.pdf

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[ib-biology-optione]

2.7 explained

[ib-biology-optione]

1.1 - 1.3 explained

#videos

[ib-biology-optione]

The Synapse

#videos

[ib-biology-optione]

Neurons

#videos

[ib-biology-optione]

Resting & Action Potentials

Click to Run

Note: Depending on your computer settings, this game might open automatically or become a file in your downloads. In case of the second possibility, open the file to play.

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#interactivegames #games

[ib-biology-optione]

Predicting Recovery from the Vegetative State

From Scientific American (http://www.scientificamerican.com/article.cfm?id=conditional-consciousness ) In patients who have survived severe brain damage, judging the level of actual awareness has proved a difficult process. And the prognosis can sometimes mean the difference between life and death. New research suggests that some vegetative patients are capable of simple learning—a sign of consciousness in many who had failed other traditional cognitive tests. To determine whether patients are in a minimally conscious state (in which there is some evidence of perception or intentional movement) or have sunk into a vegetative state (in which neither exists), doctors have traditionally used a battery of tests and observations. Many of them require some subjective interpretation, such as deciding whether a patient’s movements are purposeful or just random. “We want to have an objective way of knowing whether the other person has consciousness or not,” says Mariano Sigman, who directs the Integrative Neuroscience Laboratory at the University of Buenos Aires. That desire stems in part from surprising neuroimaging work that showed that some vegetative patients, when asked to imagine performing physical tasks such as playing tennis, still had activity in premotor areas of their brains. In others, verbal cues sparked language sectors. A recent study found that about 40 percent of vegetative state diagnoses are incorrect. To explore possible tests of consciousness in patients, Sigman and his colleagues turned to classical conditioning: they sounded a tone and then sent a light puff of air to the patient’s eye. The air puff would cause a patient to blink or flinch the eye, but after repeated trials over half an hour, many patients would begin to anticipate the puff, blinking an eye after only hearing the tone. If two stimuli are delivered at exactly the same time, even snails will equate the stimuli. But the team actually delayed the puff after the tone by 500 milliseconds. To associate two stimuli separated by that time gap, “you need conscious processing,” says lead study author Tristan Bekinschtein of the Impaired Consciousness Research Group at the University of Cambridge. In fact, delaying the second stim­ulus by more than 200 milliseconds is enough to demonstrate some learning, he adds. By comparison, people under general anesthesia, considered to be entirely lacking awareness, showed no sign of such learning when given the tone and air-puff test. The detection of learning, described in the September 20 Nature Neuroscience (Scientific American is part of the Nature Publishing Group), also opens up questions about when patients should be classified as being in a persistent vegetative state, in which emergence isn’t predicted to be likely. (Terri Schiavo, the center of a heated national debate in 2005, was determined to be in such a state.) Decisions to end life support often depend on predictions of recovery and assessments of consciousness. If “someone shows the patients can learn,” Bekinschtein says, “I think it would be a very clear argument.” Indeed, the researchers found that learning ability accurately predicted the extent of recovery within the next year about 86 percent of the time. The neural reorganization that bypasses damaged parts of the brain “implies that there’s room for at least some recovery,” Bekinschtein notes. The findings do not surprise everyone. Research using functional MRI on vegetative patients had already led John Whyte, principal investigator at the Neuro-Cognitive Rehabilitation Research Network at Thomas Jefferson University in Philadelphia, to question the designation system. It may be that “there is a firm line” between vegetative and minimally conscious patients,” he observes. “But our tools are too crude to tell us who is on which side of the line.” Or it may be that categories of consciousness are not so easy to define.

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[ib-biology-optione]

Brain Games Versus Nature Documentaries

From National Geographic (http://news.nationalgeographic.com/2013/03/130410-brain-games-neuroscience-culture-science/) It seems brain-training games—online tests, quizzes, games, or flash cards designed to improve attention, memory, creativity, and concentration—are everywhere. But do they work? A recent study published in the journal PLoS ONE says … maybe not. When researchers tested employees of the Australian Taxation Office to see if brain games boosted their mental capabilities, it turned out that workers who watched nature documentaries instead fared better on tests measuring language skills (as well as quality of life and self-esteem). Cate Borness, a graduate researcher at the University of New South Wales in Sydney,Australia, tested 135 Australian public-sector employees on their productivity, stress, cognitive functions, and overall quality of life to get baseline performance levels. Then she and her colleagues randomly assigned them to either a test group that underwent 16 weeks of short brain-training sessions using Happy Neuron software, or a control group that spent 16 weeks watching short nature documentaries and answering brief questions about them (to prove they'd watched the videos). The short clips were taken from National Geographic’s video website. Members of the control group—the "active control"—were assigned a task like watching the documentaries to ensure that any benefits seen from the brain-training app weren't simply because the control subjects were bored while the test subjects' brains were firing on all cylinders. Nature and Language "We didn't find a huge impact in terms of the cognitive training program," Borness said. But, oddly enough, the group that watched the documentaries left the study with statistically significant benefits. The nature video group said that their stress had gone down, their quality of life had increased, and—according to tests that Borness and her colleagues gave both groups—their language skills had improved. (Read “Beyond the Brain” in National Geographic magazine.) That could be because the videos and short questionnaires were language-based, Borness said. "You're listening to a video and then answering questions about it." The brain-training games, on the other hand, were designed to improve multiple measures of intelligence and cognitive function; only about 20 percent of the games emphasized language skills. One such game involved users having to fit words into boxes such that the last letter of a word was also the first letter of another word. The language-game players did see a slight increase in their language skills, but not nearly as much of an increase as the video watchers. In the paper, Borness speculates that this could be because the games focused on language only a fifth of the time, with other games dedicated to memory, attention, reasoning, and more. Yet those games didn't produce any measurable effects in the test population. Brain games like these could still be useful for some people, Borness said. "The product may be questionable in its efficacy, [but] I think part of the problem is not doing enough of it to have an effect." However, she added, "we haven't figured out what is 'enough.'" Despite the results of the study, Borness says she herself is still a user of brain-training games. "I think they're fun. I'm one of those people who can't do nothing, so I get on my phone and play games."

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[ib-biology-optione]

Optogenetics: Controlling the Brain with Light

Adapted From Scientific American : (http://www.scientificamerican.com/article.cfm?id=optogenetics-controlling) Despite the enormous efforts of clinicians and researchers, our limited insight into psychiatric disease (the worldwide-leading cause of years of life lost to death or disability) hinders the search for cures and contributes to stigmatization. Clearly, we need new answers in psychiatry. But as philosopher of science Karl Popper might have said, before we can find the answers, we need the power to ask new questions. In other words, we need new technology. Developing appropriate techniques is difficult, however, because the mammalian brain is beyond compare in its complexity. It is an intricate system in which tens of billions of intertwined neurons—with multitudinous distinct characteristics and wiring patterns—compute with precisely timed, millisecond-scale electrical signals, as well as with a rich diversity of biochemical messengers. Because of that complexity, neuroscientists lack a deep grasp of what the brain is really doing—of how specific activity patterns within specific brain cells ultimately give rise to thoughts, feelings and memories. By extension, we also do not know how the brain's physical failures produce distinct psychiatric disorders such as depression or schizophrenia. The ruling paradigm of psychiatric disorders—casting them in terms of chemical imbalances and altered levels of neurotransmitters—does not do justice to the brain's high-speed electrical neural circuitry. And psychiatric treatments have historically been largely serendipitous: helpful for many but rarely illuminating, and suffering from the same challenges as basic neuroscience. In a 1979 Scientific American article Nobel laureate Francis Crick suggested that the major challenge facing neuroscience was the need to control one type of cell in the brain while leaving others unaltered. Electrical stimuli cannot meet this challenge because electrodes are too crude a tool: they stimulate all the circuitry at their insertion site without distinguishing between different cell types, and their signals cannot turn off neurons with precision. Drugs are not specific enough either, and they are much slower than the natural operating speed of the brain. Crick later speculated in lectures that light might have the properties to serve as a control tool because it could be delivered in precisely timed pulses, but at the time no one had a strategy to make specific cells responsive to light. Meanwhile, in a realm of biology as distant from the study of the mammalian brain as might seem possible, researchers were working on microorganisms that would only much later turn out to be relevant. At least 40 years ago biologists knew that some microorganisms produce proteins that directly regulate the flow of electric charge across cell membranes in response to visible light. These proteins, which are produced by a characteristic set of "opsin" genes, help to extract energy and information from the light in the microbes' environments. In 1971 Walther Stoeckenius and Dieter Oesterhelt, both then at the University of California, San Francisco, discovered that one of these proteins, bacteriorhodopsin, acts as a single-component ion pump that can be briefly activated by photons of green light—a remarkable all-in-one molecular machine. Later identification of other members of this family of proteins—the halorhodopsins in 1977 and the channelrhodopsins in 2002—continued this original theme from 1971 of single-gene, all-in-one control. In 20/20 hindsight, the solution to Crick's challenge—a potential strategy to dramatically advance brain research—was latent in the scientific literature even before he articulated the challenge. Yet it took more than 30 years, until the summer of 2005, for these fields to come together in a new technology (optogenetics) based on microbial opsin genes. Optogenetics is the combination of genetics and optics to control well-defined events within specific cells of living tissue. It includes the discovery and insertion into cells of genes that confer light responsiveness; it also includes the associated technologies for delivering light deep into organisms as complex as freely moving mammals, for targeting light-sensitivity to cells of interest, and for assessing specific readouts, or effects, of this optical control. What excites neuroscientists about optogenetics is control over defined events within defined cell types at defined times—a level of precision that is most likely crucial to biological understanding even beyond neuroscience. The significance of any event in a cell has full meaning only in the context of the other events occurring around it in the rest of the tissue, the whole organism or even the larger environment. Even a shift of a few milliseconds in the timing of a neuron's firing, for example, can sometimes completely reverse the effect of its signal on the rest of the nervous system. And millisecond-scale timing precision within behaving mammals has been essential for key insights into both normal brain function and into clinical problems such as parkinsonism.

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[ib-biology-optione]

Section 5: The human brain

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[ib-biology-optione]

6.1

Describe the social organization of honey bee colonies and one other non-human example Honey bees ◾Honey bees (Apis mellifera) live and interact in large colonies (20,000 - 80,000 members) that show eusocial behaviour ◾There is a reproductive division of labour, whereby each type of bee is specialized for a particular task that helps the group as a whole ◾ A single queen bee (reproductive female) is responsible for the production of eggs ◾A few drone bees (reproductive males) are responsible for the fertilization of the eggs ◾The majority of bees are workers (sterile females) and may be subdivided into various castes - foragers, soldiers, etc. Baboons ◾Baboons (Papio cynocephalus) live and interact in small groups called troops (10 - 20 members) organized according to physical dominance ◾Troops are structured around dominant females who rank as leaders, while males will move in and out of different troops ◾Members of the troop do not share food, each individual is responsible for themselves (no division of labour) ◾Baboons do not have a mating season, so females are readily available and highly promiscuous (will take many male partners) ◾Males will form relationships with females through social activities such as grooming, and may help to defend females and infants Adapted from source #4

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Section 6: Further studies of behavior

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6.2

Outline how natural selection may act at the level of the colony in the case of social organisms ◾Natural selection is a mechanism of evolution that acts on the gene pool of a given population ◾Beneficial alleles (those that promote survival) become more frequent in a population as individuals with those alleles are more likely to achieve reproductive success ◾Many organisms form social clusters as their survival prospects (and those of offspring) are improved by cooperative group organization ◾Because colonies are usually comprised of genetically related individuals (family members), behaviours or traits that benefit the colony (such as shared nursing duties) will improve the reproductive fitness of the group, even if it does not directly benefit the individual ◾Such characteristics are more likely to be passed on to subsequent generations and hence become more frequent in the gene pool From source #4

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6.3

Discuss the evolution of altruistic behaviour using two non-human examples ◾Altruism is behaviour which benefits another individual at the cost of the performer ◾It appears to be in opposition to natural selection as it reduces the possibility of the altruistic individual passing on their own genes ◾However it improves the chances of the other individual passing on genes into the same gene pool (this is called inclusive fitness) ◾If the individuals are closely related, altruistic genes will persist in the gene pool and be naturally selected ◾Enhancing the reproductive success of relatives is called kin selection ◾Altruism occurs in social animals and is more common in members of the same species who are closely related Examples of Altruism: ◾Vampire bats commonly regurgitate blood to share with unlucky or sick roost mates unable to gain independent sustenance ◾Velvet monkeys give alarm calls to warn fellow monkeys of predators, even though doing so draws attention to themselves ◾Termites break a gland in their neck, releasing a sticky substance which protects others from attacking ants at the cost of their life From source #4

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