NEUROSCIENCE Reflex action Intelligenc e Neuro-diseases Biology Club Second bulletin
Contents: Reflex action
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Reflex arc Types of reflex
Intelligence
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Nature vs Nurture How to improve
Diseases
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Parkinson’s disease Alzheimer’s disease Amnesia
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Reflex Action Reflexes are automatic, subconscious response to changes within or outside the body. It is an activity performed by the peripheral nervous system of human brain in response to certain changes in the environment or the surrounding or by the body itself. Reflex action is mostly involuntary and it is a counter brain mechanism to handle different situations at different intervals.
Function 1. Maintain homeostasis, e.g. heart rate, breathing rate, blood pressure, and digestion etc. 2. Carry out automatic actions, e.g. swallowing, sneezing, coughing, vomiting etc. 3. Maintain balance & posture, e.g. control trunk and limb muscles 4. Brain reflexes – involve reflex center in the brain stem, e.g. reflexes for eye movement
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Reflex arc The reflex arc governs the operation of reflexes. Nerve impulses are transmitted along the nerve pathways as they travel through the nervous system. The simplest of these pathways, including a few neurons, constitutes a reflex arc. The reflex arc that passes through the spinal cord is called spinal reflexes.
A. Overview of the Reflex Arc 1. Receptor - Detects the stimulus and is sensitive to a specific type of internal or external change 2. Sensory neuron - Conveys the sensory information to brain or spinal cord - Transmits nerve impulses from the receptor into the brain or spinal cord 3. Interneuron - Serves as the processing center, conducts nerve impulses from the sensory neuron to a motor neuron 4. Motor neuron - Conducts motor output to the periphery - Transmits nerve impulse from the brain or spinal cord out to an effector 5. Effector - Response to stimulation by the motor neuron and produces the reflex or behavioral action.
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B. Process A receptor detects the stimulus(change in environment) A sensory neuron sends a signal to the relay neuron The relay neuron sends the signal to the motor neuron The motor neuron sends a signal to the effector The effector produces a response
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Other Forms of Reflex Action 1.Knee jerk reflex If you tap on the tendon of a muscle, it contracts. Its synergist’s contract and its antagonists are inhibited. A tap on the tendon stretches the extensor muscle and its spindle. The spindle discharges and excites the associated sensory fibers that excite the motor neurons to the extensor muscle. Contraction of the extensor muscle extends the lower leg (knee - jerk). ď Š
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2.Primitive reflex
Primitive reflexes are automatic stereotypic movements directed from the brainstem and require no cortical involvement. They are needed for survival and development in the womb and in the early months of life. However, as higher more sophisticated centers of the brain begin to reach maturity, these primitive reflexes become a nuisance and must be abated in order for proper neurological organization of the brain to develop.
Consequences If the primitive reflexes are retained past the first year of life, they can interfere with social, academic, and motor learning. Basically, the perception of our inner and outer environment and our response to it may be disturbed; that is, conscious life may be disturbed. Children with learning disorders, ADHD, Autism Spectrum, and various other neurodevelopmental disorders are known to have retained primitive reflexes contributing to their symptoms and level of dysfunction. Each reflex is associated with one or more of the Sensory Processing Systems: Auditory, Taste, Tactile, Smell, Visual, Vestibular, Proprioceptive and/or Interoceptive. Therefore, if retained, a child/person may experience dysfunction within one or several of the sensory processing systems. This can lead to what is known as Sensory Processing Disorder 7
Types of primitive reflex
A. The Moro Reflex This reflex is also referred to as the ‘Startle Reflex’. When you fail to support or hold your baby’s neck and head or if your baby becomes startled by a loud noise, bright light or sudden touch, the arms of your baby will thrust outward and then curl in as to embrace themselves. This reflex should disappear between 2-4 months of age. B. The Rooting Reflex When you stroke your baby's cheek she will turn towards you, usually looking for food. This is very useful when learning to breastfeed your baby. This reflex should be gone by 3-4 months of age. C. The Palmar Reflex This reflex is also referred to as the ‘Grasp reflex’. It is demonstrated by 8
placing your finger or an object into your baby's open palm, which will cause a reflex grasp or grip. If you try to pull away, the grip will get even stronger. This reflex should be gone by 2-3 months of age. D. Asymmetrical Tonic Neck Reflex (ATNR) This reflex is also referred to as the “fencer position�. To elicit this reflex, while your baby is lying on his back, turn his head to one side. This should cause the arm and leg on the side that he is looking toward to extend or straighten, while his other arm and leg will flex. The ATNR prepares the baby for future transitional movements like turning from back to front and vice versa. It also helps to later develop hand-eye coordination and activities that require crossing the mid-line of the body. It is also thought to be involved in the birthing process and if weak in utero, it may lead to the baby becoming stuck in the birth canal. It is reinforced by the natural birthing process. This reflex should be gone by4-6 months. E. Tonic Labyrinthine Reflex (TLR) With this reflex, tilting the head back while lying on the back causes the back to stiffen and even arch backwards, causes the legs to straighten, stiffen, and push together, causes the toes to point, causes the arms to bend at the elbows and wrists, and causes the hands to become fisted or the fingers to curl. This reflex prepares the baby for movements of rolling over, crawling on all fours, standing and walking. The presence of this reflex beyond the newborn stage is also referred to as abnormal extension pattern or extensor tone. Inhibition of the tonic labyrinthine reflex is a gradual process involving the maturation of other systems. This reflex should be gone by three and a half years of age.
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Intelligence There are different kinds of intelligence, and it’s up to scientists on how to identify and categorize them. Below are the main types of intelligences that we humans have.
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Biologically, our brains are split into two separate halves. This physical boundary sets up a nice way to describe the brain; left versus right side. It is known that the differing sides of the brain perform different functions. Here is a list of common features that show up on the respective halves: Left Brain
Right Brain
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Logical
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Random
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Sequential
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Intuitive
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Rational
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Holistic
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Analytical
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Synthesizing
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Objective
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Subjective
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Looks at parts
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Looks at wholes
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Symbolic
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Casual
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Linear
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Concrete
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Factual
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Visual
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Abstract
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Sensory
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Digital
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Spatial 12
*Please be reminded that the functions are varied between people.
Interesting facts about intelligence 1. Males estimate their general intelligence higher than females do 2. Nearly all participants rated their father’s IQ higher than their mothers 3. About 50% of the time females rated their IQ lower than it really is
Q: What affects our intelligence? A: Nature vs. Nurture. We are all paying for extra tuition for tutorial classes thinking that this can increase our intelligence. The nature vs. nature debate has been going on for decades, however, to what extent can intelligence be “acquired� or nurtured? Below is a summarized table showing the results from scientific researches that supports Nature or Nurture: Nature
Nurture
Scientific studies
Results from Researches
1. Uncovered genes linked to
2. Intelligence is a complex, multi-
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e.g. identical twins from the same egg and sharing the same genetic make-up are more likely to get the same IQ score than nonidentical twins from different eggs.
dimensional phenomenon and it is more the result of the way your genes interact with your environment than necessarily the genes themselves
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3. Shown a correlation between
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4. Educational background, physical
intelligence and the overall size of the brain and glucose metabolic rate during problem solving
environment factors, such as diet, could influence intelligence,
Mice with certain genes “knocked out� displaying interference with specific spatial tasks.
There is temporary drop in IQ during school vacations; and delay in schooling causes IQ to drop on average 5 points per year
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Schooling and intelligence influence each other. Higher intelligence tends to lead to prolonged schooling and longer schooling leads to higher IQ
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Diets lacking in the essential fatty acids required for brain health lead to seriously impaired learning skills
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Diets supplemented with the correct amounts of fatty acids, like alpha-linoeic acid and docosahexaenoic acid (DHA) result in improved mental performance and IQ scores as well as better moods and ability to handle stress
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Through the researches that have been done, it seems that heredity, as well as environment plays an important role in humans’ intelligence; but these are not exactly equal to influence. A person’s entire environment seems to be more effectual in determining his mental ability than heredity is. Using the most fundamental way to explain, it is heredity that determines one’s potential, but environment determines how far one will reach that potential during his lifetime. For example, some genes increase our risk of heart disease: but if we know this and eat less fat, we reduce the risk. Thus, you need to interact and learn from your environment in order to reach your actual, inborn potential, which was determined by your genes.
Conclusion The general consensus at the moment on the nature vs. nurture debate 15
for intelligence appears to be 50 / 50 and more research is required to determine the relative extent of influence by each factor.
How can I improve it? People are just born brainier than others? No! There’s a lot we can all do to improve our brainpower and hence our intelligence. While there is a strong genetic component to intelligence, research shows that IQ is more a result of the way your genes interact with your environment. There are lots of ways to stimulate your brain and here are some biological recommendations.
• Use your nose -
Olfactory senses: one of the first to develop
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One of the most strongly linked with mental processes
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Smells can trigger a memory more sharply t han sights or sounds
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Inhaling certain scents can have a stimulating effect on the brain, perking you up while others can have a calming, sedating effect. Rosemary is a popular recommendation for waking up the brain. Although research is still needed to prove its effects, this is one safe trick that’s worth a try.
• Top up on proteins -
Affects brain performance by supplying the amino acids which make up the neurotransmitters used in brain signals
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For example, one precursor of neurotransmitters is an essential amino acid, tryptophan, which can only be gained through the diet. So make sure you eat plenty of seafood, meat, eggs, soy, and dairy
• Include fish in your diet
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Especially oily, fatty fish such as salmon, trout and sardines
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The brain is made up of 60% essential fatty acids, such as alphalinoeic acid (ALA) and docosahexaenoic acid (DHA), which play important roles in brain neuron communication
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Diets lacking in essential fatty acids lead to seriously impaired learning skills or even possibly to mental disorders, while diets rich in essential fatty acids lead to improved mental performance and IQ scores.
Remember, your brain is similar to a muscle – the more your exercise it in the right ways, the more you will increase its ability and potential.
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Neuroscience
Related disease ďƒ¨ Parkinson’s disease: Loss of neurons that release dopamine, a compound present in the body as a neurotransmitter and a precursor of other substances including adrenalin, leading to physical impairment
- Strikes nearly 50,000 in North America - Occur most likely after 55
- Symptoms: stiff joints and muscle tremors in the hands and feet
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- Result: loss of mobility and mentally impaired and depressed
- Cause: - degeneration of dopamine-releasing neurons in the area of the midbrain that coordinates muscle movement. The shortage of dopamine impairs the ability to perform smooth, coordinated motions
- Treatment: - Taking L-dopa (a drug for the body to converts into dopamine) but could reduce the loss of neurons; receiving transplants of fetal neurons directly into the brain which come from aborted fetuses, this is very controversial but it replace lost cells
ďƒ¨ Alzheimer’s disease: - Shortage of acetylcholine, a compound which occurs throughout the nervous system, in which it functions as a neurotransmitter, leading to mental impairment a. One in every ten people has the disorder b. Occurs over age 65 c. Family history of the disease increases the risk
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- Symptoms: - Occurrence of memory lapses and progresses to severe memory loss especially for short-term memory. However, long-term memory is affected more slowly. Also, disoriented, demented and develop personality changes can occur
- Results: - The patient can no longer be able to function independently
- Cause: Unknown, but possibly involves the abnormal gene on chromosome 21 for beta amyloid (an abnormal protein) precursor protein
- Affection: - Neurons in the limbic system and frontal lobe which uses acetylcholine as their neurotransmitter, as the disease progresses, the supply of acetylcholine becomes insufficient for normal neurotransmission; the brain will have abnormal, tangled neurons 20
and unusually large deposits of beta amyloid; the metabolic activity in the frontal and temporal lobes declines and the levels of the enzyme which produce acetylcholine will also decrease
- Treatment: - Drugs can slow the progressions of the disease but there is no cure yet
ďƒ¨ Amnesia disease Symptoms: 1. Impaired ability to learn new information following the onset of amnesia ; and 2. To recall past events and previously familiar information 3. False recollections (confabulation), either completely invented or made up of genuine memories misplaced in time 4. Neurological problems such as uncoordinated movements, tremors or seizures 5. Confusion or disorientation Result: Loss of memory such as facts, and experiences but not self-identity Cause: - Damage to brain structures that form the limbic system, which controls your emotions and memories - Hippocampal formations: situated within the temporal lobes of your brain 21
- Brain inflammation resulting from infection with a virus such as herpes simplex virus or as an autoimmune reaction to cancer somewhere else in the body - Lack of adequate oxygen in the brain - Long-term alcohol abuse leading to vitamin B-1 deficiency Treatment: a. Memory training b. Use a PDA, such as BlackBerry or iPhone. With some training and practice, even people with severe amnesia can use these electronic organizers to help with day-to-day tasks c. Electroconvulsive therapy, a procedure in which electrical currents are passed through the brain, sometimes used to treat certain mental illnesses ďƒ¨ No medication are currently available to cure amnesia
Reference: http://www.macalester.edu/academics/psychology/whathap/ubnrp/int elligence05/Mtypes.html
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Biology club Bulletin team: Carol Chan 5B Adrian Wong 5A Collin Sze 4C
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Wong Long Yin Lillian 3A Lam Ho Ching Anson 4A Lam Yan Yin 4G Cheong Chi Wing 5F So Bernice Tak 5F
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