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33 Cards in this Set
- Front
- Back
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What are the three main types of muscle in the human body? What are their 'jobs'? |
Smooth: associated with the autonomic nervous system - e.g. lining of gut and arteries. Cardiac: found in heart - can contract even in the absence of input from the nervous system Striated: accounts for the majority of muscles in the body - moves our muscles and joints, helps us breathe by moving our chest and produces our speech through facial muscle movements. |
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Describe the appearance of the striated muscle. What is the muscles activated by and where? |
Striped appearance as each muscle is made of a series of muscle fibres. Each fibre is excited by a single nerve cell axon. Muscles are usually arranged in pairs - one usually flexes whilst the other contracts - they work as functional antagonists. Activated by motor neurons in the ventral horn of the spinal cord (lower or alpha-motor neurons) |
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What are alpha-motor neurons? |
Located in the ventral horn of the spinal chord and activate striated muscles. They are not distributed evenly within the spinal cord and the size of the ventral horn varies accordingly.
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What is a reflex and what are the two types of principle reflex response that we need to know (there are actually four)? |
An involuntary, stereotyped response to a sensory stimulus, where the strength of the motor response is graded with the intensity of the stimulus. There are four principle reflex responses (only two we're learning though): the monosynaptic stretch reflex and the polysynaptic flexor reflex. |
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What is the monosynaptic stretch reflex and what can we do to test it? |
Describes the tendency of the skeletal muscle to contract in response to being stretched. This response is initiated by stretching the muscle either by tapping the muscle itself or its tendon with a reflex hammer. |
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Describe the monosynaptic reflex process. |
Every striated muscle contains muscle spindle fibres that measure the length and rate of stretch of a muscle. Whenever the muscle is stretched, the muscle spindle fibres are also stretched, and there is an increase in the rate of firing la sensory axons. The la afferent fibres enter the dorsal horn of the spinal chord through the dorsal root ganglion where they synapse directly with alpha motor neurons that innervate the muscle containing the stimulated spindle. The motor neuron then fires, thus causing contraction on the muscle. |
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Describe the polysynaptic flexor process. |
(Used to withdraw a limb from adverse stimuli, such as standing on a pin.) As you stand on the pin you will activate mechanosensory and pain receptors on the base of your foot. This causes action potentials to fire and run along the sensory afferent axon into the spinal cord. Unlike the stretch reflex, the flexor reflex involves more than just a single motor neuron. As the sensory axon enters the spinal cord, it branches considerably. Each of these branches then forms a synapse with an Interneuron. These interneurons and excitatory and excite motor neurons in the ventral horn of the spinal cord. As with the stretch reflex, when the motor neurons fire they cause the muscle of the leg to contract and the leg will be withdrawn from the stimulus. |
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What is the polysynaptic flexor process' purpose? |
Used to withdraw a limb from adverse stimuli - such as standing on a pin. |
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What are central pattern generators? |
Mini circuits of neurons within the spinal cord that activate muscles on either sides of the body during locomotion. These vary considerably but often share common features such as the 'half-centre' organisation. |
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How do motor neurons within the central pattern generators control alternating flexion and extension? |
If excitatory neurons receive continuous inputs from the brain, they will produce bursts of nerve impulses which in turn will make the motor neuron fire. The activity of two excitatory interneurons will alternate because they inhibit each other through inhibitory interneurons, such that a burst of activity in one excitatory interneuron with cause inhibition in the other one. |
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What are the motor cortex, basal ganglia and cerebellum involved in, in terms of movement? |
The motor cortex is involved in complex movements and fine precise movement. The basal ganglia are involved in the selection and initiation of voluntary movements. The cerebellum is the major site for motor learning in the brain - it is the place where 'what is intended' is compared with 'what has happened'. It acts as an error detector. Contains around half the total number of neurons in the CNS. |
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How does the brain communicate with the motor neurons of the spinal cord? |
Axons from the brain run down through the spinal cord along two major groups of pathways. One is the lateral column of the spinal cord and the other is the ventromedial pathway. The lateral pathways are involved in the voluntary control of movements and are mostly under direct cortical control. The ventromedial pathways are predominantly involved in postural control and are controlled by the brainstem. |
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How does the cerebellum learn new and complicated motor tasks? |
When we instruct our muscles to contract in a particular way, a copy of the intended motor command is sent to the cerebellum. During the execution of the movement the resulting sensory feedback (I.e. information telling our brain what the rest of the body is doing) is also relayed to the cerebellum. The cerebellum can now compare the two - if the feedback differs from the expected movement then the cerebellum can detect the nature of the error and make appropriate adjustments. |
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What are the main types of cells in the cerebellum that control input and output? What do they use as transmitters? |
Input: mossy fibres and climbing fibres - use glutamate as a transmitter. Output: Purkinje Cells: Use GABA as a transmitter. |
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What is the cerebral cortex made up of? |
Grey matter - nerve cell bodies (outer surface) = local interneurons (e.g. stellate and granule cells) and larger excitatory pyramidal cells White matter - nerve cell axons ^opposite to the spine |
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What are the lobes of the cortex called and what are their functions? |
Frontal: voluntary motor control, personality, higher intellectual thinking, verbal communication Parietal: somatic sensation, relating body image with extrapersonal space Temporal: auditory perception, and via deeper structures (hippocampus, amygdaloid nuclei)-learning memory and emotion Occipital: visual perception. |
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What was the deal with this Phineas Gage chap? |
Man who suffered a sufficient brain injury when he was impales by a large iron bar. It is thought that he lost a significant part of his cerebral cortex. Following the injury he was reported to have a dramatically changed personality and behaviour. This accident demonstrated that the front of the brain is involves in the control of personality and emotion. |
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What is Electroencephalography (EEG) and what is it used for? |
Technique that allows electrical recordings to be made from the surface of the brain. Many electrodes are fixed in position on the head and small voltage deflections are measured between pairs of electrodes. It takes the activation of many thousands of neurons to generate an EEG potential big enough to record. Used to analyse sleep patterns or for the diagnosis of epilepsy. |
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What is a technique often used in the diagnosis of epilepsy? What will it show you that implies epilepsy? |
Electroencephalography (EEG). A trace will be shown of the neurons whose impulses are being recorded and almost all of them will be firing together - this is a generalised seizure and involves the whole cortex. A partial seizure only involves part of the cortex. |
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What causes epilepsy and what are the treatments? |
The causes of epilepsy are wide ranging and include tumours, trauma, infection or vascular disease, but often the cause is not knows. Treatments often use drugs that enhance the actions of GABA. GABA is inhibitory and can reduce the excessive excitement of neurons during epilepsy. In severe epilepsy cases, the corpus callosum can be severed surgically to reduce the spread of epileptic waveform. |
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What is positron emission tomography and how does it work? |
A scanner detects material that has been injected or inhaled to produce an image of the brain (commonly used radioactively-labelled materials include oxygen and glucose). Oxygen and glucose are used by the brain to provide energy and thus are the most abundant in areas of the brain that are active. When the radioactive material breaks down, it gives off a neutron and positron (particle with a positive charge). When a positron hits and electron, both are destroyed and two gamma rays are released. Gamma ray detectors record the brain area where gamma rays are emitted. This method allows us to view which parts of the brain are active whilst performing certain tasks.
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What is functional magnetic resonance imaging? |
fMRI - This technique relies on the fact that oxygen is carried around the body by an iron-containing protein called haemoglobin. The amount of oxygen present affects the magnetic properties of haemoglobin in different ways, which can be monitored using a magnetic field. A magnetic field from the MRI scanner causes the haemoglobin molecules to line up - yet when the field is released, they spin back into position, causing a minute radio wave (resonance), which can be detected. The increased energy use of active areas of the brain is associated with increased blood flow and altered levels of oxygen which can be detected using fMRI. |
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When it comes to speech, what are the two main areas that are active in the brain? What are their functions? |
The primary motor area - to move the mouth lips and tongue. Broca's area - important for the production of spoken words |
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What is Broca's aphasia? What is Wernicke's aphasia? |
Broca's: their speech is categorised by a severe stutter and they are able to produce only a few words, however, they are aware that they are making little sense Wernicke's: a condition where patients can usually produce spoken words, but the words they use are meaningless as Wernicke's area is damaged and they are unable to comprehend whether their speech is making sense. |
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When hearing words, what are the two areas of the cortex and what do they do? |
The auditory (hearing) cortex: hearing Wernicke's area: allows us to understand speech |
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Describe what split brain patients say they see/draw when you show them objects on either the left or the right. |
When an image of a specific object is presented to the left eye and therefore 'seen' by the right side of the brain, split brain patients cannot verbalise what they have seen. In fact they say there is nothing there. However, the left hand, controlled by the right brain, is able to draw the object or pick it up if it is put in front of them. If the same object is presented to the right eye and is therefore 'seen' by the left hemisphere they are able to name the object |
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How is it demonstrated that the asymmetry of language centres in the brain? |
There are some tasks that the right hemisphere appears better at than the left. For example, in split brain patients the right hemisphere performs better in tasks involving spatial perception such as making coherent patterns out of coloured blocks.
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What is Parkinson's disease and what are the symptoms? |
A nervous system disorder. A disease of the CNS that affects movement and speech in about 1% of people over the age of 50. The most visible symptom is the tremor. It occurs during rest, and is most common in the hands and arms, although it may affect other parts of the body. Other symptoms include: impaired initiation of movement; slowness of movements; shuffling gait, postural instability and flexed posture; mask like facial expression. |
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What causes Parkinson's disease? |
Parkinson's involves degeneration of dopaminergic cells in the substantia nigra, a part of the basal ganglia, which results in reduced levels of dopamine in the brain. The loss of dopamine causes dysfunction of the basal ganglia motor circuitry. It is not known what triggers this process but supplying the precursor of dopamine, L-DOPA can alleviate some of the symptoms on a non-permanent basis. |
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What is Alzheimer's disease and what are the symptoms? |
A progressive degenerative disease that affects around 5% of those over the age of 65 and 20% of those over the age of 80. Symptoms include loss of memory, the inability to think and understand clearly and generalised confusion. |
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What are contributing factors to the development of Alzheimer's disease? |
A single cause for Alzeimer's has not been found, but a number of factors have been identified as likely contributing factors. The diagnosis of Alzeimer's can be difficult and can only properly be made after death. However, one feature is the appearance in the brain of so called neurofibillary tangles and amyloid plaques. These disrupt the functioning of the brain and over time there is often shrinkage of brain tissue. |
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What is motor neuron disease and what are the symptoms? |
A disease characterised by progressive muscle weakness and paralysis due to the loss of motorneurons. Symptoms typically appear in mid-life and progress rapidly with death due to respiratory failure within 3-4 years of diagnosis. 90% of MND cases are sporadic - the remaining 10% are familial |
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In motor neuron disease, what are the potential disease mechanisms that are thought to contribute to death? |
Glutamate excitotoxicity, protein aggregates, mitochondrial dysfunction. |
