Use LEFT and RIGHT arrow keys to navigate between flashcards;
Use UP and DOWN arrow keys to flip the card;
H to show hint;
A reads text to speech;
97 Cards in this Set
- Front
- Back
What is a motor unit? |
nerve fibre and all the muscle fibres it innervates |
|
what is the point of innervation of a nerve and a muscle? |
The neuromuscular junction |
|
What are the two divisions of the descending motor tracts? |
Dorsolateral and ventromedial tracts |
|
What does the dorsolateral tract do? |
Control movement (normally independent movement) of limbs |
|
What does the ventromedial tract do? |
Controls posture and whole body movement and the limbs involved in these activities |
|
What are the direct and indirect innervations of the dorsolateral tract? |
DIRECT: corticospinal tracts |
|
What are the direct and indirect innervations of the ventromedial tract? |
DIRECT: ventromedial corticospinal tracts |
|
Explain the basic route of the dorsolateral tract |
80-90% of fibres decussate after the pyramids at the anterior white commissure to form the dorsolateral tract. Terminate in the CONTRALATERAL half of the spinal cord, sometimes directly on a motor neuron |
|
Explain the basic route of the ventromedial tract |
Fibres stay IPSILATERAL through the pyramids, more diffuse, axons innervate interneurons in several segments of the spinal cord |
|
Explain the basic function of the cerbellum |
Combines input from primary motor and sensory cortexes with feedback from somatosensory and vestibular systems. |
|
What is the function of the basal ganglia? |
Modulation of movement |
|
Explain the biological mechanisms of Parkinson's disease |
Degeneration of the dopaminergic neurons of the substantia nigra pars compacta leads to a dopamine deficiency. Dopamine therfore cannot stimulate the D1 (excitatory) and D2 (inhibitory) receptors on the striatum which then go on to effect the direct and indirect pathway. |
|
What is a positive symptom and what are some of the positive symptoms of Parkinson's disease? |
A positive symptom is a trait that is not normally present that is there because of the disease |
|
What are negative symptoms and what are some negative symptoms of Parkinson's disease? |
Negative symptoms are traits (normally present) that are absent due to the disease |
|
What is L-dopa? |
The chemical precursor to dopamine which is used as a treatment for Parkinson's etc because it can cross the blood brain barrier (unlike straight dopamine) and get converted to dopamine once past. |
|
What is Huntington's disease? |
A neurodegenerative disease, manifested in adulthood. It is autosomal dominant (chromosome 4). |
|
What are some of the biological mechanisms of huntington's disease? |
Degeneration of striatum (apparent enlargement of ventricles--> destruction of GAGAergic (and some cholinergic) neurons (no inhibiton) |
|
What are some of the symptoms of Huntington's disease? |
Chorea (involuntary, irregular 'dancing' movements) Altered speech and writing |
|
What is Tourette's? |
A disorder characterised by intermittent motor or verbal tics with otherwise normal cognition and sensory activity. |
|
What is the result of damage to the primary motor cortex? |
hemiplegia - weakness of the contralateral side
|
|
What is the result of damage to the higher order sensorimotor association cortexes? |
Apraxia and contalateral neglect |
|
What is ataxia? |
Inability to use visual information to guide hands |
|
What is apraxia? |
Disorder of skilled movement eg inability to move parts of the body in a purposeful manner |
|
What brain region is key for proprioception? |
Superior parietal lobe |
|
What are the three main stages of a motor state? |
Desired, predicted, estimated actual |
|
What is the mirror neuron system? |
Imagining or watching a movement activates the same part of the brain that is used to do that action --> we are sensitive to the actions of other people |
|
What is the optic disk? |
'blind spot' where axons from the optic nerve exit the eye |
|
What are cones? |
Low sensitivity, high positional acquity, low convergence |
|
What are rods? |
High sensitivity, low positional acquity, high convergence
Multiple rods converge on a single retinal ganglion cell. |
|
Explain the visual angle |
A 1cm wide object at a distance of 57cm will subtend 1 degree of visual angle |
|
Explain visual transduction |
Photoreceptors contain rhodopsin (G protein that is sensitive to light). Cell is normally depolarised and actively releases inhibitory neurotransmitter. When stimulated by light, the cell becomes hyperpolarised (less inhibition) which increases the bipolar neuron's firing. |
|
Explain lateral inhibiton and why we see Mach bands |
Light receptors have an extensive network of lateral connections. These connections inhibit adjacent neurons whilst simultaneously firing and stimulating the visual cortex. When there is a boundary between strong and weak light, the photoreceptors in the strong light are inhibited less by the receptors in the weak light (so they fire more) and inhibit the weak light receptors more (so they fire less) |
|
What happens to the medial and lateral fibres of the optic nerve when they leave the eye? |
Medial fibres decussate at the optic chiasm, lateral fibres stay ipsilateral. This means that light from a particular area in space is processed by ONE visual cortex. |
|
Explain retinotropic organisation and cortical magnification factor |
adjacent locations in the retina match adjacent locations in the cortex |
|
Explain the 6 layers of the lateral geniculate nucleus |
Top 4 layers: parvocellular |
|
Explain some features of the parvocellular pathway |
small cell bodies colour (cones) |
|
Explain some of the features of the magnocellular pathway |
large cell bodies large receptive fields achromatic (rods) |
|
What kind of receptive fields are activated by low spatial frequency? |
simple cell receptive fields with widely separated subfields |
|
What kind of receptive fields are activated by high spatial frequency? |
simple cell receptive fields with narrowly separated subfields |
|
explain some features of complex cells |
fed by a number of simple cells, it will fire if it gets any input from any contributing cells. |
|
What pathway does the magnocellular tract go through? |
Dorsal pathway - posterior parietal cortex |
|
What pathway does the parvocellular tract go through? |
Ventral pathway - inferotemporal cortex |
|
What is a cortical scotoma |
Damage to the visual cortex causes an area of loss in the visual field that may not be noticed |
|
Explain macular sparing |
Even if a scotoma covers the area around the fovea, the fovea is not effected because it is processed in the deeper areas of the cortex - 'spared' from the damage |
|
Explain blindsight |
A patient has a damaged visual cortex and a large scotoma. No conscious perception of any visual stimuli within the scotoma. Patient can still judge orientation, intercept objects etc within the scotoma |
|
What is the where vs what theory? |
Dorsal stream: visual spatial perception Ventral stream: visual pattern recognition |
|
What is the control of behaviour vs conscious perception theory? |
Dorsal (magno): visually-guided behaviour (using visual info to guide motor actions Ventral (parvo): conscious visual perception (colour, shape, orientation) |
|
What is prosopagnosia? |
Patient cannot recognise faces. Result of damage to VENTRAL STREAM. Familiar faces elicit higher GSRs which suggests a motor response. |
|
What is the role of the pina? |
collect sound waves and funnel them into the ear, help localise sound by reflecting sounds of various frequencies into the ear |
|
Explain how sound is amplified in the ear |
The tympanic window is much bigger than the oval window, a size disparity that amplifies sound 17 fold. All together = 22 FOLD AMPLIFICATION |
|
Explain how vibrations are converted to neural impulses |
Taking a cross section of the cochlea, there is a basilar membrane with specialised cells (with hair fibres on them), and a tectoral membrane resting on these hairs. The vibrations move the lymph fluid in the cochlea, which pushes these two membranes together, bending the hair cells. This causes chemical changes in the specialised cells beneath which elicits action potentials and a neural response. The auditory threshold of hair cell displacement is about 100 picometres. |
|
What is the volley theory? |
To perceive sounds of about 100-5000Hz, neurons carrying the auditory signals work together, each firing in a slightly delayed rhythm (eg one neuron fires for the 3rd, 7th, 11th etc signal). The overall effect of this is a signal of a much higher frequency (eg 500hz) than a single neuron could produce. |
|
What is place theory? |
The point of maximum displacement of the basilar membrane occurs very close to the start (to the stapes). As the vibrations travel down the membrane, the amplitude of displacement drops. Thus, areas of the membrane closer to the stapes code for higher frequency sounds whilst areas further away code for lower frequency sounds. |
|
Explain the basic auditory pathway |
Cochlea --> cochlear nerve --> superior olivary nucleus --> inferior colliculus --> MGN --> auditory cortex |
|
Explain interaural time differences |
sound doesn't travel fast enough to prevent us from picking up on minute differences in the time that the sound arrives in one ear compared to the other (coincidence wiring) |
|
Explain interaural intensity differences |
The head can cause an 'auditory shadow' which lowers the frequency of the wave as picked up by the ear on the other side of the head. |
|
explain coincidence wiring |
The nerve from each cochlea has a number of synapses within the olive (medial superior - MSO). If there is a difference in timing of the ears the signals will arrive at these synapses at different rates. The MSO firing is maximised when two signals arrive at the same time. If sound has arrived earlier in the left ear, the two signals might meet at the synapse furthest from the left ear and closest to the right and the brain can decode this to localise the sound. |
|
Explain olivary inhibiton |
To do with interaural intensity differences. Both olivary nuclei are stimulated by their respective cochlea, and also inhibit one another. If a signal is more intense in one ear, the olivary nucleus on this side can fire more strongly and also inhibit the other nucleus more robustly. This is another method of sound localisation. |
|
Where are the primary and secondary auditory cortexes located relative to each other? |
Both are in the superior temporal gyrus. The primary auditory cortex is more 'hidden' within the lateral sulcus and the secondary auditory cortex is more lateral (on the outside). |
|
Explain the two principles of organisation in the auditory cortex |
Columnar organisation: columns which respond to similar frequencies |
|
What is conduction deafness? |
Results from damage to the tympanic membrane and ossicles. DOES NOT INVOLVE NERVOUS SYSTEM eg ossicles can fuse together |
|
Explain sensorineural hearing loss |
Auditory nerve fibres are not stimulated properly. PERMANENT. Caused by infection, trauma, loud sounds, drugs (eg streptomycin) |
|
Central deafness |
Caused by brain lesions in the temporal lobes |
|
What is the purpose of the semicircular canals and what are the two key features of them? |
Semicircular canals respond to ACCELERATION Ampulae- large swelling filled with liquid |
|
What are the utricle and saccule and what covers them? |
Structures within the vestibular system covered with otoliths which respond to linear acceleration and gravity (constant) |
|
Explain the vestibulo-ocular reflex |
Turning the head stimulates the ipsilateral lateral rectus and contralateral medial rectus which keeps the eyes in the same spot. The contalateral lateral rectus and ipsilateral medial rectus are also inhibited. |
|
Explain vestibulo-ocular nystagmus |
Eyes 'jumping' forward and then tracking back to maintain distant visual images when the head is rotating about an axis |
|
What is oscillopsia? |
'Bouncing vision' |
|
What are the three components of the somatosensory system? |
Exteroceptive (outside stimuli) |
|
What are some types of cutaneous receptors? |
Free nerve endings (temp, pain) |
|
What are dermatomes? |
Areas of the skin that correspond to a specific spinal cord segment (which dorsal root the afferent fibre from that area converges on) |
|
What are the two major somatosensory pathways? |
Dorsal column medium lemniscus - information about touch and proprioception |
|
What are the three separate tracts of the anteroalteral tract? |
Spinothalamic: to ventral posterior thalamus Spinotectal tract: to tectum |
|
What is the effect of damage to S1? |
No major defecits in sensation, probably due to the numerous parallel pathways in the two systems |
|
What is the cortical representation for pain? |
No specific representation- very diffuse throughout/ S1 and S2 respond to pain but they can be removed without loss of pain sensation. Removal of entire hemisphere has little effect also. Anterior cingulate gyrus is likely to be involved in the emotional response to pain |
|
Explain briefly the descending control of pain |
Periaqueductal grey has analgesic effects. Electrical stimulation reduces pain. PAG has receptors for opitate-based pain drugs, endorphins modulate PAG activity. |
|
Compare language and communication |
Communication is simply behaviour used by one member of a species to convey information to another (eg body language, gesture, eye contact). |
|
What is aphasia? |
Loss of language processing ability after brain injury.
- developmental disorder |
|
What are the 5 classic types of aphasia? |
- Broca's (M) |
|
Explain Broca's aphasia |
Disturbance in speech production. Damage to left inferior frontal cortex. |
|
Explain Wernicke's aphasia |
Disturbance in auditory comprehension. Damage to left posterior superior temporal gyrus. |
|
Explain conduction aphasia |
Failure to repeat. Damage to arcuate fasciculus (between Broca's and Wernicke's). |
|
Explain transcortical sensory aphasia |
Disturbance of auditory comprehension. Unlike Wernicke's it has good repetition and semantic paraphasias. |
|
Explain transcortical motor aphasia |
Disturbance of initiating responses (selection defecit). Lesion of tracts superior/anterior to Broca's. |
|
How does psycholinguistics differ from classic views of aphasia? |
Does not view language in terms of production and coprehension. Emphasises language processing options- phonology, syntax, semantics |
|
What are the two elements of phonology? |
Phonetic: how phonemes are produced in different contexts (eg french vs english alphabet) |
|
What kind of aphasia has a problem with syntax? |
Broca's. |
|
Describe syntax |
methods for combining words to convey propositional meaning |
|
Describe semantics |
words and their meaning |
|
Explain how semantics and aphasia are related. |
Posterior lesions (Wernicke's aphasia) tend to show more semantic disruptions. |
|
Compare Broca's aphasia and Wernicke's aphasia in terms of classical vs psycholinguistic classification |
Broca's - CLASSIC = poor speech production PSYCHOLINGUISTIC = syntactic problems |
|
What is alexia and what are the three types? |
Disruption in reading ability |
|
What is agraphia and what are the two types? |
Agraphia - trouble spelling and or writing |
|
What are the two types of amnesia? |
Anterograde - can't form new memories after TBI |
|
What are the two types of long-term memory? |
Explicit (declarative) and implicit (non-declarative) |
|
What are the two types of explicit memory? |
Episodic (personal events) and semantic (facts) |
|
What are some types of implicit memory? |
Procedural (skills), perceptual representation
|