Spinocerebellar: subconscious proprioception. NO decussation, cerebellum
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Describe the main features of the corticospinal tract
Transmits motor signals from cortex to spinal cord
Decussates in medulla
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Describe the essential differences between afferent and efferent nerves
AFFERENT: sensory neurons that carry nerve impulses from sensory stimuli to CNS
EFFERENT: motor neurons that carry nerve impulses to muscles
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Name 2 proprioceptors
Muscle spindles (length) and golgi tendon organs (tension)
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Compare the sensory receptive fields in different parts of the body
Fingers: shorter :. more neurons supplying small area of skin. HIGHER RECEPTOR DENSITY
Back: one neuron covers a lot more area :. touch is far less localised. LOWER RECEPTOR DENSITY
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Explain what a two-point discrimination test is and how to perform it correctly
Measures tactile spatial acuity
Callipers used to assess ability of individual to determine between 2 points
Minimum distance at which subject can make distinction\= threshold
Higher density of receptors in skin + smaller receptive field\= finer discrimination for mechanoreception (i.e. finger pads)
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List the changes that occurs after nerve injury
1. distal part begins to degenerate as its no longer connected to the cell body
2. schwann cells unwrap themselves+ divide to form continuous line of cells lining distal endoneurial sheaths
3. proximal cut ends of nerve fibre form growth cones + grow back down inside sheath with help of cell adhesion molecules
4. actin contracts to pull cone along towards denervated region
5. macrophages + microglia engulf debris and injury site becomes walled off by glial scar
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Define what is meant by glial scar
Reactive cellular process following injury to the CNS
Acts as a physical and chemical barrier
Roles: - engulf debris - seals lesion site - repairs blood-spinal cord barrier - expresses chemicals that inhibit axon growth
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What is Wallerian degeneration?
Active process of retrograde degeneration of distal end of axon following nerve lesion
Occurs 7-21 days after injury
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Outline the features of UMN lesions
Present deep tendon reflexes (hyperreflexia)
Babinski positive (dorsiflexion + fanning of foot when scraped)
Spastic paralysis
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Outline the features of LMN lesions
Muscle atrophy
Absent deep tendon reflexes (hyporeflexia)
Fasciculations
No Babinski
Flaccid paralysis
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Describe the function of muscle spindles
Located within muscle fibre
Senses muscle stretch/ lengthening
Sends nerve impulse to spinal cord which immediately synapses with LMN to act on muscle
Results in muscle shortening aka contraction
Also involved in reciprocal inhibition by inhibiting (relaxing) antagonist muscle
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Describe the function of Golgi Tendon Organs
Located in tendon
Senses tension as tendon doesn't change in length
Inhibits further muscle action to prevent damage to muscle and tendon
Known as autogenic inhibition
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List the 5 components of the reflex arc
1. receptors
2. afferent neuron
3. integrating centre e.g. spinal cord
4. efferent neuron
5. effector
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Describe the patellar tendon reflex
1. activation of receptor when GTO is stretched
2. action potentials fired by 1a afferents which synapse with motorneurones in spinal cord (excitatory and inhibitory)
3. hamstrings inhibited via inhibitory interneuron + quadriceps muscle contracts
*MONOSYNAPTIC*
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What are polysynaptic reflexes?
When afferents and efferents are connected via interneurons
e.g. withdrawal reflex is intended to protect the body from damaging stimuli. Don't only send signals to agonist muscle but also antagonistic muscle and associated centres in brain to process what occurred
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Outline the clinical testing of the extraocular muscles
SR + IR: abduct eye then look up/down
SO + IO: adduct eye then look up/down
MR + LR: unopposed abduction or abduction of eye
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Which foramina do the CNs pass through?
I: cribriform plate
II: optic canal
III: superior orbital fissure
IV: superior orbital fissure
V1: superior orbital fissure
V2: foramen rotundum
V3: foramen ovale
VI: superior orbital fissure
VII: internal acoustic meatus
VIII: internal acoustic meatus
IX: jugular foramen
X: jugular foramen
XI: jugular foramen
XII: hypoglossal canal
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Explain the role of the different components of the spinothalamic tracts in sensation and pain
Anterior- carries sensory modalities of crude touch and pressure
Lateral- carries sensory modalities of pain and temperature
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Briefly describe the clinical manifestations of lesions of the spinal cord
Small central: *centrally crossing fibres of spinothalamic tract*, loss of pain + temperature sensitivity
Most common in CERVICAL cord
Large central: loss of pain + temp sensitivity, AT LEVEL OF LESION-\> LMN damage, BELOW LEVEL-\> UMN damage
Some Anatomists Like Freaking Out Poor Medical Students
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What does it mean when the vocal cords increase in length?
Higher pitch
Controlled by cricothyroid + supplied by external (superior) laryngeal nerve
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Through which bone does the facial nerve travel through before exiting the skull via the stylomastoid foramen?
Petrous temporal bone
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What artery supplies the anteromedial portion of the cerebrum?
Anterior cerebral artery
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How is ghrelin released in the stomach?
At the fundus of the stomach by the enteroendocrine cells
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What are the differences between Wernicke's aphasia, Broca's aphasia and conduction aphasia?
Wernicke's: can speak fluently but in a meaningless way
Broca's: can understand speech but cannot articulate properly- often having halted speech
Conduction: impaired ability to read out loud and repeat back speech
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Which sensory nerve ending is responsible for the continued dull pain and what spinal tract does this sensory information pass through?
C nociceptor fibres
Spinothalamic
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Which structure passes through foramen rotundum?
CN V2
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Through what mechanism of action do beta-adrenergic receptor antagonists help with in the treatment of glaucoma?
Decrease aqueous humour production
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How does ghrelin affect neurons that release NPY (Neuropeptide Y), AgRP(Agouti-related peptide), POMC (proopiomelanocortin) and CART (Cocaine and Amphetamine related transcript neurons)?
ACTIVATES: NPY and AgRP -releasing neurons
INHIBITS: POMC and CART
:. inducing hunger
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State the main regions of the anterior triangles of the neck
Main areas- submandibular, submental, carotid and muscular
Separated from posterior triangle by SCM
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State the boundaries and contents of the carotid triangle
Boundaries: - superior\= posterior belly of digastric muscle - lateral\= medial border of SCM - inferior\= superior belly of omohyoid muscle
Contents: common carotid artery, internal jugular vein, hypoglossal and vagus nerves
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List all the suprahyoid and infrahyoid muscles
Supra: *superheroes do much good* - stylohyoid - digastric - mylohyoid - geniohyoid
Results in: - contraction of pupils (miosis) - drooping of superior eyelid (paralysis of LPS-\> ptosis) - sinking of eye - vasodilation + absence of sweating (anhidrosis)
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Define the term 'grandmother cell'
A neuron that only responds to a highly specific stimulus :. fires significantly more when presented with an image of person grandmother or similar
Also called Jennifer Aniston neuron
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Explain the functions of the posterior parietal cortex
Receives input from a collection of sensory areas + other regions of the brain
Role in spatial cognition and motor control of eyes + extremities
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Describe the functions of the inferior temporal cortex
Visual processing and visual object recognition
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Describe the functions of the dorsolateral prefrontal cortex
Executive function, response selection and working memory
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Partial optic nerve lesion
Ipsilateral scotoma
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Optic chiasm lesion
Bitemporal hemianopia
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Optic tract lesion
Homonymous hemianopia
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Complete optic nerve lesion
Blindness in that eye
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Describe the accommodation reflex
Response to focusing on near object, then looking at distant object
3 main components: - thickening of lens (ciliary muscles contract) - convergence (bent angle of eyes) - pupil constriction
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Define photo-transduction
Process through which photons are converted into electrical signals
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Describe the main difference between rods and cones
Rods: scotopic vision-\> dim/dark light
Cones: bright light
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Describe cataracts
Lens become opaque/cloudy
- develops slowly - reduces levels of antioxidants in aqueous humour - risk factors: diabetes, hypertension, exposure to excess UV light/microwaves
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What are the 3 main neurons in the path from photoreceptor to optic nerve?
1. photoreceptors
2. bipolar cells
3. ganglion cells
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Describe the 4 parts of the internal carotid artery
Cervical Petrous (in carotid canal) Cavernous (sinus) Cerebral
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What does the anterior cerebral artery supply?
Medial frontal and parietal lobes
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What does the middle cerebral artery supply?
Lateral surface of cerebral hemispheres
Except superior frontal + parietal lobes and inferior temporal lobe
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Name the branches of the vertebral artery
Anterior spinal a. Posterior inferior cerebellar a. Basilar a. (brainstem + cerebellum) Anterior inferior cerebellar a. Superior cerebellar a. Posterior cerebral a.
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Outline the primary function of the circle of Willis
Provides redundancy :. permits circulation even if a part of the circle is occluded via communicating a.
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Describe the hypothalamo-hypophyseal tract
Collection of nerves, endocrine tissue and blood vessels in the hypothalamus and pituitary gland
Secrete:
- hormones that directly produce responses - hormones that regulate synthesis + secretion of hormones of other glands
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Describe 6 hypothalamic releasing hormones
Corticotrophin RH-\> adrenocorticotrophic H
GnRH-\> LH + FSH
Thyrotropin RH-\> thyroid stimulating H
Growth hormone RH-\> GH
Growth hormone inhibiting hormones
Prolactin inhibiting factor
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Describe the hypophyseal portal system
Capillary bed in infundibulum connecting hypothalamus to anterior pituitary
Allows hypothalamic hormones to be transported to anterior pituitary without entering systemic circulation first
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Describe the afferents of the hypothalamus
NST- blood pressure, gut distension
Reticular formation- body temperature
Retina- sleep/wake cycle
Limbic + olfactory system- smell, emotion
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Explain the structure of the BBB and its functional significance