BECOM Exam #5 (Week 1) Flashcards
Long vs. short axon
Long axon: stimulus -> CNS (TOUCH and SMELL)
- Somatic sensation (touch, pain, etc.)
- Visceral sensation
- Olfaction
Short axon: stimulus -> signal synapses primary afferent neurons’ peripheral processes -> CNS
- Gustation (taste)
- Photoreception
- Hair cells of inner ear
Conscious proprioception (kinesthesia)
Joint position and movements – including direction and velocity
Nonconscious proprioception
Muscle spindles and golgi tendon organs (proprioception)
Pain: nociceptors (fast vs. slow)
- type of pain
- fibers
- neurotransmitters
Fast pain: sharp, localized
-myelinated Aδ fibers (glutamate)
Slow pain: dull, burning, diffused
-unmyelinated C fibers (substance P)
FUNCTION Mechanoreceptor Meissner corpuscles Merkel discs Hair follicle receptors Ruffini endings Pacinian corpuscles Muscle spindles
Meissner corpuscles (tactile shapes/surfaces) Merkel discs (tactile indentations) Hair follicle receptors (tactile in hairy skin) Ruffini endings (stretching and shapes) Pacinian corpuscles (vibrations) Muscle spindles (proprioception)
Aδ mechanical vs C-polymodal (nociceptor)
- type of pain
- temp
Aδ mechanical: encapsulated/sheathed and detect discrete nocicept stimuli (pinprick)
-fast/acute pain
-cold
C-polymodal: free nerve ending that detect tissue damage)
-chronic pain
-heat
dorsal column (medial lemniscus system) mediates what? and cell body location
Tactile sensation and conscious proprioception
-cell bodies: dorsal root ganglia
Meissner’s, Pacinian, or joint receptor (dorsal column (medial lemniscus system)) pathway
primary neuron runs to dorsal root gang -> gracillis or cuneatus (decussation) -> VPL of thalamus -> sensory motor cortex
-same side of the body up through the spinal cord and crosses over at medulla
non conscious propreception pathway (posterior spinocerebellar tract)
muscle spindles and Golgi tendons enter and run to cerebellum without crossing (inferior peduncle)
- proprioception
- do not cross
non conscious propreception pathway (anterior spinocerebellar tract)
Golgi tendons enter and cross at level on the spinal cord and run up to pons where it crosses again and continues to cerebellum (superior peduncle)
- Proprioception including skin stretch sensation
- crosses twice
Cerebellar ataxia
Form of uncoordinated gait disturbance due in part because of the cerebellum not processing proprioceptive stimulus appropriately
Friedreich’s or spinocerebellar ataxia
Inherited neurodegenerative disease particularly affecting SPINOCEREBRAL tracts (proprioceptive tracts)
Symptoms: near total lack of upper limb coordination and reeling, wide-based gait
Special sensation with longest Axon
smell (olfactory)
Neospinothalamic tract
enters at spinal cord level and synapse with 1. substantial gelantinosa or 2. nucleus proprius -> crosses to lateral finiculus continues and synapsis at VPL of thalamus -> sensory cortex
Anterolateral cordotomy
a lesioning the spinalthalamic tract in order to stop pain transmission
Hyperalgesia and chemicals involved
enhancement of pain sensation (abnormally increased sensitivity to pain)
- Either activate nociceptors themselves
- Lower nociceptor threshold
- Histamine, Substance P, Serotonin, Bradykinin increase ones sensitivity to pain
Allodynia
pain occurs after repetitive but typically non-painful stimulation
-ex. sunburn, sore throat
Causalgia
Burning sensation caused by increased sympathetic efferent activity after peripheral nerve injury
Paresthesia
Pricking, tingling, numbness, tingling, burning of skin with no apparent cause
-caused by nerve compression or PVD (peripheral nerve disease)
Meralgia paresthetica
compression of the lateral cutaneous nerve of the thigh causing numbness, tingling down the outside of the thigh
Tonic receptors
slow/non adaptive receptors (continue stimulation)
-proprioception, chemoreceptors, nociceptors, Golgi tendon apparatus, baroreceptors, receptors in vestibular apparatus (position)
Phasic (rate) receptors
fast adapting (loss of stimulation)
- Display on/off response (feel hat when 1st put on and when taken off but not while wearing)
- pacinian corpuscles most fast adapting
Lateral inhibition
Strongest neuron not only sends stimulus but also inhibits the surrounding weak stimuluses (via interneurons - neurons between neurons)
-allows brain to localize stimulus
First intention vs second intention wound healing
First Intention -> results in thin scar
- Simplest type of cutaneous wound repair
- Healing of a clean, uninfected surgical incision
- Approximated by surgical sutures
Second Intention -> substantial scar
- Excisional wounds
- Repair process is more complicated
- Create large defects on the skin surface
- Extensive loss of cells and tissue
anterolateral (spinothalamic) pathway transmits
pain thermal crude touch tickle/itch sexual sensation -very little point discrimination
Pain neurotransmitters
neurotransmitters:
- substance P (C fibers)
- glutamate: activation of AMPA/NMDA (A delta)
Fast pain conduction route (anterolateral tract)
1st order: terminates in dorsal horn (lamina marginalis)
2nd order: crosses at lamina marginalis and ascend to thalamus and
Slow pain conduction route (paleospinothalamic pathway)
1st order: terminates in substantia gelatinosa (laminae II and III) in dorsal horn
2nd order: 1/4 to thalamus the rest terminate widely in the brainstem (reticular nuclei -> reticular activating system, tectum of midbrain, periaqueductal grey)
Pain suppression neurotransmitters
- encephalin (pre- and post-synaptic inhibition of type C and Ad fibers)
- serotonin
methanol stimulate
capsaicin (chilli)
TRPM8
TRPV1 (Ca2+ influx)
-(mild activator), adenosine, bradykinin, piperine, camphor, some venoms and jellyfish extract
MECHANISM
Prostaglandin
Anesthetics
Opiates
Prostaglandin: enhances/facilitate pain transmission
Anesthetics: blocks Na+ channels -> pain no AP
Opiates: inhibit at synapses via pre/post synaptic inhibition
Normal BMI
18.5-25
Marasmus
low protein and low carbohydrate intake leading to emaciation
Kwashiorkor
Calorie deprivation may be nearly adequate, but protein deprivation is severe
- distended abdomen bc depletion of visceral protein
- edema bc low albumin level = low oncotic pressure
- fatty liver due to sparing of subcutaneous fat
Cachexia
is loss of weight, muscle atrophy, fatigue, weakness and significant loss of appetite in someone who is not actively trying to lose weight
- PEM caused by advanced cancer, AIDs
- PIF and proinflammatory cytokines cause skeletal muscle breakdown via NF-κB activation of ubiquitin proteasome pathway
Anorexia nervosa vs. bulimia
Anorexia nervosa: self-induced starvation that can lead to arrhythmiaandsudden death
Bulimia: binging on food and then induced vomiting (frequent vomiting leads to electrolyte imbalances)
Folic Acid (B9)
Megaloblastic anemia: bc enough protein but cells cannot divide
Cobolamin (B12)
- pernicious anemia: B12 malabsorption due to def. in parietal cells that release intrinsic factor
- neurologic dysfunction
- megaloblastic anemi: needed for folate to function properly
Pyridoxine (B6)
Coenzyme especially for amino acid metabolism
- active compound is pyridoxal phosphate (PLP)
- microcytic anemia
- ONLY water soluble vitamin with sufficient toxicity -> sensory neuropathy
Thiamine (B1)
Function in decarboxylation reactions related to the TCA cycle
- Wernicke-Korsakoff syndrome: memory loss and loss of balance due
- Beriberi: wet = cardiovascular, dry = nervous system
Niacin (B3)
Coenzymes in oxidation reduction reactions
-Pellagra: triple D (dermatitis, dementia, diarrhea)
Riboflavin (B2)
Biotin (B7)
Pantothenic acid (B5)
Riboflavin (B2): coenzymes of oxidation reduction reactions
Biotin (B7): coenzyme of carboxylation reactions
Pantothenic acid (B5): functions to transfer acyl groups
Vitamin A (retinol) and too much?
Maintenance of normal vision: synthesis of rhodopsin (night vision) and photopsins (color vision)
-buildup of keratin debris in small opaque plaques(Bitot spots)
Cell growth and differentiation: orderly differentiation of mucosal epithelium (def. causes epithelia metaplasia and keratinization)
Hypervitaminosis A: toxic level may produce liver cirrhosis
-synthetic retinoids in pregnancy should be avoided because of teratogenic effects
Vitamin D
maintain plasma calcium by absorption from intestines and kidneys
- Deficiency causes bone demineralization (rickets in children and osteomalacia in adults)
- Excess causes hypercalcemia and renal stones
Vitamin C
antioxidant and hydroxylation of collagen:Inadequately hydroxylated fibroblast procollagen cannot acquire stable helical configuration (in blood vessels, predisposes to hemorrhages)
- Def.: scurvy
- Toxicity: iron overload (inc absorption of iron)
Vitamin K
Vitamin E
Vitamin K: coenzyme for clotting factors
Vitamin E: deficiency is rare and may present with red blood cells sensitivity to oxidative stress (antioxidant)
Pear shape vs apple shape
Pear shape: lower risk of metabolic disease
Apple shape: excess central abdominal fat has an increased risk of morbidity and mortality
POMC/CART vs. NPY/AgRP
POMC/CART: promote energy expenditure and weight loss via MSH hormone -> TRH and CRH
-leptin activates (secreted by adipocytes to dec appetite)
NPY/AgRP: promote food intake and weight gain via Y1/5 receptor -> MHC and orexin
- gherlin activates (released by stomach to inc appetite)
- pYY, leptin, amylin inhibit (causes satiety)
Adiponectin
fat burning molecules that direct fatty acids to liver for B oxidation and decrease glucose production
Contraction of ciliary muscles results in
decreased tension on suspensory ligament and, in turn, allows the lens to increase its thickness, thereby focusing light rays from a NEAR object onto retina
constrictor vs dilator muscles of the iris (control)
constrictor: parasympathetic control
dilator: sympathetic control
glaucoma
Aqueous humor is constantly secreted and it is drained into the spaces of fontana, if drainage is block -> pressure on optic nerve resulting in glaucoma
presbyopia
cataract
loss in lens elasticity as one ages resulting in farsightedness
cataract: opacification of the lens
neural and non neural part of the retina
non-neural: pigment epithelium -> single layer of light-absorbing, pigmented cells lying adjacent to the choroid
neural: photoreceptors lie deepest within the retina and interdigitate with the pigment epithelium
- contains neurons
retinitis pigmentosa
retinal detachment
retinitis pigmentosa: debris from photoreceptor cells accumulates between the photoreceptor cell layer and the pigment epithelial cell layer (normally phagocytosed by pigmented epithelial cells)
retinal detachment: detachment between the pigment epithelial cell layer and the photoreceptors
rods vs cones
Rods: found around the periphery of the eye and are sensitive to light brightness (used to see in dim light)
Cones: found in the center of the eye and are used to confer high visual sharpness
first order vs second order neurons of the eye
-pathway of light transmission
First-order neuron: bipolar cell (lies within retina)
Second-order neuron: ganglion cell (join to form optic nerve)
-light hits rods and cones -> bipolar cells -> ganglion cells
Horizontal cells vs Amacrine cells
Horizontal cells modulate transmission between photoreceptors and bipolar cells
Amacrine cells modulate transmission between bipolar cells and ganglion cells
Fovea
contain mainly rods that are directly exposed to light because of displacement of the others layers of the non neural part of the retina
Optic Disc or Papilla
where unmyelinated optic nerve fibers exit from the retina
-contains no photoreceptors -> blind spot
night blindness cause
On absorbing light, rhodopsin is broken down into retinal and opsin. After absorbing light, rhodopsin is then restored by a series of chemical reactions, some of which depend on vitamin A
-def. in vitamin A results in night blindness
color blindness
absence of red, blue, or green cones
disc edema, papilledema, or choked disc
- optic nerve is surrounded by the dura as well as the arachnoid and pia mater
- increased intracranial pressure can exert pressure via the cerebrospinal fluid-filled subarachnoid space onto the optic nerve
Thalamic lesion result
complete all sensory loss (touch, pain, temp) on contralateral side of body
Lateral Pontine lesion result
- ipsilateral complete loss of facial sensory
- contralateral anterolateral (pain, temp) sensory loss
Medial Medullary lesion results
- no face sensory loss
- contralateral dorsal/post. column (vibration, touch, proprioception)
pretectal area (light reflex) pathway
some optic nerve fibers branch off and terminate at the Edinger-Westphal nucleus (pretectal area) which mediates pupillary light reflex (constriction)
- Edinger-Westphal nucleus -> pregang parasymp (oculomotor n.) -> ciliary gang -> postgang parasymp (short ciliary n.) -> constrictor muscle
- one eye constricting will cause the other eye to also constrict
damage to temporal lobe
will effect Meyer’s loop resulting in obstruction of superior visual field
homonymous vs heteronymous
homonymous: same part of the visual field in each eye
- obstruction post. to optic chiasm
heteronymous: part of the visual field lost in each eye is different
- obstruction ant. to optic chiasm
damage to optic chiasm
right eye: loss of left visual field
left eye: loss of right visual field
-bitemporal hemianopsia
damage to right optic tract
loss of left visual field for left and right eye
Pupillary Dilation Reflex pathway
post. hypothalamus -> ciliospinal center (C8) (pregang) -> superior cervical gang and synapse -> nasociliary and long ciliary nerves (carotid plexus) -> constrictor muscles
dilator muscle vs constrictor muscle
d
Accommodation Reflexes pathway
accommodation of lens, constriction of pupils, convergence of eyes
- occipital cortex -> accommodation center (oculomotor nuclei) -> then
- Edinger-Westphal (lens and pupil change) nucleus ->pregang parasymp (oculomotor n.) -> ciliary gang -> postgang parasymp (short ciliary n.) -> constrictor muscle
- Somatic nuclei (convergence) -> medial rectus muscle
Horner syndrome
miosis, mild ptosis (drooping of the eyelid) and anhidrosis (loss of sweating)
-lesions involving the lateral medulla; cervical spinal cord injuries, tumors, or syringomyelia; trauma to T1 and T2 ventral roots; cervical sympathetic trunk involvement by pulmonary carcinoma; and diseases of the internal carotid artery
Path of light in the eye:
Cornea (2/3 of refractive power occurs here) Aqueous humor Lens Vitrous humor Retina
Route of aqueous humor
Flow through the pupil -> angle of anterior chamber -> trabecular meshwork -> canal of Schlemm -> aqueous veins -> choroidal plexus
-iredial crypts absorption some aqueous humor (iris)
purpose of pigmented layer
Prevents light scattering
Reduces the risk of choroidal melanoma
Storage of vitamin A (required to make photopigments)
Phagocytosis
cGMP phosphodiesterase (PDE5)
Metarhodopsin II -> transducen -> cGMP phosphodiesterase -> breaks down cGMP -> closure of the Na+ gates -> hyperpolarization -> cessation of glutamate release from the receptor
Rhodopsin kinase
inactivates metarhodopsin II
dark adaptation
In dark (dim light), more cis retinal is formed from vitamin A -> more photopigment-protein combination -> enhanced sensitivity -takes time, why it takes a while before you can see better in the dark
In light rhodopsin is broken down and stored as vitamin A (trans retinol) -FASTER OTHERS: -pupil size -Ca2+ indirectly regulates Ca2+ channels
Light through retina
- ganglion cells
- amacrine cells - Bipolar cells
- horizontal cells - Rods/Cones
- Pigmented epithelium (absorbs light so its not bouncing around eye distorting image, phagocytosis, stores vitamin A)
macula brain part
most posterior part of visual cortex
each optic tract, lateral geniculate nucleus and visual cortex receives information relating only to the contralateral half of the visual field This combination of images from both eyes is necessary for
stereoscopic vision (depth perception)
myopia and cause
near sightedness
cause: over powerful cornea/lens, eye too long of axis
hypermetropia and cause
far sightedness
-short eye axis
Presbyopia
Cycloplegia
Anisometropia
Presbyopia: hardening of lens causing loss of lens accommodation
Cycloplegia: loss of accommodation bc ciliary m. paralysis
Anisometropia: two eyes have unequal refractive power
Descending pain modulation pathways
Periaqueductal gray matter -> nucleus raphe manus -> down spinal cord -> interneurons at dorsal horn
OR
locus ceruleus neurons in upper pons -> down spinal cord -> interneurons at dorsal horn
thalamus blood supply
perforating branches of posterior cerebral artery and posterior communicating artery
ventral anterior (VA) nuclei
where basal ganglia can exert control over movement
- medial segment of globus pallidus (3) and terminates-> principal part
- pars reticulata of substantia nigra (4) and terminate -> magnocellular part
ventral lateral (VL) nuclei
receives information from ipsilateral GPe, SNr and contralateral dentate nucleus
ventral posterior (lateral, VPL; and medial, VPM) nuclei
- ventral posterolateral nucleus
- ventral posteromedial nucleus
general sensory information from contralateral half of body
ventral posterolateral nucleus (VPL): -> trance and limbs
- spinothalamic tracts
- medial lemniscus
ventral posteromedial nucleus (VPM):
-trigeminothalamic tracts
to —> primary somatosensory cortex
Medial Geniculate Nucleus
Receives ascending fibers from -> inferior colliculus of midbrain -> primary auditory cortex (Transverse temporal (Heschl’s) gyrus)
Anterior Nuclear Group
mammillary bodies –(mamillothalamic tract)–> ANG -> cingulate gyrus
Involved in:
- control of instinctive drives (e.g., parenting)
- emotional aspects of behaviors (e.g., fear)
- memory
Medial Nuclear Group controls
efferent to prefrontal cortexs
-mood and emotions
Broca’s area
-brodmann’s area
speech production (can’t talk but can understand speech)
- area 44, 45
- found on dominant side, non dominant side responsible for variation in tone
wernicke’s area (Auditory Association Cortex)
understanding spoken word (can talk but meaningless speech)
-found on dominant side, non dominant side appreciation of subliminal meanings and humor
Layer III
Layer IV
Layer V
Layer III: commissural fibers
Layer IV: termination for afferent fibers from specific thalamic nuclei
Layer V: projection fibers to extracortical targets (basal ganglia, thalamus, brain stem and spinal cord)
-location of BETZ CELLS
precentral gyrus
- location
- brodmann’s area
- afferent fibers coming from
primary motor cortex: motor control to contralateral half of body
- anterior to central sulcus
- area 4
- ventral lateral nucleus of the thalamus
premotor cortex
- location
- brodmann’s area
less focused movements, posture, preparation of movements
- anterior to primary motor cortex
- area 6
- includes SMA (postural control)
Frontal Eye Field
- location
- brodmann’s area
- lesion
Controls voluntary conjugate deviation of the eyes, as occur when scanning the visual field
- inferior portion of premotor cortex
- area 8
- unilateral damage to this area causes conjugate deviation of the eyes towards the side of the lesion
Prefrontal Cortex
Has cognitive functions that include:
- Intellect
- Judgment
- Predictive faculties
- Planning of behavior
Left Frontal Lobe Lesions
- Partial seizures: Paroxysmal jerking movements of the contralateral limbs are termed ‘simple motor’ or ‘Jacksonian’ seizures
- Sensory/motor deficit: contralateral hemiplegia
- Broca’s aphasia: Speech is produced with great effort and poor articulation
Alzheimer’s disease
- atrophy of the temporal and parietal lobes and the limbic system
- disorientation in space, and loss of language (aphasia) and memory (amnesia)
General paralysis of the insane (GPI)
-both frontal lobes are destroyed
total alteration of personality with loss of judgment
-planning and insight, and bizarre and uncharacteristic behavior
Postcentral Gyrus
-brodmann’s
somatosensory cortex: sensory to contralateral half of body
-Brodmann’s areas 1, 2 and 3
Right parietal lobe lesions vs. left parietal lobe lesions
SAME
-partial seizures: paroxysmal attacks of sensory disturbance affecting the contralateral side of the body (simple sensory seizures)
-sensory/motor deficit: contralateral hemisensory loss and an inferior visual field loss
DIFFERENT
RIGHT: psychological deficit: an inability to copy and construct designs because of spatial disorientation (constructional apraxia)
LEFT:Psychological deficit: inability to name objects (anomia) and a loss of literacy, with inability to read (alexia), to write (agraphia) and to calculate (acalculia)
Left Temporal Lobe Lesions
- Partial seizures: paroxysmal attacks of unresponsiveness (absences), purposeless behavior (automatism), olfactory and complex visual and auditory hallucinations, and disturbances of mood and memory (déjà vu)
- Sensory/motor deficit: contralateral superior visual field loss
- Psychological deficit: speech that is fluent and rapid but contains word errors (paraphasia) and is incomprehensible
Occipital Lobe Lesions Cause
-Partial seizures: paroxysmal visual hallucinations of a simple, unformed nature, such as lights and colors (simple partial seizures)
-Sensory/motor deficit: contralateral visual field loss (contralateral homonymous hemianopia)
Bilateral occipital lobe lesions lead to:
-Bilateral occipito-parietal lesions can spare elementary vision, but prevent the recognition and depiction of objects (apperceptive visual agnosia)
spatial summation vs temporal summation
spatial summation: multiple nuerons firing causing AP
temporal summation: 1 neuron firing multiple times causing AP
C fibers and Adelta fibers terminate where in the dorsal horn
C fibers terminate in substantia gelatinosa
Ad fibers terminate in lamina marginalis
Glutamate in hypersensitivity (hyperalgesia)
High glutamate primes neuron to express NMDA and inc AMPA resulting in any release of glutamate causing an exaggerated response
Pos. Romberg test issue
Patients with dorsal column (medial lemniscal) tract dysfunction can stand still properly with eyes open
With eyes closed, they fall
abnormal nystagmus cause
eye tracking finger slowly but stops tracking for a moment, then snaps to finger again
-CN VIII issues
TRPM8
- inward cations (Na+ and Ca++)
- sensative to temperatures between 10-35 degrees Celsius
- Menthol activates TRPM8
Convergence high vs low
high: decrease localization
low: increase localization
- convergence can be from multiple sources (3 different neurons or multiple synapses from one neuron)
Trigger pain:
Trigger pain: bradykinin, serotonin, histamine, K+, ACh and proteolytic enzymes
Increase pain sensitivity: Substance P and prostaglandin
A alpha fibers:
A beta fibers:
A delta fibers:
C fibers:
- A alpha fibers: proprioception
- A beta fibers: touch
- A delta fibers: pain (acute)
- C fibers: pain (chronic)
- 1 > 2 > 3 > 4 speed of transmission
Reticular nucleus interaction with thalamus
sends inhibitory GABA to thalamic nuclei (regulatory input to thalamus)
Primary auditory cortex brodmann’s
41 and 42
eye constriction vs. dilation
Constriction: open angle, inc surface area for iridial crypts
Dilation: closed angle
Rhodosin
- proteins
- unstimulated form
Light sensitive pigment in rods
- scotopsin + retinal
- unstimulated form: cis
Rhodospin break down
bathorhodopsin (partially split rhodopsin) -> decays in ns to lumirhodopsin -> metarhodopsin I -> metarhodopsin II -> complete split to all-trans retinal and scotopsin
-metarhodopsin II active form
Retinal isomerase
recycles all-trans back to cis retinal
Horizontal cells
Bipolar Cells
Amacrine Cells
Horizontal cells: lateral inhibitory cells that provide contrast
-primary lateral inhibition
Bipolar Cells: inhibitory and excitatory cells that sharpen retinal image (photoreceptor cell -> bipolar cell)
Amacrine Cells: Interneurons between bipolar and ganglion cell
-some lateral inhibition
Ganglion Cells:
Neurotransmitters
- Glutamate is secreted by rods and cones
- GABA, ACh, glycine, dopamine and indolamine in amacrine cells play inhibitory roles
Ganglion Cells (M and P)
-1 to 1 in fovea (sharp vision)
-200 to 1 in peripheral retina (light sensitivity)
-Few % of ganglion cells are sensitive to light and have melanopsin -> circadian rhythm regulation
M: sensitive to low contrast and rapid movement visual signals (not sensitive to color)
P: fine details, edges, color discrimination (sensitive to color)
Upper visual field pathway
sweep into temporal lobe forming Meyer’s loop
-Damage to temporal lobe can effect meyer’s loop (sup. visual field)
Miosis
ptosis
Miosis: pupil constriction
ptosis: drooping of eye
