n165 quiz 3

somatosensory system

cutaneous perception of touch and pain, proprioception ability to sense position of body and limbs, and kinesthesis ability to sense movement of body and limbs.

skin

protects against germs, excretes water, converts vitamin d, regulation of temp, and transmits sensation. split into epidermis, basement membrane, dermis, then subcutaneous tissue. theres also either glabrous skin and hairy skin.

specialized receptors

mechanoreceptors glabrous skin merkel’s disk fine details SA, meissner’s corpuscle hand grip control RA, ruffini’s cylinder stretching SA, pacinian corpuscle vibrations RA, and hairy skin hair follicle receptor. pain and temp receptors more ancient free nerve endings.

3 types of pain

acute nociceptive pain signals damage to skin, chronic inflammatory pain caused by damage to tissues and joints releasing chemicals, and chronic neuropathic pain caused by damage to the peripheral or central nervous system.

spinal cord

extends from medulla oblongata in brainstem to the lumbar region of the vertebral column inside gray matter outside white matter contains incoming somatosensory and outgoing motor nerves thru spinal nerve that feeds into the gray matter using separate dorsal root ganglion and dorsal root or ventral root. CNS starts right before ganglion otherwise its periphery and the sympathetic sits right outside the spinal column. contains posterior columns controlling touch vibration pressure joint position that become medial lemniscus in brainstem to thalamus then s1; spinocerebellar tract muscle fiber tension joint position to cerebellum; lateral and anterior spinothelamic tract pain temp and crude touch pressure to thalamus.

peripheral nerve

axons are positioned in somatotopic body maps with bundles of axons that are surrounded by myelin sheaths called fascicles. peripheral nerves can be so large that blood vessels run thru them for oxygenation.

meninges of brain in the spinal cord

dura mater, subdural space, arachnoid mater, subarachnoid space, pia mater

spinal reflex pathway

instantaneous reflex of sensory receptors feeding into sensory neurons that signal motor neurons to perform muscle contractions. muscle spindle contains somatosensory stretch receptor that signals thru sensory neurons in dorsal root to spinal cord gray matter and synapse alpha motor neuron in ventral root to contract the quads.

somatosensory pathways to cortex

fine touch dorsal column- medial lemniscus system DCML first order neuron goes to posterior columns then the medulla where it synapses to second order neuron crosses over goes thru the midbrain then synapses to third order neuron at the thalamus and crosses in cortex. pain and temp spinothalamic tract first order neuron synapses to second order neuron crosses over to lateral spinothalamic tract then up thru medulla and midbrain where it synapses to third order neuron in the thalamus and crosses in cortex.

pain matrix

signals from nociceptors travel up the spinothalamic pathway and activate subcortical areas like the hypothalamus limbic system and thalamus and cortical areas like s1 and s2 in the somatosensory cortex the insula and the anterior cingulate cortex. amygdala, hypothalamus, and insula located deep within the cortex while s1 and frontal located at the surface

somatosensory agnosia / tactile agnosia

inability to identify an object by touch on single hand possibly from damage to unilateral opposite s1. more specific tactile agnosias inability to determine aspects of object

cotard syndrome

delusional belief that one is dead does not exist is putrefying or has lost their blood or internal organs. associated with depression schizophrenia capgras bipolar migraines and meds like acyclovir. possible disconnect between sensation face perception and emotional cortex with treatment by electroconvulsive shock therapy ECT

congenital analgesia

either insensitivity to pain where painful stimulus isnt perceived or indifference to pain where they can perceive the stimulus but lacks an appropriate response. possibly caused by increased endorphins from natural opioids or a mutation in sodium channels of pain receptors.

chronic pain

pain that extends beyond the expected period of healing. 10-55% of ppl in various countries have chronic pain, over 100 million americans 1/3 of country, treatment alone costs over 600 billion in US annually and still not very good, 5-8 million rely on opioids for long term pain management

motor cortex

associative, supplementary to plan and coordinate complex sequences of movement just prior to activity and premotor to plan movement based on sensory cues with basal ganglia and control of trunk muscles, primary motor cortex to control the final execution of movement, and then posterior parietal to transform sensory info into motor commands of body and objects in space. motor cortex signals thru pyramids in corticospinal tract to cross 80% to the lateral CS tract for limb motor neurons or 20% to anterior CS tract for trunk motor neurons. anterior cerebral artery supplies medial leg areas, middle cerebral artery supplies lateral face torso arm, and internal carotid artert supplies to the anterior and middle cerebral

motor neurons

upper motor neurons originate its cell body in m1 of the cerebral cortex and carries motor info down to a specific spinal cord level where it can peripherally output for motor control. lower motor neurons have its cell body in the spinal cord and brings nerve impulses from the upper motor neurons out to the muscles. upper damage function goes up lower damage function goes down.

motor cortex injury

hemiplegia total paralysis of the arm, leg, and trunk on the same side of the body as each other. hemiparesis weakness of the arm, leg, and trunk on the same side of the body as each other. note cranial nerves separately control head and neck.

neglect syndromes

anosognosia patient unawareness of and denies disability confabulation may be associated with paralysis usually from right dorsal parietal damage. also associated with blindness in anton’s syndrone from dorsal occipital damage and eds. hemispatial neglect patients unaware of the world on one side of space often including anosognosia usually also from damage to right dorsal parietal.

gerstmanns syndrome

damage to inferior part of dominant parietal usually a left sided stroke and may be developmental. experience finger agnosia may extend to body parts, problems with left right differentiation, dyscalculia, dysgraphia, and anosognosia.

apraxia

lesion in parietal usually dominant side. experiences disorder of motor planning and loss of ability to carry out learned purposeful movements despite the desire and capability to do so. rehab treatment. ideomotor, ideational, limb-kinetic, constructional, oculomotor, and verbal types.

basal ganglia

group of cell bodies below cortex interconeccted with the cortex, thalamus, and brainstem. functions in motor control, cognition, emotions, and learning via motor, executive, limbic, and oculomotor loops. motor loop has excitatory direct and inhibitory indirect pathway where dopamine plays a key role in activation and inhibition.

basal ganglia movement disorders

decreased movement hypokinetic like parkinsons with problems in direct excitatory via loss of dopamine in basal ganglia causing akinesia muscle rigidity and rest tremors. treatment with medication l-dopa that affects the whole brain, fetal neural tissue graft thats invasive wtih legal restrictions, or deep brain stimulation of one basal ganglia side to invasively effect contralateral body. increased movement hyperkinetic like huntingtons caused by autosomal dominant genetic neuro disorders and loss of cortical neurons esp in inhibitory basal ganglia characterized by 40s, jerky movements, and decline in mental; and hemiballismus caused by damage to mange of the BG nuclei esp in subthalamic nucleus resulting in problems of indirect inhibitory characterized by involuntary flinging treated by deep brain stimulation, surgery to remove parts of BG, and drugs that block dopamine or anti seizure and psychotic.

outer ear

folds of pinna gathers and focuses sound energy on tympanic membrane esp important for vertical sound localization

middle ear

contains malleus, incus, and stapes ossicles that further amplify movement of the tympanic membrane onto smaller oval window. open to environment leads to eustachian tube of the back of the noise allows outside air to enter. bones allow easier conversion of compression from air of outer and middle to cochlear fluid in inner ear via a lever action. tensor tympani muscle attached to malleus to tune and protect while the stapedius mescle is attached to the stapes and oval window contracting in response to loud noises so less sound is transmitted in acoustic reflex.

hearing loss

otosclerosis abnormal growth of bone of the middle ear which can result in hearing loss. low frequencies lost first with higher affected later treated with hearing aids or removal of stapes bone with addition of a fat plug along the bone of the inner ear. sensorineural caused by problems in the vestibulocochlear nerve, inner ear, or central processing centers of the brain and may be genetic or acquired ranging from mild to total deafness. treated with hearing aids or cochlear implants. cortical deafness is a rare sensorineural hearing loss caused by bilateral damage to a1 where patients are completely deaf but retain some auditory reflexes caused by stroke trauma birth defects. auditory agnosia rare in the auditory system likely from damage to anterior temporal ‘what’ lobes where patients can hear sounds and describe them using unrelated terms but unable to recognize them and still do not report feeling deaf. milder versions may include pure word deafness/auditory verbal agnosia, nonverbal auditory agnosia, amusia, and word meaning deafness

inner ear

two major parts cochlea organ of hearing and vestibular system organ of balance. round window is a small membrane covered opening btwn the fluid cochlea and middle ear to dampen pressure caused by sound waves. fluid thruout its departments contains basilar membrane important in sound transduction from air to fluid by using a narrower and stiffer base that encodes high frequency and a wider more flexible apex that encodes low frequency. each individual frequency of a complex tone is pulled apart and identified by its position along the membrane and the circuitry of the auditory neurons its connected to.

organ of corti

up and down movement of basilar membrane moves the embedded auditory nerve fibers when stimulated by environmental signals that share this signaling to the tectorial membrane so it can move back and forth and transduce sound waves into neural signals. hair cells contain mechanoreceptors on the tips of its cilia.

hair cells

inner converts sound to nerve signals 10k with graded receptor potential. outer performs acoustical pre amplification 30k important for extended hearing range and improved frequency selectivity

auditory pathway to cortex

sound from ear travels thru auditory nerve to the cochlear nucleus where its sent to the superior olive nucleus with binaural inputs and left/right sound localization, then the inferior colliculus integrates sound info, the medical geniculate nucleus of the thalamus to relay frequency intensity and binaural info, and finally onto the auditory cortex where audio is segregated by ear inputs and may play a role in up-down localization.

auditory localization

lateral superior olive input from ipsilateral is excitatory while contralateral is inhibitory. medial superior olive acts as coincidence detector where anatomical diffs in connectivity allow neurons to be sensitive to sources from a particular location

auditory cortex

core including a1 thalamic input, pure tones, tonotopic sharp freq tuning, and on heschl’s gyrus with many interhemispheric connections. belt has coarser tonotopy and parabelt is mostly coarse tonotopy projects widely to parietal, temporal, and frontal regions.