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NSCI 110:Exam 3
Exploring Neuroscience |
Definition: undulating displacement of molecules caused by changing pressure
-has 3 physical attributes: frequency, amplitude, & complexity
-travel @ a fixed speed of 1100ft/s
-sound energy varies in wavelength |
frequency |
Definition: # of cycles a wave completes within a given amount of time
-sounds w/ low pitch = slow wave frequency
-sounds w/ high pitch = fast wave frequency |
amplitude |
Definition: perceived intensity or loudness; height of wave
-sounds w/ single frequency = pure tones
-sounds mix w/ wave frequencies = complex tones |
pinna |
funnel-like external structure of the outer ear designed to catch sound waves and funnel them into the external ear canal |
ossicles |
3 bones commonly known as the hammer, anvil, & stirrup
reality = malleus, incus, & stapes
-attach the eardrum to the oval window |
cochlea |
inner-ear structure containing the auditory receptor cells
-has 2 sets of hair cells:
i) 3500 inner hair cells & 12000 outer hair cells
-only inner hair cells are auditory receptors |
Sound Perception Pathway |
1. pinna catches soundwaves and funnels them into the external ear canal
2. waves are amplified and directed to the eardrum, causing it to vibrate
3. this causes the ossicles to vibrate
4. ossicles amplify and convey the vibrations to the oval window (hitting against it)
5. vibration of oval window sends waves through cochlear fluid
6. causes the basilar & tectorial membranes to bend
7. causes the cilia of the outer hair cells embedded in the tectorial membrane to bend, generating APs |
hair cells |
sensory neurons in the cochlea tipped by cilia
-movement of cilia changes hair cell's polarization & its rate of neurotransmitter (NT) release
-movement towards tallest = depolarization: Ca2+ channels open, release NT onto dendrites of the cells that form the auditory nerve-->generating more nerve pulses
-movement towards shortest = hyperpolarization: cell membrane & NT decrease therefore decreasing the activity in auditory neurons |
basilar membrane |
receptor surface in the cochlea that tranduces sound waves into neural activity
-all parts of basilar bend in response to sound waves of any frequency
-maximally responsive to frequencies that are mapped as the cochlea uncoils
-high frequency sounds peak at thick (narrow) part of the basilar membrane (BM)
-low frequency sounds peak at thin (wide) part of BM |
wernicke's area |
secondary auditory cortex located at the rear of the left temporal lobe that regulates language comprehension |
lateralization |
process by which functions become localized primarily on one side of the brain |
horizontal orienting |
azimuth detection |
vertical orienting |
elevation detection |
ventral audition pathway |
decodes complex sounds or auditory-object recognition, including the meaning of speech sounds |
dorsal audition pathway |
plays a role in integrating auditory & somatosensory info to control speech production |
broca's area |
anterior speech area in the left hemisphere that functions w/ the motor cortex to produce the movement required for speaking |
wernicke's aphasia |
people who can speak fluently, but their language is confusing and makes little sense
fluency, but poor comprehension |
broca's aphasia |
people who can't speak despite normal comprehension and intact physiology
good comprehension, inability to speak fluently |
phoneme |
simplest unit of sound |
morpheme |
smallest meaningful unit of language |
semantics |
meanings of words, sentences, & phrases |
syntax |
grammar & sentence structure |
lexicon |
words available |
prosody |
characteristic melody & rhythms of speech |
discourse |
conversation at level of social interaction |
neologism |
made up word |
major components of movement control |
1) cerebrum: conscious control
2) brainstem: automatic movement control
3) spinal cord: automatic movement control |
Integration of sensory & motor processes |
1. visual information required to locate the target (visual = LGN) (auditory = MGN)
2. Frontal lobe motor areas plan & command the movement (knowing this = parietal lobe)
3. spinal cord carries info to target
-motor neuron in motor cortex sends signal down spinal cord & affects muscles
4. sensory feels target/object & sends info to sensory cortex (layer IV)
5. spinal cord carries info to the brain
6. basal ganglia judges grasping/movement forces & cerebellum corrects movement errors
7. sensory cortex receives message that the target has been moved/grasped/reached |
motor sequence |
determined by the prefrontal cortex; movements are performed as sequences, with one held in readiness while an ongoing sequence is being completed |
frontal lobes |
(i) prefrontal cortex: plans complex behavior based on a goal
(ii) premotor cortex: produces the appropriate motor sequences
(iii) primary motor cortex: specifies how each movement is carried out |
mirror neurons |
found in premotor cortex
-a neuron that is active during the observation or action of a specific task
-active upon thinking about the task |
brainstem |
species-typical behaviors (e.g. swimming, grooming, nest making, chewing, defensive mechanisms) |
spinal cord |
facilitates complex motor patterns (e.g. scratching, walking) |
damage to section of brain |
no rehab: reduction of damaged area
rehab: enlargement/accommodation of other areas
this is evidence of plasticity |
cortical spinal tract |
main efferent pathway
-focus on layer V
-axons descend into brainstem; some go to brainstem nuclei; emerge on ventral surface of brainstem (bump on each side)
-conscious control over skeletal muscles |
corticobulbar tract |
conscious movement of eye/jaw/face muscles
-most likely to descend and synapse in the brainstem
-doesn't make sense to travel down spinal cord since muscle targets are above neck |
lateral cs tract |
does cross over
-branches at the medulla to cross over to opposite side
-moves contralateral digits and limbs
-synapses w/ interneurons & motor neurons
-interneurons synapse w/ motor neurons that innervate muscle
-motor neurons project to muscles of the body
-originates in neocortex and terminates in spinal cord |
ventral cs tract |
does not cross over
-moves (same-side) muscles of the midline body (trunk)
-originates in neocortex and terminates in spinal cord |
limb muscles |
they are paired
-extensors: move (extend) limb away from the trunk
-flexors: move limb towards trunk
-coordinated movement requires extensor contraction as flexor relaxes or vice-versa |
tectospinal tract |
important in dorsal tectospinal tract
-input from visual system to coordinate head & neck movements to visual stimuli |
rubrospinal tract |
origin: red nucleus
-input from motor cortex & cerebellum to control arm muscles |
red nucleus |
restores some motor function lost as a result of cs system damage (pyramidal tract lesions) |
agonist muscle |
more work for movement
increase firing rate of agonist motor neuron |
antagonist muscle |
goes against movement
decrease firing rate of antagonist motor neuron |
basal ganglia & movement force |
input from:
1. all areas of the neocortex, limbic cortex, & motor cortex
2. the nigrostriatial dopaminergic system from the substantia nigra
-project back to the motor cortex via thalamus & substantia nigra
-range of functions in addition to movement: habit learning, motivation, emotion
-if caudate putamen damaged = unwanted writhing & twitching (dyskinesias) occurs |
hyperkinetic symptom |
increase in movement; writhing & twitching movements called dyskinesias (i.e. Huntington's Disease) |
hypokinetic symptom |
decrease in movement; ridgity & difficulty initiating and producing movements (i.e. Parkinson's Disease) |
flocculus |
small, dense lobe involved in eye movements and balance
-divided in 2 hemispheres
-lateral parts: movement of limbs, hands, feet, & digits
-ventral parts: movement of face & midline of body
-primary fissure: separates anterior/posterior lobes
-postereolateral fissure: separates flocculus from corpus cerebelli |
cerebellar peduncles |
cerebellum connects to brain via these
superior: main output of cerebellum (goes mostly to midbrain)
middle: info from contralateral cerebral cortex
inferior: input carrying sensory info of where the body is in space |
main functions of cerebellum |
1. timing: movements & perceptions
2. movement accuracy
-error correction: compares intended movement w/ actual movement and makes the necessary adjustments |
layers of the cerebellar peduncles |
innermost: granule cell layer (small, tightly packed neurons)
-input from mossy fibers--> project to purkinje cells
middle: purkinje cell layer (1-cell thick)
-output for entire cerebellar cortex; inhibitory connections onto cerebellar deep nuclei
outer: molecular layer (mostly granule cell axons & purkinje cell dendrites) |
inferior olive |
climbing fibers-->excitatory input to purkinje cells
brainstem's largest nuclear group
-tracts originate here to form part of the inferior cerebellar peduncle |
nocioception |
perceive pain, temperature, itch
-free nerve endings
-consists of small neurons w/ little to no myelination |
hapsis |
-perceive fine touch & pressure
-mechanical stimulation of the hair or tissue
-consists of large myelinated neurons |
proprioception |
perception of the body in space
-sensitive to the stretch of muscle, muscle tendons, & joint movement
-consists of the largest myelinated neurons |
rapidly adapting receptor |
responds briefly to the beginning & end of a stimulus
ex) haptic receptors: meissner's corpuscles, pacinian corpuscle, & ruffini |
slowly adapting receptor |
responds as long as the stimulus is present
ex) merkel's receptor or hair receptors |
lateral ST tract |
nocioception (pain, T, itch) |
dorsal ST tract |
-hapsis (fine touch & pressure)
-proprioception (body in space) |
medial lemniscus |
tract formed by axons of second order neurons from the dorsal column nuclei |
spinal nerves |
cervical
thoracic
lumbar
sacral |
prefrontal cortex |
plans complex executive behavior
-decision making
-damage to this region often results in breaking social and legal rules due to faulty decision making |
premotor cortex |
received instructions from prefrontal cortex
-produces appropriate complex movement sequences
-damage to this region = sequences can't be coordinated and the goal can't be reached
-organizes motor sequences via mirror neurons |
primary motor cortex |
receives organized motor sequences from premotor cortex
-specifies how each movement is carried out |
simple movement |
blood flow increases in the hand area of the primary motor cortex as an indiv presses down on a lever w/ their finger |
movement sequence |
blood flow increases in the premotor cortex as an indiv performs a sequence of movements |
complex movement |
blood flow increases in the prefrontal, temporal, & parietal cortexes as an indiv uses a finger to trace a route in a maze |
psychosomatic pain |
emotional component of pain |
neurogenic pain |
neuron damaged; no specific nocioceptor involved |
neuropathic pain |
sensitization causes increased perception of pain, if persistent--->chronic pain |
referred pain |
site of cause is not the site of pain perception
-nociocpetors detect damage/potential damage
-may be responsive to mechanical, chemical, or thermal stimuli
-pain in body organs interpreted as body surface pain |
pain perception |
. initial response (damage)
2. inflammation: sensitized polymodal neurons, resulting in hyperalgesia (decrease pain threshold)
(i) reticular formation & PAG (arousal)
(ii) tectum (orienting responses)
(iii) amygdala (emotional responses)
(iv) hypothalamus (hormonal & cardiovascular responses) |
visceral pain |
visceral pain 1. wide variance on sensitivity
-hollow vs. solid organs
-hollow organs are more sensitive to pain
2. pain & injury relationship is weak
-GI tract: burning is not perceived, but twisting is excruciating
-hear: extremely sensitive to decrease in blood flow
3. exaggerated reactions: sweating, pale, blood pressure fluctuates
4. diffuse (poorly localized), referred pain to periphery
-there isn't a separate visceral pain pathway; signals converge onto afferents |
gate theory of pain |
activities in different pathways compete
-haptic-proprioceptive stimulation can reduce pain perception by activating inhibitory interneurons that reduce nocioception |
periaqueductal gray (PAG) |
electrical stimulate decreases pain
PAG neurons excite brainstem pathways
-these excited pathways project to dorsal spinal cord to inhibit lateral st tract neurons |
globus pallidus internal (GPi) activation pathways |
if direct pathway is activated = GPi is inhibited & the pathway is allowed to produce movement
-if indirect pathway is activated = GPi is activated & it inhibits the thalamus which blocks movement |
glabrous skin |
skin on the palms of the hands & feet, the lips, & the tongue is hairless--sensitive to a range of stimuli |
nocioception pathways |
free nerve endings for pain: SLOW
-free nerve endings for temp: SLOW
damage/irritation to dendrite or surrounding cells releases chemicals stimulating the dendrite to produce APs |
hapsis pathways |
messners corpuscle = touch: RAPID
-pacinian corpuscle = flutter: RAPID
-ruffini corpuscle = vibration: RAPID
-merkel's receptor = steady skin indentation: SLOW
-hair receptors = flutter or steady skin indentation: SLOW |
proprioception pathways |
muscle spindles = muscle strech: RAPID
-golgi tendon organs = tendon stretches: RAPID
-joint receptors = joint movement: RAPID |
dorsal-root ganglion neuron |
contains one long dendrite; only the tip is responsive to sensory stimuli
-every spinal segment is characterized by a dorsal-root that contains neurons of many types:
- each type responds to a particular kind of somatosensory info |
dorsal spinothalamic (st) tract |
formed by haptic-proprioception axons located in the dorsal part of the spinal cord
1. these axons synapse in the dorsal-column nuclei at the base of the brain
2. then cross over to other side of brainstem & ascend to medial lemniscus pathway
3. then synapse in ventrolateral thalamus which carries afferent info about body senses to somatosensory cortex
*dorsal-root ganglion neurons, dorsal-column nuclei neurons, & thalamic neurons are required to carry this info to the brai |
lateral spinothalamic (st) tract |
-formed by nocioceptive axons
1. synapse w/ neurons in the dorsal part of the spinal cord & these neurons send their axons to the other side of the spinal cord
2. on ventral side--> form ventral ST tract
3. which joins the medial lemniscus in the brainstem
4. is then send to the ventrolateral thalamus
5. somatosensory cortex |
monosynaptic reflex |
simple spinal reflex that is formed by a single synapse between a sensory neuron and a motor neuron |
affective aggression |
associated with fear/threat reactive; defensive
-correlated with medial hypothalamus, dorsolateral PAG; cerebral cortex is not required |
predatory aggression |
proactive; premeditated aggression
-correlated with lateral hypothalamus or ventral PAG; cerebral cortex is required |
gonadal hormones |
-androgens & estrogens alter 5-HT (serotonin) receptor expression
-high testosterone lowers stress perception overall BUT-->testosterone increases responsiveness to social threats |
oxytocin |
regulates maternal behavior (maternal aggression)
-depends on dam's level of anxiety
-oxytocin sensitizes the amygdala |
emotions |
cognitive interpretations of subjective feelings |
motivation |
behavior that seems purposeful and goal-directed |
smell |
receptor surface: olfactory epithelium
-composed of receptor cells and support cells
-each receptor cell sends a process that ends in 10-20 cilia into a mucous layer (olfactory mucosa)
1. chemicals in air diffuse into layer interacting with cilia
-->metabotropic activation--> AP
2. olfactory receptor cells project to olfactory bulb ending in dendrites called glomeruli
3. then synpase w/ dendrites of mitral cells
4. then send axons from olfactory bulb to range of forebrain areas |
orbitofrontal cortex (OFC) |
area of the prefrontal cortex located behind the eye sockets; receives projections from dorsomedial nucleus of the thalamus
-plays a role in emotional/social behaviors as well as eating |
vomeronasal organ |
organ that receives input of pheromones
-connects to amygdala & hypothalamus
1. detected by organ
2. then sends axons to accessory olfactory bulb
3. connects mainly w/ amygdala & hypothalamus--> plays a role in reproductive & social behaviors |
5 types of taste |
. sweet
2. sour
3. salty
4. bitter
5. umami = savory |
taste |
receptors: microvilli
-base of taste bud is contacted by branches of afferent nerves that come from cranial nerves: 7 (facial), 9 (glossopharyngeal), & 10 (vagus)
-facial nerve--> anterior 1/3 of tongue
-vagus nerve--> posterior 1/3 of tongue
-glossopharyngeal nerve--> other parts of mouth
-3 nerves form main gustatory nerve-->SOLITARY TRACT
upon entering brainstem it divides in 2:
1. travels via posterior medulla to ventroposterior medial nucleus of the thalamus-->breaks in two
(i) primary somatosensory cortex--> localizes taste & textures
(ii) region rostral to 2nd somatosensory cortex in the gustatory cortex of the insula-->activates OFC = flavor
a) right side: pleasant
b) left side: unpleasant
2. projects through the pons to the hypothalamus & amygdala
-these inputs play a role in feeding behavior |
innate releasing mechanisms (IRM) |
activators for inborn, adaptive responses that aid an animal's survival |
regulatory behaviors |
behaviors motivated by an organism's survival
-controlled by homeostatic mechanisms
-hypothalamus maintains homeostatis by acting on both the endocrine system & ANS to reg. internal enviornment |
non-regulatory behaviors |
neither required to meet the basic survival needs of an animal nor controlled by homeostatic mechanisms
-includes sexual intercourse behaviors to parenting to curiosity |
factors that control hypothalamus hormone-related activity |
1. feed back loops: hypothalamus initiates a cascade of events-->secretion of hormones, but pays attention to how much is released
-when a certain level is reached it stops hormone stimulating signals
2. neural control: regulates other brain structures (i.e. limbic system & frontal lobes)
3. experimental responses: in response to experience, neurons undergo structural & biochemical changes |