Unit 2 Study Guide Questions Flashcards
physiological sensory processing, driven by sensation
Bottom-up processing
perception is driven by cognition
Top-down processing
Olfactory Transduction Pathway
inhale odorants –> bind to olfactory receptors (on cilia) –> trigger cell changes –> action potential down axon –> project info about pattern of activation to olfactory bulb –> bypasses thalamus –> some info goes to amygdala and hypocampus; some info goes to olfactory cortex where messages coded by location –> perceptions of different smells
Taste Transduction Pathway
tastants enter taste pores (taste bud openings) in oral cavity –> interact with taste receptors –> taste nerves on each side of tongue (chorda tympani, glossopharyngeal, greater superficial petrosal, superior pharyngeal) –> solitary nucleus (in brain stem) –> crosses over to other side of brain –> ** thalamus** –> gustatory cortex
What are the four taste nerves?
- chorda tympani
- glossopharyngeal
- superior laryngeal
- greater superficial petrosal
Vision Pathway
light hits pupil–> focused by lens and cornea onto –> rods and cones at back of retina –> reduces NT release, hyperpolarizes receptor –> passes through horizontal/bipolar/amacrine cells –> ganglion –> produce action potentials –> down axon via optic nerve –> leave eye through optic disk –> half of axons from each eye cross to other side of brain at optic chiasm –> portion of axons synapse in lateral geniculate nucleus (in thalamus); the rest go to primary visual cortex (in occipital lobe)
Auditory Pathway
Air to pinna –> through ear canal –> sound waves vibrate tympanic membrane –> ossicles (malleus, incus, stapes) amplify sound waves –> vibrations through cochlea’s fluid-filled tunnels (scala vestibule, scala tympani, cochlear duct) –> excite auditory nerve –> hair cells/receptors (receptors) move due to tectorial membrane (mechanical stimulation) –> ion channels open –> depolarization due to influx of K+ –> GLUT and ACh released to cochlear nerve afferents –> crosses midline at cochlear nucleus –> superior olivary nucleus –> inferior colliculus –> medial geniculate nucleus –> auditory cortex
Somatosensory pathway
Skin/touch receptors send action potentials –> unipolar axon (in dorsal root ganglion) –> enter spinal cord dorsal horn –> joins dorsal column in spine –> in medulla, periphery axon makes synapse to neuron of dorsal column nuclei –> sends axon across midline –> up to thalamus –> thalamus receives info contralaterally –> send info to primary somatosensory cortex
particular neurons that are, right from the outset, labeled for distinctive sensory experiences
labeled lines
region of space in which stimulus will alter neurons’ firing rate
receptive field (why photoreceptors only transmit info as light)
progressive loss of receptor response as stimulation is maintained
sensory adaptation
recept in which frequency of action potentials drops rapidly as stimulation is maintained
related to sensory adaptation
phasic receptor
receptor in which frequency of action potentials declines slowly or not at all as stimulation is maintained
tonic receptors
Pain Pathway
Damaged cells release substances –> stimulate nociceptors –> action potentials in periphery –> excite blood cells and mast cells/produce inflammation/ mast cells release histamine –> info from periphery enters through **dorsal root ** and synapses on neurons in dorsal horn –> pain fibers release glutamate NT and substance P neuromodulator in spinal cord –> then dorsal horn cells send info across midline and up to thalamus –> form spinothalamic system (different than somatosensory)
In spinothalamic pathway:
Nerve fibers send axons into dorsal horns of spinal cord synapse on spinal interneurons project across midline ascend to thalamus
Hypovolemic thirst pathway
triggered when fluid volume is low
cardiac baroreceptors –> via vagus nerve –> brain stem –> Preoptic Area (POA)–>
kidney baroreceptors –> angiotensin II restricts blood vessels, reabsorbs water –> subfornical organ –> Preoptic Area (POA) –>
From Preoptic Area (POA) –> paraventricular and supraoptic nucleus –> vasopressin –> water conservation
From Preoptic Area (POA) –> Hypothalamic thirst network –> drinking behavior
Osmotic thirst pathway
triggered when solute concentration is too high
Osmosensory neurons in OVLT –> POA –>
- hypothalamic thirst pathway –> drinking behavior
- paraventricular and supraoptic nucleus –> vasopressin –> water conservation
Hunger hormones
leptin: in fat cells, provide info about long-term energy stores
ghrelin: in stomach; appetite stimulant
PYY3-36: in intestines; appetite suppressant
Cholecystokinin: in gut; acts on vagus nerve to inhibit appetite
When blood sugar is low, signals release of ——-
Explain cycle.
glucagon
glucodetectors in liver recognize low blood sugar –> signal *glucagon release from pancreas –> breaks down glycogen to glucose (glycogenolysis) –> released into circulatory system –> raises blood sugar
When blood sugar is high, signals release of ——-. Explain cycle.
insulin
glucodetectors in liver detect high blood sugar –> pancreas releases insulin –> helps get glucose into cells (acts as receptor “key”) AND signals liver to store excess glucose as glycogen (glycogenesis) –> lowers blood sugar in circulation
Thermoregulatory system for mammals
Thermoreceptors (TRP receptors) in skin, body core, hypothalamus detect temp and transmit info –> spinal cord –> brainstem –> hypothalamus
Body temp outside of set zone?
neural regions initiate physiological and behavioral responses to return temp to set zone
Physiological:
- increase temp: shiver, fluff out fur, decrease blood flow to skin
- decreatse temp: pant, sweat
Behavioral:
- increase or decrease temp: change exposure of body surface, change insulation, change surroundings
Hunger in hypothalamus (brain lesions)
VMH lesion: caused obesity due to increase in food intake; thought to be satiety center
LH lesions: caused weight loss due to refusal to eat; thought to be hunger center
BUT weight/eating went back to normal after awhile = neither VMH or LH is solely responsible for appetite signaling
Neither —– or —- is completely responsible for hunger or satiety.
LH or VMH
——– drive hypothalamic appetite control
How?
hormones
- arcuate nucleus circuit integrates hormones
- digestive organs and fat tissue release hormonal signals (energy balance)
What do neurotrophins do?
- axon guidance
- cell growth/survival
- stimulate synaptogenesis
