midterm
Asomatagnosia
Loss of awareness or denial of ownership of a body part (often after parietal lobe damage).
Nociceptor
Specialized sensory receptor that detects tissue damage or potential damage (pain).
Analgesia: Reduced or absent pain
Algesia: Sensitivity to pain
Referred pain
Pain felt in a different location than its source (e.g., heart attack → arm pain).
Phantom pain
Pain perceived in a missing or amputated limb.
Dorsal column–medial lemniscus pathway (DCML)
Carries touch, vibration, and proprioception:
receptors → spinal cord → medulla → thalamus (VP) → somatosensory cortex
Mechanoreceptor
Receptor that responds to physical pressure or distortion (touch, vibration).
Pacinian corpuscle
Mechanoreceptor specialized for detecting deep pressure and vibration.
Dermatome
Skin area supplied by a single spinal nerve.
Shingles
Painful viral infection (reactivation of varicella virus) affecting specific dermatomes.
Neglect syndrome
Failure to attend to one side of the body/space (usually right parietal damage → neglect left side).
Periaqueductal gray (PAG)
Midbrain region that controls pain suppression via descending pathways.
Afferent pain gates
Incoming pain signals traveling from body → spinal cord → brain.
Descending pain gates
Brain pathways that inhibit/block pain signals at the spinal cord.
Endorphins
Natural opioids that reduce pain by binding opioid receptors.
Naloxone
Opioid antagonist that blocks endorphins/opioids, reversing analgesia/overdose.
Substance P
Neurotransmitter that transmits pain signals.
Capsaicin
Chemical in chili peppers that activates pain receptors (heat/burning sensation).
Histamine
Chemical released during injury/allergy → causes inflammation & itching.
Bradykinin
Chemical that promotes inflammation and activates nociceptors.
Pain & placebo
Expectation of relief can reduce pain via brain mechanisms (endorphin release).
Melzack & Wall Gate Control Theory
Pain signals can be blocked or amplified in the spinal cord depending on competing input (e.g., rubbing reduces pain).
Topographic mapping
Spatial organization of sensory input in the brain (body mapped onto cortex).
Cortical map plasticity
Brain’s ability to reorganize sensory maps after injury or experience.
The four classes of sensory axons
A-alpha: fastest, motor/proprioception
A-beta: touch
A-delta: fast sharp pain
C fibers: slow dull pain
VP nucleus (ventral posterior nucleus)
Thalamic relay for body sensory info → somatosensory cortex
Warm-sensitive cells
Respond to increases in temperature.
Cold-sensitive cells
Respond to decreases in temperature.
Infrasound
Sound < 20 Hz (below human hearing).
Ultrasound
Sound > 20,000 Hz (above human hearing).
Middle ear ossicles
Malleus, incus, stapes—amplify sound vibrations.
Cochlea
Fluid-filled inner ear structure that converts sound → neural signals.
Basilar membrane
Vibrates at different locations depending on sound frequency.
Organ of Corti
Structure containing hair cells that transduce sound.
Inner hair cell
Primary sensory receptor for hearing → sends signals to brain.
Spiral ganglion
Neuron cell bodies that carry auditory info to brain.
Medial geniculate nucleus (MGN)
Thalamic relay for hearing → auditory cortex.
Pheromones
Chemical signals released by one individual that affect behavior/physiology of others of the same species.
Set-point
Body’s regulated “target” weight it tries to maintain.
Eating disorders
Disruptions in eating behavior (e.g., anorexia, bulimia, binge eating).
LH (lateral hypothalamus)
“Hunger center” → stimulates eating.
VMH (ventromedial hypothalamus)
“Satiety center” → stops eating.
Arcuate nucleus
Hypothalamic region integrating hunger signals.
Neuropeptide Y (NPY)
Strongly stimulates appetite.
Agouti-related protein (AgRP)
Increases hunger and food-seeking.
CART
Suppresses appetite.
Osmotic thirst
Triggered by cell dehydration (high salt concentration).
Antidiuretic hormone (ADH)
Reduces urine → conserves water.
Renin
Enzyme released by kidneys → starts cascade to increase blood pressure.
Angiotensin
Hormone that stimulates thirst and vasoconstriction.
Aldosterone
Hormone that increases sodium retention (and water).
Subfornical organ (SFO)
Brain structure that detects blood osmolarity and triggers thirst.
Hyponatremia
Dangerously low sodium levels (often from excess water intake).
Preoptic area (POA)
Hypothalamic region controlling body temperature + sleep initiation.
Narcolepsy
Disorder with sudden sleep attacks; linked to low hypocretin.
Circadian rhythms
~24-hour biological cycles (sleep, hormones, etc.).
Zeitgebers
External cues (light, food) that reset circadian rhythms.
SCN (suprachiasmatic nucleus)
Main biological clock in hypothalamus.
Hypocretin / Orexin
Promotes wakefulness and stabilizes sleep-wake states.
Adenosine
Builds up during wakefulness → promotes sleep pressure.
Desynchronized sleep (REM)
Active brain, dreaming, muscle paralysis.
Synchronized sleep (NREM)
Slow-wave, deep sleep.
PGO waves
Brain waves during REM linked to dreaming/visual activity.
Purpose of dreams
Likely involved in memory processing, emotional regulation, and brain activity maintenance.
Sleep disorders - Conditions disrupting normal sleep
(insomnia-
narcolepsy:
sleep apnea,
Serotonin → sleep regulation, mood
Dopamine → arousal, motivation
Norepinephrine → alertness
GABA → promotes sleep (inhibitory)
Acetylcholine → REM sleep + wakefulness