Lesson 1 - General Senses Flashcards
(147 cards)
1
Q
receptor
A
structure specialized to detect a stimulus
2
Q
some receptors are _____ _____ _____
A
bare nerve endings
3
Q
sense organs
A
structure that combines nerve tissue surrounded by other tissues that enhance response to a certain type of stimulus
4
Q
accessory tissue of a sense organ may include… (3)
A
added epithelium, muscular, or connective tissue
5
Q
sense organs range in _____ and _____
A
size, complexity
6
Q
transduction
A
the conversion of one form of energy to another
7
Q
a fundamental purpose of any sensory receptor
A
convert stimulus energy into nerve signals
8
Q
two stages of the sensory process
A
- sensation
- perception
9
Q
sensation
A
sensory receptor detects stimulus and creates a small, local, electrical charge called the receptor potential
10
Q
if the receptor potential is high enough…
A
the neuron fires action potentials and nerve signals to the brain
11
Q
perception
A
conscious experience and interpretation of a stimulus
12
Q
not all sensations lead to _____
A
perception
13
Q
sensory receptors transmit four kinds of information
A
modality, location, intensity, and duration
14
Q
modality
A
type of stimulus or the perception it produces
15
Q
what is modality determined by?
A
which region of the brain is “wired” to receive the information
16
Q
information is sent to the CNS via _____ _____
A
labeled line
17
Q
labeled line
A
the electrical signal of each modality is passed along a chain of neurons to the CNS so that the information is separated from each other
18
Q
location
A
where a stimulus is located
19
Q
what is location encoded by?
A
which nerve fibers are firing
20
Q
receptive field
A
the area within which a sensory neuron detects stimuli
21
Q
the size of the receptive field determines what?
A
resolution; the ability to distinguish between two close-together stimuli
22
Q
intensity
A
strength of stimulus
23
Q
intensity is encoded in three ways
A
- which fibers respond
- how many fibers respond
- hot fast the fibers are firing
24
Q
- intensity - which fibers respond (2)
A
weak stimulus can only activate most sensitive neurons
strong stimuli also activates less sensitive neurons with a higher threshold
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2. intensity - how many fibers respond
more intense stimuli activate more neurons
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3. intensity - how fast fibers are firing
as stimulus intensity rises, firing frequency increases
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duration
how long a stimulus lasts
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what is duration encoded by?
changes in firing frequency over time
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sensory adaptation
if a stimulus is prolonged, firing of the neuron gets slower over time and we become less aware of it
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phasic receptors (2)
adapt quickly; burst of signals when stimulus starts, then reduces or stops signaling even if stimulus continues
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examples of phasic receptors (3)
smell, hair movement, cutaneous pressure
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tonic receptors (2)
adapt slowly; action potentials continue more steadily while stimulus is present
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examples of tonic receptors (4)
body position, muscle tension, joint motion, pain
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classification of receptors by stimulus modality (5)
1. photoreceptors
2. thermoreceptors
3. nociceptors
4. chemoreceptors
5. mechanoreceptors
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photoreceptors (2)
located in the eyes and respond to light, provides the sense of vision
36
thermoreceptors (3)
respond to heat and cold, are free nerve endings, and use the same pathways as pain sensation
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where are thermoreceptors located? (4)
the dermis, skeletal muscle, the liver, and hypothalamus
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what is the pathway in which thermoreceptors send information? (3)
reticular formation in the brainstem -> thalamus -> primary sensory cortext
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nociceptors (2)
respond to noxious stimuli and are free nerve endings with large receptive fields
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where are nociceptors commonly found? (4)
superficial portions of the skin, joint capsules, within the periostea of bones, around the walls of blood vessels
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analgesia
inability to feel pain
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hyperalgesia
increased sensitivity to pain
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nociceptors may be sensitive to... (3)
temperature extremes, mechanical damage, dissolved chemicals
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pain information can be sent to the CNS by two types of axons
1. type A
2. type C
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type A axons
large myelinated fibers that are fast, sends prickling/fast pain to the CNS to trigger somatic reflexes before reaching primary somatosensory cortex
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type C axons
small unmyelinated fibers that are slow, sends burning/aching/slow pain and activated the reticular formation and thalamus - not very specific to exact location or area affected
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chemoreceptors
respond to only water-soluble and lipid-soluble substances dissolved in fluid
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chemoreceptors can monitor what three things in the blood
pH, carbon dioxide, and oxygen levels in arterial blood
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carotid bodies
located near the origin of the internal carotid arteries on each side of the neck; chemoreceptor
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aortic bodies
| where and what is it?
located between the major branches of the aortic arch; chemoreceptor
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mechanoreceptors
respond to stimuli that physically distort the receptor's plasma membrane; contains mechanically-gates ion channels that open/close in response to stretching, compression or twisting
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three classes of mechanoreceptors
1. tactile receptors
2. baroreceptors
3. proprioceptors
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tactile receptors
include fine touch, pressure receptors, and crude touch receptors
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tactile receptors provide detailed information about the stimulus, including... (5)
1. exact location
2. shape
3. size
4. texture
5. movement at the location
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two characteristics of fine touch and pressure receptors
very sensitive and have a relatively narrow receptive field
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three characteristics of crude touch and pressure receptors
1. less sensitive
2. have a relatively large receptive field, poor localization of stimulus
3. provides little information about the stimulus
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baroreceptors
monitors change in pressure; free nerve endings that branch with elastic tissue
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where can you find baroreceptors? (2)
the walls of distensible organs such as blood vessels, and digestive organs
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proprioceptors
monitors the position of joints, tension in tendons and ligaments, and the amount of skeletal muscle contraction
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three major groups of proprioceptors
1. receptors in join capsules
2. Golgi tendon organs
3. muscles spindles
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1. proprioceptors - receptors in joint capsules (3)
free nerve endings that detect pressure, tension, movement at the joint
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2. proprioceptors - Golgi tendon organs (2)
located between skeletal muscle and its tendon; monitor external tension generated during skeletal muscle contraction and are stimulated by tension in the tendon
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3. proprioceptors - muscle spindles (2)
monitor skeletal muscle length; used to trigger stretch reflexes
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unencapsulated nerve endings
dendrites with no connective tissue wrapping
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free nerve endings
| what are they? what do they detect?
tonic receptors with small receptive fields that are bare dendrites that detect temperature and pain (warm/cold receptors and nociceptors)
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tactile (Merkel) discs
tonic receptors with small receptive fields that are flattened nerve endings that terminate at tactile cells in the basal layer of the epidermis; very sensitive and detect light, touch, texture, edges, shapes
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hair receptors (root hair plexuses)
| actual hair
phasic receptors that are dendrites coiled around a hair follicle and respond to movements of the hair, are very sensitive
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types of unencapsulated nerve endings (3)
1. free nerve endings
2. tactile (Merkel) discs
3. hair receptors (root hair plexuses)
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encapsulated nerve endings
nerve fibers wrapped in glial cells or connective tissue; wrapping enhances sensitivity of selectivity of response
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types of encapsulated nerve endings (4)
1. tactile (Meissner) corpuscles
2. end (Krause) bulb
3. bulbous (Ruffini) corpuscles
4. lamellar (Pacinian) corpuscles
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tactile (Meissner) corpuscles
two or three nerve fibers within a fluid filled capsule of flattened Schwann cells
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end (Krause) bulbs
sensory nerve fiber surrounded by a connective tissue sheath
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what are tactile (Meissner) corpuscles linked to? (6)
linked to the edges of dermal papillae, especially areas of hairless skin like the fingertips, palms, eyelids, nipples, genitals
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bulbous (Ruffini) corpuscles (2)
flattened, elongated capsules containing a few myelinated axons in an incomplete fibrous capsule; tonic receptors located in the reticular layer of the dermis
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what do bulbous (Ruffini) corpuscles detect? (5)
heavy touch, pressure, stretching of skin, deformation of fingertips, and joint movement
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lamellar (Pacinian) corpuscules
large, ovoid receptos with a single dendrite surrounded by layers of flattened Schwann cells and fibroblasts
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what do lamellar (Pacinian) corpuscles detect?
they are phasic receptors that detects deep pressure and vibration, most sensitive to pulsing or high-frequency vibration
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where are lamellar (Pacinian) corpuscles located? (5)
found in the periosteum of bone, joint capsules, some viscera, and deep in the dermis especially of the hands, feel, breasts, and genitals
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exteroceptors
sense stimuli external to the body
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exteroceptors include receptors for...(8)
receptors for vision, hearing, taste, smell, and cutaneous sensations like touch, heat, cold, and pain
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interoceptors
detect internal stimuli
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where are interoceptors located? (3)
stomach, bladder, intestines
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what do interceptors sense? (4)
stretch, pressure, visceral pain, nausea
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proprioceptors
sense body position and movements, purely somatic sensation
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where are proprioceptors located? (3)
muscles, tendons, joint capsules
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general (somatosensory/somesthetic) senses
widely distributed in skin, muscles, tendons, joints, viscera; receptors may be simple, and some are just bare dendrites
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special senses
limited to head, innervated by cranial nerves, and involve complex sense organs
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afferent division of the nervous system
includes receptors that detect stimuli and replay the sensory information towards the CNS
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efferent division of the nervous system
include motor neurons that send commands to effectors through motor tracts or nerves taking information away from the CNS
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bundles of axons located in the PNS
nerves
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clusters of cell bodies located in the CNS
nuclei
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bundles of axons located in the CNS
tracts
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somatic nervous system
motor neurons and pathways that provide voluntary control of skeletal muscles
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somatic motor commands travel from motor center in the brain along these pathways (3)
- motor nuclei (CNS)
- tracts (CNS)
- nerves (PNS)
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autonomic nervous system
sends involuntary commands to viscera
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two divisions of the autonomic nervous system
sympathetic and parasympathetic
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sensory projection (2)
transmission of information from receptor to specific locations in the cerebral cortex; signals travel along projection pathways
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most somatosensory signals travel by way of three neurons
1. first-order neuron
2. second-order neuron
3. third-order neuron
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first-order neuron (4)
- signals from the head travel to pons/medulla via cranial nerves
- signals from below the head enters the posterior horn of the spinal cord via dorsal root of the spinal nerves
- touch, pressure, and proprioception fibers are large, myelinated, fast
- heat and cold fibers are small, unmyelinated, slower
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second-order neuron (2)
- decussate (cross) to opposite side (contralateral) in spinal cord, medulla, or pons
- end in thalamus, except for proprioception which ends in the cerebellum
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third-order neuron
| where do they span?
thalamus to primary somatosensory cortex of cerebrum
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three major somatic sensory pathways
1. spinothalamic pathway
2. posterior column pathway
3. spinocerebellar pathway
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spinothalamic pathway
| what info does it provide?
provides sensations of poorly localized (crude) touch, pressure, pain, and temperature
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spinothalamic pathway: first-order neurons
axons of the first-order sensory neurons enter the spinal cord and synapse on second-order neurons within the posterior grey horns
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spinothalamic pathway: second-order neurons
they cross to the opposite side of the spinal cord and then ascends up the spinal cord within the anterior or lateral spinothalamic tracts
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spinothalamic pathway - anterior tracts
| what info do they carry?
carry crude touch and pressure
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spinothalamic pathway - lateral tracts
| what info do they carry?
carry pain and temperature
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spinothalamic pathway: third-order neurons
they synapse in the thalamus, the information is sorted and processed before being transmitted to the primary somatosensory cortex
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posterior column pathway
| what info does it carry?
carries highly localizes (fine) touch pressure, vibration, and proprioception
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posterior column pathway: first-order neurons
enter the spinal cord and ascend up on the ipsilateral (same) side of the spinal cord and synapse onto the second-order neurons at the medulla oblongata
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posterior column pathway: second-order neurons
project axons that cross to the contralateral side and ascend to the thalamus
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posterior column pathway: third-order neurons
located in the thalamus, receives input from second order neurons, processes the info, and sends the information to the somatosensory cortex
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spinocerebellar pathway
| p
carries proprioceptive info from skeletal muscles, tendons, and joints; information terminated at the cerebellum for processing
114
pain
unpleasant perception of actual or potential tissue damage
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what does the perception of pain usually lead to?
evasive action
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what is pain perception lost from? (4)
| diseases and injuries?
leprosy, diabetes mellitus, nerve damage, neglect of injuries
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peripheral neuropathy
peripheral nerve damage
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nociceptive pain
stems from tissue injury; occurs when nociceptors are activated
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neuropathic pain
stems from injuries to nerves, spinal cord, meninges, or brain
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visceral pain
arises from internal organs; diffuse, dull, and hard to locate
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visceral pain creates sensations of... (3)
squeezing, cramping, nausea
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what is visceral pain caused by? (3)
stretch, chemical irritation, ischemia
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deep somatic pain
| where does it come from?
arises from bones, joints, muscles
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examples of deep somatic pain (3)
arthritis, sprains, bone fractures
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deep somatic pain can be caused by
excessive stretch, like a sprained ankle
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superficial somatic pain
usually arises from the skin
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examples of superficial somatic pain (3)
cuts, burns, insect stings
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fast pain
immediate, sharp, localized pain
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fast pain is carried by type _____ fibers
A; very fast
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discriminative pain
aka fast pain; we can tell exactly where its coming from
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slow pain is carried by type _____ fibers
C; slower, but still fast
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slow pain
burning, dull, aching pain, less localized
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pain signals from the head travel to the _____ via _____ _____
brainstem, cranial nerves
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pain signals from the head travel through these cranial nerves (4)
5, 7, 9, and 10
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pain signals from the neck and below travel through the ______ tract
spinothalamic tract
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referred pain
pain in viscera often perceived as originating from superficial sites
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what causes referred pain?
convergence of neural pathways in the CNS, and the brain cannot distinguish the source
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endogenous opioids
analgesic peptides secreted by the CNS, pituitary, digestive tract, and other organs; act as neuromodulators and block pain
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neuromodulators that block pain and give pleasure
enkephalins, endorphins, dynorphins
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opioids block pain through what process?
spinal gating
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spinal gating (3)
stops pain signals at the posterior horn, interneurons are stimulated to release enkephalins, and it inhibits second-order pain neurons
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amyotrophic lateral sclerosis (ALS)
progressive degenerative disorder affecting motor neurons in the spinal cord, brain stem, and cerebral hemisphere
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amyotrophic lateral sclerosis (ALS): cause
inherited by 5-10% in people but the rest is unknown
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amyotrophic lateral sclerosis (ALS): treatment
oral medication such as riluzole cannot reverse damage but can mitigate symptoms
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cerebral palsy (CP)
number of disorders affecting voluntary motor control, motor skills, posture/balance, memory, speech, learning; but is not progressive
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cerebral palsy (CP): possible causes (3)
unusually stressful birth, maternal exposure to drugs, genetic defect
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cerebral palsy (CP): treatment
muscle relaxants and pain relievers, various therapies like physical/speech
