cns Flashcards
1
Q
central nervous system
A
brain and spinal cord
2
Q
brainstem (composed of and function)
A
composed of midbrain, pons, medulla oblongata; functions: controls respirations, digestion, locomotion, cardiovascular, sleep/wake cycle, arousal, balance and posture
3
Q
spinal cord function
A
locomotor pattern generator
4
Q
cerebellum (where, functions)
A
at the base of cerebrum; balance, voluntary movement, coordination, learning
5
Q
cerebrum
A
- largest part of the brain (2 halves)
- corpus callosum (nerve axons that link r and l)
- 2 layers (grey and white matter)
6
Q
3 main components of the brain
A
cerebrum, cerebellum, brainstem
7
Q
cerebral cortex
A
outer layer of grey matter of cerebrum
- 4 lobes (frontal, parietal, occipital, temporal)
- functions: sensory perception, motor control, language, cognitive functions
8
Q
frontal lobe
A
personality, emotions, control of movement
9
Q
parietal lobe
A
mediates skin and muscle sensation
10
Q
occipital lobe
A
vision
11
Q
temporal lobe
A
hearing and memory
12
Q
forebrain
A
comprises the cerebrum and diencephalon
13
Q
limbic system
A
interconnected group of brain structures involved in learning, emotion, appetite, sex function, endocrine (hormone) integrations.
includes thalamus, hypothalamus, hippocampus, olfactory bulbs
14
Q
basal ganglia
A
movement initiation, inhibition of muscles antagonistic to the desired movement
15
Q
thalamus
A
sensory switchboard which selects and relays sensory signals to cortex
16
Q
hypothalamus
A
homeostasis, emotions
17
Q
meninges
A
membranes that cover the brain and spinal cord
- 3 layers (dura mater, arachnoid mater, pia mater)
18
Q
dura mater
A
tough outer layer of meninges
19
Q
arachnoid mater
A
spidery intermediary mesh of meninges
20
Q
pia mater
A
delicate inner layer of meninges
21
Q
meningitis
A
infection of the meninges
22
Q
cerebrospinal fluid
A
- maintain an appropriate electrolyte balance around neurons, bathe and support neural tissue
- produced in brain ventricles
- reabsorbed into the blood in the venous system at the same rate it is produced
23
Q
hydrocephalus
A
“water on the brain” occurs when reabsorption is blocked, CSF accumulates
treated surgically with drainage tubes
24
Q
glial cells
A
type of cell that provides physical and chemical support to neurons and maintain their environment
- 4 types (astrocytes, oligodendrocytes, ependymal cells, microglia)
25
astrocytes
physically support neurons by forming a scaffold that holds neurons together
forms blood brain barrier, forms scar tissue (which inhibits regeneration of axons), recycles neurotransmitter molecules, maintains electrolyte balance
26
oligodendrocytes
cells with relatively few branches which form the myelin sheath around neuronal axons
27
ependymal cells
produce cerebrospinal fluid
28
microglia
scavengers that ingest bacteria and cellular debris
29
gliomas
brain tumor on the blood brain barrier that arises from glial cells
30
meningioma
brain tumor on the blood brain barrier that arises in the meninges
31
why is it important that capillaries are tightly joined in the blood brain barrier
- protects neurons from chemical fluctuations and large molecules
- oxygen can cross but important large molecules such as glucose cannot
- non-porous capillaries may make block transport of beneficial drugs
32
path of a sensory receptor
- afferent axon leads to the CNS
- the cell body of the sensory axon is located just outside the spinal cord in a posterior root ganglion (dorsal root ganglion)
- the axon enters the spinal cord and terminates with synaptic connections on interneurons and efferent neurons
33
how many neurons run from the CNS to the effector organ (skeletal muscle)
one
34
vertebra column
boney structure that supports the trunk and head on the legs
35
dermatome
specific area of the skin that each spinal nerve innervates
36
myotome
specific set of muscles each spinal nerve innervates
37
posterior/dorsal
towards the back of the body
38
anterior/ventral
towards the front of the body
39
dorsal root ganglion (what is it, what is located there)
a cluster of neurons in a dorsal root of a spinal nerve; where sensory neurons are located
40
caudally
towards the tail
41
where are motoneurons located
in the ventral horn, efferent axons leave the spinal cord through ventral roots
42
what is the central grey matter composed of
motoneurons, interneurons, dendrites and axons
43
what is the surrounding white matter composed of
bundles of axons (tracts) that convey sensory signals ascending to the brain or motor commands descending from the brain
44
tracts
bundles of axons
responsible for carrying motor and sensory stimuli to and from the periphery
45
rostral
towards the nose
46
dermatomes
area of the skin that receives sensation from specific spinal nerves
- 3 types (cervical, thoracic, lumbar/sacral/coccygeal)
47
cervical nerves
mediate sensory input from arms
48
thoracic nerves
mediate sensory info from the abdomen
49
lumbar, sacral, coccygeal nerves
mediate sensory info from the legs and feet
50
shingles
occurs when neurons in the dorsal root ganglia, often in just one or two segments of the spinal cord, become infected with a virus related to chicken pox
- bands of sores and excruciating pain in the dermatomes
51
quadriplegia
a complete transection of the cervial level C6 or C7 resulting in paralysis of hand and finger movements but not paralysis of breathing of heart rate
52
paraplegia
spinal cord injury at L1 or L2 resulting in paralysis of legs, bladder, bowel and sex functions but hands, fingers, wrists, and elbows will be able to move, breathing, heart rate, and blood pressure are normal
53
modality
type of sensory info that is transmitted
- vision, sense of touch, hearing, movement
54
meissner's corpuscles
complex bulbous receptors in which the sensory terminal of the nerve axon is spiraled inside a capsule
responds to light tough of the skin
55
merkel's corpuscles
respond to tough
56
free nerve endings
respond to pain
57
pacinian corpuscles
responds vigorously to vibration; have a structure with slippery layers (lamellae) that slide over each other as the pressure around the corpuscles rises, distributes and amplifies the mechanical deformation of the nerve endings that are right in the middle of the receptor
58
ruffini corpuscles
respond to skin stretch; slowly adapting mechanoreceptors
- 2 types (warm and cold
59
sensory receptor A
includes skin receptors whose axons project directly to spinal cord
60
sensory receptor B
comprise first order receptor cells (release a neurotransmitter) that respond to stimuli and synaptically activate second order cells very close by, whose axons transmit info to the nervous system
61
somatosensory receptors
cover the surface of the body and signal a variety of sensory modalities to the CNS
62
mechanoreceptors
sense local tissue deformation in skin and viscera
63
thermoreceptors
sense temp in skin and brain
64
nociceptors
sense pain (tissue damage) in skin, viscera, muscle
65
proprioceptors
sense movement and force in muscles and joints
66
vestibular receptors
head acceleration and tilt
67
as the stimulus intensity increases
the membrane potential at the initial segment of the sensory receptors afferent axon increases until action potentials are generated
release of neurotransmitter within CNS increases
68
the stronger the stimulus
the greater the change in the membrane potential at the initial segment and the greater the rate of generation of action potentials
69
recruitment
as stimulus intensity increases, the number of senosry receptors that are activated increases
70
what happens when a stimulus is applied
- with a mechanoreceptor, when the membrane is distorted, this causes tiny pores in the cell membrane to open up; Na enters the cell which causes the inside of the cell to become less negative
- the larger the stimulus intensity, the larger change in the voltage
71
receptor potential
the change in voltage at the initial segment
72
frequency coding
the bigger the stimulus, the more the membrane channels in the sensory ending are distorted, the greater the number of action potentials per second
73
population code
the bigger the stimulus, the more sensory neurons are recruited into activity so more action potentials per second
74
temporal pattern code
variability of firing rate (bursts vs steady firing) may mediate certain types of sensation
75
tonic receptors
slowly adapting receptors; generate action potentials throughout the duration of the stimulus
- merkels corpuscles
- free neuron endings
- ruffini corpuscles
76
rapidly adapting receptors
respond only briefly each time the stimulus changes
- pacinian corpuscles
- meissners corpuslces
77
acuity
the ability to tell the difference between things that are close together
78
general principles of sensory stimulus processing
- modality
- stimulus intensity
- location
- sensation and perception
79
localization
the position of a stimulus either on the surface of the body or within the body
80
two-point discrimination
in tightly pack areas, the receptive fields of the receptors are small and sensory acuity is high
in not tightly packed areas, the receptive fields of the receptos are larger and sensory acuity is low
81
divergence
each sensory afferent sends branches to many neurons in the CNS
82
convergence
a given neuron in the CNS receives inputs from many sensory afferents
83
lateral inhibition
method of refining sensory info in afferent neurons and ascending pathways whereby fibers inhibit each other, the most active fibers causing the greatest inhibition of adjacent fibers
- sharpens contrast by focusing the activation of the neurons on the centre of a stimulus
84
sensation
the conscious awareness of a stimulus
- processing in the cerebral cortex
85
perception
when a sensation is combined with an understanding of its meaning
- processing in the cerebral cortex
86
topographic map
sensory cortex refers to the primary somatosensory cortex
- projection area is related to functional importance
- face and hands large, abdomen and legs small
87
homunculus
"little man"
shows body parts distorted according to the area of the somatosensory cortex that receives info from those body parts
88
descending inhibition
activity descending from higher centers in the brain and brainstem can "screen out: certain types of sensory info by inhibiting neurons in the afferent pathway
- 2 types (presynaptic inhibition and postsynaptic inhibition)
89
presynaptic inhibition
results from inhibition of the sensory axon close to the synapatic terminal; occurs close to the synpase between the sensory afferents and the neurons that convey info to the brain
90
postsynapatic inhibition
acts by hyperpolarizing the membrane of the second order sensory neurons to move their membrane potential further away from the threshold for generating action potentials
91
pathway of pain transmission
- painful stimulus causes tissue damage
- damaged tissue releases prostaglandins and histamine which active pain receptors
- pain receptors fire action potentials which travel to the dorsal part of the spinal cord
- activity in pain fibers causes release of substance P
- activates interneurons (projection neurons)
- signal pain and excite neurons in the thalamus and the cortex
- results in the sensation of pain
92
analgesia
suppression of pain transmission
93
aspirin
blocks the production of prostaglandins that are released by damaged tissue
94
gabapentin
blocks conduction in the nociceptive afferents
95
opioids (morphine)
block the release of substance P onto the projection neurons in the spinal cord
96
referred pain
the sensation of pain is experienced at a site other than the injured or damaged tissue
- when pain emanates from the viscera and internal organs, it is interpreted by the brain as coming from those areas of the body surface that converge onto the same interneurons in the spinal cord
97
anterolateral system
pain and temp afferent synapse onto second order interneurons in the spinal cord and these interneurons send axons that cross to the opposite side of the spinal cord then ascend to the brain in the spinothalamic or the anterolateral tracts
- the pathway crosses over within a vertebral segment upon entering the spinal cord
98
dorsal column system
touch, pressure, and stretch afferent enter the spinal cord and do not immediately contact interneurons, but instead form the dorsal columns which ascend to the brainstem where the afferents then synpase onto second order neurons in the brainstem. the second order neurons then send axons that cross over the contralateral side of the nervous system
99
supraspinal
above the spinal cord
- sensorimotor cortex, brainstem, cerebellum, cerebral cortex, thalamus and basal ganglia
100
what issues motor commands via the brainstem and spinal cord
the sensorimotor cortex, the cerebellum, and the basal ganglia
101
muscle spindle
sensory receptor that signals changes in muscle length
- located in parallel with the force producing muscle fibers inside the belly of the muscle
102
what sensory endings respond to changes in muscle length
group 1a and 2 sensory afferents
- spiraled around specialized muscle fibers (intrafusal muscle fibers - inside muscle spindle)
103
golgi tendon organs
tendinous fascicles at the ends of the muscle fibers
respond to force produced by the muscle
give rise to group 1b sensory afferents
104
spasticity
overactive stretch reflexes
105
flexor muscle and extensor muscle
muscle spindle signals length of flexor muscle
tendon organ signals force of extensor muscle
106
extrafusal muscle fibers
main muscle fibers found outside the muscle spindle that produce all the measureable force
107
alpha motor neuron
activate the main muscle extrafusal fibers to contract
108
gamma motor neurons
activate intrafusal muscle fibers
109
alpha-gamma coactivation theory
gamma motor neurons are coactivated with alpha motorneurons to keep the muscle spindle afferents firing during muscle shortening
110
stretch reflex
- tap of the patellar tendon
- small but very rapid increase in the length of the muscle (quad) or stretch of the muscle
- activate muscle spindle afferents
- action potentials in the afferent travel to the spinal cord
- synaptically activate quad motoneurons
- muscle shortens
111
golgi tendon during stretch reflex
have the reverse reflex action to that of the muscle spindle afferents
112
why are there two reflex systems that "compete" during muscle stretch
results in muscles resisting stretch in a spring-like manner (the stronger the spindle reflex, the stiffer the spring, the stronger the golgi tendon reflex, the more compliant the spring)
113
areas of the cerebral cortex that control movements of the extremities
- pre-motor cortex
- supplementary motor cortex
- primary motor cortex
- somatosensory cortex
- parietal love association areas
114
primary motor cortex =
sensorimotor cortex
115
primary sensory cortex =
somatosensory cortex
116
corticospinal tract (CST)
aka pyramidal tract
conveys signals from the sensorimotor cortex through the brainstem to the spinal cord
- formed from axons from neurons in the sensorimotor cortex
- crosses to the contralateral side of the nervous system at the brainstem level
- CST neurons make monosynaptic connections with spinal alpha motoneurons, whose axons in turn activate muscles
- only one neuronal synapse away from muscles
117
CST lesion
clinical term for damage to the sensorimotor cortex and CST: stroke, cerebrovascular accident (CVA), brain attack
- symptoms: weakness or complete paralysis of the extremities, exaggerated stretch reflexes, muscle spasm, speech deficits, attentional deficits
118
hemiplegia
inability to move the limb on the contralateral side of the body
119
paresis
complete paralysis of the extremities
120
hypertonus
excessive level of skeletal muscle tension or activity
121
spasticity
a state of increased muscular tone with exaggeration of the tendon reflexes
122
dysarthria
speech deficits
123
aphasia
inability to understand the meaning of sensory inputs, or a defect on language
124
apraxia
problem using day to day objects
125
hemi-neglect
occurs when patients fail to be aware of items to one side of their body
126
where in the brain is speech controlled
left side
127
broca's area
controls motor aspects of speech
128
what do lesions in the broca's area cause
motor aphasia (slurring speech)
129
wernicke's area
controls comprehension of language
association of visual, auditory, and tactile input with words
130
what do lesions in the Wernicke's area cause
sensory aphasia and dyslexia
131
sensory aphasia
difficulty in understanding the meaning of sensory inputs
132
dyslexia
results in difficulty in reading aloud fluently
133
vermis
area in the cerebellum that controls posture, movements of neck and axial (trunk) musculature
134
intermediate zone
area in cerebellum that controls locomotion
135
lateral zone
area in cerebellum responsible for coordinating complex, skilled movements of arms hands and fingers
136
flocculonodular lobe
area in cerebellum responsible for controlling balance
137
basal ganglia
large nuclei deep within the cerebral hemispheres that form the extrapyramidal system
responsible for initiating movement and suppressing activity of muscles that would resist the intended movement
138
lesions in basal ganglia result in
parkinson's disease, huntington's chorea, tourette's syndrome, and hemiballismus
139
parkinson's diseases
poverty of movement (bradykinesia) and rigidity and tremor
140
huntington's disease, tourette's syndrome and hemiballismus
too much movement (dyskinesia)
141
electroencephalogram (EEG)
monitors electrical activity in the brain
- amplified voltage fluctuations are recorded between pairs of electrodes on the scapl
142
sleep states and corresponding EEG waves
- NREM - N1 (alpha, some theta), N2 (alpha replaced with random waves of greater amplitude), N3 (theta and delta)
- REM (beta)
N1 -> N2 -> N3 -> N2 -> REM
143
glasgow coma scale
set of characteristics used to classify the level of consciousness of a person
- based on eye movements, responses to questions and whether the person makes voluntary movements and can obey commands to move their limbs
144
criteria for brain death
- the nature and duration of the coma must be known
- cerebral and brainstem function are absent
- supplementary criteria includes flat EEG for 30 minutes
145
reticular activating system
a set of nuclei in the brainstem and hypothalamus
- get activated during wakefulness
- releases monoamines to the hypothalamus and other brain areas
146
orexins
neuropeptide hormones supplied by hypothalamus to the thalamus and cortex to maintain wakefulness
147
suprachiasmatic nucleus
activates orexin-producing neurons in the morning to promote wakefulness
secretes melatonin at dusk
set the circadian rhythm
148
sleep centre
a nucleus found in the pre-optic nucleus of the hypothalamus
causes GABAergic inhibition to the reticular activating system to reduce orexin levels
149
lesion in the reticular activating can cause
coma that can last for months or years
150
characteristics of consciousness
awareness of the passage of time, external sensory inputs, internal states such as fatigue, thirst, happiness, memories, reasoning, and ideas
- selective attention and conscious perception
151
selective attention
attention shifts from one focus to another
- CNS areas: thalamus and locus ceruleus in brainstem RAS
152
conscious perception
specific set of neurons in different parts of the brain temporarily function together to generate the consciousness experience
153
primary motivated behaviour
directly related to homeostasis (maintaining water balance, nutrition, body temp)
154
secondary motivated behaviour
results in pleasure, can be disadvantageous (over-eating, drugs)
155
why does motivation = reward
a pathway in the brainstem nuclei releases dopamine within the frontal lobe of the brain which elicits pleasure or reward
156
emotions
internal attitudes towards events and the environment
- different parts of the brain can be stimulated electrically to elicit particular types of emotion
157
working memory (short-term)
- easily acquired, quickly lost
- episodic: recent events, places
- visuo-spatial: recent sights, locations
- phonological: recent words, sounds
158
long-term memory
- slower period of acquisition, last for much longer, even a lifetime
- declarative (conscious) - semantic (facts), episodic (personal experiences)
- procedural (motor, sub-conscious) - stimulus response behaviours
159
how and where are memories made
laying down of the memory trace
in hippocampus in temporal lobe
160
caudate nucleus
part of the basal ganglia involved in consolidating stimulus to response behaviors such as those that occur during operant conditioning
161
amnesia
absence of memory; retrograde and anterograde loss of stm
162
korsakoff's syndrome
a complete anterograde amnesia from damage to hippocampus
163
alzheimer's disease
involves the degeneration of memory-holding neurons, perhaps due to proteins called amyloid precursor proteins that cause excitotoxicity
