CH 14 Flashcards
1
Q
what are the four main parts of the adult brain?
A
- cerebrum
- cerebellum
- diencephalon
- brainstem
2
Q
what are the protective coverings and barriers of the brain?
A
- cranial meninges
- bones of the skull
- cerebrospinal fluid
3
Q
what are the cranial meninges?
A
CT coverings continuous w/ spinal meninges, sharing common names w/ them
4
Q
what is the difference between the cranial and spinal dura mater?
A
the superficial cranial dura mater has two layers:
- outer periosteal layer
- inner meningeal layer
5
Q
what are some differences btwn the cranial and spinal meninges?
A
- cranial dura mater has 2 layers, spinal dura mater has 1 layer
- no epidural space btwn dura mater and bones of the skull
6
Q
what are the extensions of dura mater that separates parts of the brain?
A
- falx cerebri
- falx cerebelli
- tentorium cerebelli
7
Q
what is the falx cerebri?
A
extension of the cranial dura mater that separates the right and left hemispheres of the brain
8
Q
what is the falx cerebelli?
A
extension of the cranial dura mater that separates the left and right hemispheres of the cerebellum
9
Q
what is the tentorium cerebelli?
A
extension of the cranial dura mater that separates the cerebellum and the cerebrum
10
Q
what is the blood-brain barrier?
A
barrier btwn blood and the brain that maintains the selective permeability of brain tissue to substances in blood
11
Q
what forms the blood-brain barrier?
A
- continuous capillaries (w/o fenestrations) w/ tight junctions btwn endothelial cells
- Astrocytes associate tightly w/ capillaries and secrete substances to maintain tight junctions
12
Q
which arteries supply oxygenated blood to the brain?
A
- anterior L/R internal carotid arteries
- posterior L/R vertebral arteries
13
Q
which veins drain deoxygenated blood from the brain?
A
dural venous sinuses drain venous blood into the internal jugular veins
14
Q
how is neuronal activity and blood flow to the brain related?
A
as activity of neurons increase, blood flow to the brain also increases
increased perfusion (extent of blood flow)
15
Q
what is the blood-brain barrier permeable to?
A
- lipid-soluble substances
– steroid hormones
–nonpolar molecules (O2 and CO2) - some water-soluble substances
– water
– glucose
– some ions (slow transport only)
16
Q
what is the blood-brain barrier impermeable to?
A
- proteins
- antibiotics
17
Q
What could disrupt the function/structure of the blood-brain barrier?
A
- tumours
- trauma to vessels and brain tissue
- infection (meningitis, rabies)
- radiation
18
Q
what is the result of a compromised blood-brain barrier?
A
- brain tissue now permeable to more substances, can lead to damaged tissue
- brain hemorrhaging
- more infection
19
Q
what is the composition of CSF?
A
consists mainly of water plus glucose, ions, proteins, lactic acid, urea, and some leukocytes
20
Q
where is CSF located in the brain?
A
the ventricles, it continuously circulates around them and through spinal cord
21
Q
what are the four ventricles of the brain?
A
- 2x lateral ventricles
- third ventricle
- fourth ventricle
22
Q
what separates the two lateral ventricles?
A
thin membrane - septum pellucidum
23
Q
where is the third ventricle located?
A
- between the two halves of the thalamus, superior to the hypothalamus
- connected to the lateral ventricles by two interventricular foramina
24
Q
where is the fourth ventricle located?
A
between the brainstem and the cerebellum
25
what are the functions of cerebrospinal fluid?
- mechanical protection: **absorbs shock** and permits brain and spinal cord to **float weightlessly**
- chemical protection: maintains the specific **optimal electrochemical** environment required for accurate neuronal signalling
- circulation: circulates nutrients and waste
26
where is CSF synthesized?
in choroid plexuses lining ventricles of the brain
- **ependymal cells** filter blood plasma and secrete the filtered substance as CSF
27
what are choroid plexuses?
capillary networks in the brain's ventricles where ependymal cells fliter blood plasma and secrete CSF
- secretion is also **bidirectional**
- ependymal cells are joined by **tight junctions**, forming **blood-CSF barrier**
28
how is CSF circulated through the ventricles?
CSF from choroid plexuses of lateral ventricles → interventricular foramina → third ventricle, choroid plexuses of third ventricle → aqueduct of midbrain → fourth ventricle
29
how is CSF circulated starting from the fourth ventricle?
subarachnoid space:
- fourth ventricle → median or lateral apertures → subarachnoid space
central canal:
- fourth ventricle → central canal (they are continuous w/ e/o)
30
what are apertures?
three openings in the roof of the fourth ventricle where CSF flows into and then through the subarachnoid space around brain and spinal cord
31
what are the three different apertures?
- 1x median aperture
- 2x lateral apertures
32
how is CSF reabsorbed?
through **arachnoid granulations**, extensions of the arachnoid mater that project into the **dural venous sinuses** and are especially prominent in **superior sagittal sinuses**
33
why is CSF volume relatively constant?
rates of filtration and reabsorption of CSF is also relatively constant
34
what is hydrocephalus?
condition caused by increased CSF pressure
- may be caused by tumours, inflammation, or malformation
- pressure on delicate brain and spinal cord tissues compresses them, altering their functions
35
how do you treat hydrocephalus?
drain excess CSF to relieve pressure, usually via surgical insertion of a **shunt**
36
what does the brainstem consist of?
- medulla oblongata
- pons
- midbrain
37
what is the reticular formation?
network of grey (cell bodies) and white (myelinated axons) matter tracts within the brainstem with both sensory and motor fxns.
38
what is the medulla oblongata?
- continuous w/ spinal cord
- forms inferior portion of brainstem
39
what is the function of the medulla oblongata's white matter?
contains all sensory and motor tracts that run btwn brain and spinal cord
40
what are the medulla oblongata's pyramids?
enlarged corticospinal tracts found on anterior side of medulla oblongata that controls **voluntary movements** of limbs and trunk
41
what is the decussation of pyramids?
- at junction of MO with spinal cord
- 90% of axons on one side cross to the opposite side
- why one side of the brain controls the **movements** of the *opposite* side of the body
42
how does the medulla oblongata control multiple body functions?
nuclei such as cardiovascular centre, respiratory centre, and vomiting, coughing, etc. centres are found in the medulla oblongata
43
what is an olive?
bulges just lateral to each pyramid of the medulla oblongata that contains a nucleus
- receives info from **cerebral cortex, midbrain, and spinal cord**
44
what is the function of the inferior olivary nucleus?
neurons in the inferior olivary nucleus extend their axons into the cerebellum to regulate **muscle activity**
45
what are the gracile and cuneate nuclei?
nuclei in the medulla oblongata that integrates information of **somatic** sensations (pain, touch, pressure, conscious proprioception)
46
what is the pons?
"bridge", connects parts of the brain with each other via tracts
connects:
- L/R of cerebellum
- nerve impulses controlling voluntary skeletal movements from cerebral cortex to cerebellum
47
what are some nuclei found in the pons?
- pontine nuclei
- respiratory group
- vestibular nuclei
- nuclei for cranial nerves 5-8
48
what is the midbrain?
*mesencephalon*
- extends from pons to diencephalon
- contains **cerebral aqueduct**
- contains sensory tracts, motor tracts, and nuclei (for visual and auditory info)
49
what are tectum?
posterior portion of midbrain w/ 4 bumps
- 2x superior colliculi
- 2x inferior colliculi
50
what are the superior colliculi?
2 bumps on posterior portion of pons that are **reflex centers for visual stimuli**
51
what are the inferior colliculi
2 bumps on posterior portion of pons that are **reflex centers for auditory stimuli**
- controls the **startle reflex**
52
what are peduncles?
anterior portion of the midbrain containing three paired tracts
- ascending axons carry sensory info to **thalamus**
- descending tracts run btwn cerebrum, pons, medulla oblongata, and spinal cord
53
what are the three paired tracts in the midbrain's anterior cerebral peduncles?
- corticospinal
- corticobulbar (brainstem nuclei)
- corticopontine
54
what is the substantia nigra?
large and darkly pigmented nuclei in midbrain, neurons release **dopamine** to help control subconscious muscle activity, roles in reward and addiction
55
what are red nuclei?
nuclei found in midbrain that are red due to **rich blood supply**
- axons from **cortex and cerebellum** synapse here to coordinate **muscular movements of limbs**
56
what cranial nerves/ nuclei are found in the midbrain?
cranial nerves 3 and 4, oculomotor and trochlear
57
what is the reticular activating system?
ascending portion of the reticular formation
- controls visual, auditory, mental activity, pain/touch/pressure sensing and **consciousness**
- controls arousal, attention, alertness, sensory overload
58
what is arousal?
ability to wake up from sleep
59
what is sensory overload?
ability to filter excessive auditory/visual stimuli
60
what does the descending portion of the reticular activating system control?
**muscle tone** via cerebellum and spinal cord
- also regulates heart rate, blood pressure, and respiratory rate
61
what does inactivation of the reticular activating system lead to?
sleep
62
what does damage to the reticular activating system lead to?
coma, due to lack of arousal
63
what does the reticular activating system not help process?
olfactory stimuli, meaning you won't be able to wake up from smells (like a burning house)
64
what is the cerebellum?
highly convoluted portion of brain that is posterior and inferior to cerebrum
65
what is the cerebellum's grey matter cortex?
superficial portion of cerebellum made of grey matter
66
why is the cerebellum highly convoluted?
for increased surface area, cerebellum is 10% of brain's mass but contains 50% of brain's neurons
67
what are cerebellar peduncles?
white matter tracts that attaches cerebellum to the **brainstem** and coordinates muscle movements
- **myelinated for rapid communication for coordination**
- inferior, superior, and middle peduncles
68
what is the vermis?
the central body of the cerebellum that separates the cerebellum into left and right cerebellar hemispheres
69
what are cerebellar fissures?
grooves on cerebellum that divide the hemispheres into lobes
70
what are the lobes of the cerebellum?
- anterior lobe
- posterior lobe
- flocculonodular lobe
71
what do the anterior and posterior lobes of the cerebellum do?
controls **subconscious** movements
72
what does the flocculonodular lobe of the cerebellum do?
controls **equilibrium** and **balance**
73
what are the functions of the cerebellum?
- determines **accuracy** of muscle movements and initiates adjustments
- **smooths out** movements
- **corrects errors**
- helps w/ learning complex movement sequences (like choreography)
- regulates **posture** and **balance**
- some nonmotor fxns. in learning, memory, etc. due to connections to cerebral cortex
74
what does damage to cerebellum result in?
ataxia
- problems in balance, stiffness
- uncoordinated movements and **gait**
- slurred, mumbling speech
- may be due to trauma/drugs
75
what is the diencephalon?
"core" of brain tissue, covered by cerebral hemispheres
- consists of thalamus, hypothalamus, epithalamus
76
what is the thalamus?
- 80% of diencephalon
- **relays** signals from **spinal cord and brainstem** → **primary sensory cortex**
- **transmits** signals from **cerebellum** → **primary motor cortex**
- plays a role in **consciousness**
77
what is the interthalamic adhesion?
grey matter that joins right and left halves of the thalamus in 70% of humans
78
what are the thalamic nuclei?
**don't need to memorize**
seven major groups that form diff. connections to **cerebral cortex**:
- anterior nucleus
- medial nuclei
- lateral group
- ventral group
- intralaminar nuclei
- periventricular nucleus
- reticular nucleus of prethalamus
79
what is the hypothalamus?
- inferior to thalamus
- plays major part in maintaining **homeostasis**
80
what are the nuclei found in the hypothalamus?
- posterior hypothalamic area
- intermediate hypothalamic area
- anterior hypothalamic area
- preoptic area
81
what is the posterior hypothalamic area?
contains nuclei for **olfaction**, feeding reflexes (licking, swallowing)
82
what is the intermediate hypothalamic area?
contains **infundibular stalk**, regulates anterior pituitary gland fxn.
83
what is the infundibular stalk?
found in hypothalamus, connects hypothalamus to pituitary gland
84
what is the anterior hypothalamic area?
contains axons from paraventricular and supraoptic nuclei that transport **ADH** and **oxytocin** to posterior pituitary
85
what is the preoptic area?
anterior part of hypothalamus that helps regulate certain autonomic activities (e.g. body temp)
86
what are the functions of the hypothalamus?
- control of the ANS
- hormone production
- regulation of emotional and behavioural patterns
- regulation of eating and drinking
- control of body temp
- regulation of circadian rhythms and states of consciousness
87
how does the hypothalamus function in control of the ANS?
axons from hypothalamus extend to **sym.** and **para. nuclei** in brainstem and spinal cord
- stimulates smooth/cardiac muscle contraction and secretions from glands
88
how does the hypothalamus function in hormone production?
- hypothalamus releases hormones into capillary network → carried to anterior pituitary → stimulates/inhibits secretion of anterior pituitary hormones
- cell bodies in paraventricular and supraoptic nuclei produce **ADH** and **oxytocin** →transported through **infundibulum stalk** and released by the posterior pituitary gland
89
what hormones do cell bodies in paraventricular and supraoptic nuclei secrete?
- antidiuretic hormone
- oxytocin
90
how does the hypothalamus function in regulating emotional and behavioural patterns?
works w/ **limbic system** to express rage, aggression, pain, pleasure, sexual arousal
91
how does the hypothalamus function in regulating eating and drinking?
hypothalamus contains **thirst** center, **feeding** center, and **satiety** center
- certain cells that can sense osmotic pressure changes are stimulated by increase of osmotic pressure of ECF and cause thirst sensation → drinking water restores normal osmotic pressure
92
how does the hypothalamus function in controlling body temperature?
hypothalamus functions as body's **thermostat**
- when blood temp flowing through hypothalamus changes, ANS responses are activated to restore homeostatic temperature
93
how does the hypothalamus function in regulating circadian rhythms and states of consciousness?
**suprachiasmatic nucleus** receives **visual** input from retina to synchronize biological rhythms to 24-hr cycle
- suprachiasmatic nucleus serves as body's internal biological clock
94
what is the epithalamus?
portion of diencephalon that is superior and posterior to thalamus
- contains pineal gland and habenular nuclei
95
what is the pineal gland?
endocrine gland found in epithalamus, secretes **melatonin** to regulate circadian rhythms
96
what are the habenular nuclei?
nuclei found in epithalamus that regulate **emotional** responses to **olfactory** stimuli
97
what are the circumventricular organs?
- located around the third ventricle
- includes parts of hypothalamus, pineal gland, pituitary gland, etc.
- **lacks a BBB**
98
what is the fxn. of the circumventricular organs?
coordinates **endocrine** and nervous responses to maintain homeostasis (BP, fluid volumes and compositions, hunger, thirst, etc.)
- maybe site of HIV dissemination
99
what is dissemination?
initial infection occurs to new organs in the body
100
why do the circumventricular organs lack a blood-brain barrier?
- circumventricular organs have to sense signals from blood circulating around it in order to coordinate endocrine responses and maintain homeostasis
101
what are the three parts of the cerebrum?
1. outer cerebral cortex (grey matter)
2. inner cerebral white matter
3. deep grey matter nuclei
102
what is the functions of the cerebrum?
produces intelligence, learning, imagination, and memory
103
what are cerebral gyri?
extensively folded ridges on cerebral cortex
104
what are cerebral sulci?
shallow grooves that divide individual gyri
105
what are interlobal sulci?
intermediate grooves that divide cerebrum into lobes
106
what are cerebral fissures?
deep grooves that divide the brain into hemispheres/parts
107
what is the longitudinal cerebral fissure?
deepest and most prominent groove on brain that defines the cerebral hemispheres
108
what is the corpus callosum?
white matter tracts that connects the cerebral hemispheres together
109
why do each lobes process sensory input and output motor functions to the opposite side of the body?
decussation of pyramids in brainstem, 90% of axons cross over midline and innervate opposite side of body
110
what is the central cerebral sulcus?
divides frontal lobe from parietal lobe
111
what is the lateral cerebral sulcus?
separates frontal lobe from temporal lobe
112
what is the parieto-occipital sulcus?
divides parietal lobe from occipital lobe
113
what is the function of the frontal lobes?
cognitive fxns, control of emotions, voluntary movement
114
what is the function of the parietal lobes?
processes information about temperature, taste, touch, movement, proprioception
115
what is the function of the occipital lobes?
processes visual information
116
what is the function of the temporal lobes?
processes **memories** and integrates them with sensations of taste, touch, sound, and sight
117
what is the function of the temporal lobes?
processes sensory input of taste (gustation)
118
what are the different tracts that can be found in the cerebral white matter?
1. association tracts
2. commissural tracts
3. projection tracts
119
what are association tracts?
in cerebral white matter, conducts nerve impulses between gyri in **same** hemisphere
- ipsilateral, doesn't cross midline
120
what are commissural tracts?
in cerebral white matter, conducts nerve impulses between corresponding gyri in **opposite** hemispheres
- contralateral, crosses midline
121
what are the different kinds of commissural tracts?
- corpus callosum
- anterior commissure
- posterior commissure
122
what are projection tracts?
in cerebral white matter, conducts nerve impulses from **cerebrum** to other parts of brain/spinal cord
123
what is the internal capsule?
thick band of white matter containing both ascending and descending tracts that acts as a **projection tract**
124
what is the corpus striatum?
group of nuclei buried deep within each cerebral hemisphere
- globus pallidus
- putamen
- caudate nucleus
125
what composes the lentiform nucleus?
globus pallidus and putamen
126
what are the functions of the corpus striatum?
- receives input from cerebral cortex and sends output back to motor cortex via thalamus
- also communicates w/ substantia nigra
- helps start and stop movements (activity in corpus striatum can be detected before movements)
- helps control muscle tone, subconscious movements, and posture (e.g. swining arms, spontaneous laughter)
- affects attention, memory, planning
- coordinates w/ **limbic system** to regulate emotional behaviours
127
what is the fornix?
white matter bundle that connects the components of the limbic system
- forms floor of diencephalon
- wraps around and up the corpus callosum
128
what is the limbic system?
collection of structures from cerebrum, diencephalon, and midbrain
- involved in establishing **emotional states** (pain, pleasure, docility, affection, anger) and olfaction and memory
-
129
what happens when amygdala is damaged in humans?
humans unable to recognize fear/anger in other humans
130
what is the hippocampus?
found in limbic system, involved in memory **storage** and **retrieval**
- contains cells that are capable of mitosis
131
what is a lobotomy?
- removal of a portion of the brain, often to treat "hysterical" women into docility
1. remove part of scalp
2. drill burr holes and remove portion of cranium
3. remove amygdala and other brain structures (portions of temporal lobe)
132
what are the cerebral cortex's primary sensory areas?
where sensory info from peripheral receptors arrives to cerebral cortex
- receives touch, pressure, vibration, itch, tickle, temp, pain, and proprioception info
- includes the primary somatosensory, visual, auditory, gustatory, and olfactory cortexes
133
what are sensory association areas?
- lies nearby the primary sensory areas
- facilitates sensory info processing along w/ other brain centers (recognition & awareness)
134
what is a somatosensory map/sensory homunculus?
misshapen map of body formed by peripheral sensory receptors linking to sensory areas
- each sensory area receives stimuli from specific part of the body
135
what determines how much area of the sensory homunculus is devoted to a body part?
the number of receptors found on a body part
136
what is the primary visual cortex?
receives impulses that convey information for vision (shape, colour, movement)
- found on posterior tip of occipital lobe
137
what is the primary auditory cortex?
interprets basic characteristics of sound (rhythm and pitch)
- found on superior part of temporal lobe, near lateral cerebral sulcus
138
what is the primary gustatory cortex?
- receives impulses for taste
- located in the insula
139
what is the primary olfactory cortex?
- receives impulses for smell
- found in temporal lobe on medial aspect (peel back and look inside)
140
what are the motor areas?
governs voluntary muscular movement
- formed by anterior portions of each cerebral hemisphere
- primary motor cortex
- premotor cortex
- Broca's area
- Frontal eye field
141
why does each region of the primary motor cortex control specific skeletal muscles on the **contralateral** side of the body?
decussation of pyramids in brainstem
142
what is the number of neurons devoted to a muscle group dependent on in the primary motor cortex?
dependent on whether the area is responsible for fine/skilled movements (more neurons) or gross movements (less neurons)
143
what is the premotor cortex?
motor association area anterior to primary motor cortex
- controls complex, learned, sequential, and coordinated movements (typing, etc.)
- fine-tune movements
- serves as **memory bank** for how to do these movements
144
what is the frontal eye field?
controls voluntary **scanning** movements of eyes (e.g. reading a line of text)
- partially in and anterior to premotor cortex
145
what is Broca's area?
- helps control articulation of speech (ability to speak)
- controls production of speech
- located in left frontal lobe
146
what happens if Broca's area is damaged?
person has Broca's aphasia, person cannot speak but can understand
147
what is aphasia?
communication dysfunction, including inability to speak, understand, or write
148
what is the function of association areas?
concerned w/ complex **integrative** functions such as memory, emotions, reasoning, will, judgement, personality traits, and intelligence
- different association areas connected to e/o by association tracts
- nerve impulses are transmitted from primary areas to association areas
149
why are association areas usually nearby to the primary areas?
nerve impulses are transmitted from primary areas to association areas, connected to each other by association tracts
150
what is the somatosensory association area?
- receives input from primary somatosensory cortex and thalamus
- integrates and interprets sensations
- can determine exact shape/texture of object by feel alone (proprioception)
- stores past somatic sensory experiences (memories)
- posterior to somatosensory area
151
what is the visual association area?
- in occipital lobe
- receives sensory input from primary visual cortex and thalamus
- relates present and past visual experiences (object recognition)
152
what is the facial recognition area?
- receives input from visual association area
- stores information about faces, allowing you to recognize people by sight
- found in inferior temporal lobe (right hemisphere, usually dominant)
153
what is the auditory association area?
- allows for recognition of sound as speech, music, or noise
- located inferior and posterior to primary auditory area, in temporal cortex
154
what is the orbitofrontal cortex?
- receives sensory impulses from primary olfactory area
- allows us to identify and distinguish different odours
- located in lateral part of frontal lobe
155
what is Wernicke's area?
- broad association area in **left** temporal and parietal lobes
- interprets **meaning** of speech by recognizing spoken words
- comprehension of speech, translation of words to thought
- writing, recognizing, understanding written words
156
what is the function of areas in **right** hemisphere corresponding to Broca's area and Wernicke's area?
add **emotional content** to language
157
what is Wernicke's aphasia?
can speak, but cannot arrange words coherently, lacks speech comprehension
- can also have hard time w/ writing thoughts
158
what is the common integrative area?
association area that surrounds somatosensory, visual, and auditory association areas
- **integrates sensory interpretation** → formation of thoughts based on sensory input from different brain areas
- transmits signals to parts of brain for appropriate responses
159
what is the prefrontal cortex?
extensive area of anterior frontal lobe
- well-developed in primates
- many connections w/ other brain regions
- regulates **personality, intellect, recall, initiative, judgment, foresight, reasoning, conscience, intuition, mood, future planning, abstract ideas**
160
what is hemispheric lateralization?
functional & structural asymmetry of the cerebral hemispheres, established early in development, during gestation
- may be less pronounced in biological females
161
what results in less pronounced lateralization in females?
more commissural tracts
162
what results in hand preferences when writing?
- hemispheric lateralization
- bigger areas in one hemisphere controlling dominant hand than other hemisphere
163
what are the functions of the right hemisphere?
**visual, creative, spatial skills**
- musical & artistic awareness
- space & pattern recognition
- face recognition, facial expression recognition
- generating emotional content of language
- producing mental picture of spaces
- identifying, discriminating btwn odours
164
what are the functions of the left hemisphere?
**verbal, logic, language**
- reasoning
- numerical, scientific skills
- ability to use and understand sign language
- spoken, written language
165
what does damage to broca's/wernicke's area in right hemisphere do?
- speaking in a **monotone**
- inability to generate **emotional inflection** in speech
166
what does damage to left hemisphere often result in?
aphasia
*broca's and wernicke's area found in left hemisphere*
167
what are brain waves?
electrical activity in brain due to many neurons of brain sending millions of nerve impulses
168
what is an electroencephalogram?
digital output of brain waves made after placing electrodes on forehead and scalp to produce electrical signals
169
what are the four types of brain waves?
- alpha waves
- beta waves
- theta waves
- delta waves
170
what are alpha waves?
electrical waves made while awake but not fully alert, resting with eyes closed, absent during sleep
171
what are beta waves?
small and frequent electrical waves made while awake, mentally active, fully alert
172
what are delta waves?
electrical waves occurring only during **deep sleep** in adults
173
what are theta waves?
electrical waves that indicate emotional **stress** in adults
174
olfactory (I) nerve
- sensory
- receives **olfactory** stimuli from olfactory mucosa of nasal cavity → olfactory bulb → synapses w/ neurons that form olfactory tracts → primary olfactory area in **temporal lobe**
175
optic (II) nerve
- sensory
- receives **visual** stimuli from eyeball's retina
176
describe the path visual stimuli take to get to the primary visual cortex
ganglion cells axons form optic nerve → merge and some axons cross in **optic chiasm** → optic tracts → thalamus → primary visual cortex
177
why do some ganglion cells' axons go to the midbrain?
to synapse w/ motor neurons that control eye movements
178
where does the optic nerve enter the brain?
through the optic foramen
179
describe how visual stimuli is transduced
visual stimuli sensed by photoreceptors (rods and cones) in retina, → bipolar cells → ganglion cells → optic nerve
180
where do optic tracts end?
MOST end in **lateral geniculate nucleus** in the **thalamus**
- they synapse w/ neurons and axons of these neurons extend to **primary visual cortex**
SOME end in **superior colliculi** and motor nuclei of brainstem
- synapse w/ motor neurons controlling extrinsic and intrinsic eye muscles
181
oculomotor (III) nerve
- motor
- innervates **extrinsic muscles** to move eyeballs and upper eyelid
- also as **autonomic motor output** to **constrict pupils**
superior: innervates superior rectus, levator palpebrae superioris
inferior: innervates medial rectus, inferior rectus, inferior oblique muscles, ciliary muscle, circular muscle of iris
182
trochlear (IV) nerve
- motor
- innervates **superior oblique muscle of eyeball**
183
trigeminal (V) nerve
- mixed
- 3 branches: opthalmic, maxillary, mandibular
sensory: receives **sensory** stimuli from skin over upper eyelids, lacrimal glands, cornea, mucosa of nose, upper teeth, palate, lower teeth, 2/3 of tongue
motor: innervates **muscles of mastication** to control chewing movements
184
what is the opthalmic branch of the trigeminal (V) nerve?
receives stimuli from sensory axons from skin over upper eyelids, **lacrimal glands**, cornea
185
what is the maxillary branch of the trigeminal (V) nerve?
receives stimuli from sensory axons in mucosa of nose, upper teeth, palate
186
what is the mandibular branch of the trigeminal (V) nerve?
receives stimuli from sensory axons in lower teeth, 2/3 of tongue
187
where do sensory axons of trigeminal (V) nerve terminate?
they enter through trigeminal ganglion and terminate in **nuclei of pons**
188
what is trigeminal neuralgia?
nerve pain of CN V, can result in shingles, muscle weakness, loss of sensation in face
- 1st sign of multiple sclerosis
189
abducens (VI) nerve
- motor
- innervates **lateral rectus muscle of eyeball**
190
what can damage to CN III, IV, and VI lead to?
strabismus
191
what is strabismus?
disorder where eyes do not line up in same direction
192
what is sensory functions of facial (VII) nerve
- extend from taste buds of anterior 2/3 of tongue, extending to thalamus, then to **gustatory areas** of cerebral cortex
- extend from **external acoustic meatus** in skin to relay touch, pain, thermal sensations
193
what is motor functions of facial (VII) nerve?
- innervates muscles of facial expression and stapedius msucle
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what is the function of brachial motor axons of the facial (VII) nerve?
innervates middle ear, facial, scalp, and neck muscles
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what is the function of parasympathetic motor axons of the facial (VII) nerve?
regulates autonomic glandular function, ends in two ganglia that extends to the lacrimal glands, palatine glands, nasal glands, oral cavity glands
196
what is Bell's palsy?
damage to facial (VII) nerve
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vestibulocochlear (VIII) nerve
- special sensory
- receives impulses for hearing and equilibrium
198
what is the function of the vestibular branch of the vestibulocochlear (VIII) nerve?
- receives impulses for equilibrium
- extends from semicircular canals, and vestibule of inner ear
- **ends in vestibular nuclei in** **pons and cerebellum**
199
what is the function of the cochlear branch of the vestibulocochlear (VIII) nerve?
- receives impulses for hearing
- originates in **spiral organ** in cochlea of inner ear
- extends to **nuclei in medulla oblongata** and ends in **thalamus**
- **motor fibres** regulate hair cells in inner ear
200
what is the sensory axons of the glossopharyngeal (IX) nerve?
- originates from **tastebuds on posterior 1/3 tongue**
- proprioceptors for swallowing muscles
- baroreceptors
- chemoreceptors
- external ear
- cell bodies located in superior and inferior ganglia
- pass through **jugular foramen** and ends in medulla oblongata
201
what is the motor neurons of the glossopharyngeal (IX) nerve?
- originates from **nuclei in medulla oblongata**
- exits skull through **jugular foramen**
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what do the branchial motor axons of CN IX do?
innervate **stylopharyngeus muscle** for swallowing
203
what do the parasympathetic motor axons of CN IX do?
stimulate **parotid gland** for saliva secretion
204
what is the sensory axons of CN X?
originate from:
- the skin of external ear for touch, pain, and thermal sensations
- few taste buds in epiglottis and pharynx
- proprioceptors in muscles of neck and
throat
- baroreceptors in carotid sinus
- chemoreceptors in carotid and aortic
bodies
- visceral sensory receptors in organs in thoracic and abdominal
cavities
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what do branchial motor axons of CN X do?
innervate muscles of pharynx, larynx, soft
palate (for swallowing, vocalization, coughing)
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what do parasympathetic motor axons of CN X do?
supply lungs heart, glands of digestive canal, smooth muscles of passageways and intestine (visceral organs)
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accessory (XI) nerve
- motor
--cranial accessory part of CN X
-- spinal accessory motor axons originate from anterior grey horn of C1-C5, ascending skull through foramen magnum
- **innervates sternocleidomastoid and trapezius muscles** to coordinate head movement
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hypoglossal (XII) nerve
- motor
-- somatic motor axons supply **tongue muscles** (during speech and swallowing)
209
An elderly relative suffered a CVA (stroke) and now has difficulty moving her right arm, and she also has speech problems.
What areas of the brain were damaged by the stroke?
Movement of the right arm is controlled by the left hemisphere’s primary motor cortex, located in the precentral gyrus.
Speech is controlled by the Broca’s area in the left hemisphere’s frontal lobe just superior to the lateral cerebral sulcus.
210
Nicky has recently had a viral infection and now she cannot move the muscles on the right side of her face.
In addition, she is experiencing a loss of taste and a dry mouth, and she cannot close her right eye.
What cranial nerve has been affected by the viral infection?
Nicky’s right facial (VII) nerve has been affected; she is suffering from Bell’s palsy due to the viral infection.
The facial nerve controls contraction of skeletal muscles of the face, tear gland and salivary gland secretion, as well as conveying sensory impulses from many of the taste buds on the tongue.
211
You have been hired by a pharmaceutical company to develop a drug to regulate a specific brain disorder.
What is a major physiological roadblock to developing such a drug, and how can you design a drug to bypass that roadblock so that the drug is delivered to the brain where it is needed?
You will need to design a drug that can get through the brain’s blood–brain barrier (BBB). The drug should be lipid- or water-soluble.
If the drug can open a gap between the tight junctions of the endothelial cells of the brain capillaries, it would be more likely to pass through the BBB.
Targeting the drug to enter the brain in certain areas near the third ventricle (the circumventricular organs) might be an option as the BBB is entirely absent in those areas and the capillary endothelium is more permeable, allowing the blood-borne drug to more readily enter the brain tissue.
212
What are the three layers of the cranial meninges, from superficial to deep?
dura mater, arachnoid mater, and pia mater
213
Where is CSF reabsorbed?
reabsorbed by the arachnoid granulations that project into the dural venous sinuses.
214
What part of the brainstem contains the pyramids?
The medulla oblongata contains the pyramids
215
what part of the brainstem contains the cerebral peduncles?
the midbrain contains the cerebral peduncles
216
What is the functional consequence of decussation of the pyramids?
Decussation = crossing to the opposite side.
each side of the cerebrum controls muscles on the opposite side of the body.
217
What is the importance of the cerebral peduncles?
the cerebral peduncles are the main sites through which tracts extend and nerve impulses are conducted between the superior parts of the brain and the inferior parts of the brain and the spinal cord.
218
Which structures contain the axons that carry information into and out of the cerebellum?
The cerebellar peduncles carry information into and out of the cerebellum.
219
What structure usually connects the right and left halves of the thalamus?
In about 70% of human brains, the interthalamic adhesion
220
What are the four major regions of the hypothalamus, from posterior to anterior?
the posterior hypothalamic area, intermediate hypothalamic area, anterior hypothalamic area, and preoptic area.
221
Which tracts carry impulses between cerebral gyri of the same hemisphere? Between cerebral gyri in opposite hemispheres? Between the cerebrum and thalamus, brainstem, and spinal cord?
- Association tracts connect cerebral gyri of the same hemisphere
- commissural tracts connect cerebral gyri in opposite hemispheres
- projection tracts connect the cerebrum with the thalamus, brainstem, and spinal cord
222
what is a major function of the corpus striatum/basal nuclei in the cerebrum?
- A major function of the corpus striatum is to help regulate initiation and termination of movements
- subconscious contractions of skeletal muscles (true laughter, automatic arm swings)
223
Which part of the limbic system functions with the cerebrum in memory?
The hippocampus is the part of the limbic system that functions with the cerebrum in memory
224
Where do axons in the olfactory tracts terminate?
Axons in the olfactory tracts terminate in the primary olfactory area in the temporal lobe of the cerebral cortex.
225
Where do most axons in the optic tracts terminate?
Most axons in the optic tracts terminate in the lateral geniculate nucleus of the thalamus.
226
Which branch of the oculomotor (III) nerve is distributed to the superior rectus muscle? Which is the smallest cranial nerve?
The superior branch of the oculomotor nerve is distributed to the superior rectus muscle; the trochlear nerve is the smallest cranial nerve.
227
How does the trigeminal (V) nerve compare in size with the other cranial nerves?
The trigeminal nerve is the largest cranial nerve.
228
Where do the motor axons of the facial (VII) nerve originate?
Motor axons of the facial nerve originate in the pons.
229
What structures are found in the vestibular and spiral ganglia?
The vestibular ganglion contains cell bodies from sensory axons that arise in the semicircular canals, saccule, and utricle; the spiral ganglion contains cell bodies from axons that arise in the spiral organ of the cochlea.
230
Through which foramen does the glossopharyngeal (IX) nerve exit the skull?
through the jugular foramen
231
Where is the vagus (X) nerve located in the neck region?
The vagus nerve is located medial and posterior to the internal jugular vein and common carotid artery in the neck.
232
How does the accessory (XI) nerve differ from the other cranial nerves?
The accessory nerve is the only cranial nerve that originates from both the brain and spinal cord.
233
What important motor functions are related to the hypoglossal (XII) nerve?
Two important motor functions of the hypoglossal nerve are speech and swallowing.
