1
Q
How is the brain protected?
A
-cranium provides a rigid outer layer of protection
- connective tissue layers surround and partition brain
2
Q
What are the types of connective tissue layers that surround and part the brain?
A
- dura matter
-pia matter - arachnoid matter
3
Q
How do connective tissue layers protect and support brain?
A
-encloses and supports blood vessels serving the brain
-contains circulating CSF
- interior blood-brain barrier structures selectively control movement of materials between circulating blood and brain tissue
4
Q
What is the dura mater of the cranium?
A
- tough double layer (meningeal and periosteal) of connective tissue that forms outer meningeal membrane
5
Q
What are the layers of the dura matter?
A
-outer periosteal
-meningeal
6
Q
What is dura matter made of?
A
- collagen, dense irregular connective tissue
7
Q
What does the outer periosteal layer do?
A
- forms periosteum on the internal surface of cranial bones
-fused with meningeal layer in most places
8
Q
What does the meningeal layer do?
A
- innermost dura matter layer
9
Q
What layer is also called true dura matter?
A
-meningeal layer
10
Q
What is the dural sinus?
A
- acts as modified vein collecting venous blood and CSF
11
Q
Where is the dural sinus?
A
found in space between periosteal and meningeal layers
12
Q
What is the dural septa?
A
-when two meningeal layers meet and extend inwards
13
Q
What does the dural septa do?
A
- partitions specific regions of the brain, providing support and stabilization
14
Q
What are the dura matter spaces?
A
-epidural space
-subdural space
15
Q
What is the epidural space of the cranium?
A
a potential space that contains arteries and veins and support the bones of the cranium and meninges
16
Q
What is the subdural space of the cranium?
A
- a potential space found between the dura and arachnoid matter where fluid can collect
- usually not present but can appear when filled with blood and other fluid
17
Q
When do epidural and subdural hematomas occur in the cranium?
A
when blood pools in these regions and compresses blood regions
18
Q
What causes epidural hematomas?
A
- High-impact traumatic injury
19
Q
What causes subdural hematomas?
A
- usually violent movement or sharp turn breaks blood vessels
20
Q
What is arachnoid matter?
A
- connective tissue membrane located next to, deep of, subdural space
21
Q
What is arachnoid matter made of?
A
- arachnoid trabeculae
22
Q
What are arachnoid trabeculae?
A
-collagen and elastic extensions
23
Q
Where is arachnoid trabeculae located
A
-transverse to subarachnoid space
24
Q
What does arachnoid trabeculae do?
A
connects superficial arachnoid matter to deep pia matter
25
What drives CSF movement?
- pressure gradient
-CSF pressure is greater than venous pressure
26
What do arachnoid villi do?
- help move CSF from subarachnoid space to dural sinus
27
How does CSF move?
- CSF forms in the ventricles of the brain and drains into and circulates through, the subarachnoid space of the meninges
- CSF goes from subarachnoid space into villi and transports into dural sinus where it mixes with venous blood
- ciliated ependymal cells beat synchronously aiding in the movement of CSF through ventricles and into subarachnoid space
28
What is a granulation?
- a collection of villi
29
What is pia matter?
- innermost, thin meningeal layer that adheres to the contours of the brain surface
- tender
30
What is a fissure?
- deep-defined depression in the brain surface
- in pia matter
31
What is a gyrus?
-elevated regions of the cerebral cortex
-in pia matter
32
What is a sulcus?
- shallow groove in the cerebral cortex
-in pia matter
33
Where is the choroid plexus found?
-each of the four ventricles
34
Where does CSF form?
- 30% forms at the choroid plexus
35
How does CSF circulate through the ventricles?
- lateral- interventricular foramen- 3rd- cerebral aqueduct- fourth before being routed into the subarachnoid space through the meninges
- small amounts of CSF enters the central canal of the spinal cord from 4th ventricle but most goes from the fourth ventricle to the subarachnoid space through lateral and medial apertures
36
What ventricle has the most CSF?
lateral because its the biggest
37
What are the CSF functions?
- buoyancy
-protection
-environment stability
-supports nervous tissue
38
How does CSF provide buoyancy?
- reduces brain's weight by 95%
39
How does CSF provide protection?
-adds liquid cushion
40
How does CSF provide environment stability?
- helps with the transport of nutrients and wastes
-protects against fluctuations
41
How does CSF support nervous tissue?
-plays prominent role in brain development and homeostasis
42
What does the choroid plexus do?
- forms a selective barrier that determines what materials move from blood plasma into ventricles, forming CSF
43
What is the choroid plexus made of?
- capillaries, pia matter, ependymal cell
-capillaries bc CSF is product of blood
44
Where are all the places CSF is made?
-30% at choroid plexus
-additional CSF across ependymal cells lining ventricles 30%
- fluids moving into subarachnoid space 40%
45
How does CSF follow the pressure gradient?
-CSF pressure > ventricular pressure
- flows through subarachnoid space to arachnoid villi to dural sinuses, following the pressure gradient
46
What is the blood brain barrier?
- highly selective semipermeable barrier thast regulates which substances enter brain's interstitial fluid
47
How do ependymal cells modify CSF so it has a unique composition?
-more Na+ and Cl-
-less K+, Ca2+, glucose
-compared to blood plasma
48
What does the blood brain barrier do?
-helps prevent neuron exposure to harmful substances such as drugs and waste products
- protects the brain from hormones and NT fluctuation, maintaining a constant environment
49
What is the blood brain barrier made of?
-endothelial cells
-astrocytes
50
What do endothelial cells do for the blood brain barrier?
-reduced permeability
-continuous basement and tight junctions between ells and pericytes
51
What do astrocytes do for the blood-brain barrier
- perivascular feet that surround the capillaries
- gatekeepers that selectively allow certain substances to cross
52
What is allowed to cross the blood-brain barriers and is ok?
- h20
-respiratory gases
-glucose
-soluble
53
What can cross the blood-brain barrier that you want to prevent
- drugs (cocaine, nicotine, caffeine, meth)
- alcohol
-pathogens
-medicine
54
Where is the blood-brain barrier missing or reduced
-choroid plexus
-hypothalamus
- pineal gland
55
Why is the blood-brain barrier missing or reduced in the hypothalamus and pineal gland?
its where we produce hormones that need to travel through the blood
56
How many hemispheres and lobes does the cerebrum have?
-2 hemispheres
- 5 lobes per hemisphere
57
What makes up the diencephalon?
-thalamus
- hypothalamus
- epithalamus
57
What are the parts of the brainstem?
-pons
-medulla oblongata
- midbrain
58
How much O2 does the brain receive?
20%
59
What percentage of body weight is the brain?
2%
60
Why is the brain highly folded?
increases surface area for neurons
61
What is another name for the cerebral cortex?
seat of intelligence
-enlarged in humans compared to other animals
62
Why do humans have larger frontal lobes?
allows for higher level functions
63
Is the brain ipsilateral or contralateral?
contralateral?
64
What does contralateral mean for the brain?
- cerebral hemispheres receive sensory info and send motor controls to the opposite side of the body
65
What does lateralization mean for the brain?
-each hemisphere specializes in specific high-order functions (like speech)
-still has some functional overlap tho
66
What percentage of the brain's weight is the cerebrum?
- 85%
67
What connects the left and right hemispheres of the cerebrum?
- corpus calllosum
68
What is the corpus callosum?
- longitudinal fissure with axons "tracts"
-connects left and right sides
69
What does the frontal lobe control?
- voluntary movement
- decision making
- personality
-communication
70
What are the major parts of the frontal lobe?
-primary motor cortex
- premotor cortex
- frontal eye field
- motor speech area
71
What does the primary motor cortex control?
voluntary motor movement
72
What does the premotor cortex do?
- plans movements (skilled/learned movements like playing the piano)
-plans things that require coordination
- just plans, doesn't cause the muscle contraction
73
What does the frontal eye field control?
- eye movement muscles (where you look)
- helps with binocular vision
74
What is binocular vision?
you can see and focus both eyes on one spot
75
What is the motor speech area?
- controls muscles used for speech
76
What does the parietal lobe do?
- receives inputs related to touch and body positions; conscious of sensations received
77
What are some major parts of the parietal lobe?
- somatosensorry association
-somatosensory cortex
78
What does the somatosensory association area do?
-integrates sensory info allowing us to identify objects based on previous experience
- identifies pressure, texture, temperature, shape
79
What does the somatosensory cortex do?
receives info from skin and proprioceptors
80
What are proprioceptors?
muscle and joint receptors
81
What is the occipital lobe responsible for?
- receives, processes, stores visual info
82
What are the major parts of the occipital lobe?
- primary visual cortex
-visual association area
83
What is the primary visual cortex?
- receives and processes incoming visual info
84
What does the visual association area do?
- integrates color, movement, and form to identify things we see based on memory
85
What is the temporal lobe in charge of?
hearing and smelling
86
What are the parts of the temporal lobe?
- primary auditory cortex
- auditory association cortex
-primary olfactory cortex
87
What does the primary auditory cortex do?
-receives and processes sound
88
What does the auditory association cortex do?
-interprets sounds
-stores and retrieves memories of sound
89
What does the primary olfactory cortex do?
conscious awareness of smells
90
What is the insula in charge of?
-hidden cortex
- memory and interpretation of taste
91
What cortex is the primary gustatory cortex a part of?
insula
92
What is the primary gustatory cortex in charge of?
- processing taste information
93
What is the cerebrum overall in charge of?
-intelligence and reasoning
- conscious thought, memory , judgement
-voluntary motor, visual auditory activities
94
What are petalias part of?
cerebrum
95
What are petalias?
-slight enlargement related to handedness
-part of lateralization
- ex. right-handed people have right frontal petaliass, left occipital petalias
96
Is there ever lateralization overlap?
yes especially for complex functions
97
What does the left side of the brain control?
- speech
- categorical things like math
Wernicke's area is in left, controls language comprehension
98
What does the right side of the brain control?
- representational lings like visual-spatial relationships
-art and music
99
How are jobs in the brain divided?
- 50% function in right 50% function in left
100
By what age is lateralization established
5
101
How is the brain sexually dimorphic?
- males have more lateralization - suffer more loss when a hemisphere is damaged - thicker corpus callosum
- females have bilateral language processing - more coordination between hemispheres
102
What does the prefrontal cortex do?
- retrieves and coordinates info from multiple areas of the brain
- involved in planning future behaviors, evaluating consequences, decision making, impacts behavioral choices made based on societal norm
103
What age does the prefrontal cortex develop into?
develops into the 20s
104
What is gray matter made of?
- cell bodies
-dendrites
-unmyelinated axons
105
What is white matter made of?
myelinated axons
106
What are tracts?
- bundles of parallel axons in the CNS
107
What are cerebral nuclei?
- internal clusters of gray matter embedded within white matter
-not like nucleus
108
What are association tracts?
- bundles of axons that connect regions of the cerebral cortex within the same hemisphere
- localized to only R or L hemispheres
109
What are arcuate fibers?
-part of association tracts
- connects areas in the same lobe
110
What are longitudinal fasciculi?
-part of association tracts
-connects different lobes
-runs the length of the hemisphere like posterior to anterior...
111
What are projection tracts?
-link cerebral cortex to inferior brain regions and spinal cord
-contains decussation
112
What is the decussation?
where crossing over occurs
113
What are commissural tracts?
-link right and left hemispheres
- corpus callosum = largest
-also anterior commissure
114
What is the Diencephalon thalamus?
-contains right and left thalamic bodies, each with multiple groups of nuclei that are connected by the intermediate mass
115
What are the functions of the diencephalon thalamus?
- thalamus is the final relay point for incoming sensory info
- info is processed and selectively sent to the coordinating cerebral region
- acts as an info filter, relaying some signals to cortex but not others
- gateway to cerebral cortex
116
What is the largest region of the diancephalon?
thalamus
117
What is the diencephalon hypothalamus?
- connected to te pituitary gland through the hypothalamus
118
What are the functions of the diencephalon hypothalamus?
- controls the autonomic nervous system
- controls endocrine system
-regulation of body temp
- emotional behavior
- food intake regulation
-water intake regulation
-sleep-wake cycle
119
How does the diencephalon hypothalamus control the autonomic nervous system?
sends signals to brain stem in order to regulate HR, BP, respiration
120
How does the diencephalon hypothalamus control the endocrine system?
- secretes hormones
-regulates hormones
-hypothalamus affects pituitary and pituitary affects everything else
121
How does the diencephalon hypothalamus control body temp?
detects altered temperature and signals to heat or cool body
122
How does the diencephalon hypothalamus control emotional behavior?
-part of the limbic system, controls emotional responses like pleasure or fear etc..
123
How does the diencephalon hypothalamus control food intake?
- monitors nutrient levels and regulates hunger
124
How does the diencephalon hypothalamus control water intake?
monitors concentration of dissolved substances in blood and regulates thirst
125
How does the diencephalon hypothalamus control the sleep wake cycle?
directs pineal gland in its role to regulate sleep-wake cycles
126
Where is the diencephalon hypothalamus located?
below thalamus
127
What are the parts of the diencephalon epithalamus?
-pineal gland
- habenuclear nuclei
128
What does the pineal gland do?
- the endocrine gland that secretes melatonin
-helps regulate circadian rhythm
129
When should melatonin levels be highest?
at night when you are sleeping
130
What is the circadian rhythm?
day-night cycles
131
What effects melatonin?
- light inhibits melatonin formation
132
What is the habenuclear nuclei?
-involved in visceral and emotional responses to odors
-helps keep us from eating spoiled food
133
What is the limbic system?
- composed of multiple cerebral and diencephalic structures that collectively process and experience emotions, form memories, and regulate motivation
-"emotional brain"
134
What are the parts of the limbic system?
-cingulate gyrus
-hippocampus and parahippocampus gyrus
- amygdaloid body
-olfactory structures
135
What is the cingulate gyrus and what does it do?
- receives input from other components of limbic system
136
What is the hippocampus and parahippocampus gyrus and what does it do?
- assists in storing and forming long-term memory
-neurogenesis of adult stem cells occurs here
137
What is the amygdaloid body and what does it do ?
- involved in several aspects of emotion, especially fear
- attaches emotions to memories
138
What do the olfactory structures do?
- processes odors that can provoke emotions
139
What are the olfactory structures?
- bulbs
- tracts
- olfactory cortex
140
What are the parts of the midbrain?
- cerebral peduncle
-superior cerebellar peduncle
- substantia nigra
-tectum
- tegmentum
141
What does the cerebral peduncle do?
-motor tract that relays voluntary motor command from the primary motor cortex of each cerebral hemisphere
- think of tracts like highways
-white matter
142
What does the superior cerebellar peduncle do?
- tracts that connect cerebellum to midbrain
143
What does the substantia nigra do?
-nuclei that house neurons that produce dopamine which is involved in controlling movement, emotional responses, pleasure and pain response
- has melatonin pigments
144
What does degeneration in the substantia nigra cause?
parkinsons
145
What is the tectum?
-sensory nuclei that controls visual reflex and tracking
- controls auditory reflexes
146
What is the tegmentum?
- contains red nuclei and reticular formation
-integrates info from the cerebrum and cerebellum
- issues involuntary motor commands to help maintain posture, bend, and walk (uses back muscles to do this)
147
What is the pons?
- contains sensory and motor tracts connecting the brain and spinal cord
- houses sensory and motor cranial nerve nuclei (trigmenial, abducens, facial?
148
What does the pons contain?
-middle cerebellar peduncle
- pontine respiratory center
- superior olivary nuclei
149
What is the middle cerebellar peduncle?
- contains axons that connect the pons and cerebellum
150
What is the pontine respiratory center?
- contains autonomic nuclei that regulate breathing and transitions between inspiration and expiration
- works with medulla oblongata to regulate the skeletal muscles of breathing, and how deep of a breath
151
What is the superior olivary nuclei?
- involved in multiple pathways for hearing including sound source and localization
152
What is the medulla olongata?
- most inferior part of the brainstem, continuous with the spinal cord
- contains sensory and motor tracts that connect brain and spinal cord
153
Where are the decussation of pyramids?
-medulla oblongata
154
Where does crossing over occur?
-decussation pyramids of medulla oblongata
155
What does crossing over cause?
contralateralization
156
What does the inferior olivary nucleus do?
- part of medulla oblongata
- sends ascending sensory signals
157
What are inferior cerebellar peduncles?
- part of medulla oblongata
- tracts connecting the medulla oblongata to the cerebellum
158
What do nucleus cuneate and nucleus gracillas do?
-relay sensory info to the thalamus
159
What are the parts of the medulla oblongata?
- inferior olivary nucleus
-inferior cerebellar peduncles
- cranial nerve nuclei
- nucleus cuneate
-nucleus gracillias
- vestibulocochlear, glossopharyngeal, vagus, accessory, hypoglossal nerves
- autonomic nuclei
-cardiac vascular centers
- medullary respiratory center
160
What are the parts of the cardiac vascular center?
- cardiac center
- vasomotor center
161
What does the cardiac center of the medulla oblongata do?
- regulates HR and cardiac output
162
What does the vasomotor center of the medulla oblongata do?
- controls blood vessel diameter
-vasodilation and vasoconstriction affect how much blood gets to an area and blood pressure
163
What does the medullary respiratory center do?
-controls breathing rate and communicates with the pontine respiratory center
164
What are the misc. functions of the respiratory center?
- coughing, sneezing, vomiting, salivating, swallowing
165
What is the cerebellum made of?
- 2 hemispheres connected by vermis
-each hemisphere has an anterior and posterior lobe
- contains surface folds called folia
-outer gray cerebral cortex and nuclei with internal white abor vitae
- superior, middle, inferior cerebellar peduncles
166
What are folia?
- surface folds of the cerebellum
167
What do the superior, middle, inferior cerebellar peduncles do?
-connect cerebellum to midbrain, pons, medulla
168
What are the functions of the medulla?
- coordinates and fine tunes movements, helps maintain equilibrium and posture (note not initiate)
-may generate error-correcting signals to be sent to premotor and primary motor cortex
- ensures muscle activity follows the correct pattern
- stores memories of previously learned movements
- helps maintain equillibrium and posture
169
How does the cerebellum maintian equillibrium and posture?
receives proprioceptive info from muscles and joints
170
Describe the spinal cord?
- extends inferiorly from medulla oblongata to conus medullaris (approx, L1 level)
- Widens at cervical and lumbosacral enlargements due to neurons leading to upper and lower limbs
- has roots from spinal nerves that contain sensory and motor signals
- spinal cord and associated structures (cauda aquina) are encapsulated by spinal meninges, but contain some distinct features
171
Where do the roots of lumbar, sacral, and coccygeal nerves go?
- extend inferior from the conus medullary until they exit the intervertebral foramen forming the cauda equina
- root grows as spinal cord ascends during the fetal development
172
What makes up the spinal meninges?
- dura mater
-epidural space
- no dural sinuses or septa
173
Describe spinal dura mater?
- single layer
-provides stability
-surrounds roots and fuses with connective tissues surrounding nerves
174
Describe the spinal epidural space?
- unique to spinal meninges (only potential in cranial)
- lies between dura mater and inner walls of the vertebra
- has areolar connective tissue, blood vessels, and adipose tissue
-epidural anesthesia induced here
175
What does the spinal cord have instead of dural sinus or septa?
-meningeal layer (dural sheath)
- meninges surround roots
176
What makes up the arachnoid space of the spinal cord?
-arachnoid mater
-subarachnoid space
177
What is arachnoid mater?
connective tissue layer with arachnoid trabeculae that extends into subarachnoid space
178
What is the subarachnoid space of the spinal cord?
-continuous with cranial meninges filled with CNS
179
Describe pia mater of the spinal cord?
- innermost meningeal layer that adheres to the surface of the spinal cord
180
What are the extensions of the pia mater of the spinal cord?
- denticualte ligaments
- filum terminale
181
What are denticulate ligaments?
- triangular extensions of spinal pia mater that attaches to dura mater
- laterally stabilizes spinal cord
182
What is the filum terminale?
- extends from conus medullary to coccyx bone through cauda equina
-stabilizes spinal cord superior and inferiorly
183
What parts of the pinal associated structures are gray matter?
-anterior horm
-posterior horn
-lateral horn
184
What is the posterior horn made of?
- interneuronn cell bodis and dendrites
185
What does the posterior horn connect with?
axons of sensory neurons lead to cell bodies and dendrites of interneurons
186
What is the lateral horn made of?
- cell bodies and dendrites of autonomic motor neurons
187
What does the lateral horn connect with?
- axons of interneurons lead to cell bodies and dendrites of autonomic motor neurons
- innervate cardiac muscle and smooth muscle
188
Where are lateral horns found?
- t1-l2
189
What are anterior horns made of?
- cell bodies and dendrites of somatic motor neurons
190
What does the anterior horn connect with?
- axons of interneurons lead to cell bodies and axons of somatic motor neurons and form synapse with skeletal muscle
191
What does the funiculus contain?
all funiculi contain sensory tracts tracts
- only anterior and lateral contain motor tracts
192
What are tracts?
myelinated axons that have a shared origin, destination, and function
193
what are motor tracts?
descending tracts that go from the brain
194
What are sensory tracts?
-descending tractings going from the brain
195
What does the posterior root contain?
- axons of sensory neurons whose somas are in the posterior root ganglion and lateral and anterior horns have motor neurons
196
What does the anterior root contain?
- axons of motor neurons whose somas are in spinal cord
197
How are mixed signals formed?
- roots unite within intervertebral foramen to form mixed spinal nerve
198
What are mixed nerves?
carries both sensory and motor signals
199
What is a monosynaptic reflex?
- direct communication between sensory and motor neuron
-ex = stretch reflex
200
What are polysynaptic reflex?
- interneuron facilitates sensory-motor communication
-ex: withdrawal reflex
201
What is a reflex?
- rapid, programmed, involuntary reflex of muscles or glands to a stimulus
- survival mechanism
202
Where do anterior roots lead?
-spinal cord
203
What are all spinal nerves?
-mixed nerves
204
What is the gray commisure?
- where signals are sent between right and left spinal cord gray matter
- little circle= central canal filled with CSF
205
What is a nerve?
- where roots fuse
206
What are the parts of the nerve?
-epineurium
-perineurium
- endoneurium
207
What is the epineurium?
- thick layer of dense iregular connective tissue
-encloses entire nerve
208
What is the perineurium?
- layer of dense irregular connective tissue
-wraps bundles of axons
-supports blood vessels
209
What is the endoneurium
- has capillaries that supply the axon
-a delicate layer of areolar connective tissue
- separates and insulates each axon
210
What do the posterior and anterior rami have in common?
- mixed nerves
-branch from spinal nerves
-somatic
211
What does the posterior ramus do?
-innervates muscles and skin of back
212
What does the anterior ramus do?
- splits into multiple other branches
-at different levels, the ramus innervates the anterior and lateral trunk and limbs
- some anterior rami weave together forming aneerve plexus
213
Do most thoracic spinal nerves and d1-s5 form a plexus
no
214
What do the grey and white communicants have in common?
- both are associated with autonomic NS
-connect spinal nerves to sympatetic trunk
215
What do white rami communicantes do?
-carry myelinated preganglionic sympathetic axons T1-L2 nerves to the trunk
- "entrance ramps" to the trunk
216
What do gray rami communicanted do?
- carry unmyelinated postganglionic sympathetic axons from the trunk to all spinal nerves
- "exit ramps" from trunk
217
What is the sympathetic trunk ganglion?
-ganglia interconnected in sympathetic trunk, parallel to vertebral column
218
How is the nervous system divided?
- CNS and PNS
-PNS to sensory and efferent
Efferent to autonomic and somatic
- Autonomic to sypathetic and parasympathetic
219
What is the CNS
-integrative control center
220
What is the CNS made of?
brain and spinal cord
221
What is the PNS made of?
-cranial and spinal nerves
222
What does the PNS do?
communication between CNS and body?
223
What is the sensory pns made of?
sensory neurons
224
the efferent pns do?
conducts signals from the CNS to effectors
225
What is the efferent PNS made of?
motor neurons
226
What does the autonomic PNS do?
controls involuntary responses
227
What does the somatic motor system do?
controls voluntary movements
228
What does the sympathetic motor system do?
-mobilizes body systems
-fight or flight response
229
What does the parasympathetic autonomic motor system do?
- conserves energy
- rest and digest response
230
What does the motor pathway do?
- descending pathway that transmits neural signals from the brain to specific skeletal muscle effectors
231
What are the two types of motor neuron?
-upper and lower
232
Where is the cell body of the upper motor neuron located?
-in the brain (cerebral cortex, cerebral nucleus, or brainstem nuclei)
233
What does the axon of the UMN do?
- leads down and directly synapses with the cell body of the LMN
234
Where is the cell body of the lower motor neuron located?
- spinal cord
-where in spinal cord depens on the LMN
235
Where does the LMN exit?
- exits through cranial nerves and innervates effector (skeletal muscles)
-would go to head or neck
236
Where does the axon of the UMN of the motor tractgo?
-travels through the corticobulbar or corticospinal tracts before synapsing with the LMN
237
What is the corticobulbar tract and what is it made of?
- tract consists of UMN that synapses with LMN at the cranial nerve nuclei in the brain stem
238
What is the corticospinal tract?
- tract has lateral and anterior paths with UMN in brain
239
Where is the UMN soma?
cerebral cortex
240
Where do myelinated LMN travel?
- goes from cns to the effector (skeletal muscle) by exiting through the anterior root spinal cord and anterior and posterior ramus
241
Where is the UMN cell body in the direct pathway?
- Primary motor cortex of the frontal lone
242
What is the bulbar tract? (put all the pieces together)
- cell body of UMN is located in the primary motor cortex, axon of UMN synapses with cell body of LMN at the cranial nerve
- takes projection tracts
- axon of LMN axon exits from cranial nerve, innervating head and neck of skeletal muscle
243
What are the two types of corticospinal tracts?
-anterior and lateral
244
How does the lateral side of the spinal tract travel?
- decussate in pyramids of medulla oblongata and continue down the contralateral side of spinal cord through lateral funiculus until they synapse with LMN
- LMN is found in anterior horn at spinal cord
- LMN exits spinal cord through anterior root and subsequent spinal nerve leading to voluntary muscles of the limb it serves
245
How does the anterior corticospinal tract travel?
the spinal cord before decussation occurs at gray commissure and axon synapses with LMN in the anterior horn of the spinal cord at the level of the spinal nerve in which it exits innervating voluntary muscles of the back
- synapses with cell body of LMN of the opposite side
246
How are roots formed?
rootlets fuse to form them
247
What does the dura mater cover?
everything
248
Is there arachnoid villi in the spinal meninges
no
249
What is the auricle of the ear?
-outer part of ear
-contains earwax, hair, made of cartilage
250
What do the autonomic and somatic pathways have in common?
- consist of upper and lower motor neuron which carries signal to a lower motor neuron
- lower motor neuron always innervates the effector
251
What is the somatic pathway?
- UMN soma in brain synapses with single LMN
- UMN axon travels through corticobulbar or corticospinal tracts
- LMN cell body is in the brainstem or spinal cord
- axon of LMN travels through cranial and spinal nerves to skeletal muscle effector
252
What is the autonomic pathway?
- UMN soma in brain and axon synapses with 1st of 2 LMN
- 2lmn are preganglionic or postganglionic
- axon of preganglionic LMN exits CNS and synapses with postganglionic neurons at ganglia where postganglionic soma is
- postganglionic axon travels to the autonomic effector (cardiac muscle to skeletal muscle effector)
253
Where does the preganglionic soma receive signals from?
UMN
254
Where does the preganglionic axon synapse?
- synapses with soma of the postganglionic neuron at autonomic ganglia
255
Where does the postganglionic axon carry signals?
to the effector muscle
256
Where are preganglionic somas
-localized to the CNS
- parasympathetic are craniosacral
-sympathetic are thoracolumbar
257
What is dual innervation?
- when most effectors recieve input from sympathetic and parasympathetic divisions
258
What are antagonistic effectors?
- parasympathetic and sympathetic signals often have opposing effects on the same effector which is achieved through the release of different NT binding different receptors at the same organ
259
What do cholinergic synapses do?
- synthesizes and releases ACH
260
What do adrenergic synapses do?
synthesizes and releases norepinephrine and epinephrine
261
How do adrenergic and cholinergic receptors work at the same time?
1. preganglionic axon releases ACH
2. ganglionic neuron cell body and dendrites always contain ACH receptors
3. postganglionic axon releases ACH or NE
4. target cells contain ACH receptors or NE
262
Do adrenergic and nicotinic receptors cause EPSP or IPSP?
-could be both depending on the receptor cells
263
What is the tympanic membrane and what does it do?
- eardrum
- carries vibrations into the middle ear
- separation between inside and outside ear
264
What does the tympanic cavity do?
- small earbones that form bridge from tympanic membrane to inner ear (auditory ossibles)
- amplifies sound waves
- filled with air
265
What is the eustachian tube?
- connects tympanic cavity to throat
- lots of bacteria exchange
- children's are shorter and more horizontal
266
What is the stapes?
- leads to inner ear
267
What is the chochlea?
- where hearing recepors are located, within spiral organ
268
Where is the vestibule?
- ear
269
What do semicircle canals do?
- help maintain equilibrium and angular acceleration
270
What does the vestibular apparatus do?
- maintains equilibrium with semicircle canals
271
What does equilibrium do?
- awarness and monitoring head position
272
What is linear equillibrium?
- straight line, no twisting and turning
273
What is static equillirum?
- no movement
274
What is the vestibular apparatus made of?
- utricle and saccule
275
Where is the ampulla of semicircle canals?
base of semicircle canall
276
Where is the crista ampullaris?
ampulla
277
What is the crista ampullaris?
- region of mechanoreceptors for dynamic equilibrium
278
What does the cupula do?
bends stereocilia and changes hair cell voltage in semicircle canals
279
What happens if stereocilia bends towards the kinocilium?
- hair cell depolarizes
280
What happens if stereocilia bends away from the kinocillium?
- hair cell hyperpolarizes
281
What is the maculaof the ear?
- receptor for static equilibrium and linear acceleration within utricle and saccule
- has hair cells with single kinocilium and stereocilia which are embedded in gelatinous otolithic membrane
282
Where are otoliths?
-in the gel-like matrix of the ear
283
What do otoliths do?
- add weight and help pull membrane as movement occurs
284
What is the macula have instead of the cupula?
- otolithic membrane
285
What happens when the head is tilted up?
depolarization
286
What happens when the head is tilted away?
hyperpolarization
287
When are hair cells firing?
always
288
What does the spiral organ do?
- fluid pressure waves in the scala vestibuli push the vestibular membrane causing pressure waves in the endolymph of the cochlear duct
- specific regions of the baislar membrane move distorting hair cells
289
What are the steps in cochlear hair cell stimulation?
- contain ion channels at their tips and tip link proteins that connect them
- hair cells bathed in K+-rich endolymph that is more positive than the fluid inside cell
- when the basilar membrane moves up hair cells are pushed into the tectorial membrane and their tips are tilted causing the links to pull open ion channel causing K+ to diffuse into hair cell depolarizing it
- hair cells release NT from its bsae, exciting the sensory neuron and initiating an AP
290
What happens when the baislar membrane moves down?
hair cell stimulation processes quickly reverses
291
What are the steps in hearing?
1. sound waves directed by auricle into the external acoustic meatus causing the tympanic membrane to vibrate
2. tympanic membrane vibration moves auditory ossicles (malleus, incus, stapes)
3. fluid at the oval window generates pressure waves in perilymph within scala vestibuli
4. fluid pressure waves in scala vestibuli push the vestibular membrane causing pressure waves in cochlear
- spiral organs are distorted initiating nerve signals in a cochlear branch of the vestibulocochlear nerve
5. remaining pressure waves are transferred to the perilymph within the scala tympani and are absorbed as the round window slightly buldges
292
What is pitch?
-depends on the frequency of vibrating object
293
What pitch can humans hear?
- 20-20,000 hz
294
What do high frequency sounds do?
- excites cell in narrower, stiff baislar membrane near oval window `
295
What do low frequency sounds do?
- excites cell in wider flexible baislar membrane near the apex
296
What's the sclera?
- tough, outer vascularized white of eye
297
What is the pupil?
- black hole in iris that controls how much light gets in
298
What does the pupil do in high light?
constricts
299
What does the pupil do in low light?
dilates
300
What is the pigmented layer of the retina?
- absorbs extraneous light and provides vitamin A for photoreceptors
-attached to choroid
301
What is neural layer of the retina?
- where phototransduction occurs (light energy converted into an electrical signal)
- houses photoreceptors and associated neurons
302
What is the ciliary body?
- muscles that support and change the shape of the lens (attached to the suspensory ligament) and processes that secrete aqueous humor
- aqueous humor travels through pupil into anterior chamber and is released into scleral venous sinus
- changes shape of iris
303
What is the choroid?
- blood vessels supply retina and melanin absorb light preventing it from scattering
304
What does the lens do to an image?
- flips it
305
What are the general vision steps?
1. light rays enter eye as they pass through the cornea, aqueous humor and go to through pupil
2. lens focuses the light on the retina through the vitreous humor
3. photoreceptors respond to light by creating an electrical signal which gets carried through the optic nerve to the brain
306
What is the iris?
- pigmented and vascularized and contains muscles which control the pupil diameter therefore controlling te amount of light entering the eye (pupil reflex)
- seperates anterior and posterior chamber
307
What form of innervation is pupil constriction?
- parasympathetic
308
What form of innervation is pupil dialation?
sympathetic innervation
309
What does ciliary body contraction do?
- ciliary body closer to the lens, rounds it, and lets us focus on things close up
- called accommodation
310
What does ciliary body relaxation do?
- lens flattens, suspensory muscles taught, distance vision
311
What do the ciliary processes do?
- produce aqueous humor and fills anterior cavity
312
What are phtoreceptors?
- contains photopigments that react to light which triggers a change in membrane potential
313
What are rods?
- more specialized than cones
- specialized for dim light and night vision
- cant do color or sharp vision
314
What are cones?
- less numerous than rods
- only worked in bright light
- specialized for color recognition and sharpness
- subdivided into blue, green and red
315
What are bipolar cells?
- receive input from photoreceptor cells and send the info to ganglion cells
316
What are ganglion cells?
- respond to bipolar cells and sends AP when stimulated, axons gather at optic disk and from optic nerve
317
Where are photopigmentation disks?
- outer region of photoreceptors
318
Where are photopigments embedded?
-outermembrane
319
What are photopigments made of?
-rhodopsin and opsin
320
How are photopigments formed?
with vitamin A
321
What type of phtopigment do rods have?
-rhodopsin
- most sensitive to 500nm
322
What type of photopigments do cones have?
- opsins
-red blue and green
323
What does the form of opsin control?
- the wavelength range of light transduced
324
What is the rod photocycle?
Light
1. rhodopsin absorbs light rays
2. cis-retinal transformed to trans-retinal
3. separates retinal and opsin breaking rhodopsin apart, opsin activated (bleaching reaction)
Dark
4. transretinal is reconverted to cis-retinal within pigmented layer using ATP
5. cis-retinal associates with opsin to re-form rhodopsin
325
Where does the rod photocycle occur?
in photopigments
326
What is the rod light electrical cycle?
1. stimulation of light hyperpolarizes photoreceptors due to closing of cation channels
2. no glutamate mean bipolar cell is no longer inhibited and therefore becomes hyperpolarized releasing glutamate and stimulating the ganglion cell to fire sending nerve cell to brain
327
What is the rod dark electrical signal?
1. no light - photoreceptor depolarized due to opening of cation channels casing it to continously release glutamate
2. glutamate gauses hyperpolarization of bipolar cell inhibiting signaling
328
What is the optic disk?
- has no photoreceptors, blind spot
- where ganglion axons exit towards the brain
329
What is the macula lutea?
- rounded, yellow region lateral to disk
- has cones
- site of macular degeneration
- has fovea centralis
330
What is macular degeneration?
- leading cause of blindness, physical deterioration of macula lutea
331
What is the fovea centralis?
- highest area of cones
- area of sharpest vision
332
What is the peripheral retina?
- contains primarily rods
- functions most effectively in low light
333
What is emmetopia?
normal vision
334
What is myopia?
- nearsighted
- trouble seeing far away
- only rays close to eye focus on retina
- corrected iwth concave lens
335
What is hypertropia?
- farsighted
- trouble seeing upclose
- only convergent rays from distance points focus
- corrected with a convex lens
336
What is an astigmatism?
- unequal focusing
- unequal curvatures in one or more retroactive surface
337
Bio 240
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