Topic 19: Nervous System Flashcards
1
Q
what are the 2 divisions of the nervous system?
A
-central nervous system (CNS)
-peripheral nervous system (PNS)
2
Q
what is the central nervous system?
A
-command center
-brain + spinal cord
-processes + integrates info
3
Q
what does the peripheral nervous system consist of?
A
-cranial nerves
-spinal nerves
4
Q
where do the cranial nerves go?
A
-to/from the brain
5
Q
where do the spinal nerves go?
A
-to/from the spinal cord
6
Q
what are the 2 divisions of the PNS?
A
-sensory/afferent division
-motor/efferent division
7
Q
what is the sensory/afferent division of the PNS?
A
-arriving/going in to the CNS
-has sensory receptors that detect stimuli
-stimuli = changes in the internal/external environments
8
Q
what is the motor/efferent division of the PNS?
A
-exiting/going out of the CNS
-nerves convey impulses away from the CNS
-innervates (supplies nerves to) effectors
9
Q
what are effectors?
A
-muscles
-glands (exocrine or endocrine)
10
Q
what are the 2 cells in the nervous system?
A
-neurons
-neuroglia (glial cells)
11
Q
what are neurons?
A
-cells that conduct impulses
-make up the CNS + PNS
-mostly amitotic (irreplaceable)
12
Q
what is the structure of a neuron?
A
-cell body
-cell body processes (dendrites + axon)
-can be very long, but are very small in diameter
12
Q
which neurons are able to be replaced?
A
-taste
-olfaction
-memory
13
Q
what are the characteristics of the cell body of a neuron?
A
-contain typical organelles
-rough ER is called nissl bodies
-clusters of cell bodies in the CNS = nuclei (gray matter)
-clusters of cell bodies in the PNS = ganglia
14
Q
what is the purpose of dendrites?
A
-receive incoming messages and relay them to the cell body
15
Q
what is the purpose of the axon?
A
-carry impulses away from the cell body
16
Q
what are the parts of an axon?
A
-axon hillock
-axon terminal
17
Q
what is the axon hillock?
A
-where the axon meets the cell body
18
Q
what is the axon terminal?
A
-typically branched with synaptic end bulbs (enlarged tips)
-at the end of the axon
19
Q
what can change between axons?
A
-can be myelinated or unmyelinated
20
Q
what does it mean for an axon to be myelinated?
A
-wrapped in many layers of cell membrane (myelin sheath)
-gives support
-gives electrical insulation (increases signal speed)
21
Q
what are gaps in the myelin sheath called?
A
-nodes of ranvier (very small)
22
Q
what are the cells that make up the myelin sheath in the CNS? PNS?
A
-oligodendrocytes (CNS)
-schwann cells (PNS)
23
Q
where are there myelinated axon bundles?
A
-CNS = tracts (white matter)
-PNS = nerves
24
what are unmyelinated neurons?
-no myelin sheath
25
what are neuroglia (glial cells)?
-support neuron cells
-can undergo mitosis to be replaced
-prone to cancer/brain tumors
26
what are the 2 types of neuroglia (glial cells)?
-CNS neuroglia
-PNS neuroglia
27
what are the glial cells of the CNS?
-oligodendrocytes
-microglia
-astrocytes
-ependymal (neural epithelia)
28
what is the purpose of oligodendrocytes?
-produce myelin around the axon in the CNS
29
what is the purpose/function of microglia?
-protective
-become phagocytic if infected, dead or damaged neurons are detected
-because immune cells cannot enter the CNS
30
what is the purpose of astrocytes?
-surround blood capillaries to form part of the blood brain barrier (BBB)
-control capillary permeability of what is leaving + going to the brain
31
what is the purpose of ependymal (neural epithelia)?
-line brain ventricles + central canal of the spinal cord
-secrete cerebrospinal fluid (CSF) + circulate it (cillia)
32
what are the glial cells of the PNS?
-schwann cells
-satellite cells
33
what is the purpose of schwann cells?
-form myelin around axons in the PNS
34
what is the purpose of satellite cells?
-surround neuron cell bodies in ganglia
-protect + support
35
what are the structural types of neurons? what are they based on?
-unipolar
-bipolar
-multipolar
-based on the # of cell processes off of the cell body
36
what are unipolar neurons?
-1 process that divides into 2 (central and peripheral portions)
-peripheral end has dendrites (interact with sensory receptors for pain, touch, etc)
-remainder is the axon
-always sensory neurons
37
what are bipolar neurons?
-2 processes
-1 axon, 1 process with dendrites
-sensory (retina + nose (olfaction) )
38
what are multipolar neurons?
-3 or more processes
-1 axon + many dendrites
-all interneurons + motor neurons
-most common
39
what are the 3 functional types of neurons?
-sensory/afferent neurons
-interneurons
-motor/efferent neurons
-based on the direction of impulse conduction
40
what are sensory/afferent neurons?
-mostly unipolar
-impulses from sensory receptors to the CNS
41
what are interneurons?
-within the CNS
-impulses between sensory + motor neurons
-99% of neurons
-mostly multipolar
42
what are motor/efferent neurons?
-impulses from CNS to effectors
-all multipolar
43
what are the different neuron junctions?
-neuronal junction
-neuromuscular junction
-neuroglandular junction
44
what are neuronal junctions?
-neuron to neuron
-can be chemical (use neurotransmitters)
-can be electrical (use ions)
45
what are neuromuscular junctions?
-motor neuron to skeletal muscle
46
what are neuroglandular junctions?
-motor neuron to gland
47
what are the most common neuronal synapses?
-chemical neuronal synapses
48
what is the structure of a chemical neuronal synapse?
-presynaptic neuron
-axon terminal
-synaptic cleft
-postsynaptic neuron
49
what is the presynaptic neuron?
-neuron bringing the impulse
50
what is the purpose of the axon terminal in chemical synapses?
-the synaptic end bulbs (presynaptic membrane) has synaptic vesicles inside
-synaptic vesicles contain a neurotransmitter that will be diffused through the synaptic cleft to the postsynaptic neuron
51
what is the synaptic cleft?
-space between neurons
52
what is the postsynaptic neuron?
-receives the impulse
-has a postsynaptic membrane (cell membrane of dendrites or a cell body with receptor sites for the neurotransmitter)
53
what are the protective features of the central nervous system?
-bone
-meninges
-cerebrospinal fluid (CSF)
-blood brain barrier
-cerebral arterial circle
54
what is the bone that protects the CNS?
-the skull + vertebral column
55
what are meninges?
-CT around the brain + spinal cord
-3 layers
56
what are the layers of meninges?
-dura mater (outer)
-arachnoid mater (middle)
-pia mater (inner)
57
what are the characteristics of the dura mater in the brain?
-2 fused layers
-separated in spots to form spaces = venous (dural) sinuses (brain only)
-these sinuses contain blood
58
what is deep to the dura mater for both the brain + the spinal cord?
-subdural space
-filled with ISF
59
what are the characteristics of the dura mater in the spinal cord?
-1 layer
-superficial to the dura mater is the epidural space (spinal cord only)
-space is filled with fat, blood vessels, CT, etc (spinal cord only)
60
what are the characteristics of the arachnoid mater in the brain?
-avascular
-subarachnoid space (deep)
-has arachnoid granulations (brain only)
61
what are the characteristics of the arachnoid mater in the spinal cord?
-avascular
-subarachnoid space (deep)
62
what is the subarachnoid space?
-contains cerebrospinal fluid (CSF)
-web like strands of CT to secure it to the pia mater below
63
what are arachnoid granulations?
-project into the dural sinuses
-cerebrospinal fluid (CSF) enters the granulations to return to the blood (in the sinuses)
64
what are the characteristics of the pia mater in the brain and spinal cord?
-on the surface of the CNS
-vascular
65
what is meningitis?
-inflammation of meninges
66
what is cerebrospinal fluid (CSF)
-surrounds the brain + spinal cord
-in the brain ventricles + central canal of spinal cord
-cushions the CNS (brain buoyant)
67
what forms and produces cerebrospinal fluid (CSF)?
-formed from blood plasma (similar composition)
-produced by choroid plexuses (networks) (blood capillaries) found in each ventricle
68
what are the brain ventricles?
-spaces inside the brain (filled with CSF)
-2 lateral ventricles (1st + 2nd) (in cerebrum)
-3rd ventricle (in diencephalon)
-4th ventricle (surrounded by pons, medulla oblongata, cerebrum)
69
what is the central canal of the spinal cord?
-space in the spinal cord
70
what cells make the blood brain barrier? how do they do so?
-endothelial cells (of capillaries) with tight junctions
-astrocytes (foot processes wrap around the endothelial cells)
71
how does the blood brain barrier let stuff through?
-selectively permeable
-allows glucose + fat soluble material
-does not allow toxins, antibiotics, etc
72
what is the cerebral arterial circle?
-cerebral arteries form a circle at the base of the forebrain
73
what structures does the cerebral arterial circle circle?
-pituitary gland
-optic chiasma (where optic nerves cross)
74
what does the cerebral arterial circle unite?
-unites the two major blood supplies to the brain (anterior + posterior)
75
what does the cerebral arterial circle provide?
-an alternate route for blood if the vessels are blocked
76
what is the cerebrum?
-part of the forebrain
-has right + left cerebral hemispheres
-contains different lobes and surface features
-has 3 layers
77
what are the lobes of the cerebrum? how are they named?
-frontal
-temporal
-parietal
-occipital
-insula (deep to the temporal lobe)
-named after the cranial bones (overlying)
78
what are the surface features of the cerebrum?
-fissures (deep grooves)
-gyri (ridges)
-sulci (shallow grooves)
79
what are the 3 fissures of the cerebrum?
-longitudinal fissure
-transverse fissure
-lateral fissure
80
what do each of the fissures separate?
-long. = right + left cerebral hemispheres
-trans. = cerebellum + cerebrum
-lat. = temporal lobe from the rest of the cerebrum
81
what are two examples of gyri in the cerebrum?
-postcentral gyrus in the parietal lobe
-precentral gyrus in the frontal lobe
82
what separates gyri?
-sulci
83
what is an example of a sulci in the cerebrum?
-central sulcus between frontal + parietal lobes
84
what are the 3 layers of the cerebrum?
-cerebral cortex
-tracts
-basal nuclei
85
what is the cerebral cortex layer of the cerebrum?
-2-4mm thick
-gray matter
-has functional areas
86
what are the functional areas of the cerebral cortex?
-motor areas
-sensory areas
-association areas
-other
87
what are the characteristics of the motor areas in the cerebral cortex?
-all in the frontal lobe
-control skeletal muscle movement
-3 regions
88
what are the 3 regions of motor areas in the cerebral cortex?
-primary motor area (precentral gyrus)
-premotor area
-broca's area (motor speech)
89
what are the sensory areas in the cerebral cortex?
-general sensory area (pain, touch, temp, pressure)
-vision
-auditory + olfaction
-taste + visceral sensation
90
where is the general sensory area?
-postcentral gyrus in the parietal lobe
91
where is the vision sensory area?
-occipital lobe
92
where is the auditory + olfaction sensory area?
-temporal lobe
93
where is the taste + visceral sensation sensory area? what is an example of a visceral sensation?
-insula
-full bladder (feeling of internal organs)
94
what are association areas in the cerebral cortex? where are they?
-recognize info from memories
-parietal, occipital, temporal lobes
95
what are other sensory areas in the cerebral cortex? where are they?
-memory = temporal lobes
-conscious intellect (personality, learning, ideas, judgement, etc) = prefrontal cortex
96
what are tracts in the cerebrum?
-white matter
-3 types
97
what are the 3 types of tracts in the cerebrum?
-association tracts
-commissural tracts
-projection tracts
98
where do association tracts run from?
-gyrus to gyrus in the same hemisphere
99
where do commissural tracts run from? what is an example?
-gyrus to gyrus in opposite hemispheres
-ex: corpus callosum
100
where do projection tracts run from?
-vertically
-brain to spinal cord/spinal cord to brain
101
what are basal nuclei? what do they control?
-paired masses of gray matter (within white matter)
-control skeletal muscle movement
102
what is contained in the diencephalon of the brain?
-thalamus
-hypothalamus
-all gray matter
103
what is the thalamus?
-2 lobes connected by an intermediate mass (bridge through the 3rd ventricle)
-relay station for impulses coming to the cortex from the spinal cord
104
what is the hypothalamus?
-major regulator of the internal environment (visceral control) ex: blood pressure or heart rate
-inferior to thalamus, above the pituitary gland
105
what does the midbrain connect? what does it contain?
-connects pons + diencephalon
-contains cerebral aqueduct
106
what are contained in the anterior + posterior portions of the midbrain?
-anterior = cerebral peduncles (projection tracts)
-posterior = 4 nuclei (corpora quadrigemina)
107
what are the 4 nuclei of the midbrain posterior portion? what is their purpose?
-2 superior colliculi (visual reflexes)
-2 inferior colliculi (hearing)
108
what are the parts within the hindbrain?
-pons
-medulla
-cerebellum
109
what is the pons of the hindbrain?
-tracts between the brain + spinal cord
-tracts to/from the cerebellum
-pontine respiratory centers
-anterior to the cerebellum
110
what is the medulla of the hindbrain?
-2 bulges (called pyramids)
-3 vital centers
-several non vital centers
-inferior to the pons
-ends at the foramen magnum
111
what occurs just above the spinal cord?
-decussation (crossover) of pyramids
112
what are the 3 vital centers in the medulla?
-cardiac
-vasomotor (blood vessels)
-respiratory
113
what are the non-vital centers in the medulla?
-swallowing
-sneezing
-vomiting
114
what forms the brain stem?
-midbrain
-pons
-medulla
115
what is the cerebellum?
-has folds similar to gyri called folia
-cortex is grey matter
-arbor vitae (deep to cortex) is white matter
-coordinates skeletal muscle contraction (balance + posture)
-posterior to pons + medulla
116
what are the 2 functional systems of the brain?
-limbic system
-reticular formation
117
what is the limbic system?
-regulates emotions (laughing, crying, etc)
-nuclei in the cerebrum + diencephalon
-contains areas involved in memory (memories=emotional response)
118
what is the reticular formation?
-regulates alertness + attention
-sleepy when inhibited
-nuclei in brain stem
-cortex + thalamus + hypothalamus are involved
119
how does the reticular formation regulate alertness + attention?
-filters stimuli
-only sends new/unusual signals to other brain areas
120
what happens if the reticular formation is damaged?
-coma
121
what forms the reticular activating system (RAS)?
-cortex
-thalamus
-hypothalamus
122
what is the basic structure of the spinal cord?
-foramen magnum to L1/L2 (conus medullaris)
-nerves continue down through vertebral foramina as cauda equina (horses tail) (exit at intervertebral foramina)
-contains filum terminale
123
what is contained within the forebrain?
-cerebrum
124
what is the filum terminale?
-CT extension of the pia mater
-anchors the conus medullaris of the spinal cord to the coccyx
-where cerebrospinal fluid (CSF) samples are taken
125
what is contained within the cross sectional structure of the spinal cord?
-anterior median fissure
-posterior median sulcus
-central canal
-grey matter
-white matter
126
what does the anterior median fissure and posterior median sulcus separate?
-separates the spinal cord into right + left halves
127
what does the central canal of the spinal cord contain?
-cerebrospinal fluid (CSF)
128
what is the grey matter of the spinal cord?
-cell bodies + dendrites of motor neurons + interneurons
-H shaped
129
what is the crossbar of the gray H-shaped matter? what about the horns?
-cross bar = gray commissures
-dorsal horn = receives sensory information
-lateral horn = motor response
-ventral horn = motor response
130
what is the white matter of the spinal cord?
-myelinated axons
-contains ascending (sensory) tracts
-contains descending (motor) tracts
-forms 3 columns
131
what are the 3 columns of white matter in the spinal cord?
-dorsal column
-lateral column
-ventral column
132
what are the functions of the spinal cord?
-sensory + motor impulses
-produces reflexes
-fast + predictable + automatic responses to changes in environment
-ex: withdrawal reflex (arm away from a hot stove)
133
what cranial nerves are associated with the forebrain?
- I olfactory
- II optic
134
what cranial nerves are associated with the midbrain?
- III oculomotor
- IV trochlear
135
what cranial nerves are associated with the pons?
- V trigeminal
- VI abducens
- VII facial
- VIII vestibulocochlear
136
what cranial nerves are associated with the medulla oblongata?
- IX glossopharyngeal
- X vagus
- XI accessory
- XII hypoglossal
137
which 2 pairs of nerves are only sensory neurons?
- I olfactory
- II optic
138
which pair of cranial nerves is mainly sensory neurons?
- VIII vestibulocochlear
139
what are the remaining 9 pairs of cranial nerves composed of?
-mixed nerves
-both sensory + motor neurons
140
where are the cell bodies of the remaining cranial nerves motor neurons located?
-brainstem nuclei
141
where are the cell bodies of the remaining cranial nerves sensory neurons located?
-ganglia of the PNS
142
what is the motor and sensory function of the trigeminal nerve (V)
-motor = chewing
-sensory = conveys sensations (touch, pressure, pain, temp) from face to the CNS
143
how many pairs of spinal nerves are there? are they all one type of neuron or mixed?
-31pairs
-all mixed nerves
144
where is the location of all 31 spinal nerve pairs?
-8 cervical
-12 thoracic
-5 lumbar
-5 sacral
-1 coccygeal
145
where do the spinal nerves exit?
-exit at the intervertebral foramina
-except the 1st exits between the atlas + occipital bone
146
what are the 2 points of attachment to the spinal cord for each spinal nerve?
-dorsal root
-ventral root
147
what is in the dorsal root?
-sensory neurons with cell bodies in the dorsal root ganglion
148
what is in the ventral root?
-autonomic + somatic motor neurons with cell bodies in the ventral or lateral horn
149
what forms a spinal nerve?
-the joining of the dorsal + ventral roots
150
what do the spinal nerves immediately divide into?
-branches called rami
151
what are the 3 rami called?
-dorsal ramus
-ventral ramus
-rami communicantes
152
what does the dorsal ramus do?
-innervates (supplies with nerves) the skin + muscles of the back
153
what does the ventral ramus do?
-forms throacic nerves (T2-T12)
-also may further branch + join to form nerve plexuses (nerve network)
154
what are the 4 spinal nerve plexuses?
-cervical
-brachial
-lumbar
-sacral
155
what spinal nerves form the cervical spinal nerve plexus? what is the important nerve that arises?
- C1 - C5
-phrenic (innervates the diaphragm)
156
what spinal nerves form the brachial nerve plexus? what are the important nerves that arise?
- C5 - C8, T1
-axillary, radial, ulnar, median, musculocutaneous
157
what spinal nerves form the lumbar nerve plexus? what is the important nerve that arises?
- L1 - L4
-femoral
158
what spinal nerves form the sacral nerve plexus? what are the important nerves that arise?
- L4 - S4
-sciatic, divides into tibial + common fibular nerves
159
what is the rami communicantes?
-connect the ventral ramus to the sympathetic trunk
-contains autonomic nerve fibres (neurons)
160
what are the CT wrappings of a nerve?
-epineurium (around whole nerve)
-perineurium (around fascicles) (groups of nerves)
-endoneurium (around axon + myelin)
161
what is the path in the sensory (afferent) division?
-stimulus > receptor > CNS
162
what does the sensory (afferent) division of the PNS consist of?
-receptors
-first order neurons
163
what is the purpose of receptors?
-to detect changes in the environment
164
how are receptors classified?
-location
-type of stimulus received
-structure of the receptor (general senses only)
165
what are the different location receptors?
-exteroceptors
-interoceptors
-proprioceptors
166
what stimulus do exteroceptors detect? where are they? what senses?
-stimulus in the external environment
-receptors are at the body surface
-touch + special senses
167
what stimulus do interoceptors detect? where are they?
-stimulus in the internal environment
-in viscera (organs), blood vessels, etc
168
what are proprioceptors?
-monitor body position (stretch receptors, muscle spindles)
-balance + movement
-located in joints, skeletal muscles, etc
169
what are the receptors classified by their type of stimulus?
-mechanoreceptors
-thermoreceptors
-chemoreceptors
-photoreceptors
-nociceptors
170
what do mechanoreceptors detect?
-mechanical stimuli
-pressure, touch, hearing
171
what do thermoreceptors detect?
-temperature
172
what do chemoreceptors detect?
-chemical
173
what do photoreceptors detect?
-light
174
what do nociceptors detect?
-pain
175
what are the two structures of a receptor?
-free nerve endings
-encapsulated nerve endings
176
what are free nerve endings?
-terminal dendrites of unipolar sensory neurons
-ex: pain, root hair plexus
177
what are encapsulated nerve endings?
-terminal dendrites enclosed in CT
-ex: meissner's + pacinian corpuscles
178
what are first order neurons?
-unipolar neuron attached or associated with a receptor (may be encapsulated instead of free)
-axon travels in cranial/spinal nerves to the CNS
179
where are the cell bodies of the first order neurons?
-sensory ganglia of cranial nerves
-dorsal root ganglia of spinal cord
180
where are the axon terminals of the first order neurons?
-brain
-dorsal horn of the spinal cord
181
what is the path in the motor (efferent) division of the PNS?
-CNS > effector
182
what are the 2 subdivisions of the motor (efferent) division of the PNS?
-somatic
-autonomic
183
what is the somatic division of the motor (efferent) division of the PNS?
-skeletal muscle = effector (voluntary)
-consists of lower motor neurons
184
what are lower motor neurons?
-single multipolar neuron
-cell bodies in the CNS and axons in the PNS
185
where are the cell bodies of neurons located in the somatic division of the motor (efferent) division of the PNS?
-ventral horn of the spinal cord
-motor nuclei of the brainstem (ex: facial motor nucleus for the cranial nerve VII)
186
what is the autonomic division of the motor (efferent) division of the PNS?
-smooth muscle, cardiac muscle, glands = effector (involuntary)
-2 consecutive multipolar neurons from the CNS to the effector
187
what are the 2 neurons of the autonomic division?
-preganglionic neuron
-postganglionic neuron
188
what is the preganglionic neuron?
-myelinated
-cell body in the brain stem or lateral horn of the spinal cord (in the CNS)
189
what is the postganglionic neuron?
-unmyelinated
-cell body in the autonomic ganglion (outside the CNS)
190
what are the 2 subdivisions of the autonomic division of the PNS (efferent)?
-sympathetic (SNS)
-parasympathetic (PSNS)
191
what is the sympathetic nervous system (SNS)?
-triggers fight or flight
-preganglionic neuron cell body is in the lateral horn (T1-L2)
-autonomic ganglia = trunk ganglia or collateral ganglia
-postganglionic neuron has a longer axon (bigger response)
-exit the CNS mainly as thoracic nerves
192
where is the trunk ganglia?
-either side of the vertebral column
193
what is the parasympathetic nervous system (PSNS)?
-rest + digest
-preganglionic neuron cell body is in the brain stem + S2-S4 (sacrum)
-autonomic ganglia = terminal ganglia
-postganglionic neuron has a short axon (smaller response)
-exit the CNS mainly via the vagus nerve (cranial nerve X)
194
where is the terminal ganglia?
-at or in the organ/effector wall
194
what are the two nervous system pathways?
-ascending (sensory)
-descending (motor)
195
what is an ascending nervous pathway?
-conducts impulses from general sense receptors into the brain
-3 consecutive neurons from the receptor to the cortex
196
what are the 3 consecutive neurons in the ascending pathways?
-first order neuron
-second order neuron
-third order neuron
197
where does the first order neuron of the ascending pathway lead? what type of neuron?
-receptor to the spinal cord (PNS)
-sensory neuron
198
what type of neuron is the second order neuron in the ascending pathway?
-interneuron, multipolar (CNS)
199
where is the cell body of the second order neuron in the ascending pathway?
-dorsal horn of the spinal cord or medulla (CNS)
-decussates (crosses over) in the medulla
200
what type of neuron is the third order neuron in the ascending pathway?
-interneuron, multipolar (CNS)
201
where is the cell body of the third order neuron in the ascending pathway? where does it impulse?
-in the thalamus
-impulses to the postcentral gyrus (sensory cortex) (CNS)
202
what forms the ascending spinal tracts?
-axons of the first and second order neurons
203
what are the 3 ascending spinal tracts?
-dorsal (posterior) column tract/pathway
-spinothalamic tract/pathway
-spinocerebellar tract/pathway
204
what is the dorsal (posterior) column tract/pathway?
-receptors could be free nerve endings or meissners
sensations can be precisely located (touch)
205
what is the spinothalamic tract/pathway
-temperature + pain receptors
-non-specific
-difficult to localize
206
what is the spinocerebellar tract/pathway?
-ascending tracts from the spinal cord to cerebellum
-receptors = proprioceptors (body position)
-no third order neuron, second order goes directly to the cerebellum
-no conscious perception because there is no crossing over (decussation)
207
what is a descending nervous pathway?
-conduct impulses from the brain to the effector
-2 neuron pathway
208
what are the 2 neurons in the descending pathway?
-upper motor neuron
-lower motor neuron
209
what is an upper motor neuron? where are their cell bodies located?
-multipolar interneurons
-cell bodies are in the cortex or brainstem nuclei
-in the CNS
210
what forms the descending spinal tracts?
-axons of the upper motor neurons
211
what are the 2 descending spinal tracts?
-corticospinal tracts
-indirect tracts
212
what is the corticospinal tract?
-cell bodies are in the cerebral cortex
-tracts mainly cross over (decussate) in the medulla
213
what is the indirect tract?
-cell bodies are in the brainstem nuclei
-receive impulses from the motor cortex, basal nuclei, and cerebellum
214
what is the relationship between the CNS and PNS?
-receptors detect stimuli
-afferent division of the PNS has sensory neurons that go into the CNS
-efferent division of the PNS has motor neurons that leave the CNS
-effectors execute a response (muscles + glands)
215
what is an example of how the CNS and PNS works together?
-hand touches something hot (stimulus) triggers a sensory receptor
-triggers the CNS and creates a response
-pull hand away (effector)
216
what are the 2 divisions of the motor/efferent division of the PNS?
-somatic (skeletal muscle)
-autonomic (smooth muscle, cardiac muscle, and glands)
217
what are the 2 divisions of the autonomic division of the motor/efferent division of the PNS
-sympathetic (SNS, fight or flight)
-parasympathetic (PSNS, rest and digest)
218
what is the pathway for production and reabsorption of CSF?
-produced by the choroid plexuses
-secreted into the lateral ventricles (1st + 2nd)
-moves into the 3rd ventricle via the interventricular foramina
-moves into the 4th ventricle via the cerebral aqueduct
-moves into the subarachnoid space of the brain and spinal cord via median (1) and lateral (2) apertures
-absorbed into the dural sinus (venous blood) via arachnoid villi
-moves to the internal jugular veins and to the heart
-then moves into arterial blood and goes back to the choroid plexuses
219
what is the posterior blood flow to the brain?
-vertebral arteries > basilar artery > posterior cerebral arteries (part of the circle)
220
what is the anterior blood flow to the brain?
-internal carotid arteries > middle cerebral arteries (not part of the circle)
-internal carotid arteries > anterior cerebral arteries (part of the circle) > anterior communicating artery (part of the circle)
-internal carotid arteries > posterior communicating artery (part of the circle)
221
how does blood return from the brain posteriorly?
-cerebral arteries > capillaries > cerebral veins > dural sinuses > superior vena cava
222
what does the anterior communicating artery join?
-the two anterior cerebral arteries
223
what are the 2 bulges/pyramids in the medulla?
-large motor tracts
-part of corticospinal tracts
224
how many cranial nerves are there?
-12 pairs
225
where is the collateral ganglia?
-close to large abdominal arteries
