Physiology of the Nervous System- Module 2, 3, & 4 Flashcards
(294 cards)
1
Q
The somatic system consists of:
- Somatosensory
- Somatomotor
What kind of fibers are in each part?
A
- Somatosensory: afferent fibers + ascending pathway
- Somatomotor: efferent fibers (spinal) + descending pathway (brain & spinal)
2
Q
The autonomic system has how many afferent and efferent nerves?
A
1 afferent
2 efferent
3
Q
The peripheral nervous system is the segment of the nervous system that controls:
A
the activities of the internal organs as well as skeletal muscle
4
Q
What are the two parts of the peripheral nervous system?
A
- Autonomic (sympathetic & parasympathetic & enteric)
- Somatic
5
Q
Which nervous system is involuntary and has short-lived actions?
A
autonomic
6
Q
What part of the spinal cord is the sympathetic nervous system located in?
A
thoracolumbar
7
Q
What part of the spinal cord is the parasympathetic nervous system located in?
A
craniosacral
8
Q
Any nerve that emerges from T1-L2 is what kind of nerve?
A
sympathetic
9
Q
What are the only cranial nerves that are parasympathetic?
A
- oculomotor (3)
- facial (7)
- glossopharyngeal (9)
- vagus (10)
10
Q
The sympathetic chain is made up of several ____ _____.
A
paravertebral ganglions
Paravertebral chain ganglia, also known as sympathetic chain ganglia or sympathetic trunk ganglia, are a series of nerve cell bodies located bilaterally on either side of the spinal column. They form a chain that extends from the base of the skull to the coccyx. These ganglia are part of the sympathetic nervous system and serve as relay stations for sympathetic nerve signals.
11
Q
What is the function of the white rami?
A
to connect the preganglionic fibers to the sympathetic chain
12
Q
What is the function of grey rami ?
A
To connect the postganglionic fibers to the sympathetic chain
13
Q
For sympathetic nerve supply to the head and thoracic region, the 1st synapse is located at the ______ _____.
A
sympathetic chain
14
Q
For sympathetic nerve supply to the pelvic and abdominal regions, the 1st synapse is:
A
outside of the sympathetic chain
15
Q
What are the 4 basic functions of the ANS (autonomic nervous system)?
A
- Maintaining/ regulating ongoing visceral organ function in the body cavity and head region
- Adapting the animal to environmental changes
- Maintaining homeostasis
- Responding to stress threatening animal survival
16
Q
The autonomic nervous system is further divided into:
A
- sympathetic
- parasympathetic
- enteric
17
Q
What is the enteric nervous system?
A
Specialized neurons for the contraction of smooth muscle in the GIT
18
Q
What is the sympathetic chain? What is its function?
A
When spinal nerves exit the spinal cord as sympathetic nerves, they run into an organized framework of ganglia called the sympathetic chain on either side of the spinal cord, which allows for an organized arrangement of nerves
19
Q
The ANS is involved in the release of chemical _________.
A
neurotransmitters
20
Q
What do spinal nerves and cranial nerves supply?
A
- visceral organs and muscles
- external structures
Visceral organs in dogs are the soft, internal organs located within the body cavity, including those of the digestive, respiratory, circulatory, excretory, and reproductive systems.
21
Q
Which division of the nervous system is responsible for innervations to visceral organs?
A
autonomic (sympathetic and parasympathetic)
22
Q
Which division of the nervous system is responsible for innervations to skeletal muscles?
A
somatic (sensory and motor)
23
Q
What are 3 other names for the autonomic nervous system?
A
- vegetative nervous system
- visceral nervous system
- involuntary nervous system
24
Q
What is the general function of sympathetic nerves?
A
to regulate the activity of the visceral organs antagonistic to parasympathetic nerves
25
Cranial nerves that supply visceral organs of the body and exert an antagonistic effect on the sympathetic action of the same organ are:
parasympathetic
26
What is the name of the 3rd cranial nerve?
oculomotor
27
Where does the oculomotor nerve innervate?
1 - superior rectus
2 - medial rectus
3 - inferior rectus
4 - inferior oblique
5 - levator palpebrae superioris muscles
(all of which are responsible for eye movement and eyelid elevation. Additionally, it carries parasympathetic fibers to the pupillary sphincter and ciliary muscles, which control pupil size and lens shape)
28
What is the name of the 7th cranial nerve?
facial
29
What does the facial nerve innervate?
parasympathetic innervation to the:
- facial muscles
- salivary glands
30
What is the name of the 9th cranial nerve?
glossopharyngeal
## Footnote
glosso means tongue
31
Where does the glossopharyngeal nerve innervate?
parasympathetic innervation to the:
- pharynx
- baroreceptor reflex of the heart
32
What is the name of the 10th cranial nerve?
vagus
33
Where does the vagus nerve innervate? What kind of innervation is this?
parasympathetic innervation to the:
- visceral organs of the head region
- heart
- lungs
- stomach
- liver
- bladder
- superimposition over the enteric nervous system
34
What does the pelvic nerve innervate? What kind of innervation is this?
Parasympathetic innervation to the reproductive system
35
grey matter is located at the _____ portion of the spinal cord
interior portion
36
white matter is located at the ______ portion of the spinal cord
exterior portion
37
What covers the spinal cord for protection?
3 layers of meninges
38
What is the path of a sensory nerve?
runs from a tissue to the grey matter of the spinal cord
39
what is the path of a motor nerve?
runs from the grey matter of the spinal cord to the tissue
40
How do motor sympathetic nerves associate with the sympathetic chain
attach to the paravertebral ganglia via grey and white rami
41
how are paravertebral ganglia named?
according to their location with respect to the vertebral column:
- cervical (superior, middle, inferior)
- thoracic
- lumbar
- sacral
42
where do sensory fibers and motor fibers enter and exit the grey matter
sensory: enter through the dorsal horn
motor: exit through the ventral horn
43
where do sympathetic motor fibers and somatic motor fibers have their cell bodies located within the grey matter
visceral (sympathetic): cell bodies in the intermediolateral horn of the grey matter
somatic: cell bodies in the ventral horn of the grey matter
44
what are nerves within the grey matter of the spinal cord called and where are they located
interneurons in the lateral horn
45
what is the difference in the location of the synapse between sympathetic preganglionic nerve fibers in the thoracic vs abdominal regions
thoracic: paravertebral ganglia in the sympathetic chain
abdominal: prevertebral ganglia
46
what are the names of the main prevertebral ganglia
- celiac ganglion
- superior mesenteric ganglion
- inferior mesenteric ganglion
47
What is the difference in the length of pre- and postganglionic nerve fibers between sympathetic and parasympathetic nerves
- Parasympathetic nerves have long preganglionic and short postganglionic fibers
- Sympathetic nerves have short preganglionic and long postganglionic fibers
48
How many cranial nerves are in the body?
12
49
How many Spinal nerves are in the body?
(The number varies among species)
50
What are nerves that emerge directly from the brain (including the brain stem) called?
cranial nerves
51
What are nerves that emerge from the segments of the spinal cord called?
spinal nerves
52
Each ___ nerve is paired and present on both sides
cranial nerve
53
What is the numbering of cranial nerves based on?
the order in which they emerge from the brain (from front to back)
54
Which 2 nerves emerge from the cerebrum or forebrain, while the remaining 10 pairs arise from the brain stem (lower part of the brain)?
- olfactory nerves
- optic nerves
55
Cranial nerve 1 is called:
Olfactory nerve
56
Cranial nerve 2 is called the:
Optic nerve
57
Cranial nerve 3 is called the:
Oculomotor nerve
58
Cranial nerve 4 is called the:
Trochlear nerve
59
Cranial nerve 5 is called the:
Trigeminal nerve
60
Cranial nerve 6 is called the:
Abducens nerve
61
Cranial nerve 7 is called the:
Facial nerve
62
Cranial nerve 8 is called the:
Vestibulochoclear nerve
63
Cranial nerve 9 is called the:
Glossopharyngeal nerve
64
Cranial nerve 10 is called the:
Vagus nerve
65
Cranial nerve 11 is called the:
Accessory nerve
66
Cranial nerve 12 is called the:
Hypoglossal nerve
67
What is the function of cranial nerve 1(olfactory nerve)?
smell
68
What is the function of cranial nerve 2 (optic nerve)?
vision
69
What is the function of cranial nerve 3 (oculomotor nerve)?
controls 4 extrinsic eye muscles, the elevator palpebrae superioris, and the pupillary sphincter muscle
70
What is the function of cranial nerve 4 (trochlear nerve)?
controls the superior oblique
71
where are neurotransmitters released in nerve fibers
both at the target organ and at the synapse
72
What neurotransmitter is released at all ganglia
ACh
73
what neurotransmitter is released at the target organ by sympathetic nerves
norepinephrine
74
what neurotransmitter is released at the target organ by parasympathetic nerves
ACh
75
What is the overall functions of the autonomic nervous system
- regulator of organ function in the face of endogenous or exogenous factors that may alter their function
- adaptation to environmental changes
- maintaining homeostasis
- stress response
- informs CNS of conditions of the organs of the body (afferent)
76
how many afferent and efferent fibers are present in the ANS
1 afferent, 2 efferent
77
What is the purpose of the release of NT's by sympathetic and parasympathetic nerve fibers
ensures that the action potential is transmitted from the pre to the post ganglionic fibers and they exert control on the target organ
78
Neurotransmitters exert their receptor mechanism on what 3 structures
smooth muscle, cardiac muscle, and glands
79
where is the cell body located of a preganglionic autonomic nerve fiber
brain or spinal cord
80
Where is the cell body located of a postganglionic autonomic nerve fiber?
Ganglia
81
The effects of the SNS and PSNS are ____________.
Antagonistic
82
Most tissues receive nerve fibers from ___________________.
SNS and PSNS
83
What 4 structures of the body only receive innervation from one part of the ANS and what are they?
- Uterus: sympathetic only
- Pyloerector muscles: sympathetic only
- Sweat glands: sympathetic only
- Blood vessels: sympathetic only
84
How are sweat glands an exception to the normal distribution of neurotransmitters?
Postganglionic sympathetic nerve fibers release ACh instead of norepinephrine.
85
All ganglia have what type of receptor?
Cholinergic
86
All parasympathetic postganglionic nerve fibers, as well as sweat glands, have what type of receptor?
Cholinergic
87
All sympathetic(??) postganglionic nerve fibers, as well as adrenal glands, have what type of receptors?
Adrenergic
88
What is a nonadrenergic, noncholinergic system (NANC)?
Regions where neither ACh or NE are predominant, but rather other neurotransmitters such as dopamine, serotonin, or glutamate.
89
What is the difference in the type of saliva produced by the salivary gland depending on the type of innervation (sympathetic vs parasympathetic)?
Sympathetic: scant and viscous saliva
Parasympathetic: watery and profuse saliva
90
Postganglionic sympathetic nerve fiber cell bodies are located where?
At the paired paravertebral ganglion chain and several prevertebral ganglia.
91
Why are chromaffin cells of the adrenal medulla described as part of the SNS?
They behave like a postganglionic fiber of the sympathetic nervous system in that they are stimulated by ACh to produce norepinephrine or adrenaline.
92
The sympathetic nervous system is made up of less than _______% sensory fibers.
20%
93
The sympathetic nervous system supplies mainly what?
Blood vessels
94
How do sympathetic nerves relate to skeletal muscles of the somatic nervous system?
The release of ACh at the neuromuscular junction.
95
Describe NANC systems of the SNS.
Release of dopamine at postganglionic fibers in renal, mesenteric, and coronary vascular beds and by interneurons in sympathetic ganglia.
96
What are 8 of the major effects of the SNS on the body?
- Increased heart rate
- Increased blood pressure
- Pupil dilation
- Bronchodilation
- Lowered GIT motility
- Cutaneous and mucosal vasoconstriction
- Dilation of coronary blood vessels and blood vessels of skeletal muscles
- Glycogenolysis
97
Sensory input from the parasympathetic system is ____% of the vagus nerve and ____% of the pelvic nerve.
80%, 50%
98
What are the characteristics of the PSNS?
- Discrete activation which usually occurs at the individual organ level
- Limited level of neuronal divergence from CNS to ganglia and to target tissues
- Cholinergic at all levels of neuronal connections (synapses)
99
Parasympathetic innervation is dominant in what structures?
- Heart: relaxes the heart
- Eyes: constricts pupils
- Gut: increases motility, digestion, and absorption
- Bladder: regulates micturition reflex
100
Describe Horner's syndrome.
Horner's syndrome, which is a lack of sympathetic innervation to the eye, is usually caused by damage to the sympathetic nerve supply which can be associated with damage to the brachial plexus since that is where the cranial cervical ganglion is located.
101
How does parasympathetic innervation regulate the micturition reflex of the bladder?
M3 stretch receptors of the bladder are innervated by parasympathetic nerves.
102
What is the function of glial cells?
Provide mechanical support and nutritive support by secreting neurotrophins to neurons.
103
Where are glial cells found?
In both the central and peripheral nervous systems.
104
What types of glial cells are found in the peripheral nervous system?
Satellite cells and Schwann cells.
105
What types of glial cells are found in the central nervous system?
Oligodendrocytes, astrocytes, microglia, and ependymal cells.
106
What is the function of satellite cells?
Satellite cells support cell bodies by providing anchorage and fixing them in place.
107
What is the function of Schwann cells?
Schwann cells secrete neurotrophic factors and form myelin sheaths (provide insulation and protective coat); helps amplify the velocity of conduction along nerve fibers.
108
What is the function of oligodendrocytes?
Form myelin sheaths; Schwann cells of the PNS do what oligodendrocytes do in the CNS for neuronal tracts/interneurons.
109
What is the function of astrocytes?
Astrocytes form support for CNS, help form BBB by attaching to blood capillaries at the endothelial pores to limit the ability for solutes to leak from the capillaries, secrete neurotrophic factors, and take up K and NT's during neuronal reuptake/extraneuronal reuptake.
110
What is the most populous glial cell?
Astrocytes
111
What is the population of astrocytes a good indication of?
Healing in the case of a traumatic brain injury.
112
What is the function of microglia?
- Modified immune cells; act as macrophages
- Clean and mop up the brain and spinal cord of infectious agents.
113
What is the function of ependymal cells?
- Compartmentalize the ventricles of the brain, which act as flow channels for CSF
- Act as a barrier between the blood vessels and the choroid plexus cells of the ventricles that produce the CSF, as well as line the central canal in order to act as a buffer and shock absorbers.
114
What is a neurotransmitter?
Chemical substance that acts as the mediator for the transmission of nerve impulses from one neuron to another neuron through nerve connections called a synapse.
115
Why are neurotransmitters released?
They are released for systemic and local effects of synaptic transmission.
116
How do neurotransmitters act out their function?
By binding to membrane-bound transmitter receptors.
117
What are the 4 major neurotransmitters?
ACh, NE, epinephrine, and dopamine (kidney and coronary vessels).
118
What are the 3 minor neurotransmitters?
Serotonin, substance P, vasoactive intestinal peptide, and others.
119
What all do cholinergic fibers innervate?
- Both preganglionic of SNS and PSNS, and postganglionic of PSNS synapses
- Postganglionic synapses of sweat glands (species variable)
- Some blood vessels
- Skeletal muscles of the somatic motor systems (neuromuscular junctions via nicotinic receptors and muscarinic receptors).
120
What all do adrenergic fibers innervate?
- SNS postganglionic fibers
- Adrenal medullary cells release epinephrine and to a lesser extent norepinephrine via chromaffin cells.
121
What is the difference between epinephrine and norepinephrine?
The absence of a methyl group in norepinephrine.
122
How does the adrenal medulla have more epinephrine than norepinephrine?
Adrenal medulla contains the enzyme that converts it from norepinephrine to epinephrine, called phenylethanolamine-N-methyltransferase.
123
Dopamine is released by sympathetic fibers located where, and what is it dependent on?
Renal, mesenteric, coronary vascular beds, and interneurons in the sympathetic ganglia; dependent on the presence of certain enzymes.
124
Where and how is ACh synthesized?
Synthesized within neurons by the enzyme choline acetyltransferase (ChAT) via the precursors acetyl CoA and choline.
125
Where and how is ACh degraded?
Degraded by hydrolysis in the synaptic cleft by the enzyme acetylcholinesterase (AChE) into acetate and choline.
126
Where is AChE found?
In the postganglionic membrane.
127
What happens after ACh is degraded?
Acetate is metabolized and choline is recycled back to the presynaptic membrane to make more ACh.
128
What are the 2 types of cholinergic receptors?
Nicotinic and muscarinic.
129
Where are nicotinic receptors found?
Autonomic ganglia, adrenal medulla, and NMJ of skeletal muscles.
130
What are the subclassifications of nicotinic receptors?
Nc receptors in autonomic ganglia
Ns receptors in NMJ and CNS.
131
Where are muscarinic receptors located at?
- Postganglionic parasympathetic nerve terminals supplying organs like the heart, smooth muscles, trachea, GIT, bladder, and the exocrine glands
- Present in CNS.
132
What type of receptors are muscarinic receptors?
Membrane protein receptors that are coupled to G-proteins; function by the production of 2nd messengers.
133
How are muscarinic receptors sub classified?
M1-M5 (tissue dependent).
134
Are muscarinic receptors excitatory or inhibitory?
Can be either depending on the type of effect desired on the target organ.
135
Why are the receptors called muscarinic or nicotinic?
Animals affected by the parasympathetic response tend to mimic those that have been exposed to nicotine or muscarine.
136
What are the characteristics of adrenaline (epinephrine)?
- Generally referred to as a catecholamine
- Synthesized from tyrosine as a precursor.
137
How is adrenaline synthesized?
- Tyrosine is converted to 3,4-dihydroxyphenylalanine or dopa by tyrosine hydroxylase
- Dopa is converted to dopamine by dopa-decarboxylase
- Dopamine is converted to norepinephrine by dopamine-beta-hydroxylase
- Norepinephrine may be converted to epinephrine by phenylethanolamine-N-methyltransferase.
138
What kind of reaction is the conversion from dopa to dopamine?
Decarboxylation reaction.
139
Where is the enzyme phenylethanolamine-N-methyltransferase very prominent?
In the adrenal medulla.
140
What are the 2 major types of adrenergic receptors?
Alpha and beta.
141
What are the 2 types of alpha adrenergic receptors?
Alpha-1: contraction/excitation (increased AP and vasoconstriction)
Alpha-2: relaxation (hyperpolarization of smooth and cardiac muscle; vasodilation/bradycardia).
142
What are the different types of beta adrenergic receptors?
Beta-1: slow contraction; do not excite
Beta-2: slow contraction; do not excite
Beta-3: not very important; regulation of metabolism and energy.
143
Which is the main excitatory adrenergic receptor?
Alpha-1.
144
What is the classification of adrenergic receptors based on?
Their relative affinities for various adrenergic agonists.
145
What do beta-1 and beta-2 adrenergic receptor subtypes stimulate?
The formation of the enzyme adenylate cyclase through the G-protein (GMP).
146
What is the messenger pathway of beta 1 and beta 2 receptors?
- Stimulate the formation of the enzyme adenylate cyclase through GMP
- Converts ATP to cyclic-AMP, which is the 2nd messenger that will open Na channels.
147
What is a secondary function of beta adrenoreceptors?
Activate (open) L-type calcium channels in membranes; Ca moves out of the cell and it becomes hyperpolarized: no excitation.
148
Norepinephrine acts on which adrenoreceptors?
Alpha 1 and alpha 2.
149
What is the messenger pathway of alpha 1 receptors?
- Phospholipase-C and alpha 1 receptor produce DAG and IP3
- DAG activates phosphokinase-C for vasoconstriction
- IP3 pulls Ca from the smooth ER for vasoconstriction.
150
What is the messenger pathway of alpha 2 receptors?
Inhibitory; antagonizes the conversion of ATP to cAMP by the beta receptors; still works with adenylate cyclase.
151
Which NT's are responsible for the messenger pathway of beta 1 and beta 2 receptors?
Epi and dopamine.
152
Which NT's are responsible for the messenger pathway of alpha 2 receptors?
NE and dopamine.
153
Which NT's are responsible for the messenger pathway of alpha 1 receptors?
NE.
154
What determines the outcome of a messenger pathway?
The type of enzyme and receptor present on the membrane.
155
What is the metabolism of epinephrine accomplished by?
Mainly by the liver and kidneys; it is rapid (2 minutes for NE, less for epi).
156
The time spent before the NE activity wanes is very transient due to what factors?
- Enzymatic degradation
- Reuptake.
157
What does enzymatic degradation lead to if in excess and how is it treated?
Depression; treated with increased levels of dopamine, serotonin, and epinephrine by eliminating the enzymes (MAO/COMT inhibitors).
158
What are the two enzymes responsible for the degradation of epinephrine and are they intracellular or extracellular?
Monoamine oxidase (MAO) is intracellular
Catecholamine-o-methyltransferase (COMT) is extracellular.
159
Which reuptake route does norepinephrine use predominantly?
More of reuptake 1 (neuronal amine-uptake system).
160
Which reuptake system does epinephrine use predominantly?
More of reuptake 2 (extraneuronal reuptake pathway).
161
What are cranial nerves?
Cranial nerves are nerves that emerge directly from the brain (including the brain stem).
162
What are spinal nerves?
Spinal nerves are nerves that emerge from the segments of the spinal cord.
163
How are cranial nerves numbered?
Cranial nerves are numbered based on the order in which they emerge from the brain from rostral to caudal.
164
Which cranial nerves emerge from the cerebrum/forebrain?
The olfactory and optic nerves emerge from the cerebrum/forebrain.
165
Which cranial nerves emerge from the brain stem?
All cranial nerves except for the olfactory and optic emerge from the brain stem.
166
Which parts of the head region receive sympathetic innervation, and from where?
The eyes and salivary glands receive sympathetic innervation from the thoracic region as the sympathetic nerves ascend via the sympathetic chain.
167
What are the regions of the grey matter of the spinal cord?
Grey matter is made up of the dorsal, lateral, and ventral column as well as the intermediolateral horn.
168
How do reflexes work?
Reflexes are controlled by the brain stem alone from the neck to the tail; the first synapse in the ascending pathway of the CNS occurs via the afferent fiber in the dorsal column of the grey matter and forms an interneuron, which supplies the same organ via the efferent fiber.
169
Reflexes show the integrity of the ___________________?
Reflexes show the integrity of the spinal cord.
170
What is decussation?
Decussation is the crossing over of the sensory fiber from one side of the grey matter of the spinal cord to the other that sometimes occurs before the ascending pathway.
171
Describe the ascending pathway.
Sensory fibers enter the spinal cord, synapse at the dorsal column, may or may not decussate, and ascend to the brain to deliver sensory information from the hindbrain to the midbrain, terminating in the cerebral cortex of the forebrain.
172
What are the two halves of the cerebral cortex?
The two halves of the cerebral cortex are the sensory part and the motor part.
173
What happens after the ascending fiber terminates in the sensory part of the cerebral cortex?
The descending pathway takes over as the motor fiber moves back down the CNS to the ventral horn of the grey matter of the spinal cord to synapse and send out the preganglionic nerve fiber.
174
What is the first cranial nerve and what is it responsible for?
The first cranial nerve is the olfactory nerve, which is responsible for smell.
175
What is the 2nd cranial nerve and what is it responsible for?
The 2nd cranial nerve is the optic nerve, which is responsible for vision.
176
What is the 3rd cranial nerve and what is it responsible for?
The 3rd cranial nerve is the oculomotor nerve, responsible for 4 extrinsic eye muscles, levator palpebrae superioris, and pupillary sphincter muscle.
177
What is the 4th cranial nerve and what is it responsible for?
The 4th cranial nerve is the trochlear nerve, responsible for the superior oblique muscle.
178
What is the 5th cranial nerve and what is it responsible for?
The 5th cranial nerve is the trigeminal nerve, made up of maxillary, mandibular, and ophthalmic parts.
## Footnote
- Maxillary: cheeks, lower eyelid, nasal mucosa, upper lip, upper teeth, and palate.
- Mandibular: anterior 2/3 of tongue, skin over mandible and lower teeth, muscles of mastication.
- Ophthalmic: scalp, forehead, and nose.
179
What is the 6th cranial nerve and what is it responsible for?
The 6th cranial nerve is the abducens nerve, responsible for the lateral rectus muscle.
180
What is the 7th cranial nerve and what is it responsible for?
The 7th cranial nerve is the facial nerve, responsible for sensation to part of the external ear, taste from anterior 2/3 tongue, hard and soft palate, muscles of facial expression, lacrimal, submandibular, sublingual glands, and mucous glands of mouth and nose.
181
What is the 8th cranial nerve and what is it responsible for?
The 8th cranial nerve is the vestibulocochlear nerve, responsible for hearing and balance.
182
What is the 9th cranial nerve and what is it responsible for?
The 9th cranial nerve is the glossopharyngeal nerve, responsible for posterior 1/3 tongue, external ear, middle ear cavity, carotid body and sinus, taste from posterior 1/3 tongue, parotid gland, and stylopharyngeus.
183
What is the 10th cranial nerve and what is it responsible for?
The 10th cranial nerve is the vagus nerve, responsible for external ear, larynx and pharynx, thoracic and abdominal viscera, taste from epiglottis region of tongue, smooth muscles of pharynx, larynx, and most of GIT, and most muscles of the larynx and pharynx.
184
What is the 11th cranial nerve and what is it responsible for?
The 11th cranial nerve is the accessory nerve, responsible for trapezius and sternocleidomastoid, with a few fibers running with the vagus nerve to the viscera.
185
What is the 12th cranial nerve and what is it responsible for?
The 12th cranial nerve is the hypoglossal nerve, responsible for intrinsic and extrinsic tongue muscles (except for the palatoglossus).
186
How are the spinal nerves arranged?
Spinal nerves are arranged as follows:
- 8 pairs of cervical nerves (C1-C7)
- 13 pairs of thoracic nerves (T1-T13)
- 7 pairs of lumbar nerves (L1-L7)
- 3 pairs of sacral nerves (S1-S3)
- 20-23 pairs of coccygeal nerves (Co1-Co23).
187
How are spinal nerves named?
Spinal nerves are named similarly to the structures they innervate.
188
Where is the 8th cervical spinal nerve if there are only 7 cervical vertebrae?
The 8th cervical spinal nerve is located between C7 and T1.
189
What is the somatic system?
The somatic system is the part of the PNS associated with skeletal muscle voluntary control of body movements; it consists of somatic sensory (afferent) and somatic motor (efferent).
190
What is the first point of contact for somatosensory nerves in the CNS?
The first point of contact for somatosensory nerves in the CNS is the dorsal column of the grey matter of the spinal cord.
191
Where do the axons of somatic sensory nerves go for reflex connections?
The axons of somatic sensory nerves go to the ventral horn of the grey matter of the spinal cord for reflex connections.
192
Where do the axons of somatic sensory nerves go for non-reflex connections?
The axons of somatic sensory nerves go to the white matter (to ascend and/or descend) and form intersegmental tracts with other segments of the spinal cord.
193
What are the different regions of the dorsal horn of the grey matter of the spinal cord?
- Nucleus posteromarginalis
- Substantia gelatinosa
- The nucleus proprius
- Nucleus dorsalis (dorsal nucleus of Clark)
194
What are the 4 main ascending fiber tracts?
- Fasciculus gracilis and fasciculus cuneatus
- Ventral and lateral spinothalamic tracts
- Spinotectal tract
- Dorsal and ventral spinocerebellar tract.
195
What are the 3 more minor ascending fiber tracts?
- Spinoreticular tract
- Spino-olivary tract
- Spinocervical tract.
196
Where does the fasciculus gracilis and fasciculus cuneatus ascending tract run from and what does it control?
The fasciculus gracilis runs from the hindlimbs and carries sensory information from the lower half of the body. The fasciculus cuneatus runs from the forelimbs and transmits vibration, conscious proprioception, and fine touch sensations from the upper body (forelimbs, trunk, and neck).
197
Which of the ascending tracts has the strongest reflex pathway?
The fasciculus gracilis and fasciculus cuneatus have the strongest reflex pathway.
198
Where does the lateral and ventral spinothalamic ascending tract run from and what does it control?
The lateral and ventral spinothalamic ascending tract runs from the spinal cord to the thalamus of the brain. The ventral tract transmits information related to crude touch and form pressure, while the lateral tract transmits pain and temperature sensations.
199
Where does the spinotectal ascending tract run from and what does it control?
The spinotectal ascending tract runs from the spinal cord to the tectum of the brain, inhibiting pain sensation by terminating at the periaqueductal gray.
200
Where does the dorsal and ventral spinocerebellar ascending tract run from and what does it control?
The dorsal and ventral spinocerebellar ascending tract runs from the spinal cord to the cerebellum. The dorsal tract carries unconscious proprioceptive information from the skeletal muscle and joints to the cerebellum, while the ventral tract carries proprioceptive information from the body to the cerebellum.
201
Where does the spinoreticular ascending tract run from and what does it control?
The spinoreticular ascending tract runs from the spinal cord to the pons and medulla, responsible for automatic responses to pain caused by an injury.
202
Where does the spino-olivary ascending tract run from and what does it control?
The spino-olivary ascending tract runs from the spinal cord to the olivary nucleus of the brain, responsible for the control of movements of the body and limbs and carries proprioception information from muscles and tendons as well as cutaneous impulses to the olivary bodies.
203
Where does the spinocervical ascending tract run from and what does it control?
The spinocervical ascending tract runs from the spinal cord to the cervical area of the brain, providing a pathway for the transmission of tactile and pressure sensation from the cutaneous surfaces to the cerebrum.
204
Where are the nuclei for the motor system of the somatic nervous system within the spinal cord?
The nuclei for the motor system of the somatic nervous system are located in the grey matter of the spinal cord at the ventral horn (skeletal muscle) or the intermediolateral cell column (visceral).
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What is the function of the motor systems in the grey matter?
The function of the motor systems in the grey matter is to control somatic and visceral motor activities.
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What are the two nuclear groups of the ventral horn of the grey matter?
- Medial: extends throughout the length of the cord and innervates the muscles of the axial skeleton.
- Lateral: innervates the remainder of the somatic musculature.
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What are the two neurons contained within the somatic motor columns?
- Large alpha cells in the extrafusal muscle fibers.
- Gamma cells in the muscle spindles.
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What is the role of the efferent motor system?
The role of the efferent motor system is to conduct impulses from the CNS and PNS to the muscles, organs, and glands affecting what happens in those tissues.
209
The somatic division of the nervous system contains nerves which end in the ____________________?
The somatic division of the nervous system contains nerves which end in the skeletal muscles.
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Where does the descending pathway start and end?
The descending pathway starts in the brain and ends in the spinal cord.
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Are synapses involved in the descending pathway?
No, synapses are not involved in the descending pathway.
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What is an upper motor neuron?
An upper motor neuron is a neuron in the region of the brain to spinal cord.
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What is a lower motor neuron?
Neurons in the region of the spinal cord to target tissue.
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What is UMN disease?
UMN damage that affects the target tissue.
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What is LMN disease?
LMN damage that affects the target tissue.
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How come a skin reflex test would still be positive in the case of LMN disease?
Because the spinal cord is unaffected in the case of LMN disease.
217
What are the two functional divisions of the descending motor tracts?
- Pyramidal
- Extrapyramidal
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What are pyramidal tracts and what are they responsible for?
- Tracts that originate in the cerebral cortex, carrying motor fibers to the spinal cord and brainstem.
- Responsible for the voluntary control of the musculature of the body and face.
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What are extrapyramidal tracts and what are they responsible for?
- Originate in the brain stem, carrying motor fibers to the spinal cord; bypasses the brain pyramids.
- Responsible for involuntary and automatic control of all musculature such as muscle tone, balance, posture, and locomotion.
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What are the 5 descending motor pathways?
- Corticospinal tracts
- Rubrospinal tract
- Vestibulospinal tract
- Tectospinal tract
- Reticulospinal tract
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Describe the corticospinal descending tract.
- Originate in the primary motor and premotor areas of the cerebral cortex and goes to the spinal cord.
- Functions in the programming and execution of voluntary muscles.
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Describe the rubrospinal descending tract.
- Originate from red nucleus and functions to adjust the distal movements of the limbs (precise control of the digits in non-primate mammals).
- Damage will cause all limbs to be extended and rigid.
- Responsible for large muscle movement regulation flexor and inhibiting extensor tone as well as fine motor control.
223
Describe the vestibulospinal descending tract.
- The lateral vestibulospinal tract originates from cells in the lateral vestibular nucleus of the upper medulla portion of the brainstem.
- Responsible for maintaining balance via lateral and medial muscles of the eye, muscles of the neck, trunk, limbs, etc.
- Terminates at the medial motor neurons innervating postural group muscles.
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What is the function of the vestibulospinal descending tract?
Excites extensor motor neurons and inhibits flexor motor neurons on the ipsilateral side; makes automatic postural adjustment of the axial and proximal antigravity muscles necessary for equilibrium.
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Describe the sensory input received by the vestibular nuclei for the vestibulospinal descending tract.
Each vestibular nucleus receives information from the ipsilateral vestibular apparatus of the inner ear via afferent fiber of the vestibulocochlear nerve.
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What does ipsilateral mean?
Impulses coming from the right ear control the muscles on the right side of the body, and damage to one side of the head can cause loss of balance on that side.
227
Describe the tectospinal descending tract.
- Originates in the rostral colliculus, decussates and descends to upper cervical level of the spinal cord.
- Mediates automatic orientation of the head and eyes to make sure the head can orient to see what is in front of it.
- More important in herbivores than carnivores as it provides a protective mechanism.
228
Describe the reticulospinal descending tract.
- Runs from pons and medulla to the spinal cord.
- Those from pons excite medial extensor motor neurons while those from the medulla inhibit motor extensor neurons.
- Standing: pons
- Lying down with limbs flexed: medulla.
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In what region of the spinal cord are ascending and descending tracts able to be seen most?
White matter.
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Describe the path of a descending tract as it leaves the brain.
Brain → white matter of cervical region → descend the spinal cord → enter the grey matter → synapse at the ventral horn of the segment near the muscle it wants to innervate.
231
Describe the difference in the path of a pyramidal vs an extrapyramidal tract.
Pyramidal: Cortex → midbrain → pons → rostral medulla → spinal cord → muscle.
Extrapyramidal: Cortex → midbrain → pons → rostral medulla → caudal medulla → spinal cord → muscle.
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What is the somatic motor system made up of?
Lower motor neurons and upper motor neurons.
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What do LMNs govern?
Posture and locomotion.
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If the LMN is not intact, what happens to the structure it innervates?
It becomes completely disconnected from the nervous system.
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Where are the neurons of UMNs?
Higher centers of the brain.
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Where do the axons of UMNs terminate?
Either within the brainstem cell bodies or cell bodies within the spinal cord.
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Descending UMN pathways tend to activate what structures?
Coactivate alpha and gamma motor neurons and have control over LMNs.
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Describe what you will see with UMN damage.
- Inappropriate movement
- No muscle atrophy
- Retained but exaggerated segmental reflex
- Normal electromyogram
- Spastic paralysis (spasm is present)
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Describe what you will see with LMN damage.
- Paralysis or paresis (flaccid)
- Muscle atrophy
- Loss of segmental and intersegmental reflexes
- Loss of electromyogram recording
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What are the 4 main spinal cord regions associated with the localization of lesions?
- C1-C5
- C6-T2: brachial intumescences containing motor neurons to the thoracic limbs
- T3-L3
- L4-S3: lumbar intumescences containing motor neurons to the hind/pelvic limbs
241
Tetraplegia indicates lesions within the _____________ spinal cord segments.
C1-T2.
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Paraplegia indicates lesions within the _____________ spinal cord segments.
T3-S3.
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What happens if there is a lesion in the C1-C5 or the T3-L3 spinal cord segments?
- Motor neurons of the brachial and lumbar intumescences are spared and spinal reflexes mediated by these spared motor neurons remain intact and the muscle tone is usually normal to increase.
- In this instance tetraplegia and paraplegia associated with preserved spinal reflexes is caused by UMN lesion.
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Is detecting the presence of a UMN lesion when there is already a LMN lesion present harder or easier?
Harder; LMN lesion causes paralysis of the limb muscles and loss of spinal reflexes, therefore making detection of a UMN lesion challenging.
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What test is used to try to detect UMN damage in the presence of an LMN lesion?
CTMR (Panniculus reflex).
246
What happens if there is a lesion in the C6-T2 or the L4-S3 spinal cord segments?
- Motor neurons in these regions are damaged, spinal reflexes become reduced or absent, and the muscle tone is often reduced.
- In this instance, the tetraplegia and paraplegia associated with reduced or absent spinal reflexes is caused by an LMN lesion.
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What are the UMN types that form the descending pathway?
- Cerebral cortex MN
- Cerebellum MN
- Basal ganglia and brainstem nuclei MN
248
What are the two major UMN sites that control locomotion?
Basal ganglia and cerebellum.
249
Where are the cell bodies and dendrites of LMNs located?
CNS.
250
What are the two types of LMNs?
Gamma (intrafusal) and alpha (extrafusal).
251
What is the origin of LMNs?
Either cranial nerve nuclei of the brainstem or ventral horn of the spinal cord.
252
What serve as the last motor fibers of the motor system?
LMNs.
253
What is vestibular dysfunction?
Abnormalities in posture and eye movement that results from dysfunction of one inner ear that involves a lesion in the cerebellum and the vestibular system.
254
What are the symptoms associated with vestibular dysfunction?
The animal typically exhibits a head tilt toward the affected side, and abnormal spontaneous horizontal nystagmus (with fast phase away from lesion), and postural evidence of disequilibrium by falling towards the side of the lesion.
255
What is herniated IVDD?
- Involves compressive lesions of the spinal cord.
- Characterized by an interruption of the more discreetly (not diffused) organized descending pathways (corticospinal, rubrospinal, reticulospinal, and vestibulospinal tracts) and ascending pathways (spinocerebellar, dorsal column).
256
What are the symptoms of herniated IVDD?
Ataxic gait, uncoordinated limb movement, a swaying of the body, and stumbling over obstacles. Total paralysis may occur if the more diffused pathways are involved following severe spinal compression.
257
What is equine nigropallidal encephalomalacia?
A degenerative disease of basal ganglia. This appears like Parkinson's disease in man. It occurs in horses that consume a specific plant called yellow star thistle found mostly in California and Oregon; signs of intoxication appear weeks after grazing on these plants.
258
What are the signs of Equine nigropallidal encephalomalacia?
Marked hypertonia with rigidity of the facial muscles (especially the muzzle), retraction of the lips and nose, protrusion of the tongue, and inability to prehend food. Continued purposeless chewing movements occur.
259
What are the clinical signs of cerebellar disease?
- Head tremors
- Intention tremor (tremor associated with voluntary movement)
- Vestibular dysfunction
- Opisthotonus (spasm with upward bending of head and tail)
- Extensor hypertonus of the forelimbs
- Clonic movements of the pelvic limbs
- Mental attitude (perception) and the ability to initiate motor activity are not altered with cerebellar disease.
260
What is a myotome and dermatome?
Muscles that one particular spinal root supplies are that nerve's myotome and the dermatome are the areas of sensory innervation on the skin for each spinal nerve.
261
What is sciatica generally caused by?
The compression of lumbar nerves L4, or L5, or sacral nerves S1-S3, or by the compression of the sciatic nerve itself.
262
What is horner's syndrome?
Relatively rare disorder characterized by a constricted pupil (miosis), drooping of the upper eyelid (ptosis), absence of sweating of the face (anhidrosis), and sinking of the eyeball into the bony cavity that protects the eye (enophthalmos).
263
What are the causes of horner's syndrome?
Trauma to the brachial plexus (lesion of the sympathetic preganglionic neurons) or lesion of the primary neuron to the eye muscles.
264
What is facial nerve paralysis?
Involves paralysis of any structures innervated by the facial nerve and results in unilateral facial weakness, loss of taste, hyperacusis, and decreased salivation and tear secretion.
265
What happens in the case of glossopharyngeal nerve dysfunction?
Dysphagia and regurgitation.
266
Describe the efferent, afferent, and autonomic innervation of the glossopharyngeal nerve.
- Efferent (motor) to striated pharyngeal muscles
- Autonomic: smooth pharyngeal muscles and parasympathetic to some salivary glands
- Afferent (sensory): back of tongue, chemo and baroreceptors (thorax)
267
What do disorders of the hypoglossal nerve cause?
Weakness or wasting of the tongue on the affected side; tongue will always stick out.
268
What do pathologies of the midbrain cause?
Coma, semicoma (RAS), extensor rigidity (red nucleus).
269
What is head pressing?
Condition characterized by the compulsive act of pressing the head against a wall or other object for no reason due to massive degeneration of the brainstem that results in confusion and the animal seems blind.
270
What is head pressing indicative of generally?
Damage to the nervous system, which may result from a number of causes, including prosencephalon disease (in which the forebrain and thalamus parts of the brain are damaged), and some types of toxic poisoning.
271
What are possible causes of head pressing?
Possible causes may be a metabolic disorder, such as hyper- or hyponatremia.
272
What are epileptic seizures caused by?
These seizures can be caused by trauma, toxins, brain tumors, and infections.
273
What is the function of the forebrain as a whole?
Regulation of perception, voluntary motor control, emotion cognition, and language.
274
What is the function of the basal ganglia?
Control of higher voluntary motor activity such as skeletal motor control.
275
What is the function of the thalamus?
Involved in integrating and relay of sensory signals, as well as motor control and regulation of cortex excitation.
276
What is the function of the subthalamus?
Regulator of motor activity.
277
What is the function of the hypothalamus?
Control center for sex drive, pleasure, pain, hunger, thirst, blood pressure, body temperature, and produces oxytocin and ADH which are stored and released by the posterior pituitary.
278
What is the function of the pineal body of the epithalamus?
Endocrine organ responsible for the secretion of melatonin.
279
What is the function of the habenula of the epithalamus?
Olfactory correlation center.
280
What is the function of the posterior pituitary?
Endocrine organ responsible for oxytocin and ADH storage and release.
281
What is the function of the striatum?
Decision-making functions, such as motor control, emotion, habit formation, and reward.
282
What is the function of the hippocampus?
Long term memory formation and memory retrieval.
283
What is the function of the limbic system?
Integration and expression of emotions, feelings, and drives.
284
What is the function of the frontal lobe of the cerebrum?
Motor function including those for language, learning, planning, and higher psychological processes; responsible for elaboration of conscious thought.
285
What is the function of the occipital lobe of the cerebrum?
Visual operations.
286
What is the function of the parietal lobe of the cerebrum?
Somatosensory functions (temperature, touch, pressure, and pain), cognitive and intellectual processes.
287
What is the function of the temporal lobe of the cerebrum?
Hearing and speech, sense of smell, memory processes, and functions related to the limbic system.
288
What is the overall function of the midbrain?
Regulation of walking and posture, and reflex for the head and eye movements.
289
What is the function of the anterior and posterior canalliculi?
Anterior: visual reflex center
Posterior: auditory reflex center.
290
What is the function of the medulla?
Functions in the respiratory, cardiovascular, and digestive systems.
291
What is the function of the pons?
Respiratory inhibitory centers and structures involved in motor control.
292
What is the function of the cerebellum?
Movement coordination including balance/posture, starting and stopping of movements, and smooth movements.
293
In what areas are the afferent fibers of the cerebellum located?
Vestibulocerebellum, spinocerebellum, and corticocerebellum.
294
What is the function of reticular formation in the pons and medulla?
Involved in sleep and generalized control of excitation of higher forebrain structures.
