sp14_-_human_anatomy_exam_1_20141210195148 Flashcards
What is the bony structure surrounding the brain?
skull
What is the bony structure surrounding the spinal cord?
vertebral canal
How many angular degrees separate the horizontal plane from the coronal plane?
90 degrees
What type of muscle is innervated by fibers of the somatic nervous system?
striated muscle
What are the 3 major embryological subdivisions of the brain?
- rhombencephalon - most caudal subdivision and consists of: myelencephalon (medulla oblongata) and metencephalon (pons and cerebellum)- mesencephalon - midbrain- prosencephalon - cerebrum including diencephalon (“in-between” brain) and telencephalon (cerebral hemispheres and corpus striatum of the basal ganglia)
What are the minor subdivisions of the hindbrain?
- myelencephalon - medulla oblongata- metencephalon - pons and cerebellum
What are the minor subdivisions of the forebrain?
- diencephalon - “in-between brain”- telencephalon - cerebral hemispheres, corpus striatum of the basal ganglia
What are the ventricular cavities of each subdivision of the brain?
- spinal cord - central canal- rhombencephalon - 4th ventricle- midbrain - cerebral aqueduct- diencephalon - 3rd ventricle- telencephalon - lateral ventricles (1st and 2nd)
What is the structural and functional unit of the nervous system?
neuron
List the 12 cranial nerves by name and number.
CN I - olfactoryCN II - opticCN III - oculomotorCN IV - trochlearCN V - trigeminal (ophthalmic, maxillary, and mandibular)CN VI - abducensCN VII - facialCN VIII - vestibulocochlearCN IX - glossopharyngealCN X - vagusCN XI - accessoryCN XII - hypoglossal
What are the components of the brainstem?
- midbrain- pons- medulla
Name the lobes of the cortex.
- frontal lobe- occipital lobe- temporal lobe- parietal lobe
What are the borders of the frontal lobe?
lobe lies rostral to the central sulcus and superior to the lateral fissure
What are the borders of the occipital lobe?
lobe lies behind an imaginary line drawn from the parieto-occipital sulcus to the preoccipital notch
What are the borders of the temporal lobe?
lobe lies below the lateral fissure and an imaginary extension drawn caudally to the occipital lobe
What are the borders of the parietal lobe?
lobe occupies the remainder of the lateral surface not covered by another lobe
Define ipsilateral.
the axon (tract) courses and/or terminates on the same side as its cell body (nucleus)
Define contralateral.
the axon (tract) courses and/or terminates on the side opposite its cell body (nucleus)
Define bilateral.
the axon (tract) divides and courses and/or terminates on both sides
Define decussation.
fibers ascend/descend as they cross
Define commissure.
fibers pass directly from one side to the other
List the 3 meninges.
- dura mater- arachnoid- pia mater
List and describe the 2 clinically significant potential meningeal spaces.
- epidural space - potential space between the skull and dura mater- subdural space - potential space between the dura mater and the arachnoid**subarachnoid space is an actual space, not a potential space (?)
What is an epidural hematoma?
result of blood entering the epidural space; often the result of damage to the middle meningeal artery; the expanding hematoma puts pressure on the brain
What is a subdural hematoma?
result of blood entering the subdural space; often the result of damage to small veins that cross from the brain to the venous sinuses; the expanding hematoma puts pressure on the brain
What is the major blood supply to the dura over the parietal lobe?
the middle meningeal artery and its branches (?)
What is the rostral extent of the subarachnoid space along the optic nerve? How is this clinically significant?
meninges cover the optic nerve so the subarachnoid space extends along the optic nerve to the back of the eye; an abnormal increase in CSF pressure (hydrocephalus) is reflected by changes in the optic papilla (choked disk; papilledema)
What is the falx cerebri and what does it separate?
- it is a reflection of dura mater- extends ventrally in the sagittal plane from the skull to the corpus callosum and separates the cerebral hemispheres; the superior sagittal sinus occupies the upper edge of the falx
What is the tentorium cerebelli and what does it separate?
- it is a reflection of dura mater- lies horizontally to separate the cerebellum below from the occipital lobe above; tentorium extends around the brainstem; the opening created by the brainstem is called the tentorial incisure (notch) and is occupied by the midbrain
What occupies the supratentorial compartment? The infratentorial compartment?
- supratentorial compartment - cerebrum- infratentorial compartment - cerebellum
What is the origin, course, and point of resorption of cerebrospinal fluid?
- cerebrospinal fluid (CSF) is produced by vascular tufts located in the lateral, third, and fourth ventricles- CSF exits the ventricular system into the subarachnoid space- CSF is reabsorbed into the superior sagittal siinus through the arachnoid granulations
Name the vessels involved in the posterior (vertebral-basilar) blood supply of the brain.
- posterior inferior cerebellar artery- anterior inferior cerebellar artery- superior cerebellar artery- posterior cerebral artery
Name the vessels involved in the anterior (internal carotid) blood supply of the brain.
- anterior cerebral artery (with the anterior communicating artery)- middle cerebral artery (with ophthalmic artery)- posterior communicating artery (connects ICA with posterior cerebral artery)
Name the vessels of the cerebral arterial circle (of Willis).
- anterior cerebral artery- anterior communicating artery- middle cerebral artery- internal carotid artery- posterior communicating artery- posterior cerebral artery- superior cerebellar artery- basilar artery- anterior inferior cerebellar artery- posterior inferior cerebellar artery- vertebral artery- anterior spinal artery
Name the 3 major vessels that supply the cerebral cortex.
- anterior cerebral artery- middle cerebral artery- posterior cerebral artery
Name each of the four functional components found in a peripheral nerve and describe their functions.
- somatic afferent - pain, touch, temperature, and position sense- somatic efferent - motor signals that control striated muscles- visceral afferent - “visceral sensibility” like peristaltic activity, blood pressure, bladder fullness, etc.- visceral efferent - autonomic nervous system; two neurons linked together
What tissues are innervated by somatic afferent neurons?
skin (pain, touch, temperature, conscious proprioception, awareness of limb position)
What tissues are innervated by somatic efferent neurons?
striated (voluntary) muscles
What tissues are innervated by visceral efferent neurons?
contraction of smooth muscle and secretion of glands; preganglionic and postganglionic neuron chains
What tissues are innervated by visceral afferent neurons?
organs to monitor internal environment like heart rate, blood pressure, smooth muscle contractility, and bladder/bowel fullness
What is the location of the preganglionic nerve cell bodies? The postganglionic nerve cell bodies?
- preganglionic - nerve cell body in CNS; axon extends to autonomic ganglion- postganglionic - nerve cell body in autonomic ganglion; axon extends to visceral target
What are the functional components and target tissue of nerve fibers found in the posterior root?
- functional component - sensory (somatic afferent and visceral afferent)- target tissue - skin, internal organs
What are the functional components and target tissue of nerve fibers found in the anterior root?
- functional component - motor (somatic efferent)- target tissue - striated muscle, internal organs
What is the functional component and target tissue of nerve fibers found in the posterior ramus?
- functional component - sensory and motor- target tissue - back
What is the functional component and target tissue of nerve fibers found in the anterior ramus?
- functional component - sensory and motor- target tissue - anterior and lateral body as well as limbs
What is the function and relative speed of an A-alpha afferent nerve fiber?
- function - myotatic reflex- velocity - 70-120 m/sec
What is the function and relative speed of an A-beta nerve fiber?
- function - deep touch- velocity - 60-80 m/sec
What is the function and relative speed of an A-delta nerve fiber?
- function - light touch, fast pain- velocity - 10-30 m/sec
What is the function and relative speed of a C nerve fiber?
- function - slow pain- velocity - 0.5-2.5 m/sec
List the events seen during the degeneration of a nerve fiber.
- if an axon is crushed (or cut), the axon distal to the crush will degenerate- the axon proximal to the crush will die back a short distance- the cell body will respond by becoming more metabolically active (chromatolysis)- the axon and myelin degenerate (but not Schwann cells) and macrophage cells engulf the debris
List the events seen during the regeneration of a nerve fiber.
- axons sprout and exhibit growth cones- Schwann cells undergo mitosis and form guiding route for the growth cone- Schwann cells produce new myelin- greater number of Schwann cells means: shorter internodal distance and slower conduction time
What is the “knee jerk” reflex? How does it work? How is it modified?
- when the muscle is stretched (by hitting the knee), the neuromuscular spindle is also stretched- A-alpha sensory fiber conducts stretch signal back to spinal cord- sensory fiber has a single synapse with an alpha motor neuron which moves the extrafusal muscle fibers to move the limb- this is monosynaptic and cannot be modified
What is the lower motor neuron?
the nerve cell body (located in the CNS) and its axon (located in the PNS) that innervates a striated muscle
What are the signs and symptoms of a lower motor neuron lesion?
- flaccid paralysis- atonia - loss of normal muscle tone- areflexia - loss of the stretch (myotatic) reflex- fasciculations - spontaneous contraction of bundles of muscle fibers- muscle atrophy
A lower motor neuron lesion results form a lesion of what?
- peripheral nerve- anterior root- anterior horn motor neurons
What is muscle tone?
slight contraction of the muscles that does not produce movement or active resistance, but gives the muscles firmness, assisting the stability of joints and the maintenance of posture
What is the neuroanatomical basis of muscle tone?
the activation of the gamma and alpha motor neurons
What are the functional components and target tissue of nerve fibers found in the anterior root?
- functional component - motor (somatic efferent)- target tissue - striated muscle, internal organs
Name the 3 funiculi of the spinal cord.
- posterior funiculus- lateral funiculus- anterior funiculus
Name the four sulci.
- posterior median sulcus- posterior intermediate sulcus- posterolateral sulcus- anterolateral sulcus
What is the caudal extent of the posterior intermediate sulcus?
posterior intermediate sulcus only extends to level T6 so that is the caudal extent
What 2 bundles of fibers are separated by the posterior intermediate sulcus?
- fasciculus gracilis- fasciculus cuneatus
Name the cord levels between which the lateral horn is found.
T1-L2
Name the two structures that stabilize the spinal cord within the vertebral canal.
- denticulate ligaments - extend from the cord through the arachnoid to the dura- spinal nerves - anchor the cord in the vertebral canal
Name the sensory function modulated by Lamina II.
pain (substantia gelatinosa)
In what direction are the impulses traveling that are found in the posterior root? In the anterior root? In the spinal nerve?
- posterior root - carries sensory signals toward the cord- anterior root - carries motor signals away from the cord- spinal nerve - carries signals toward and away from the cord
What is the posterior root ganglion?
found along the posterior root; contains the neuron cell bodies of the nerve fibers that make up the posterior root
What part of the body (soma) is served by the nerve fibers that make up the posterior ramus? The anterior ramus?
- posterior ramus - serves posterior aspect of the body- anterior ramus - serves anterior aspect of the body
Are the anterior and posterior rami sensory in function? Motor in function?
The anterior and posterior rami are both sensory and motor in function since they carry fibers from the posterior and anterior roots.
Why are the communicating rami described in terms of colors (gray and white)? What function do these rami serve?
- gray matter is made up of neuron cell bodies- white matter is made up of myelinated axons- the gray and white communicating rami contain autonomic fibers and branch off the spinal nerve at T1-L2
Name the nerve fibers that make up the cauda equina.
posterior and anterior roots; occupies the lumbar cistern
Name the vertebral level that marks the caudal extent of the conus medullaris.
the caudal cone-shaped end of the spinal cord; extends to the L1-L2 interspace
Name the tissue that makes up the denticulate ligaments.
pia and arachnoid
Name the tissue that makes up the filum terminale.
pia and arachnoid that extend from the conus medullaris which is eventually encased in dura
What is contained within the lumbar cistern?
cauda equina and cerebrospinal fluid, along with the filum terminale
Name the embryological origin of the nucleus pulposus and the clinical significance of this structure.
- nucleus pulposus is a remnant of the notochord- nucleus herniates through the break in the annulus fibrosus and puts pressure on nearby nerve fibers
a, b
a. nucleus gracilis b. nucelus cuneatus
c, d
c. trigeminal spinal nucleus d. gracilis tract
e, f
e. cuneate tract f. trigeminal spinal tract
g, h
g. medial lemniscus h. pyramidal tract
a, b
a. cuneate nucleus b. trigeminal spinal nucleus
c, d
c. solitary nucleus d. dorsal motor nucleus of the vagus
e, f
e. hypoglossal nucleus f. cuneate tract
g, h
g. trigeminal spinal tract h. solitary tract
i, j
i. medial lemniscus j. pyramidal tract
a, b
a. vestibular nuclear complex b. cochlear nucleus
c, d
c. solitary nucleus d. inferior olive
e, f
e. trigeminal spinal tract f. solitary tract
g, h
g. medial lemniscus h. pyramidal tract
i, j
i. medial longitudinal fasciculus j. inferior cerebellar peduncle
a, b
a. abducens nucleus b. facial nucleus
c, d
c. inferior olive d. inferior cerebellar peduncle
e, f
e. middle cerebellar peduncle f. superior cerebellar peduncle
g, h
g. medial lemniscus h. pyramidal tract
i, j
i. medial longitudinal fasciculus j. fourth ventricle
a, b
a. trigeminal motor nucleus b. trigeminal principal sensory nucleus
c, d
c. trigeminal mesencephalic nucleus d. medial lemniscus
e, f
e. medial longitudinal fasciculus f. middle cerebellar peduncle
g, h
g. pyramidal tract h. superior cerebellar peduncle
i, j
i. trigeminal mesencephalic tract j. trigeminal nerve root
k, m
k. basilar pons m. fourth ventricle
a, b
a. periaqueductal gray b. inferior colliculus
c, d
c. superior cerebellar peduncle d. medial longitudinal fasciculus
e, f
e. medial lemniscus f. lateral lemniscus
g, h
g. basilar pons h. cerebral aqueduct
a, b
a. periaqueductal gray b. superior colliculus
c, d
c. oculomotor nuclear complex d. superior cerebellar peduncle
e, f
e. medial longitudinal fasciculus f. medial lemniscus
g
g. cerebral aqueduct
What pathway is shown? What type of nerve fiber is shown at the bottom?
- discrimative touch pathway - A-beta fibers
What pathway is shown? What type of nerve fiber is shown at the bottom?
- fast pain pathway - A-delta fibers
What pathway is shown? What type of nerve fiber is shown at the bottom?
- slow pain pathway - C fibers
What pathway is this? Starting from the top, name all of the structures that the nerve passes through.
- Pain Regulation Pathway - periaqueductal gray - nucleus raphe magnus (medulla) - raphe spinal tract (serotonin) - lamina II
What pathway is shown? What nerve fiber is shown in blue? What nerve fiber is shown in green? What type of synapse is shown?
- myotatic (stretch) reflex - A-alpha sensory fiber - alpha motor neuron - monosynaptic synapse
For the autonomic system, name the general components shown at 1 and 2.
- preganglionic neuron 2. postganglionic neuron
Name the components of the SYMPATHETIC division of the ANS. (For 2 and 4, name the neurotransmitters released here)
- preganglionic neuron 2. acetylcholine 3. postganglionic neuron 4. norepinephrine
Name the components of the PARASYMPATHETIC division of the ANS. (For 2 and 4, name the neurotransmitters released here)
- preganglionic neuron 2. acetylcholine 3. postganglionic neuron 4. acetylcholine
For CN III (oculomotor), name the preganglionic nucleus and its location (1), the ganglion (2), and what it innervates (3).
- Edinger-Westphal nucleus in the midbrain 2. ciliary ganglion 3. pupilary constrictor muscle and ciliary muscle
For CN VII (facial), name the preganglionic nucleus and its location (1), the ganglion (2 and 3), and what it innervates (4 and 5).
- superior salivatory nucleus in the pons 2. pterygopalatine ganglion 3. submandibular ganglion 4. lacrimal gland 5. submandibular and sublingual gland
For CN IX (glossopharyngeal), name the preganglionic nucleus and its location (1), the ganglion (2), and what it innervates (3).
- inferior salivatory nucleus in the medulla 2. otic ganglion 3. parotid salivary gland
For CN X (vagus), name the preganglionic nucleus and its location (1), the location of the ganglion (2), and what it innervates (3 and 4).
- dorsal motor nucleus of the vagus and nucleus ambiguous 2. wall of target tissue 3. heart 4. gut
For sacral parasympathetic outflow, name the preganglionic nucleus and its location (1), the fibers that it travels as (2), the location of the ganglion (3), and what it innervates (4 and 5).
- sacral cord levels S2-S4 2. pelvic splanchnic nerves 3. wall of target tissue 4. bladder 5. rectum
Identify the parts of the neuron.
- dendrites 2. cell body 3. axon 4. axon terminal
What is the classification of this neuron based on structure? Based on function?
- multipolar neuron - motor or interneuron
What is the classification of this neuron based on structure? Based on function?
- bipolar - special sensory
What is the classification of this neuron based on structure? Based on function?
- unipolar - general sensory
What types of synapses are shown here (based on which neuronal components are involved)?
- axosomatic synapse 2. axodendritic synapse 3. axoaxonic synapse
Identify 1 and 2. What type of synapse is shown?
- axon terminal 2. dendrite axodendritic synapse
Identify what is at the “?”. Are these axons myelinated or unmyelinated?
- Node of Ranvier - myelinated
What does this image depict?
cross-section of myelinated axons
Identify 1 and 2. Are these nerve fibers myelinated?
- Node of Ranvier 2. axons myelinated
Distinguish between encapsulated and unencapsulated sensory receptors.
- encapsulated - receptors with layered capsules and thin capsules- unencapsulated - receptors with free nerve endings and endings with accessory structures
What is Meissner’s corpuscle and its it encapsulated? What does it sense? Where is it found? What type of fiber does it contain?
- elongated, encapsulated endings in the dermal papillae of hairless skin- discriminative touch- concentrated in finger tips- A-beta fibers - fast conducting
What is Pacinian corpuscle and is it encapsulated? What does it sense? Where is it found? What type of fiber does it contain?
- encapsulated- detection of vibration- concentrated in fingers and palms- A-beta fiber - fast conducting
What are free nerve endings?
- branching terminations of sensory fibers in the skin with no obvious specialization around them other than partial ensheathment by Schwann cells- provide sensation of pain, crude touch, and temperature
Identify the components of the axon reflex. What is the triple response?
- the skin is scratched2. the skin reddens due to capillary dilation (REDLINE?)3. free nerve ending discharge and conduct a signal to the: - spinal cord (orthodromic conduction) - branches (antidromic conduction) - release of substance P - arteriolar dilation (THE FLARE) - activation of mast cells (release of histamine) - increased capillary permeability (THE WHEAL)*triple response noted in CAPS
What are the Rexed laminae?
Laminae I, II, V
Which of the Rexed laminae play a role in pain transmission and pain regulation?
- pain transmission - Lamina I, II, V- pain regulation - Lamina II
What is the input to the periaqueductal gray?
- amygdala - anxiety, emotional pain regulation- dorsolateral prefrontal cortex - cognitive (?) pain regulation
Identify the structures in the neuroanatomical basis of pain regulation. What is the role of each? Identify the neurotransmitters involved.
periaqueductal gray stimulates the nucleus raphe magnus which sends a signal via the raphe spinal tract and serotonin to the inhibitory interneuron in Lamina II
What is a lower motor neuron?
- innervates striated muscles- last neuron in chain of neurons- includes A-alpha and A-gamma motor neurons
What are the signs and symptoms of a lower motor neuron lesion?
- atonia - loss of muscle tone- areflexia - loss of myotatic (knee jerk) reflex- flaccid paralysis - no muscle tone; patient cannot contract the muscle- fasciculations - spontaneous muscle contractions- atrophy - loss of muscle tissue
What are the signs and symptoms of a upper motor neuron lesion?
- spastic paralysis- hypertonus (flexors of arms and extensors of leg)- hyperreflexia - exaggerated knee jerk reflex- negative plantar reflex (Babinski sign) - abnormal reflex on the bottom of the foot so when the foot is stroked, the toes curl upward- atrophy of disuse
What is spastic paralysis?
chronic pathological condition in which the muscles are affected by persistent spasms and exaggerated tendon reflexes because of damage to motor nerves of the central nervous system
What is a flexor reflex?
- also called withdrawal reflex- input from cutaneous receptor travels to the spinal cord and synapses with an alpha motor neuron via an interneuron- for example, put your hand on a sharp needle and your arm pulls back quickly
What is a myotatic reflex?
- stretch spindle in the muscle is stretched- A-alpha sensory fiber goes up to the dorsal horn of the spinal cord- in a monosynaptic synapse, the A-alpha sensory fiber synapses directly with the alpha motor neuron- alpha motor neuron goes back to the muscle to stimulate the motion
What is the neuroanatomical significance of the internal capsule?
a section of white matter in the brain that contains the axons descending from the motor cortex; part of the corticospinal (pyramidal) tract
What is the role of the periaqueductal gray? What are the side effects?
- deep brain stimulation and control of pain- side effects: abnormal eye movements, smothered feeling, bladder fullness, nausea, vertigo, increased or decreased blood pressure
What is the neuroanatomical significance of the cerebral peduncle?
section of the midbrain carrying the motor neurons from the internal capsule to the basilar pons; part of the corticospinal (pyramidal) tract
What is the neuroanatomical significance of the pyramids?
section in the medulla that contains the descending motor neurons; also the site of decussation in which the neurons cross-over to the other side; part of the corticospinal (pyramidal) tract
What is the neuroanatomical significance of the posterolateral spinal cord?
(?)
What is the origin, termination, and function of the corticobulbar tract?
- origin - cortex- termination - brainstem- function - controls the muscles of the face, head, and neck by innervating the nuclei for CN V, VII, XI, and XII (and IX and X via the nucleus ambiguous)
What is the origin, termination, and function of the corticopontine tract?
- origin - cortex- termination - basilar pons- function - innervates the nuclei for CN V, VII, and XII
Identify the effect on leg and arm muscles of the activation of the corticospinal tract.
- extensor muscles in upper extremity- flexor muscles in lower extremity- control of hand musculature (primary effect!)
Identify the effect on leg and arm muscles of the activation of the rubrospinal tract.
control of proximal arm and leg musculature
Identify the effect on leg and arm muscles of the activation of the vestibulospinal tract.
control of axial musculature (balance)
Identify the effect on leg and arm muscles of the activation of the reticulospinal tract.
control of axial musculature (walking)
Identify the effect on leg and arm muscles of the activation of the raphe spinal tract.
control of incoming pain signals
Identify the location of the preganglionic and postganglionic nerve cell bodies in the sympathetic division of the ANS. What are the neurotransmitters in each for the sympathetic division?
- preganglionic neuron cell body - lateral horn of T1-L2 with acetylcholine as its neurotransmitter- postganglionic neuron cell body - sympathetic ganglia with norephinephrine as its neurotransmitter
What are the courses of the preganglionic and postganglionic neurons in the ANS?
- preganglionic neuron - cell body of origin located in CNS and terminates in the ganglion- postganglionic neuron - terminates in the target tissue
Identify the location of the preganglionic and postganglionic nerve cell bodies in the parasympathetic division of the ANS. What are the neurotransmitters in each for the parasympathetic division?
- preganglionic neuron cell body - brainstem autonomic nuclei and the saccral cord with acetylcholine as its neurotransmitter- postganglionic neuron cell body - parasympathetic ganglia in the wall of viscera with acetylcholine as its neurotransmitter
List the cranial and spinal nerves that carry sympathetic fibers.
lateral horn of spinal cord levels T1-L2 (thoracolumbar)
List the cranial and spinal nerves that carry parasympathetic fibers.
CN III (occulomotor), VII (facial), IX (glossopharyngeal), X (vagus), and lateral horn of sacral cord S2-S4 (craniosacral)
Identify the levels of the neuraxis that contain preganglionic sympathetic nerve cell bodies.
T1-L2
Identify the intermediolateral cell column (lateral horn).
place of the sympathetic preganglionic nerve cell body
By what route do sympathetic fibers reach the cranium (and cranial nerves)? Are these pre- or postganglionic fibers?
preganglionic nerve cell bodies in T1-L2 have axons that go to the paravertebral (chain) ganglion, prevertebral (collateral) ganglion, and adrenal medulla; postganglionic nerve fibers then reach the head via cervical ganglia and the carotid plexus
What effect does sympathetic activation have on pupil diameter?
dilates pupils
What effect does sympathetic activation have on blood vessel diameter?
constricts blood vessels
What effect does sympathetic activation have on salivation?
increase salivation
What effect does sympathetic activation have on the bronchi?
dilates the bronchioles
What effect does sympathetic activation have on the heart rate?
increases rate and force of contraction
Describe Horner syndrome and list/describe the resulting conditions.
- a loss of sympathetic innervation to the face- symptoms: - ptosis - eyelid droop (superior tarsal muscle) - miosis - small pupil - endophthalmos - apparent sunken eye - anhydrosis - dry skin - heterochromia - eyes are each a different color (if Horner syndrome before 2 years of age)
Describe the enteric nervous system (purpose, plexuses, etc.).
- provides innervation for intestinal tract, pancreas, and gall bladder- neural plexus between layers of muscle and endothelium in the intestinal tract - myenteric plaxus (of Auerbach) - submucous plexus (of Meissner)- provides primary control of motility and secretion
Identify the levels of the neuraxis that contain preganglionic parasympathetic nerve cell bodies.
brainstem autonomic nuclei (midbrain, pons, and medulla) and sacral cord (S2-S4)
By what route do parasympathetic fibers reach the thorax and abdomen? Are these pre- or postganglionic fibers?
- vagus preganglionic nerve cell bodies in dorsal motor nucleus and nucleus ambiguous have axons that travel with other vagus nerve fibers that terminate in the wall of the target tissue (which is the location of the postganglionic nerve cell bodies)- sacral preganglionic nerve cell bodies in the lateral horn of S2-S4 exit within the ventral root and course within splanchnic nerves and terminate in the wall of target tissue (which is the location of the postganglionic nerve cell bodies)
What effect does parasympathetic activation have on pupil diameter?
pupil consticts
What effect does parasympathetic activation have on salivation?
salivation increases
What effect does parasympathetic activation have on heart rate?
decreases rate and force of contraction
What is effect produced by the parasympathetic fibers of CN III (occulomotor)?
- pupilary constictor muscle fibers decrease pupil diameter (pupilary reflex)- ciliary muscle accommodates lens for near vision
What is effect produced by the parasympathetic fibers of CN VII (facial)?
- nasal and lacrimal glands produce lacrimation- submandibular and sublingual salivary glands produce a thin, watery mucous
What is effect produced by the parasympathetic fibers of CN IX (glossopharyngeal)?
parotid salivary gland produces a thin, watery mucous
What is effect produced by the parasympathetic fibers of CN X (vagus)?
- reduces heart rate and blood pressure- increases gastric secretion and peristaltic activity
What is effect produced by the parasympathetic fibers of the sacral cord S2-S4?
increases intestinal secretion and peristaltic activity
List the sympathetic pathway of the pupillary reflex.
lateral horn -> paravertebral chain ganglion -> superior cervical ganglion -> carotid plexus -> eye (?)
List the sympathetic pathway for salivation.
lateral horn -> paravertebral chain ganglion -> superior cervical ganglion -> carotid plexus -> glands (?)
List the sympathetic pathway to the bronchi.
lateral horn -> paravertebral chain ganglion -> inferior (stellate) cervical ganglion -> brachial plexus
List and describe the major functions of the nervous system.
- gathers information or sensory input via sensory receptors- through integration, it processes and interprets the sensory input and decides what, if any, action should be taken- produces a response or motor output, activating effector organs
List and describe the two divisions of the nervous system. What are some of the structures within each division?
- central nervous system (CNS) - integrative and control centers of the body; composed of the brain and the spinal cord- peripheral nervous system (PNS) - communication lines between the CNS and the rest of the body; composed of all nervous structures outside the brain and spinal cord; composed of structures such as cranial nerves (arise from brain), spinal nerves (arise from spinal cord), ganglia (groups of neuron cell bodies not in CNS), and plexuses (intermingling of neuron cell process from ventral rami of different cord levels)* a nerve is a collection of axons (i.e. a process of neurons) found in the PNS
List and describe the two types of cells found in nervous tissue. What are the major function(s) of each?
- nerve cells or neurons - functional unit of nervous system; main active and excitable cells; generate and transmit action potentials; cannot go through mitosis- neuroglia, glia, or supporting cells - supporting cells; outnumber neurons; can provide structural support, electrical insulation (myelin sheath), and metabolic exchanges between vascular system and neurons; do NOT generate action potentials; can go through mitosis
List and describe the special characteristics of neurons.
- extreme longevity - most neurons survive over 100 years- most are amitotic - lose the ability to divide (typically but there are some exceptions)- high metabolic rate - they need oxygen and glucose; dead in a few minutes without oxygen
List and describe the basic structural components of neurons. What are the major function(s) of each part?
- neuron cell body/perikaryon - man function is that it acts as the biosynthetic center of the neuron; always unmyelinated; no action potentials (nerve impulses)- processes: - dendrites - main function is that it acts as main receptive or main input regions of neuron; always unmyelinated; no action potentials; a neuron can have one or more dendrites - axon/nerve fiber - main function is that it acts as conducting region of neuron as it can generate action potentials and transmit them; can be myelinated; a neuron can only have 1 axon; at the end, axon terminal releases chemical neurotransmitters when impulse reaches it
What organelles are located in each component of a neuron?
- neuron cell body/perikaryon - nucleus with a prominent nucleolus; regular organelles except there is no centrioles (because they are only needed for mitosis), many rough ER and ribosomes (Nissl bodies) for production of proteins, many microtubules for structure and internal trafficking- dendrites - no golgi apparatus- axon/nerve fiber - no Nissl bodies
What is a Nissl body?
clumps of rough ER and ribosomes that stain purple with hematoxin
List and define the classification of neurons based on structure.
- multipolar neurons - 3 or more processes- bipolar neurons - 2 processes (very rare)- unipolar neurons - 1 process (cell body is attached like a “T”)
List and define the classification of neurons based on function.
- sensory or afferent neurons - carry impulse toward the CNS- motor or efferent neurons - carry impulse away from the CNS- interneurons or association neurons - found between motor and sensory neurons
How do the 2 classification schemes for neurons (based on structure and based on function) overlap?
- multipolar neurons = motor (efferent), or interneurons- bipolar = special sensation- unipolar = sensory (general)
List and describe the classification of synapses based on which neuronal components are involved.
- axodendritic synapse - axon terminal and dendrite - axosomatic synapse - axon terminal and cell body- axoaxonic synapse - between axons- dendrodendritic synapse - between dendrites- dendrosomatic synapse - between dendrite and cell body
Which two types of synapses are the most common?
axodendritic and axosomatic synapses
Define presynaptic neuron.
neuron carrying impulse/signal toward synapse
Define postsynaptic neuron.
neuron carrying impulse/signal away from synapse (note: this can also be an effector cell)
List and describe the 2 varieties of synapses based on the signal used to transmit information between cells.
- electrical synapses - action potentials conducted directly between adjacent cells through gap junctions- chemical synapses - signals from cell to cell across interstitial fluid
Where are the prominent locations for electrical synapses in the human body?
allows cells to synchronize so can be found in places like the heart
What are the steps involved with information transfer at a chemical synapse?
- nerve impulse arrives at synaptic end bulb of a presynaptic axon2. depolarization causes voltage-gated calcium channels to open3. calcium ions signal for the release of neurotransmitter (stored in synaptic vesicles) via exocytosis into the synaptic cleft4. neurotransmitter diffuses across synaptic cleft and binds to neurotransmitter receptors at the postsynaptic membrane; each receptor is part of a ligand-gated channel5. the binding of the neurotransmitter opens the associated ligand-gated channel allowing ions to flow across the postsynaptic membrane6. this produces local changes in membrane potential called the postsynaptic potential, a type of graded potential (depolarizing or hyperpolarizing)
What cellular components are found at a chemical synapse?
- presynaptic knob (synaptic end bulb or presynaptic axon terminal)- synaptic cleft- postsynaptic membrane
What are the ways a neurotransmitter can be removed from the postsynaptic receptor?
- degradation by enzymes- reuptake by astrocytes or presynaptic terminal- diffusion away from synapse
List the 6 types of neuroglia and where they are located (CNS or PNS).
- astrocyte - CNS- microglial cell - CNS- ependymal cell - CNS- oligodendrocyte - CNS- Schwann cell - PNS- satellite cells - PNS
Describe oligodendrocytes.
- function is to produce myelin sheaths in CNS for MORE THAN 1 neuron- predominate glial cell in the brain- mostly in white matter
Describe astrocytes.
- perivascular feet wrap around blood vessels and cover endothelial cells of the capillaries to contribute to the blood-brain barrier and regulate vasodilation- transfers ions, etc.- embryonic and fetal development uses this scaffolding- can get rid of excess neurotransmitters- largest of the neuroglia with large radiating processes- more commonly in gray matter than white matter- connect with one another through gap junctions to form large networks of cells in CNS
Describe ependymal cells.
- surround the central canal of the spinal cord and lines spaces in the brain- joined to one another- have cilia which extend into the CSF and helps circulate CSF- transport and secrete materials derived from body’s plasma
Describe microglia cells.
- originate from blood monocytes- when activated, proliferate and become phagocytotic and are APCs in areas of injury- nucleus is very elongated and dense-staining
Describe Schwann cells.
- produce myelin in the PNS; wrap around the axon- one Schwann cell makes up one internodal segment on one axon
Describe satellite cells.
- found around the cell bodies in ganglion- job is not well understood but may be protecting the cell body
Define white matter.
composed of primarily myelinated axons and some neuroglia; white due to myelin
Define gray matter.
composed of neuronal cell bodies, dendrites, unmyelinated axons, axon terminals, and neuroglia; gray due to Nissl bodies and lack of myelin
Define ganglion.
clusters of neuronal cell bodies in the PNS
Define nucleus.
clusters of neuronal cell bodies in the CNS
Define nerve.
bundle of neuronal axons in PNS
Define tract.
bundle of neuronal axons in CNS
List and describe the connective tissue coverings associated with nerves.
- endoneurium - around individual axons- perineurium - forms fascicles- epineurium - around the whole nerve
List and describe the components of a nerve.
- neuron process- Schwann cells- connective tissue - keeps it organized- blood vessels - brings in oxygen/nutrients and takes away waste- lymphatic vessels
List and describe the classification of nerves based on function (which direction they are transmitting their nerve impulses).
- sensory (afferent) - conduct action potentials toward the CNS- motor (efferent) - conduct action potentials away from the CNS- mixed nerves - contain both sensory and motor fibers
List and describe the classification of nerves based on their origination point.
- cranial nerves - originate at brain; 12 pairs- spinal nerves - originate at spinal cord; 31 pairs
Describe the interaction of Schwann cells with unmyelinated nerve fibers.
unmyelinated axons are still associated with Schwann cells and snuggle up next to them but they aren’t insulated because the Schwann cells don’t wrap around them; Schwann cells just provide structure for the axons
What are the functions of myelin sheaths?
- protect and electrically insulate axons from other axons- increases speed and nerve impulse transmission
How does the myelin sheath form?
Schwann cell wraps around and around the axon; multiple layers of plasma membrane fuse together leaving a bunched up section of the Schwann cell on the outside of the sheath called the neurilemma
Define and describe continuous vs. saltatory conduction.
- continuous conduction - unmyelinated axons; the electrical signal travels slowly since action potential needs to be triggered at each sodium channel along the length of the axon- saltatory conduction - myelinated axons; the electrical signal travels fast since the action potential only needs to be triggered at the unmyelinated nodes of Ranvier along the length of the axon
What is the rate of impulse propagation in an axon dependent upon?
- axon diameter - impacts ion flow and therefore, impacts propagation rate- myelination - continuous vs. saltatory conduction
Identify the location of the cell body of origin and the course of the abducens nerve.
cell body of origin in the pontine tegmentum -> rootlets exit anteriorly -> longest intracranial course -> lateral rectus muscle -> abducts eye
What structure is innervated by the abducens nerve?
lateral rectus muscle
List the signs and symptoms seen following a lesion of the abducens nerve.
- diplopia (double vision) at rest since affected eye looks medially- diplopia (double vision) when asked to look lateral on the lesioned side- compensatory head-turn away from side of lesion
Identify the location of the cell body of origin and the course of the trochlear nerve.
cell body of origin in the midbrain tegmentum -> rootlets exit posteriorly -> superior oblique muscles
Name the structure innervated by the trochlear nerve.
superior oblique muscle
List the signs and symptoms seen following a lesion of the trochlear nerve.
- extorsion of eye (top of eye is tipped laterally)- accompanying vertical double vision (diplopia)- weakness during attempted downward medial gaze- compensatory head-tilt toward intact shoulder
Identify the location of the cell body of origin of both components and the course of the oculomotor nerve.
- GVE cell body of origin in the midbrain tegmentum -> rootlets exit into interpeduncular fossa -> Edinger-Westphal nucleus -> ciliary ganglion- SE cell body of origin in the midbrain tegmentum -> rootlets exit into interpeduncular fossa -> oculomotor nucleus -> all extraocular muscles and levator palpebrae muscle except SO and LR
Name the structure(s) innervated by the oculomotor nerve.
- intrinsic muscles of the eye- medial rectus, inferior oblique, inferior rectus, superior rectus, and levator palpebrae muscles
List the signs and symptoms seen following a lesion of the oculomotor nerve.
- SE functional component - ptosis - paralysis of levator palpebrae muscle makes eyelid droop - eye position - down and out- GVE functional component (parasympathetic) - dilated, fixed pupil - paralysis of accommodation
How does ptosis due to a lesion of the oculomotor nerve differ from that seen in Horner syndrome?
in Horner’s syndrome, the drooping of the eyelid is much less severe (?)
What is the significance of unequal pupil size?
it could be used to signal if a person has an uncal herniation since the parasympathetic fibers of CN III (which are one of the controls of pupil size) are unmyelinated and easily damaged by an uncal herniation (?)
Define diplopia. How can the patient minimize diplopia?
- diplopia - double vision- can be compensated for by tilting the head so that both eyes align
Name the neuroanatomical structure that corresponds with the center for lateral gaze.
abducens nucleus controls eye movements in the horizontal plane (center for lateral gaze); loss of the abducens nucleus results in paralysis of lateral gaze
Name the tract that contains the axons that arise from the internuclear neurons of the abducens nucleus.
medial longitudinal fasciculus
Name the source of the axons that terminate in the ciliary ganglion.
Edinger-Westphal nucleus in the midbrain -> ciliary ganglion
Name the muscle innervated by the oculomotor nerve that holds the upper eyelid up.
levator palpebrae muscle
Describe the anatomical basis of paralysis of lateral gaze.
- abducens nucleus controls the lateral rectus muscle- abducens nucleus is also connected to the oculomotor nuclear complex via internuclear neurons- abducens nucleus controls eye movements in the horizontal plane (center for lateral gaze)- loss of the abducens nucleus results in paralysis of lateral gaze
Describe the anatomical basis of internuclear ophthalmoplegia.
- paralysis of the contralateral medial rectus muscle because the internuclear neuron (neuron connecting abducens and oculomotor nuclei) is cut- medial rectus does not contract on attempted ipsilateral horizontal gaze- medial rectus does not contract during accomodation- nystagmus (quivering) in abducting eye contralateral to lesion
Describe the pupillary light reflex.
- if you shine a light in one eye, the afferent component comes back to the pretectum and measures the amount of light coming in- efferent fibers go out and affect both eyes- direct response - response of the eye into which the light was shined- consensual response - the response of the opposite eye in which the light was not shined
Identify the location of the cell bodies of origin as well as the origin and termination of the SE component of the hypoglossal nerve.
hypoglossal nucleus in medulla -> rootlets exit adjacent to pyramid -> innervate intrinsic tongue muscles
Identify the location of the cell bodies of origin as well as the origin and termination of the SE component of the spinal accessory nerve.
spinal gray in cervical region -> innervate trapezius and sternocleidomastoid muscles
Identify the location of the cell bodies of origin as well as the origin and termination of the SVE component of the vagus nerve.
nucleus ambiguus -> muscles of speech and swallowing
Identify the location of the cell bodies of origin as well as the origin and termination of the 2 GVE components of the vagus nerve.
- dorsal motor nucleus of vagus -> viscera from neck to transverse colon (parasympathetic)- nucleus ambiguus -> cardiac inhibition
Identify the location of the cell bodies of origin as well as the origin and termination of the GSA component of the vagus nerve.
skin of ear and middle ear cavity -> superior ganglion of vagus nerve -> trigeminal spinal nucleus
Identify the location of the cell bodies of origin as well as the origin and termination of the GVA component of the vagus nerve.
epiglottis -> inferior ganglion of vagus nerve -> solitary nucleus
Identify the location of the cell bodies of origin as well as the origin and termination of the SVA component of the vagus nerve.
epiglottis (taste) -> inferior ganglion of vagus nerve -> solitary nucleus
Identify the location of the cell bodies of origin as well as the origin and termination of the SVE component of the glossopharyngeal nerve.
nucleus ambiguus -> stylopharyngeus muscle
Identify the location of the cell bodies of origin as well as the origin and termination of the GVE component of the glossopharyngeal nerve.
inferior salivatory nucleus -> otic ganglion -> parotid gland
Identify the location of the cell bodies of origin as well as the origin and termination of the GSA component of the glossopharyngeal nerve.
skin of ear -> superior ganglion of glossopharyngeal nerve -> trigeminal spinal nucleus
Identify the location of the cell bodies of origin as well as the origin and termination of the 2 GVA components of the glossopharyngeal nerve.
- carotid body and carotid sinus (blood pressue and blood oxygen/carbon dioxide)- posterior 1/3 of tongue -> inferior ganglion of glossopharyngeal nerve -> solitary nucleus
Identify the location of the cell bodies of origin as well as the origin and termination of the SVA component of the glossopharyngeal nerve.
posterior 1/3 of tongue -> inferior ganglion of glossopharyngeal nerve -> solitary nucleus
Name the striated muscle(s) innervated by the hypoglossal nerve.
intrinsic tongue muscles
Name the striated muscle(s) innervated by the spinal accessory nerve.
trapezius and sternocleidomastoid muscles
Name the gland innervated by CN IX. Name the parasympathetic ganglion involved.
- parotid gland- otic ganglion
What is the effect of a lesion of CN XII?
- lower motor neuron lesion- tongue deviates toward the side of the lesion- fasciculations- atrophy
What is the effect of a lesion of CN XI?
- patient cannot turn head against resistance- patient cannot shrug shoulders against resistance
What is the effect of the jugular foramen syndrome (affects CN IX, X, XI, and XII)?
- pain in or behind the external ear- headache (irriation of meningeal branch of CN X)- hoarseness (muscles of speech)- dysphagia (difficulty in swallowing, muscles of swallowing)
