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Nervous System > Nervous System Chapter 12 > Flashcards

Nervous System Chapter 12 Flashcards

1
Q

Diencephalon

A
  • forms the central core of the forebrain
  • surrounded by cerebral hemispheres
  • consists of thalamus, hypothalamus, and epithalamus
  • enclosed in 3rd ventricle
  • gray matter
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2
Q

Thalamus (physical attributes)

A
  • bilateral egg-shaped nuclei
  • forms walls of the 3rd ventricle
  • 80% of diencephalon
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3
Q

Thalamus (function)

A
  • relay station for info coming into the cerebral cortex
  • many nuclei that each have a functional specialty
  • each nuclei projects fibers to and receives fibers from a specific region of the cerebral cortex
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4
Q

How does the thalamus fulfill it’s function?

A
  • afferent impulses from senses and all body parts converge on the thalamus and synapse w/ one of its nuclei
  • info is sorted and edited
  • impulses with similar functions are relayed as a group via the internal capsule to to the appropriate area of the sensory cortex and cortical association areas
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5
Q

As afferent impulses reach the thalamus what is our recognition like?

A

crudly pleasant or unpleasant

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6
Q

Other inputs that funnel through the thalamic nuclei ascending to the cerebral cortex

A
  • inputs that regulate emotion and visceral info from the hypothalamus
  • instructions that help direct activity of motor cortices from the cerebellum and basal nuclei
  • inputs for memory or sensory integration that are projected to specific association corties
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7
Q

Hypothalamus (physical attributes)

A
  • forms inferolateral walls of the 3rd ventricle
  • caps brain stem and merges into the midbrain inferiorly
  • extends from optic chiasma to posterior of mammillary bodies
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8
Q

Mammillary bodies

A

-relay stations in the olfactory pathways

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9
Q

Infandibulum

A

-stalk of hypothalamic tissue that connects pituitary gland to the base of the hypothalamus

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10
Q

Hypothalamus (function)

A
  • has many functionally impt nuclei
  • main visceral control center
  • impt to body homeostasis
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11
Q

Homeostatic roles of the hypothalamus

A
  1. Control of the autonomic nervous system–influences blood pressure, rate and force of heartbeat, digestive tract motility, eye pupil size
  2. Initiate physical responses to emotions–acts through ANS to initiate physical expression of emotion (fear causes pounding heart) and is the heart of the limbic system (nuclei perceive pleasure, fear, rage, drives)
  3. Regulate body temperature
  4. Regulate food intake–in response to blood levels of nutrients or hormones–regulates feelings of hunger or satiety
  5. Regulate water balance and thirst–osmoreceptors are activated when body fluid is too concentrated–triggers release of ADH causing kidneys to retain water–also stimulate neurons in thirst center
  6. Regulate sleep-wake cycles–acts w/ other regions of brain to regulate this
  7. Control endocrine system function-releasing and inhibiting hormones control the secretion of hormones by the anterior pituitary–supraoptic and paraventricular nuclei produce ADH and oxytocin
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12
Q

Epithalamus

A
  • dorsal portion of diencephalon

- forms roof of 3rd ventricle

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13
Q

Pineal gland

A
  • extends from posterior border of epithalamus

- secretes melatonin

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14
Q

Brain stem regions, physical attributes

A
  • midbrain, pons, medulla oblongata
  • 2.5% of brain mass
  • has nuclei of gray matter embedded in the white matter
  • between cerebrum and spinal cord
  • provides pathway for fiber tracts b/t higher and lower neural centers
  • nuclei are associated w/ 10 of 12 cranial nerves
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15
Q

Midbrain (physical attributes)

A
  • b/t dienchephalon and pons

- has bulging cerebral peduncles

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16
Q

Cerebellar peduncles

A
  • connect the midbrain and cerebellum dorsally

- has fiber tracts

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17
Q

Cerebral aqueduct

A
  • connects 3rd and 4th ventricle

- runs through the midbrain

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18
Q

Periaqueductal gray matter

A
  • surrounds aqueduct
  • involved in pain suppression and links the fear-perceiving amygdaloid body and ANS pathway that control fight or flight response
  • has nuclei that control two cranial nerves: oculomotor and trochlear
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19
Q

Corpora quadrigemina

A

-largest midbrain nuclei–has 4 domelike protrusions on the dorsal midbrain surface

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20
Q

Superior coliculi of corpora quadrigemina

A
  • superior pair of corpora quadrigemina
  • visual reflex center–coordinate head and eye movements when we visually follow a moving object even if not consciously looking at it
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21
Q

Inferior coliculi of corpora quadrigemina

A
  • auditory relay from hearing receptors of the ear to the sensory cortex
  • act in reflexive responses to sound ex: startle reflex
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22
Q

Substantia nigra

A
  • deep to cerebral peduncle
  • its dark color reflects a high content of melanin pigment which is a precursor of neurotransmitter, dopamine, released by these neurons
  • functionally linked to basal nuclei
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23
Q

Parkinson’s disease

A

-degeneration of dopamine-releasing neurons in substantia nigra

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24
Q

Red nucleus

A
  • deep to substantia nigra
  • reddish hue due to rich blood supply and presence of iron pigment in its neurons
  • relay nuclei in some descending motor pathways that effect limb flexion
  • embedded in the reticular formation (system of small nuclei scattered through the core of the brain stem)
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25
Q

Pons

A
  • between midbrain and medulla oblongata
  • 4th ventricle separates it form the cerebellum
  • composed of conduction tracts
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26
Q

Deep projection fibers of the pons

A

-run longitudinally as part of pathway b/t higher brain centers and spinal cord

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27
Q

Superficial ventral fibers of the pons

A
  • oriented transversely and dorsally
  • form middle cerebral peduncles
  • connect pons bilaterally w/ two sides of cerebellum
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28
Q

Pontine nuclei

A
  • in the superficial ventral fibers of the pons–relay conversations b/t motor cortex and cerebellum
  • trigeminal, abducens, and facial nerves start here
  • some are part of reticular formation
  • some help medulla oblongata maintain normal breathing rhythm
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29
Q

Medulla oblongata

A
  • most inferior part of the brain stem
  • blends into the spinal cord at the foramen magnum
  • medulla and pons form ventral wall of the 4th ventricle
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30
Q

Pyramids of medulla

A
  • on midline of medulla’s ventral aspect

- formed from large pyramidal tracts descending form the motor cortex

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31
Q

Decussation of the pyramids

A
  • just above medulla-spinal cord junction, most of the fibers cross to the opposite side before continuing to the spinal cord
  • this makes each side of the cerebral hemisphere control voluntary movements of muscles on the opposite side of the body
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32
Q

Olivary nuclei

A

-in medulla–relay sensory information on the degree of stretch in muscles and joins to the cerebellum

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33
Q

Which cranial nerves are associated with the medulla?

A

-hypoglossal, glossopharyngeal, vagus

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34
Q

Functions of the medulla

A
  1. cardiovascular center–cardiac center: adjusts force and rate of heart contraction and vasomotor: changes blood vessel diameter to regulate blood pressure
  2. respiratory centers–generate respiratory rhythm (in concert with pontine centers) control the rate and depth of breathing
  3. Various other centers–regulate activities such as vomiting, hiccuping, swallowing, coughing, and sneezing
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35
Q

Cerebellum (physical attributes)

A
  • 11% of brain mass
  • dorsal to pons and medulla
  • hemispheres are separated by vermis
  • has folia–“leaves”, convolutions that are pleatlike gyri
  • connected to brain stem by superior, middle, and inferior peduncles
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36
Q

Cerebellum functions

A
  • processes inputs from cerebral motor cortex–provides precise timing and appropriate patterns of skeletal muscle contraction for smooth, coordinated movements and agility
  • -these occur subconsciously
  • plays role in cognition (not well understood)
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37
Q

Purkinje cells

A

in the cerebellar cortex-large cells with extensive branched dendrites–are the only cortical neurons that send axons through the white matter to synapse with the central nuclei of the cerebellum

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38
Q

Arbor vitae

A

white matter of cerebellum resembles branching tree

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39
Q

Cerebral peduncles

A
  • paired fiber tracts
  • connect cerebellum to the brain stem
  • ipsilateral—fibers entering and leaving are on the same side of the body
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40
Q

Superior cerebellar peduncles

A
  • connect cerebellum and midbrain

- carry instructions from neurons to the cerebral motor cortex via thalamic relays

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41
Q

Middle cerebellar peducles

A

-carry one-way communications form the pons to the cerebellum, advising it of voluntary motor activities initiated by the motor cortex

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42
Q

Inferior cerebellar peduncles

A
  • connect medulla and cerebellum
  • convey sensory info to cerebellum from muscle proprioceptors throughout the body and bestibular nuclei of the brain stem, which are concerned with equilibrium and balance
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43
Q

Cerebellar injury results in what?

A

loss of motor tone and clumsy movements

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44
Q

Limbic system

A

-group of structures on the medial aspect of each cerebral hemisphere and diencephalon and encircles the upper part of the brain stem

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45
Q

Fornix of the limbic system

A

-fiber tract that links limbic system regions together along w/ other tracts

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46
Q

Amygdaloid body

A

-in limbic system–critical for responding to perceived threats w/ fear or aggression

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47
Q

Cingulate gyrus

A

-in limbic system–plays role in expressing emotions through gestures and in resolving mental conflicts when we are frustrated

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48
Q

Psychosomatic illness

A

-hypothalamus (most limbic output relayed through here) is neural clearing house for autonomic function and emotional response–stress can lead to heartburn and high blood pressure

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49
Q

What does the interaction between the limbic system and prefrontal lobes create?

A

-relationship b/t feelings and thoughts

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50
Q

What role do the hippocampus and amygdaloid body share?

A

-memory

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51
Q

Reticular formation (physical attributes)

A
  • extends through medulla, pons, and midbrain
  • composed of loosely clustered neurons which for columns along the length of the brain stem: raphe nuclei, medial group of nuclei, and lateral group of nuclei
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52
Q

Reticular activating system

A
  • send continuous stream of impulses to the cerebral cortex to keep the cortex alert, conscious, and enhance its excitability
  • filters these sensory inputs: repetitive, weak, or familiar signals are filtered out, but unusual, significant or strong impulses reach consciousness
  • –if this didn’t occur sensory overload would drive us crazy–LSD inhibits this
  • -EX: don’t notice wrist watch until the clasp breaks
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53
Q

What inhibits RAS?

A
  • sleep centers in the hypothalamus and other neural regions

- depressed by alcohol, sleep inducing drugs, and tranquilizers

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54
Q

Motor arm of the RAS

A
  • some of its motor nuclei project to motor neurons in the spinal cord via reticulospinal tracts that help control skeletal muscles during coarse limb movements
  • other motor nuclei such as vasomotor, cardiac, and respiratory centers of the medulla, are autonomic centers that regulate visceral motor functions
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55
Q

Electroenchephalogram (EEG)

A
  • records some of the electrical activity of neurons
  • electrodes placed on scalp and connected to an apparatus that measures voltage differences b/c various cortical areas
  • used for diagnosing epilepsy and sleep disorders
  • flat EEG is clinical evidence of brain death
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56
Q

Brain Waves

A
  • pattern of neuronal electrical activity recorded by EEG that are generated by synaptic activity at the surface of the cortex, rather than by action potentials in the white matter
  • each person’s brain waves are unique
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57
Q

Alpha waves

A

-regular, rhythmic, low amplitude, synchronous waves
-indicated a brain that is idling in a calm, relaxed, state of wakefullness
8-13 Hz

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58
Q

Beta waves

A

-rhythmic but less regular than alpha and have a higher frequecy
-occur when mentally alert, as when concentrating on a problem or visual stimulus
14-30 Hz

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59
Q

Theta waves

A

-more irregular
-common in children
-uncommon in awake adults but may appear when they are concentrating
4-7 Hz

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60
Q

Delta waves

A

-high amplitude waves seen during deep sleep and when reticular activating system is dampened ex: during anesthesia
-in awake adults, can indicate brain damage
4 Hz

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61
Q

Absence seizures

A
  • expression goes blank for a few seconds as consciousness disappears
  • seen in children, dissapear by age 10
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62
Q

Tonic-clonic seizures

A
  • most severe, convulsive form of epileptic seizure

- can last for a few minutes

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63
Q

Aura

A
  • sensory hallucination, such as taste, smell, or flashes of light just before a seizure
  • helpful b/c it gives person time to lay down first
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64
Q

What can be done to control seizures?

A
  • anticonvulsive drugs

- vagus stimulator or deep brain stimulator (implants that stabilize brain’s electrical activity)

65
Q

Clinically conscious

A

-behavior is graded on response to stimuli as alertness, drowsiness or lethargy, stupor, and coma

66
Q

Coma

A
  • state of unconscious in which a person can’t be aroused
  • oxygen is below normal resting levels
  • this is different from sleep where brain is active and oxygen consumption resembles waking state
67
Q

Sleep

A
  • state of partial unconsciousness in which a person can be aroused
  • cortical activity is depressed but brain stem functions continue (control heart rate, respiration, bp), and environmental stimulation continues (know when there is a “bump in the night”
68
Q

NREM sleep

A
  • first 30-45 minutes of sleep are the first 2 stages of NREM
  • stages 3 and 4 are called slow-wave sleep
  • depressed by tranquilizers like diazepam
69
Q

Sleep cycle (circadian)

A
  • hypothalamus is responsible for timing of sleep cycle–suprachiasmatic nucleus is a biological clock and regulates preoptic nucleus (a sleep-inducing center)
  • 4 stages of NREM then alternates b/t REM and NREM with occasional partial arousals
  • by inactivating the reticular activating system, the preoptic nucleus puts the cerebral cortex to sleep
70
Q

REM sleep

A
  • occurs about every 90 minutes and each one gets longer (first is about 10 minutes, second is 20, ect.)
  • skeletal muscles (except ocular and diaphram) are actively inhibited, most dreaming occurs
  • alcohol and sleep medications suppress REM but not slow-wave
71
Q

Slow wave sleep importance

A
  • restorative sleep

- when we are sleep deprived we will spend more time in this sleep

72
Q

REM sleep importance

A
  • if deprived person becomes moody and depressed and exhibits various personality disorders
  • gives the brain an opportunity to analyze the day’s events and work through emotional problems in dream imagery
  • reversed learning–we dream to forget
73
Q

Stage 1 NREM

A

-relaxation begins, EEG shows alpha waves, arousal is easy

74
Q

Stage 2 NREM

A

-irregular EEG with sleep spindles (short, high amplitude bursts), arousal is more difficult

75
Q

Stage 3 NREM

A

-sleep deepens , theta and delta waves appear, vital signs decline

76
Q

Stage 4 NREM

A
  • EEG is dominated by delta waves, arousal is difficult, bed-wetting, night terrors, and sleepwalking may occur
  • stage 4 disappears throughout life
77
Q

Narcolepsy

A
  • lapse abruptly into REM sleep from awake state
  • can trigger a sudden loss of voluntary muscle control (cataplexy)-person is fully conscious but unable to move
  • orexins are selectively destroyed in patients with narcolepsy (wake-up peptides)
78
Q

Insomnia treatment

A

-drugs that block orexin will promote sleep

79
Q

Sleep apnea

A
  • temporary cessation of breathing during sleep
  • person wakes form hypoxia (lack of oxygen)
  • can occur several hundred times per night
  • often happens in obese people
80
Q

Patients with lesion to Broca’s region…

A

-can understand language but have difficulty speaking

81
Q

Patients with lesion on Wernicke’s area…

A
  • are able to speak but speak nonsense–“word salad”

- have difficulty understanding language

82
Q

Short-term memory

A
  • working memory

- look up phone number, dial it, and forget it

83
Q

Long-term memory

A
  • continually changes with time
  • STM is transferred to LTM when we want to remember something and is influenced by…
    1. emotional state-norepi is involved in memory processing of emotionally charged events
    2. rehearsal–repeating material
    3. association–tying new info with old info already stored
    4. automatic memory–not all impressions in LTM are consciously foremed
84
Q

Declarative (fact) memory

A

-learning explicit info such as names, faces, words, dates
-related to conscious thoughts and ability to manipulate symbols and language
-usually filed with context in which they were learned
(when you think of new friend you think of where you met them)

85
Q

Nondeclarative and 3 categories

A
  • less conscious or unconscious learning
  • procedural memory–piano playing
  • motor memory–riding a bike
  • emotional memory–pounding heart when you hear a snake
  • these are hard to unlearn
86
Q

Declarative memory circuit

A

-info from association cortices flow to the medial temporal lob (including hippocampus), which communicates with the thalamus and prefrontal cortex–the association cortices receive feedback from these structures–acetylcholine from basal forebrain is necessary for this circuit to function

87
Q

Procedural memory circuit

A

-sensory and motor inputs flow through the association cortices and are relayed to the premotor cortex–dopamine from the substantia nigra is necessary for this circuit to function

88
Q

Anterograde amnesia

A
  • can’t create new memories

- can still learn new skills

89
Q

Retrograde amnesia

A

-loss of memories formed in the distant past

90
Q

Long-term potentiation

A
  • persistent increase in synaptic strength that is crucial for memory formation
  • occurs in hippocampal neurons that use glutamate as a neurotransmitter
  • NMDA is a glutamate receptor–it can act as a calcium channel and initiate the cellular changes that bring about LTP
  • normally the NMDA receptors are blocked, but when glutamate binds to different receptors and depolarizes the postsynaptic terminal, the NMDA block is removed and calcium flows to the postsynaptic cell
91
Q

Meninges

A
  • 3 connective tissue membranes that lie external to the CNS organs
  • cover and protect the CNS
  • protect blood vessels and enclose venous sinuses
  • contain CSF
  • form partitions in the skull
92
Q

Dura mater

A
  • strongest meninx
  • two-layered sheet of fibrous connective tissue
  • periosteal layer–attaches to inner surface of the skill
  • meningeal layer–forms true external covering of the brain and continues in the vertebral canal as the spinal dura mater
  • layers are fused together except where they separate dural venous sinuses
93
Q

Dural venous sinuses

A

-collect venous blood from the brain and direct it to the internal jugular veins

94
Q

Dural septa

A
  • meningeal dura mater that extends inward to form flat partitions to subdivide cranial cavity
  • limit excessive movement of the brain w/in the cranium
  • -falx cerebri, falx cerebelli, and tentorium cerebelli
95
Q

Falx cerebri

A
  • dips into longitudinal fissure between the cerebral hemispheres
  • attaches to the crista galli
96
Q

Falx cerebelli

A
  • continues inferiorly from the posterior falx cerebri

- runs along vermins of the cerebelllum

97
Q

Tentorium cerebelli

A

-in transverse fissure b/t the cerebral hemispheres and the cerebellum

98
Q

Arachnoid mater

A
  • forms loose brain covering
  • separted from dura mater by serous cavity called subdural space
  • has subarchnoid space
99
Q

Subarachnoid space

A
  • below arachnoid membrane–has spiderweb like extensions that span the space and secure the arachnoid mater to the underly piamater
  • filled with CSF and contains largest blood vessels serving the brain
100
Q

Arachnoid villi

A
  • knoblike projections of acrachnoid mater
  • protrude through the dura mater and into the superior sagittal sinus
  • they absorb CSF into the venous blood of the sinus
101
Q

Pia mater

A
  • made of delicate connective tissue that has many tiny blood vessels
  • clings tightly to the brain like cellophane wrap
102
Q

Meningitis

A
  • inflammation of the meninges–can spread to the brain

- encephalitis–brain inflammation

103
Q

Cerebral spinal fluid

A
  • in and around brain and spinal cord
  • forms liquid cushion that gives buoyancy to CNS structures
  • helps nourish brain and carries some chemicals such as hormones and sleep and appetite inducing molecules
  • has similar composition to blood plasma but less protein and different ion concentrations
  • circulates through the ventricles and into the subarachnoid space and returns to the dural venous sinuses via the arachnoid villi
104
Q

Choroid plexuses

A
  • hang from the roof of each ventricle
  • form CSF
  • clusters of thin-walled capillaries enclosed by pia mater and a layer of ependymal cells lining the ventricles
105
Q

Hydrocephalus

A
  • CSF accumulates and exerts pressure on the brain b/c of an obstruction of the circulation or drainage of CSF
  • in babies their head gets big b/c their skull isn’t fused yet
  • in adults it damages the brain b/c the skull won’t move
106
Q

Blood brain barrier

A
  • impermeable epithelium of capillaries of the brain
  • allows water, respiratory gases, essential nutrients, and fat-soluble molecules to enter the neural tissue
  • blocks water-soluble molecules and potentially harmful substances
107
Q

Concussion

A
  • usually temporary alteration in brain function following a blow to the head
  • person can be dizzy or lose consciousness
  • multiple concussions over time produce cumulative damage
108
Q

Contusion

A
  • bruise on the brain
  • cause permanent neurological damage
  • cortical contusions–may remain conscious
  • brain stem contusions–always cause coma
109
Q

Subdural or subarachnoid hemmorhage

A
  • blood accumulating in the skull which increases cranial pressure and compresses the brain tissue
  • death can result
  • people who are initially lucid and the begin to deteriorate are usually hemorrhaging intracranially
110
Q

Cerebral edema

A

-swelling of the brain

111
Q

Cerebrovascular accidents (CVA)

A
  • strokes
  • occur when blood circulation to a brain area is blocked and brain tissue dies
  • most common causes is a blood clot that blocks a cerebral artery
112
Q

Ischemia

A
  • deprivation of blood supply to any tissue

- impairs delivery of oxygen and nutrients to cells

113
Q

Survival of CVA results in what deficits?

What can be done to help these?

A
  • person is paralyzed on one side of the body
  • sensory deficits
  • difficulty understanding or vocalizing speech
  • can recover partially b/c of undamaged neurons ability to sprout new branches and spread to injured area and physical therapy
114
Q

Transient ischemic attacks (TIAs)

A
  • last from 5-50 minutes
  • temporary numbness, paralysis, or impaired speech
  • these deficits aren’t permanent
115
Q

What is the main culprit for neuron-killing outside of the initial ischemic zone that wreaks the most havoc on the brain?

A
  • glutamate–excitatory neurotransmitter involved in learning and memory
  • normally glutamate binds to NMDA receptors and opens NMDA channels that allow calcium to enter the stimulated neruon–after brain injury the neurons that are deprived of oxygen disintegrate and unleash buckets of glutamate
  • this makes the glutamate act as an excitotoxin which excites the cells to death
116
Q

In excitotoxicity, the amount of calcium swamps the cell’s ability to cope and calcium homeostasis breaks down. What are the two ways high levels of calcium can kill the cell?

A
  • damages mitochondria, causing them to produce superoxide (free radical) that damages cells directly and can cause apoptosis
  • turns on synthesis of certain proteins, some of which promote apoptosis and others are enzymes that produce NO (free radical) and other inflammatory agents
117
Q

Most successful treatment for stroke

A

-plasminogen activator-dissolves blood clots in the brain

118
Q

Alzheimer’s disease

A
  • progressive degenerative disease of the brain that results in dementia (mental deterioration)
  • beta-amayloid peptide deposits and neurofibrillary tangles appear
  • marked by a deficit of ACh
119
Q

Parkinson’s disease

A
  • usually strikes people in their 50’s or 60’s
  • degeneration of dopamine-releasing neurons of the substantia nigra
  • as neurons deteriorate, the dopamine-deprived basal nuclei they target become overactive
  • people have tremors, forward-bend walking posture, shuffling gate, and stiff facial expression–they are slow in initiating and executing movement
120
Q

Huntington’s disease

A
  • fatal hereditary disorder that strikes during middle age
  • mutant huntingtin protein accumulates in brain cells and the tissue dies which leads to a massive degeneration of the basal nuclei and later the cerebral cortex
  • initial symptoms are wild, jerky movements called chorea (‘dance”)
  • later, mental deterioration occurs
  • it is progressive and usually fatal w/in 15 years
121
Q

Spinal cord

A
  • extends from the foramen magnum to the 1st or 2nd lumbar vertebra
  • provides 2-way conduction pathway to and from the brain
  • spinal reflexes are initiated and completed at the spinal cord level
122
Q

What is the spinal cord protected by?

A

-bone, meninges, and CSF

123
Q

Lumbar puncture

A

-since the dural and arachnoid membranes extend to the level of S2 but the spinal cord ends b/t L1 and L2, the subarachnoid spaces w/in the meningeal sac inferior to this point provides an ideal spot for removing CSF w/o risking damaging the spinal cord

124
Q

Conus medullaris

A

-a tapering cone-shaped structure where the spinal cord ends

125
Q

Filum terminale

A

-fibrous extension of the conus that extends infereiorly to the coccyx where it anchors the spinal cord so it isn’t jolted by body movements

126
Q

Denticulate ligaments

A

-saw-toothed shelves of pia mater that secure the spinal cord to the tough dura mater meinx throughout it’s length

127
Q

Cauda equina

A

-collection of nerve roots at the inferior end of teh vertebral canal

128
Q

How many pairs of spinal nerves are there?

A

31

129
Q

Dorsal horns

A
  • posterior
  • entirely interneurons
  • afferent fibers carrying impulses from peripheral sensory receptors form dorsal roots that fan out as dorsal rootlets before entering the spinal cord
130
Q

Ventral horns

A
  • anterior
  • some interneurons but mainly cell bodies of somatic motor neurons that send axons to the skeletal muscles via ventral rootlets that fuse to become ventral roots
131
Q

Lateral horns

A
  • consist mostly of cell bodies of autonomic motor neurons that serve visceral organs
  • axons leave cord via ventral root along w/ those of the somatic motor neurons
  • *because ventral roots contain somatic and autonomic efferent fibers, they serve both motor divisions of the PNS
132
Q

Dorsal root ganglia

A

-cell bodies of associated sensory neurons are found here

133
Q

Spinal nerve formation

A

-laterally from the dorsal and ventral roots

134
Q

Ascending fibers of white matter

A
  • go up to higher centers

- sensory inputs

135
Q

Descending fibers of white matter

A
  • go down the cord from the brain or within the cord to lower levels
  • motor outputs
136
Q

Transverse fivers of white matter

A
  • go across from one side of the cord to the other

- commissural fibers

137
Q

Funiculi

A
  • dorsal, lateral and ventral

- each contains several fiber tracts and each tract is made of axons w/ similar destinations and functions

138
Q

Ascending pathways to the brain

A

-conduct sensory impulses upward through chains of 3 successive neurons to various areas of teh brain

139
Q

First-order neurons

A
  • cells bodies reside in ganglion
  • conduct impulses from cutaneous receptors of skin and from proprioceptors to the spinal cord or brain stem where they synapse w/ second order neurons
  • impulses from facial area are transmitted by cranial nerves
  • spinal nerves conduct somatic sensory impulses from rest of body to CNS
140
Q

Second-order neurons

A
  • reside in dorsal horn or in medullary nuclei

- transmit impulses to thalamus or to cerebellum where they synapse

141
Q

Third-order neurons

A
  • cell bodies in the thalamus
  • relay impulses to somatosensory cortex of the cerebrum
  • there are none in the cerebellum
142
Q

Dorsal-column-medial lemniscal

A
  • transmission of inputs from a single type of sensory receptor that can be localized precisely on the body surface
    ex: discriminative touch and vibrations
143
Q

Spinothalamic pathways

A
  • receive input from many types of snesory receptors and make multiple synapses in the brain stem
  • primarily transmit impulses for pain and temperature but also coarse touch and pressure
144
Q

Somatosensory information travels along which three ascending pathways?

A
  • dorsal column-medial lemniscal
  • spinothalamic pathways
  • spinocerebellar pathway
145
Q

Spinocerebellar pathways

A
  • convey info about muscle or tendon stretch to the cerebellum which uses this info to coordinate skeletal muscle acitivity
  • these DON’T decussate or they cross over twice, undoing the decussation
146
Q

Descending pathways and tracts

A
  • deliver efferent impulses from the brain to the spinal cord
  • two groups: direct and indirect pathways
147
Q

Upper motor neurons of the descending pathway

A

-pyramidal cells of the motor cortex and neurons of subcortical motor nuclei

148
Q

Lower motor neurons of the descending pathway

A
  • ventral horn motor neurons

- directly innervate skeletal muscles

149
Q

Direct pathway of descending pathway

A
  • originate with pyramidal neurons in the precentral gyri
  • send impulses through brain stem via the large pyramidal tracts
  • axons descend w/o synapsing form the pyramidal neurons to the spinal cord
  • they synapse with interneurons or ventral horn motor neurons
  • stimulation of ventral horn neurons activates skeletal muscles
  • regulates fast and fine movements (writing)
150
Q

Indirect pathway of descending pathway

A
  • include brain stem motor nuclei and all motor pathways except pyramidal
  • regulate axial muscles that maintain balance and posture, muscles controlling coarse limb movements, and head, neck and eye movements that follow objects
151
Q

Flaccid paralysis

A
  • damage to the ventral root or ventral horn cells

- the muscles they serve atrophy

152
Q

Spastic paralysis

A
  • only upper motor neurons of the primary motor cortex are damaged
  • spinal motor neurons remain intact and spinal reflex activity continues to stimulate the muscles irregularly
  • muscles remain healthy longer but are no longer under voluntary control
153
Q

Paraplegia

A
  • between T1 and L1

- both lower limbs affected

154
Q

Quadraplegia

A
  • injury to the cervical region

- all 4 limbs affected

155
Q

Hemiplegia

A
  • paralysis of one side of the body

- usually reflects brain injury rather than spinal cord injury

156
Q

Spinal shock

A
  • period of functional loss that follows spinal injury
  • depresses all reflex activity next to the lesion site
  • bowel and bladder reflexes stop
  • blood pressure falls
  • muscles below injury are paralyzed and insensitive
  • neural function usually returns w/in a few hours–if it doesn’t return within 48 hours it is usually permanent paralysis
157
Q

Poliomyelitis

A
  • poliovirus–enters body in feces-contaminated water and destroys ventral horn motor neurons
  • paralysis develops and muscles atrophy
158
Q

Amyotrophic Lateral Sclerosis (ALS) aka Lou Gehrig’s disease

A
  • neuromuscular condition that progressively destroys ventral horn motor neurons and fibers of the pyramidal tracts
  • lose ability to speak, swallow, and breathe
  • death w/in 5 years
159
Q

Diagnostic procedures used to assess neurological condition and function

A
  • reflex testing
  • cerebral angiography
  • CT scans
  • MRI scans
  • PET scans

Nervous System (2 decks)

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