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Anatomy (MPAS) > Lecture 4: Nervous system III > Flashcards

Lecture 4: Nervous system III Flashcards

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1
Q

How are spinal nerves named?

A

According to their association with vertebral column

8 pairs of cervical, 12 thoracic, 5 lumbar, 5 sacral

See figure

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2
Q

How is each nerve attached to the spinal cord?

A

By a ventral root and a dorsal root

See figure

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3
Q

Where does brain receive sensory info from?

A

Somatosensory systems

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4
Q

What happens after brain receives sensory info?

A

Receptors convert stimuli into action potentials that travel down the axons that enter the CNS

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5
Q

What root of the spinal nerves does sensory info enter the CNS?

A

Dorsal roots

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6
Q

What are afferent signals in the CNS used for?

A

In reflexes

Or signals may be relayed via neurons in spinal cord or brainstem to higher centres

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7
Q

What roots of spinal nerves carry motor impulses?

A

Ventral

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8
Q

What kind of stimuli is sensory system capable of detecting?

A

Mechanical stimuli (mechanoreceptors)

Pain (nociceptors) and

Temperature (thermoreceptors)

Mechanoreceptors (many types)

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9
Q

Types of mechanoreceptors

A

Neuromuscular spindles - receptors for stretch, respond to change in length (basis for stretch reflex i.e. Knee jerk)

Golgi Tendon organs - stimulated by tension in tendons (protection against damage from excessive stretch)

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10
Q

Where are the cell bodies of the sensory neurons of the PNS?

A

Dorsal root ganglia

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11
Q

Where do the processes of the sensory cells project?

A

One process of the sensory cell projects (in the spinal nerve) to the periphery where it ends in a sensory receptor

one process projects to CNS (spinal cord).

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12
Q

Afferent signal transduction

A

Signal (converted to action potential by receptor) travels from receptor to CNS

See figure

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13
Q

What root contains efferent fibres?

A

Anterior Root = Ventral Root = Motor Root

action potentials are leaving the cord

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14
Q

What do motor neurons innervate?

A

cell bodies are in the ventral horn of the cord

innervate skeletal muscle (via motor fibres)

cause contractions of the muscle (LMNs)

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15
Q

What do descending fibres from the cerebral cortex and brainstem activate?

A

Motor neurons

produce voluntary (and reflexive) movement

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16
Q

Where do the ventral and dorsal roots pass through?

A

Intervertebral foramina

They then join together and form a short spinal nerve (becomes a mixed nerve)

Supply myotomes and dermatomes

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17
Q

What is a myotome?

A

refers to muscles innervated by the motor fibres of a spinal nerve

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18
Q

What is a dermatome?

A

area of skin innervated by the sensory fibres of a spinal nerve

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19
Q

What would peripheral nerve injury cause (motor changes)?

A

flaccid paralysis followed by muscle

degeneration

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20
Q

What would peripheral nerve injury cause (sensory changes)?

A

loss of cutaneous sensibility (pinprick test)

However: the injury of one spinal cord segment
or spinal nerve rarely causes the loss of function of a whole muscle or loss of sensitivity in a dermatome

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21
Q

What does spinal nerve or root compression cause?

A

Prolapse of the nucleus pulposus

Causes herniation

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22
Q

Postero-lateral disc herniation

A

Most common herniation

Causes lower back pain, pain in buttock, thigh, leg

Prolapse of the L4/L5 disc causes compression of the L5 root

see figure

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23
Q

Postero-medial disc herniation

A

see figure

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24
Q

Where does the spinal cord extend from?

A

From foramen magnum to L1-L2

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25
What structure marks the end of the spinal cord?
Conus medullaris (between L1 and L2) See figure
26
What tethers the cord to the end of the dural sac
The filum terminale Extension of the pia
27
What is below the conus medullaris?
Cauda equine
28
What are the two enlargements of the spinal cord
Cervical and lumbosacral
29
Where is cervial enlargement? What does it innervate?
C4-T1 of sc Arm
30
Where is lumbosacral enlargement? What does it innervate?
L2-S3 of sc Innervation of leg
31
Root length in cervical and lumbosacral region
Cervical - short and horizontal Lumbosacral - cauda equina (horses tail)
32
What is caudal equina contained within?
Subarachnoid space
33
Internal composition of spinal cord
White matter (ascending and descending axons) Butterfly shapedgray matter See figure
34
Horns of grey matter
Dorsal horn ventral horn See figure
35
Function of dorsal horn?
Sensory processes and relays sensory information to the brain
36
Through which root does sensory info enter through?
Dorsal root
37
Where are the cell bodies of sensory neurons located?
Dorsal root ganglion
38
Function of ventral horn
Motor Contains large motor neurons projecting into muscle (via ventral root)
39
Another word for motor neurons
"motor efferents"
40
Composition of white matter of spinal cord
nerve fibres, neuroglia, & blood vessels (not neuronal cell bodies)
41
Why is white matter white?
high fat content (myelin)
42
Where do the fibres of the white matter arise from?
Cell bodies located in... Brain (descending from cerebrum and brainstem) Spinal cord (ascending from grey matter of spinal cord) Periphery (Ascending from dorsal root ganglia) (see figure)
43
How are axons arranged in white matter of spinal cord?
Arranged in tracts/fasciculi/bundles that have similar origin, termination and function (sensory or motor)
44
Number of fibres in white matter relative to cord location
White matter decreases as you move down the cord See figure
45
Composition of grey matter of spinal cord
Neuronal cell bodies Neuroglia
46
Dorsal horn of grey matter of spinal cord
Receives sensory input via dorsal root. Site of numerous interneurons and projection neurons (project axons to brain)
47
Ventral horn of grey matter of spinal cord
Motor fn Sends projections to skeletal muscle via ventral root (see figure)
48
What is spinal cord contained in?
Meninges: dura/ arachnoid sac from foramen magnum to 2nd sacral vert. (S2) Arachnoid is attached to dura, and is continuous with dura of the brain.
49
Where does conus medullaris end?
Between L1 and L2 vertebrae
50
Is dura attached to bone of vertebrae?
No
51
Epidural space of spinal cord
Between dura and vertebrae Contains connective tissue, fat, veins
52
Space between arachnoid and pia of spinal cord
Filled with CSF subarachnoid space
53
What is lumbar cistern?
Space between L1-2 and S2 vertebrae Contains cauda equina
54
What is lumbar cistern used for?
Access to CSF without damaging cord Spinal anasthesia
55
Pia matter of spinal cord
Innermost layer attached to spinal cord
56
What is the denticulate ligament?
Lateral projections of pia matter of spinal cord Suspend cord with dural sac (see figure)
57
What is the somatic nervous system?
Functional entity of the peripheral nervous system Includes sensory component and a tomato-motor component
58
What does sensory component of somatic nervous system detect?
Pain, temperature, touch, vibration, proprioception Sensory fibres carry information to the CNS
59
Where are the cell bodies of the sensory components of the somatic nervous system?
1 neutron from receptor to CNS Cell body is in dorsal root ganglion
60
What does somato-motor component of somatic nervous system do?
Responsible for contraction of voluntary (skeletal) muscle (under voluntary control of the conscious mind, as well as reflexes of skeletal muscle). See figure
61
Where are the cell bodies of the somato-motor components of the somatic nervous system? Where do the axons exit?
Cell bodies of neurons innervating muscle are in ventral horn of spinal cord Axons exit cord via ventral root and contact muscle directly (1 neuron from cord to muscle) See figure
62
Systems regulated by ANS
1. Cardiovascular System 2. Respiratory System 3. Reproductive System 4. Urinary System 5. Gastrointestinal System
63
Target tissue of ANS
i. Cardiac muscle ii. Smooth muscle (within the walls of blood vessels, airways, G.I. tract etc.), and iii. Glands (e.g., salivary, sweat, adrenal medulla)
64
Conscious control of ANS?
In general, little conscious control (although there can be conscious influences on ANS activity)
65
Neurons of the afferent component of the autonomic nervous system
Sensory neurons that project from the target | tissue to the CNS via cranial and spinal nerves
66
Neurons of the efferent component of the autonomic nervous system
A ‘2-neuron chain’ that connects the CNS to the target tissue The connection between the 2 neurons is in an autonomic ganglion See figure
67
What is the pre-ganglionic neuron? Where is it located? Where does it project?
Cell body of 1st neuron is in the CNS projects to a ganglion via a myelinated axon
68
What is the ganglion in the efferent portion of the autonomic nervous system? Where does it project to?
Site of connection between the pre- and post-ganglionic neuron Houses the cell body of the post-ganglionic neuron projects to the target tissue via a non-myelinated axon see figure
69
2 divisions of autonomic nervous system (ANS)
1. Sympathetic (Thoracolumbar) Nervous System (“Fight or Flight” response) 2. Parasympathetic (Craniosacral) Nervous System (“Rest & Digest”) Target tissue can be innervated by both, but this is not always the case
70
Sympathetic nervous system functions
Activated during ‘fight or flight’ response: Increases heart rate and blood pressure Increases diameter of airways Inhibits salivary glands and decreases G.I. activity (directs blood away from G.I. tract) Stimulates adrenal gland 0 Activates sweat glands Dilates pupil
71
Where are the pre-ganglionic cell bodies of the sympathetic (thoracolumbar) NS located?
Located in thoracic and lumbar segments of spinal cord (T1 to L2) Axons exit spinal cord via ventral root and project to sympathetic ganglia
72
What are sympathetic ganglia for the sympathetic (thoracolumbar) NS?
sympathetic chain: blood vessels, sweat glands, head and thorax (heart and lungs) pre-vertebral ganglia: Abdominal and pelvic viscera
73
Where are the pre-ganglionic cell bodies of the parasympathetic (craniosacral) NS located?
brainstem: cell bodies of preganglionics are in specific cranial nerve nuclei and send their axons within the cranial nerves. sacral levels of the spinal cord: The axons of these neurons exit cord via ventral root and travel within sacral nerves.
74
Where are parasympathetic ganglia located?
Near the target tissue (axons of post-ganglionics are short)
75
What do Cranial nerves in parasympathetic carniosacral NS innervate?
eye, glands of the head, viscera of thorax (heart & lungs) and abdomen (stomach, intestines, liver)
76
What do sacral nerves in parasympathetic carniosacral NS innervate?
pelvic viscera (lower colon, bladder, and reproductive organs)
77
Parasympathetic NS functions
Dominant when at rest (‘Rest & Digest’) : Decreases heart rate and blood pressure Decreases diameter of airways Stimulates salivary glands and increases G.I. activity Constricts pupil
78
sympathetic vs parasympathetic
Generally the 2 branches (symp. & parasymp.) are functionally antagonistic If both innervate a muscle, 1 branch will cause contraction, while the other relaxation Together they determine the overall activity of a gland or contractile activity of a smooth muscle
79
Innervation of smooth muscle of blood vessels and sweat glands
only innervated by the Sympathetic NS
80
Which functions require coordination between SNS and PSNS?
Bowel and bladder function (defecation and micturition) Sexual function (erection and ejaculation)
81
What is the major regulator of the ANS?
Hypothalamus (part of diencephalon) Hypothalamus projects to brainstem and down the spinal cord and regulates activity of the preganglionics of SNS and PNS

Anatomy (MPAS) (22 decks)

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