Chapter 13 Flashcards
(86 cards)
1
Q
Meninges definition
A
Three protective, connective tissue coverings that encircle the spinal cord and brain
2
Q
What are the three meninges?
A
- Dura mater
- Arachnoid mater
- Pia mater
3
Q
Dura mater
A
- Most superficial
- Thick strong layer composed of dense irregular connective tissue
- Forms a sack from the foramen magnum in the occipital bone, to meningeal duramater of the brain, to the second sacral vertebrae
4
Q
Arachnoid Mater
A
- The middle layer
- Thin, avascular, made up of cells and thin loosely arranged collagen and elastic fibres
- Deep to the duramater and his continuous through the foreman magnum with the arachnoid Mater of the brain
- between the duramater and the arachnoid Mater is a thin subdural space which contains interstitial fluid
5
Q
Pia matter
A
- Innermost meninges
- Send transparent connective tissue layer that adheres to the surface of the spinal cord and brain
- Consists of thin squamous to cuboidal cells within interlacing bundles of collagen fibres and some fine elastic fibres
- Vascular supplies the nutrients and oxygen to the spinal cord
- Suspends the spinal cord in the middle of its dural sheath
6
Q
Subdural space
A
Located between the duramater and the arachnoid Mater and contains interstitial fluid
7
Q
Denticulate ligaments
A
- Thickening of the pia Mater
- they project laterally and fuse with arachnoid Mater an inner surface of the duramater between the anterior and posterior nerve root of spinal nerves on either side
- protect the spinal cord against sudden displacement that could result in shock
8
Q
Subarachnoid space
A
Between arachnoid Mater and pia matter and contains shock absorbing cerebrospinal fluid
9
Q
Cervical enlargement
A
- Superior enlargement
- Extends from the fourth cervical vertebrae C4 to the first thoracic vertebrae T1
- Nerves to and from the upper limbs arise from the cervical enlargement
10
Q
Lumbar enlargement
A
- Inferior enlargement
- Extends from the ninth to the 12th thoracic vertebrae
- Nurse to and from the lower limbs arise from the lumbar enlargement
11
Q
Conus medullaris
A
- The spinal cord terminates as a tapering conical structure
- Ends at the first and second lumbar vertebrae
12
Q
Filum terminate
A
- Arises from the cornice medullaris
- Extension of the pia matter, fuses with the arachnoid and Dura Mater
- Anchors the spinal cord to the coccyx
13
Q
Spinal nerves
A
The paths of communication between the spinal cord and specific regions of the body
14
Q
How many pairs of spinal nerves are there?
A
31
15
Q
Where do the 31 pairs of spinal nerves emerge?
A
- Eight pairs of cervical nerves
- 12 pairs of thoracic nerves
- Five pairs of lumbar nerves
- Five pairs of sacral nerves
- 1 pair of coccygeal nerves
16
Q
Roots
A
Two bundles of axons that connect each spinal nerve to a segment of the cord by even smaller bundles of axons called rootlets
17
Q
Rootlets
A
Even smaller bundles of axons
18
Q
Posterior root (dorsal)
A
Contain only sensory axons which conduct nerve impulses from sensory receptors in the skin, muscles, and internal organs into the central nervous system
19
Q
Posterior (dorsal) root ganglion
A
Contains the cell bodies of sensory neurons
20
Q
Anterior (ventral) root
A
Contain axons of motor neurons which conduct nerve impulses from the CNS to effectors
21
Q
Cauda equina
A
Roots of lower spinal nerves that angle inferiority alongside the filum terminale in the vertebral canal like wisps of hair
22
Q
White matter of spinal cord
A
- Surrounds grey matter
- Consist mostly of bundles of myelinated axons and neurons
23
Q
What are the two grooves that puncture the white matter of the spinal cord?
A
- Anterior median fissure
- Posterior median sulcus
24
Q
Gray commisure
A
Forms the crossbar of the H (gray matters shape in the spinal chord)
25
Central canal
Small space in gray commisure that extends the entire length of the spinal cord and is filled with cerebrospinal fluid
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Anterior (ventral) white commisure
Anterior to gray commisure, connects the white matter of the right and left sides of the spinal cord
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Nuclei
Clusters of neuronal cells bodies that form functional groups in the gray matter of the spinal cord and brain
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Sensory nuclei
Receive input from receptors via sensory neurons
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Motor nuclei
Provide output to effector tissues via motor neurons
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Horns
How gray matter is subdivided on each side of the spinal cord
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Posterior (dorsal) gray horns
Contain axons of incoming sensory neurons as well as cell bodies and axons of interneurons
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Three regions of spinal white matter?
1. Anterior (ventral) white columns
2. Posterior (dorsal) white columns
3. Lateral white columns
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Tracts
Bundles of axons in CNS, can extend up or down spinal tract
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Nerves
Bundles of axons in PNS
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Sensory ( ascending) tracts
Consists of axons that conduct nerve impulses towards the brain
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Motor (descending) tracts
Tracks consisting of hacks on security nerve impulses from the brain
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Sensory input and motor output are processed how?
1. Sensory receptors detect a sensory stimulus
2. Sensory neurons convey the sensory input in the form of nerve impulses along the axons which extend from the sensory receptors into the spinal nerve and then into the posterior route from the posterior route axons of the sensory neurons may process along three possible paths
3. Axons of sensory neurons may extend into the white matter of the spinal cord and descend to the brain as part of the sensory tract
4. Axons of sensory neurons may enter the posterior gray horn and synapse with interneurons whose axons extend into the white matter of the spinal cord and then ascend to the brain as part of a sensory tract
5. Axons of sensory neurons may enter the posterior gray horn and synapse with interneurons that intern synapse with somatic neurons that are involved in spinal motor reflex pathways
6. Axons from higher brain centres form motor tracks that discend from the brain into the white matter of the spinal cord there they synapse with the somatic motor neurons either directly or indirectly by first synapsing with interneurons that intern snapse with somatic motor neurons
7. When activated, somatic motor neurons convey motor output in the form of nerve impulses along their axons, which sequentially pass through anterior gray horn and anterior root to enter the spinal nerve
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Spinal nerves
Connect the CNS to sensory receptors, muscles, and glands in all parts of the body
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Mixed nerve
When the posterior root contains sensory axons and the anterior root contains motor axons the spinal nerve is classified as a mixed nerve
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Endoneurium
Individual axons within a nerve, myelinated or unmyelinated, are wrapped in endoneurium, The inner most layer consist of mesh of collagen fibres fibroblasts and macrophages
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Perineum
- Middle layer
- Thicker layer of connective tissue
- Consists of up to 15 layers of fibroblast within a network of collagen fibres
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Epineurium
- Outer most layer of entire nerve
- Consists of fibroblast and take collagen fibres
- Extensions also fill the spaces between fascicles
- Duramater of the spinal meninges fuses with the epineurium as the nerve passes through the intravertebral foramen
- vascular
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Rami
The branches a spinal nerve divides into after passing through its intravertebral foramen
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Posterior ramus
Serves the deep muscles and skin of the posterior surface of the trunk
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Anterior ramus
Serves the muscles and structures of the upper and lower limbs and the skin of the lateral and anterior surfaces of the trunk
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Meningeal branch
Re-enters the vertebral cavity through the intravertebral foramen and supplies the vertebrae, vertebral ligaments, blood vessels of the spinal cord, and meninges
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Rami communicates
components of the autonomic nervous system
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Plexus
Networks on both the left and right side of the body joining various numbers of axons from anterior Rami of adjacent nerves other than in the thoracic nerve T2 to T12
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What are the principal plexuses
1. Cervical plexus
2. Brachial plexus
3. Lumbar plexus
4. Sacral plexus
5. Smaller coccygeal plexus
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Intercostal nerves or thoracic nerves
The anterior rami of spinal nerves T2 to T12 do not enter into the formation of plexis and are known as this
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Dermatome
The area of the skin that provides sensory input to the CNS via one pair of spinal nerves or the trigeminal five nerve is called a dermatome
52
Cervical plexus
- Is formed by the roots of the first four cervical nerves with contributions from C5
- one on each side of the neck along side the first four cervical vertebrae
- supplies the skin and muscles of the head neck and superior part of the shoulders and chest
53
Brachial plexus
1. Roots of spinal nerve C5 to see 8NT one form the brachial plexus extend inferiorly and laterally on either side of the last four cervical and first thoracic vertebrae
2. Pass is above the first rib posterior to the clavicle and then enters the Scilla
3. Brachial plexus provides almost the entire nerve supply of the shoulders and upper limbs
54
Lumbar plexus
1. The roots of spinal nerves L1 to L4 form the lumbar plexus unlike the brachial plexus there is minimal intermingling of fibres in the lumbar plexus
2. Supplies the Antero lateral abdominal wall, external genitals, and part of the lower limbs
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Sacral plexus
1. The roots of spinal nerves L4 to L5 and S1 to ask for form the sacral plexus
2. Situated largely anterior to the sacrum
3. Supplies the buttocks, perineum, and lower limbs
4. The largest nerve in the body the sciatic nerve arises from the sacral plexus
56
What are the two principal functions of the spinal cord in maintaining homeostasis?
1. Nerve impulse propagation
2. Integration of information
57
White matter tracks in the spinal cord or highway is for what?
Nerve impulse propagation
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What does gray matter do in the spinal cord?
Receives and integrates incoming and outgoing information
59
Nerve impulses from sensory receptors propagate up the spinal cord to the brain along what two main routes?
1. Spinothalamic tract
2. Posterior column
60
Spinothalamic tract
Conveys nerve impulses for conveying pain, tempature, itch, and tickle
61
Posterior colum consists of what two tracts and what they convey?
1. Gracile fasciculus
2. Cuneate fasciculous
Nerve impulses for touch, pressure, vibration, and conscious proprioception ( awareness of positions and movements of muscles, tendons, and joints)
62
How does motor output travel to skeletal muscles in descending pathways?
Direct and indirect pathways
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What are the direct motor pathways?
1. Lateral corticospinal
2. Anterior corticospinal
3. Corticobulbar tracts
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How do the direct motor pathways convey nerve impulses that originate in the cerebral cortex?
Through voluntary movements of skeletal muscles
65
What are the indirect motor pathways (extrapyramidal pathways)?
1. Rubrospinal
2. Tectospinal
3. Vestibulospinal
4. Lateral reticulospinal
5. Medial reticulospinal
66
What do the indirect motor pathways convey?
1. Nerve impulses from brainstem to cause autonomic movements
2. help coordinate body movements with visual stimuli
3. Maintain skeletal muscle tone
4. Sustain contraction of postural muscles
5. Major role in equilibrium by regulating muscle tone in response to movements of the head
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Reflex
Fast, involuntary, unplanned sequence of actions that occurs in response to a particular stimulus
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Spinal reflex
When integration takes place in the spinal cord gray matter
Example: knee jerk
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Cranial reflex
Occurs in brainstem
Example: tracking movement of eyes as you read
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Somatic reflexes
Contraction of skeletal muscle
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Autonomic reflexes (visceral)
Not consciously perceived, smooth muscle, cardiac muscle, and glands
Example: heart rate, digestion, urination, defecation
72
What are the five reflex arcs?
1. Sensory receptors
2. Sensory neuron
3. Integrating center
4. Motor neuron
5. Effector
73
Sensory receptors
Distal end of sensory neuron (dendrite)
Responds to internal or external environment stimulus
Produces a graded potential called generator potential
74
Sensory neuron
Nerve impulses propagate from sensory receptor along the axon of the sensory neuron to axon terminal, in gray matter of spinal cord and brain stem, relay neurons send nerve impulses to the area of the brain that allows conscious awareness that a reflex occured
75
Integrating center
One or more regions of gray matter within the CNS acts as an integrating center. Simple reflex one synapse between sensory and motor neuron some are more complicated
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Motor neuron
Impulses triggered by the integrating centre propagate out of the CNS along a motor neuron to the part of the body that will respond
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Effector
The part of the body that responds to the motor nerve impulse such as a muscle or gland is the effector it’s action is a reflex
78
Stretch reflex
Causes contraction of a skeletal muscle in response to stretching of the muscle
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Ipsilateral reflex
Sensory nerve impulses enter the spinal cord on the same side the motor nerve impulse leaves monosynaptic reflexs are always ipsilateral
80
Muscle tone
How vigourously a muscle spindle response to tone the small degree of contraction while the muscle is at rest prevents overstretching
81
Reciprocal innervation
Stretched muscles contract and antagonistic muscles relax simultaneously.
prevents conflict between opposing muscles and is vital to coordinating body movement
82
Tendon reflex
Feedback mechanism to control muscle tension causes muscle relaxation before muscle foreskin cause Terrie always ipsilateral
83
Tendon organs
Detecting respond to change in muscle tension caused by passive stretch or muscle contraction
84
Flexor (withdrawal) reflex
Painful stimulus
85
Intersegmental reflex arc
Nerve impulses from one sensory neuron ascend and descend in the spinal cord and activate interneurons in several segments of the spinal cord
86
Crossed extensor reflex
Helps maintain balance
