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Human Anatomy (EPHE 141) > Nervous System > Flashcards

Nervous System Flashcards

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1
Q

What are the two main divisions of the nervous system and what do each include?

A

1) Central nervous system - includes all nervous tissue associated with the brain and spinal cord
2) Peripheral nervous system - includes all neural tissue outside the CNS

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2
Q

What is the CNS responsible for?

A

integrating, processing, coordinating sensory input and motor output. Also higher functions like intelligence, memory, learning, and emotion.

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3
Q

What are the two main divisions of the PNS (think about the direction of the flow of information)?

A

Afferent: somatic sensory, visceral sensory, and special sensory fibres carry information about some aspect of the environment to the CNS

Efferent: somatic and autonomic fibres carry motor information to elicit some response.

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4
Q

What are the two main divisions of the efferent division of the PNS and what are they responsible for?

A

1) Somatic nervous system: controls skeletal muscle contraction
2) Autonomic nervous system: controls activities of internal organs (via smooth muscle, cardiac muscle, or glands)

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5
Q

What are the two cell types of the nervous system and what are the main difference between them?

A

1) Neuron
2) Neuroglia

Main difference is that the neurons are excitable while the neuroglia are not. Glia also retain the ability to undergo cell division while neurons do not.

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6
Q

What is the difference between gray matter and white matter?

A

Gray matter is neural tissue made of the cell bodies of neurons while white matter is neural tissue made of myelinated axons

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7
Q

What are the types of neuroglia in the CNS and what are their roles?

A

1) Oligodendrocytes: myelinate CNS axons and provide structural framework
2) Astrocytes: maintain BBB, provide structural support, regulate ion, nutrient, and dissolved gas concentrations, absorb and recycle NTs, and form scar tissue after injury
3) Microglia: remove cell debris, waste, and pathogens by phagocytosis
4) Ependymal cells: line ventricles and central canal, assist in producing, circulating, and monitoring CSF

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8
Q

What are the types of neuroglia in the PNS and what are their roles?

A

1) Satellite cells: surround neuron cell bodies in ganglia and regulate dissolved gas, nutrient, and NT levels in ganglia
2) Schwann cells: surround and myelinate all axons in the PNS, and participate in repair process after injury

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9
Q

What are the clusters of cell bodies in the PNS called?

A

Ganglia

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10
Q

What are the four structural classifications of neurons?

A

1) anaxonic - no anatomical clues to differentiate axons and dendrites. Found in the CNS and special sense organs
2) bipolar - dendrites fuse to form one long dendrite and the cell body lies between the dendrite and a single long axon. Found in special sense organs for relaying sight, smell, and hearing.
3) pseudounipolar - continuous dendritic and axonal processes with the cell body lying off to the side. Found in sensory neurons of the PNS.
4) multipolar - several dendrites and a single axon. Most common in the CNS (eg. motor neurons)

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11
Q

What are the functional classifications of neurons?

A

1) Sensory - collect information concerning the external or internal environment
2) Motor - stimulate or modify the activity of a peripheral tissue, organ, or organ system
3) interneuron - analysis of sensory input and coordination of motor output

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12
Q

What is a neuronal pool?

A

A group of interconnected neurons with specific functions

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13
Q

What is a neural circuit?

A

The specific pattern of connectivity found within a neuronal pool.

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14
Q

What are the two major types of synapses found in the nervous system?

A

1) Chemical/vesicular synapse

2) Electrical/non-vesicular synapse

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15
Q

List the sequence of events that occur at a chemical synapse:

A

1) Action potential arrives at presynaptic membrane
2) Neurotransmitter is released from axon vesicles
3) NT diffuses across synapse
4) NT binds to postsynaptic membrane
5) Binding causes a change in permeability of the post synaptic membrane to one or more ion species
6) Change in permeability results in an action potential at the next neuron

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16
Q

List the sequence of events at an electrical synapse:

A

1) presynaptic membrane of one neuron is tightly bound to the postsynaptic membrane of the next neuron
2) this binding permits the passage of ions from one neuron to the next

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17
Q

What is another name for Schwann cells?

A

Neurolemmocytes

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18
Q

What is the primary purpose of myelin?

A

Increase the conduction speed of an action potential or neural impulse.

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19
Q

What type of nervous tissue are most brain cancers derived from and why?

A

Most brain tumours arise due to cell division and neuroglia are the only nervous tissue capable of undergoing cell division and regeneration.

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20
Q

What is a reflex? What is a reflex arc?

A
  • an immediate, involuntary motor response

- the progression from sensory receptor to peripheral effector

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21
Q

What are the two main ways we classify reflexes?

A

1) monosynaptic: involves a single segment of the spinal cord, minimal delay between stimulus and response, and presents the same every time
2) polysynaptic: involves integration of input from several spinal segments, longer delays between stimulus and response.

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22
Q

Describe what takes place in the stretch reflex:

A

a monosynaptic reflex arc:

  • proprioceptors in muscle spindles send afferent information to the dorsal root of the spinal cord
  • afferent fibre conducts through posterior gray horn
  • afferent fibre synapses with efferent motor neuron at anterior gray horn
  • motor neuron projects to muscle fibres to stimulate a contraction of the appropriate muscle
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23
Q

Describe what takes place in the withdrawal reflex:

A

a polysynaptic reflex arc:

  • nociceptors or thermoreceptors are activated by a stimulus
  • sensory neuron sends information to the spinal cord where it synapses with an interneuron
  • this interneuron can be excitatory or inhibitory; if it is inhibitory, it usually projects to another interneuron to inhibit it which disinhibits the motor neuron. If it is excitatory, it projects to another interneuron to excite it to excite/stimulate the motor neuron on one side and inhibit the antagonists
  • the excited motor neuron stimulates the muscle fibres to contract on the side of the response
  • the inhibited motor neuron generally projects to an antagonist - no activation of the antagonist
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24
Q

When do anterior horns increase in size?

A

When the number of muscles innervated by a spinal segment increases

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25
What is the difference between a tract and a column of white matter?
Tract: bundles of CNS axons that share a common origin and destination Column: several tracts that form an anatomically distinct mass in the spinal cord
26
What is the shallow longitudinal groove along the dorsal surface of the spinal cord called? What is the deep crease along the ventral surface called?
- posterior median sulcus | - anterior median fissure
27
What are the two major enlargements of the spinal cord?
The cervical enlargement and the lumbosacral enlargement. These areas have a larger amount of gray matter than other areas of the spinal cord due to the presence of interneurons.
28
What is the name of the slender, fibrous tissue that extends from the end of the spinal cord to the coccyx?
- filum terminale
29
What is the function of the filum terminale?
- provide longitudinal support to the spinal cord as a component of the coccygeal ligament
30
What is the cauda equina?
Composed of the filum terminale and the long dorsal and ventrak riits that extend caudally
31
What are the main roles of the spinal meninges?
1) provide protection 2) physical stability 3) shock absorption
32
The spinal meninges and the cranial meninges are continuous at what location on the skull?
At the foramen magnum
33
What tissue type makes up the three layers of the spinal meninges?
Dura: dense, irregular connective tissue covered by simple squamous epithelium Arachnoid: simple squamous epithelium Pia: elastic and collagen fibres
34
What structure of the spinal cord contains axons crossing from one side to the other?
Gray commissures
35
How are spinal nerves named?
Cervical: for the vertebra directly following them Thoracic and Lumbar: for the vertebra immediately preceding them
36
During a spinal tap, cerebrospinal fluid is drawn from the subarachnoid space at the level of ______. Why?
- Lower lumar vertebra (L2 and lower) - because these vertebra no longer enclose the spinal cord but still contain CSF so there is minimal risk of long term injury.
37
Why are the dorsal rami thinner than the ventral rami?
Dorsal rami only innervate the posterior trunk while the ventral rami innervate the lateral and anterior trunk, as well as the entirety of the limbs
38
Name the four major nerve plexuses:
1) Cervical: from ventral rami of nerves C1-C4 and some from C5 and innervates the head, neck, and chest 2) Brachial: from ventral rami of nerves C5-T1 and innervates the pectoral girdle and upper limbs 3) Lumbar: from ventral rami of nerves T12-L5 and innervates the pelvic girdle and lower limbs 4) Sacral: from ventral rami of nerves L4-S4 and innervates the pelvic girdle and lower limbs
39
List the 5 potential routes that sensory information can take to reach the spinal cord:
1) Dorsal ramus via interoceptors of the back 2) Dorsal ramus via exteroceptors and proprioceptors of the back 3) Ventral ramus via interoreceptors of body wall and limbs 4) Ventral ramus via exteroceptors and proprioceptors of body wall and limbs 5) Rami communicantes via interoceptors of visceral organs
40
What do nerve plexuses arise from?
- arise during development as ventral rami containing sensory and motor fibres converge
41
Describe the path that proprioception, fine touch, pressure, and vibration take through posterior columns:
- axons from sensory neurons enter spinal cord through dorsal root ganglia of the upper or lower body - if coming from the upper body, axons ascend within the fasciculus cuneatus - if coming from the lower body (inferior to T6), axons ascend within the fasciculus gracilis - these first order neurons synapse at the nucleus cuneatus or gracilis of the medulla oblongata - the second order neurons immediately decussate and ascend to the thalamus via the medial lemniscus - second order neurons synapse at the ventral posterolateral nucleus of the thalamus - axons of the third order neurons of the thalamus project to the primary sensory cortex on side opposite to stimulus
42
Describe the path that proprioception takes through spinocerebellar tracts:
- axons from sensory neurons enter posterior gray horn through dorsal root ganglia - decussation immediately in posterior horn of spinal cord - axons of second order neurons ascend via anterior spinocerebellar tract to cerebellum - decussation again in cerebellum - information projected to cerebellar cortex primarily on same side as stimulus
43
Describe the path that pain, temperature, crude touch, and pressure take through the spinothalamic tracts:
- axons from sensory receptors enter posterior gray horn through dorsal roots - decussation occurs immediately in the posterior gray horn - second order neurons for pain and temperature ascend via the lateral spinothalamic tract - second order neurons for crude touch and pressure ascend via the anterior spinothalamic tract - both tracts ascend through the medulla and synapse at the ventral posterolateral nucleus of the thalamus - third order thalamic neurons project to the primary sensory cortex on the opposite side to stimulus
44
What are three key differences between the spinocerebellar and the posterior column/spinothalamic tracts?
1) only first and second order neurons 2) no synapse in the thalamus 3) double decussation
45
If visceral sensory information is getting mixed up with other sensory information in the spinal cord, where is kidney pain felt on the dermatome?
lower back and buttocks
46
A myocardial infarction is often perceived as _____.
pain down arm
47
What are the 6 potential paths a motor command can take from the spinal cord?
1) Dorsal ramus to skeletal muscles of the back 2) Postganglionic fibres to smooth muscles, glands of the back 3) Ventral ramus to skeletal muscles of the body wall and limbs 4) Postganglionic fibres to smooth muscles, glands of body wall and limbs 5) Preganglionic fibres in the rami communicantes to sympathetic ganglia innervating abdominopelvic viscera 6) Postganglionic fibres in the rami communicantes to smooth muscles, glands, visceral organs of thoracic cavity
48
What do somatic motor pathways innervate?
Skeletal muscle
49
Where does an upper motor neuron originate? Where does a lower motor neuron originate?
- upper: within the brain | - lower: lateral or anterior horn of spinal cord
50
Describe the pathway through the corticospinal tract:
- upper motor neurons from the primary motor cortex descend to the medulla where they decussate (90% here but some decussate in anterior white commissure) - continue to descend on opposite side of spinal cord - synapse at lower motor neurons in anterior horn of spinal cord
51
Describe the pathway through the corticobulbar tract:
- Upper motor neurons originate on primary motor cortex - decussate in the brain stem - synapse with lower motor neurons of some cranial nerves
52
What do neurons from the corticospinal tract control? What do neurons from the corticobulbar tract control?
- corticospinal tract neurons control voluntary movement of skeletal muscle below the neck - corticobulbar tract neurons control conscious control of skeletal muscles of the eye, jaw, face, and some muscles of the neck and pharynx
53
If a person injures their spinal cord at C1-C2 level, what happens?
They become quadriplegic and lose sensory input and motor output to any area below the neck, including the diaphragm
54
If a person injures their spinal cord at T9-T12 level, what happens?
They become paraplegic and lose sensory input and motor output to the lower limbs
55
Function of the cerebrum:
- conscious thought processes and intellectual functions - memory storage and processing - conscious and subconscious regulation of skeletal muscle contraction
56
Function of the diencephalon and the structures it contains:
- Thalamus: relay and processing centre for sensory information - Hypothalamus: centres controlling emotions, autonomic functions, hormone production
57
Function of the pons:
- relay sensory information to cerebellum and thalamus | - subconscious somatic and visceral motor centres
58
Function of the medulla oblongata:
- relay sensory information to thalamus and other portions of brain stem - autonomic centres for regulation of visceral function
59
Function of the cerebellum:
- coordinate complex somatic motor patterns | - adjust output of motor centres in brain and spinal cord
60
Function of mesencephalon/midbrain:
- process visual and auditory information - generate reflexive somatic motor responses - maintenance of consciousness
61
What are the two layers of dura mater?
- periosteal/endosteal cranial dura | - meningeal cranial dura
62
What is contained in the dural sinuses?
interstitial fluid and blood vessels
63
What flows through the subarachnoid space?
Cerebrospinal fluid
64
What anchors the pia mater to the surface of the brain?
astrocytes
65
What are the main functions of cerebrospinal fluid?
1) prevent contact between neural tissue and surrounding bones 2) provide support for the brain 3) transport nutrients to CNS tissue 4) transport waste away from CNS
66
At which location are the ependymal cells not freely permeable?
- choroid plexus where CSF is produced | - ependymal cells cover fenestrated capillaries here and prevent free diffusion of molecules
67
What are ventricles and how many do we have?
- large cavities filled with cerebrospinal fluid | - we have 4 ventricles
68
How is CSF circulated?
- exits the fourth ventricle to subarachnoid space via lateral apertures and median aperture - small amount of CSF goes to centrla canal of spinal cord
69
What is the main purpose of the blood brain barrier (BBB)?
- separate blood supply of CNS from general circulation
70
What sort of material can pass through the BBB?
- lipid soluble material may pass by diffusion | - water soluble material may pass through transport mechanisms
71
What are the four main sites where the BBB has a different permeability?
1) Hypothalamus - increased permeability to allow for monitoring of the internal environment and release of hormones 2) Capillaries in pineal gland - increased permeability 3) Capillaries in posterior lobe of pituitary gland - continuous with floor of hypothalamus aka increased permeability 4) Capillaries in choroid plexus are highly permeable
72
How does arterial blood reach the brain (which vessels) and how does venous blood leave the brain?
- arterial blood: internal carotid and vertebral arteries | - venous blood: internal jugular veins
73
Which division of the PNS has cell bodies in ganglia and which has cell bodies in the gray matter of the spinal cord?
1) autonomic | 2) somatic
74
What are the main functions of the hypothalamus
- monitor cerebral activities and coordinate with autonomic functions - coordinate function of the endocrine system by inhibiting or stimulating pituitary gland - set appetitive drives and behaviours - set emotional state
75
What is the third division of the autonomic nervous system?
- enteric nervous system | - neurons are located in the walls of the digestive tract
76
What is the main purpose of the sympathetic nervous system?
- fight or flight ; mobilize the body for activity
77
Where are sympathetic ganglia found?
- ganglia are located near the spinal cord
78
What are the three locations of postganglionic neurons?
1) sympathetic chain ganglia on both sides of vertebral column 2) collateral ganglia anterior to vertebral column 3) adrenal medulla
79
Where do preganglionic neurons of the sympathetic nervous system originate?
- lateral horn of spinal cord between T1 and L2
80
Splanchnic nerves converge on what type of ganglia and innervate what?
- converge on collateral ganglia | - innervate abdominopelvic cavity organs
81
Sympathetic input to thoracic cavity viscera follow what pathway?
- from lateral gray horn travel through ventral root - enter white ramus communicantes and sympathetic chain ganglion and synapse with post ganglionic neuron - postganglionic fibre exits via sympathetic nerve
82
Sympathetic input to general visceral effectors follow what pathway?
- from lateral gray horn travel through ventral root - enter white ramus communicantes sympathetic chain ganglion and synapse with postganglionic neuron - postganglionic fibre exits via gray ramus communicantes and travels out a spinal nerve
83
Sympathetic input to the adrenal medulla follows what pathway?
- from lateral gray horn, travel through ventral root - pass through white ramus communicantes and sympathetic chain ganglion without synapsing - pass through collateral ganglia without synapsing - synapse at adrenal medulla
84
Why are the preganglionic fibres that project to the adrenal medulla longer than the postganglionic fibres?
- post ganglionic fibres are unmyelinated while preganglionic fibres are myelinated - when we want to activate the adrenal medulla, we want to activate it as fast as possible
85
What is the main purpose of the parasympathetic nervous system?
- conserve energy
86
Where does the vagus nerve originate? What are its targets
- Vagus nerve is cranial nerve X - originates at medulla oblongata - innervates heart, lungs, liver, gallbladder, spleen, pancreas, LI, SI, rectum, kidney, urinary bladder, reproductive organs
87
What are the two locations of synapses with postganglionic neurons?
- near the target organ (terminal) | - within the target organ (intramural)
88
What are 4 organs innervated by the sacral parasympathetic neurons?
1) kidney 2) urinary bladder 3) rectum 4) reproductive organs

Human Anatomy (EPHE 141) (3 decks)

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