1
Q
Nervous system
A
Consists of two principle divisions
-central nervous system (CNS) (brain and spinal cord)
-peripheral nervous system (PNS) (the nerves of the body)
🔹subdivision of the PNS is the autonomic nervous system (ANS), which consists of structures that regulate the body’s automatic or involuntary functions for ex heart rate, secretions of chemicals by glands
2
Q
Cells of the nervous system
A
- neurons, or nerve cells (conduct impulses)
- glia, which are support cells, (glia support neurons)
3
Q
Neurons
A
Each neuron consists of three parts: a main part called the neuron CELL BODY, one or more branching projections called DENDRITES, and one elongated projection known as an AXON
- the three types of neurons are classified according to the direction in which they transmit impulses
1. Sensory neurons
2. Motor neurons
3. Interneurons
4
Q
Dendrites
A
-the processes or projections that transmit impulses TO the neuron cell bodies or axons
5
Q
Axons
A
- are the processes that transmit impulses AWAY from the neuron cell bodies or dendrites
- surrounded by a segmented wrapping of a material called myelin
- myelin is a white, fatty substance formed by schwann cells that wrap around some axons outside the CNS
- such fibers are called myelinated fibers
6
Q
Sensory neurons
A
- transmit impulses to the spinal cord and brain from all parts of the body
- also called afferent neurons
7
Q
Motor neurons
A
- transmit impulses in the opposite direction of sensory neurons
- transmit impulses away from the brain and spinal cord
- they do not conduct impulses to all parts of the body but only to two kinds of tissue: muscle and glandular epithelial tissue
- also called efferent neurons
8
Q
Interneurons
A
- conduct impulses from sensory neurons to motor neurons
- often also connect with each other to form complex, central networks of nerve fibers
- also called central or connecting neurons
9
Q
Nodes of ranvier
A
Indentations between adjacent Schwann cells
10
Q
The outer cell membrane of a Schwann cell is called _____
A
- neurilemma
- axons in the brain and spinal cord have no neurilemma and this is clinically significant because it plays an essential part in the regeneration of cut and injured axons
- therefore the potential for regeneration in the brain and spinal cord is far less than it is in the peripheral nervous system
11
Q
Glia aka neuroglia
A
-do not specialize in transmitting impulses
-special type of supporting cells
-one function is to hold the functioning neurons together and protect them
-also the regulation of neuron function, therefore they act not just as physical “glue” but also help bring the various functions of the nervous tissue together into a coordinated whole
-one of the most common types of brain tumour called a glioma develops from them
Vary in size and shape:
-astrocytes
-microglia
-oligodendrocytes
12
Q
Astrocytes (type of glia)
A
- look somewhat like stars because of the threadlike extensions that jut out from their surfaces
- their threadlike branches attach to neurons and to small blood vessels, holding their structures close to each other
- the “feet” of the astrocytes form a wall around the outside of the blood vessels in the nervous system. This astrocyte wall, along with the vessel wall, forms a structure known as the blood-brain barrier (BBB).
13
Q
Microglia (a type of glia)
A
- smaller than astrocytes
- usually remain stationary, but in inflamed or degenerating brain tissue, they enlarge, move about, and act as microbe eating scavengers
- they surround the microbes, draw them into their cytoplasm, and digest them
- also help cleanup cell damage resulting from injury or disease
14
Q
Oligodendrocytes (a type of glia)
A
- help hold nerve fibers together and also serve another and probably more important function- they produce the fatty myelin sheath that envelops nerve fibers located in the brain and spinal cord
- each oligodendrocyte can form part of the myelin sheath around several axons whereas Schwann cells wrap entirely around only one axon
15
Q
Disorders of nervous tissue
A
-multiple sclerosis: characterized by myelin loss in central nerve fibers and resulting conduction impairments
-tumours
🔹general name for nervous system tumours is neuroma
🔹most neuromas are gliomas, glial tumours
🔹multiple neurofibromatosis: characterized by numerous benign tumours
16
Q
Nerve
A
- nerve: Bundle of peripheral axons
- tract: bundle of central axons
- white matter: brain or cord tissue composed primarily of myelinated axons (tracts)
- gray matter: brain or cord tissue composed primarily of cell bodies and unmyelinated fibers
17
Q
Nerve coverings
A
- nerve coverings: fibrous connective tissue
- endoneurium: surrounds individual fibers within a nerve
- perineurium: surrounds a group (fascicle) of nerve fibers
- epineurium: surrounds the entire nerve
18
Q
CNS
A
- its two major structures, the brain and spinal cord are found along the midline of the body
- brain is protected in the cranial cavity of the skull
- spinal cord is surrounded by the spinal cavity by the vertebral column
- brain and spinal cord are also covered by protective membranes called meninges
19
Q
Divisions of the brain
A
The brain consists of the following major divisions, named in ascending order beginning with the most inferior part 1. Brainstem 🔹medulla oblongata 🔹pons 🔹midbrain 2. cerebellum 3. diencephalon 🔹hypothalamus 🔹thalamus 🔹pineal gland 4. cerebrum
20
Q
Brainstem
A
-consists of, named in ascending order, the medulla oblongata, pons, and midbrain
-structure: white matter with bits of grey matter scattered through it
-functions: all three parts of brainstem are two-way conduction pathway
-MEDULLA OBLONGATA: two-way conduction pathway between the spinal cord and higher brain centres; cardiac, respiratory, and vasomotor control center
🔹upward extension of the spinal cord, lies just inside the cranial cavity above the large hole in the occpital bone called the foramen magnum
🔹consists of grey and white matter. in the medulla bits of grey matter mix intricately with white matter. in the spinal cord grey and white matter do not intermingle
-PONS: two way conduction pathway between areas of the brain and other regions of the body; influences respiration
-MIDBRAIN: two way conduction pathway; relay for visual and auditory impulses
21
Q
Cerebellum
A
- second largest part of the brain
- muscle coordination; maintenance of equilibrium and posture; assists cerebrum
- folded grey matter composes the thin outer layer, forming a large surface area of nervous connections that allow for a huge amount of information processing
- white matter tracts form most of the interior
- plays an essential part in the production of normal movements, perhaps has an overall coordinating function for the whole brain
22
Q
Diencephalon
A
HYPOTHALAMUS: regulation of body temperature, water balance, sleep-cycle control, appetite, and sexual arousal, heartbeat, constriction and dilation of blood vessels
-the posterior pituitary gland, the stalk that attaches it to the undersurface of the brain, and areas of grey matter located in the side walls of a fluid-filled space called the third ventricle are extensions of the hypothalamus
-exerts major control over virtually all internal organs
-some neurons in the hypothalamus make the hormones that the posterior pituitary gland secretes into the blood
THALAMUS: sensory relay station from various body areas to cerebral cortex; emotions and alerting or arousal mechanisms
-each enlarged end lies in a lateral wall of the third ventricle
PINEAL GLAND: adjusts output of melatonin in response to changes in external light, to keep the body’s internal clock on time
23
Q
Cerebrum
A
- largest and uppermost part of the brain
- has ridges and grooves
- ridges: convolutions, or GYRI
- grooves: SULCI
- deepest sulci are called fissures, longitudinal tissue divides the cerebrum into right and left halves or hemispheres. These halves are almost separate structures except for their lower mid portions, which are connected by a structure called the corpus callosum
- two deep sulci subdivide each cerebral hemisphere into four major lobes and each lobe into numerous convolutions
- a thin layer of grey matter called the cerebral cortex is made up of neuron dendrites and cell bodies; this makes up the surface of the cerebrum
- white matter makes up most of the interior, within this white matter are a few islands of grey matter known as basal nuclei or basal ganglia, whose functioning is essential for producing automatic movements and postures (Parkinson’s disease is a disease of the basal nuclei)
- sensory perception, emotions, willed movements, consciousness, memory
24
Q
Spinal cord: structure
A
- lies inside spinal column in the spinal cavity
- extends from the occipital bone down to the bottom of the first lumbar vertebra or T12
- place your hands on your hips, and they will line up with your fourth lumbar vertebra, your spinal cord ends just above this level
- spinal cord provides two way conduction paths to and from the brain
- ascending tracts: conduct impulses up the cord to the brain
- descending tracts: conduct impulses down the cord from the brain
25
Spinal cord: functions
- it switches or transfers incoming sensory impulses to outgoing motor impulses thereby making it possible for a reflex to occur
- carry impulses to and from the brain
26
Coverings and fluid spaces of the brain and spinal cord
- nervous tissue is not sturdy, even moderate pressure can kill nerve cells, so nature safeguards the chief organs made of this tissue (spinal cord and brain) by surrounding them with a tough, fluid cushioned set of membranes called meninges. The meninges are then surrounded by bone
- three layers of the spinal meninges are:
1. Dura mater
2. Pia mater
3. Arachnoid mater
27
Dura mater (meninges)
-the tough outer layer, that lines the vertebral canal
28
Pia mater (meninges)
-the innermost membrane covering the spinal cord itself
29
Arachnoid mater
-membrane between the dura and pia mater
30
Meningitis
- inflammation or infection of the meninges
| - severe headaches and neck pain
31
Cerebrospinal fluid (CSF)
- fluid fills the subarachnoid spaces between the pia mater and arachnoid mater in the brain and spinal cord, this fluid is called CSF
- also fills spaces in the brain called cerebral ventricles
- one of the body's circulating fluids
- forms continually from fluid filtering out of the blood in a network of brain capillaries known as the choroid plexus and into the ventricles
- this fluid forms continually from blood, circulates, and is resorbed into blood
32
Peripheral nervous system
-nerves connecting the brain and spinal cord to other parts of the body constitute the peripheral nervous system (PNS)
33
Cranial nerves
- 12 pairs of cranial nerves emerge from the undersurface of the brain, extending mostly from the brainstem
- their fibers conduct impulses between the brain and structures in the head and neck and in the thoracic and abdominal cavities
34
Lumbar puncture
- the meninges, the fluid containing membranes surrounding the brain and spinal cord, extend beyond the spinal cord, an anatomical fact that is most convenient in regard to being able to perform lumbar punctures without putting the spinal cord at risk of injury
- withdrawal of some CSF from the subarachnoid space in the lumbar region of the spinal cord
- needle gets inserted just above or below the fourth lumbar vertebra
- sample should be yellow ish and clear
35
Hydrocephalus
"Water on the brain"
-abnormal accumulation of CSF in the ventricles of the brain
-communicating hydrocephalus is caused by an inability to absorb CSF into the venous sinuses, or an overproduction of CSF
-non communicating hydrocephalus is caused by an obstruction in the flow of CSF
-may be congenital or acquired
Symptoms and complications:
-dilation of the ventricular system leading to compression atrophy of the brain
-appears as dilated ventricles
36
Concussion
- temporary loss of normal brain function due to a blunt trauma that bends the brain stem
- headache, nausea, light sensitivity, vertigo etc
37
Cerebral contusion
- bruising of the brain; caused by blunt trauma that throws the brain against the rough interior surfaces of the skull
- edema, swelling and tissue necrosis
- visualized on CT as hypo-dense areas, dotted with high intensity lesions, most often in the frontal regions of the brain
38
Epidural hematoma
- by far most dangerous
- acute arterial bleed between the dura mater and the inner table of the skull
- can lead to rapid loss of consciousness and death; bleeding is fast as it involves arteries, and causes compression and displacement of the brain structures towards midline (mass effect) or inferiorly to foramen magnum
- lens shaped (double convex) high density lesion visualized on CT
- may be necessary to open skull surgically for drainage
39
Subdural hematoma
- venous bleed caused by ruptured veins between the mater and the arachnoid mater. Associated with a blow to the frontal or occipital bone
- on CT it appears as a hyper-dense crescent shaped lesion adjacent to the inner table of the skull. May resolve on its own, but may require surgical intervention
40
Subarachnoid hematoma
- venous bleed into the ventricular system
- may increase intracranial pressure
- usually appears as increased density in the fall cerebri, subarachnoid cisterns, or sulci
41
TIA (transient ischemic attack)
- temporary loss of neurological functions that resolve within 24 hours. 2/3 of strokes are preceded by one or more TIA's so accurate diagnosis is important
- TIA's are most often caused by temporary vessel occlusion or stenosis
- angiography is the most effective diagnostic modality
42
Cerebrovascular accident (stroke)
- acute ischemic stroke: an acute brain infarction, caused by loss of blood supply to a localized portion of the brain. Severity of symptoms is dependent on the number of arteries involved. Usually caused by atherosclerotic disease of the brain
- hemorrhagic stroke: ruptured blood vessel in the brain. Usually caused by hypertension, rupture of a congenital berry aneurysm or AVM
- acute hemiparesis (one sided weakness) or hemiplegia (paralysis on one side of the body) and/or difficulty speaking
- time is of the essence as clot busting drugs are in effective three hours after initial onset of stroke
43
AVM atriovenous fistula/ malformation
- abnormal communication between an artery and a vein
- one of the common causes of hemorrhagic stroke
- appears on CT as a mass entanglement of vessels drained by dilated veins emerging from the center of the mass
44
Glioma (astrocytoma is most common)
- the most common primary brain tumour. May or may not be malignant. 70% are astrocytomas which are slow growing infiltrating tumours
- prognosis is poor, astrocytomas have a 5 year survival rate following treatment
45
Meningitis
- acute inflammation of the pia mater and arachnoid mater. Bacterial meningitis is most common
- acute onset of severe headache and neck pain. Can be diagnosed by lab analysis of CSF. Needs to be done quick because this disease can lead to encephalitis (inflammation of the brain) which is life threatening
46
What are contraindications for lumbar puncture?
Increased intracranial pressure or cerebral hemorrhaging
47
Metastatic carcinoma (metastasis)
- brain cancer that has metastasized from a primary tutor in the bone, lung or breast. Usually the metastatic lesions reach the brain through the blood stream (hematogenous spread)
- symptoms and complications and appearance are the same as a glioma
48
Ventricles
1st is more superior
2nd is middle
3rd white dot inside which is the pineal gland
49
Vertebral disks
- outside is fibrous inside is gushy (they can herniate)
- shock absorbers for the body
- as you get older, they can dry out and are more likely to injure more (herniated disk)
50
Spina bifida
- incomplete closure of the vertebral canal. Usually occurs in the lumbosacral area. May demonstrate a protrusion of the meninges, spinal cord, or both. (Meningocele, myelocele, myelomeningocele, respectively)
- if there is no visible abnormality or mental deficit it is called spina bifida occulta
- as with any opening to the outside of the body, there is increased potential for infection. In more severe cases (meningocele, myelocele, myelomeningocele) verging degrees of paralysis will occur. Most patients with myelomeningocele will have hydrocephalus as well
51
Herniated disk
- the nucleus pulposus of a vertebral disk protrudes from the annulus fibrosis, due to trauma, aging or degenerative disease. Most often occurs in the lower lumbar spine, where it causes sciatica, but can occur elsewhere
- sudden severe pain and muscle weakness, in upper or lower limbs depending on the location of herniation
- MRI is best for visualization
52
Parkinson's
- also known as "shaking palsy"
- degenerative disorder of middle or later life, caused by inadequate production of the neuro transmitter dopamine
- stooped posture, slowness of movement, persistent tremor while at rest, stiff facial expression, involuntary movement of limbs
- CT scans may demonstrate atrophy of the cortex but may not be distinguishable from the normal aging process
- treated with administration of L-dopa medication
53
Alzheimer's
- a diffuse progressive form of cerebral atrophy that causes premature memory impairment
- memory loss (especially short term memory) short attention span, disorientation, and loss of language skills. There are medications to slow the progress but no cure
54
Neuroglia (glial) cells are specialized neurons (true/false)
False!
55
Sensory neurons transmit information to the brain and spinal cord, and motor neurons transmit information away from the brain and spinal cord (true/false)
True!
56
Motor neurons transmit information to muscle and glandular epithelium only
True
57
A life threatening brain tumour that arises from glial cells is known as a ____
Glioma
58
Axons coated in myelin can transmit sensory and motor information more quickly than those without
True
59
Cerebrum
The large superior portion of the brain
60
Cerebellum
The smaller posteroinferior part of the brain that is responsible for muscle coordination, balance and posture
61
Diencephalon
Egg shaped section between the cerebrum and brainstem that houses the thalamus, hypothalamus and pineal gland
62
Cerebral cortex
A thin layer of grey matter on the surface of the cerebrum that is responsible for "consciousness, thinking, memory, sensations, emotions, and willed movements"
63
Brain stem
Enlarged upward extension of the spinal cord formed by the midbrain, pons, and medulla oblongata
64
Basal nuclei
Masses of grey matter found deep within the cerebrum, responsible for automatic movements and postures such as developing good x-ray habits
65
Ridges of tissue on the cerebral cortex as
Gyri
66
Depression in the cerebral cortex are know as
Sulci
67
Deep grooves in the cerebral cortex are called
Fissures
68
The diencephalon is part of the brainstem (true/false)
False
69
The thalmus sorts and relays sensory/emotional information to the _____
Cerebral cortex
70
The diencephalon is superior to the brain stem, and is completely surrounded by cerebral hemispheres (true/false)
True
71
Pons
Middle section of the brain stem that relays information to the cerebellum
72
Midbrain
Superior section of the brain stem
73
Medulla oblongata
Most inferior section of the brain stem that regulates heart rate, respiration, and blood pressure (through vasomotor responses ex change in vessel diameter)
74
Coordination and communication between the left brain and the right brain is controlled by a fibrous tract of white matter known as
The corpus callosum
75
Explain the term "hemispheric lateralization"
Refers to the fact that each cerebral hemisphere is responsible for different tasks; the left for logical thinking, reading, writing, math etc and the right for creativity. Also the left brain controls the right distal extremities and vice versa
76
What are "dural sinuses" and what do they do?
Are reservoir like spaces between the inner and outermost layers of the brains dura mater, where venous blood from the brain collects, before returning to the heart via the veins in the neck
77
The double walled fold in the dura mater that separates the hemispheres of the cerebellum is know as
The falx cerebri
78
Where is the subarachnoid space, and what kind of fluid does it contain?
- between the pia mater and arachnoid mater in the brain and spinal cord
- CSF (cerebrospinal fluid)
79
What does CSF stand for and what two functions does it have?
Cerebrospinal fluid- it protects the brain from impact and provides nutrients
80
What structures form CSF and where are these structures located?
-the choroid plexus which are specialized structures in the roofs of the cerebral ventricles
81
Which space do we draw CSF from during a lumbar puncture or spinal tap?
Subarachnoid space
82
How is CSF returned to the blood?
It is resorbed into the dural sinuses, which return venous blood to the heart
83
Where is the "epidural space"
It lies in the lumen of the bony vertebral canal and the dura mater of the spinal cord
84
```
Which of the following is located most superiorly in the body?
A) medulla oblongata
B) pineal gland
C) diencephalon
D) corpus callosum
```
Corpus callosum
85
```
Which of the following is located most inferiorly in the body?
A) lateral ventricle
B) third ventricle
C) thalmus
D) pons
```
Pons
86
Which of the following is located most anteriorly in the body?
A) anterior horns of the lateral ventricles
B) midbrain
C) pons
D) medulla oblongata
Anterior horns of the lateral ventricles
87
A person with an atriovenous malformation
Is at increased risk for hemorrhagic stroke
88
What is always a contradiction for lumbar puncture?
Epidural hematoma
89
```
Which of the following has the potential to cause acute neurological deficits?
A) spina bifida occulta
B) myelocele
C) Parkinson's
D) meningitis
```
Meningitis
ANPH 202
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