what are the spinal nerves of the spinal cord? how are they arranged?
C1-C8 T1-T12 L1-L5 S1-S5 1 (coccygeal)
*Nerves C1 - C7 emerge above the vertebra of same number. C8 emerges below C7. All others emerge below the vertebra of the same number.
What is the caudal equina?
the spinal nerves that extend from the conus medullaris
what is the conus medullar is?
the terminal portion of the spinal cord (because the spinal cord is shorter than the vertebral column)
*spinal cord ends at the conus medlars at L1
*spinal tap is done at the lumbar cistern at the L5, S1 or L4, L5
what is the filum terminale?
extension of the pia mater that acts anchors the spinal cord
Sensory is Afferent, Motor is Efferent; Dorsal is Afferent, Ventral is Afferent
on our backs; entirely sensory in function; contain dorsal root ganglia
on our stomachs; entirely motor in function; the cell bodies lie in the ventral horn of the spinal cord
what is the dermatome?
Area of skin innervated by one DORSAL root (unbranched spinal nerve)
What is plexus? (and examples)
the joining of some spinal nerve branches to other spinal nerve branches. forms larger named nerves
ex: ulnar nerve, medial nerve, static nerve
what are the three meninges (and physical appearance)?
- dura mater (thick) - subarachnoid (spidery) - pia mater(thinnest)
what are the meningeal spaces (and location)?
- epidural space (separates the dura mater from and the skull/vertebrae column) - subdural space (separates the dura mater from the subarachnoid) - subarachnoid (separates the arachnoid from the pia mater)
what is the content of the meningeal spaces?
- epidural: fat and veins (only in the epidural space surrounding the spinal cord; the epidural surrounding the brain is EMPTY) - subdural space: potential space- NOTHING THERE - subarachnoid: cerebrospinal fluid, arteries, extended in places called cisterns
what are the extensions of the pia mater (and their functions)?
- denticulate ligaments: anchors the spinal cord within the dura mater filum terminale: anchors the spinal cord
what are the four brain ventricles (and location)
- 2 lateral ventricles (within the neocortex- one in each hemisphere) - third ventricle (located medially; b/w the two halves of the diencephalon) - fourth ventricle (between cerebellum and the roof of the pons and medulla oblongata)
what are the connections of the ventricles and meningeal space?
- foramen of Monroe (medial): connects the lateral ventricles to the midline third ventricle - cerebral aqueduct (aqueduct of sylvius): takes CSF from the third to the fourth ventricle - formamen of magendie (medial) and two foramina of luschka (lateral): exit points from the fourth ventricle to the subarachnoid space
what forms CSF?
choroid plexus ependymal cells
what are the specialized structures that reabsorb CSF?
Gravity pulls the CSF from the lateral ventrical third ventricle fourth ventricle (out through the foramen) subarachnoid space. And then..... DESTINATION 1: Because of all the pressure of the CSF, it enters the subarachnoid space and then works its way back up to the brain to the top. (subarachnoid venous lacunae, arachnoid graulation, and arachnoid villae (which protrudes into the SSS and allows for diffusion) superior sagittal sinus blood (venous) heart. OR... DESTINATION 2: it goes down to the subarachnoid space of the spinal cord. For DESTINATION 1: the 4 reabsorption sites are listed above. These are sites where CSF rejoins the venous system/blood (YES THERE IS CSF IN THE BLOOD) The superior sagittal sinus is an area where venous blood (blood destined for the heart) pools. ***CSF is produced constantly which is why it is important to have this drainage system, otherwise pressure would build up
what percent of our brain is utilized?
are individuals more commonly right brain dominate or left?
Most brain functions are localized to specific brain areas, but redundancies exist. Because of redundancies and cross-talk between brain hemispheres, the notion that we are either left- or right-brained thinkers is also a myth.
T or F: you can train your brain to gain mental flexibility
F- Brain-training can give a task-specific boost, but may not be transferrable.
What is Hebbian Plasticity?
**DOUBLE CHECK* - use it or lose it - fire together, wire together
what is phrenology?
a pseudomedicine primarily focused on measurements of the human skull, based on the concept that the brain is the organ of the mind, and that certain brain areas have localized, specific functions or modules. BRAIN MYTH (rather we have localization of function)
relationship between the nervous system and congenital defects?
1/3 of all neonatal congenital birth defects - 75% of spontaneous fetal deaths are rural related - 40% of deaths in first year of life
what are causes of congenital malformation?
- genetic factors (genetic mutations) - environmental factors - combination of the two
another name for environmental insults is ________?
- time: specific - stimulus: largely unknown
The effects of teratogens depend not only on the nature of the teratogenic agent, but also on the time during embryogenesis (time-specific). More than one teratogen causes the same developmental anomaly depending on the time of insult.
how many cells are in the body?
what are the three stages of human brain development?
- fetal period (3-8 weeks prenatal): period of organogenesis - embryonic period (9 weeks prenatal-newborn): period of cellular proliferation - maturation period (25 weeks prenatal- 4 years old): period of functional maturation of the neuron
*early stage occurs in the first two weeks prenatal
what part of the prenatal process is the most crucial for the CNS development?
first four months (period of time that CNS is most susceptible to teratogen influence)
3-8 weeks prenatal; organogenesis
what major developmental events occur in the embryonic period?
1. The formation of three germ layers (ectoderm, mesoderm, and endoderm) 2. The formation of notochord 3. the formation of the neural tube 4. Primary neuralation
Beginning of the 3rd week?
formation of the three germ layers (ectoderm, mesoderm, endoderm) from the bilaminar disc (which consisted of two layers- epiblast and hypoblast)
Process summary: The primitive streak appears on the anterior epiblast, marking the beginning of gastrulation. The cells in the epiblast begin to migrate to form the three germ layer
Process: longitudinal rod (notochord) forms from mesoderm bells soon after gastrulation is complete. The notochord and a region anterior to it, called the prechordal plate express bone morphogenic protein (BMP) inhibitors (noggin, chordin, and follistatin) and sonic hedgehog (SHH) which induce the overlying anterior ectoderm to thicken and form a longitudinal neural plate. Late in the third week, the neural plate develops the neural folds which have the effect of creating the neural groove which begins to close (to eventually form the neural tube). This is induced by the notochord.
what does the notochord later become?
the spinal/vertebral column
1) closure of the neural tube (fully forms): anterior neuropore closes at 24-26 days (primary neurulation) while posterior neuropore closes at 26-28 days (secondary neurulation) 2) induction of mesoderm-derived structures by the neural tube 3) dilation of the neural tube (which leads to the formation of 3 primary vesicles) 4) optic vesicles form 5) neural crest formation 6) demarcation of spinal cord
what does the anterior neuropore later become?
what does the neural tube later become?
CNS (brain and spinal cord); its cavity becomes the ventricular system of the brain
neural tube defects
*also called dysraphisms
1) anencephaly: (no forebrain; incompatible with life) 2) encephalocele/ cranium bifidum: anterior failure, severe retardation 3) spina bifida: posterior failure of neural tube development
Neural tube defects (dysraphisms) facts
1) Failure of the neural tube formation or closure 2) Failure of induction of certain mesodermal structures 3) 1/1000 live births 4) Diagnosis during pregnancy - Elevated levels of alpha-fetoprotein - Ultrasound examination 5) Folic acid deficit is now added to fortified grain products in the US. NOTE: Vitamin B9 (Folate) is needed for DNA synthesis. Folic acid play s a role in neural tube defect prevention
In spina bifida occulta, the spinal cord is properly formed, but some vertebrae, usually in the lower lumbar region do not completely form. The only sign may be a tuft of hair at the base of the lumbar vertebral column.
spina bifida cystica
- meningocele: protrusion of the spinal meninges but normal development of the spinal cord
- meningomyelocele: protrusion of the spinal cord and meninges
- myeloschisis: incomplete development of the spinal cord with the consequent joining of the neural tube to the skin and opening the neural tube to environmental elements
neural crest later becomes?
PNS, sensory and autonomic ganglia (amongst other differentiated cell types)
what are the different types of neural crest cells?
- from prosencephalon: telencephalon, diencephalon - mesencephalon - from rhombencephalon: metencephalon, myelencephalon
what is holoprosencephaly?
- division defect; the prosencephalon divides into the diencephalon left and right hemispheres (paired telencephalon vesicles)via inward rotation, this division is induced by SHH (which is secreted initially by the notochord and later by the ventral portion of the nervous system). Failure of telencephalic division to occur results in an anomaly termed holoprosencephaly in which the fetus or infant has a single forebrain vesicle instead of right and left hemispheres.
forebrain, midbrain, and hindbrain (with their respective structures) are formed - the bulges (vesicles) and flexures start to bend (get into proper formation)
In the 14th week, the growth of the telencephalon overshadows other parts of the nervous system, because it becomes the biggest part of the brain
when do sulcus and Gyri form?
3-7 months (prenatal)
major developmental events during the maturation period?
1) Neurogenesis: neuron generation continues THROUGHOUT life 2) Myelination: prenatally to 4 postnatal years, continues to adulthood 3) Synaptogenesis: birth to 2 years (also in late childhood), continues to adulthood 4) Dendrite growth 5) Neuronal and synaptic pruning (after 2 years of genesis)
at what age do you find the greatest number of synapses (in males and females)?
girls: 11 yrs boys: 12.5
what is the source of cells for the maturation period?
- neuroepithelial layer
how many neurons are in the brain?
anomalies during period of cell proliferation and migration?
The most common acute disease involving a single nerve and is the most common cause of acute facial nerve paralysis (>80%).
Bell's palsy is defined as a one-sided facial nerve (the cranial nerve VII) paralysis of unknown cause.
Cause an inability to control facial muscles on the affected side.
● The common presentation of this condition is a rapid onset of partial or complete paralysis that often occurs overnight.
● It is thought that an inflammatory condition leads to swelling of the facial nerve.
● Typically, the condition gets better on its own with most achieving normal or near-normal function.
● Corticosteroids have been found to improve outcomes, when used early, while anti-viral medications are of questionable benefit.
● Many show signs of improvement as early as 10 days after the onset, even without treatment.
Cognitive Load Theory (and its components)
The idea that there is a limit to working capacity.
- intrinsic CL: how difficult the matter is (manage) extrinsic CL: external things that make learning the material harder (minimize) - germane CL: way of streamlining the learning experience to make it easier (maximize)
components of the limbic system?
- cingulate gyrus - parahippocampal gyrus (located in the temporal lobe) - uncus
what are the subcortical areas of the telencephalon?
- frontal - parietal - occipital - temporal - insula
the sulcus in the neocortex?
- Lateral fissure stops midway (the straight line added is imaginary)- separates the frontal lobe from temporal. And parietal from temporal - Parietooccipital fissure: sulcus (seen only in a sagittal view) that divides the parietal lobe from the occipital lobe - Central sulcus: located about midway in the brain from anterior to posterior; the dividing line between the frontal and right parietal lobes - Calcerine fissure: is a fissure that does not divide lobes. It resides only in the occipital lobe and divides it in half. Its' along this fissure that we have our visual and conscious perception - Preoccipital notch: inferior dividing line between occipital lobe and temporal lobe. The only place that you can tell where the occipital lobe and temporal lobe end/begin. Can be seen also on the outside of the brain (the notch at the bottom that goes up a little)
what are the gyri of the neocortex
- Frontal pole: most anterior part of the brain - Occipital pole: more posterior part of the brain - Precentral gyrus: the gyrus anterior to the central sulcus - Postcentral gyrus: the gyrus posterior to the central sulcus - Supramarginal gyrus is horseshoe shaped gyrus at the tip of the lateral sulcus/fissure - Angular gyrus is adjacent and inferior to the supramarginal gyrus - Superior temporal gyrus: the most superior gyrus in the temporal gyrus - Heschel's gyrus resides within the temporal lobe on the top leading edge of the lateral sulcus just inside the opercula. Runs the length of the lateral sulcus(?)
what are the types of fiber tracts of the neocortex?
Projection tract Between neocortex and spinal cord or brain stem (can go either way)
Commissural tract Between left and right cortical areas (left and right hemispheres)
Association tract Between cortical areas on same side (within a given hemisphere)
where is the hypothalamus located?
in the inferior portion of the diencephalon
inferiorly, the hypothalamus forms the floor of the third ventricle