Exam 1 Flashcards
Posterior
pertaining to the back
Horizontal/axial/transverse
divides a structure into upper and lower portions
Parts of the Peripheral Nervous System
Sensory: neurons link the sensory receptors of the body surface or interior with the processing circuits of the CNS
Motor: two components
(Somatic and Visceral/Autonomic)
Division of the Peripheral Nervous System
Somatic and Automatic (Sympathetic and Parasympathetic)
By Day ___ post-fertilization, the neural tube is closed and the neural crest cells have broken free
22
Iniencephaly
also an anterior neural tube defect; regions of skull and cervical spine fail to develop along with brain structures
Fatal
Encephalocele:
brain bulges through sac-like opening in skull
Also an anterior neural tube defect
Almost always fatal
Retinoic Acid Exposure
what specific area?
retinoic acid is anti-anterior/anti-brain; too much retinoic acid during the wrong part of development can lead to loss of forebrain structures
Holoprosencephaly:
-reason for it?
failure of the prosencephalon to develop into two hemispheres; sometimes the result of Sonic Hedgehog (Shh) defects
- I think it is an example of something that can go wrong during nervous system development
Medulloblastoma
progenitors keep dividing after they should stop; leads to uncontrolled granule cell proliferation; often a result of a Shh defect
human brainstem includes:
the midbrain, pons and medulla
Spinal Cord: Gray matter vs White matter
Gray matter= cell bodies (central)
White matter= axons (external)
Spinal Cord: Dorsal vs Ventral
Dorsal= mostly sensory information Ventral= motor neurons
Cerebrospinal Fluid
- description
- function (3)
- produced by:
- found in:
- Clear liquid
- Helps to cushion (brain and spinal cord)
- Supplies nutrients (to the nervous tissue)
- Helps to remove waste products
- Produced continuously by the choroid plexus in the ventricles
- Found in your ventricles, central canal, and the subarachnoid space
Flow of Cerebrospinal Fluid
1) lateral ventricles
2) Foramen of Monro
3) Third ventricle
4) cerebral aqueduct
5) Fourth ventricle
6) forman of Lushka and Magendie
7) Subarachnoid Space
8) arachnoid vilia and then to venous drainage system of brain
Choroid Plexus
- made of:
- vascularization?
- Way understudied
- Found in ventricles and next to the pia mater
- Highly vascularized
- Made of epithelial cells + Also contains immune cells
- Makes your CSF!
- Develops from the dorsal neural tube: First in and with 4th ventricle, then in the lateral ventricles of the telencephalon, and then in and with the 3rd ventricle
Ventricles and location
- Two lateral ventricles- one in each cerebral hemisphere
- Third ventricle- at the midline near the ventral portion of the brain
- Fourth ventricle- within the brainstem, roughly between the pons and medulla; connects to central canal of the spinal cord
*Central Canal- not a ventricle, per se, but basically a spinal cord ventricle that runs down the middle of it
Hydrocephaly/Hydrocephalus
- too much CSF
- -Causes include trauma, meningitis, infection, blockage in CSF drainage pathways, and birth defects
Too Little CSF
-reasons
- Usually means you sprung a CSF leak somewhere or are severely dehydrated
- bad because : Brain does not have enough cushion. It can also cause the brain to sag, stressing nerves and meninges
Too Little CSF
- Usually means you sprung a CSF leak somewhere or are severely dehydrated
- bad because : Brain does not have enough cushion. It can also cause the brain to sag, stressing nerves and meninges
Choroid Plexus Pathologies (5)
- Cysts- common with certain disorders
- Hemorrhages- often due to birth trauma/stress/hypoxia
- Tumors and Hyperplasia- often lead to hydrocephalus
- Microorganism infiltration- seen in children who have meningitis
- Deficiencies in thyroid hormone carrier protein (thus depriving brain regions of thyroid hormone)
- Perhaps involved in Alzheimer’s disease- CSF helps to clear plaques and choroid plexus appears atrophied in those with the disease
Meninges Functions
- Provide asupportive frameworkfor the cerebral and cranial vasculature.
- Acting with cerebrospinal fluid to protectthe CNS from mechanical damage.
The singular of meninges is ______
meninx
3 layers of Meninges
The delicate inner layer is the pia mater. The middle layer is the arachnoid, a web-like structure filled with fluid that cushions the brain. The tough outer layer is called the dura mater
dura mater: def and characteristics
-also known as
- theoutermostlayer of the meninges
- Directly underneath the bones of the skull and vertebral column
- Thick, tough, and inextensible
- Fits brain like a loose bag
- Also known as the pachymeninx
- Continuous with the periosteum
dura mater contains…
Within the cranial cavity, the dura contains two connective tissue sheets:
- Endosteal (Periosteal) layer– Lines the inner surface of the bones of the cranium; does not extend through foramen magnum
- Meningeal layer– Lines the endosteal layer inside the cranial cavity. (The only layer present in the vertebral column)
- Between these two layers, thedural venous sinusesare located: Responsible for the venous vasculature of the cranium, draining into theinternal jugularveins.
dural reflections
-purpose?
In some areas within the skull, the meningeal layer of the dura mater folds inwards asdural reflections.
They partition the brain and divide the cranial cavity into several compartments.
Meningeal Spaces
Epidural – contains meningeal arteries & veins
Subdural – traversed by “bridging” veins
Subarachnoid -communicates with ventricles, includes cisterns, contains CSF, circle of Willis
Meningeal Spaces
- Epidural – contains meningeal arteries & veins
- Subdural – traversed by “bridging” veins
- Subarachnoid -communicates with ventricles, includes cisterns, contains CSF, circle of Willis
Dura Mater: A haematoma can cause a rapid increase in ______. Death will result if untreated.
intra-cranial pressure
There are two types of haematomas involving the dura mater:
- Extradural– Arterial blood collects between the skull and endosteal layer of the dura. The causative vessel is usually the middle meningeal artery, tearing as a consequence of BRAIN TRAUMA.
- Subdural– Venous blood collects between the dura and the arachnoid mater. It results from DAMAGE TO CEREBRAL VEINS as they empty into the dural venous sinuses.
Arachnoid Mater/Layer
- surrounds?
- lines the brain?
- vascular?
- innervation?
*Middle layer of the meninges, lying directly underneath the dura mater
*Surrounds both the brain and spinal cord
*Does not line the brain into the sulci, with exception of longitudinal fissure
*Avascular (!!)
*Does not receive any innervation.
Web of collagen
It consists of layers of connective tissue
Dorsal layer covers internal cerebral veins and fixes them to the surrounding tela choroidea
Ventral layer of arachnoid membrane is a direct anterior extension of this arachnoid envelope that the dorsal layer forms over the pineal region
*Underneath the arachnoid is a space known as thesub-arachoid space. - It contains cerebrospinal fluid, which acts to cushion the brain.
Small projections of arachnoid mater into the dura(known asarachnoid granulations)allow CSF to re-enter the circulation via the dural venous sinuses.
Subarachnoid Hemorrhage
Between arachnoid and pia
Thunderclap headache
Photophobia
Pia Mater
- location
- description
- follows the brain?
- vascularization?
- Located underneath the sub-arachnoid space.
- Very thin andtightly adheredto the surface of the brain and spinal cord.
- It is the only covering to follow the contours of the brain (the gyri and fissures)
- Highly vascularized, with blood vessels perforating through the membrane to supply the underlying neural tissue.
Leptomeninges
- “Thin meninges”
- Arachnoid + Pia
- 5% of cancer patients will have their cancer spread to the leptomeninges
- CNS symptoms are divided into the following 3 anatomic groups:
- Cerebral involvement: Headache, lethargy, papilledema, behavioral changes, and gait disturbance.
- Cranial-nerve involvement: Impaired vision, diplopia, hearing loss, and sensory deficits, including vertigo; cranial-nerve palsies commonly involve CN III, IV, VI, VII, and VIII
- Spinal-root involvement: Nuchal rigidity and neck and back pain, or invasion of the spinal roots.
Meningitis
-causes
- Inflammationof the meninges.
- Can be drug induced: Nonsteroidal anti-inflammatory drugs, antimicrobials, intravenous immunoglobulin, intrathecal agents, vaccines
- Usually caused by pathogens: Bacteria are the most common infective cause. The most common organisms areNeisseria meningitidisandStreptococcus pneumoniae.
The immune response to the infection Meningitis causes_____, consequently raising intra-cranial pressure. This has two main effects:
cerebral edema
1) cranial herniation: Part of the brain can be forced out of the cranial cavity
2) In combination with systemic hypotension, raised intracranial pressurereduces cerebral perfusion.
* Both of these complications rapidly result in death
-net pressure gradient causing cerebral blood flow to the brain
Blood-Brain Barrier: Def
-regulation by :
*An organic barrier between circulating blood and the CNS
*Regulates, in part actively and in part passively, the exchange of substances between blood and the brain.
*Also acts as a protective shield by preventing the penetration of harmful substances into the CSF.
Few pathogens can overcome the blood-brain-barrier.
Blood-Brain Barrier: allows vs prevents
- Allows passage/transport of small molecules (H2O, O2, CO2), lipophilic molecules (EtOH, heroin), passive transport of glucose, active transport of amino acids/NT precursors
- Prevents passage of larger molecules (dopamine), charged molecules, etc
- Medications can be tailor-made in order that they can overcome the blood-brain barrier.
Blood-Brain Barrier: passage
- Allows passage/transport of small molecules (H2O, O2, CO2), lipophilic molecules (EtOH, heroin), passive transport of glucose, active transport of amino acids/NT precursors
- Prevents passage of larger molecules (dopamine), charged molecules, etc
- Medications can be tailor-made in order that they can overcome the blood-brain barrier.
3 Main Functions of Blood-Brain Barrier
*Protects the brain from “foreign substances”in the blood that may injure the brain.
*Protects the brain from hormones and neurotransmittersin the rest of the body.
Maintains a constant environmentfor the brain.
Components of the BBB
- The filter is primarily made up of endothelial cells, which surround the blood capillaries, and from the ends of astrocytes, which have important structural and metabolic functions
- In most parts of the body, capillaries are lined with endothelial cells.
Endothelial tissue has small spaces between each individual cell so substances can move readily between the inside and the outside of the vessel.
However, in the brain, the endothelial cells fit tightly together and substances cannot pass out of the bloodstream.
What Can Open the Blood-Brain Barrier
Hypertension (high blood pressure) Hyperosmolality Microwaves Radiation Infection Trauma, Ischemia, Inflammation, Pressure *Development: the BBB is present, but may be not fully formed at birth.
Circumventricular Organs
-vascularized?
- Highly vascularized with fenestrated capillaries
- Lack a traditional BBB
- Permit polypeptide hypothalamic hormones to leave the brain without disrupting the BBB
- Permit substances that do not cross the BBB to trigger changes in brain function
- Mammalian examples: median eminence and adjacent neurohypophysis, organum vasculosum lamina terminalis (supraoptic crest), subfornical organ (ventral fornix), and the area postrema (vomiting center).
Frontal Lobe functions
Cognition Problem-solving Language Expression of emotion Contributes to learning and memory Motor function (important part of the telencephalon)
Superior frontal gyrus function
: executive processing in working memory (du Boisgueheneuc et al, 2006), laughter, executive processing for attention, motor control (supplementary motor area)
Middle frontal gyrus:
orienting attention, literacy and numeracy
Inferior frontal gyrus
: language processing and speech (contains Broca’s area)
Broca’s Area
In short, it is responsible for language production (but this not the whole story, not just as simple as make it out to be)
Broca’s Aphasia
-also known as
- Also known as expressive aphasia
- Results from damage to Broca’s area
- Individuals lose their ability to produce language: spoken and written
- Can happen to varying degrees: Some can make sentences, but leave words out (usually prepositions, articles, etc) + Some can only speak single word sentences
- The person knows what they are trying to say, but have difficulty getting the words out
- Comprehension is generally intact
Precentral gyrus
-tracts that oringiate from here
-also known as the primary motor cortex
The corticospinal tract, corticobulbar tract, and cortico-rubrospinal tract all originate from the precentral gyrus
Contains upper motor neurons
Large motor neurons that send their axons out of the brain to places like the spinal cord
Lateral (Sylvian) Fissure
lateral sulcus, the Sylvian fissure is a large sulcus that separates the temporal lobe from the frontal and parietal lobes.
Division of the Temporal Lobe
-Lateral (Sylvian) Fissure
1- Superior Temporal Gyrus
(Superior Temporal Sulcus is between 1 & 2)
2- Middle Temporal Gyrus
(Middle Temporal Sulcus is between 2 & 3)
3- Inferior Temporal Gyrus
(labeling)
Superior temporal gyrus function
auditory association cortex; includes Wernicke’s area
Middle temporal gyrus
participates in visual associations- word meanings and facial recognition
Inferior temporal gyrus
object processing, visual speech processing, some roles in visual association/processing
Wernicke’s Aphasia
Damage to this region leads to production of speech that lacks meaning
Words and sentences are produced fluidly, but the words do not connect and no complete thought can be derived from this speech
Parietal Lobe
either of the paired lobes of the brain at the top of the head, including areas concerned with the reception and correlation of sensory information.
The parietal lobe, posterior to the central sulcus, is divided into three parts: (1) the postcentral gyrus, (2) the superior parietal lobule, and (3) the inferior parietal lobule. The postcentral gyrus receives sensory input from the contralateral half of the body.
- intrapareital sulcus
- angular gyrus
- supramarginal gyrus
Parietal Lobe parts
The parietal lobe, posterior to the central sulcus, is divided into three parts: (1) the postcentral gyrus, (2) the superior parietal lobule, and (3) the inferior parietal lobule. The postcentral gyrus receives sensory input from the contralateral half of the body.
- post central gyrus
- intrapareital sulcus
- angular gyrus
- supramarginal gyrus
Supramarginal gyrus
- part of the somatosensory association cortex; helps you figure out where your limbs are in space; important part of the mirror neuron system
- (part of the parietal lobe)
Mirror Neuron System
- Neurons fire not only when you perform an action, but also when you see someone else perform an action (or even if you hear it)
- Believed to play a role in helping you learn behaviors, including speech
- May also play a role in empathy
Insula
Located deep in the lateral sulcus
Believed to play a role in self-awareness and consciousness
Also plays a role in things like taste preference, empathy, emotion
Basal Ganglia
Not ganglia
Definitely basal
Most known for role in movement
Functions not limited to movement
Amygdala
*Primary role in processing and memory of emotional reactions, particularly fear.
*Can act as ‘thinking bypass’, triggering automatic reactions.
*In a fearful situation, sensory stimuli –> basolateral amygdala–> form associations with memories of the stimuli –> fear responses (freezing, increased heart rate and the release of stress hormones)
*Damage: disrupts the ability of an emotionally charged stimulus to elicit an unconscious emotional response
*Remove amygdala: lose their ability to fear and recognize anger in others
Electrical activation: feelings of fear and apprehension
*Also involved in the process of forming long-term memories
Hippocampus
Mostly gets credit for role in learning and memory
white matter different types
- Association fibers – cortical to cortical connections ipsilaterally
- Commissural fibers – cortical to cortical (mostly) connections running contralaterally
- Projection fibers – cortical to subcortical connections
Association fibers (white matter) function
cortical to cortical connections ipsilaterally
Thalamus general def
The largest part of the mammalian diencephalon
*Receives all sensory information, with the exception of olfaction, first
The major relay to the neocortex
“Gateway” to cortex
Each major area of the neocortex depends on a defined thalamic group
Details differ for each species, but general relationships apply to all mammals
Dividing up the Thalamus
- By Projections/Circuitry: Relay, Association, and Non-specific nuclei
- Dorsal vs Ventral
Types of Relays
First Order, Higher ORder
Dorsal Thalamus
-Largest part of the thalamus and also largest part of diencephalon by itself
-Major efferents: telencephalic structures
(Mostly neocortex, weak striatal connections)
-Relay cells with axons to telencephalon
-Basically, lots of connections back and forth with cortex
-All connections are ipsilateral
-No known communication between thalamic nuclei directly, except the reticular nucleus
division of the dorsal thalamus
External medullary lamina- a layer of axons (white matter) that covers the dorsal thalamus on the lateral sides
Includes fibers coming to and from the cortex
The cells of the reticular nucleus reside here
Internal medullary lamina- white matter fibers that subdivide the thalamus into anterior, medial, lateral, midline, and intralaminar nuclear groups
Dorsal thalamus subdivision
Anterior Medial Lateral Midline Intralaminar
-by the internal medullary lamina
Ventral Thalamus division
Subthalamus, Reticular Nucleus of the Thalamus +++++
Reticular Nucleus of the Thalamus
*Homogenous neurotransmitter phenotype- GABA
*Receives excitatory branches from corticothalamic/thalamocortical axons and send inhibitory axons to other parts of the thalamus: Each circuit sends to and from through the same part of reticular nucleus
*Role in adjusting messages based on attentive state of the whole animals (wake/sleep) and salience (threat/no threat)
Strategically placed over the axons being sent between thalamus and cortex
Epithalamus: parts
Pineal gland and Habenular nuclei
Pineal gland
- in the Epithalamus
contains modified photoreceptor cells (pinealocytes)
Release melatonin in a circadian rhythm
Do not respond directly to light in humans
Respond to circadian differences in sympathetic nervous system activity
Sleep-wake cycle
Sexual maturation?
what happens by day 22 of development
By Day 22 post-fertilization, the neural tube is closed and the neural crest cells have broken free
Does the arachnoid layer of the meninges line the brain into the sulci?
Does not line the brain into the sulci, with exception of longitudinal fissure
t/f extradural and subdural hematoma are more gradual headaches
I think true
does the brain get compressed more in an extradural or subdural hemorage?
i think the extradural
how do amino acids/NT precursors get through the BBB?
active transport
