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.