Histo of NS Flashcards
What are the most common types of cells in the CNS?
Multipolar cells
* Multipolar neurons have a # of dendrites and they all have one axon, so often they have a faily complicated dendritic tree.
-Multipolar cells are able to communicate with a # of different cells but they all just have one axon
Pseudounipolar neuron
- Have cell bodies in the dorsal root ganglion, just outside the spinal cord
- All sensory
- One axon, no dendrites
- Part of axon acts as a functional dendrite
Examples of each type of neuron
Pseudounipolar= touch receptors
Bipolar= photorecepetors (retina), olfactory receptors (olfactory epithelium)
Interneurons= neurons that are found between 2 other neurons
Intergrative neurons= Pyrimidal, purkinje cells, and interneurons
Pyrimidal cells, purkinje cells, and interneurons are what type of neuron?
Integrative
Explain the process of intergrative neurons
- Integrative means that they do not directly receive sensory input and they also do not synapse ona specific target.
- They are basically sitting in the middle and receive input from a lot of sensory neurons and intergrate all of the info and then provides an output to the motor neuron.
Neuroendocrine cell
Secretes hormones into bloodstream, so it ends in lots of capillaries
What the two types of glia cells?
- Microglia
- Macroglia
- Myelin forming cells
- Shwann cells (PNS)
- Oligodendrocytes (CNS)
- Supporting cells
- Astrocytes (CNS)
- Satellite cells (PNS)
- Myelin forming cells
When do microglia develop?
Microglia invade the brain during fetal development and maintains residence in the parenchyma
- They typically just sit in the nervous sytem until there is injury
Function of microglia
- Responsible for response to injury or trauma in brain by proliferation and phagocytosis of debris
Characteristics of microglia
- Small cells with delicate processes, inconspicuous in H&E stained section
- Migrate actively
- Derived from monocytes incorporated into CNS during development
- Mediate response to injury by proliferating, migrating to site of injury, and removing debris by phagocytosis
- Important in neuropathology
How is the action of microglia implicated in Alzheimer’s disease?
- During injury, microglia undergo a burst of mitotic activity and then this proliferation is followed by apoptosis, which will reduce the cell numbers back to basline. This puts a bit of toll on the metabolism of the system.
- If there is minor neuronal damage that occurs with normal aging, it can transform microglial cells into enlarged and activated microglia. these chronic increases in microlial activation contribute to an increased risk of conditions like Alzheimer’s disease.
- Constant neuronal damage favors plaque formation in susceptible patients.This is a long term effect of microglial activation
Microglia are derived from ____________.
Monocytes
Schwann cells are derived from the ____________
Neural crest
Aside from myelination, what are addition functions of Schwann cells?
- Can act as phagocytes
- Produce cytokines
Which types of glia cells are found in the CNS?
Astrocytes
Oligodendrocytes
Microglia
Ependymal cells
Which types of glia cells are found in the PNS?
Schwann cells
Satellite cells
What are the functions of astrocytes?
- interface between neurons and pia, ependyma, blood vessels
- provide structural support
- take up neurotransmitters
- regulate ionic balance
- guide axons during development (radial glia)
- immune response
- pathology: form glial scars after CNS injury
Which type of astrocyte guide axons during development?
Radial glia
Astrocytes communicate with each other and with neurons via __________________.
Gap junction
What are the two types of astrocytes?
Fibrous and protoplasmic
*Astrocytes line the nervous system. If you were to take a pin and poke into the head and get through the skin, skull, meninges, and everything you would really toucj an astrocyte before you got to a nerve
What is unique about satellite cells?
Satellite cells are resticted to ganglia
NOTE: Satellite cells surroung the cell bodies in the dorsal root ganglionn
What are the functions of ependymal cells?
- Produce CSF
- Line ventricles in brain and central canal in spine
What type of epithelial cells make up ependymal cells?
Cuboudal or columar epithelial cells
Ependymal cells are remnants of _______________
Embryonic neuroepithelium
Ependemyal cells are made up of what type of filaments?
Microvilli and cilia
- Function to help move CSF
If a person has a CNS injury, what action would astrocytes take?
- If a person has a CNS injury, typically what happens is the neuron that has been damged changes its morphology and its form, so a presynaptic terminal may retract from the damaged neuron.
- The astrocytes come in and for a scar around the axon terminal so that the presynaptic neuron cannot form a function synapse to the damaged posynaptic neurons.
Astrocytes form end- feet on ____________, __________, and _____________.
Basal lamina
Capillaries
Ependymal (that line the ventricles)
Multiple sclerosis
- Demyelination disease
- Affects oligodendrocytes in the CNS and can affect sensory as well as motor neurons and that is reflected in the symptoms that manifest themselves in MS
Nissl bodies are found in the _________ and are found in large dendrites.
Perikaryon
What is the general course of sensory neurons?
Sensory neurons have cell bodies in the dorsal root ganglion and then they send their axon through the dorsal root and into the spinal cord with the cell bodies and dendrites and synapses of the gray matter.
What is the general course of motor neurons?
Motor neurons have their cell bodies in the brainstem or spinal cord. They leave the spinal cord through the ventral root and become a spinal nerve
Cluster of cell bodies in CNS=___________
Cluster of cell bodies in PNS=__________
Cluster of axons in CNS=__________
Cluster of axons in PNS=_____________
Nucleus
Ganglion
Tract
Nerve
Somatic nervous system
•Voluntary motor and sensory components
Autonomic nervous system
Involuntary control of viscera
- Sympathetic system
- “fight-or-flight; thoraco-lumbar
- Parasympathetic system
- “steady-state”; cranio-sacral
What is the difference between somatic and autonomic motor neurons?
Somatic motor neuron
- Cell bodies in ventral root and leave the spinal cord and synapse directly on the skeletal muscle
Autonomic Motor Neuron
- Synapses first at an autonomic ganglion
- You have preganglionic neuron that is typically myelinated and then you have a postganglionic neuron and it will synapse on smooth muscle glands or cardiac muscle.
Postganglionic neurons synapse on ____________, ____________, and______________.
Cardiac muscle, smooth muscle, and glands
How do somatic and autonomic sensory neurons differ?
They don’t. In both cases, they come directly from the receptor and go all the way to the CNS, with NO ganglion in between.
What are the two layer of the dura mater? What is the space between the two layers called?
The dura mater, divided into periosteal and meningeal, is found all around the brain and there is a space between the two and is referred to as the dural sinuses.
Once the menigeal layer separates from the periosteal layer what happens?
The menigeal layer separates from the periosteal layer and goes down into the longitudinal fissure and forms the falx cerebri
Which sinus is the largest dural sinus?
The superior sagittal sinus is the largest dural sinus is is filled with blood
Role of the arachnoid villus
Allows the CSF to exit the brain and get into the blood stream
* Normally the pressure of the CSF is higher than that of the venous system, so CSF flows through the villi and granulations into the blood
Falx Cerebelli
a small triangular process of dura mater, received into the posterior cerebellar notch and runs along the vermis
Tentorium cerebelli
Lies in the transverse fissure and is a horizontally oriented extension of the dura mater. It separates the cerebellum from the inferior portion of the occipital lobe.
The straight sinus is found underneath the _____________.
Occipital lobe
Pia mater + arachnoid =___________
Leptomeninges
What role do astrocytes play in forming the blood-brain barrier?
The astrocyte end-feet encircling endothelial cells of blood vessels
Endothelial cells of blood vessels are connect to each by _____________.
Tight junctions
*This means that there is relatively little movement across the endothelial cells for some molecules. The BBB is highly selective
___________ are the most abundant glial cells of the CNS.
Astrocytes
Types of capillaries
Fenestrated, sinusoidsm continuous
What is the difference between capillaries in the brain vs in the rest of the body?
Capillaries (in general)
- Fenestrated
- Intact basal membrane
- Alot of potential for transport across the endothelium, so there are a lot of pinocytic fluid-filled vesicles
Capillaries (brain)
- Astrocytes
- Pericytes
- Basal membrane not intact
- Tight junctions
- Mitochondria
What are the 3 components of the BBB?
Endothelium
Pericytes (muscle-like cells)
Astrocytes
Basement membrane of the basal membrane
What role do pericytes play in BBB? Where are they found?
Pericytes are found in the basement membrane. They are responsible for:
- Tight junction formation
- Vesicle trafficking among endothelial cells
- Inhibiting the effects of the CNS immune cells (which can damage the barrier)
What are the two major types of blood-brain barriers?
- Blood-ECF
- Blood-CSF
The blood-ECF barrier is in the ___________ and the blood-CSF barrier is in the ____________.
CNS capillary bed
Choroid plexus
The blood-CSF barrier is made up of ______________ covered by __________ and __________.
Capillaries; pia mater; ependyma
What is unique about the ependymal cells found in the Blood-CSF barrier?
- Cilia are replaced by microvilli
- They have numerous enzymes specifically involved in the active transport of ions and metabolits
- There is a basement membrane beneath the epithelium
- Tight junctions are present between the ependymal cells at the apices
The tight junctions that join the endothelial cells of the BBB are of high _____________.
Electrical resistance
Which type of molecules can pass through the BBB?
Fat solube molecules like alcohol, nicotine, and anestetics
____________ transports glucose to the brain.
GLUT-1
NOTE: There is decreased expression of these transporters during Alzheimer’s disease. This may be due to lower metabolic requirement of the brain after the brain experiences extensive neuronal loss, so you don’t need as much glucose and you have fewer transporters.
Choroid plexus
- Mediates the production of cerebrospinal fluid
- Major source of transferrin secretion that plays a part in iron homeostasis in the brain.
- Consists of higly specialized tissue and villi and is projecting in to 4 ventricles of brain.
- It is found in the roof of ventricles 3 and 4 and in parts of the two lateral ventricles
What is the process of transformation of blodd plasma to CSF?
- Blood is converted into CSF via filtrate formation
-
This transformation occurs in the capillaries
- The filtrate that is formed has glucose, oxygen, vitamins,etc. and is put out into the ventricles
-
This transformation occurs in the capillaries
NOTE: Waste and other unwanted material can also move the opposite direction out of the cavity of the ventrical. Ependymal cells absorb waste.
What are the layers of the choroid plexus?
The choroid plexus consists:
- A layer of cuboidal epithelial cells surrounding a core of capillaries and loose connective tissue.
- The epithelium of the choroid plexus is continuous with the ependymal cell layer that lines the ventricles.
- The cells of the choroid plexus are non ciliated and has tight junctions between the cells on the side facing the ventricle.
- The choroid plexus folds into many villi around each capillary, creating frond-like processes that project into the ventricles.
- The villi, along with a brush border of microvilli, greatly increases the surface area of the choroid plexus.
- The choroid plexus consists of many capillaries, separated from the ventricles by choroid epithelial cells.
What are the major differences between the plasma and the CSF?
- There are virtually NO PROTEIN that makes it into CSF
- pH is lower is CSF
What is the BBB permeable to? What is it not permeable to?
Permeable to
- Water
- non-ionised lipid soluble substances
- ethanol
- caffeine
Not permeable to
- protein
- protein-bound substances (Drugs, hormones)
- strongly hydrophilic (water soluble) substances (Na, K)
- use of specialised carrier-mediated transport mechanisms
The neurons and neuroglia are surrounded by _______ and __________ is in the ventricles of the brain.
ECF; CSF
What is the flow of CSF?
- Lateral ventricle
- Interventricular foramine (foramen of Monroe)
- Third ventricle
- Supraoptic recess of 3rd ventricle
- Infundibular recess of 3rd ventricle
- Cerebral aqueduct
- Fourth venricle
- Foramen of Luschka (lateral) & Magendie (medial)
- Subarachnoid space
Circumventricular organs (CVOs)
Structures that permit polypeptide hypothalamic hormones to leave the brain without disrupting the blood-brain barrier (BBB) and permit substances that do not cross the BBB to trigger changes in brain function.
*CVOs are outside of the BBB are are hence expose to blood
Circumventricular organs can be classified into __________ organs and ___________ organs.
Sensory; Secretory
Sensory organs
- Area postrema (AP)
- Body fluid homeostasis, emetic physiology
- The subfornical organ (SFO)
- Thirst-regulating
- The organum vasculosum of lamina terminalis (OVLT)
- Fluid and electrolyte balance
Secretory organs
- Subcommissural organ (SCO)
- Secretes various glycoproteins into CSF
- The posterior pituitary (i.e., neurohypophysis)
- Secretes vasopressin and oxytocin into the blood
- The pineal gland
- Mediates circadian rhythms; melatonin
- The median eminance
- Hypophysiotrophic hormones converge here before they are conveyed to the pituatary gland
- The intermediate lobe of the pituitary
