Cells and Tissues of The Nervous System Flashcards
How do glial cells contast to neurons?
In contrast to neurones they are non-excitable and are much smaller
How many axons/dendrites does a typical neurone have?
Typically - mutliple dendrites and one axon
Describe the nucleus in a neurone
loose chromatin, prominent nucleolus.
What are the cell organelles within a nerve cell?
Mitochondria, rER( Nissl bodies), diffuse Golgi apparatus.
What is the metabolic rate of a nerve cell?
High
What is the name given to the cytoplasm in the cell body and the axon?
Cell body - perikaryon
Axon - axoplasm
What is special about the life of a nerve cell
Long living and amitotic - meaning the nucleus can divide without mitosis
What part of a neurone can be damaged and will grow back?
Axon can grow back but if the cell body is damaged the loss is irreversible
What is the effect of myelination of axons?
Myelin sheath: Increase conduction speed in axons by ‘saltatory conduction’
Reduces the decay of action potentials
What is the myelin sheath formed by in the central and peripheral nevous system?
Central - oligodendrocytes
Peripheral - Schwann cells
What happens to the cytoplasm of a schwann cell that is wrapped around an axon?
Cytoplasm becomes extruded leaving only the cell membrane
What is the effect of MS on the myelin sheath?
Patchy loss/scarring of myelin sheath (demyelination)à nerve conduction across affected axons abnormal
What is the cause of MS
Unknown
What type of neurones are multipolar?
Interneurones and motor neurones
Where do you find bipolar neurones?
Olfactory mucosa
Retinal nerve fibres
What type of nerve fibres are pseudonipolar?
Sensory neurones
What composes the grey matter of the CNS?
Collection of cell bodies+ non-myelinated axons form grey matter (if diffuse) or nucleii (if localised)
What forms white matter?
Collection of myelinated axons
What are tracts?
Bundles of axons carrying specific information within the white matter
What forms nerves and ganglia?
Nerves - myelinated axons
Cell bodies - ganglia
What are the glial cells of the CNS?
Astrocytes
Oligodendrocytes
Ependymal cells
Microglial cells
What are the glial cells of the PNS?
Scwhann cells
Satellite cells
What is the function of astrocytes?
Chemical concentration maintenance
Waste disposal
Responsible for the blood brain barrier
What is the function of satellite cells of the PNS?
Satellite cells surround sensory and autonomic ganglia and regulate their microenvironment
Which two cell types are responsible for the myelination of nerve axons?
Oligodendrocytes and schwann cells
Outside the CNS, non-myelinated nerve cells are still wrapped by scwann cells but there is no myelin sheath
What is the role of microglial cells?
Ingest cells and pathogens - phagocytosis
Immune function
What is the function of ependymal cells?
Filters blood to produce CSF
What is the brainstem responsible for?
Vital centres eg: cardiorespiratory,
Pathway for fibre tracts
What is the cerebellum responsible for?
Balance and coordiantion
Where is the seat of consciousness?
Cerebrum
What does the nervous system form from?
The neural tube
What are the three primary vesicles that form from the neural tube?
What are the secondary vesicles?
When do the primary and secondary vesicles form?
Primary - week 4
Secondary - week 5
What are ventricles of the brain?
The cavity of the neural tube persists in the adult brain as spaces called ventricles
What do ventricles contain?
CSF
What are the lateral ventricles?
C shaped cavities which lie in the cerebral hemishpheres
Where is the 3rd ventricle?
Within the diencephalon
What connects the lateral ventricles with the 3rd ventricle?
The interventricular foramen
Where does the cerebral aqueduct lie?
In the midbrain
Where does the 4th ventricle lie and what is it shaped like?
Diamond-shaped lies in the hindbrain
Describe the dura mater
Tough and fibrous and has dural folds
Describe the pia mater
Vascularised and dips into the folds of the brain
What is the subdural space?
•The subdural space is a potential space which is traversed by blood vessels penetrating into the CNS
What contains CSF
Subarachnoid space
Where do you find CSF?
Inside the cavity of brain (ie the ventricles) and central canal of spinal cord.
Is also present surrounding the brain and spinal cord in between the layers of meninges which are coverings of the brain (between the pia and arachnoid)
Where is CSF produced?
CSF is produced mainly by a structure called the choroid plexus in the lateral, third and fourth ventricles. CSF flows from the lateral ventricle to the third ventricle through the interventricular foramen
What aids movement of CSF?
The circulation of CSF is aided by the pulsations of the choroid plexus and by the motion of the cilia of ependymal cells
Where is CSF absorbed?
CSF is absorbed across the arachnoid villi into the venous circulation and a significant amount probably also drains into lymphatic vessels around the cranial cavity and spinal canal.
What is the protective mechanism of dural folds?
Protect and support different parts of the brain
Help separate the areas of soft tissue to stop them from rubbing together
What is the falx cerebri?
It is a large, crescent-shaped fold of meningeal layer of dura mater that descends vertically in the longitudinal fissure between the cerebral hemispheres of the human brain.
What is the tentorium cerebelli?
The cerebellar tentorium or tentorium cerebelli(Latin: “tent of the cerebellum”) is an extension of the dura mater that separates the cerebellum from the inferior portion of the occipital lobes.
What is the falx cerebelli?
The falx cerebelli is a small sickle shaped fold of dura mater, projecting forwards into the posterior cerebellar notch as well as projecting into the vallecula of the cerebellum between the two cerebellar hemispheres
What is the diaphragm sellae?
The diaphragma sellae or sellar diaphragm is a flat piece of dura mater with a circular hole allowing the vertical passage of the pituitary stalk. It retains the pituitary gland beneath it in the fossa hypophyseos as it almost completely roofs the fossa hypophyseos of the sella turcica, a part of the sphenoid bone
Which substances does the blood brain barrier prevent entering the brain?
Harmful amino acids and ions present in the blood stream and blood cells
What three things make up the blood brain barrier?
Endothelium - tight junction
Thick basal lamina
Foot process of astrocytes
Where is the blood brain barrier absent?
In a few circumventricular organs: parts of the hypothalamus and posterior pituitary
What type of drugs are able to enter the CNS?
Drugs have to be lipid soluble or use suitable vectors
