Cells and Tissues of the CNS (anatomy based) Flashcards
What makes up the CNS?
Brain and spinal cord
What makes up the peripheral nervous system?
12 pairs of cranial nerves
33 spinal nerves
Information carried by the nervous system can be motor or sensory. Name the two divisions of motor information.
Autonomic (sympathetic and parasympathetic)
Somatic
How are impulses carried in neurons?
As action potentials
Name the two types of cells in the nervous system.
Neurons
Glial cells
Which cells are excitable; neurons or glial cells?
Neurons
Which cells are bigger; neurons or glial cells?
Neurons
Which cells are of greater quantity; neurons or glial cells?
Glial cells
Neurons have a high metabolic rate and contain many mitochondria, RER and Golgi apparatus.
What can neurons produce?
Neurotransmitters
Describe what happens to the neurotransmitter when produced by the neuron.
Travels down axon and is stored in the synaptic terminals.
The neurotransmitter will be released once an action potential reaches it.
Perikaryon?
Cytoplasm in cell body of neuron
Axoplasm?
Cytoplasm in the axon of a neuron.
What happens if you lose a neuron?
They are not replaced. Neurons last your whole life, lose one, lost it forever.
Name three common types of neurons.
Multipolar (typical neuron you would imagine).
Bipolar
Pseudounipolar
Name two types of multipolar neuron.
Interneurons
Motor neurons
Name two types of bipolar neurons.
Olfactory mucosa
Retinol nerve fibres
Name a type of pseudounipolar neurons.
Sensory neurons
In which crnails nerve would you find bipolar neurons?
CN I
CN II
->think about it, they tend to be olfactory mucosa and retinol fibres so would make sense it’s the olfactory and optic cranial nerves.
Describe the direction of nerve impulses in multipolar neurons.
Impulse travels from the dendrite to cell cell body and then down the axon.
Describe the direction of nerve impulses in pseudounipolar neurons.
Impulse travels down dendrite, bypasses cell body and goes straight down the axon.
Where would you find the cell bodies of the multipolar neurons?
Always in the CNS (either brain or spinal cord)
What does a myelin sheath do?
Increases the conduction of action potentials
What is meant by saltatory conduction?
Action potential jumps from none node to another without having to travel through the entire neuron hence speeding up the rate of conduction.
Which cells secrete the myelin sheath in:
1. CNS
2. PNS
?
- Oligodendrocytes
- Schwann cells
If a neuron does not have a myelin sheath, what is this known as?
Non-myelinated neuron
Why is Multiple Sclerosis (MS) caused?
Believed it is caused by patchy loss of the myelin sheath as the body’s immune system attacks it’s own tissues.
These patchy myelin sheaths effect conduction of action potentials.
Describe the arrangement of white and grey matter of the spinal cord.
Peripheral white matter
H shaped grey matter in middle.
What is found in :
1. white matter
2. grey matter
- Myelinated axons
- neuronal cell bodies
Is the dorsal root motor or sensory?
Sensory
Is the ventral root motor or sensory?
Motor
What is the function of ascending tracts of the spinal cord?
Carry information up the spinal cord from the body to the brain.
Do ascending tracts of the spinal cord carry motor or sensory information?
Sensory
What is the function of descending tracts of the spinal cord?
Carry information down the spinal cord from the brain to the body.
Do descending tracts of the spinal cord carry motor or sensory information?
Motor
RECAP- where does the
1. dorsal ramus supply
2. ventral ramus supply
- Posterior trunk
- Anterior trunk and limbs
If you see an area of the brain and it looks grey, what does that means about it’s composition?
Lots of unmyelinated neuronal cell bodies
->myelinated cell bodies=white structure
What is the name given to a collection of neuronal cell bodies, which is sitting outside of the central nervous system?
Ganglion
What is the name given to a collection of neuronal cell bodies, which is sitting inside of the central nervous system?
Nucleus
Which type of glial cell is the most populous within the CNS?
Astrocytes
Describe astrocytes.
Look like an asteroid!
Have central nucleus with many processes surrounding it- these are known as endfeet.
What is the function of astrocyte endfeet?
They surround synapses and capillaries and help with potassium buffering.
What is the function of microglia, another type of glial cell?
Phagocytosis and scar tissue formation.
Which type of glial cell helps to maintain the blood brain barrier?
Astrocytes
Why does the brain need microglia to enable phagocytosis when the rest of the body has other cells, like WBCs, that do this?
Blood brain barrier prevents white blood cells from moving in the capillaries of the brain so brain needs own cells for the process of phagocytosis.
Where would you find ependymal cells, another type of glial cell?
Lining the ventricles of the brain
Lining canal of spinal cord
What is the function of oligodendrocytes? (another type of glial cell).
Secrete myelin sheath of axons in the CNS.
Name the four types of glial cells in the CNS.
Astrocytes
Microglial
Ependymal cells
Oligodendrocytes
Name the two types of glial cells of the PNS.
Schwann cells
Satellite cells
What is the function of schwann cells?
Secrete myelin sheath of axons in the PNS.
Where are satellite cells found?
Inside neuronal cell bodies
What are more common- gliomas (tumours of glial cells) or neural brain tumours?
Glioma
What is the blood brain barrier?
Protective mechanism creating a stable environment for the brain as prevents certain molecules from entering the brain.
What does the blood brain barrier prevent coming into the brain?
Harmful amino acids and ions
Glucose
What makes up the blood brain barrier?
- Endothelium- tight junction
- Thick basal lamina
- Foot processes of astrocytes
Because of the blood brain barrier, what are the only substances that can go across the capillaries of the brain?
Lipid soluble substances e.g. water and oxygen.
The brain needs glucose and amino acids, despite the blood brain barrier preventing them to flow into the brain.
Therefore, how do these substances get into the brain?
Pump mediated transfer
Which parts of the brain are not surrounded by the blood brain barrrier?
Hypothalamus
Posterior pituitary
->both endocrine
Due to the blood brain barrier, if wanting to use drugs which will affect the brain, what will need to be considered?
They will need to be able to pass over the BBB so will be lipid soluble or use suitable vectors to get them across.
What does the cerebrum control?
‘Seat of consciousness’
e.g. initiates and coordinates movements, controls temperature.
What does the cerebellum control?
Balance
Coordination
Name the three components of the brainstem.
Midbrain
Pons
Medulla
What would be found in the brainstem?
Vital automatic centres e.g. cardio-respiratory centres
What would you find in the subarachnoid space (space between arachnoid mater and pia mater)?
Cerebrospinal fluid
Name the fold of dura mater which separates the two cerebral hemispheres.
Falx cerebri.
Name the fold which separates the two cerebral hemispheres from the cerebellum.
Tentorium cerebelli.
What are the ventricles of the brain?
Spaces within the brain- they are all connected
Where do the lateral ventricles lie?
Cerebral hemispheres
Where does the cerebral aqueduct lie?
Midbrain
Where does the diamond shaped 4th ventricle of the brain lie?
Hindbrain
What connects the lateral ventricles with the 3rd ventricle?
Interventricular foramen
Where is the 3rd ventricle found?
Diencephalon
What is found in the brain ventricles?
Cerebrospinal fluid
What are meninges?
Coverings of the CNS
Name the three layers of the meninges.
Dura mater
Arachnoid mater
Pia mater
What is the function of CSF?
Maintains intracranial pressure
Protects brain and spinal cord
Where would you find CSF?
Brain ventricles
Subarachnoid space
What forms CSF?
A structure called the choroid plexus found in each ventricle
Where is CSF absorbed?
By arachnoid villi into the sagittal sinus (this is the venous drainage for the brain).
How does CSF leave the ventricular system and get to the subarachnoid space?
Leaves through three holes at the roof of the 4th ventricle.