Cells and tissues of the nervous system Flashcards
What makes up the CNS
Brain and spinal cord - control centres for whole nervous system
what makes up PNS
Cranial and spinal nerves
conduits - carry impulses from CNS to peripheral organs and structures
Division of PNS?
sensory afferent (to CNS) or afferent (motor) division (CNS to PNS)
Somatic motor function
skeletal muscle - voluntary movements
Autonomic division
sympathetic or parasympathetic (involuntary movements)
The entire nervous system is made up of which 2 types of cells?
neurons
glial cells
What is a neuron
excitable cells that carry impulses in form of AP’s
structural and functional unit of the nervous system
What are glial cells?
Supportive cells - non-excitable
much smaller than neurons and more of them
Describe a typical neuron
- Has multiple dendrites and one axon
- Nucleus- loose chromatin, prominent nucleolus.
- High metabolic rate
- Long living and amitotic - don’t regenerate
- Cytoplasm in the cell body is perikaryon and in the axon is axoplasm
An impulse transmission is by AP which can travel in only one direction from cell body to synaptic terminal
What does a myelin sheath do?
Increases conduction speed of AP in axons by ‘saltatory conduction’ (jumping from node of Ranvier to node of Renvier)
Myelin sheath is just the cell membrane of the axon - fatty - appears white (white matter)
What forms a myelin sheath in the PNS?
schwann cells (type of glial cell)
What forms a myelin sheath in the CNS?
oligodendrocytes (type of glial cell)
Types of neurons?
Multipolar - typical neuron, branches of lots of dendrites
Bipolar
Pseudounipolar neuron
What is a Pseudounipolar neuron like?
All its dendrites are joined up as one
smaller cell body - located in ganglia
All sensory neurons are of what type? where do their cell bodies lie?
pseudounipolar
cell bodies lie in ganglia (dorsal root ganglia)
All motor neurons are of what type? where do their cell bodies lie?
multipolar
ventral root (motor) so cell bodies lie in grey matter of spinal cord
Why do neurons have lots of mitochondria and endoplasmic reticulum?
cell body is making neurotransmitter that then travels down the axon to be stored in the vesicles and then secreted when an AP or impulse reaches there
Multiple Sclerosis
own immune system attacks myelin sheath - patchy loss
nerve conduction across affected axons abnormal
Cause unknown (? Viral, ?autoimmune)
MRI shows whitish plaques of demyelination
Scotland has HIGHEST incidence in the world
What is white matter?
myelinated axons- bundled together depending on what modality they are carrying - sensory or motor
either running to cerebral hemisphere or down from it
What is grey matter?
neuronal cell bodies
What is a tract
bundles of fibres (mainly myelinated axons) that are sitting in the white matter of the spinal cord
Collection of cell bodies within the CNS is called what?
a nucleus
How many types of glial cells are there? Name them
6 different types
within CNS - 4 types: astrocytes oligodendrocytes microglia ependymal cells
Within PNS - 2 types:
Schwann cells
Satellite cells
What are tumors of glial cells called?
glioma
Why are astrocytes important?
they cover capillaries and synapses so keep neurotransmitter localised in these synapses
help form blood brain barrier
Importance of microglia
responsible for phagocytosis and scar tissue formation in CNS
Importance of ependymal cells
line ventricles in the brain
Importance of satellite cell
surround neuronal cell bodies - help to nourish and support them
What is the blood brain barrier
Is a protective mechanism that helps maintain a stable environment for the brain and prevents harmful amino acids & ions present in the bloodstream and blood cells from entering the brain.
Special features of the BBB
Endothelium has tight junctions
thick basal lamina
foot processes of astrocytes - prevents stuff from leaking out of the capillaries
Drug delivery into the CNS
drugs have to be lipid soluble or use suitable vectors
How many ventricles are there in the brain
4
lateral ventricle x2
III ventricle
IV ventricle
What does the subarachnoid space contain?
cerebrospinal fluid
Where is CSF present?
inside ventricles
between pia and arachnoid layers
What forms CSF?
Choroid plexus in each ventricle
Where is CSF absorbed?
by arachnoid villi into saggital sinus (around outside of skull)
