L21- Nervous Tissue Structure And Function Flashcards
(33 cards)
What are the two divisions of the nervous system?
- Central nervous system (CNS): brain and spinal cord
2. Peripheral nervous system (PNS): cranial nerves and spinal nerves
Difference between grey and white matter?
Grey matter:
- peripheral in brain but central in spinal cord (butterfly shaped)
- consists of: nerve cell bodies, dendrites, axon terminals, non-myelinated axons and neuroglia (support cells)
White matter:
- central in brain, peripheral in spinal cord
- consists of: myelinated material (axons), no cell bodies
Outline the structure of the white and grey matter in the spinal cord
Grey matter is in the form of a butterfly:
- found in the centre
- anterior prongs: ventral horns (VH)
- posterior prongs: dorsal horns (DH)
- connected by the grey commissure (GC)
White matter on the periphery:
- contains nerve fibres that form ascending and descending tracts
- blood vessels from the outer connective tissue layer (pia mater), the ventral fissure (VF) and some dorsal roots of the spinal nerves are visible
What is the basic structure of a neuron?
- Dendrite/s: elongated processes specialised for receiving stimuli and conducting towards cell body
- cell body (perikaryon): contains nucleus and cytoplasm—> maintenance of cell (cytoplasm contains nissl bodies)
- axon: single process—> generates or conducts nerve impulses away from cell body to other cells
In the a) CNS and b) PNS which cells produce myelin?
A) Oligodendrocyte
B) Schwann cell
What are the 4 types of neurons?
- Location and function
- Motor
- Location: CNS —> Periphery
- Function: to send signals to effector tissues
- tyPES: presynaptic and postsynaptic autonomic neuron - Sensory:
- Location: Periphery —> CNS
- Function: to send environmental signals to integrative centre
- Types: pseudounipolar and bipolar neuron - Integrative
- Location: CNS
- Function: collate all information
- 3 TYPES: Pyramidal cell, interneurons (most common) and purkinje cell - Anaxonic
- Location; retina (some parts of CNS)
- Function: act as relays
A) Where are the following neuron cells found?
B) What type of neurons are they?
I) Pseudounipolar II) purkinje cells IIi) pyramidal cells Iv) Interneurons V) postsynaptic autonomic neurons Vi) presynaptic autonomic neurons Vii) Bipolar
I)
A) outside CNS
B) Sensory
II)
A) CNS
B) Integrative
Iii)
A) CNS
B) Integrative
Iv)
A) CNS
B) Integrative
V)
A) Outside CNS
B) Motor
Vii)
A) CNS
B) Motor
Vii)
A) Outside CNS
B) Sensory
What type of neurons are the majority of neurons in the CNS?
Interneurons
Outline the structure of the following: A) multipolar neurons B) bipolar neurons C) unipolar neurons D) anaxonic neurons
A) - one axon and multiple dendrites
- mot common
- most neurons in brain and spinal cord
B) - one axon and one dendrite
- olfactory cells, retina, inner ear
C) - single process leading away from soma
- sensory from skin and organs to spinal cord
D) - many dendrites but no axon
- help in visual processes
What would you see in a histology slide of a CNS Neuron?
- Nucleus
- Lots of rough endoplasmic reticulum (high protein synthesis)
- lots of Golgi apparatus
- many free ribosomes
A) What is axonal transport?
B) Structure of the axon related to this?
A) cellular process responsible for the movement of mitochondria, lipids, synaptic vesicles, proteins and other organelles through the cytoplasm of its axon
B) - microtubules made of tubular run along length of axon: provide cytoskeleton tracts
- Kinesin motor protein: moves cargoes in anterograde
- Dynactin motor protein: moves cargoes in retrograde
- these motor proteins bind and transport different cargoes including mitochondria and neutrotrnasmitter vesicles
A) What are the two types of axonal transport directions?
A)
- Anterograde (away from cell body to synapse): kinesin
- cargo tents to be Golgi derived vesicles (vesicles with neutrotrnsmitter ) - retrograde (conveys materials from axon to cell body): dynactin
- cargo tends to be molecules being returned for degeeneration (vesicles that are empty)
B)
Outline the synthesis and transport of neurotransmitters
- Synthesis of neurotransmitter in ER and Golgi with only enzyme
- Transport of neurotransmitter down axon (anterograde) using microtubules- as it travels it synthesises neutrotransmitter
- AP down axon, AP causes calcium to enter, release of NT in synaptic cleft
- NT binds to post synaptic receptor, response in post synaptic neuron
- Reuptake of NT to be recycled
- Vesicles without neurotransmitter travel back down cell body (retrograde)
What is the fate of an empty neurotransmitter vesicles?
- Recycled through clathrin-coated endocytosis
2. Lost to neurolemma
Different types of synapses?
- Axosomatic: directly to plasma membrane or nerve of cell
- Axodendritic: axon terminal synapses with dendritic spine
- Axoaxonic: synapse at axonic button
- Dendro-dendritic
- Axo-axonal
Structure of peripheral nerves
Nerve fibres separated by connective tissue layers
Out to inner:
- Paraneurium: fascia that seperates nerves from surrounding structures
- Epineurium:
- dense irregular CT
- seperates diff types of nerves and fills spaces between fascicles - Perineurium:
- specialised CT: transport proteins
- maintains ionic composition
- surrounds clusters of axons (fasicle) - Endoneurium:
- loose CT
- surrounds single nerve cells
What types of nerves to peripheral nerves contain?
- all 3 types: sensory, motor and integrative
- but each fasicle tends to only contain 1 type
There are A, B and C fibres. Compare them with the following headings: A) Size B) Speed C) Location D) Function E) Myelination F) Internodal distance
A FIBRES:
- Size: thickest
- Speed: fastest
- Location; CNS
- Function: motor
- Myelination: myelinated
- Internodal distance: largest
B FIBRES:
- Size: medium
- Speed: intermediate
- Location: viscera
- Function: sensory
- Myelination: myelinated
- Internodal distance: smallest
C FIBRES:
- Size: thinnest
- Speed: slowest
- location: periphery
- Function: sensory
- Myelination: unmyelinated
- Internodal distance: none
Steps of how myelination occurs
- The axon sitting in a groove is surrounded by a Schwann cell
- The mesaxon membrane initiates myelination by the surrounding embedded axon
- A sheet-like extension of the mesaxon membrane then wraps successively around the axon, forming multiple membrane layers
- Cytoplasm is extruded from between the two apposing plasma membranes of the Schwann cell, which then become compacted to form myelin (19-20 rounds)
What is an oligodendrocyte?
- it does the same thing as a Schwann cell except in the CNS
- Cytoplasmic processes from the cell body form flattened cytoplasmic sheaths that wrap around each of the axons
What is the difference in function between a Schwann cell and oligodendrocyte?
Pretty much the same except the oligodendrocyte wraps around more than one axon simultaneously—> 5 or 6
- oligodendrocyte in the CNS
- SChwann cell in the PNS
What are the other support cells in the CNS?
- astrocytes
- microglial cells
- ependymal cells
Astrocyte:
A) Structure
B) Location
C) Function
A) - star-like structure
- have perineural feet that contain gap junctions
B) CNS
C) - biochemical support for endothelial cells
- transport of nutrients (lactate and glucose) from blood to nerve cells
- regulate nerve impulses by releasing glutamate (near to node of ranvier)
- contribute to BBB
Microglial cell:
A) Structure
B) location
C) function
A) large cells with elongated nucleus and few processes from cell body
B) CNS
C) - Resident macrophage: immune function, remove damaged nerve cells, Sense increased K+ ions
- phagocytose dead cells or pathogens, process the proteins and then act as antigen presenting cells and blood brain barrier
