ANATOMY - SPINAL NERVES and HISTOLOGY OF NERVE Flashcards
In the spinal cords, what is the ventral horn , what does it look like?
The horn facing the front of the Body. It is the rounder of the 2 horns
What is contained in grey matter? Where in the spinal cord is it?
It is in the centre, the part that looks like a H.
It contains nerve cells
What is contained in the white matter of spinal cords
axons, many myelinated
Where is the spinal cords located?
In the vertebral canal
Where is the central canal located?
In the grey matter of the spinal cords
Do sensory neurons enter the spinal cord through the ventral or dorsal horn?
The dorsal
Do motor neurons exit the spinal cord through the ventral or dorsal horn?
Ventral
Are spinal nerves paired?
Yes
How many pairs of spinal nerves are there? List them
31 pairs.
C1-C8
T1-T12
L1-L5
S1-S5
1 Co (coccyx)
How is the spinal nerve formed from the spinal cords?
The posterior root and anterior root which originate from the spinal cords fuse to form the spinal nerve.
Do the spinal nerves divide?
Yes.
Into anterior and posterior rami.
What is a dermatome?
A strip of skin supplied by a single spinal nerve
What is a myotome?
All the skeletal muscle innervated by a single spinal nerve.
What must you test for when testing nerve function?
Motor and sensory loss
What are lower motor neurons?
Motor neurons which exit through the ventral horn of grey matter and innervate skeletal muscle
What is contained in the dorsal root ganglion?
The cell bodies of many sensory neurons
What is one structural difference between motor and sensory neurons?
Motor neurons are multipolar
Sensory neurons are unipolar
Where can sensory nerve endings be found?
Skin
Joint capsules
Muscles
Draw a motor neuron
Draw a sensory Neuron
Draw an Interneuron
What makes up the CNS?
Brain and spinal cord
What makes up the PNS?
Cranial nerves and spinal nerves
What are the 2 cell types in nervouse tissue?
Neurons
Neuroglia/support cells
What do interneurons do?
Send signal through CNS pathways
What are bundles of neuron processes called in the CNS?
Tracts
What are bundles of neuron processes called in the PNS?
Nerves
What is the cytoplasm called int he neuron cell body?
Perikaryon
Neuron cell bodies have few mitochondria t/f?
False. They have many
What are Nissl bodies and where are they found?
Clusters of RER
Found in base of dendrites and axon hillock
What are neurofilaments
Bundles of intermediate filaments found in neuron cell bodies
They give scaffolding and shape to the cell bodies
What structures allow transport of neurotransmitters within neurons?
Microtubules
What do dendrites do ?
Transmit impulse towards cell body
How many axons does one neuron have?
1
What do axons do?
Transmit impulses away from cell body
What are the branches at the end of the axon called?
End axon terminals/ terminal boutons
What are the 3 structural classifications of neurons?
- multipolar
- bipolar
- pseudounipolar / unipolar
Describe structure and function of a multipolar neuron
Has many dendrites and one axon
The most common type of neuron
Innervate skeletal muscle
Describe structure and function of bipolar neurons
2 processes
Rare neurons
Found in some sensory organs e.g retina of eye
Describe stucture and function of unipolar/ pseudounipolar neurons
- 1 short process
- Have a short projection which extends into 2 axons
-One axon goes into CNS
-One axon goes the the PNS - SENSORY NEURONS
What is a synapse?
Site at which one neuron
communicates with:
• another neuron, or
• an effector cell
Can synapses transmit impulses in either direction?
No. One direction only
What are the different types of synapses (STRUCTURALLY)
- axodendritic
- axosomatic (axon -> cell body)
- axoaxonic
- others which are uncommon
What are the types of synapse (method of transmitting signal)
- electrical synapse
- chemical synapse ( more common)
What are the components of a chemical synapse?
- Presynaptic terminal bouton
- Synaptic cleft
- Postsynaptic membrane
What are the support cells on the CNS?
- astrocytes
- microglia
- oligodendrocytes
- Ependymal cells
What are the support cells in the PNS?
- Schwann cells
- Epineurium
- Perineurium
- Endoneurium
What is the function of astrocytes?
- scaffolding
- blood brain barrier (foot processes line the meninges forming an impermeable barrier)
What is the function of oligodendrocytes ?
- form myelin sheath around many axons in CNS
Function of microglia?
- small phagocytes ( macrophages of CNS )
- migrate towards injured neurons
- engulf invading organisms and dead neurons
Function of Ependymal cells?
- line cerebrospinal fluid filled cavities
- have cilia to help circulation of CSF
What is the Epineurium ?
Surrounds entire nerve
What is the Perineurium ?
Surrounds each nerve fascicle
What is the Endoneurium ?
Surrounds each individual nerve fibre/axon
Extends from spinal cord almost to nerve ending
Symptoms of multiple sclerosis?
- visual disturbances
- muscle weakness
- sensory loss
What is the cause of Multiple sclerosis?
The immune system attack myelin around axons in the CNS
- impulse conduction if slowed and eventually ceases