The Spinal Cord Flashcards
What is a plexus
A branching network of intersecting nerves including afferents and efferents
What is the dorsal horn
Part of the spinal cord
Includes sensory nuclei that receive and process incoming somatic sensory information
What is the ventral horn
Part of the spinal cord Includes
Includes cell bodies of motor neurones that send axons of spinal nerves to striated muscles
What is the spinal cord divided into starting from the top (cervical)
8 cervical
12 thoracic
5 lumbar
5 sacral
1 coccygeal nerve
What is are the branches of nerves called after the spinal cord ends
Cauda equina
Describe the structure of a nerve
Endometrium wraps each axon
Axon bundles- fascicles- surrounded by perineurium
Entire nerve surrounded by epineurium
True or false: plexuses have both sensory and motor neurones
True
What are rami
Divisions of spinal nerves
How is the lumbar plexus formed
Formed by anterior rami of nerves from T12-L5
Nerves pass in front of the hip joint and serve the anterior part of the thigh
How is the sacral plexus
Formed by anterior rami of nerves from L4-S5
Provides motor and sensory nerves to posterior thigh, foot and pelvis
How are spinal cords formed
By joining dorsal and ventral roots of the spinal cord
How is a peripheral nerve formed
Anterior and posterior rami of several spinal nerves join together
In arm and leg they form a plexus first
Arm- brachial plexus
Leg- lumbrosacral plexus
What are the nerve roots for the femoral nerve
L2-L4
What are the three different types of peripheral nerves
Sensory, motor and mixed
What is the function of sensory nerves
Send afferent sensory information from the body to the brain via the spinal cord
What is the function of motor nerves
Send efferent motor information from the brain to the body via the spinal cord
What is a mixed nerve and what is its function
Carry both sensory and motor info
Include spinal nerves and 4 of the cranial nerves
Where is the synapse for motor nerves
On muscles at neuromuscular junctions- the motor endplate
What does the synapse release at a neuromuscular junction
Neurotransmitter acetylcholine
What does acetylcholine activate
Nicotine acetylcholine receptors
What occurs after ACh activates nAChRs
A small local depolarisation- end plate potential
What does an end plate potential trigger
An action potential leading to a muscle contraction
Describe the steps of generating an action potential at a neuromuscular junction
Synapse releases acetylcholine
Activates nicitonic acetylcholine receptors
Causes small local depolarisation known as end plate potential
End plate potential triggers action potential
Leads to muscle contraction
How is a neurotransmitter released in a synapse
Ca2+ enters through ca2+ channels
Vesicle with neurotransmitter inside brought close to membrane
Vesicle fuses with membrane
Transmitter released by exocytosis
What type of channel is nicotinic acetylcholine receptor
Cation permeable ligand-gated ion channel
What occurs in the post synaptic knob after ACh has binded to generate an action potential
3 Na+ enters
2 K+ exits
Leads to knob becoming more positive
Exceeds threshold
End plate potential formed
Leads to AP
What is myasthenia gravies
Autoimmune disease where AB produced against nAChRs
Inability to activate muscles at neuromuscular junctions
Causes muscle weakness and fatigue
What are the clinical signs of myasthenia gravis
ptosis- drooping of eyelid
eye rotation
What is the function of neuromuscular blocking agents and what does this cause
Block transmission at neuromuscular junctions
Cause paralysis of skeletal muscles
What kind of molecule is a neuromuscular blocking agent
Competitive antagonist
How can neuromuscular block be overcome
By increasing the concentration of ACh
What are some clinical uses of neuromuscular blocking agents
Paralyse vocal cords during endotracheal intubation
Relax skeletal muscles during surgery
Permit mechanical ventilation in patients with poor lung function
What is patellar reflex
Known as knee jerk reflex
Tested to see the integrity of L2-L4 spinal nerves
What is Westphals sign
Absence of patellar reflex
What can westphals sign be used to diagnose
Peripheral nerve disease- dorsal sensory columns of the spinal cord
Lesions in the primary motor cortex
Interruption of sensory or motor neurones in the femoral nerve
