Week 2 HNN lectures Flashcards
Where are the Intervertebral discs found?
In between vertebral bodies
What is the function of Intervertebral discs?
To act as shock absorbers
What can happen if there is damage to the fibrous outside of the IVD?
The inside can pop out (prolapsed disc)
How does a prolapsed disc happen?
If there is damage to the fibrous outside of the IVD
What can a prolapsed disc cause?
Nerve damage (it presses on the nerve roots)
What type of pain can a prolapsed disc cause?
Radicular pain
Where are the two most common places for a prolapsed disc?
Lumbar and cervical
Where is the nerve problem in the condition sciatica?
The nerve root at L5
Where does parasympathetic innervation come from?
The parasympathetic cranial nerves and the sacral section of the spine
How many cervical pairs of nerves are there?
8
What do the cervical nerves innervate?
The arms and neck
What do the thoracic nerves innervate?
The truncal and intercostal muscles
What do the lumbar nerves innervate?
The legs
What do the sacral nerves innervate?
Perineal floor and the pelvic organs
What is the epidural space?
The space between the dura and the vertebral periosteum, filled with fat and venous plexus
What is the sub arachnoid space?
Filled with CSF, continuous with the subarachnoid space of the cranium
What is a spinal ganglion?
Contains nerve cell bodies of primary sensory afferents and psuedounipolar neurons. There are no synapses
What is the anterior root?
Carries motor information, exits spinal cord through anterolateral sulcus
What is the fasciculus gracilis?
Sensory (fine touch, vibration, proprioception) - from ipsilateral lower limb
What is the fasciculus cuneatus?
Sensory (fine touch, vibration, proprioception) - from ipsilateral upper limb
What does ipsilateral mean?
From the same side as the body
What travels on the spinocerebellar tract?
Proprioception from limbs to cerebellum
What travels on the lateral corticospinal tract?
Motor to ipsilateral anterior horn (mostly limb musculature)
What travels on the spinothalamic tract?
Pain and temperature from the contralateral side of the body
What does contralateral mean?
relating to the opposite side of the body
What travels on the anterior corticospinal tract?
Motor to ipsilateral and contralateral anterior horn (mostly axial musculature)
What happens at the anterior white commissure?
Pain and temperature fibres cross.
Anterior corticospinal fibres cross
Where does the spinothalamic tract run?
The anterior part of the spinal cord
What is a dorsal root ganglion made up of?
sensory cell bodies.
How many motor neurons supply one muscle fibre?
One
What are Gamma motor fibres involved in?
The fine control of muscles, they keep the muscle spindle tense
How do gamma fibres know what position a muscle is in?
Sensory fibres relay information on how much movement has occurred
How (SIMPLY) do tendon stretch reflexes work?
The tendon is stretched (and it doesn’t like this) and a the muscle is also stretched which sends a signal to the brain
When a tendon is stretched it is at risk of mechanical damage. This means it wants its muscle belly to relax to take some pressure away. This is a protective mechanism for the tendon.
What does an EEG do?
Records electrical activity in the brain
What is the latency?
The length of time between the stimulus and the action
What is suggested if the conduction of a nerve is slower than expected?
Demyelinating neuropathy
What would be expected if there was axonal damage?
Low signal
What would be expected if there was myelin damage?
Slow signal
What is Guillan- Barre syndrome?
an immune reaction to an initial infection. The protein is a bit like one in the myelin so the body has overreacted and begins to destroy the myelin.
What is Myasthenia Gravis?
An autoimmune reaction to the Ach receptor
What does the upper subscapular nerve supply?
The subscapularis muscle
What does the lower subscapular nerve supply?
Subscapularis, teres major
What does the thoracodorsal nerve supply?
Latissimus dorsi
What does the axillary nerve supply?
Sensation to the shoulder and motot to the deltoid, teres minor and triceps brachii (long head)
What does the radial nerve supply?
Triceps brachii, brachioradialis, extensor muscles of the fingers and wrist, supinator, and the extensor and abductor muscles of the thumb
What does issues with the common peroneal nerve lead to?
weakness in dorsiflexion and eversion
What three layers does gastrulation give?
Ectoderm, Mesoderm and endoderm
What is the definition of gastrulation?
A process of cell division and migration resulting in the development of the bilaminar disc into the trilaminar embryonic disc (3 germ layers)
What does the ectoderm give rise to?
CNS, PNS, Sensory epithelium of the ear, nose and eye, Epidermis, hair and nails, subcutaneous, mammary and pituitary glands and enamel of the teeth
What does the endoderm give rise to?
the epithelial linings of the respiratory passages and the GI tract, including the gland openings into the GI tract and the glandular cells of associated organs, such as the liver and the pancreas.
What does the Mesoderm give rise to?
smooth muscular coats, connective tissues and vessels associated with the tissues and organs. The mesoderm also forms most of the cardiovascular system and is the source of blood cells and bone marrow, the skeleton, striated muscles and the reproductive and excretory organs.
What is the notochord?
A flexible rod shaped structure that lies ventral to the neural tube. It has an inductive relationship with the neural plate
What is the relationship between the neural plate and the notochord?
An inductive relationship
What is the notochord made from?
Mesoderm
What does the notochord become?
The nucleus pulposus of the intervertebral disc
What signals does the notochord produce?
Noggin and chordin
What does Noggin do?
inactivates BMP4 (BMP4 absence causes patterning of NT and somites)
What does chordin do?
BMP antagonist
What does the inductive effect of the notochord on the neural plate have?
causes the overlying ectoderm to thicken and form the neural plate
What happens after the neural plate is induced?
the lateral edges elevate, forming neural folds. The depressed mid region forms the neural groove
In which direction does fusion of the neural tube proceed?
In the cephalic and caudal directions.
What do neural crest cells go onto form?
Spinal ganglion, Schwann cells, Adrenal Medulla, Melanocytes, Connective tissue in the head region
What does Treacher Collins syndrome cause?
Under development of the zygomatic bones and ears
What causes Treacher Collins syndrome?
A mutation in the TCOF1 gene
What does Di George syndrome cause?
Pneumonic CATCH 22:
- Cleft palate
- Abnormal facies
- Thymic aplasia
- Cardiac abnormalities
- Hypocalcaemia/hypoparathyroidism
What doe the neuroepithelial cells go on to form?
Various types of neurones, astrocytes and glial cells
What do the neuroepithelial cells give rise to once the neural tube closes?
Neuroblasts at the peripheral edges of the neural tube
What do the neuroblasts at the peripheral edges of the neural tube form?
The mantle layer
What is the mantle layer?
A zone around the neuroepithelial layer
What does the mantle layer go on to form?
Grey matter of the spinal cord
What is the outermost layer of the spinal cord?
The marginal layer
What is the marginal layer also known as?
The white matter
What is the sulcus limitans?
a longitudinal groove that separates the dorsal alar and ventral basal plates of the spinal cord
What is hydrocephalus?
A build up of CSF in the brain that can put excess pressure on the brain and damage it
How can hydrocephalus be relieved?
Shunting of the fluid into the abdomen via the surgical implantation of a shunt
Where is CSF made?
The choroid plexus
Where are the choroid plexus found?
Where the pia mater and the ependyma come into direct contact (e.g. the roof of the 4th ventricle)
What is a reflex?
An involuntary stereotyped response to a stimulus
When do tendon jerk reflexes occur?
Automatically in response to a stimulus
What are the two types reflexes?
Somatic and autonomic
What type of reflex is a tendon jerk reflex?
Somatic
How is a tendon jerk reflex elicited?
By hitting the tendon with a tendon hammer and causing a stretch
What is a monosynaptic reflex?
A two-neuron reflex arc with a single central synapse
What is an example of a monosynaptic reflex arc?
The knee jerk reflex
What is the stimulus for the knee jerk reflex?
A tendon tap with a tendon hammer that causes a brief stretch of the muscle.
What is the effect of the brief stretch of the muscle in the knee jerk reflex?
Activation of muscle spindle receptors which then produce action potentials
Where do the action potentials that are produced by muscle spindle receptors in the knee jerk reflex travel?
Along the peripheral nerve sensory fibres (1a afferent fibres) which then synapse directly with motor neurons
Why are tendon jerk reflexes used clinically?
They are simple to elicit and cant be faked
What is a reflex present only on one side suggestive of?
Mononeuropathy
What would it suggest if a reflex is normal in one muscle but not in another?
Polyneuropathy
What axons do peripheral neuropathies often affect first?
The longest ones
What is the pattern of sensory loss caused by peripheral neuropathies known as?
A stocking-glove pattern of sensory loss (hands and lower leg)
What is the result of the stretch reflex?
o Prolonged stretch of a muscle produces prolonged contraction
What is the function of the stretch reflex?
acts to maintain a constant muscle length and control muscle tone e.g. keeps the muscle in the same position even when a load is added
What are the 3 primary brain vesicles?
Forebrain - prosencephalon
Midbrain - Mesencephalon
Hindbrain - Rhombencephalon
What do the meninges develop from?
Mesenchymal cells and neural crest cells
When does the eye begin to develop?
Day 22 as a pair of shallow grooves
What are the optic vesicles?
outgrowths from the diencephalon of the forebrain
What does the lens placode develop from?
the surface ectoderm and invaginates into the optic vesicle
What do the 2 walls of the optic vesicle form?
The optic stalk
What is the function of the choroidal fissure?
Provides a pathway for the hyaloid artery
What does the hyaloid artery supply?
The lens and developing retina
What is the lens derived from?
Ectoderm
