Neuroanatomy Spinal cord (1).pdf

Neuroanatomy Nick Hurst  Neurological anatomy and physiology Aims and To understand the structure of a nerve cell objective Be able to explain how information is transmitted To be able to explain the development of the nervous system Be able to explai...

Neuroanatomy Nick Hurst  Neurological anatomy and physiology Aims and To understand the structure of a nerve cell objective Be able to explain how information is transmitted To be able to explain the development of the nervous system Be able to explain the organisation of the nervous system Identify regions of the brain and spinal cord and their functions Investigate the central nervous system and peripheral nervous system and how they relate to medical conditions Spinal cord Anatomy of the spinal cord Within Vertebral canal Continues from brain stem Receives info from, and controls trunk and limbs Undifferentiated structure compared with the brain Picture: https://neupsykey.com/introduction-and-overview/  31 pairs of spinal nerves Picture: http://dhamma4u.com/spinal-cord-images-anatomy/admirable-spinal-cord-images-anatomy/ Picture: https://neupsykey.com/introduction-and-overview/  Intervertebral foramina Cauda equina – lumbar and sacral nerves Spinal nerves end at L1/L2 disc Why end here? Picture: http://aurorachiroplus.com/chiropractic-care-aurora-co-wellness/symptoms-disc-herniation-treat/  Cauda equine syndrome https://www.pinterest.com/pin/432556739200491284/ http://pennstatehershey.adam.com/content.aspx?productId=114&pid=28&gid=000415  Picture: https://www.quora.com/Why-does-our-left-hemisphere-of-brain-control-our-right-side-of-our-body-and-the-right-our-left However……...  - The olfactory system isn’t reversed at all. - The visual system is only partly reversed; each eye sends some information to each side of the brain. - Sounds are analysed on both sides of the lower portions of the brain but on only one side of the cortex. https://www.quora.com/Does-olfactory-nerve-have-a-ganglion https://www.pinterest.com/pin/75083518765722309/  Spinothalamic tract Spinocerebellar tract and Dorsal columns Corticospinal tract Picture: http://vanat.cvm.umn.edu/neurLab2/pages/SpThalTract.html Picture: http://resizeme.club/picresize-212_12.html How do we feel pain?  Alpha Beta Fibres Alpha-delta (aδ) fibres C-fibres (Visceral Pain) (Touch) (Somatic Pain) Large, mylelinated and fastest Small myelinated fibres which Smalleat diameter. Non- conducting conduct rapidly myelinated fibres with low conduction velocity Carry information related to Sharp Pain Diffuse pain touch/pressure Precisely located Precisely located Not distinctly localised Ø 3 orders of neurons carrying action potential signalling pain from periphery to cerebral cortex. Ø 1st order neuron- cell bodies within the dorsal root ganglion. Synapse with the 2nd order neuron Ø 2nd order neuron- travels along the spinothalamic tract- synapses in the Thalamus Ø 3rd order neuron- sends fibres to the somatosensory cortex (location)  Descending pathway Ø Responsible for pain inhibition Ø Periaquaductal grey matter (PAG) Ø Role in descending pathway and pain modulation Ø Enkephalin-releasing neurons Ø Serotonin descends to the dorsal horn of the spinal cord & forms excitatory connections with inhibitory interneurons Ø Activated interneurons release enkephalins or dynorphin that bind to mu opioid receptors Activation of Serotonergic (5-HT) and Noradrenergic (NA) neurons to prevent nociceptive neurotransmitters Endogenous and exogenous Opioid inhabitation of 1st order neurone.  Upper and lower motor neurones https://www.youtube.com/watch?v=ClXsS7O8seg&feature=youtu.be UMN transmit signals from the brain to brainstem and spinal cord. LMN transmit signals from the spinal cord to the muscles. Example Want to move RIGHT thumb. UMN arise from the LEFT Primary motor cortex Pass through the internal capsule through the midbrain and brainstem (Medulla and pons) Majority of Neurons cross over to the opposite side of the body at the medulla. Majority of UMN contained within the Lateral corticospinal tract through the spinal cord. Once the UMN reaches the correct vertebral level (via the spinal cord) it will synapse with the LMN at the anterior horn. The LMN will then target the muscle responsible for the movement of that body part (ie the muscles involved in the movement of the right thumb) Causes of UMN Lesions Signs of UMN lesions Causes of LMN Lesions Signs of LMN lesions Lower and upper motor neurone lesions Upper motor neurone syndrome Weakness or paralysis of specific movements (ie extension of upper limbs) No wasting of muscles Increased resistance to passive stretching muscles (spasticity) Hyperactivity of deep tendon reflexes (hyperreflexia) Emergence of extensor plantar response (Babinski reflex) Loss of abdominal reflexes Lower motor neurone syndrome Weakness (paresis) or paralysis (plegia) of individual muscles (ie Bells Palsy, Bulbar palsy) Wasting of muscles Fasciculation (of muscles) Reduced resistance to passive stretching (hypotonia) Diminution of loss of deep tendon reflexes (hyporeflexia or areflexia)  Blood supply to spinal cord Anterior and Posterior spinal artery Requires additional input from radicular arteries Picture: http://www.facts4u.co.in/blood-supply-of-spinal-cord-and-brain-anatomy/  Blood supply most vulnerable in thoracic region and anterior portion of cord Occlusion of anterior spinal cord – paraplegia and incontinence  Venous drainage Anterior and posterior spinal vein Via anterior and posterior radicular vein into internal vertebral venous plexus Ascends to: Lumbar veins Azygos Hemiazygos veins Picture: https://neupsykey.com/vasculature-of-the-central-nervous-system/ Ganglions  A nerve cell cluster Houses cell bodies of afferent and efferent nerve fibres Made up of somata and dendritic structures Can interconnect with other ganglia Complex systems – “Plexus” Function: provide relay points and intermediary connections between different neurological structures Dorsal root ganglia (Spinal ganglia) – sensory neurones Cranial nerve ganglia – cell bodies of cranial neurones Autonomic ganglia – cell bodies of autonomic nerves Post and preganglionic fibres