Neuroanatomy Spinal Cord PDF

Neuroanatomy Nick Hurst 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://...

Neuroanatomy Nick Hurst 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://pen nstatehershey.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/  Spinocerebellar tract and Dorsal columns Corticospinal tract These are longitudinal running nerve fibres Spinothalamic tract – info from muscles and joint receptors – Sensory tract – carries nociceptive, temperature, crude touch and pressure from skin to the thalamus [Ascending tracts from trunk to brain] Picture: http://vanat.cvm.umn.edu/neurLab2/pages/SpThalTract.html Picture: http://resizeme.club/picresize-212_12.html How do we feel pain? Nociceptors under the skin. Chemicals released from the injury activate nociceptos → release SUBSTANCE P and GLUTAMATE (Pain producing neurotransmitters) Prostaglandins released due to inflammatory response activates the nociceptors.  There are two types of nociceptive pain: Somatic pain has an external identifiable cause and is transmitted by the Aδ fibres. activation of nociceptors in skin and skeletal muscle patient can normally identify exactly where the pain is. It can often be reproduced by touching or moving the area or tissue involved. Alpha Beta Fibres Alpha-delta (aδ) fibres C-fibres (Visceral Pain) (Touch) (Somatic Pain) Visceral pain has an internal cause and is transmitted via the Large, mylelinated and fastest Small myelinated fibres which Smalleat diameter. Non- C fibres. conducting conduct rapidly myelinated fibres with low conduction velocity - is activation of the nociceptors in the thoracic or Carry information related to Sharp Pain Diffuse pain abdominal organs. touch/pressure -is often poorly localised Precisely located Precisely located Not distinctly localised and may feel like a vague deep ache, sometimes being cramping or colicky in nature.  3 orders of neurons carrying action potential signalling pain from periphery to cerebral cortex. 1st order neuron- cell bodies within the dorsal root ganglion. Synapse with the 2nd order neuron 2nd order neuron- travels along the spinothalamic tract- synapses in the Thalamus 3rd order neuron- sends fibres to the somatosensory cortex (location)  Descending pathway Responsible for pain inhibition Periaquaductal grey matter (PAG) Role in descending pathway and pain modulation Enkephalin-releasing neurons Serotonin descends to the dorsal horn of the spinal cord & forms excitatory connections with inhibitory interneurons 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 UPPER MOTOR Neurons – located in cerebral cortex of the brain and facilitate the transmission of signals from the brain to the brain stem and spinal cord nerves (UMN) and then on to the skeletal muscles (LMN) – the target organ for the motor neurons. Descending motor pathways that control activity of LMN (Signals from UMN required to activate LMN’s) Corticospinal (pyramidal) and corticobulbar pathways important Breakdown leads to: loss of individual movement of digits Reduced extension and abduction of upper limbs UMN transmit signals from the brain to brainstem and Reduced flexion of lower limbs (referred to as Pyramidal weakness) spinal cord. PYRAMIDAL system = voluntary motor movement Communication between upper and lower motor neurons occur in the vertebrae LMN transmit signals from the spinal cord to the muscles. LOWER MOTOR Neurons – located in spinal cord and their terminal extend all the was to muscle fibres and tendons Skeletal muscle contraction is initiated by LOWER motor neurons Arise in brain stem (forming the cranial nerves) and those leaving the ventral horns of the spinal cord (SPINAL NERVES) LMM innervate muscle on same side of the body (effects of lesions are ipsilateral to the lesion) DAMAGE TO LMM → paralysis (loss of movement, or paresis (weakness) of the affected muscles Upper Motor Neurones (UMN) 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 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