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Brain spinal cord notes

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  • 1. Learning Outcomes • To describe the major components of the Central, Peripheral and Autonomic Nervous systems. • To understand the functions of these components. • To explain how a nervous impulse is transmitted. • To explain the underlying physiology behind the lesions/damage that occurs in the nervous system.
  • 2. Spinal cord structure
  • 3. Spinal cord has two main functions: 1). SC connects a large part of the peripheral nervous system to the brain. 2) SC acts as a minor coordinating centre responsible for some simple reflexes (e.g withdrawal reflex). 31 pairs of spinal nerves arise along the spinal cord
  • 4. • Extension of brain stem • Long slender cylinder of nerve tissue (~45 cm long, 2cm diameter). • Enclosed by a protective vertebral column (vertebrae). • Paired spinal nerves emerge from spinal cord. • Spinal nerves named according to region of vertebral column from which they emerge.
  • 5. Peripheral Nervous System • 31 pairs of Spinal nerves • 12 pairs of Cranial nerves • Autonomic Nervous System
  • 6. 8 pairs: Cranial Nerves 12 pairs: Thoracic Nerves 5 pairs: Lumbar Nerves 5 pairs: Sacral Nerves 1 Pair: Coccygeal Nerves
  • 7. • During development, vertebral column grows ~25cm longer than SC. • Nerves pass down SC and exit at particular points from the vertebral column. • At the lower end of vertebral column is a thick bundle of elongated nerve roots called Cauda Equina (‘horses tail’). At this region Spinal Taps can be taken (collection of CSF). No SC, so no damage caused.
  • 8. • A cross section of the SC shows it is composed of grey matter in the centre surrounded by white matter. Ventral horn White matter Grey matter Dorsal horn
  • 9. Grey Matter. – resembles the letter H (butterfly) – consists of mixture of multipolar neurone cell bodies (colour) – consists of 2 prominent projections: • Posterior Dorsal Horn • Anterior Ventral Horn
  • 10. Dorsal Horn: • Groups of afferent fibres carrying impulses from peripheral sensory receptors enter through the dorsal root into here. Ventral Horn: • Nerve fibres exit from here through ventral roots to skeletal muscles. Dorsal and ventral roots are very short and fuse to form the spinal nerves.
  • 11. Poliomyelitis: polio = grey matter myelitis = inflammation of SC • Polio virus enters through faeces contaminated water. • Polio virus causes destruction of anterior ventral horn motor neurones. • Muscles atrophy due to wasting (astronauts) • Death by paralysis of respiratory or cardiac muscle • Salk and Sabin polio vaccines eliminated disease.
  • 12. White Matter - Composed of myelinated and unmyelinated nerve fibres. - Divided into: Posterior funiculi Lateral funiculi Anterior funiculi
  • 13. Spinal Cord Segments
  • 14. • Spinal tracts are bundles of axons grouped together into columns that extend length of the spinal cord • A spinal tract consist of neuronal axons that have a similar destination and function • Part of a multineurone pathway that connect the brain to the rest of the body • Each tract either: - begins with a particular part of the brain (Motor / descending tract) - ends with a particular part of the brain (Sensory /ascending tract) • Tracts are named according to their origin and point of termination.
  • 15. The Brain
  • 16. • The brain is organised into several different regions dependent upon function, anatomy and development. 1). Brain stem: - Midbrain - Pons - Medulla 2). Cerebellum: 3). Forebrain: • Although specific activity is attributed to particular regions, complex interplay between regions exists.
  • 17. • A majority of the brain which we recognise is the Cerebrum (outer wrinkly part). • Deep folds divide each half of the Cerebrum into 4 major lobes. - Occipital lobes: process visual input - Temporal lobes: process sound - Parietal lobes: receive and process somesthetic sensations (touch, pressure, heat, cold, pain) and proprioception (awareness of body position) - Frontal lobes: 3 functions: voluntary motor activity, speaking ability, thought
  • 18. Cerebral Hemispheres (Cerebrum). • Largest part of the brain • Account for about 80% of brain weight. • Divided into 2 halves: - Right cerebral hemisphere - Left cerebral hemispheres. • They are connected together by the Corpus Callosum. • This is a thick band of neuronal axons transversing between the 2 hemispheres.
  • 19. • The entire surface of the cerebral hemispheres are marked by elevated ridges of tissue called Gyri. • These are separated by shallow grooves called sulci. • The deepest of these grooves are called fissures. • The median longitudinal fissure separates the cerebral hemispheres from one another. • The transverse fissure separates the cerebral hemispheres from the cerebellum below it.
  • 20. Parts of the Brain • Cerebrum • Thalamus • Hypothalamus • Cerebellum • Midbrain • Pons • Medulla Oblongata
  • 21. Cerebral lobes and their function • Frontal: - voluntary motor activity - speech - thought • Temporal: - process sound • Occipital: - process visual input • Parietal: - process somesthetic sensations (touch, pressure, heat, cold - proprioception; awareness of body position
  • 22. www.smc.edu
  • 23. The Brain – Cerebral cortex: cognition, senses, movement – Cerebellum: coordination of muscle contraction – Thalamus: relay center – Hypothalamus: homeostasis – Limbic System: instincts, emotions – Brain Stem: medulla controls breathing, blood pressure, heart rate
  • 24. Parts of the Brain Cerebrum Thalamus Hypothalamus Cerebellum Midbrain Pons Medulla Oblongata Tortora, G. J. and Grabowski, S. (2000) Principles of Anatomy and Physiology
  • 25. The Cerebrum www.smc.edu
  • 26. www.smc.edu
  • 27. Spinal cord has two main functions: 1). SC connects a large part of the peripheral nervous system to the brain. 2) SC acts as a minor coordinating centre responsible for some simple reflexes (e.g withdrawal reflex). • 31 pairs of spinal nerves arise along the spinal cord The Spinal Cord
  • 28. Peripheral Nervous System • 31 pairs of Spinal nerves – Join together to form Plexuses • 12 pairs of Cranial nerves • Autonomic Nervous System
  • 29. Any localised damage to spinal cord or spinal roots will attribute to some form of functional loss. - Paralysis: (loss of motor function) - Parasthesias: (loss of senses) The effects of disease or injury upon the CNS and periphery depend on the: - severity of the damage - type of neurones involved - position of neurones involved Lesions/Damage to the Nervous System
  • 30. • Normal muscle function requires intact connections along motor pathway. • Chain of nerve cells that runs from the brain through the spinal cord out to the muscle is called the motor pathway. • Damage at any point reduces brain's ability to control muscle's movements. • Reduced efficiency causes weakness (paresis).
  • 31. • Complete loss of communication prevents any willed movement. • Lack of control is called paralysis. • Paralysis may affect an individual muscle, but usually affects an entire body region. • Distribution of weakness an important clue to location of the nerve damage that is causing the paralysis. • Words describing the distribution of paralysis use the suffix "-plegia," from the Greek word for "stroke.“
  • 32. The types of paralysis are classified by region: Monoplegia: affecting only one limb Diplegia: affecting the same body region on both sides of the body (both arms, for example, or both sides of the face) Hemiplegia: affecting one side of the body Paraplegia: affecting both legs and the trunk Quadriplegia: affecting all four limbs and the trunk.
  • 33. • The nerve damage that causes paralysis may be in the: - brain or spinal cord (CNS) - nerves outside the spinal cord (PNS). • The most common causes of damage to the brain are: - Stroke - Tumour - Trauma (caused by a fall or a blow) - Multiple sclerosis (destruction of Myelin sheath)) - Cerebral palsy (defect or injury to the brain that occurs at or shortly after birth) - Metabolic disorder (interferes with body's ability to maintain itself).
  • 34. • Damage to spinal cord is most often caused by trauma, (fall/car crash). Other conditions that may damage nerves within or immediately adjacent to spine include: - Tumour - Herniated disk (also called a ruptured or slipped disk) - Spondylosis (a disease that causes stiffness in the joints of the spine) - Rheumatoid arthritis of the spine - Neurodegenerative disease (a disease that damages nerve cells) - Multiple sclerosis.
  • 35. • Paralysis originating in the brain may sometimes be flaccid, that is, the affected muscles may be loose, weak, flabby, and without normal reflexes. • More frequently it is spastic, that is, the affected muscles are rigid and the reflexes accentuated. • Paralysis originating in a motor nerve (UMN) of the spinal cord is always spastic • Paralysis originating in peripheral nerves (LMN) is always flaccid.
  • 36. Cerebrovascular Accident (Stroke) • CVAs are: bleeds into the brain obstruction of blood supply to brain • CVAs often affect Motor cortex and its major pathways. • These tracts cross in medulla therefore: - left hemiplegia (stroke on right side of brain) - right hemiplegia (stroke on left side of brain) • Small bleeds close to brain surface may result in weakness on one side (hemiparesis) - good chance of recovery • Larger/deeper bleeds may cause profound paralysis - may result in permanent damage
  • 37. Pupillary Reflex • Clinical test for brain stem function • Shine bright light into patient’s eye • Normal response: pupils constrict in response to light stimulus • Reflex via autonomic nervous system • Sensory input of bright light- to brain via optic nerve (II) – parasympathetic impulses out via oculomotor nerve (III) – circular muscles of eye constrict • Pupil observation important when considering head injury care
  • 38. Plantar (sole) reflex • Tests integrity of spinal cord from L4-S2 • Determines functionality of corticospinal tracts • Normal response is a downward flexion (curling) of toes • If corticospinal tract damaged, normal plantar’s reflex replaced by Babinski’s sign • Toes fan backwards Normal Abnormal