1 / 27

Nervous System (NS) – Cerebral Cortex

بسم الله الرحمن الرحيم. Dr. Othman Al- Shboul Department of Physiology. Nervous System (NS) – Cerebral Cortex. Based on differences in the structure, location, and functions, nervous system is subdivided into: Central nervous system (CNS) Brain and spinal cord Contained within bone

liuz
Télécharger la présentation

Nervous System (NS) – Cerebral Cortex

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. بسم الله الرحمن الرحيم Dr. Othman Al-Shboul Department of Physiology Nervous System (NS) – Cerebral Cortex

  2. Based on differences in the structure, location, and functions, nervous system is subdivided into: • Central nervous system (CNS) • Brain and spinal cord • Contained within bone • Peripheral nervous system (PNS) • All nerve tissue outside CNS • Sensory & motor divisions Organization of the Nervous System

  3. Generalized Model of Function of NS INPUT (PNS: sensoryneurons; afferentneurons) INTEGRATION (CNS: inter-neurons) OUTPUT (PNS: motor neurons; efferent neurons)

  4. Cells of the Nervous System • Consists of 2 kinds of cells: • Neurons: functional units of NS • Supporting cells (= glial cells) • Maintain homeostasis • Are 5X more common than neurons • Schwann and satellite cells in the PNS • Oligodendrocytes, microglia, astrocytes and ependymal cells in the CNS

  5. Afferent neurons: • Sensory receptor at peripheral ending (generates AP) • Convey input to the CNS • Cell body outside CNS • Efferent neurons: • Cell bodies in the CNS • Convey output for the effector organs (muscles, glands) • Interneurons: • 99% of all neurons • Integrating peripheral responses to peripheral information Functional Classes of Neurons

  6. The Central Nervous System (CNS)

  7. Consists of: • The brain • Spinal cord CNS

  8. Major brain functions: • Regulates internal environment • Experiences emotions • Voluntarily controls movements • Perceives own body and surroundings • Engages in other higher cognitive processes (e.g. thought and memory) • Brain functions as a whole (neurons linked via synapsis). The Brain

  9. Based on anatomical distinction, functional specialization, and development, brain has the following regions: • Brain stem (Medulla, pons, midbrain) • Cerebellum • Forebrain • Diencephalon • Hypothalamus • Thalamus • Cerebrum • Basal nuclei • Cerebral cortex Major Components of the Brain

  10. the outermost sheet of neural tissue (gray matter) of the cerebrum of the brain • Total surface area: 2200 cm2 (2.5 ft2) • Thickness: 1.5 mm - 4.5 mm • Weight: 600 gm (40 % of total brain weight) • 180 gm --------- neurons (10-15 billion neurons) • 420 gm --------- glial cells • Function: motor control of the body & information processing center Cerebral Cortex neuronal cell bodies &their dendrites & most glial cells Myelinated nerve fibers (axons)

  11. Functions of Cortical Lobes • Voluntary motor activity • Speaking ability Receiving and processing sensory input Initial processing of visual input sound (auditory) sensation

  12. Somatosensory Cortex • The somatosensory cortex: • located in the front portion of each parietal lobe • Immediately behind the central sulcus • Post-central gyrus • It is the site for initial cortical processing • and perception of: • Somestheticinput (sensations from the surface of the body, such as touch, pressure, heat, cold, and pain ) • Proprioceptive input (awareness of body position)

  13. Somatosensory Cortex • Each region within the somatosensory cortex receives input from a specific area of the body. • Different parts of the body are not equally represented • The size of each body part in this homunculus indicates the relative proportion of the somatosensory cortex devoted to that area. (e.g., fingers >>> trunk) • Reception of opposite side inputs Sensory Homunculus Proportional representation of the different body parts and areas in brain hemispheres

  14. Somatosensory Cortex • Thalamus vs. somatosensory cortex: • Thalamus  simple awareness of sensation • Somatosensory cortex  full sensory perception (location, intensity ….) • Capable of spatial discrimination; shapes and small differences between objects • Connections with higher brain centers: • via white matter fibers to adjacent higher sensory areas for furtherelaboration, analysis, and integration of sensory information.

  15. Primary Motor Cortex • Primary motor cortex: • Immediately in front of the central sulcus • Pre-central gyrus • Next to the somatosensory cortex • Confers voluntary control over movement produced by skeletal muscles. • Controls opposite side muscles of the body

  16. Primary Motor Cortex • The extent of representation in the motor cortex is proportional to the precision and complexity of motor skills required of the respective part • E.g., lips are >>> trunk area Motor Homunculus Proportional representation of the different body parts and areas in brain hemispheres

  17. When an area of the brain associated with a particular activity is destroyed, other areas of the brain may gradually assume some or all of the functions of the damaged region • Mechanism: ???formation of new neural pathways (not new neurons, but new connections between existing neurons) Brain Plasticity

  18. Electroencephalogram (EEG)

  19. The recording of electrical activity (potentials) along the scalp • A tracing (measurement) of voltage fluctuations resulting from ionic current flows within the neurons of the brain versus time recorded from electrodes placed over scalp in a specific array • Deep parts of the brain are not well sampled Electroencephalogram (EEG)

  20. EEG Elements • Electrodes: • Active electrodes: Attached to the scalp • Reference electrode: Mastoid, nose, ear lobe... • Amplifier The EEG records differences in voltage – difference in electrical potential from one electrode to another

  21. EEG Rhythms • Alpha (α) waves • Most common in adults. • Posteriorly (occipital) more than anteriorly • Especially prominent with closed eyes and with relaxation. • Disappears normally with attention (e.g., mental arithmetic, stress, opening eyes). • In most instances, it is regarded as a normal waveform.

  22. EEG Rhythms • Beta (β) waves • Small in amplitude • More evident anteriorly • Drugs, such as barbiturates and benzodiazepines, augment beta waves

  23. EEG Rhythms • Theta (θ) waves • Normally seen in sleep • In awake adults, these waves are abnormal if they occur in excess.

  24. EEG Rhythms • Delta (δ) waves • Normally seen in deep sleep. • Delta waves are abnormal in the awake adult. • Often, they have the largest amplitude of all waves. • Theta and delta waves are known collectively as slow waves.

  25. EEG Rhythms

  26. To distinguish various stages of sleep A clinical tool in the diagnosis of cerebral dysfunction (e.g. Epilepsy) Legal determination of brain death EEG Uses

  27. The END

More Related