Physiology Central Nervous System part I.pptx

Physiology, CNS

1. The Central Nervous System By Mariam A. (MSc.)

2. Outline Introduction on the NS The CNS Regions of The Brain : Telencephalon, Diencephalon , Mesencephalon, Myelencephalon , Metencephalon The brain stem : components and function RF of the BS: parts and functions RAS and sleep The Limbic system : components, connections and function Memory : definition, types, characteristics, consolidation and encoding memory disorders. CSF : definition, functions, formation, composition, circulation and collection (spinal tap) Circumventricular organs The spinal cord (Reading Assignment)

3. Introduction: Extrinsic control systems- The NS VS Endocrine Syst ?

4. Cont.… Neuroscience Science of the nervous system … U nified field of science striving for understanding of human thought, emotion and behavior. Interdisciplinary (+ biology (cell + developmental), chemistry, computer science, engineering, linguistics, medicine, mathematics, neurophysiology, philosophy, physics, psychology + …etc.,).

5. Cont.… NS : is a complex system that coordinates actions & sensory information to & from different parts of the body. Receives millions of bits of information each minute from the different sensory nerves & sensory organs then integrates all to determine responses to be made by the body.

6. Cont.… The CNS contains > 100 billion neurons. Incoming signals enter this neuron through synapses located mostly on the neuronal dendrites , but also on the cell body . For different types of neurons, there may be only a few hundred or as many as 200,000 such synaptic connections from input fibers. Conversely, the output signal travels by way of a single axon leaving the neuron. Then, this axon has many separate branches to other parts of the NS or peripheral body

7. General organization of the NS

8. Cont.…

9. The CNS Is the part of the NS consisting primarily of the brain and spinal cord . Receives input f rom sensory neurons . Association neurons (interneurons) maintain homeostasis i n the internal environment . Directs activity of motor neurons .

10. Cont.… The Motor Neurons Specialized type of neurons located within the brain and the S.cord . C omprise tightly controlled circuits to control voluntary and involuntary movements . For voluntary control , signals start in the cerebral cortex reach the skeletal muscle through 2 levels of neurons . Upper motor neurons (UMN): neurons of the pyramidal and extrapyramidal tracts Lower motor neurons (LMN): neurons that extend from the anterior horn motor part of S.cord to the skeletal muscles that they innervate . The CNS influences the activity of the skeletal muscle trough these 2 sets of neurons

11. Cont.… NS Lesions: Motor neuron lesions UMNL: Damage of cerebral cortex Damage of pyramidal (with or without extra pyramidal) tracts. LMNL: Damage of ventral horn cells as in poliomyelitis Damage of motor nerves due to trauma or disease Both UMNL and LMNL results in paralysis ; loss of voluntary movements .

12. Importance of CNS Sensory detection Information processing (Integration) Perception Transformation of signal Transmission Planning and implementation of motor commands Thought processes and conscious awareness Learning Emotion and motivation Expression of behaviors and motor activities A Control network (life!)

13. CNS Tissues: Gray and White Matter Microscopically, the CNS contains 2 neural elements : Neuron cell bodies in clusters called nuclei . Nerve fibers (axons) in bundles called tracts . Viewed macroscopically , CNS tissues can be distinguished by color : Gray matter : consists of somata, dendrites, and unmyelinated axons . White matter : consists primarily of myelinated axons .

14. Cont.… The gray matter is  the areas where the actual "processing" is done  whereas the white matter provides the communication between different gray matter areas and between the gray matter and the rest of the body. The grey matter also extends from the brain into the spinal cord for effective signaling.

15. The Brain Brain Regions 1.Telencephalon ( Forebrain): Cerebrum, Basal Ganglia, Hippocampus & Amygdala 2. Diencephalon (Forebrain): Thalamus & Hypothalamus 3. Mesencephalon ( Mid brain): Tectum & Tegmentum 4. Myelencephalon ( Hindbrain): Medulla ob. 5. Metencephalon ( Hindbrain) : Cerebellum & Pons

16. Telencephalon Forebrain

17. 1. Cerebrum/Cerebral Cortex Largest portion of brain ( 80% mass ). Most developed in man Responsible for higher mental functions concerning: Perceptions of fine sensations Initiation of voluntary movements Higher intellectual functions **** Learning + memory Speech + language Judgment… Intelligence… Planning…

18. Cont.… The surface is marked by ridges called gyrus separated by grooves called sulcus . Highly folded, forming gyri and sulci ( SA  number of cortical neurons capacity for processing information…).

19. Cont.…. The cerebrum consists of  2 cerebral hemispheres connected by the corpus callosum . Has an outer cortex of gray matter surrounding an interior that is mostly white matter , except for a few small portions .

20. Cont.…. Each hemisphere contains 4 lobes ; Frontal lobe Parietal Temporal Occipital

21. Cont.…

22. Cont.… 3 types of functional areas : Motor : Control voluntary motor functions Sensory : allow for conscious recognition of stimuli Association : Integration

23. Broad man’s area of cerebral cortex Each gyrus contains one or more functional areas called Brodmann´s areas. Patchy organization of the brain by their difference in microscopic structure & functions .

24. Cont.… Brodman area used for control of voluntary movements: The Primary motor area/M1 (4) The Premotor area PMA(6,8,44,45) The supplemental motor area/SMA (6) The m otor association area/MAA (A-9-12 ) Brodman area used for analysis of sensory information include: The primary somatosensory areas (S I ) (3,1,2) The secondary somatosensory areas (S II ) (40) Somatosensory association area (5,7)

25. Motor function of the cerebral cortex Located in the frontal lobe , in front of the central sulcus. It is divided in to 4 functional areas The primary motor area/M1 (4) The premotor area/PMA (6, 8, 44, & 45) The supplemental motor area/SMA(6) The motor association area/MAA (9-12)

26. A. The primary motor cortex (A-4) Location: precentral gyrus in the frontal lobe. Body representation : the body is topographically represented in an inverted (head-down) and crossed (opposite side) manner . The toe  (at the top of the cerebral hemisphere) to mouth (at the bottom ) The area of representation is proportional to the degree of fine movement of the part. Eg. large areas for heads and muscles of speech and small area for trunk.

27. Cont.….

28. Cont.… Function of area-4 Initiation of voluntary, fine, discrete (separate) movement of limbs . (Eg. Hands, fingers) on opposite side. Facilitation of stretch reflex i.e . Facilitation of skeletal muscle tone and tendon jerk . Effect of lesion to area-4 Flaccid paralysis (reduced muscle tone) in the opposite side of the body . Recovery occurs on gross movement but not on fine movement . Loss of deep and cutaneous reflexes in the opposite side.

29. B. Premotor area (6 , 8, 44, & 45) Area 6 Location: anterior to area-4 Body representation: crossed & inverted Connections : It projects efferent fibers to area 4 and sensory areas via sub cortical fibers, : Receives from thalamic nuclei, Function of area-6 It cooperates with area-4 in control of coordinated voluntary movement . Isolated stimulation of A-6 initiates coordinated Gross movement in the opposite side of the body (flexion, extension)

30. Cont.… Weak inhibition of stretch reflex and grasp reflex ( suppresses muscle tone). Initiates gross movements that involve groups of muscles to support and' facilitate fine movement(Hand skill area) Execute skilled movement and gestures . Center for head rotation -Directs the head to objects ( Head rotation area) The lower part of area-6 controls complex movement of facial expression, jaws, tongue, larynx, pharynx and respiratory muscles. It initiates an automatic (involuntary) movements performed subconsciously ( swinging movement of arms during walking ). Center for verbalization Involved in the control of the ANS.

31. Cont.… Effect of lesion to A-6 Muscle paresis in the opposite side Increase in muscle tone & muscle rigidity Exaggerated tendon jerk Appearance of grasp reflex Motor apraxia/dyspraxia if mild : loss of ability to execute skilled movement and gestures . Eg: whistling, winking, coughing voluntarily. Agraphia : loss of previous ability to write due to lesion to exner´s center (NB: It is not associated with ability to read)

32. Cont.… Frontal eye field area (8) Located above the Broca´s area Direct eyes to a desired field Center for voluntary eye movement (voluntary fixation and blinking movement ) Connected to the visual center in the occipital lobe:-Controls movement of eye & eyelid Lesion : F ixation (locking) of the eye on specific objects Broca´s area/Speech center (44 & 45)- word formation area Lesion : M otor aphasia ( Failure of speech articulation /vocalization/ unable to speak or write or understand language in extreme cases )

33. C. The supplemental motor area Location : in medial A6 Topographic representation of body : horizontal and inverted manner Functions: Programming of complex movements. Involved in preparation (readiness) for movements ( readiness). Supplement the functions of the PMA /A6 in gross position of the body. Lesion: impaired ability to self-initiate learned movements and sequence of movements.

34. D . Motor association area ( areas-9, 10, 11 & 12) Occupies the anterior part of the frontal lobe It is called the organ of mind Connections : It has connections with the HT, thalamus, limbic system, motor areas, the temporal and occipital lobes . Effect of lesion : Mental impairment , lack of initiatives and self control, loss of attention Change in social behavior , disorientation of time and space Functions: Involved in the higher intellectual functions of the brain; planning, intelligence and elaboration of thought. Due to its connection with hippocampus , it is involved in the storage of recent memory . Due to its connection with HT , it is involved in the control of the ANS Due to its connection with the limbic system , it is involved in the control of emotional behaviors.