From Neuron To Brain, basics of neuroscience.pptx

a presentation about basic concepts of neuroscience and neural plasticity.

1. Basics From Neuron To Brain

2. Hello! I’m Heba el saeid 2

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4. What are we going to cover today ? 4 the components of our Nervous system The neuron The brain Plasticity Neural plasticity Muscle plasticity Cortical plasticity Movement control from neuron to brain Role of somatosensory system in movement control Stretch reflex Cortical areas involved in motor control Basal ganglia cerebellum

5. 1. T he Nervous System

6. The Nervous System The nervous system is a complex collection of nerves and specialized cells known as neurons that transmit signals between different parts of the body. Structurally, the nervous system has two components: the central nervous system and the peripheral nervous system. Functionally, the nervous system has two main subdivisions: the somatic, or voluntary, component; and the autonomic, or involuntary, component. 6

7. The Central Nervous system The CNS consists of the brain and spinal cord. The brain is the most complex organ in the body and uses 20 percent of the total oxygen we breathe in. The brain consists of an estimated 100 billion neurons, with each connected to thousands more. 7

8. The Peripheral Nervous system The term peripheral nervous system (PNS) refers to any part of the nervous system that lies outside of the brain and spinal cord. The CNS is separate from the peripheral nervous system, although the two systems are interconnected. 8

9. The Neuron Neurons are cells within the nervous system that transmit information to other nerve cells, muscle, or gland cells. Most neurons have a cell body, an axon, and dendrites. Dendrites extend from the neuron cell body and receive messages from other neurons. Synapses are the contact points where one neuron communicates with another. 9

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11. When neurons receive or send messages, they transmit electrical impulses along their axons, which can range in length from a tiny fraction of an inch (or centimeter) to three feet (about one meter) or more. Many axons are covered wit the myelin sheath, which accelerates the transmission of electrical signals along the axon. This sheath is made by specialized cells called glia. In the brain, the glia that make the sheath are called oligodendrocytes, and in the peripheral nervous system, they are known as Schwann cells. 11

12. The brain 12

13. 13 W hat makes it so special ?

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15. Neuroplasticity The capacity of the nervous system to change is demonstrated in children during the development of neural circuits, and in the adult brain, during the learning of new skills, establishment of new memories, and by responding to injury throughout life. Learning an activity is synapse and circuit specific, and can be modified with synaptic transmission being either facilitated (strengthened) or depressed (weakened). 15

16. The synapse 16

17. Cortical plasticity Cortical representation areas have been found to be modified by sensory input, experience and learning, as well as in response to brain injury. Cortical areas response to changing input which can either be upgraded or downgraded, such as remapping in subjects following amputation, where there is a reduced representation of the affected area and an increase of representation of adjacent areas within the cortex 17

18. Muscle plasticity Like neuroplasticity, the adaptability of muscle has been investigated extensively. Skeletal muscle is one of the most plastic tissues in the human body Every structural aspect of muscle, such as its architecture, gene expression, fiber type distribution, number and distribution of alpha motor units and much more. With an increased demand there is a shift from fast to slow fiber types, an increase in size and number of mitochondria and an increase of the capillary density with an overall hypertrophy of the muscle 18

19. 2. Movement control from neuron to brain

20. Motor control

21. Motor control, the ability to maintain and change posture and movement. Movement arises from the interaction of perception and action systems, with cognition affecting both systems at many different levels.. Movement control is achieved through the cooperative effort of many brain structures that are organized both hierarchically and in parallel. 21

22. Role of somatosensory system in movement control Sensory inputs serve as the stimuli for reflexive movement organized at the spinal cord level of the nervous system. sensory information has a vital role in modulating the output of movement that results from the activity of pattern generators in the spinal cord (e.g., locomotor pattern generators).

23. Another role of sensory information in movement control is accomplished via ascending pathways, which contribute to the control of movement in much more complex ways. 23

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25. 25 the muscle spindle

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27. Muscle Spindle encapsulated spindle-shaped sensory receptors located in the muscle belly of skeletal muscles. They consist of Specialized very small muscle fibers, called intrafusal fibers (nuclear chain and nuclear bag fibers) Sensory neuron endings (group Ia and group II afferents) that wrap around the central regions of these small intrafusal muscle fibers. 27

28. gamma motor neuron endings that activate the polar contractile regions of the intrafusal muscle fibers. Muscle spindles detect both muscle length and changes in muscle length, and along with the monosynaptic reflex, help to finely regulate muscle length during movement. the highest spindle density (spindles per muscle) are in the extraocular, hand, and neck muscles. 28

29. Golgi Tendon Organs Golgi tendon organs (GTOs) are spindle-shaped and are located at the muscle-tendon junction. The GTO is sensitive to tension changes that result from either stretch or contraction of the muscle. The GTO responds to as little as 2 to 25 g of force. The GTO reflex is an inhibitory disynaptic reflex, inhibiting its own muscle and exciting its antagonist. Afferent information from the GTO is carried to the nervous system via the Ib afferent fibers. 29

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31. Gamma Motor Neurons Both the bag and chain muscle fibers are activated by axons of the gamma motor neurons. It changes the sensitivity of the muscle spindle ( the stretch receptor ) and therefore prevents the unloading . 31

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33. 33 Facilitatory Inhibitory Primary motor area 4 Neocerebellum Facilitatory reticular formation Vestibular neuclus Cortical suppressor area 4s Paleocerebellum Inhibitory reticular formation Red nucleus Basal ganglia

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35. Role of stretch reflex in movement control Servo-assist function during muscle contraction by the alpha-gamma link Damping function (smoothness of contraction) 35

36. 36 Cortical areas involved in motor control

37. Cortical areas involved in motor control Primary motor cortex and two other areas including: The supplementary motor area (SMA) The premotor cortex They also interact with sensory processing areas in the parietal lobe, basal ganglia and cerebellar areas to identify where we want to move, to plan the movement, and finally, to execute our actions 37

38. All three of these areas have their own somatotopic maps of the body. Inputs to the motor areas come from the basal ganglia, the cerebellum, and sensory areas, including the periphery (via the thalamus), SI, and sensory association areas in the parietal lobe. MI neurons receive sensory inputs from their own muscles and also from the skin above the muscles. 38

39. Outputs from the primary motor cortex contribute to the corticospinal tract (also called the pyramidal tract) The corticospinal tract includes neurons from primary motor cortex (about 50%), and premotor areas including supplementary motor cortex, and even somatosensory cortex. The fibers descend ipsilaterally, (90%) cross to form the lateral corticospinal tract, controlling precise movements of the distal muscles of the limbs. The remaining 10% continue uncrossed to form the anterior ( or ventral) corticospinal tract, controlling less precise movements of the proximal muscles of the limbs and trunk. 39

40. The majority of the anterior corticospinal neurons cross just before they terminate in the ventral horn of the spinal cord. It has been shown that specific neurons in the cortex, activated when we pick up an object, may remain totally silent when we make a similar movement, such as a gesture in anger. Simply by training a patient to utilize a specific set of muscles to make a particular movement in one situation does not automatically mean that the training will transfer to all other activities requiring the same set of muscles 40

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42. Supplementary Motor Area Movements that are initiated internally are controlled primarily by the SMA. This area also contributes to activating the motor programs involved in learned sequences. Interestingly, the SMA receives inputs from the putamen of the basal ganglia complex. 42

43. Premotor Area Movements that are activated by external stimuli (e.g., a visual cue such as a traffic light changing from red to green) are controlled primarily by the premotor area. It receives inputs from the cerebellum. Nerve signals generated in the premotor area cause much more complex “patterns” of movement than the discrete patterns generated in the primary motor cortex. 43

44. A special class of neurons called mirror neurons becomes active when a person performs a specific motor task or when he or she observes the same task performed by others. Thus, the activity of these neurons “mirrors” the behavior of another person as though the observer was performing the specific motor task. 44

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46. The basal ganglia

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49. Functions of the basal ganglia Planning sequences of patterns of movement ( Caudate Circuits ). Exciting subconscious learned movement patterns ( Putamen Circuits ) Initiation and regulation of gross intentional movement Posture taken by the body to perform a particular voluntary movement. Inhibition of muscle tone 51

50. The Cerebellum

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52. 54 Lobe Connected to Function Paleocerebellum or spinocerebellum AHCs - Coordination of movement Inhibition of muscle tone Neocerebellum or cerebrocerebellum Cerebral cortex Planning and programming of movements Facilitatory to muscle tone Archicerebellum or vestibulo-cerebellum Vestibular nuclei - Concerned with equilibreium

53. Other functions of the cerebellum Comparator function ( feedback and feedforward ) The braking effect of the cerebellum 55

54. 56 Thanks! Any questions? You can find me at [email protected]