lecture from 1/15

1-15 Physiological Techniques Goal Determine the relation between a particular structure or area of the brain and its role in the control of movement Several approaches to accomplish it: Record brain correlates of movement How to record: 1. Humans ? fMRI, EEG Animals ? intra-coritcal microsstimulation (ICMS) Stimulate brain Observed elicited responses How to stimulate brain in humans and animals: ICMS Don?t have pain receptors in the brain Interfere with brain function ? observe deficits How to perform on humans ? Transcranial Magnetic Stimulation (TMS); lesion studies Patient studies ? people get brain lesions from strokes, degeneration, tumor removal, etc. Disadvantages with patients ? lesion extent, access to patients, rest of brain adapts Animals ? temporary or permanent lesions fMRI ? Functional Magnetic Resonance Imaging localizes neural activity by examining regional cerebral blood flow measures changes in blood flow if you are holding your breath more blood will be directed from somewhere else in your body to your brain to prevent the neurons from dying Electr-encephalography (EEG) Neural activity is electrical in nature It is possible to measure this electrical activity on the scalp Weak signal? Many things in the way that can interfere with the signal making it weak Many trials have to be collected and averaged Animal Studies Train animal to perform the task Perform surgery to gain access to the brain area of interest Insert microelectrode into brain to record electrical activity from neurons while the animal performs the task, continue to move the electrode to figure out what part of the brain is involved in performing that task Nervous System Components Movement Basics Two necessary for movement: Muscular system Creates movement via contraction/relaxation of muscle fibers Muscles are ?motors? Nervous system Dictates muscle activity Nerves are ?controllers? Central & peripheral subsystems (CNS&PNS) Central Nervous System All neurons and glia that are entirely contained within the brain and/or spinal cord CNS Hierarchical Organization ? more complex tasks are performed higher in the brain Medulla oblongata controls breathing, visceral functions, etc Cerebellum Controls coordination during walking, picking up things etc. Pons Transmits messages from brain stem to brain Cerebrum Makes up of the bulk of our brain tissues and controls personality, memory, attention, etc. Divided into four major lobes Frontal Parietal Occipital ? vision is processed Temporal Brain facts ~1.4 Kg (3 lbs) >100 billion neurons >1 trillion glial cells Peripheral Nervous System All neurons and glia that are not entirely contained within the brain and/or spinal cord Cranial Nerves (12) Supraspinal Spinal nerves (31) Alpha motorneurons Directly communicate with your muscles Originate in the spinal cord and exit into the muscles The neuron Nucleus Genetic center of the cell Dendrites Receive information from other neurons and send to cell body Unidirection flow of information Cell body (soma) sums information from dendrites/other terminals Axon transmits information from the cell body PS terminal Attaches to other neurons to relay information Neuron classification Sensory neurons Deliver into to the CNS from endings on the surface of the body and within muscles and tendons Gives us information about the body relative to the environment Afferent: carrying info towards the CNS Motor neurons Neurons connected to muscle cells which cause muscle contractions (i.e. movement) Necessary to perform any type of voluntary movement activity Efferent: carrying info away from CNS Interneurons Performs processing functions Memory Planning Connect multiple neurons with (multiple) other neurons Account for the majority of neurons in the nervous systems Glial cells ??glue? Insulate, support, and nourish neighboring neurons Outnumber neurons: 10:1 Astrocytes Most numerous type of glial cell They help form blood brain barrier Helps protect from viruses, bacteria etc Prolific astrocytes can lead to brain cancer Oligodendroctyes Produce myelin sheaths Form myelin for axons in CNS Schwann cells produce myelin sheaths from myelin for axons in PNS Myelin Key glial cells Oligodendroctyes (CNS) Schwann cells (PNS) One Oligodendroctye glial cell will produce multiple myelinated axon One myelin cell will produce 7 schwann cells Cover the axon of neurons Acts as insulator Speed up transmission of neural impulses Helps contain and insulate signal Without myelin muscles are weaker because each neuron does not receive the same amount of signal and may be lost by the time it gets to the certain site. Affects pain receptors and can cause major pain