BISC 421 1st EditionExam 2 Study GuideI. BRAIN STRUCTURE Know the 3 main divisions of the brain and be able to associate large structure with each 1. Forebrain: Cerebral Cortex, Basal Ganglia, thalamus, hypothalamus 2. Midbrain: Tectum 3. Hindbrain: Cerebellum, pons, medulla oblongata Know the names of the four lobes of thecerebral cortex 1. Frontal lobe 2. Parietal Lobe 3. Temporal Lobe 4. Occipital Lobe Know your planes of secton (Coronal, Sagital, Horizontal) Be able to answer questons like: If I slice your brain so that I cut through your frontal and occipital lobe – have I cut? a) A coronal section b) A horizontal section c) A sagital section d) A coronal or horizontal section e) A coronal or sagital section f) A sagital or horizontal section Is the spinal cord part of the CNS or the PNS? It is part of the CNS II. SPINAL CORD AND MOTOR SYSTEM What is the diference between an upper and lower motorneuron (think about which type synapses with muscle)? Are there lower motor neurons in both the brainstem and spinal cord or just the cord? Are there upper motor neurons in the cortex and brainstem or just the cortex? 1. Upper motor neuron: in brainstem and cortex involved with the motor cortex and the brainstem centers. They synapse not onto muscles themselves but other neurons2. Lower motor neurons: located in the spinal cord and will synapse onto skeletal musclesWhat is the diference between a motor pool and motor unit?1. Motor pool: the group of motor neurons that innervate a single muscle. Can comprise of more than one type of motor unit.2. Motor unit: The group of muscle fbers that receive input from a single motor neuronWhich region of the spinal cord houses motorneurons?The VENTRAL HORN house the cell bodies of the motor neurons and ventral roots contain axons of lower motor neurons that travel out (EFFERENT) towards muscle. Think SAME-‐DAVE(sensory-‐aferent, motor-‐eferent; dorsal-‐aferent, ventral-‐eferent)Do you expect that to fnd larger or smaller motor units associated with muscles thatguide fine movements like those direct our eyes, lips and fingers?You would expect to fnd smaller motor units that have a very high proporton of muscles fibers capable of contractng with maximal velocityWhich muscle do you think would be more resistant to fatgue. A muscle involved in maintaining posture or one involved in movements associated with atack or escape?You would expect a muscle involved in maintaining posture to be more resistant tofatgue than one associate with atack or escape because it probably has smallerfatgue resistant fbers than the other which has more larger fast fatgue able fbersAlpha motor neurons innervate extrafusal muscle fbers. What about gamma motorneurons?Gamma motor neurons innervate intrafusal fbers and they regulate the sensitvity of the muscle spindle by pulling at both ends of the bag and chain fbers, so stretching regions where the aferent endings are wrappedWhich type refex involve muscle spindlesThe monosynaptc stretch refex: which maintains muscle lengthGroup 1a and group II fbers carry informaton from which intrafusal muscles? What kind of information does each provide (e.g. length and/or velocity)?1a: sensory aferents carry informaton from the bag and chain fbers (more actve with muscle length is changing)II: Sensory aferents wrap around chain fbers only and most actve when muscle is stretchedWhat sort of informaton does the Golgi tendon organ convey, via which type of aferent?The golgi tendon organ conveys informaton about the state of the muscle such as force or tension in the muscle. They are capsules encasing group 1b aferents that wrap around collagen fbrilsBe able to draw the spinal refex arc for input from the muscle spindles and (the simple version illustrated in the slide and animaton – not as illustrated in the book).8" 8"99"What cortcal regions supply the fbers that descend through the cortco spinal andbulbar tracts?They both originate in the motor and premotor cortex but the cortcobulbar region ends in the brainstem and the cortcospinal region ends in the spinal cord and crosses at midlineWhat is the main functonal diference between the anterior and lateral cortico-‐spinal tracts?Lateral: Most fbers cross at the pyramidal decussaton (medulla) and terminate on the lateral motor neurons, including those that move distal muscles like fngers and toesAnterior: Crosses at the cord and makes bilateral and polysynaptc connectons with medial motorneurons that are used to maintain postureIII. BASAL GANGLIAKnow the direct and indirect pathways in the basal ganglia. Memorize the block diagrams from lecture, remember which regions send excitatory projectons to their targets and which send inhibitory projectons. Eg. the striatum sends inhibitory projectons and the subthalamic nucleus sends excitatory projectonsRemember where cells are silent unless actvated and where cells fre tonically unlessinhibited.CortexGlutamate (+)PutamenGlutamate (+)GABA (-)Glob. Pal. Int.GABA (-)VA/VL ThalamusAll silent except GLOB PAL INT which is tonically activeCortexGlutamate(+)PutamenGABA (-)Glob. Pal. ext.Glutamate (+)GABA (-)'Sub Thal. Nuc.Glutamate(+)'Glob. Pal. Int.GABA (-)'VA/VL ThalamusAll silent except GLOB PAL INT and GLOB PAL EXT which are tonically activeWhich pathway acts as the accelerator and which as the brake on movements?The direct pathway acts as the accelerator and the indirect pathway puts on the brakesIf you were to see a diagram of a pathway on the exam, would you be able to indicate which structures are inhibitory and which are excitatory. Would you be able to pick out a mistake? Would you be ableto predict what symptoms a patent might have (eg. inability to initate movement vs. inability to control or restrain movement) if a partcular region were damagedParkinsons is the loss of dopaminergic neurons in the substansta nigra-‐ leads to slowed impaired movement, rigidity, and pill rolling tremorWhen the subthalamic nucleus is lost, actvity in Glob. Pal. Int. is reduced– the VA/VL receives too litle inhibiton and goes into overdrive and over excites cortex.•If we lose dopamine we lose the ability to initate movementHUNTINGTONS: loss of striatal neurons leads to changes in coordinaton and involuntary movementsLoss of the Putamen reduces inhibiton of the Glob. Pal. ext , which results in increased cortcal actvityUnderstand how structures can be excited directly, by