BISC 421 1st Edition Lecture 1Outline of Current LectureI. Cell Biology of the NeuronCurrent LectureCell Biology of the NeuronThe major components of the nervous systemo 1. Central Brain and spinal cordo 2. Peripheral Detects environment outside and inside Temperature, heart rate, hunger Visual system, auditory system Detected by sensory receptors in neuron Visceral system: Gut Motor systemMovement Effectors Modulated by nervous activity (muscle) How fast heart beatsCells of the Nervous Systemo 10^12 types of cells in the bodyo only 10% are actually neuronso 90% are glial cells (supporting cells)The Stereotypical Neurono Soma Nucleus Like any other cello Axon Makes neurons different from other cells Only one per neuron, longest part of the neuron Extends from the cell body to great distances Can make a synapse with another cell (signal output)o Dendrite Where informaton is received (signal input)Diversityo Example of different types of cellso Yellow/orange = axono Green = dendrite (the one on botom right is called dendriticarbors)o Purple = somaAxonsAxon hillock Where the signal (AP) starts First neurons will conduct signals a lot faster than second neurons- different neurons give you differentresponses Depends on myelinaton Those that are heavily myelinated will conduct signals very fast andthose that aren’t conduct signals slowlyPre-synaptic terminaloo End of the axon is the pre-synaptic terminal or the synapticboutono Where the neurotransmiters are releasedo For majority of neurons they never actually touchSynapseTransferring informaton from a pre-synaptic cell to a postsynaptc cell- communicatonDendriteso The receiving part are the dendrites on neuronso Neurotransmiter receptorso Structure of the dendrite may be a lot more complexo Spines and shafs are further extensions of the dendrite –each red dot is where another neuron is in contact withanother cell- thousands of synapseso These are constantly changing- number of connectons can change with plasticityTypes of connectionsoo 1. Axo-dendritc Classical type Middle picture If on a spine- excitatory If on a shaft- inhibitoryo 2. Axo-somatic (left) Synapse on the somao 3. Axo-axonic (right picture)o A neuron can have all three types of connectons Slide 10- Cytoskeletonoo Contributes to the structure of the cello actn filaments- involved in very motile structureso Microtubules- involved in the movement of material-Axonal Transporto Cytoskeleton is involved in axonal transporto Since proteins are made in the cell body the axonal transportis important for transporting these proteins to other parts ofthe bodyo Two types of transport: 1. Anterograde: cell body to nerve terminal useful for growth 2. Retrograde: nerve terminal to the cell body for degradationNeurons have polarityo Microtubules have a certain symmetry within the neurono For axon: + to –o Have motor proteins which is a protein that uses energyKinesins and DynesinsGliaoo Makes up the majority of the nervous systemo Oligodendrocytes and Schwann cells have similar functonso Astrocytes most common type (on the left)o Differ because: 1. Do not form synapses- don’t have same type ofcommunicaton 2. Only one type of process- no polarity 3. Retain ability to divide- divide a lot- neurons have lost this ability 4. Not electrically excitable- will not really fire APAstrocytesoo Role is to support neurons- structural support, guiding where an axon will project. Surround and support the structure of the synapseo Help control potassium concentrationso Can facilitate the regulaton of metabolism- help provideglucoseo Main role is to control the neurotransmission- in removal ofNT from the synapse-Oligodendrocytes and Schwann cellsoo Essentally same functono Myelin comes from these cells- they wrap around the axon toprovide the myelin sheatho Oligodendrocytes- central nervous systemo Schwann cells- PNSMicrogliao The most crucial- not derived from neural tssue but a part ofthe immune systemo Activated by a tissue- will phagocytose foreign antigensneural circuitsoo Neurons don’t work in isolaton- function in neural circuitso Hammer Tap reflex: 1. Hammer taps- hits tendon and when this is moved itis sensed by sensory neuron in muscle 2. Sensory neuron sends signal to the spinal cord.Neural Circuit in spinal cord composed of sensory, motor, and interneuron (inhibits other neurons) 3. Motor neurons are actvated to move the muscleKnee-Jerk Responseoo The motor neuron that goes to the extensor and the motor neuron that goes to the fexor Flexor motor neuron is inhibited when the hammer tapsbut the extensor activity is activated- one muscle must contract (extensor), while the other relaxes (flexor) Interneurons are actve too because it is sending an inhibitory signal to the fexor muscleIntracellularly recorded responses during knee-jerk reflexo Stck electrode into the sensory neurono Increase in activity in the extensor motor neuron andinterneurono Decrease in the activity of the fexor motor