Transcript Nerve Cells
Nerve Cells The Neuron Fun facts about neurons Most specialized cell in animals Longest cell: blue whale neuron 10-30 meters giraffe axon 5 meters human neuron 1-2 meters Nervous system allows for 1 millisecond response time 3 parts of a Neuron 1) Dendrite – branched end that extends out from the cell, provides a large surface area to receive nervous information 2) Cell Body – control center, regular cell organelles (nucleus etc) 3) Axon – long thin fiber, extends out from cell body, carries action potential from cell body -ending are called synaptic terminals Nervous system cells Neuron signal direction a nerve cell dendrites cell body axon Structure and function many entry points for signal one path out transmits signal signal direction synapse dendrite cell body axon 3 Types of Neurons 1) Motor – connects to a muscle or gland 2) Sensory – receives a stimulus 3) Interneuron – connects the above 2 Myelin Sheath -Myelin Sheath covers some axons Myelin Sheath -Formed by a type of neuroglia called Schwann cells Myelin Sheath -Schwann cells contain a lipid called myelin in cell membrane -Schwann cells wrap around axon many times Nodes of Ranvier- gaps between Myelin sheaths Reflex Rapid, predictable, and involuntary responses to stimuli Reflex arc Direct nervous message from a sensory neuron to inter-neuron to a motor neuron to an effector (a muscle or a gland) Video Reflex Arc A motor, sensory and inter neuron form a reflex arc Begins with a stimulus causing an impulse in the sensory receptors of a sensory neuron. The impulse then continues on through the dendrite, cell body and axon of a sensory neuron (DCA). The impulse passes to the interneuron, passing through dendrite, cell body and axon (DCA). The impulse passes onto the motor neuron, passing through the dendrite, cell body, and axon (DCA). This causes a response in an effector (a muscle or a gland) Reflex Arc Reflex Arc Nerves Combination of nerve cell fibers Sensory dendrites and motor axons Summary Neuron Types Sensory Neuron Interneuron Motor Neuron Structure Long dendrite Short axon Short dendrite Short axon Short dendrite Long axon Function Conduct impulse to cord Interconnect sensory neurons with motor neurons Conduct impulse to effector (muscle/ gland) Location Cell body/ dendrite outside spinal cord Cell body- dorsal root Cell body/ dendrites in spinal cord Axon outside spinal cord Entirely within CNS Synapses/ synaptic gap Synapse- region of close proximity Synaptic gap- Space between a neuron (axon terminal) and the next cell The next cell could be another neuron or an effector (muscle/ gland) Space between must be bridged by neurotransmitters More on neurotransmission and nerve impulses tomorrow! Synapse