Nervous System, Neuroglial Cells, Classification Of Neurons, Neuron Impulse, And Synaptic Transmission

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Central nervous system

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Consists of the brain and spinal cord

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Peripheral nervous system

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Nerves that connect the CNS to other body parts

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Sensory functions

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Derives from sensory receptors. Monitor external and internal environmental changes

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Integrative function

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Occurs in the CNS. Creates sensations. Adds to memory. Translates sensations into perceptions. CAUSES US TO MAKE CONSCIOUS OR SUBCONSCIOUS DECISIONS.

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Motor functions

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Are used to act upon the results of sensory and integrated functions. Send peripheral neurons from the CNS to effectors.

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Effectors

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Muscles that contract and glands that secrete when stimulated by nerve impulses

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Neurons

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Cells that carry information through the nervous system also called "nerve cells"

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Dendrite

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Part of neuron that receives information from other cells (like antenna)

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Cell body

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Main part of a neuron: collects information from dendrite and passes it on to other parts of the neuron

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Chromatophilic substance

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Ribosomes attach and proteins are made in the cell body

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Axon

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Extension of neuron that carries impulses (electrical signals) away from the cell body

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Axon/synaptic terminals

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Branched end of an axon leading to the synaptic knob, then to the synapse

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Schwann cells

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Type of cell in the PNS that surrounds a fiber forming the neurilemmal sheath and myelin

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Myelin sheath

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Layers of lipid proteins surrounding the axon providing insulation

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Neurilemma

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Sheath formed from schwann cells surrounds myelin sheath on the axon

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Nodes of ranvier

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Gaps in the myelin sheath between schwann cells on the axon

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Synaptic knob

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Tiny enlargement at the end of an axon that makes, holds and secretes neurotransmitters

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Synapse

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The junction at which a neuron meets another cell and exchanges chemical or electrical impulses

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Neuroglial cells

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Cells that aid the nervous system

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Microglial cells

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Support neurons and phagocytize bacterial cells and cellular debris

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Oligodendrocytes

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Provide insulating layers of myelin around axons with the CNS

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Astrocytes

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Provide structural support, join parts by cellular process, regulate the concentration of nutrients and ions, dorm scar tissue within the CNS

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Ependymal

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Forms membrane that covers specialized parts of the brain, forms inner linings that enclose spaces within the brain

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Neuron cell structure

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Contains all the basic organelles. Consists of neurofibrils, which extend into the axon. Mature neurons do not divide

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Bipolar neurons

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Located in the eyes, nose and ears with two extensions off of the cell body

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Unipolar

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Neuron with one extension coming off of the cell body that leads into a peripheral branch: Where dendrite are attached to a peripheral body part. Central branch: Where axon terminal enter brain and spinal cord

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Ganglia

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Specialized masses of nervous tissue, which are located outside the brain and spinal cord

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Multipolar

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Many branches extending from the cell body. Only one branch is an axon the rest are dendrites. Mostly found in the brain or spinal cord

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Sensory neurons

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Carry nerve impulses from peripheral body parts into the brain or spinal cord

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Interneurons

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Located only within the brain or spinal cord

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Motor neurons

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Carry nerve impulses out of the brain or spinal cord to effectors

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Summation

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The addition of stimuli that leads to a level called threshold. Threshold causes an action potential.

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potential difference

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The difference in electrical charges between two regions

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Cell membrane potential

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Distribution of ions na to k ratio, determined by selective membranes

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Resting potential

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The potential difference between the area inside a cell (-) and the area outside a cell (+)

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Potential changes

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Any external or internal stimuli that causes a change in the resting potential

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Depolarizing

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Resting potential decreases, inside of cell becomes less negative by increasing Na inside the cell causing action potential

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Action potential

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Transmission of a electrical signal along an axon. Caused by the change in electrical gradient due to the depolarization

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Nerve impulse

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A series of action potentials traveling down a axon

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Refractory/ repolarization period

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Amount of time necessary for an axon to return to resting potential so it can be stimulated again

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Impulse conduction

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Unmyelinated axon conducts impulse over entire surface. Myelinated axon conducts impulse at nodes of ranvier. Myelin prevents the conduction!!!!!!

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All or none response

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Nerve impulse is conducted whenever a stimulus of threshold intensity or above is applied to an axon. Greater intensity of stimulation produces more impulses per second

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Nerve pathway

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Path where impulses travel from neuron to neuron

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Synapse

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Junction between two communicating neuron

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Synaptic cleft

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Space between two neurons that the impulse jumps through

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Synaptic transmission

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Diffusion of neurotransmitters from an axon terminal to a dendrite

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Excitatory neurotransmitters

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Increase postsynaptic membrane permeability to sodium ions. Causes threshold that causes impulse

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Inhibitory neurotransmitters

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Decrease postsynaptic membrane permeability to sodium ions. Inhibits threshold, block impulse

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Nerve

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Cordlike bundle of nerve fibers held together by layers of connective tissue

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Sensory nerves

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Nerves that conduct impulses to the CNS

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Motor nerves

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Carry impulses to effectors from CNS

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Mixed nerves

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Contain sensory and motor

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Nerve pathways

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The route nerve impulses travel through the nervous system

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Reflex Arc

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Simplest nerve pathway which includes only a few neurons