Nervous System Flashcards
Neurons
Specialized cells capable of transmitting electrical impulses and then translating those into chemical signals
Dendrites
Part of the Neuron:
Receive incoming messages from other cells
Cell Body (Soma)
Part of the Neuron:
Where nucleus, ER and ribosomes are located
Axon Hillock
Part of the Neuron:
Integrates incoming signals and plays and important role in action potentials
Action Potentials
Part of the Neuron:
Transmission of all-or-nothing electrical impulses down the axon
Axon
Part of the Neuron:
Long appendage
Myelin
Part of the Neuron:
Insulates the nerve fibers to prevent signal loss or crossing of signals
Myelin Sheath
Part of the Neuron:
Maintain electrical signal within one neuron and increases speed of conduction in the axon
Schwann Cells
Glial Cell: Part of the Neuron:
Produce myelin around axons in peripheral nervous system
Oligodendrocytes
Glial Cell:
Produce myelin around the axons in central nervous system
Nodes of Ranvier
Part of the Neuron:
Small breaks in the myelin sheath which expose the axon membrane and are critical for rapid signal conduction
Nerve Terminals (Synaptic Bouton)
Part of the Neuron:
Maximize neurotransmission to the next neuron and ensure proper release of neurotransmitters
Synaptic Cleft
Small space between neurons
Synapse
Nerve Terminal + Synaptic Cleft + Post Synaptic Membrane
- Where neurotransmitters release from axon terminal transverse the synaptic cleft and bind to receptors
Nerves
Multiple neurons bundled together - can be sensory, motor or mixed (depending on the type of info. they carry)
Tracts
Axons bundled together BUT can carry only one type of information
Astrocyte
Glial Cell:
Nourish neurons and form the blood brain barrier which controls the transmission of solutes from the blood stream into the nervous tissue
Ependymal Cells
Glial Cell:
Line the ventricles of the brain and produce the cerebrospinal fluid which physically supports the brain and serves as a shock absorber
Microglia
Glial Cell:
Phagocytic cells that ingest and breakdown waste products and pathogens in the central nervous system
Glial Cells
- Astrocytes
- Schwann Cells
- Oligodendrocyte
- Microglia
- Ependymal Cells
Resting Membrane Potential
Potential difference between the inside of the neuron and the extracellular space (about -70mV) with inside of the neuron being negative
Na+ / K+ ATPase
Restore [ ] gradient transporting 3Na+ out of the cell for every 2K+ into the cell at the expense of 1 ATP.
Depolarization
Caused by excitatory input (if enough to reach the threshold causes an action potential) to raise membrane potential (mV)
Hyperpolarization
Caused by inhibitory input lowering the membrane potential
Summation
Additive effects of multiple signals
Temporal Signals
Type of Summation:
Multiple signals integrated during a short period of time
Spatial Signals
Type of Summation:
Additive effects based on the location of incoming signals
Steps of an Action Potential
- Voltage gated Na channels open and Na passes through into the cell making the membrane potential + and rapidly depolarizing
- Voltage approaches + 35mV and Na channels become inactivated triggering the voltage gated K+ channels to open
- Repolarization - K+ driven out of the cell and there is a restoration of the negative membrane potential
- Hyperpolarization - K+ Efflux overshoots the resting potential and makes the neuron refractory to further action potentials
- Na+ / K+ ATPase restores membrane potential and [ ] gradients
Absolute Refractory Period
No amount of stimulation can cause an action potential
Relative Refractory Period
Greater than normal stimulation can cause action potentials
Impulse Propagation
Action potential much travel down the axon and initiate the neurotransmitter release
**info. can only flow in one direction
Length of Axon
Longer the axon the higher the resistance and the slower the conduction of signals
Cross Sectional Area of Axon
Greater cross sectional area allows faster propagation of signals due to decreased resistance
Saltatory Conduction
Membrane is only permeable at the nodes of ranvier - Signal “hops” from node to node
Neurotransmitters in Synaptic Cleft
Must be regulated / removed form synaptic cleft
- Broken down by enzymatic reactions
- Reuptake carriers bring them back to the presynaptic neuron
- SImply diffuse out of the synaptic cleft
Ca2+ Voltage Gated Channels
Ca2+ Channels open when an action potential reaches the nerve terminal causing exocytosis of the neurotransmitter - once released it diffuses across the cleft and binds to the receptors on the postsynaptic membrane allowing message to be passed from one neuron to the next
Afferent Neurons
Afferent Signals Ascend:
Transmit sensory info from receptors to spinal cord / brain
Efferent Neurons
Efferent Signals Exit:
Transmit motor info from brain / spinal cord to muscle / glands
Interneurons
Found between other neurons and linked to reflexive behavior
White Matter
- Deep within Brain
- Axons encased in myelin sheaths on outside of Spinal Cord
Grey Matter
- Surface of Brain
- Unmyelinated cell bodies and dendrites deep within the Spinal Cord
Central Nervous System
Consists of Brain and Spinal Cord
Parts of Spinal Cord
- Cervical
- Thoracic
- Lumbar
- Sacral
Peripheral Nervous System
Nerve tissues and fibers outside the brain that connects the Central Nervous System to the rest of the body
Somatic System
Part of Peripheral Nervous System:
Sensory (afferent fibers) and motor (efferent fibers)
Autonomic System
Part of Peripheral Nervous System: Involuntary muscles (automatic) and body temp
Sympathetic Nervous System
“Fight or Flight”
- Increase heart rate
- Relax bronchi
- Decrease digestion
- Dilate eyes (max. light)
- Epinephrine released into blood
- [Glucose] in blood increased
- Redistribute blood to muscles
Parasympathetic Nervous System
“Rest and Digest”
- Slow heart rate
- Constrict bronchi
- Stimulate digestion and bile release
- Constrict pupils
- Contracts bladder
- Stimulates flow of saliva
Reflex Arcs
Neural circuits control reflexive behavior.
Interneurons in spinal cord can send signals to the muscles; info. is still sent to the brain but by the time it receives it the body has already responded
Monosynaptic Reflex
Single synapse between sensory neuron that receives stimulation and motor neuron that respond
Ex; Knee-Jerk Reflex
Polysynaptic Reflex
At least one interneuron between the sensory and motor neuron
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Ex: Withdrawal Reflex
