Nervous Tissue Concepts Flashcards
Describe the organization of the nervous system.
1st Split: CNS vs. PNS
Central Nervous System(brain and spinal cord) and Peripheral Nervous System(everything outside)
2nd Split: Within the PNS
Somatic nervous system(SNS), Autonomic nervous system(ANS), Enteric nervous system(ENS)
3rd Split: within ANS
Sympathetic vs. parasympathetic
Describe the three basic functions of the nervous system.
Sensing= sensory message sent to the CNS via circulation of blood, or from the receptor to the CNS via sensory neurons (ex: see brake lights flashing)
Integrating= occurs within the CNS via interneurons of association neurons. Usually in the brain, but sometimes just in the spinal cord (ex: decide really quickly to slam brakes)
Responding= response can be delivered from the CNS to the effectors via hormones, or motor neurons (moving the foot to brake and push hard)
Contrast functions of the Somatic, Autonomic & Enteric N.S.
Somatic= Monitors and powers skeletal muscles
Autonomic= Monitors and powers smooth muscles of the viscera, cardiac muscle, and glands
Enteric= Monitors and powers smooth muscles, glands, and endocrine cells of the GI tract, very specifically
Contrast antegrade and retrograde transport in an axon.
Anetgrade moves material from the cell body to the axon terminal
Retrograde moves material from the axon terminals back to the cell body
Contrast the structure of the 3 types of neurons. Provide the general location of each of the 3 as either “sensory”, “interneurons”, or “motor”
Multipolar(motor, ex: brain and spinal cord)= usually has lots of dendrites coming off the body and one axon. Most neurons in the CNS and all most neurons of the PNS have this shape
Bipolar (interneuron, ex: eyes)= one main dendrite (which can branch later) and one axon. Special sensory neurons
Unipolar(sensory. Ex: cranial nerve) = dendrites and axons fuse together to form one continuous process that extends from the cell body. Sensory receptors!! The cell bodies are usually clustered in the ganglia of spinal and cranial nerves.
Contrast myelination via oligodendrocytes with myelination via Schwann cells with INSULATION of unmyelinated axons by Schwann cells.
Oligodendrocytes can myelinate several parts of different axons
One Schwann cell can myelinate one section of one axon
One Schwann cell can enclose several unmyelinated axons (insulate)
Contrast grey and white matter structurally
White matter= myelinated= white color
Gray matter= unmyelined= nissl bodies color show, resulting in a gray color
Contrast tracts & nerves. And contrast nuclei & ganglia
Tracts are bundles of axons found in the CNS, and nerves are bundles of axons found in the PNS
Nuclei are collections of cell bodies found in the CNS, and ganglia are collections of cell bodies in the PNS
Contrast depolarizing & hyperpolarizing graded potentials.
Depolarization is when the membrane potential becomes more positive.
Hyperpolarization is when the membrane potential becomes more negative
Contrast temporal & spatial summation
Temporal summation involves a single presynaptic neuron rapid-firing signals to a single postsynaptic neuron’s synapse. As the signals are being received so quickly, they summate into a greater signal.
Spatial summation involves multiple presynaptic neurons sending signals to a single neuron at the same time.
Discuss how the 3 AM freight train can be “silenced” by IPSPs.
Mechanoreceptors flooding the CNS with signals, due to the freight train, are shut down by IPSP. IPSP created at the junction shut down the signals so that it’s not sensed and keeps the transduction from being consciously “perceived.” This allows you to sleep through the sounds of the freight train at 3 am.
Compare the basic types of ion channels, and explain how they relate to graded potentials and action potentials.
Leak channels= set the resting potential, but don’t really participate in graded potentials or action potentials
Mechanically gated channels=create depolarizing graded potential that can lead to an action potential
Ligand-gated channels= create depolarizing graded potential (EPSP) that can lead to an AP (similar to what we see at NMJ using ACh)
Voltage-gated channels= do nothing until the summed depolarization graded potential brings the resting potential up past -55 mV. They explode open to start the all or none AP.
Describe the factors that maintain a resting membrane potential.
Leak Channels for Na+, K+, and Cl-
- They randomly open and close, there are more K+ than others and those for K+ are “leakier”
- The net effect is to make the inside of the neuron more negative since K+ will always leave the neuron via leak channels
The inability of most anions to leave the cell (Donnan Equilibrium)
- ATP and proteins are polyanionic and do not travel across the cell membrane.
- Contributing to the overall negative charge of the cell
Na/K-ATPase pump exchanges Na for K across the membrane but not equally
- 3 Na+ goes out of the cell for every 2 K+ that it brings in
Describe the classes and functions of neurotransmitters
Excitatory neurotransmitters “excite” the neuron and cause it to “fire off the message,” meaning, the message continues to be passed along to the next cell.
Inhibitory neurotransmitters block or prevent the chemical message from being passed along any further
Identify the various types of neural circuits in the nervous system.
Simple series circuit, neural circuits: diverging and converging, neural circuits: reverberating and parallel after discharge
