Nervous System Part 1 Flashcards
What makes up the Central Nervous System?
The brain and spinal cord
What makes up the Peripheral Nervous System?
Peripheral Nerves and Ganglia (clusters of nerve cell bodies that makes a swelling)
A swelling due to a cluster of neurons collecting in one area that carries sensory information from the peripheral aspects of the body into the CNS.
Dorsal Root Ganglia
A swelling due to a cluster of neurons collecting in one area that carries motor information to the peripheral aspects of the body.
Ventral Root Ganglia
Occurs when the Ventral and Dorsal Roots join together. Has sensory and motor functions.
Spinal Nerve
How many spinal nerves are there?
31 pairs
Spinal nerves very quickly divide into two components; one goes anterolaterally and the other goes dorsally/posteriorly
Dorsal or Ventral Primary Rami
Which Rami are the largest and take care of most everything?
Ventral Primary Rami
The Dorsal/Ventral Primary Rami go on to form what? Ex: Cervical Plexus is made up of VPR of C1-C5
Peripheral Nerve Branches
Receptors located on skin, joints, muscles experience a threshold stimulus that creates an action potential along the dorsal root, which enters the Spinal Cord. Spinal cord then absorbs the dorsal roots, ending with neuron sprouts coming out (Synapsing) with the ventral root.
Afferent (Sensory)
The Ventral root ganglion is located where?
Within the spinal cord
The Dorsal root ganglion is located where?
Outside the spinal cord
After synapsing with the Dorsal Root, the Spinal cord responds by sending the message out over the Ventral root (motor). Ventral root supplies response to something like a skeletal muscle.
Efferent (motor)
Most peripheral nerves are what?
Mixed (motor & sensory functions)
A component of the Peripheral Nervous System (PNS); 12 pairs coming directly off of the brain (except for one)
Cranial Nerves
Axons that deliver information to muscles that:
-have large diameters
-are heavily myelinated
-Rapidly conduct signals
Run very fast so that we can get proper responses from muscles to help us maintain posture, etc.
Somatic Efferent Fibers (motor fibers to skeletal muscles)
Supplies motor innervation to the viscera (GI tract, esophagus, stomach, cardiac, etc). Has a parasympathetic and sympathetic component.
-Entirely motor, no sensory functions
Autonomic Nervous System (ANS)
Motor fibers that have:
-a small diameter
-little to no myelin
-a slow conduction
-a two-tiered system involving preganglionic and postganglionic schema
Autonomic Nervous System (parasympathetic or sympathetic)
Fibers that originate within a nucleus (nerve cell cluster) located within the CNS (brain, spinal cord, CNs, etc).
These give off a preganglionic axon that goes into the periphery to synapse with a ganglionic structure.
Preganglionic Fibers
Fibers that originate within a ganglion (nerve cell cluster) that is located outside of the CNS. Gives off a postganglionic axon that projects to visceral structures to innervate them.
Postganglionic Fibers
1st order neuron gives off an axon that is going to synapse with a 2nd order neuron that is located within a ganglion. Then, 2nd order neuron gives off a postganglionic axon that projects to whatever the target organ is (visceral smooth muscle, cardiac muscle) to have sympathetic or parasympathetic response.
ANS Preganglionic/Postganglionic Schematic
Has a short preganglionic neuron and a long postganglionic neuron
Sympathetic
Has a long preganglionic neuron and a short postganglionic neuron
Parasympathetic
Cranial Nerves and/or Spinal Nerves respond to stimuli from the receptors out in the peripheral aspects of the body (joints, skin, muscle, etc). Signals come from receptors, enter CNS and may go into brain (CN) or spinal nerves. Then, after the information has been integrated, exits via the CN and spinal nerves to deliver motor responses to glands/muscles to produce response that was dictated by the receptors.
CNS/PNS
Input from the sensory system is associated, which tells us to respond a certain way via the motor responses.
Gives an output that reflects the input.
-If you have a lesion (Stroke, TBI), takes out this ability. Information coming in over the PNS is unable to be properly integrated, so output is not what it should be.
Integration
Have a nerve cell body (NCB) giving off a little projection called a Neurite, that joins with an axon. Picks up a nerve impulse from the dendrites, travels all the way over to axon termination.
-Impulse does not go through the nerve cell body.
Unipolar Neuron
Start with dendrites on the left and axon on the right.
-Dendrites and axon are attached to the NCB at exactly opposite poles from each other.
Bipolar Neuron
Dendrites all over the NCB and one point where the axon comes off into axon termination
-Typical neuron you would expect to see.
Multipolar Neuron
Found peripherally in sensory ganglia (Dorsal Root Ganglion). Give rise to fibers that carry general sensation to the CNS.
-Pain, temperature, etc.
Unipolar Neurons
Give rise to fibers that carry special sensation to the CNS.
-Vision, olfaction (smell), hearing, equilibrium/balance, and taste
Bipolar Neurons
Provide special sensation (vision) via layer of rods and cones (Photoreceptors) which picks up light to allow you to see. These then project into an Internuncial Cell Layer (Short axonal cells found between two major systems). These then parlay that on up to the Ganglion Cells, which forms CN 2 (Optic Nerve). Cells cluster together to make an Optic Nerve ending that is taken back to the CNS.
Retinal Bipolar Neuron
Give rise to motor fibers and most internuncial cells.
Multipolar Neurons
At rest and healthy, should be -70
Set up by concentration gradients of electrolytes in the ICF and ECF
Primary electrolytes: K, Na, Ca, Cl
Regulated by actions of Na/K ATPase (requires energy)
Resting Membrane Potential
Bones, Connective tissue, etc.
-Resting Membrane Potential never changes (as long as you’re healthy)
Non-Excitable Tissue
Muscles, Nerves, etc.
-Resting Membrane Potential can be disrupted in order to create an Action Potential.
Excitable Tissue
Start out in resting state (positive charge on outside and negative charge on inside). Then have a reversal of polarity with inside becoming positive and outside becoming negative (depolarization). Causes an action potential that travels down the axon. Have repolarization occurring behind the impulse traveling down the axon that resets membrane potentials.
-If it didn’t work, we wouldn’t be able to make our nerves or muscles function. Dependent on electrical currents
Impulse Conduction
Average is about 100 Angstrom Units, but it’s enough distance to inhibit transmission of an impulse over to the Postsynaptic Neuron without a neurotransmitter.
Synapse
Secreted by the presynaptic membrane into synaptic cleft, this then goes and transfers the stimulus to postsynaptic neuron and the impulse continues down axon until it reaches effector organs.
Neurotransmitter
Neurotransmitter for cholinergic receptors (Excitatory)
Acetylcholine
Neurotransmitter for adrenergic receptors (Excitatory)
Norepinephrine
Neurotransmitters can be Excitatory and cause an Excitatory Postsynaptic Potential (EPSP) on the postsynaptic neuron (depolarization), or be Inhibitory and cause an Inhibitory Postsynaptic Potential (IPSP) on the postsynaptic neuron (Hyperpolarization).
Neurotransmitters
A postsynaptic neuron is influenced by multiple presynaptic neurons. Need joint EPSPs from both presynaptic neurons to get a stimulus on the postsynaptic neuron.
-Need several signals operating in concert with each other.
Convergence
A signal presynaptic neuron can exert control over multiple postsynaptic neurons.
Divergence
Occurs when terminal buttons of presynaptic neurons are synapsing directly on the dendrites.
-Generally what you expect to see with presynaptic/post synaptic.
Axonodendritic Synapses
Occurs when terminal buttons of presynaptic neurons are synapsing to the cell body.
Axonosomatic Synapses
Occurs when terminal buttons of presynaptic neurons are synapsing directly to the Axon.
Axonoaxonic Synapses
Open ares between the myelin that leave a tiny bit of axon exposed. Impulse jumps from one of these to the next, conserving energy. Also increases the velocity of the segment. Moves very rapidly down a myelinated axon.
-Only depolarizes a segment at a time, not the whole thing.
Nodes of Ranvier
Neurologic Peripheral cells that create axons for peripheral nerves.
-Creates Myelin on these axons
-Provides insulation (myelin) to neurons in the PNS
Schwann Cells
The “skipping” depolarization that occurs along the Nodes of Ranvier
Saltatory Conduction
Cells that stabilize the nervous system and cause it to stick together.
4 Types:
-Astrocytes, Oligodendrocytes, Microglia, and Ependymal Cells
Neuroglial Cells
-Clean up debris: any injury to the brain or something where the brain does not function, needs to be cleared out
-Digest parts of dead neurons
-Transport nutrients to neurons
-hold neurons in place (glue)
-Fill in extracellular space: spaces can be created as a result of injury/disease. These fill in those extra spaces
-Help form the blood/brain barrier.
Astrocytes (Astroglia)
Found in the White Matter (myelinated axons); forms the blood-brain barrier via perivascular feet. Perivascular feet form tight junctions with the capillaries to form a barrier between the CNS and CV system.
Fibrous Astrocyte
Found in the gray matter; forms the blood-brain barrier
Protoplasmic Astrocyte
Provides myelin to neuronal axons in the Central Nervous System.
-Cell membrane wraps around axon to form myelin sheath
-Very efficient - can do multiple axons
-Have Nodes of Ranvier present
Oligodendrocytes
Cells that go out into the CNS to gobble up trash, scar tissue, diseased tissue, etc. to promote healing.
Microglial Cells
Line the cavities (ventricles) in the CNS
Ependymal Cells
