Introduction to Nervous System Flashcards
3 Divisions of the Nervous System
1.) Central Nervous System - (Brain + Spine)
2.) Peripheral Nervous System - (Spinal Nerves (31 pairs)
Cranial Nerves (12 pairs)
3.) Autonomic Nervous System - everything that isn’t related to somatic system is innervated by ANS. Includes vasculature, GI tract, thoracic viscera, glands, pili erector muscle in hair follicles.
Response (Motor)
Somatic Nervous System or Autonomic Nervous System
Somatic Nervous System
- “voluntary,” Innervates Skeletal Muscle.
- Pathway: One motor neuron to target
Autonomic Nervous System
- “involuntary”
- Innervates cardiac muscle, smooth muscle, and glands
- Pathway: Chain of two motor neurons to target. Preganglionic and postganglionic neurons. Innervates cardiac muscle, smooth muscle, and glands.
Divided into sympathetic (fight/flight) and parasympathetic division
Nervous System composed of
Neurons or nerve cells which are excitable cells that transmit nerve impulses. Also have glial cells which are supporting cells. They are non excitable. More glial cells than neurons in a 10:1 ratio.
Neuron Anatomy
EACH neuron HAS CELL BODY (SOMA). EACH SOMA HAS SINGLE AXON which projects out. Once It reaches innervation site it utilizes a terminal segment as a stimulus initiator. Cell body has dendrites which extend from receptor segment. Can have several dendrites per soma. Some axons are myelinated and that is where we have lots of glial cells. Important for neurons that require high speed.
Nervous Tissue
In the PNS, neuron cell bodies and dendrites are found in the ganglia.
In the PNS, neuron axons are found in nerves.
Sensory neurons send info to CNS.
Motor neurons send info away from CNS.
Spinal Cord Cross Section Anatomy - Grey Matter and White Matter
1.) Gray Matter which consists of Anterior horn and Posterior Horn. Gray matter is where our cell bodies are located. The ventral horn (front) is where motor neurons have their cell bodies. The dorsal horn (back) is where the sensory neurons have their cell bodies.
2.) White Matter is external to the gray matter. It is where our axons are located. All of the white matter is reserved for the tracts of the spinal cord.
Ascending tracts = sensory
Descending tracts = Motor
First thing that we see coming off spinal cord
is rootlets to make roots. Our ventral rootlets give rise to our ventral root. Our dorsal rootlets give rise to our dorsal root. Dorsal Root ganglion is not a type of synapse, but does contain cell bodies. It is merely a relay station between peripheral and spinal cord. The neurons that are in dorsal root and dorsal ganglion are psuedounipolar neurons. Our dorsal and ventral roots come together to form spinal roots.
intervertebral foramen
allows spinal nerves to exit into Periphary
Once becomes spinal nerves it
divides into ventral and dorsal ramii. The dorsal ramii will go to structures that are dorsally located (the back). The ventral ramii will innervate the reamining structures associated with somatic nervous system. It will have connections with a structure associated with sympathetic nervous system called sympathetic chain. Sympathetic chain has sympathetic ganglia (31 pairs). Each ventral ramii will have two connections to symp. ganglia called ramii comunicans.
From sympathetic ganglia,
we can utilize ventral ramii as a pathway to send sympathetic fibers to periphary (anything away from spinal cord). ONly exception is viscera.
We innervate viscera with splanchnic nerves which comes off medial side of sympathetic ganglia and this is how we innervate GI tract, uterus, testis, stomach, and liver.
