Unit 4 Study Guide Flashcards
Epineurium
- thick layer of dense connective tissue
- encloses the entire nerve
perineurium
- layer of dense irregular connective tissue
- wraps bundles of axons, fascicles
- supports blood vessels
Endoneurium
- delicate layer of areolar connective tissue
- separates and electrically insulates each axon
- has capillaries that supply the axon
dorsal root
- many axons of sensory neurons whose cell bodies are in posterior root ganglion
anterior root
- many axons of motor neurons whose cell bodies are in anterior and lateral horns
posterior ramus
- smaller of the two branches
- innervates deep muscles of the back and skin of back
anterior ramus
- larger of the two branches
- splits into multiple other branches
- at different levels, this ramus innervates anterior and lateral trunk, upper limb, lower limb
- participates in plexuses
Posterior Horns
Axons of sensory neurons and cell bodies of interneurons
Lateral Horns
(T1-L2)
-cell bodes of autonomic motor neurons that innervate cardiac muscle, smooth muscle, glands
Anterior Horns
cell bodies of somatic motor neurons innervating skeletal muscle
Rami Communicantes
- Associated with spinal Nerves. Connect spinal nerves to sympathetic trunk
- contain axons associated with the autonomic nervous system
White Rami Communicantes
- carry myelinated preganglionic sympathetic axons from T1-L2 nerves to turn
- Entrance ramps to trunk
Gray Rami Communicantes
- Carry unmyelinated postganglionic sympathetic axons from trunk to all spinal nerves
- exit ramps from trunk
Sympathetic Trunk Ganglion
-Ganglia interconnected in sympathetic trunk parallel to vertebral column
Somatic Nervous System
- includes process that are perceived or consciously perceived
- Somatic Sensory
- Somatic Motor
- A single lower neuron extends from the CNS to skeletal muscle fibers.
- Cell body lies within brainstem or the spinal cord and axon exits the CNS in a cranial nerve or a spinal nerve and extends to a skeletal muscle
Somatic Sensory
detection of stimuli and transmission of nerve signal from special senses, skin, and proprioreceptors to the CNS
Somatic Motor
initiation and transmission of nerve signals from the CNS to control skeletal muscles
Autonomic Nervous System
- includes processes regulated below the conscious level. -
- Motor System only–Autonomic Motor
- Responds to input from visceral sensory components, such as receptors that detect stimuli associated with blood vessels and internal organs
Lower Motor Neuron found in the Somatic Nervous System
- A single lower motor neuron extends from the CNS to skeletal muscle fibers.
- Cell body lies within brainstem or the spinal cord and axon exits the CNS in a cranial nerve or a spinal nerve and extends to a skeletal muscle
- Voluntary Movements involve cerebrum
- Reflexive movements involve brain and spinal cord
Preganglionic neuron of autonomic system
- cell body lies within brainstem or spinal cord
- Preganglionic axon extends from cell body and exits CNS in either a cranial nerve or a spinal nerve
- Myelinated axons with small diameter
- nerve signals release acetylcholine to excite second neuron
Postganglionic neuron of autonomic system
- cell body resides within an autonomic ganglion
- postganglionic axon extends from the cell body to an effector
- unmyelinated axons with even smaller diameter
- Nerve signal releases acetylcholine or norepinephrine to excite or inhibit second neuron
Two lower neuron system of Autonomic System
Post ganglionic and preganglionic
-extend from the CNS
Parasympathetic division of ANS
- functions to maintain homeostasis when we are at rest
- craniosacral
- preganglionic neurons are located in brainstem and segments of spinal cord
- Rest-and-digest
- Longer preganglionic axons and shorter postganglionic axons
- Few branches
- Ganglia located close to or within effector
Sympathetic Division of ANS
- functions to maintain homeostasis during exercise or times of stress
- Thoracolumbar
- Preganglionic neurons located on lateral horns
- Fight-or-flight response
- shorter preganglionic axons and longer postganglionic axons
- many branches
- ganglia located in the sympathetic trunk or prevertebral ganglia
Structure of the sympathetic trunk
- immediately lateral to the vertebral column and anterior to the pair spinal nerves
- one sympathetic trunk ganglion is associated with each spinal nerve
Function of the sympathetic trunk
Allows nerve fibers to travel to spinal nerves that are superior and inferior from where they originated
What is the importance of the parasympathetic division to the craniosacral?
Brainstem:
- innervation to the head
- Innervation to the thoracic organs (cardiac and pulmonary)
- innervation to most abdominal organs (esophageal, aortic)
Sacral:
- Pelvic spanchic nerves form hypogastric plexus
- Innervation to pelvic region (bladder, rectum, vagina, penis)
What is the importance of the sympathetic division to the thoracolumbar region?
Thoracolumbar
- innervation to thoracic organs (cardiac and pulmonary plexus)
- innervation to abdominal pelvic organs (Celiac ganglion, Superior and inferior mesenteric ganglio, hypogastric ganglion)
Cholinergic Neurons
synthesize/release acetylcholine
Adrenergic neurons
syntheisize/release norepinephrine
Preganglionic neurons release?
acetylcholine
Ganglionic neuron, cell body, and dendrites contain?
nicotine receptors for ACh
Postganglionic Axon for parasympathetic releases what?
ACh
Postganglionic Axon for sympathetic releases what?
NE
What types of receptors do target cells contain?
Muscarinic receptors (bind to ACh) or adrenergic receptors (binds NE)
Where do sympathetic pregangliionic neurons originate?
in the lateral gray horns of the T1-L2 regions of the spinal cord
Where do axons of the preganglionic neurons travel and with what?
with somatic neurons and exit into anterior rami
Spinal Nerve Pathway
- for skin effectors of neck, torso, and limbs
- Preganglionic neuron enters synaptic trunk ganglion and synapses with ganglionic neuron
- Postganglionic Axon travels through gray rams at the same spinal level as ganglion, joins that level’s spinal nerve and extends to effector organ
Postganglionic Sympathetic nerve pathway
for effectors that are internal organs of thorax and neck:
- skin effectors of the head and neck
- eyelid and dilator pulpillae muscles
Pregangliionic neuron enters and synapses in sympathetic trunk ganglion
Postganglionic axon goes directly from trunk ganglion to effector organ (DOES NOT LEAVE TRUNK VIA GRAY RAMUS)
Splanchic Nerve Pathway
- For effectors in abdominal and pelvic viscera
- preganglionic axons pass sympathetic trunk without synapsing. (Axons travel in splanchic nerves to prevertebral ganglia where they make synapses)
- Postganglionic axons innervate effectors
Adrenal Medulla Pathway
- for central region of adrenal gland (its medulla)
- preganglionic sympathetic axons extend through sympathetic trunk and prevertebral ganglia without synapsing in either
-Preganglionic cells synapse on neurosecretory cells and stimulate adrenal medulla cells to release epinephrine and norepinephrine into the blood (potentiate and prolong fight-or-flight response)
Autonomic Tone
continuously release neurotransmitter to regulate target organ (parasympathetic and sympathetic) to sustain stimulation or inhibition
-Generate base level responses that can be adjusted
Do blood blood vessel constrict or dilate when increased sympathetic activity?
Constrict
Do blood vessels constrict or dilate when decreased sympathetic activity?
Dilate
Dual Innervation
Most effector receive input from both sympathetic and parasympathetic divisions
Antagonistic effects of Dual innervation
- Parasympathetic activity slows heart rate; sympathetic activity increases heart rate
- cardiac cell have both cholinergic and adrenergic receptors
Cooperative effects of Dual innervation
- Seen when parasympathetic and sympathetic stimulate have different effects that are part of an overall response
- erection due to parasympathetic activity. Ejaculation due to sympathetic activity
Autonomic Plexuses
- how both division of the autonomic nervous system innervates organs
- located in anterior body cavities
- Contains parasympathetic preganglionic and sympathetic postganglionic axons (two divisions don’t interact or synapse, but have same target organ)
-Cardiac Plexus, pulmonary plexus, esophageal plexus, abdominal aortic plexus, hypograstric plexus
