PNS (4d) Flashcards
what is the PNS made of
ganglia and nerves that branch from the CNS
types of nerves
cranial: take impulses to and from the brain (12 pairs)
spinal: take impulses to and from the spinal cord and brain
what is the corpus callosum
tract within the brain that connects both sides of the brain
the PNS brings information to and from these brain tracts
characteristics of cranial nerves and which do we need to know
most are mixed (motor and sensory nerves)
1. olfactory
2. optic
8. vestibulocochlear (hearing and balance)
10. vagus (internal organs)
1, 2 and 8 are solely sensory
characteristics of the vagus nerve
only pair of cranial nerves that goes beyond the neck and head region
most motor fibers and parasympathetic and signal to the heart, lungs and abdominal viscera
sensory fibers carry impulses from thoracic and abdominal viscera, baroreceptors, chemoreceptors and taste buds of posterior tongue and pharynx
characteristics of the spinal cord
extends from foramen magnum to 1-2 lumbar vertebra
has 31 pairs of mixed spinal nerves (named based on where they emerge from: cervical, thoracic, lumbar and cauda equina)
characteristics of gray matter in the spinal cord
dorsal horns contain the cell bodies of interneurons and receive information from sensory neurons in the dorsal root
dorsal root ganglion contains the cell bodies of sensory neurons
ventral horns contain the cell bodies of motor neurons of the somatic nervous system (send information out by ventral root)
central canal is filled with CSF
characteristics of white matter in the spinal cord
sensory tracts send impulses towards the brain
motor tracts carry impulses from the brain to skeletal muscles
what makes up the spinal nerves
the ventral and dorsal root that emerge from the spinal cord merge to from spinal nerves
characteristics of spinal nerve
nerve separates into the dorsal and ventral ramus
ramus: branch of spinal nerve which contains both motor and sensory fibers
what types of rami do what
dorsal rami: skin and muscles of posterior trunk
T1-T12 ventral rami: form intercostal nerves that supply muscles and skin or ribs and trunk
ventral rami without T1-T12: form plexus of sensory and motor nerves for limbs
what is a plexus
when branches of ventral rami from a single nerve join with axons from adjacent nerves (doesnt occur with T1-T12)
creates new combination as the peripheral nerves
what are the four types of voluntary plexuses and what they contain
cervical plexus: posterior head, neck, shoulders and diaphragm
brachial plexus: upper limbs, some neck, shoulder muscles
lumbar plexus: abdominal wall, external genitals and part of lower limbs
sacral plexus: buttocks, perineum and lower limbs
how does the somatic division differ from the autonomic division
effectors
efferent pathways
organ responses to neurotransmitters
difference in somatic vs autonomic divisions based on motor neurons
somatic: cell bodies originate inside the CNS, axon extends to skeletal muscles
autonomic: chain of two motor neurons (preganglionic neuron in CNS, postganglionic neuron extends to the organ)
difference in somatic vs autonomic divisions based on neurotransmitters
somatic: cholinergic nerve fibers release acetylcholine and it has a stimulatory effect of skeletal muscles
autonomic: cholinergic nerve fibers release acetylcholine and it has an inhibitory effect on cardiac muscle, adrenergic nerve fibers release norepinephrine, epinephrine and dopamine and they create the fight or flight response
what are the subdivisions of the autonomic division and characteristics
sympathetic: fight or flight response, E (exercise, excitement, emergency, embarrassment)
parasympathetic: rest and digest response, D (digest, defecate and diuresis)
what only receives input from the sympathetic nervous system
adrenal medulla, some glands, skin and most blood vessels
what does the sympathetic nervous system do in the skin and adrenal gland
skin: increased sweating and goose bumps
adrenal glands: stimulates adrenal medulla to produce norepinephrine and epinephrine
how is the sympathetic division anatomically arranged
preganglionic motor neurons originate from T1 to L2 (axons pass through a ramus communicans to enter a sympathetic trunk ganglion which lies near the spinal cord)
there are 22 pairs of sympathetic trunk ganglia
how does the sympathetic division work
the preganglionic neuron synapses at the ganglion and may synapse with a postganglionic neuron at the same or different level
or the preganglionic neuron can pass through the ganglion without synapsing and form part of the splanchnic nerve
what is a splanchnic nerve
nerve that travels through the collateral ganglion (serve the abdominal and pelvic organs)
difference between short preganglionic neurons and long postganglionic neurons in sympathetic system
preganglionic: have cholinergic fibers
postganglionic: have adrenergic fibers
how is the parasympathetic division anatomically arranged
preganglionic neurons originate in cranial nerves 3, 6, 9 and 10 and S2-S4 region of the spinal cord
preganglionic neurons (long) synapse with terminal ganglia (located on or near effector organ) and from there postganglionic axons (short) extend to organs
what types of fibers do pre and postganglionic neurons have in the parasympathetic division
both have cholinergic fibers
what happens when the same organ is served by both divisions of the autonomic nervous system
cause antagonistic effects due to different neurotransmitters
