pns Flashcards
Peripheral nerves
bundles of axons.
Types:
- Sensory (afferent)
- Motor (efferent)
- Autonomic (also motor, involuntary)
Composed of:
1. Afferent neuron, receptor in PNS to CNS
2. Interneuron, w/i CNS
3. Efferent neuron, from CNS to PNS, connects to effector organ
Motor neurons
- Striated muscle
- Cell body in CNS
- release ACh
Sensory neurons
- Cell body not in CNS - sensory ganglia
Ganglion
Collection of neuronal cell bodies in PNS
Autonomic neurons
- Either sympathetic (norepinephrine) or parasympathetic (ACh)
- 2 neurons in CNS -> peripheral organ
- Preganglionic: cell body in CNS
- Postganglionic: cell body in autonomic ganglion (PNS)
- Sympathetic: ganglion near CNS
- Parasympathetic: ganglion near or in target organ
ANS functions
- Homeostasis (maintain stable env, ex. breathing harder when running)
- Vegetative systems (semi-autonomous, coordinated w endocrine system)
- BP
- GI motility
- electrolyte water balance
- Pupil reflexes
- Sexual function
Higher centres of ANS
- Some reflexes at spinal cord level
- Medulla, hypothalamus, prefrontal cortex (emotional states, not 100% autonomic)
ANS afferent neurons
- Send info into control centres
- Baroreceptors: pressure (blood vessels)
- Osmoreceptors: concentration (ions in plasma)
- Thermosensors
- Cutaneous receptors: sexual stimulus
- Pain fibers
- Stretch receptors: distension in lungs, bladder, stomach, bowel
Sympathetic nervous system
Catabolic effects (breaking down, using energy)
- Incr HR, BP
- Incr blood flow to skeletal muscle
- Decr blood flow to skin
- Fight-or-flight: epinephrine and norepinephrine released from medulla, stimulates skeletal muscle glycogenolysis (glycogen->glucose->ATP)
Parasympathetic nervous system
Anabolic effects (building)
- Decr HR, BP
- Incr GI tract motility and secretions
- Relaxation of sphincters
Paradoxical coactivation:
both symp and parasymp activated during intense conflict
Cranial nerves
Carry afferent info, efferent info, ANS fibers
Name mnemonic: Ooh, Ooh, Ooh, To Touch And Feel Very Good Vagina. So Heavenly!
olfactory
optic
oculomotor
trochlear
trigeminal
abducens
facial
vestibulocochlear (auditory)
glossopharyngeal
vagus
spinal accessory
hypoglossal
Function mnemonic: Some Say Marry Money, But My Brother Says Big Brains Matter More.
S=sensory
M=motor
B=both
Which nerves are completely in the CNS?
i olfactory and ii optic
olfactory
sensory - smell
optic
sensory - vision
oculomotor
motor, voluntary - eyeball movement to midline
motor, autonomic - constricts pupil, thickens lens
trochlear
motor, voluntary - moves eyeball
trigeminal
motor - mastication (chewing)
sensory - touch/temp/pain from head
abducens
motor - eyeball movement away from midline
When looking right or left, vi and iii coordinate through medial longitudinal fasciculus
facial
motor, voluntary - facial expression
motor, autonomic - lacrimal and salivary glands, taste buds
glossopharyngeal
both
vagus
both
ix, x, xi all involved in swallowing (vagus x most important)
spinal accessory
motor - swallowing and shrugging
hypoglossal
motor - tongue
Spinal nerves
- 31 pairs, numbered by vertebrae
- All have voluntary motor function
- All (except C.1, first cervical) have sensory fibers
Sympathetic nerves
Preganglions arise from all thoracic, and 1st and 2nd lumbar segments
parasympathetic nerves
preganglions arise from sacral segments 2,3,4
carried in cranial nerves iii, vii, ix, x, and sacral 2, 3, 4
