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
