Peripheral Nervous System Flashcards
Do spinal nerves have afferent and efferent branches
yes - they all do
do all cranial nerves have afferent and efferent branches
No - most do
optic is only afferent
hypoglossal is only efferent
describe afferent neurons
convey info from sensory receptors to CNS
long part of axon is outside CNS, central process is inside CNS
1st order neurons
describe efferent neurons
carry signals from CNS to effectors
subdivided into somatic and autonomic
describe somatic nervous system
innervate skeletal muscle
voluntary control
single neuron - no synapse between CNS and skeletal muscle cells
only cause excitation - only cause contraction so called MOTOR NEURONS
large diameter myelinated axons
ACh is only neurotransmitter involved
describe autonomic nervous system
innervates smooth/ cardiac muscle - involuntary
2 neuron chain - connected by synapse
can be excitatory or inhibitory
before ganglion = ACh
after ganglion = ACh(excitatory) or NA (inhibitory)
divided into parasympathetic and sympathetic
describe sympathetic nervous system
leaves CNS T1-l2
forms sympathetic chains
preganglionic synapses - ACh, nicotinic receptors
postganglionic synpase - NA, adrenergic receptors
preganglionic fibres form lateral grey horn
supply visceral organs, structures of superficial body regions
effects amplified by adrenal gland
how does the adrenal gland amplify sympathetic action
releases adrenaline directly into blood
what are the effects of sympathetic stimulation
increase HR/ force of contraction vasoconstriction bronchodilation reduced gastric motility/ secretions sphincter contraction male ejaculation
describe parasympathetic nervous system
leaves CNS from brainstem or sacral portions of spinal cord
ganglia lie in/ very close to organs that postganglionic neurones innervates
preganglionic neurons; ACh, nicotinic receptors
effect cell synapse; ACh, muscarinic receptor
describe cranial outflow of parasympathetic nervous system
from brain preganglionic fibres run via 1973 CN 3 to pupil CN 7 to salivary gland CN 9 to swallowing reflex CN 10 to thorax and abdomen
describe sacral outflow of parasympathetic nervous system
supplies remaining abdominal or pelvic organs
what are the effects of the parasympathetic nervous system
decrease HR/ force of contraction vasodilation bronchoconstriction increase gastric motility/ secretions sphincter relaxation male erection
what is the enteric nervous system
nervous system of GI tract
can work independently of autonomic nervous system
