peripheral nervous system Flashcards
do PNS neurones transmit signals better than CNS or worse
Neurones of the PNS transmit signals better than the CNS and receptors and
effectors in all other parts of the body
what fibres can peripheral nerves contain
can contain nerve fibres that are the axons of
- efferent neurones (motor)
- afferent neurones (sensory)
- both
so fibres in a nerve can be classified as belonging to the efferent or afferent branch of the PNS
what do efferent neurones refer to
motor
what do afferent neurones refer to
sensory
which fibres do all of the spinal nerves contain
all of the spinal nerves contain both the efferent and afferent branches
which fibres do cranial nerves contain
some cranial nerves contain only afferent fibres (optic nerve) or only efferent fibres (hypoglossal nerve)
function of afferent neurones
convey information from sensory receptors at their peripheral ending to the CNS
where is axon of afferent neurones
lhe long part of their axon lies OUTSIDE of the CNS and is part of the PNS
why are afferent neurones sometimes called first order neurones
because they are the first cells
entering the CNS in the synaptically linked chains of neurones that handle
incoming information
function of efferent neurones
carry signals out from the CNS to muscles, glands and other tissues
what is the efferent dividion of the PNS made of
somatic nervous system (voluntary)
and
the autonomic nervous system
what does somatic nervous system innervate
skeletal muscle
what does somatic nervous system consist of
a single neurone between the CNS and skeletal muscle cells
can somatic nervous system lead to muscle inhibition
no
it can only lead to muscle excitation
is somatic nervous system voluntary or involuntary
voluntary - conscious of its actions
where are cell bodies of somatic cell neurones
located in groups in the brainstem or the ventral horn of the spinal cord
describe axons of somatic nervous system neruones
have large-diameter myelinated axons which leave the CNS and pass without ANY SYNAPSE directly to the skeletal muscle cells
why are somatic neurones called motor neurones
because their activity results in contraction of the innervated skeletal muscles cells
what is the only neurotransmitter involved in somatic nervous system
acetylcholine
ACh
function of autonomic nervous system
Innervate smooth & cardiac muscle, glands, neurones in the GI tract
(enteric nervous system) and other tissues
how many neurones in autonomic nervous system
Has a two-neurone chain (connected by
synapse) between the CNS and the
effector organ
where is the first autonomic neurone
The first neurone has its cell body IN the CNS
The synapse between the neurones is outside the CNS in a cell cluster
called an autonomic ganglion
what are preganglionic neurones
the neurones passing between the CNS and the ganglia
what are postganglionic neurones
the neurones passing between the ganglia and the effector cells
