peripheral nervous system Flashcards
(56 cards)
parts of the pns
somatic and autonomic
two parts of autonomic
sympathetic and parasympathetic
somatic
voluntary control (efferent neurones and skeletal muscle)–> also mediates involuntary reflexes
autonomic
unconscious- visceral (inside body organs) e.g. HR, digestion etc
main NT and receptors in PNS
ACH
2 types of receptors however only nicotinic in PNS
also adrenergic receptors found in autonomic system
myelin sheath
made up of schwann cells in the PNS (type of glial cell)
-insulates neurones and causes saltatory conduction where impulses jump from nodes of ranvier to nodes of ranvier. increases conductance velocity
what are SNARE mediated neurotransmitters?
small abundant , tailed anchored proteins which r often post transitionary inserted into membranes via a c-terminal transmembrane demain
role of SNARE proteins
mediate vesical fusion
SNARE mechanism
Ca2+ dependent exocytosis
As AP reaches synapse, depolarisations cases Ca2+ channels to open and Ca2+ to flood in.
Calcium causes various varieties of SNARE proteins to ‘pull’ the vesicles to the membrane surface where they can release their content
how is an AP transmitted across a synapse
- AP reaches presynaptic knob
- this causes Ca2+ channels to open,, due to Na+ channels being open
- Calcium causes th vesicles to move to the membrane via calcium dependent exocytosis (SNARE proteins)
- once fused, NT is released and crosses the synaptic cleft
- NT will enter complementary inotropic channels and cause them to open
- Na+ will enter the post synaptic neurone and cause depolarisation
diff between norma synapse and bw regular neuromuscular junction
NMJ- interaction between neurone and muscle q
role of summation
-prevents fatigue
the process which determines whether or not an AP will be triggered by the combined effects of excitatory and inhibitory signals
two types
two types of summation
temporal
spatial
spatial
a way of achieving the threshold potential via input from multiple presynaptic neurones.
temporal
a high frequency of APs in the presynaptic neurone elicits postsynaptic potentials that overlap and summate with each other. The higher the frequency the higher the chance that the threshold will be reached.
how is ACH made
acetyl cholinetransferase from acetyl co A and choline in the liver
how is ACH broken down
by acetyl cholinesterase - to choline and ethnic acid
where is ACH stored
stores in vesicles in neurones (highest conc is in the terminal ends)
what are thermoTRP channels
6 transmembrane channel found on the c.s.m which is involved in temp perception–> ion channels. Activated and opened by heat. Diff type of TRP channel for different types of temp e.g. dangerous temp
4 diff receptors
chemo
there
mechano
photo
nocieptive
a sensory nerve cell that responds to damaging or dangerous stimuli by sending signals to the brain and spinal cord–> nociception. They are found in any area of the body which can ease noxious stimuli.
Nociceptive neurones travel down spinal cord where they form synapses at the dorsal horn–> reflex mechanism
afferent
conduction signals towards cns
efferent
conducting signals away from cns
role of glial cells
1) maintain homeostasis
2) forms myelin
3) provide support and protection
