PNS and Synapses Flashcards
synapse
connection between neuron and target cell
pre–>post synaptic component
electrical synapse vs chemical synapse
electrical: passing of electrical signals (gap junctions in cardiac)
chemical: the rest of our body; uses neurotransmitters
structures involved in typical chemical synapse
axon terminal (presynaptic)
synaptic cleft (gap between neurons)
neurotransmitter receptors
events of synaptic transmission in chronological order
- action potential reaches axon terminal
- opens voltage gated calcium channels
- presynaptic vesicles perform exocytosis
- neurotransmitter cross cleft and binds to post synaptic receptors
- ligand gated channels open (graded potential)
- termination through degradation
what is excitatory postsynaptic potential (EPSP)
graded potentials thats purpose is to generate action potential (cholinergic and adrenergic)
–> depolarization
what in inhibitory post synaptic potential (IPSP)
graded potentials thats purpose is to avoid action potentials (GABA-ergic)
–>hyperpolarization
how can a single neurotransmitter elicit different responses at different postsynaptic cells
by binding to different receptors at different synapses
most common excitatory and inhibitory neurotransmitters
excitatory: glutamate, epinephrine
inhibitory: GABA, serotonin
reuptake mechanism
the whole neurotransmitter molecule is taken back into the axon terminal that released it
enzymatic breakdown
enzyme binds to neurotransmitter and breaks it apart so that the neurotransmitter can no longer fit into a receptor of receiving cell
diffusion mechanism
the neurotransmitter drifts away and can no longer act on receptor
formation structure and branches of spinal nerve
dorsal ramus, spinal nerve, dorsal root ganglion, dorsal root, ventral root, gray ramus, white ramus, and ventral ramus
number of spinal nerve pairs emerging from each spinal cord
8 C
12 T
5 L
5 S
1 C
spinal nerve plexus
group of nerves that merge from different spinal nerves to connect to certain parts of body
cervical nerve plexus
C1-C4 head and neck
nerves: C1-C4
brachial nerve plexus
C5-T1 upper extremities
nerves: musculocutaneous, median, ulnar (pinky) , axillary, and radial (thumb)
lumbar nerve plexus
L1-L4 (abdomen, thighs, and genitalia)
nerves: fermoral (quads) and obturator (medial side of leg)
sacral nerve plexus
L4-S5 (pelvis and below knee)
nerves: sciatic, tibial (back of leg), deep fibular (front of leg), superficial fibular (lateral of leg)
reflex
quick involuntary stereotyped reactions of glands or muscles to stimuli (any muscle types)
–> generated at spinal level
describe reflex responses in terms of the major structural and functional components of a reflex arc
- receptor detects stimulus
- it sends afferent signal to posterior horn
- reaches integrating center where there is synaptic contact
- efferent signal from anterior horn
- carriers motor impulse to muscles or effectors
describe functions and locations of first, second, third, order neurons
first order: sensory neurons that produce action potentials ; enter through dorsal root and synapse with second
second order (interneuron): dorsal gray horn of spinal cord and decussates to ascend spinal cord
third order: integrated in primary somatosensory cortex
locations of lower and upper neurons
these are motor neurons
upper motor: in primary motor cortex and propagates its AP to lower motor neurons
lower motor: in brain stem where signal exits via ventral root and enters spinal nerve
decussation and its implication
occurs in the medulla and allows for coordinated control of movement and sensation between both sides of the brain
