Module 3- Neurophysiology Flashcards
Central Nervous System
acts as the integrating system
-brain and spinal cord
Peripheral Nervous System
-rapid communication
(1) Sensory division of the PNS; sends info to the CNS through afferent (sensory) neurons
(2) Efferent division of PNS; takes info from the CNS to target cells via efferent neurons
Efferent neurons
(1) autonomic neurons; sympathetic and parasympathetic
(2) somatic motor neurons
autonomic neurons
- unconscious, homeostatic response
sympathetic and parasympathetic - controls: cardiac muscle, smooth muscle, exocrine glands/cells, some adipose tissue
somatic motor neurons
-conscious movement
controls skeletal muscle
interneurons
neurons entirely within the CNS
ganglia
clusters of neuron cell bodies in the peripheral nervous system
nerves
bundles of axons in the peripheral nervous system
-transmits signals between brain or spinal cord and other body regions
Autonomic (involuntary) nervous system
-conveys impulses from CNS to smooth muscle, cardiac muscle, and glands
- 1st preganglionic fiber has cell body in the CNS and synapses with 2nd in the autonomic ganglion
-2nd postganglionic fiber sends signal from autonomic ganglion to the effector organ
spinal cord
-links brain and PNS
-controls some involuntary functions
-protected by vertebral column
- 31 pairs of spinal nerves
sympathetic
-fight or flight
-excitement, emergency, exercise, embarrassment
-routes energy resources to brain, heart, and skeletal muscles
sympathetic effects
-adrenergic effects
-dilates pupils
-increases heart beat and force of contraction
- relaxes airways
-inhibition of digestion and stomach activity
-stimulates release of glucose into the blood; inhibits insulin release from pancreas
-stimulates secretion of epinephrine and norepinephrine from adrenal
parasympathetic
-rest and digest
-digestion, defecation, and dieresis
-reduces energy use and directs “housekeeping” activities
parasympathetic effects
- cholinergic
constricts pupils - slows heartbeat
-constricts airways
-stimulates digestion and stomach activity
-increases glucose utilization by liver cells; stimulates insulin secretion from pancreas
sympathetic fibers
the sympathetic nervous system has short cholingeric (acetlycholine-releasing) preganglionic fibers and long adrenergic (norepinephrine-releasing) postganglionic fibers
parasympathetic fibers
parasympathetic nervous system has long cholinergic preganglionic fibers and short cholinergic postganglionic fibers
long distance communication
the nervous system achieves long distance communication by combining long distances electrical signals within (along) cells and short distance chemical signals between cells (synapses)
neuron structure
cell body: organelles
dendrites; receive signals
axon; transmits signals
axon hillock; initiates signals to travel down axon
membrane potential
unequal distribution of positivities and negative charges across the membrane
-in neurons, is primarily driven by the distribution of sodium and potassium ions
resting membrane
the membrane potential of cell (neuron) not transmitting signals; roughly -70 mV, polarized, negative
leaky channel
always open, no gate and not regulated
ligand (chemically) gated
open in response to a specific chemical (such as a neurotransmitter)
mechanical gated
open in response to physical deformation of the receptor
voltage gated
only open in response to specific electrical signals
depolarization
- closer to 0mV
-decrease in potential; membrane less negative
repolarization
return to resting potential after depolarization
hyper polarization
-further from 0mV
increase in potential; membrane more negative
graded potentials overview
-occur in dendrites and cell body
-small, localized change in membrane potential
graded potential
-the magnitude of change in membrane potential varies with strength of stimulus (greater stimulus = more gated channels open)
-caused by opening of voltage or ligand gates ion channels
-local signal initiated in dendrites, decays with distance
graded potential effects
can cause depolarization or hyperpolarization
-depolarization; increase in membrane potential, more Na+ diffuses into the cell
- hyperpolarization; decrease in membrane potential, more K+ diffuses out of cell
action potentials
-brief, rapid reversal of membrane potential
-begins at the axon hillock, travels down axon (conduction)
-all to none threshold
-initiated by graded potentials
action potential phases summary
- resting potential (Na+/K+ pump)
- depolarization (Voltage gated Na+ channel)
- depolarization (Voltage gates K+ channel)
- Resting potential (Na+/K+ pump)
electrical synapses
- electrical current flows from one cell to next via gap junctions
direct; gap junctions; ion flow [CNS: sensory cells to neurons; in btwn cardiac cells; neuron to “non-excitable” effectors (e.g. adrenal medulla)]
chemical synapses
-chemical neurotransmitter released from presynaptic neuron
indirect; synaptic cleft; neurotransmitters [PNS; MOST common; neuron to neuron; neuron to “excitable” effectors (e.g. muscles)]
neurotransmitter receptors are grouped into two major types
(1) ionotropic receptors
- ligand-gated ion channels
-fast response
-result in change in Vm
(2) metabotropic receptors
-g protein coupled receptors
-slower response
-can result in Vm
-can result in long term changes in gene expression
three major drivers of resting membrane potential
(1) sodium-potassium pump
(2) leaky ion channels
(3) cellular proteins
leads to..
-more Na+ outside
-more K+ inside
