661 neuronal structure and PNS

what is the fundamental functional unit of the nervous system

neuron

what are the functional regions of a neuron

input, integrative, conductive, output

membrane of soma

hydrophobic, binds together cytoplasm (organselles and cytosol - aqueous part)

nucleus of the soma

has chromosomes for protein production

endoplasmic reticulum

tubes that isolate, modift, store, and transport proteins and lipids (rough has ribosomes for protein synthesis and smooth is for lipid synthesis)

lysosomes in soma

digest compounds, glycogen to glucose, axoplasmic transport system

golgi appartatus in soma

stores proteins and lipids

microtubules in soma

axonal transport, relay structures down the axon

function 1 of axons

transmission of information by proagation of action potential (sending information along)

function 2 of axon

transportation of metabolically important materials to and from the cell body to the axonal end

anterograde

from the cell body out to axon

retrograde

from axonal end back to cell body

what are the electric and physical principles of the neuronal cell membrane

two hydrophobic phospholipid bilayers, tries to keep everything on the outside away from everything on the inside, protein from channels for ions to pass through

what are the active mechanisms of ion transport

Na+/K+ pump and requires ATP

what are the two types of force that guide movement of ions

electrostatic force and diffusion force

electrostatic force

charges repel each other

diffusion force

ions move from higher to lower concentration

T/F electrostatic forces are stronger than diffusion forces

F (false)

ligand gates ions channels

made of multiple proteins, ligand molecule (neurotransmitter) attaches to the receptor and opens the channel (ions then move inside)

mechanically gates ion channels

opens in response to any mechanical stimulus like pressure or stretch

voltage gated ion channels

opens when membrane potential reaches threshold, Na+ channels open at -55 millivolts and close at 30+ millivolts

leakage channels

open at rest randomly, ions can pass in either direction, more K+ than Na+ leakage channels

T/F maintenance of the resting membrane potential requires an active mechanism that uses ATP

T (true)

T/F schwann cells are only associated with myelinated axons

F (false)

depolarizations

inside becomes less negative (stimulus causes the number of millivolts to become less negative - excititory)

hyperpolarization

inside becomes more negative (inhibitory event)

what is the threshold for there to be an action potential

-55

postsynpatic potential (PSP)

graded potential, excitatory vs inhibitory

excititory synapse (EPSP)

insides becomes more positive than RMP (membrane becomes depolarized)

inhibitory synapse (IPSP)

inside becomes more negative than RMP (membrane becomes hyperpolarized)

what phase tries to get the action potential to end

repolarizing phase

what are the phses to get back to resting membrane potential

stimulus, depolarization phse, repolarization phase, hyperpolarization phase, resting membrane potential

when do Na+ sodium gates close

+30 mV

action potential propogation

wave of depolarization travels quickly along the membrane, positive charge in axon is attracted to the negative charge adjacent to it, absolute refractory period prevents another AP from happening too soon

describe motor nerve fibers

myelinated, large

decrbie sensory nerve fibers

myelinated, thinly myelinated, and unmyelinated, large to small

describe autonomic nerve fibers

thinly myelinared, unmyelinated, small

a patient with peripheral neuropathy has preferential degredation of small diameter unmyelinated nerve fibers. is it very likely that this patient has lost what

pain and temperature sensations

functions of myelin sheath

electrical insulator for parts of axon which would prevent AP from developing, allows accumulation of charge at nodes of ranvier, speeds up conduction of AP

what are the structures of a synapse

presynaptic axon terminal, zone of apposition (cleft), postsynaptic cell

T/F there is one direction for chemical synapses

T (true)

synapse sequence

AP arrives, influx of Ca, exocytosis of vesicles with neurotransmitters into the cleft, neurotransmitter binds to post synaptic membrane channel, influx of Na, AP is generated

steps of neurotransmitter recovery and degradation

diffusion, reuptake, enzymatic destruction, desensitization, synaptic fatigue

neutrotransmitter diffusion

away from synapse

neutrotransmitter reuptake

neutrotransmitter reenters presynaptic axon terminal

neutrotransmitter enzyme destruction

inside terminal cytosol or synaptic cleft

neutrotransmitter desensitization

neutrotransmitter becomes inactive

neutrotransmitter synaptic fatigue

occurs if the presynaptic vesicles are released at a faster rate than reuptake can recycle them

signals are propagated fastest when

axons are myelinated and have a large diameter

most synapses are chemical using

neurotransmitters

which sensory nerve fibers transmit faster; touch and vibration, pain, or autonomic system

touch and vibration

myelinated axons in PNS

schwann cells myelinate axons by investing them with concentric layers from myelin sheath

unmyelinated axons

no myelin sheath, associated with and enveloped by schwann cells that provide trophic support (keeps axons alive)

purposes of the nervous system

coordination, voluntary and involuntary movement, cognition, respond and adapt to internal and external demands

what needs to happen in the nervous system when you go from first identifying thirst to taking a drink of water when on a hike?

sensory input (mouth is dry, headache, sweaty) - hypothalamus identify where the water bottle is (memory) , nervous system sends signal to fire muscles

autonomic nervous system (communication with internal organs and glands)

sympathetic division (arousing) and parasympathetic division (calming)

somatic nervous system (communicates with sense organs and voluntary muscles)

sensory (afferent - sensory input) and motor (efferent - motor output)

spinal cord (CNS)

conveys sensory input from body and organs, has fibers and cells that control motor output/function of the body and viscera

brainstem includes

midbrain (eyes and hearing) pons (relfex like chewing) medulla oblongata (HR, BP)

cerebellum is in charge of what

coordination, balance, posture

diencephalon

main processing center for info to the cerebral cortex from ascending sensory pathways

PNS includes

spinal nerves, cranial nerves, autonomic ganglia and autonomic nerves to viscera and glands

cranial nerves come off of the

brain stem

PNS includes

ANS, 31 pairs of spinal nerves, 12 pairs of cranial nerves

the dorsal root is for

sensory/afferent

the ventral root is for

motor/efferent

describe spinal nerve

mix of motor and sensory, splits into rami that go to plexus

what are the connective tissue layers of a spinal nerve

epineurium, perineurium, and endoneurium

describe sensory/afferent info traveling to spinal cord

mechanical stimulus at skin creates electrical impuse, dorsal root ganglion, one end is connected to receptor, enters the spinal cord via dorsal horn, relays info at the spinal level and the supraspinal level

sections of plexus

roots to trunks to division to cords to branches

describe motor component of SPN

spinal motor neurons, axons leave spinal cord via ventral roots, innervate skeletal muscles

types of anterior horn cells

alpha and gamma

what is the purpose of the anterior horn cells

motor output (myelinated)

motor unit

a single alpha motor neuron and all the muscle fibers it innervates

T/F all muscles in motor unit contract together when neuron fires

T (true - all or none law)

what nerve roots have a ganglion

dorsal

T/F every muscle has only one motor unit

F (false)