Anatomy:Chapter 11.1-11.3 and 11.6

sensory input

receptors gather info(internal and external)

integration

nervous system processes and interprets

motor output

effectors(muscles and glands) instructed to respond

CNS

central; brain and spinal cavity; i greg ration and control center

PNS

peripheral- outside CNS; nerves (bundles of axon) that extend from the brain and spinal cord, as well as ganglia (clusters of neuron cell bodies along nerve pathways)

sensory (afferent) division

nerve fibers carry info from receptors to CNS

somatic

skin, skeletal muscles and joints

visceral

organs

motor (efferent) division

impulses transmitted from CNS to effectors, two main parts

somatic

conscious control of skeletal muscles

autonomic

ANS-regulates activity of smooth and cardiac muscles, as well as glands; two functional subdivisions

Sympathetic

mobilized during activity

parasympathetic

regulates restful functions (ex. digestion)

neurons

nerve cells; generate and transmit APs; can function for a lifetime; most do not divide after maturing; high metabolic rate (requires continuous glucose and oxygen supplies)

neuroglia

support cells; more abundant than neurons to ensure proper functions

astrocyte

most abundant and most versatile-anchors neurons to capillaries for nutrients; determine capillary permeability; assist in synapse formation; remove excess ions, neurotransmitters from synapses

microglia

phagocize microorganisms and neural debris

ependymal cells

we cilia to move CSF (cerebrospinal) through/around brain and spinal

oligodendrocytes

insulate thick nerve fibers, forming myelin sheaths

satellite cells

surround neuron cells bodies in the PNS; similar function to astrocyte

schwann cells

surround all cell fibers in the PNS and form myelin sheaths around thick nerve fibers; vital to regeneration of damaged peripheral nerves

cell body

contains nucleus, cytoplasm, numerous mitochondria and other

nuclei

clusters in CNS

dendrite

short, highly branched to create large surface area to receiving signals from other neurons; send graded potential to cell body

graded potential

short, loud impulses

axon

conducting region-produces and conducts impulses away from cell body; long axons called nerve fibers

axon collaterals

only one axon arrives from cell body, but may branch

axon terminal

secretory region; end of axon branches and expand slightly at ends

nerve impulses transmitted

down plasma membrane (axolemma) to axon terminals, where neurotransmitters are secreated into extra cellular space

myelin

covers large/long axon in segments; increasing speed of impulses

nonmyelinated axon

single layer of myelin to conduct impulses more slowly

myelinated

thick layer of myelin to conduct impulses quickly

myelin sheaths gaps

schwann cells do not touch, so myelin sheaths have gaps that occur at 1mm intervals

multipolar

many process extend from the cell body. all are dendrites except for a single axon; 99% of neurons

bipolar

two processes extend from the cell body. one is fused to the dendrite, the other is an axon. only found in retina and olfactory mucosa

unipolar

one process extend from the cell body and form central and peripheral process, which together compromise an axon

sensory

afferent-transmit impulses from sensory receptors to CNS; almost all are unipolar; cell bodies located in ganglia

motor

efferent-transmit impulses from CNS to effectors; multipolar; cell bodies located in CNS

interneurons

association neurons-lie between sensory and motor neurons where intregration occurs typically in the CNS; almost all multipolar

resting membrane potential

are polarized(negative inside membrane, positive outside)

depolarization

an AP briefly reversed the RMP due to energy to entry of Na+

repolarization

once 30mV is reached, Na+ channels close, K+ channels open, K+ exit cells, restoring negativity

hyperpolarization

some K+ channels remain open, causing voltage to dip lower than original RMP

threshold

guarantees the AP; a sub threshold stimulus will not be a full AP, may increase voltage a little

all or none phenomenon

AP either happens or it doesn’t

AP

generate in axons and propagate down axolemma toward axon terminal

refractory periods

ensure AP reaches certain point before responding to stimulus from the new AP

absolute refractory period

neuron cannot respond to a new stimulus on the same spot on the membrane, regardless of its strength; lasts from the time Na+ channels open to the time they close; ensure that each AP is a separate and complete event

relative refractory period

K+ channels still open; exceptionally strong stimulus will reopen Na+ channels to generate a new AP at the same spot on the membrane before hyperpolarization is complete (and RMP is reestablished)

Absolute refractory period

ensures that a new AP will fire on the an adjacent location, as opposed to the same spot again

refractory periods

allow cells to replenish ingredients such as neurotransmitters, oxygen, glucose, calcium(muscle cells requirement for contraction) and also returns ions to original location

speed of conduction

diameter of axon(larger= faster) and degree of myleination(presence of myelin =faster)

continuous conduction

action potential propagates at the adjacent spots on the membrane of the nonmylinated slow because new APs must fire repeatedly to move down the membrane

saltatory conduction

APs only conducted in myelin sheath gaps and appear to “jump” from myelin to gap, which is 30x faster than continuous conduction