unit 6 test

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central nervous system

central nervous system

brain and spinal cord

peripheral nervous system

nerves

sensory nerves (afferent)

impulses are sent to the CNS; detect changes inside and outside of the body

integration

within CNS; processing incoming sensory input decision making

motor

impulse sent from CNS to effectors to cause response

neurons

nerve cells; conduct impulses

neuroglia

surrounds nerve cells; do not conduct impulses

parts of a neuron

cell body, dendrites, axon

cell body

cytoplasm, mitochondria, lysosomes, microtubules, golgi apparatus, nucleus

nissl bodies

chromatophilic substance that consists mainly of rough er

dendrites

receive input; highly branched. provide many receptors; can be 1 or more

axon

transmits input; carries the input away from the cell body; usually one long fiber

impulses travel

dendrite-> cell body-> axon

multipolar

1 axon and MANY dendrites

bipolar

1 axon and 1 dendrite

unipolar

1 process which splits into 2 branches, the peripheral and central processs

sensory neurons (afferent)

carry impulses from peripheral body parts to CNS

interneurons

lie within the CNS and form links with other neurons

motor neurons (efferent)

carry impulses from CNS to peripheral body parts

neuroglial cells in PNS

schwann and satellite

neuroglial cells in CNS

astrocytes; oligodendrocytes; microglia; ependyma

schwann cell

produce myelin on myelinated neurons

how do schwann cells wrap around

tightly wrap around fibers, forming a myelin sheath; just neurilemma with no myelin sheath

satellite cell

clusters of neuron cell bodies called ganglia

myelinated fiber

fiber that has a myelin sheath; impulse travels faster

unmyelinated fiber

fiber that does not have a myelin sheath; impulse travels slower

gray matter

nervous tissue containing lots of cell bodies and unmyelinated fibers

white matter

nervous tissue containing lots of myelinated fibers

astrocyte

large star shaped cells between neurons and blood vessels; structural support, communication, and transportation between blood vessels and neurons

oligodendrocytes

shaped like astrocytes with fewer processes, occur in rows along axons; form myelin sheath in the CNS ( NO neurilemma)

microglia

small cells with few processes found throughout CNS; structural support and phagocytosis

ependyma

cuboidal and columnar cells in the brain and spinal cord that line the cavities; help with diffusion

regeneration in CNS

no regeneration; no endoneurial tube and no neurilemma

regeneration in PNS

might occur; bc the endoneurium's presence may prevent scar tissue from coming in before the process can regrow

synapse

junction between axon of one neuron and dendrite or cell body of another neuron

presynaptic fiber

neuron which sends impulse to synapse; releases neurotransmitters into synaptic cleft

postsynaptic fiber

neuron which has receptors for the neurotransmitters

first step in synaptic transmission

Presynaptic knob of axon contains vesicles filled with neurotransmitters.

second step in synaptic transmission

When impulse reaches knob, Ca++ diffuses into cytoplasm.

third step in synaptic transmission

Vesicles move to membrane and release neurotransmitters into cleft.

fourth step in synaptic transmission

Neurotransmitters cross cleft and bind to receptors on postsynaptic membrane of neuron (either dendrite or cell body)

fifth step in synaptic transmission

If enough neurotransmitters are present, an action potential will occur.

sixth step in synaptic transmission

Neurotransmitters are either decomposed or they move back into presynaptic knob.

neuron potential

the concentration of ions on either side of the membrane affects its charge distribution

changes in potentials

when a stimulus encounters a neuron, it responds by changing its permeability to various ions, which affects the potentional

hyperpolarized

the resting membrane becomes more negative

depolarized

the resting membrane becomes more positive

nerve impulse

if stimulus is strong enough it cause Na gates to open Na flows into cell, depolarizing membrane action potential is reached at +30 mV K+gates open K+ moves out, repolarizing membrane hyperpolarizes for brief moment active transport pumps Na out and K in

resting potential

The charge distribution when a nerve is at rest. No impulse being conducted, so membrane is not very permeable to POTASSIUM (K+) and even less permeable to SODIUM (Na+). Active transport has to be used to pump K+ in and Na+ out. More negatively charged ions on the inside of the cell so more positive particles are going to move in (attraction): More Na+ on outside, K+ on inside Membrane is positive on the outside, negative on the inside Membrane is said to be polarized -70mV- is the difference in charges (resting potential)

action potential

the rapid sequence of Na and K movements

nerve impulse

chain reaction of action potentials

all-or-none response

if a neuron responds at all, it responds COMPLETELY or conducts COMPLETELY or not at all

refractory period

a short time period after a nerve impulse where a stimulus will not conduct the neuron

saltatory conduction

type of impulse conduction along myelinated fibers

nerve impulse speed

thick faster than thin myelinated faster than unmyelinated

excitatory postsynaptic potential

neurotransmitter triggers Na+ gates to open and membrane is depolarized (more likely reach action potential)

inhibitory postsynaptic potential

neurotransmitter triggers K+ gates to open and membrane is hyperpolarized (less likely to reach action potential)

facilitation

if a neuron receives a net excitatory stimulation, but is subthreshold it is more susceptible to an action potential the next time

monoamines

modifications of amino acids

epinephrine

boost of energy

dopamine

feel good hormone

serotonin

mood stabilizer

amino acids

unmodified amino acids

glycine

inhibitory neurons in brain and spinal cord

gamma-aminobutyric acid (GABA)

inhibitory neurons in brain and spinal cord

peptides

short chains of amino acids

substance P

pain perception

endorphins

reduces pain

convergence

when a neuron receives impulses from 2 or more other neurons allows the brain to receive info from different regions of the body and respond in a special way

divergence

when 1 neuron sends impulses to 2 or more other neurons-results in an amplified response

sensory fibers

contains only sensory fibers (afferent)

motor fibers

contains only motor fibers (efferent)

mixed fibers

contains both sensory and motor fibers

general somatic efferent fibers

carry impulses from CNS to skeletal muscles

general visceral efferent fibers

carry impulses from CNS to smooth muscles and glands

general somatic afferent fibers

carry impulses from skeletal muscles and skin to CNS

general visceral afferent fibers

carry impulses from smooth muscles and glands to CNS

reflex arc

simple impulse pathway during a reflex

receptor

specialized nerve endings stimulated by change

effector

smooth muscle or gland that responds

meninges

found beneath the bone and soft tissues of nervous system; brain and skull, spinal cord and vertebral column protect the brain and spinal cord

3 layers outer to inner

dura mater arachnoid mater pia mater

meningitis

inflammation of the meninges

spinal cord

31 segments ends between 1 and 2 lumbar relays impulses and info between body and CNS