Chapter 11 -- Functional Organization of Nervous Tissue

innervate

to supply an organ or other body part with nerves.

microglia

phagocytize microorganisms, foreign substances, and necrotic tissue

astrocyte

star-shaped neuroglia that help to form the blood-brain barrier. provide structural support for neurons and blood vessels. isolate damaged tissue, limit spread of inflammation, help maintain synaptic function

oligodendrocyte

neuroglia that has cytoplasmic extensions that form myelin sheaths around axons in the CNS

ependymal cells

neuroglia that line ventricles of the brain and the central canal of the spinal cord. some are specialized to produce cerebrospinal fluid

name the five functions of the nervous system

1. Maintaining homeostasis

2. Receiving sensory input

3. Integrating information

4. Controlling muscles and glands

5. Establishing and maintaining mental activity

What are the parts of the CNS?

brain and spinal cord

What is the function of the CNS?

Process, integrate, store and respond to information from the PNS

What are the parts of the PNS?

Nervous tissue outside of the CNS, including sensory receptors, nerves, ganglia and plexuses

What are the two divisions of the PNS?

1. Sensory

2. Motor

What does the sensory division of the PNS do?

transmits APs to CNS. usually consists of single neurons with cell bodies in ganglia

What does the motor division of the PNS do?

carries APs away from CNS in cranial or spinal nerves

What are the two subdivisions of the motor division?

1. somatic nervous system/SNS

2. autonomic nervous system /ANS

What does the somatic nervous systems do?

innervates skeletal muscle

is the somatic nervous system mostly voluntary or involuntary?

mostly voluntary

what does the autonomic nervous system do?

innervates cardiac and smooth muscle and glands.

What is the neurological makeup of the SNS?

single neurons that have cell bodies located within the CNS

What is the neurological makeup of the ANS?

The first set has its cell bodies within the CNS and the second set has its cell bodies within autonomic ganglia

What are the two divisions of the ANS?

1. sympathetic division

2. parasympathetic division

What dos the sympathetic division of the ANS do?

chill out mechanism

What does the parasympathetic division of the ANS do?

fight or flight

What does the PNS do?

detects stimuli and transmit information to/receive information from CNS

What does the CNS do?

processes, integrates, stores and responds to information from the PNS

What do neurons do?

receive stimuli and transmit APs

cell body

primary site of protein synthesis in neurons

dendrites

short, branched cytoplasmic extension of cell body that usually conduct electrical signals toward cell body

axon

cytoplasmic extension of cell body; transmits AP toward cell body

multipolar neuron

several dendrites and single axon (e.g., interneurons, motor neurons)

biploar neuron

single axon and dendrite; are components of sensory organs

pseudo-unipolar neurons

single axon

Are most sensory neurons multipolar, bipolar or pseudo-unipolar?

pseudo-unipolar

neuroglia

non-neural cells that support, aid neurons of CNS/PNS. maintain homeostasis, form myelin, and provide support and protection for neurons in the brain and peripheral nervous system. Includes astrocytes, oligodendrocytes, micro glia and ependymal cells

astrocytes

star-shaped neuroglial cell involved with forming the blood-brain barrier

Schwann cell

forms myelin sheath around part o axon of a PNS neuron

satellite cell

supports, nourishes neuron cell bodies within ganglia

myelinated axons

wrapped by several layers of plasma membrane from Schwann cells (PNS) or oligodendrocytes (CNS)

node of Ranvier

spaces between plasma membrane wrappings on axon

unmyelinated axons

rest in invaginations of Schwann cells (PNS) or oligodendrocytes (CNS) that conduct APs slowly

white matter

myelinated axons, propagates APs

gray matter

collections of neuron cell bodies or unmyelinated axons

axons _________ with neuron cell bodies

synapse

what does white matter form?

nerve tracts in CNS and nerves in PNS

what does gray matter form?

cortex and nuclei in the CNS and ganglia in the PNS

resting membrane potential

charge difference across plasma membrane when cell is in unstimulated condition. inside of cell is negatively charged compared out outside of cell

depolarization

decrease in resting membrane potential. inside of membrane becomes more positive because Na diffuses into cell through voltage-gated ion channels

hyperpolarization

increase in resting membrane potential

graded potential

small change in RMP that is confined to small area of plasma membrane

why is it called a graded potential?

a stronger stimulus produces a greater potential change than a weaker stimulus

why does a graded potential decrease in magnitude?

decreases in magnitude as the distance from the stimulation increases

action potential

larger change in resting membrane potential that spreads over the entire surface of the cell

threshold

membrane potential at which a graded potential depolarizes the plasma membrane sufficiently to produce an AP

repolarization

return on MP toward the resting state. voltage-gated ion Na channels close, Na diffusion into cell slows to resting levels. voltage-gated K channels continue to open, K diffuse out of cell

afterpotential

brief period of hyperpolarization following repolarization

absolute refractory period

period following effective stimulation during which excitable tissue (e.g., heart muscle) fails to respond to stimulus of threshold intensity

relative refractory period

follows absolute refractory period; stronger-than-threshold stimulus can evoke another AP

subthreshold stimulus

produces only graded potential

threshold stimulus

causes graded potential that reaches threshold, results in single AP

submaximal stimulus

greater than a threshold stimulus, weaker than maximal stimulus

maximal/supramaximal stimulus

produces maximum frequency of action potentials

action potentials propagate most rapidly in _____, _____-____ axons

myelinated, large-diameter

electrical synapses

gap junctions in which tubular proteins (connexons) allow local currents to move between cells

presynaptic terminal

enlarged ends of axon; contain synaptic vesicles

postsynaptic membranes

contain receptors for neurotransmitter

synaptic cleft

space separating the presynaptic and postsynaptic membranes

neurotransmitter

any specific chemical agent released by a presynaptic cell on excitation that crosses the synaptic cleft and stimulates or inhibits the postsynaptic cell

neuromodulator

substance that influences the sensitivity of neurons to neurotransmitters but neither strongly stimulates or strongly inhibits neurons by itself

EPSP

excitatory postsynaptic potential. depolarizing graded potential of the postsynaptic membrane

IPSP

inhibitory postsynaptic potential. hyperpolarizing graded potential of postsynaptic membrane

spatial summation

occurs when two or more presynaptic terminals simultaneously stimulate a postsynaptic neuron

temporal summation

occurs when two or more APs arrive in succession at a single presynaptic terminal

convergent pathways

many neurons synapsing with a few neurons

divergent pathways

few neurons synapsing with many neurons

oscillating circuits

collateral branches of postsynaptic neurons synapsing with presynaptic neurons

ligand

a molecule, such as a neurotransmitter or hormone that binds to a receptor

when membrane potential increases compared to RMP, the inside of the membrane becomes _____________. This is called _____________.

more; hyperpolarization

saltatory conduction

propagation of action potentials along myelinated axons from one node of Ranvier to the next node. (from the Latin saltare, to hop or leap)