Chapter 10: Nervous System

What are the nervous system functions?

sensory input (detects changes)

integration and processing (making decisions)

motor output (stimulates muscles and glands to respond)

Main cells types of nervous system:

neurons (nerve cells)

neuroglia

Neurons aka nerve cells do what?

respond quickly to changes/stimuli and conduct electrical impulses via neurotransmitters

Neuroglia does what?

protect, support, insulate, and nourish neurons

Neuroglia does not conduct what?

electrical impulses like neurons

CNS (central nervous system) includes the?

brain and spinal cord

PNS (peripheral nervous system) connects what?

CNS to other body parts

PNS consists of?

cranial nerves and spinal nerves

What are the two subdivisions of PNS?

afferent-sensory

efferent-motor

Sensory receptors perform?

sensory functions

Impulses conducted along peripheral nerves to CNS for?

integration

Neurons that transmit impulses from CNS to effectors perform?

motor function

Effectors are muscles or glands outside?

nervous system

What are the two motor divisions?

somotic and autonomic

What is somatic?

transmits voluntary commands to skeletal muscles

What is autonomic?

transmits involuntary commands to viscera

Neurons vary in?

size and shape

Neurons may differ in?

length, number, and size of axons and dendrites

Nuerons share certain structural features like?

cell body (soma), dendrites, axons

Cell body (soma or perikaryon)is?

contains nucleus, cytoplasm, organelles, neurofilaments, chromatophilic substance (Nissl bodies)

Dendrites are?

branched receptive surfaces; a nueron may have many

An axon transmits impulses and releases neurotransmitters to?

another nueron or effector

Structural features of an axon are?

axon hillock, collaterals, axon terminal, synaptic knob

Schwann cell is?

neuroglia of the PNS that wrap around some axons in layers

Axon hillock is?

cone shaped area of cell body from which axon arises

What is a myelin?

mixture of fats and proteins that fill layers made by schwann cell membranes

Myelin sheath is?

a wrapped coating around some PNS axons, composed of layers of schwann cell membranes and myelin acts as electrical insulator

Nodes of Ranvier is?

gaps in myelin sheath between schwann cells

Not all axons are?

myelinated

Myelinated axons produce?

Oligodendrocytes in CNS

Myelinated axons produce a series of?

Schwann cells lined up along axon in PNS

Unmyelinated axons encase by schwann cell cytoplasm in PNS but?

no wrapped coating of myelin surrounding the axons

Groups of unmyelinated axons in CNS comprise?

gray matter

Classification of neurons by structure are?

multipolar neurons, bipolar neurons, unipolar neurons

Classification of neurons by function include?

sensory, Interneurons, motor

Sensory (afferent) neurons carry impulses to?

periphery to CNS (brain or spinal cord)

Motor (efferent) neurons carry impulses from?

CNS to effectors (muscles or glands)

General functions of neuroglia include?

support for neurons, guide, produce growth factors, aid in formation

Astrocytes connect neurons to blood vessels that exhange?

nutrients and growth factors

What do astrocytes form?

scar tissue

Astrocytes also do what?

aid in metabolism of certain substances

regulate ion concentrations K+

part of blood brain barrier

Oligodendrocytes myelinate?

CNS axons; also provide structural support

Microglia do what?

Phagocytic cells; also provide structural support

Ependyma or ependymal cells:

Line central canal of spinal cord & ventricles of brain, cover choroid plexuses

help regulate composition of cerebrospinal fluid

Ciliated cuboidal or columnar cells

Satellite cells support?

clusters of neuron cell bodies (ganglia)

Exciteable cells can?

rapidly change internal charge

Membrane potential charge inside a cell and has a “potential” to?

transport charges across membrane

Resting membrane potential is a charge inside cell when it is inactive and about?

-70mV

Potassium K ions are in?

higher concentration inside than outside

Sodium Na ions are in?

higher concentration outside than inside

Sodium and potassium follow the rule of?

diffusion (high to low)

Action potential is?

sequence of electrical events in an excitable cell,
involving changes in membrane potential, first positive and then negative, to return to resting potential; action potentials are used for communication between cells

The Na/K pump maintains balance in ion movement across membrane

When resting potential is disturbed, it pumps 3 Na+ ions out of cell and 2 K+ ions into cell and uses energy of ATP to actively transport these ions in opposite directions across membrane

What is stimulus?

anything that can change resting potential of −70 mV in
either direction

Local potential changes are graded which means?

the greater the stimulus intensity, the greater the potential change

Excitatory stimulus opens chemically gated Na+ channels this makes inside?

neuron less negative

Threshold stimulus:

Excitatory stimulus that causes enough Na+ ions
to flow into cell that it reaches Threshold Potential of −55 mV

Depolarization is?

Change from negative to positive charge inside cell,
making both sides of membrane positive

All-or-None Law is?

Reaching an action potential; either achieved or not

Repolarization is?

Return to resting potential after action potential;
occurs as K+ channels open and K+ ions rush out of cell; polarity
returns

Hyperpolarization is?

Slight overshoot at end of repolarization, in which
potential drops below −70 mV for a moment before returning to −70
mV

Two refractory period include?

absolute refractory and relative refractory

Absolute refractory is when?

time when threshold stimulus cannot generate another action potential

Relative Refractory period is when?

time when only high intensity stimulus can generate another action potential

Speed of impulse conduction varies with?

myelination

Unmyelinated axons conduct?

impulses over entire length

Myeline is rich in?

lipids

Myelinaed axons transmit impulses through?

saltatory conduction, in which action potentials “jump” from node to node down the axon

Neurons communicate with each other at a?

synapse

Synapse:

a site at which a neuron transmits a nerve impulse to another region

presynaptic neuron sends impuse

postsynaptic neuron receives impulse

synaptic cleft separates the 2 neurons

Synaptic transmission is the process?

by which presynaptic neuron sends impulse to postsynaptic neuron

EPSP:

membrane change in which neurotransmiter open Na channels

depolorizes membrane of postsynaptic neuron as Na enters axon

action potential in postsynaptic neuron becomes more likely

Inhibitory postsynaptic potential (IPSP):

membrane change in which nuerotransmitter opens K+ channels or Cl- channels

hyperpolorizes membrane of postsynaptic neuron as K+ leaves axon

action potentional of postsynaptic neuron becomes less likely

EPSP and IPSO are added together in a process called?

summation

Net excitatory effect leads to?

great probability of an action potential

True or false: net inhibitory effect does not generate action potentials?

true

The way the nervous system processes nerve impulses and acts upon them reflects the?

organization of neurons and axons in the brain and spinal cord

Repeated impulses on an excitatory presynaptic neuron may cause that neuron to release more nuerotransmitter in response to a single impulse is?

facilitation

Convergence is one neuron that receives input from several neurons but also?

allows nervous system to collect, process, and respond to information

Divergence is one neuron that sends impulses to several neurons via branching of its axon and also?

can amplify an impulse