Ch. 12 Neural Tissue

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2 kinds of cells in Nerve tissue:

neurons, neuroglia

Cells that send and receive signals:

Neurons, also the function unit of nerve cells.

Neuroglia:

cells that support and protect neurons

2 Divisions of Nervous System:

CNS- brain & spinal cord, used to process and coordinate act. in the body; PNS- all neural tissue outside CNS

Functions of CNS:

Used to process & coordinate activities in the body

Functions of PNS:

Deliver sensory information to the CNS, and gets message back of what to do.

Cranial nerves connect to the:

brain (12 cranial nerves)

Spinal nerves attach to the:

spinal cord (31 spinal nerves)

Functional Divisions of PNS:

afferent, efferent

Afferent:

(TO) Carries sensory information from PNS sensory receptors TO CNS

The primary function(s) of the nervous system include:

providing sensation to the internal & external environments, integrating sensory info, & regulating and controlling peripheral structures & systems

Neurons are responsible for:

information transfer and processing in the nervous system

The region of a neuron with voltage-gated sodium channels is the:

axon hillock

Neurons are classified on the basis of their structure as:

motor, sensory, association

The two major cell populations of neural tissue are:

neurons and neuroglia

CNS glial cell that removes debris, wastes, and pathogens by phagocytosis:

microglia

The white matter of the CNS represents a region dominated by the presence of:

oligodendrocytes

Depolarization of the membrane will shift the membrane potential toward:

0 mV

What is the term given to describe a shift in transmembrane potential from -70 mV to -90 mV?

hyperpolarization

If resting membrane potential is -70 mV and the threshold is -60 mV, a membrane potential of -62 mV will:

not produce an action potential

At the site of an action potential, the membrane contains:

an excess of positive ions inside and an excess of negative ions outside

A node along the axon represents an area where there is

an absence of myelin

Nerve cell bodies in the PNS are clustered together in masses called:

ganglia

The most important factors that determine the rate of action potential conduction are:

the presence or absence of a myelin sheath and the diameter of the axon

At an electrical synapse, the presynaptic and postsynaptic membranes are locked together at:

gap junctions

Exocytosis and the release of acetylcholine into the synaptic cleft is triggered by:

calcium ions flooding into the axoplasm

Inhibitory or hyperpolarizing CNS neurotransmitters include:

dopamine and serotonin

An excitatory postsynaptic potential (EPSP) is:

a depolarization produced by the arrival of a neurotransmitter

An inhibitory postsynaptic potential (IPSP) is a:

transient hyperpolarization of the postsynaptic membrane

Sensory neurons are responsible for carrying impulses:

to the CNS

Interneurons, or associated neurons, differ from sensory and motor neurons because of their:

exclusive location in the brain and spinal cord

Efferent pathways consist of axons that carry impulses:

away from the CNS

Graded potentials that develop on the postsynaptic membrane in response to a neurotransmitter are:

postsynaptic potentials

The addition of stimuli occurring in rapid succession is:

temporal summation

When sensory information is relayed from one processing center to another in the brain, the pattern is called

serial processing

Interneurons are responsible for:

analysis of sensory inputs and coordination of motor outputs

Sensory (ascending) pathways distribute information

from peripheral receptors to processing centers in the brain

Schwann cells are glial cells responsible for:

producing a complete neurilemma around peripheral axons

When a barrier prevents the movement of opposite charges toward one another, a(n)

potential difference exists

The sodium-potassium pump's activity is needed after:

every action potential to restore resting potential

All-or-nothing principle:

A given stimulus either triggers a typical action potential or does not produce one at all

During the relative refractory period, a larger-than-normal depolarizing stimulus can:

bring the membrane to threshold and initiate a second action potential

Saltatory conduction conducts impulses along an axon

five to seven times faster than continuous conduction

In type C fibers action potentials are conducted at speeds of approximately

2 mph

The larger the diameter of the axon, the

faster the rate of transmission

dipping toe in cold water, pulling back.. The sensory neurons responsible for this is:

exteroceptors

The main functional difference between the autonomic nervous system and the somatic nervous system is that the activities of the ANS are

primarily involuntary or under "automatic" control

Reverberation in neural circuits refers to collateral axons that:

use positive feedback to simulate presynaptic neurons

What is happening during a "runners high"?

Endorphins are blocking the transmission of substance P, a neurotransmitter that sends information about pain to the CNS

The most excitatory neurotransmitter in the brain and functions in learning and memory:

glutamate

What are the two major ions that are involved in generating an action potential?

sodium and potassium. These ions determine the gradient that drives the depolarization of the membrane.

What do we call the difference in charge between the inside of the nerve cell membrane and the outside?

the membrane potential. The difference in charge between the inside and outside of the membrane gives the membrane its responsive nature.

What is the first thing needed to start an action potential?

a stimulus. In order for an action potential to be produced, there has to be a stimulus great enough to start the cascade effect down the axon.

What ion initiates the formation of vesicles filled with acetylcholine?

calcium. As the axon potential arrives at the synaptic terminal, calcium channels open and with calcium influx, the formation of vesicles begins.

When the membrane potential is disturbed, which ion enters the cell?

sodium. When the stimulus causes a disruption in the cell membrane, sodium rushes into the cell.

What do we call the change in the sodium and potassium ions caused by a stimulus?

depolarization. When sodium rushes in, it causes a change in the membrane potential that starts the message down the axon.

When there is no stimulus to the nerve cell, is the cell said to be..

at rest. Homeostasis refers to the body's maintenance of a stable internal environment.

How is potassium recaptured after depolarization?

sodium-potassium pumps. The pumps are responsible for reclaiming the ions so the cell can respond again.

The space between nerve cells is called the

synapse

What is the ion responsible for initiating the formation of acetylcholine?

Calcium

What are the chemicals called that propagate the message across the synapse?

neurotransmitters

What is the most abundant neurotransmitter in the body

acetylcholine.

The part of the cell that receives the impulse is called

the dendrite

glial cells that surround cell bodies in the PNS and regulates levels of oxygen and carbon dioxide around ganglionic neurons:

satellite cells

glial cells that can form a myelin sheath around axon fibers in the central nervous system:

oligodendrocyte

The binding of ACh on the axon hillock triggers

the opening of voltage-gated channels.

Synaptic delay is greater at synapses of..

myelinated neurons than at those of unmyelinated neurons.

A chemical synapse at which the neurotransmitter is acetylcholine is called

cholinergic synapse

Receptors of afferent division:

detect changes or respond to stimuli

Effectors of afferent division:

respond to efferent (taking signals away from brain and bringing back to PNS) signals

Somatic nervous system (SNS):

controls skeletal muscle contractions: voluntary and involuntary (reflexes) muscle contractions

Autonomic nervous system (ANS):

controls subconscious actions: contractions of smooth muscle and cardiac muscle and glandular secretions

sympathetic division:

has a stimulating effect (speeds), adrenaline rush

parasympathetic division:

has a relaxing effect (slows), when stuck with needle, get a vegas response due to vegas nerve.

___ perform all of the communication, information processing, and control functions of the nervous system.

neurons

multipolar neuron

Common in the CNS:
cell body (soma)
short, branched dendrites
long, single axon (tail)

Perikaryon

(cytoplasm)

RER and ribosomes produce..

neurotransmitters

Neurofibrils:

bundles of neurofilaments that provide support for dendrites and axon

Nissl Bodies:

Dense areas of RER and ribosomes
Make neural tissue appear gray (gray matter, not mylenated; slower)

Dendrites:

look like little fingers

Dendritic spines:

many fine processes
receive information from other neurons
80-90% of neuron surface area

The axon

(long tail) Carries electrical signal (action potential) to target, Axon structure is critical to function

Axoplasm

Cytoplasm of axon
Contains neurotubules, neurofibrils, enzymes, organelles

Axolemma

Specialized cell membrane
Covers the axoplasm

Axon hillock

where tail attaches to cell body, Thick section of cell body
Attaches to initial segment

Telodendria

Fine extensions of distal axon

Synaptic terminals

Tips of telodendria

Synapse:

(gap in neuron connection)
Area where a neuron communicates with another cell

The synapse steps:

Presynaptic cell, Postsynaptic cell, The synaptic cleft

Presynaptic cell

neuron that sends message

Postsynaptic cell:

cell that receives message

The synaptic cleft:

the small GAP that separates the presynaptic membrane and the postsynaptic membrane

The synaptic knob

Is expanded area of axon of presynaptic neuron, Contains synaptic vesicles of neurotransmitters

Neurotransmitters

are chemical messengers, released at presynaptic membrane, affect receptors of postsynaptic membrane, are broken down by enzymes, are reassembled at synaptic knob

Recycle Neurotransmitters through..

Axoplasmic transport (have to have ATP for it to work)Neurotubules within the axon
Transport raw materials
Between cell body and synaptic knob
Mitochondria is imp. for cell functions with ATP

Neuromuscular junction

Synapse (GAP) between neuron and muscle

Neuroglandular junction

Synapse (GAP) between neuron and gland

Synovial fluid:

reduce friction, Contains slippery proteoglycans secreted by fibroblasts, Functions of synovial fluid lubrication, nutrient distribution, shock absorption

The place where the fixed end attaches to a bone, cartilage, or CT is called..

origin of the muscle.

The site where the movable end attaches to another structure is called..

insertion of the muscle.

The origin is typically proximal to the..

insertion

Imaginary part of the pelvis the baby comes through during birth:

pelvic outlet

The four types of muscles identified by different patterns of organization are:

parallel, convergent, pennate, circular

In a convergent muscle the muscle fibers are:

based over a broad area, but all the fibers come together at a common attachment site

Muscles responsible for shrugging shoulders:

trapezius

Anaxonic neurons:

(ana- without), no tail, Found in brain and sense organs, Small, All cell processes look alike

Bipolar neurons

Found in special sensory organs (sight, smell, hearing); Are small, One dendrite, one axon

Unipolar neurons

cell body is budding off, 2 ends; Found in sensory neurons of PNS, Have very long axons, Fused dendrites and axon, Cell body to one side

Multipolar neurons

Common in the CNS, Include all skeletal muscle motor neurons; Have very long axons, Multiple dendrites, one axon

Three Functional Classifications of Neurons:

sensory, motor, interneurons

Sensory Neurons:

afferent (takes info to CNS) neurons of PNS; Monitor internal environment (visceral sensory neurons), Monitor effects of external environment (somatic sensory neurons

Motor Neurons:

Efferent (brings it back from CNS to PNS) neurons of PNS

Interneurons

assocation neurons

Structures of sensory neurons:

Unipolar, Cell bodies grouped in sensory ganglia, Processes (afferent fibers) extend from sensory receptors to CNS

Three Types of Sensory Receptors:

Interoceptors, Exteroceptors, Proprioceptors

Interoceptors:

Monitor internal systems (digestive, respiratory, cardiovascular, urinary, reproductive) Internal senses (taste, deep pressure, pain)

Exteroceptors:

(external) External senses (touch, temperature, pressure), Distance senses (sight, smell, hearing)

Proprioceptors:

Monitor position and movement (skeletal muscles and joints) (tells you if ur standing up right, lying down)

Motor Neurons:

Carry instructions from CNS to peripheral effectors via efferent fibers (axons)

Two major efferent systems:

Somatic nervous system (SNS):
includes all somatic motor neurons that innervate skeletal muscles
Autonomic (visceral) nervous system: involuntvary visceral motor neurons innervate all other peripheral effectors, smooth muscle, cardiac muscle, glands, adipose tissue

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