Nervous Tissue

1. sensory input

2. integration

3. Homeostasis

4.mental activity

5.output

5 functions of the nervous system

Sensory (afferent) neurons

Detect changes in body and external environment

information transmitted into brain or spinal cord

Interneurons

-lie between sensory and motor pathways in CNS

-90% of our neurons are interneurons

-process, store and retrieve information

motor (efferent) neurons

-send signals out to muscles and gland cells

-organs that carry out responses called effectors

CNS and PNS

What are the 2 major anatomical subdivisions of the nervous system?

PNS

The ______ has cranial nerves: originate from the brain; 12 pairs and

Spinal nerves: originate from spinal cord; 31 pairs

Dendrites, axons, cell body

Structures of a neuron

Axon hillock

Where does an axon originate?

Multi-polar

_______ neuron is the most common (brain and spinal cord) and has many dendrites + one axon

Bipolar

________ neuron has olfactory, retina, ear and 1 dendrite + one axon

Unipolar

______ neuron is sensory from skin/organs to spinal cord and only has a single process leading out of soma

anaxonic

_______ neuron deals with visual processes, perception and has many dendrites + no axon

Unipolar

______ neuron deals with quick sensory reflexes such as pulling your hand back on a hot stove

Many proteins made in soma must be transported to axon and axon terminal

What is axonal transport?

Important for repairing axolemmas, gated ion channels protein passageway

Why is there axonal transport?

Anterograde

Movement of proteins away from soma down the axon

Retrograde

Movement of proteins toward the soma up the axon

Kinesin

Motor protein for anterograde transport

Dynein

Motor protein for retrograde transport

Fast and slow

Two types of axonal transport

Anterograde and retrograde

Fast axonal transport has ______ transport

Anterograde

Slow axonal transport has ______ transport

6

There are ______ types of neuorglia

No

Do neurons outnumber neuroglia?

Central Nervous System (4)

Oligodendrocytes

Microglia

Ependymal cells

Astrocytes

Peripheral Nervous System (2)

Schwann cells

Satellite cells

Which neuroglia are in the CNS and which are in the PNS?

Oligodendrocytes

form myelin sheaths to insulate the nerve fiber

Microglia

-Respond to inflammation

-Phagocytize necrotic nervous tissue, microorganisms, and foreign substances that invade the CNS

Macrophages

Microglia are considered specialized _______

Secrete cerebrospinal fluid

ependymal cells function

ependymal cells

Astrocytes

Tightly seals blood brain barrier, stimulates vasoconstriction/vasodilation, most abundant cell in CNS

Astrocyte

Astrocytosis

_______ is the process of forming hardened scar tissue to fill in dead space in damaged neurons

Schwann cells

-wrap repeatedly around portion of only one axon to form myelin

-Can assist in regeneration of damaged nerve fibers

Satellite cells

surround neuron cell bodies in ganglia, provide support and nutrients

Myelin sheath

The ________ is a spiral layer of insulation around a nerve fiber

Endoneurium

loose connective tissue that encloses axons and their myelin sheaths

Neurilemma

the outermost coil in schwann cell known as the ________

Cannot, segments

Because nerve fibers are so long...a single Schwann cell ______ wrap around it and _____ are formed

Internodal segments

myelin-covered segments from node to node

Initial segment

section of nerve between axon hillock and first glial cell

Trigger

the axon hillock + initial segment is known as the ______ zone

Axon aka trigger zone

Myelinated

_________ axon protects and insulates axons from one another, speeds transmission, functions in repair of axons. White matter

Unmyelinated

______ axons are not wrapped around the axon; gray matter

Myelinated

White matter = _____ axons

Unmyelinated

Gray matter = _______ axons

Diameter and myelination

The speed of a nerve signal depends on two things: _______ and ________

More

Larger fibers have (more/less) surface area

Quickly

Myelination should happen slowly/quickly

unmyelinated

Digestion is an example of myelinated/Unmyelinated

Yes

Soma must be intact and some neurilemma remains

Is regeneration possible in the PNS? How?

Atrophy, degeneration in the distal end

An injured peripheral nerve presents with

1. Healthy neuron and muscle fibers are normal.

2. Nerve injury causes distal axon and Schwann cell degeneration; macrophages clear debris.

3. Soma swells and axon sprouts form; denervated muscles atrophy.

4. Schwann cells create a regeneration tube that guides one axon sprout.

5. The axon reconnects with target cells and restores synapses.

6. Neuron and muscle fibers recover toward normal structure and function.

Describe the steps of regeneration of a nerve fiber

Action potentials

Cells produce electrical signals called ________

Electrical potentials

___________ are different concentrations of charged particles in different parts of the cell.. This can produce a current!

Electrical current

_______ is a flow of charged particles from one point to another within the cell

-70mV

What is the resting membrane potential of a cell

Neural

____________ communication is based on electrophysiology - cellular mechanisms for producing electrical potentials and currents.

Unequal, RMP

_________ electrolyte distribution between ECF/ICF creates ______.

1. Diffusion of ions down their concentration gradients

2. Selective permeability of plasma membrane

3. Electrical attraction of cations and anions

Resting membrane potential results from combined effects of which 3 factors

Sodium

The orange channel is the sodium/potassium channel

Potassium

The blue channel is the sodium/potassium channel

potassium

The plasma membrane is very permeable to ______

Less

The plasma membrane is ______ permeable to sodium

no action potential is being generated

the neuron is waiting for stimulation

When does the resting membrane potential occur?

Local potential

A ____________ is a small, short-distance change in membrane potential that occurs when a neuron or muscle cell is stimulated.

Local

________ potentials are graded

Local, potassium

________ potentials are reversible because ______ leaks out of the cell

Local potential

The more sodium the enters the cell....the larger the ________

Positive, negative

Local potentials can make a resting membrane more _______ or more _______

Action

A ________ potential is a more dramatic change in the plasma membrane produced where there is a high density of voltage-gated ion channels.

1. Voltage gated sodium channels open

2. Sodium enters -> depolarization

3. Potassium gates fully open

4. Potassium leaves->repolarization

If a threshold potential of -55mV is reached what will happen?

Repolarization

(depolarization/repolarization) makes the inside of a cell more negative

Depolarization

(depolarization/repolarization) makes the inside of a cell more positive

Local potential

Purple box

Depolarization

Gray box

Repolarization

Turquoise box

Threshold

Pink box

Action

________ potentials are all or nothing

Afterpotential

Green box

Local

_______ potentials are produced by gated channels on dendrites and soma

Local

________ potentials may be positive or negative voltage changes

Local

________ potentials are graded

Local

_______ potentials are reversible and return to RMP if stimulation ceases before threshold is reached

Local

_______ potential has effects for only a short distance

Local

________ potentials have signals that grow weaker with distance

Action

________ potentials are produced by voltage gated channels on teh trigger zone and axon

Action

_______ potentials always begin with depolarization

Irreversible

Action potentials are (reversible/irreversible)

Action

________ potentials are self-propogating

Action

_________ potentials have effects of great distances

Sodium, potassium, closed

In resting membrane potential, voltage gated ______ and _____ are (open/closed)

Sodium, Open

Voltage gated (sodium/potassium) channels are (open/closed) in depolarization

Potassium, open

Voltage gated (sodium/potassium) channels are (open/closed) in repolarization

Refractory period

The period of resistance to restimulation is the __________

Absolute refractory period, relative refractory period

What are the 2 stages of the refractory period?

Absolute

(Absolute/relative refractory period) involves NO stimulus of ANY strength can trigger a new AP

Relative

(Absolute/relative refractory period) involves an unusually strong stimulus COULD trigger an AP, but this is unlikely

Unmyelinated

An (unmyelinated/myelinated) fiber has voltage-gated channels along its entire length.