AP Chapter 11 Final

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-Schematic of levels of nervous system organization -Neuroglia -Neuron Structure -Structural & Functional classification
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College: First year
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1

4 types of neuroglia in the CNS

-Astrocytes
-Microglial cells
-Ependymal cells
-Oligodendrocytes

2

2 types of neuroglia in the PNS

-Satellite cells
-Schwann cells

3

-Most abundant, versatile, and highly branched glial cells
-Cling to neurons, synaptic endings, and capillaries

Astrocytes(CNS)

4

Functions of the Astrocytes

-Supports and brace neurons
-Guide migration of young neurons
-Control chemical environment around neurons

5

Microgial Cells(CNS)

-Small, ovoid cells w/ thorny processes that touch and monitor neurons
-Clean up cells
-Migrate toward injured neurons
-Can transform to phagocytize microorganisms and neuronal debris

6

Ependymal Cells (CNS)

-Line the central cavities of the brain and spinal column
-Form permeable barrier between cerebrospinal fluid in cavities an tissue fluid bathing CNS cells fluid

7

Oligodendrocytes (CNS)

-Branched cells
-Processes wrap CNS nerve fibers, forming insulating myelin sheaths thicker nerve fibers

8

Satellite Cells (PNS)

-Surround neuron cell bodies in PNS
-Function similar to astrocytes of CNS

9

Schwann Cells (PNS)

-Surround all peripheral nerve fibers and form myelin sheaths in thicker nerve fibers
.Similar function as oligodendrocytes
-Vital to regeneration of damaged peripheral nerve fibers

10

Neuron Structure

-Units of nervous system
-Large, highly specialized cells that conduct impulses
-Extreme longevity
-Amitotic (can't repair)
-High metabolic rate- requires continuous supply of oxygen and glucose
-All have cell body and 1 or more processes

11

Structural Classification of Neurons
-Grouped by number of processes
-3 Types

-Multipolar- 3 or more processes
. 1 axon, other dendrites
. most common; major neuron in CNS
-Bipolar- 2 or more processes
. 1 axon and 1 dendrite
. rare
-Unipolor- 1 short process
. Divides T-like- both branches now considered axons
-Distal (peripheral) process
-Proximal (central) process

12

Dendrites- take information in

-In motor neurons
-Receptive(input)region of neuron
-Convey incoming messages toward cell body as GRADED POTENTIALS (short distance signals)

13

Membrane Potentials

-Neurons are highly irritable
-Respond to adequate stimulus by generation an ACTION POTENTIAL (nerve impulse)

14

Graded Potentials

-Short lived, localized changes in membrane potential
-Either depolarization or hyperpolarization
-Triggered by stimulus that opens gated ion channels
-Current flows but dissipates quickly and decays

15

Action Potentials (AP)

-Principle way neurons end signals
-Principal means of long distance neural communication
-Occur only in muscle cells and axons of neurons
-Brief reversal of membrane potential
-Do not decay over distance as graded potentials do

16

Absolute Refractory Period

-When voltage-gated Na+ channels open neuron cannot respond to another stimulus
-Time from opening of Na+ channels until resetting of the channels
-Ensures that each AP is an all or none event -Enforces one way transmission of nerve impulses

17

Relative Refractory Period

-most Na+ channels have returned to their resting state
-Some K+ channels still open
-Repolarization is occurring
-Threshold for AP generation is elevated
-Inside of membrane more negative than resting state
-Only exceptionally strong stimulus could stimulate an AP

18

Electrical Synapses

-Less common than chemical synapses
-Neurons electrically coupled (joined by gap junctions that connect cytoplasm of adjacent neurons)
.Communication very rapid
. May be unidirectional or bidirectional
.Synchronize activity
-More abundant in:
.Embryonic nervous tissue
-Nerve impulse remains electrical

19

Chemical Synapses

-Specialized for release and reception of chemical neurotransmitters
-Typically composed of 2 parts
-Axon terminal or presynaptic neuron
-Neurotransmitter receptor region on postsynapitc neuron's membrane
-2 parts separated by synaptic cleft
-Electrical impulse changed to chemical across synapse, then back into electrical

20

Postsynaptic Potentials

-Neurotransmitter receptors cause graded potentials that vary in strength w/
-Amount of neurotransmitter stays in area

21

Postsynaptic Potentials

-Types of postsynaptic potentials
-EPSP- excitatory postsynaptic potentials
-IPSP- inhibitory postsynaptic potentials

22

Excitatory Synapses and EPSPs

-Neuotransmitter binding opens chemically gated channels
-Na+ influx greater than K+ efflux-> net depoarization called EPSP (not AP)
-EPSP help trigger AP if EPSP is of threshold strength

23

Inhibitory Synapses and IPSPs

-Reduces postsynaptic neuron's ability to produce and action potential
-Makes membrane more permeable to K+ or Cl-
-Therefore neurotransmitter hyperpoloarizes cell

24

6 Neurottransmitters

-Acetylcholine
-Biogenic amines
-Amino acids
-Peptides
-Purines
-Gases and lipids-gasotransmitters

25

Acetylcholine(ACh)

...