chapter 11: nervous system basics and nervous system tissues

Chapter 11:Nervous System Basics and

Nervous System Tissues

Santiago Ramon Y. Cajal (1852-1934)Founding Scientist in the Modern Approach toNeuroscience. Received Nobel Prize in 1906

Human Anatomy and Physiology, 7eby Elaine Marieb & Katja Hoehn

Copyright © 2007 Pearson Education, Inc.,publishing as Benjamin Cummings.

Figure 11.1: The nervous system’s functions, p. 388.

Sensory input

Motor output

Integration



Figure 11.2: Levels of organization in the nervous system, p. 389.

Central nervous system (CNS) Brain and spinal cord Integrative and control centers

Sensory (afferent) division Somatic and visceral sensory nerve fibers Conducts impulses from receptors to the CNS

Motor (efferent) division Motor nerve fibers Conducts impulses from the CNS to effectors (muscles and glands)

Autonomic nervous system (ANS) Visceral motor (involuntary) Conducts impulses from the CNS to cardiac muscles, smooth muscles, and glands

Sympathetic division Mobilizes body systems during activity

Parasympathetic division Conserves energy Promotes housekeeping functions during rest

Peripheral nervous system (PNS) Cranial nerves and spinal nerves Communication lines between the CNS and the rest of the body

Somatic nervous System Somatic motor (voluntary) Conducts impulses from the CNS to skeletal muscles

= Structure= Function

Key:

Centralnervoussystem(CNS)

= Sensory (afferent)division of PNS= Motor (efferent)division of PNS

Key: Brain

SpinalcordSkin

Visceral organ

Skeletalmuscle

Peripheral nervous system(PNS)

Motor fiber ofsomatic nervoussystem

Somatic sensoryfiber

Sympatheticmotor fiber of ANS

Parasympatheticmotor fiber of ANS

Visceralsensory fiber

(a)

(b)



Figure 11.3: Neuroglia, p. 390.

(a) Astrocyte

(d) Oligodendrocyte

(e) Sensory neuron with Schwann cells and satellite cells

(b) Microglial cell

(c) Ependymal cells

Schwann cells(forming myelin sheath)

Cell bodyof neuronSatellite cells

Nerve fiber

Capillary

Neuron

Nerve fibers

Myelin sheath

Process ofoligodendrocyte

Fluid-filled cavity

Brain or spinal cord tissue



Figure 11.4: Structure of a motor neuron, p. 392.

(b)

(a)

Dendrites(receptiveregions)

Cell body(biosynthetic centerand receptive region)

Nucleolus

Nucleus

Terminal branches(telodendria)

Nissl bodies

Axon(impulse generatingand conductingregion)

Axon terminals(secretorycomponent)

Axon hillock

Neurilemma(sheath ofSchwann)

Node of Ranvier

Impulsedirection

Schwann cell(one inter-node)

Neuron cell body

Dendriticspine



Figure 11.5: Relationship of Schwann cells to axons in the PNS, p. 394.

(a)

(b)

(c)

(d)

Schwann cellcytoplasm

Axon

NeurilemmaMyelinsheath

Schwann cellnucleus

Schwanncell plasmamembrane

Myelin sheath

Schwann cellcytoplasm

Neurilemma

Axon



Figure 11.6: Operation of gated channels, p. 398.

(a) Chemically gated ion channel

Na+

K+K+

Na+

(b) Voltage-gated ion channel

Na+

Na+

Receptor

Neurotransmitter chemical attached to receptor

Closed Open

Membranevoltagechanges

Closed Open

Chemicalbinds



Figure 11.7: Measuring membrane potential in neurons, p. 399.

Voltmeter

Microelectrodeinside cell

Plasmamembrane

Ground electrodeoutside cell

Neuron

Axon



Figure 11.8: The basis of the resting membrane potential, p. 399.

Na+ Na+

K+

K+

K+

K+

Na+

Na+

Na+

Na+

Cell interiorNa+

15 mMK+

150 mMCl–

10 mM A–

100 mMNa+

150 mMA–

0.2 mM

Cell exterior

K+

5 mM Cl–

120 mM

Cellexterior

Cellinterior

Plasmamembrane

Na+–K+

pumpDif

fusi

on

K+ N

a+D

iffus

ion

-70 mV



Figure 11.9: Depolarization and hyperpolarization of the membrane, p. 400.

Depolarizing stimulus

Mem

bra

ne

po

ten

tial

(vo

ltag

e, m

V)

Time (ms)

0–100

–70

0

–50 –50

+50

1 2 3 4 5 6 7

Hyperpolarizing stimulus

Mem

bra

ne

po

ten

tial

(vo

ltag

e, m

V)

Time (ms)

0 1 2 3 4 5 6 7–100

–70

0

+50

Insidepositive

Insidenegative

(a) (b)

Restingpotential

DepolarizationRestingpotential

Hyper-polarization



Figure 11.10: The mechanism of a graded potential, p. 401.

(b)

Depolarized region Stimulus

Plasmamembrane

Depolarization Spread of depolarization(a)



Figure 11.11: Changes in membrane potential produced by a depolarizing graded potential, p. 402.

Distance (a few mm)

–70Resting potential

Active area(site of initialdepolarization)

Mem

bra

ne

po

ten

tial

(m

V)



Figure 11.12: Phases of the action potential and the role of voltage-gated ion channels, p. 403.

0 1 2 3 4

–70

–55

0

+30

Me

mb

ran

e p

ote

nti

al

(mV

)

Time (ms)

Re

lati

ve

me

mb

ran

e

pe

rme

ab

ilit

y

Na+Na+

K+

K+

Outsidecell

Insidecell

Outsidecell

Insidecell

Depolarizing phase: Na+

channels open

Repolarizing phase: Na+

channels inactivating, K+

channels open

Action potential

PNa

PKThreshold

Na+

Na+

K+K+

Outside cell

Insidecell

Outsidecell

Insidecell

Inactivation gate

Activationgates

Potassiumchannel

Sodiumchannel

Resting state: All gated Na+

and K+ channels closed (Na+ activation gates closed; inactivation gates open)

Hyperpolarization: K+

channels remain open; Na+ channels resetting

2

2

3

4

4

1

11



Figure 11.13: Propagation of an action potential (AP), p. 405.

–70

+30

(a) Time = 0 ms (b) Time = 2 ms (c) Time = 4 ms

Voltageat 2 ms

Voltageat 4 ms

Voltageat 0 ms

Resting potential

Peak of action potential

Hyperpolarization

Mem

bra

ne

po

ten

tial

(m

V))



Figure 11.14: Relationship between stimulus strength and action potential frequency, p. 406.

Time (ms)

Vo

ltag

eM

emb

ran

e p

ote

nti

al (

mV

)

–70

0

+30

Threshold

Actionpotentials

Stimulusamplitude



Figure 11.15: Refractory periods in an AP, p. 406.

Stimulus

Mem

bra

ne

po

ten

tial

(m

V)

Time (ms)

–70

0

+30

0 1 2 3 4 5

Absolute refractoryperiod

Relative refractoryperiod

Depolarization(Na+ enters)

Repolarization(K+ leaves)

After-hyperpolarization



Figure 11.16: Saltatory conduction in a myelinated axon, p. 407.

Node of Ranvier

Cell bodyMyelinsheath

Distalaxon



Figure 11.17: Synapses, p. 409.

(a)

(b)

Cell body

Dendrites

Axon

Axodendriticsynapses

Axoaxonicsynapses

Axosomaticsynapses

Axosomaticsynapses

Soma of postsynaptic neuron

Axon



Figure 11.18: Events at a chemical synapse in response to depolarization, p. 410.

Synaptic vesiclescontaining neurotransmitter molecules

Axon of presynapticneuron

Synapticcleft

Ion channel(closed)

Ion channel (open)

Axon terminal of presynaptic neuron

PostsynapticmembraneMitochondrion

Ion channel closed

Ion channel open

Neurotransmitter

Receptor

Postsynapticmembrane

Degradedneurotransmitter

Na+

Na+

Ca2+

Action P

otential

1

2

34

5



Figure 11.19: Postsynaptic potentials, p. 412.

Threshold

Mem

bra

ne

po

ten

tial

(m

V)

Time (ms)

+30

0

–70

–55

10 20

(a) Excitatory postsynaptic potential (EPSP)

Threshold

Mem

bra

ne

po

ten

tial

(m

V)

Time (ms)

+30

0

–70

–55

10 20

(b) Inhibitory postsynaptic potential (IPSP)



Figure 11.24: Types of circuits in neuronal pools, p. 422.

(a) Divergence in same pathway

(e) Reverberating circuit

(f) Parallel after-discharge circuit

(b) Divergence to multiple pathways

(c) Convergence, multiple sources

(d) Convergence, single source

Input Input

Output Output

Input

OutputInput

Output

Input 1

Input 2 Input 3

Output

OutputInput



Figure 11.25: A simple reflex arc, p. 423.

Stimulus

Response

Receptor

Effector

Sensory neuron

Motor neuron

Integrationcenter

Spinal cord (CNS)

Interneuron

chapter 11: nervous system basics and nervous system tissues

Documents

pearson education

benjamin cummings

nervous system basics

nervous systems functions

motor neuron

visceral sensory nerve

glandssympathetic division

effectors muscles