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Lecture 05, 06 Sept 2005Chapters 10 and 11

Vertebrate PhysiologyECOL 437 (aka MCB 437, VetSci 437)

University of ArizonaFall 2005

instr: Kevin Boninet.a.: Kristen Potter

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1. Nervous System Introduction

Vertebrate Physiology 437

Chapter 10

Chapter 11

2. Neurons

p. 214, Silverthorn2001. 2nd ed. Human Physiology. Prentice Hall

synapse

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Good morning,This is a reminder that Dr. Herman Gordan (UA Associate Professor, Cell Biologyand Anatomy) will speak at Doings this Friday Sept 9th at 4pm (Gould-Simpson 601).The title of his presentation is:

"Self-organization of transmembrane kinases in synaptogenesis"

Hope to see you there.

Fiona Bailey______________________________________________________________________________

E. Fiona Bailey Ph.D., Research Assistant Professor, Department of Physiology,College of Medicine, The University of Arizona. Tucson AZ, USA.Phone: (520)626-8299. Fax: (520)621-8170

http://www.physiology.arizona.edu/labs/rnlab/fiona%20page.htm

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Nervous System

- Neurons / Nerve Cells- Glial Cells (support)

- Signalling via combinationof Electrical and Chemical

- Integrate informationAFFERENT

Comprises

- Coordinate ResponseEFFERENT

5-2 Randall et al. 2002

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Effectors respond to directives from NS(muscles, glands, target cells in organs)

Nervous System (NS) INTEGRATES information

Interneurons communicate between 2 neurons

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How does the endocrine system differ?

•Hormones•Broadcast•Ductless glands (not exocrine)•Much longer time scale, more widespread response

Neurosecretory CellsNeurohormones

ParacrineAutocrine

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7Hill et al. 2004, Fig 10.2

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Organization of the Nervous System

Three main functions:1. Sensory Reception2. Central Processing3. Motor Output

Divided into CNS and PNSA. CNS = Central Nervous System

B. PNS = Peripheral Nervous System

- Brain and Spinal Cord(and eyes and interneurons)

- most sensory and motor axons

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9Hill et al. 2004, Fig 10.7

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Flow of Information

Very Simplee.g., Sensing Effectors

Simple Interneurons

Afferent Signal -> CNS -> Efferent Signal -> Response

Monosynaptic Polysynaptic

8-2 Randall et al. 2002

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Sensing Effectors

Sensors with Afferent and Efferent Properties/Homeostasis

e.g., osmolarity and antidiuretic hormone (ADH)

8-2 Randall et al. 2002

P.279 Randall et al. 2002

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Convergence

Divergence

Parallel Processing

Flow of Information

- Multitask- As opposed to sequential

- Allow comparison of information, integration etc.

- Send same signal to several parts of CNS

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- Based on the neuron

- Group neurons into CNS

- New structures added on to old (not replaced)

Evolution of Nervous System:

- Size of CNS region correlated with importance

- Elaboration of Reflex Arc

- More neurons in complex organisms

- Topological Maps

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CNS - Spinal Cord- Retains evidence ofsegmented ancestors

8-7 Randall et al. 2002

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CNS - Spinal Cord- Anatomy

White matter = myelinGray matter = somata

and dendrites

Cerebrospinal Fluid in spinal canal

Dorsal root, horn = ~afferent

Ventral root, horn = ~efferent

Spinal Reflexes: - locomotion / walking- chicken w/o head

Dorsal Root Ganglion (PNS)- afferent sensory somata

8-8 Randall et al. 2002

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CNS - Brain

Vertebrate bilaterally paired nerve connections to periphery

Sensory

Motor

Both

8-9 Randall et al. 2002

cerebrum

tectumcer

ebellu

m

pituitary

olfactory

optic

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17Hill et al. 2004, Fig 10.8

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CNS - Brain Anatomy

-Medulla oblongataRespiration, autonomic funct, some sensory (hearing, equil.)

-Cerebellum Coordinate motor outputIntegrates info. from proprioceptors (stretch and joint)

visual, auditoryMore convoluted ( ⇑ s.a.) in higher groups

-Pons (and tectum)

Birds with large cerebellum to handle 3D flight

Integrate and communicateVisual, tactile, auditory maps~ body movement coordination in some groups

-Cerebral CortexIn higher groups takes over function of tectum

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CNS - Brain Anatomy (con’t)

-ThalamusSensory and motor coordination

-AmygdalaProcesses info. and output related to emotions

-HypothalamusAlso involved in emotions

Often communicates with cerebral cortex

Body temp, eating, drinking, sexWater and electrolyte balance

-Olfactory BulbKey sense in many vertebrate groupsAnterior position

-Cerebrum (covered by cerebral cortex)More evolved in higher groups (size and folds)...

Olfacti

on st

raigh

t to

cerebr

um w

/o goin

g

thro

ugh t

halam

us

(in m

ammals

)

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CNS - Brain

Note change in size in difft. groups

8-10 Randall et al. 2002

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CNS - Brain

Note change in size in difft. groups

8-10 Randall et al. 2002

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Cerebrum and Cerebral Cortex

CNS - Brain

- Folds increase surface area and # neurons- Functional Regions

1. Sensory cortex

2. Motor cortex

3. Association cortex- memory, future, thought, communication

- somatosensory, auditory, visual- sensory homunculus (“little man”)

- often similar to sensory cortex map

Relative importance of each region changes among vertebrate groups

Size o

f

rece

ptive

fields

?

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23Relative decrease

Relative increase

Increase then decrease?

8-13 Randall et al. 2002

24Hill et al. 2004, Fig 10.9

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Cortical Maps

More neurons to make precise movements

Plasticit

y!?

8-15 Randall et al. 2002

1/2 face and hands

Teeth, whiskers … claws

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CNS

- Interneurons

Structural and Functional Regions

Tracts = bundles of axons from nuclei

- Most neuronal somata

Nuclei = collections of somata w/ similar function

PNS

incl. motor neurons

Nerves = axon bundles from sensory + motor neuronsGanglia = somata of some autonomic neurons and

most sensory neurons

- Nervous system outside CNS

Nerve usually with both Afferent and Efferent axons

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Structural and Functional Regions

- Efferent NS1. Somatic/Voluntary

-skeletal muscle

2. Autonomic- smooth muscle- cardiac muscle- glands- ”housekeeping”A. Sympathetic

~ fight or flight

B. Parasympathetic~ rest and digest

8-6 Randall et al. 2002

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Sympathetic

Para-sympathetic

8-18 Randall et al. 2002

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Autonomic NS (vs Voluntary/Somatic)

A. Sympathetic (f or f)B. Parasympathetic (r + d)

Antagonistic Groups in Balance:

Both function via reflex arcs, but often opposite effectsEfferent signal with two neurons:1. Preganglionic (NT released is Acetylcholine [Ach])

2. Postganglionic (PNS, receptor is nicotinic ACh)

Difference between Symp. and Para. is in:1. Location of postganglionic somata2. Postganglionic NT 3. Receptors on target tissues

-Muscle reflexes in spinal cord, autonomic to brain

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Autonomic NS

1-Postganglionicsomata nearer CNSin chain ganglia

Sympathetic Parasympathetic1-Postganglionic

somata near effector,or in effector organ

2-Postganglionic NTis Norepinephrine

2- Postganglionic NTis ACh

3-Effector receptoris alpha or betaadrenergic

3-Effector receptor ismuscarinic ACh

Difference between Symp. and Para. is in:1. Location of postganglionic somata2. Postganglionic NT 3. Receptors on target tissues

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31Hill et al. 2004, Fig 10.12

32Hill et al. 2004, Fig 10.13

Norepinephrine

Acetylcholine

Know a couple of examples:

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33Hill et al. 2004, Fig 10.13

Know a couple

of examples:

Norepinephrine

Acetylcholine

34Hill et al. 2004

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Biological Clocks later if we have time(Hill et al. pages 274-280)

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“Squid axons are important to physiologists, and to the squid.”Hill et al. 2004, p.281

Sir Alan Hodgkin, Nobel Prize 1963

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Neurons:

Hill et al. 2004, Fig 11.1

38Hill et al. 2004, Fig 11.2

1.PNS

2.CNS

3.Metabolic support

4.Phagocytes/immune

4 types of Glial Cells

Outnumber neurons 10:1 in mammalian brain

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Osmotic Properties of Cells and Relative Ion Concentrations

Na+Na+ K+K+

Cl-Cl-

4-12 Randall et al. 2002

Ca+

Ca+

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Movement Across Membranes

Electrochemical Gradient

Concentration gradient

Electrical gradient

Electrochemical equilibrium

Equilibrium potential (Ex in mV)

Na+Na+

--

--

-

-

-

-

-

-

-

++

+

+

+

+

+

+

++

++

K+K+

--

--

-

-

-

-

-

-

-

++

+

+

+

+

+

+

++

++

when [X] gradient = electrical gradient

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Equilibrium potential (Ex in mV)

“Every ion’s goal in life is to make the membrane potential equal its own equilibrium potential (Ex in mV)”

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To change Vm, A Small Number of Ions Actually MoveRelative to the Number Present both

Inside and Outside the cell

The concentration gradients are not abolishedWhen the channels for an ion species open

Gradients allow for ‘work’ to be done, e.g., action potential sends signal along axon

-Gradient established by pumps (ATP)

Membrane Potential

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Membrane Potential

- Driven by ions that are permeable to the membrane (and have different [ ]in as compared to [ ]out a.k.a. gradient created with ATP)

- emf determines which direction a given ion (X) will move when the membrane potential is known

- Equilibrium Potential (Ex in mV):~The equilibrium potentials of all the permeableions (a function of their established gradients) will determine the membrane potential of a cell

emfx = Vm - Ex

- K+ for example

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Membrane Potential

- Resting Membrane Potential driven by K+ efflux and,to a lesser extent, Na+ influx

- Na+/K+ ATPase pump generates gradients that, for these permeable ions, determinemembrane potential

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Nernst equation: E = lnRTzF

CoutCin

whereE = equilibrium membrane potentialR = gas constantT = absolute temperaturez = valenceF = Faraday’s constant

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Equilibrium Potential

- Calculate for a given type of ion using thesimplified Nernst Equation:

0.058 [X]outEx = log z [X]in

0.058 [Na+]outENa= log z [Na+]in

0.058 120 mMENa= log1 10 mM

= 63 mV (0.063 V)

remember Equilibrium potential (Ex in mV)when [X] gradient = electrical gradient

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Osmotic Properties of Cells and Relative Ion Concentrations

Na+Na+ K+K+

Cl-Cl-

4-12 Randall et al. 2002

Ca+

Ca+Donnan Equilibrium?

Goldman Equation?

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Membrane Potential - Nernst for single ion

- Goldman equation for multiple ions

Vm = Ex if only one ion ‘driving’

5-14 Randall et al. 2002

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49Hill et al. 2004, Fig 11.4

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Hill et al. 2004, Fig 11.5a,b

Current from + to –(follow cations)

Tau = time constant(2 - 20 ms)(time to reach 63% max)

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channels

membrane bilayer

Hill et al. 2004, Fig 11.5c

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Hill et al. 2004, Fig 11.6a,b

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Hill et al. 2004, Fig 11.6c

Lambda = length constant(distance at which 37% voltage change)

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conductance = reciprocal of resistance

Membrane Potentials and Electricity

vs.capacitance

5-10 Randall et al. 2002deltaV = IRChange in Voltage = current x resistance

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Mid-Lecture Question

Calculate EK if[K+]inside = 140 mM[K+]outside = 2.5 mM

If the resting membrane potential is –60 mV, which way will K+ ‘want’ to move (in or out of the cell)?

Which way will Na+ want to move?

Which way will K+ want to move if membrane potential is -110 mV? 30 mV?

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Calculate EK if[K+]inside = 140 mM[K+]outside = 2.5 mM

If the resting membrane potential is –60 mV, which way will K+ ‘want’ to move (in or out of the cell)?

Which way will Na+ want to move?

Which way will K+ want to move if membrane potential is -110 mV? 30 mV?

OUT

IN

IN OUT

-101 mV

Mid-Lecture Question

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Randall et al. 2002