1. nervous system and neurons (chap 10&11)

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Lecture 05, 05 Sept 2006

Vertebrate PhysiologyECOL 437 (MCB/VetSci 437)

Univ. of Arizona, Fall 2006

Kevin Bonine & Kevin Oh

1. Nervous Systemand Neurons(Chap 10&11)

http://eebweb.arizona.edu/eeb_course_websites.htm

5-2 Randall et al. 2002

(endocrine system later)

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Wanted to give you a heads up for our next Doings on Sept 15th led by Doug Stuart (UofA, Regents' Professor Emeritus of Physiology ). Doug will be giving us an update of the Physiology seminar he gave at the end of last

spring.

Title: Historical reflections on the term "motor homunculus".

Doings meets in 601 Gould-Simpson, 4:00-5:00.

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Housekeeping, 05 September 2006

Upcoming Readings

today: Textbook, chapter 10 & 11

Wed 06 Sept: Tipsmark et al. 2002, bring problem set to doThurs 07 Sept: Textbook, chapter 10 &11Tues 12 Sept: Textbook chapter 11 & 12

Lab oral presentations 06 Sept9am – Nilam Patel2pm – Nick Brown

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Wed 06 Sept: Tipsmark et al. 2002

Kevin Oh will help with short glossary

Integrative

Good example of using multiple tools to addressinteresting physiological question

Filter the useful information from the unnecessary details

What other questions does this paper raise?

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Nervous System

- Neurons / Nerve Cells- Glial Cells (support)

- Signalling via combinationof Electrical and Chemical

- Integrate informationAFFERENT

Comprises

- Coordinate ResponseEFFERENT


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Organization of the Nervous System

Three main functions:1. Sensory Reception (converts environmental stimulus to elect/chem)

2. 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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7Hill 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


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Sensing Effectors

Sensors with Afferent and Efferent Properties/Homeostasis

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


P.279 Randall et al. 2002

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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


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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


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CNS - Brain

Vertebrate bilaterally paired nerve connections to periphery

Sensory

Motor

Both


cerebrum

tectumcer

ebellu

m

pituitary

olfactory

optic

14Hill 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


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CNS - Brain

Note change in size in difft. groups


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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

?

20Hill et al. 2004, Fig 10.9

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Cortical Maps(Hill et al. Fig 10.11)

More neurons to make precise movements

Plasticit

y!?


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


33C. Enteric

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Sympathetic

Para-sympathetic


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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. CNS origin2. Location of postganglionic somata3. Postganglionic NT 4. Receptors on target tissues

-Muscle reflexes in spinal cord, autonomic to brain

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Autonomic NS

2-Postganglionicsomata nearer CNSin chain ganglia

Sympathetic Parasympathetic2-Postganglionic

somata near effector,or in effector organ

3- Postganglionic NTis Norepinephrine

3- Postganglionic NTis ACh

4-Effector receptoris alpha or betaadrenergic

4-Effector receptor ismuscarinic ACh

Difference between Symp. and Para. is in:1. CNS origin2. Location of postganglionic somata3. Postganglionic NT 4. Receptors on target tissues

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27Hill et al. 2004, Fig 10.12

28Hill et al. 2004, Fig 10.13

Norepinephrine

Acetylcholine

Know a couple of examples:

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29Hill et al. 2004, Fig 10.13

Know a couple

of examples:

Norepinephrine

Acetylcholine

(chain ganglia)

30Hill et al. 2004

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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

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33Hill 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-


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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Na+Na+ K+K+

Cl-Cl-

Permeabilities

K+ >> Na+ ; Cl-

A- (includes proteins, phosphate groups, etc.)


Ca+

Ca+

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- outside is zero by convention

Membrane Potential (Vm in volts or mV)

K+, Na+- Vrestabout -60 mV

At Rest


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Nernst equation: E = lnRTzF

CoutCin

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

(Mistake in Hill et al. text bottom of page 291; see if you can fix it)

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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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Na+Na+ K+K+

Cl-Cl-


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’


46Hill et al. 2004, Fig 11.4

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channels

membrane bilayer

Hill et al. 2004, Fig 11.5c

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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

1. nervous system and neurons (chap 10&11)

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