Neurobiology, Physiology, and Behavior

8/13/2019 Neurobiology, Physiology, and Behavior

1/22

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yesterday


2/22

a) whatthe nervous system responds to

b) how it regulates tissues and organ systems(skeletal muscle, cardiac muscle, digestivesystem...)

nervous system 13 days, 50 min/ea... essentially one 11-hr lectureprimary interests are...

therefore, learn ...a) structural organizationb) signal generationc) signal propagationd) electricalresponses

Fig 5-1

note errors:1) retina is CNS2) motoneurons are CNS

stimuli receptor (i.e., responsive) cells

light photoreceptors in retina

muscle stretch stretch receptors in muscle

muscle/tendon tension tension receptors within tendons

sound, linear/rotational acceleration hair cells in 3 parts of inner ear

sweet, bitter, sour, salt taste receptors in tongue

blood plasma osmolarity osmoreceptors in hypothalamus

change in blood pressure baroreceptors e.g, aortic archstretch, peptides, fat, pH, osmolarity receptors in small intestine

touch, temperature, pain receptors in skin

what does the nervous system respond to?

note: the specificity of these responses imply these

cells are structurally and/or biophysically specialized.

we will mention ~10 different types of receptor cells.

in several cases, the mechanisms are not known.


3/22

in the absence of stimuli, cells are said to be at rest

in the presence of appropriate stimuli, they might respond

light

dark

add chemical

remove chemical

relax

stretch

at rest

resting

stretch receptor

chemoreceptor

photoreceptor

stimulated

activated

responding

Fig 5-1

what pathways do these signals activate? see 2 anatomical divisions


4/22

afferentneurons

afferent neurons send signals toward

the spinal cord, toward the brain, or tohigher levels within the CNS

1) from the periphery toward the spinal cord2) toward the brain (from the periphery & spinal cord)3) from lower to higher levels of the spinal cord4) from lower to higher levels of the brain

Fig 5-1

efferent neuronssend signals awayfrom the spinal

cord or the brain

efferentneurons

1) from higher to lowerlevels of the brain

2) away from the brain (tocells in the head & spinal cord)

3) from higher to lowerlevels of the spinal cord

4) away from the spinalcord (to the periphery)

Fig 5-1


5/22

note:1) the afferent cells stimulated by specific stimuli are the receptor cells.2) single afferent cells can communicate directly with efferent cells.

3) or the afferent path can consist of a sequenceof several cells; theefferent path might also consist of several cells.

4) some cells send signals over long distances. these are anatomically& biophysically specialized so that signals travel quickly & reliably.

5) afferent & efferent signals typically travel only 1 direction cellshave a polarity.

afferenta.k.a.sensory receptor cell efferent

afferent efferentinterneuronsi.e. intervening

what happens along the afferent & efferent paths?

see 2 other divisions: central vsperipheral nervous systems

Fig 5-1


6/22

skull

vertebralcolumn

central nervous system

CNS

retina

spinal cord

brainskull earnose

tongue

spinal cord

brain

enteric NSpostganglionicfibers

vertebralcolumn

receptorssomaticvisceral

motoneuronspreganglionicfibers

1) entirely inside skull or entirely insidevertebral column

2) only the cell body within skull or vertebralcolumn

3) retina

1) receptor cells in ear, nose, tongue2) cell body or entire neuron outside of skull &

vertebral column

3) enteric - inside wall of digestive tract(especially, small intestine)

peripheral nervous system

PNS

cell bodydirection of

signal propagation

cell body

location!

to categorize neurons, check 2 properties:where is cell body?

which direction does signal travel?below, show this as:

skull

vertebralcolumn

AFFERENT

retina

brainskull earnose

tongue

spinal cord

brain

enteric NS

postganglionicfibers

vertebralcolumn

CNS PNS


motoneurons

spinal cordpreganglionicfibers

direction

of signal!

to categorize neurons, check 2 properties:where is cell body?which direction does signal travel?


7/22

skull

vertebralcolumn

retinabrain

skull earnosetongue

spinal cord

brain

enteric NSpostganglionicfibers


vertebralcolumn

EFFERENTCNS PNS

preganglionicfibers

motoneurons

spinal cord

direction

of signal!

directionof signal!

to categorize neurons, check 2 properties:where is cell body?

which direction does signal travel?

One way is to ask: What cells are present?

Then, how do individual cells work?

Then, how do groups of cells work together?

The human brain contains ~100 billion neurons.

The human spinal cord contains ~13.5 million neurons.

The digestive tract contains a similar number of neurons.

Each human retina contains > 100 million neurons.

How many cells are we considering?

This is not the only way to study the nervous system, but it

allows us to examine mechanisms.

retina

spinal

cord

brainhow can we understand this in detail?


8/22

how can we anatomically map & recognize these cells?

tremendous microscopy & mapping efforts

1) Ramon y Cajl (Nobel Prize, 1906)(http://nobelprize.org/nobel_prizes/medicine/articles/cajal/index.html)

2) Allen Brain Atlas (http://www.brainatlas.org/aba/)3) International Consortium for Brain Imaging

(www.Ioni.ucla.edu/ICBM)

4) National Center for Microscopy and ImagingResearch (http://www-ncmir.ucsd.edu/)

5) Brain Maps(http://www.brainmaps.org) an interactive zoomable high-resolution digital brain atlas, PI: CfN, UCD.

6) National Partnership for Advanced ComputationalInfrastructure (http://www.npaci.edu)

7) Brain Architecture Project (http://brainarchitecture.org/)


9/22

serial section reconstruction

F

ig5-1

Nature424:250,2003

Netter 06 Human Anatomy / Sherwood Fig 5-28

http://www.brainmaps.org

Deerinck07OlympusBioscapes

Ca

jal1894(perSotelo03

Na

tureReviewsNeurosci)

Weissman08NikonSmallWorldmossyfibersomata(dentateghrus)

CajalHistologieduSysteme

Nerveux

del'HommeetdesVertebre

tes.


10/22

induced expression of GFP

Kime

tal08Nature

Stradleighetal2011JCompNeurol

induced expression of YFP

Micheva&Smith07Neuron55:25


11/22

Deerinck07OlympusBioscapes

Cajal1894(perSotelo03

NatureReviewsNeurosci)

Weissman08NikonSmallWorldmoss

yfibersomata(dentateghrus)

CajalHistologieduSystemeNerveux

del'HommeetdesVertebretes.

connectometomography Smiths video

Micheva et al 10 Neuron 68: 639


12/22

what could we learn at a macroscopic scale?

morphological propertiesof cells

length how far do they reach?

diameter how easily can signals travel?

breadth how many cells can they communicate with?

numbers how many cells are devoted to specific functions(e.g. to detect light falling in a given area of space?)

differences inshape

cells that are identical in appearance are likely to befunctionally similar; cells that differ one way are likely

to differ both ways (anatomy & connections!interactions & functions)

connections are their parallel (i.e., separate) pathways from onelocation to another? (like lanes on a highway)

at this point, which properties are important?

location relative to skull & vertebrae

direction afferent vs efferent

typeneuron vs non-neuron; receptor cell vs interneuronvs long-distance spiking cell

polarity dendrites, axon, axon terminal

axon diameter major factor in the speed at which signals travel

connections

as few as 1-to-1 (e.g., in fovea of primate retina)

many-to-one -- convergence

one-to-many -- divergence


13/22

Fig 4-8

textbook image of polarity

a) the input end looks like tree branches: DENDRITESb) the output is at the end of a cylinder (axon): AXON TERMINAL

1) breadthrefers to the span from one side of the dendritic arborization tothe opposite side: this helps determine how many inputs a cell can

collect / integrate / compare / process

2) the axon is the part of cells specialized to allow signals to travel longdistances: this accounts for the length of neurons

breadth (whether thedendrites cover a broad

area or not)

Fig 4-8

diameter

input end

output

end

basic structural properties


14/22

example of polarity

1) to drive withdrawal reflex, signals travel in direction shown by arrows2) painful stimulus elicits signal at the sensory end of the receptor cell.3) this signal travels to the spinal cord, elicits response in small neurons

inside spinal cord.

4) these elicit response in motoneurons: signal starts at input end ofmotoneuron and travels to the output end (at the skeletal muscle).

Fig 5-31

3 basic cell types

receptor cells - transform stimulus energies into electrical signalsinterneurons - process signals locally, or regulate flow of information

spiking cells - generate spikes (action potentials)

receptor cell(some spike,

some dont)

interneurons

spiking command neuronsFig 5-31


15/22

1) in the absence of stimuli, they are at rest2) interneurons & spiking neurons respond to changes in the

release of chemicals (neurotransmitters) that transmit

information between neurons3) the change in release starts in the receptor cell, and the end

result is to elicit the appropriate response in the target tissue

stimulusrelease of chemical

(neurotransmitter)increases or decreases

interneuronresponse

neurotransmitter release

increases or decreases

spiking neuronresponse

responseneurotransmitter releaseincreases or decreases

receptor cellresponse

12

3

45

6

78

how do these cell types work as a group?

central higher brain

perceive, learn, remember,reason, choose, conceive,

emote

motor skeletal muscle

locomotionbreathing

chewingswallowing

posturesome reflexes

autonomic

cardiac muscle heart

smooth muscleblood vessels

iris

glandssweattears

enteric smooth muscle digestive tract

some neural outputs are voluntary & conscious

some are involuntary & subconscious


16/22

Central Nervous System(CNS)A.brain

1. forebrain

a. cerebral cortex

b. basal ganglia

c.thalamusd. limbic system

2. brainstem

a. midbrain

b. pons

c. medulla oblongata

3. cerebellum

a. cerebellar cortex

b. deep nuclei

B.spinal cord

1. sensory fibers in spinal cord2. motor

3. pre-ganglionic fibers

C. retina

Peripheral Nervous System(PNS)A.somaticsensory

B.autonomic:

1. sympathetic

2. parasympathetic

traditionally shown as efferent only,but notice their sensory inputs

C.enteric- both sensory & output

D. special sensory: ear, nose, tongue

E. visceralsensory

major parts of central & peripheral nervous systems

note: Sherwood (Fig 5-1 & Ch 6) does not include the retinaas a part of the CNS. This is an error. The retina develops

from neural plate like the brain and spinal cord, whereas thePNS arises from neural crest.

if time permits

= will be covered

now that we know the major parts...

1) what do nerve cells do?

2) how does this happen?


17/22

what does the nervous system do? Which cells do this?

eye, ear, nose, tongue (all face forward & are close to brain)brain (e.g., osmoreceptors)aorta (baroreceptors)

small intestine (pressure, pH, peptides, fat)skin (touch, pressure, pain)skeletal muscle (spindles)etc.

where does this happen?

1) transduce stimuli

2) process signals

3) produce involuntary responses

4) generate & control behavior

5) extract information & intellectual activity

transduction: converting one form of energy

into another. in the nervous system, this

ultimately generates electrical signals.

Fig 1-4

Ch 5, 6, 7

what does the nervous system do?1) transduce stimuli

2) process signals




eye, ear, nosebrain

spinal cord

processing: adding, subtracting, filtering,

amplifying, adaptationsignals: electrical events that report changes

in a stimulus that a cell is sensitive to

7thed: Fig 1-4

8thed: Fig 1-5

Ch 5, 6, 7


18/22

what does the nervous system do?


2) process signals




brainstemvarious centers (e.g., swallowing)

spinal cord

involuntary responses: a.k.a. reflexes

1) no conscious control (e.g. digestion)2) often no sensation (e.g. pupillary

constriction),but some exceptions (e.g.

sneezing & defecation)

3) typically stereotyped (events & speed)

7thed: Fig 1-4

8thed: Fig 1-5

Ch 5, 6, 7

what does the nervous system do?1) transduce stimuli

2) process signals




brain (e.g., motor cortex)cranial nerves (e.g., for chewing)

spinal cord (e.g., for moving limbs)

behavior: deliberate, controlled, sensed

e.g. moving head, jaw, torso, limbs, digits,walking, talking

7thed: Fig 1-4

8thed: Fig 1-5

Ch 5, 6, 7


19/22

what does the nervous system do?


2) process signals




brain

intellectualize:perceive, learn, remember,

reason, choose, conceive, emote

7thed: Fig 1-4

8thed: Fig 1-5

Ch 5, 6, 7

NPB 101 examines several examples of brain function

event involved in

activate cranial nerves

vision, hearing, taste, smell, salivation,

chewing, swallowing. also facialexpressions, eye movement,

sensations in face & scalp.

somatosensory cortex somatic sensations

efferent from motor cortex to spinal cord movement (e.g. locomotion)

activate melanopsin ganglion cells pupillary reflex (in eye)

baroreceptors activate medullary centeradjust heart rate, arterioles, peripheral

veins

release anti-diuretic hormone (ADH) reduce urine volume

activate osmoreceptorsmodulate activity of thirst center

modulate release of ADH

long (vago-vagal) reflexincrease gastrointestinal secretions &

motility

generate & control output of medullary

centers

control vegetative functions (e.g.,

swallowing, respiration)

release hypothalamic & pituitary hormonesfluid balance, blood pressure, growth,

metabolism, reproduction, birth

event involved in

activate cranial nerves

vision, hearing, taste, smell, salivation,

chewing, swallowing. also facialexpressions, eye movement,

sensations in face & scalp.

somatosensory cortex somatic sensations

efferent from motor cortex to spinal cord movement (e.g. locomotion)

activate melanopsin ganglion cells pupillary reflex (in eye)

baroreceptors activate medullary centeradjust heart rate, arterioles, peripheral

veins

release anti-diuretic hormone (ADH) reduce urine volume

activate osmoreceptorsmodulate activity of thirst center

modulate release of ADH

long (vago-vagal) reflexincrease gastrointestinal secretions &

motility

generate & control output of medullary

centers

control vegetative functions (e.g.,

swallowing, respiration)

release hypothalamic & pituitary hormonesfluid balance, blood pressure, growth,

metabolism, reproduction, birth


20/22

hmm would it be possible to examine even more brain functions?

1) consciousness2) higher vision (e.g. perception)3) generation of complex behaviors4) localization of sound5) memory, learning, other forms of plasticity& what about neurological & neurodegenerative diseases?

Scannell&Y

oung(1993)CurrBiol3:191

cerebral cortexvisual cortex

unlikely. here are hints of what wed need to examine.

in 2005, some likened our maps of the brain to 17thcentury maps of the world.

Gibbons1990Science

Thorpe2001Science

32 areas

extensive spatial interconnections

rapid signal processing &

propagation (under 0.25 sec)


21/22

brain!cortex etc.

6 cell layers of gray matter(cell bodies & dendrites)

arranged in functional columns (teams)extend from surface to white matter(myelinated axons)

7thed: Fig 5-8, 5-14, 5-25

8thed: Fig 5-9, 5-14, 5-25

brain!cortex etc.

6 cell layers of gray matter(cell bodies & dendrites)

arranged in functional columns (teams)extend from surface to white matter(myelinated axons)

7thed: Fig 5-8, 5-14, 5-25

8thed: Fig 5-9, 5-14, 5-25

cerebral cortex

4 major lobes

frontalvoluntary motor activity

speechelaboration of thought

parietal

touch, pressure, heat, painbody position (proprioception)

temporalsound sensation

motivation

emotionmemory

occipitalvision


22/22

1) the nervous system contains circuits for various inputs & outputs.2) the cellsin these circuits include receptor cells, interneurons, &

output neurons.3) the sensory structurescan be in the G-I tract, other internal

organs, the body surface, or sensory structures of the head.4) output neurons can be part of the motor, autonomic, or enteric

systems.

5) these circuits can be entirely in the central nervous system(e.g.,from the eye to the brain), entirely in the peripheral nervous

system(e.g., within the gastrointestinal tract), or partly peripheral &partly central(e.g., from a touch receptor into the spinal cord, up tosomatosensory cortex, back down to a motor pathway, and out to

skeletal muscle).6) the signalsin these circuits include receptor signals generated by

sensory stimuli, signals processed by the nervous system(combinations of excitation & inhibition), and signals sent to controlvarious tissues (muscles, glands, other neurons).

SUMMARY

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Neurobiology, Physiology, and Behavior