Nervous & Other Systems

8/13/2019 Nervous & Other Systems

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Nervous Systems


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Nervous Systems


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Evolution of the Nervous

System

Nerve Net

Cnidarian, Ctenophora

Nerve Ring with radial nerves Echinodermata

Bilateral Nervous Systems

Cephalization (ganglia or brain) Nerve cord


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Evolution of the Nervous

System

Bilateral Nervous Systems

Ganglia and two or more longitudinal nerve

cords

platyhelminthes, some mollusca

Ganglia (brain) and ventral nerve cord

annelida, arthropoda, some mollusca

Brain and dorsal nerve cord chordata


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Overview of a Nervous

System


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Overview of a Nervous System

Sensory Input conduction of signals from sensory

receptors

PNS Integration

environmental information is interpreted

CNS (brain and spinal cord) Motor Output

conduction of signals to effector cells

PNS


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Neurons


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Neurons

Cell body

nucleus and organelles

Dendrites short and branched

toward cell body

Axons long and unbranched

away from cell body


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Axons

Myelin Sheath - insulating layer

Node of Ranvier - gaps between Schwann

Cells

Synaptic Terminals - neuron ending


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Clusters of Neurons

Ganglion

Cluster of nerve cell bodies in the PNS

Nuclei

Cluster of cells in the brain


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Supporting Cells

Glia (glue)

Astrocytes (structural support)

Creates tight junctions and forms the blood-brain barrier

Radial Glia Form tracks for new neurons formed in the neural tube

Oligodendrocytes

Form myelin sheath in brain

Schwann Cells Form myelin sheath in the PNS


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Reflex

Sensory

neuron

to a

motorneuron


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Neural Signals

Membrane Potential

Sodium-Potassium Pump


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Threshold Potential


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Resting State

Both sodium

and

potassium

activationgates are

closed

Interior of

cell isnegative


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Depolarization State

Sodium

activation

gates are

opened on

somechannels

Interior of

cell

becomesmore

positive


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Rising Phase of Action Potential

Most sodium

activation

gates are

opened Potassium

activation

gates are still

closed


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Undershoot

Both gates tosodiumchannels areclosed

Potassiumchannels areclosing

Membranereturns to itsresting state


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Propagation of

the Action

Potential Localized event

First actionpotentials

depolarization sets

off second action

potential Travels in one

direction due to

refractory period


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Salatory Conduction

Action Potential jumps from node to node

Speeds up signal from 5 m/sec to 150

m/sec


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Communication Between

Synapses

Electrical Synapses

gap junctions allow for direct transfer of action

potential (used during escape responses)

Chemical Synapses

uses neurotransmitters


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Chemical Synapse


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Chemical Synapses

Action potential triggers an influx of calcium Synaptic vesicles fuse with presynaptic

membrane

Neurotransmitter released into synaptic cleft Neurotransmitters bind to receptors and

open ion channels on postsynaptic

membrane which sets off new actionpotential

Neurotransmitters are degraded by enzymes

or removed by a synaptic terminal


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Neurotransmitters


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Postsynaptic Potentials


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Postsynaptic Potentials

Subthreshold doesnt reach threshold

Temporal Summation

two signals do not reach threshold level butoccur close enough to set off action

potential

Spatial Summation

two signals are set off at the same time

setting off an action potential

Spatial Summation with an inhibitor

doesnt reach threshold


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Vertebrate

NervousSystem


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Central Nervous System

Ventricles (4)

Cerebrospinalfluid

White Matter Made up of

axons

Gray Matter

Made up ofdendrites


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Peripheral Nervous System


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Peripheral Nervous System

Autonomic Nervous System regulates the

internal environment (usually involuntary)

Somatic Nervous System regulates the

external environment (usually voluntary)


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Autonomic Nervous System


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Autonomic Nervous System

Sympathetic Division

Flight or fight response

Parasympathetic Division

Rest or digest response


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Brain


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The Brainstem

The Medulla Oblongata and

the Pons controls breathing,

heart rate, digestion

The Cerebellum controls

coordination of movement

and balance


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The Midbrain

The Midbrain receives,

integrates, and projects

sensory information to the

forebrain


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The Diencepholon

Forebrain

Epithalamus

Includes the pineal gland and the

choroid plexus

Thalamus

conducts information to specific areas of

cerebrum

Hypothalamus

produces hormones and regulates bodytemperature, hunger, thirst, sexual

response, circadian rhythms


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The Telencepholon

Cerebrum

with cortex and

corpus callosum

higher thinking


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Cerebrum


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Cerebrum


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Limbic System

Regulates

emotions

Association

with differentsituations is

done mostly

in the

prefrontal

lobe


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Memory

Short Term

Done in the

frontal lobe

Long Term Frontal lobes

interact with

the

hippocampusand the

amygdala to

consolidate


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Sensory Receptors

Mechanoreceptors

Pain Receptors

Thermoreceptors

Chemoreceptors

Electromagnetic Receptors


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Sensory Receptors

Mechanoreceptors

Pain Receptors

Thermoreceptors


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Sensory Receptors

Chemoreceptors


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Sensory Receptors

Electromagnetic receptors

Evolution of the


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Evolution of the

Eye

Complex eyes

have developed

many times

Evolution of the


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Evolution of the

Eye All light-sensitive organsrely on photoreceptorsystems employing a

family of proteins called

opsins. Further, the

genetic toolkit for

positioning eyes is

common to all animals:

the PAX6 genecontrolswhere the eye develops

in organisms ranging

from mice to humans to

fruit flies
http://en.wikipedia.org/wiki/Opsinhttp://en.wikipedia.org/wiki/Pax_geneshttp://en.wikipedia.org/wiki/Drosophila_melanogasterhttp://en.wikipedia.org/wiki/Drosophila_melanogasterhttp://en.wikipedia.org/wiki/Pax_geneshttp://en.wikipedia.org/wiki/Opsin


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Photoreceptors Eye cups(ocelli) - light

detection Genetic basis

that started as a

light detector

600 mya

During the

Cambrian

explosionaround 540 mya

two types of

eyes arose


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Photoreceptors

Compound Eyes -

made up of

ommatidia that helps

detect movement


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Photoreceptors

Camera Type Eyes

Evolved several

times

Hagfish eye Lamprey eye

Jawed vertebrate

eyes


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Single Lens Eye

Sclera (white)

Cornea (clear)

Choroid (pigmented)

Iris (color of eye)

Retina (rods and cones)

Pupil Fovea (focal point)

Blind spot

S f E l ti


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Photoreceptors Scars of Evolution1. inside out retina

that forces light to

pass through the

cell bodies and

nerves before

hitting the retina2. blood vessels

across the retina

that cause

shadows

3. nerve fibers that

exit causing a blind

spot


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Focusing

Near vision ciliary muscle

contracted

lens becomes

more spherical

Distance vision

ciliary muscle

relaxed

lens becomes

flatter


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Visual Problems

Near-sightedness (myopia)

eyeball too long / focal point in front of fovea

Far-sightedness (hyperopia)

eyeball too short / focal point behind fovea

Astigmatism (blurred vision)

misshapen lens or cornea

H i d E ilib i


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Hearing and Equilibrium

Hearing Organ


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Hearing Organ Outer Ear

pinna and the auditory canal tympanic membrane

Middle Ear

malleus, incus and stapes oval window

Inner Ear

cochlea with the Organ of Corti with a basilar membrane and hair cells

Eustachian Tube


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Sound Volume

amplitude of sound wave

vibrates fluid in ear and bend hair cells whichgenerates more action potentials

Pitch frequency of sound wave

Equilibrium


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Equilibrium

Utricle and Saccule

Semicircular Canals

used to detect body position and movement


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Lateral Line

System Similar to inner ear detects movement of

current, moving

objects


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Statocysts

Equilibrium

contain

statoliths

Sound Systems in


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Sound Systems in

Invertebrates

Body hairs that vibrate

mosquitoes

Tympanic Membranes crickets


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Chemoreception

Taste Buds

sweet (tip), salty

(behind), sour (sides),

bitter (back of tongue)


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Chemoreception

Olfactory receptors cells

upper portion of nasal cavity

The Cost of Locomotion


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e Cost o oco ot o


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The Cost of Locomotion

Locomotion must overcome two forces: gravity

friction

Swimming is more efficient than running runner must overcome gravity

Larger animals travel more efficiently than

smaller animals Flight is the most costly (per minute)


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Skeletal Structures

Hydrostatic Skeleton

(cnidaria, ctenophora, platyhelminthes,

nematoda, annelida)

Exoskeletons mollusca, arthropoda

Endoskeletons

chordata

Cooperation of Muscles and


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Cooperation of Muscles and

Skeletons Muscles always

contract

Muscles

attached inantagonistic

pairs


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Skeletal Muscles

Muscles are made up ofmuscle fibers

Fibers are made up of

myofibrils Myofibrils are made up of

myofilaments

thin filaments (actin)

thick filaments (myosin)

Sliding Filament


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Sliding Filament

Model

Sacromeres (basic

functioning unit)

Z lines (border of

sacromeres)

H zone (center of

sacromere)

I band (only thin filaments)

A band (length of thick

filaments)

Sliding Filament


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Sliding Filament

Model During contraction, thin

and thick filaments slide

past each other

I band and H zonedecreases in size

Caused by myosin

head creating cross

bridge with actin fiberand then moves by

using ATP

Muscle


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Muscle

Control

Tropomyosinblocksmyosinbinding sites

Calcium ionsallow crossbridges toform

M l Fib


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Muscle Fibers

Fast Muscle Fibers

rapid, powerful

contractions

flight muscle

Slow Muscle Fibers

sustain, long

contractions

adductor muscles

I t b t M l


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Invertebrate Muscles

Flight muscles in insects are capable ofindependent contractions

wings beat faster than action potentials

Clam muscles contain paramyosin thatallows them to remain contracted with little

energy

Nematodes only have longitudinal musclethat gives them their characteristic

movements

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Nervous & Other Systems