Bio 11 - Nerves & Hormones Powepoint

8/8/2019 Bio 11 - Nerves & Hormones Powepoint

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Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings

IB Biology 2010/2011Topic 6.5 Nerves, Hormones & Homeostasis

RNS Science


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Functional magnetic resonance imaging

Is a technology that can reconstruct a three-dimensional map of brain activity

Figure 48.1


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The nervous system consists of the central

nervous system (CNS) and peripheral nerves(sensory and motor neurons), and is composedof cells called neurons that can carry rapidelectrical impulses.

Nerve impulses are conducted from receptorsto the CNS by sensory neurons, within theCNS by relay neurons, and from the CNS toeffectors by motor neurons.


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Concept 48.5: The vertebrate nervous system

is regionally specialized In all vertebrates, the nervous system

Shows a high degree of cephalization anddistinct CNS and PNS components

Figure 48.19

Central nervoussystem (CNS) Peripheral nervous

system (PNS)Brain

Spinal cordCranialnerves

GangliaoutsideCNSSpinalnerves


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The Peripheral Nervous System

The PNS transmits information to and from the

CNS And plays a large role in regulating a

vertebrates movement and internal

environment



Two Categories of Peripheral Nerves

Spinal Nerves

31 pairs (left and right)

Emerge directly from the spinal cord

Mixed nerves which contain both sensory andmotor neurons.

Cranial Nerves

12 pairs which emerge from the brainstem

Eg. Optic nerve pair



The cranial nerves originate in the brain

And terminate mostly in organs of the headand upper body

The spinal nerves originate in the spinal cord

And extend to parts of the body below thehead



The PNS can be divided into two functional

components The somatic nervous system and the

autonomic nervous systemPeripheral

nervous system

Somaticnervoussystem

Autonomicnervoussystem

Sympatheticdivision

Parasympatheticdivision

Entericdivision

Figure 48.21



The somatic nervous system

Carries signals to skeletal muscles

The autonomic nervous system

Regulates the internal environment, in aninvoluntary manner

Is divided into the sympathetic,

parasympathetic, and enteric divisions



The sympathetic and parasympathetic divisions

Have antagonistic effects on target organsParasympathetic division Sympathetic division

Action on target organs: Action on target organs:

Location of preganglionic neurons:brainstem and sacralsegments of spinal cord

Neurotransmitter released bypreganglionic neurons:acetylcholine

Location of postganglionic neurons:in ganglia close to or within target organs

Neurotransmitter released bypostganglionic neurons:acetylcholine

Constricts pupilof eye

Stimulates salivarygland secretion

Constrictsbronchi in lungs

Slows heart

Stimulates activityof stomach and

intestines

Stimulates activityof pancreas

Stimulatesgallbladder

Promotes emptyingof bladder

Promotes erectionof genitalia

Cervical

Thoracic

Lumbar

Synapse

Sympatheticganglia

Dilates pupilof eye

Inhibits salivarygland secretion

Relaxes bronchiin lungs

Accelerates heart

Inhibits activity of stomach and intestines

Inhibits activityof pancreas

Stimulates glucoserelease from liver;inhibits gallbladder

Stimulatesadrenal medulla

Inhibits emptyingof bladder

Promotes ejaculation and

vaginal contractionsSacral

Location of preganglionic neurons:thoracic and lumbar segments of spinal cord

Neurotransmitter released bypreganglionic neurons:acetylcholine

Location of postganglionic neurons:some in ganglia close totarget organs; others in

a chain of ganglia near spinal cord

Neurotransmitter released bypostganglionic neurons:norepinephrine

Figure 48.22



Sensory neurons transmit information from

sensors A stimulus is a change in the environment

(internal or external) that is detected by areceptor and elicits a response

Sensory information is sent to the CNS

Where interneurons integrate the information

Motor output leaves the CNS via motor neurons

Which communicate with effector cells



Information Processing

Nervous systems process information in three

stages Sensory input, integration, and motor output

Figure 48.3

Sensor

Effector-an organ that performs a response

Motor output

IntegrationSensory input

Peripheral nervous

system (PNS)

Central nervous

system (CNS)



Knee-Jerk Reflex(brain not involved) an example A reflex is a rapid, unconscious response, that is, a reaction to a

stimulus

The three stages of information processing

Figure 48.4

Sensory neuronsfrom the quadricepsalso communicatewith interneurons in the spinal cord.

The interneuronsinhibit motor neuronsthat supply the

hamstring (flexor)muscle. This inhibitionprevents the hamstringfrom contracting,which would resistthe action of the quadriceps.

The sensory neurons communicate withmotor neurons that supply the quadriceps. Themotor neurons convey signals to the quadriceps,causing it to contract and jerking the lower leg forward.

4

5

6

The reflex isinitiated by tapping

the tendon connectedto the quadriceps

(extensor) muscle.

1

Sensors detecta sudden stretch inthe quadriceps.

2 Sensory neuronsconvey the informationto the spinal cord.

3

Quadricepsmuscle

Hamstringmuscle

Spinal cord(cross section)

Gray matter

Whitematter

Cell body of sensory neuronin dorsalroot ganglion

Sensory neuronMotor neuronInterneuron

motor neuronsin ventral root


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Human Sensory Receptors

mechanoreceptors,

Sense of touch due to pressure receptors,which also detect changes in blood pressure inarteries.

Stretch receptors in lungs,

proprioceptors in muscle, tendons, ligaments, joints to give info on position of arms and legs

ie; posture and balance.

Inner ear pressure receptors sensitive towaves of fluids for info about equilibrium


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Chemoreceptors,

Sense of taste and smell, in some bloodvessels they monitor pH which cause us tochange breathing rate.

Pain receptors are a type of chemoreceptor which respond to chemicals released by

damaged tissues


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Thermoreceptors

Warm and cold receptors respond totemperature changes

and Photoreceptors.

In the eyes, rod cells respond in dim light inblack and white vision, cone cells respond tobright light and give us colour vision


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Diagram of the human eye.

Sclera, cornea, conjunctiva, eyelid, choroid, aqueoushumour, pupil, lens, iris, vitreous humour, retina, fovea,optic nerve and blind spot.

The conjunctiva is the thin, transparent tissue thatcovers the outer surface of the eye. It begins at theouter edge of the cornea , covering the visible part of the sclera , and lining the inside of the eyelids. It isnourished by tiny blood vessels that are nearly invisibleto the naked eye.

The conjunctiva also secretes oils and mucous that moistenand lubricate the eye.
http://www.stlukeseye.com/popups/cornea.htmhttp://www.stlukeseye.com/popups/sclera.htmhttp://www.stlukeseye.com/popups/sclera.htmhttp://www.stlukeseye.com/popups/cornea.htm


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The structure of the vertebrate eye

Figure 49.18

Ciliary body

Iris

Suspensoryligament

Cornea

Pupil

Aqueous

humor

Lens

Vitreous humor

Optic disk

(blind spot)

Central artery andvein of the retina

Opticnerve

Fovea (center of visual field)

Retina

ChoroidSclera


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Diagram the retina to show the cell types and the directionin which light moves.

Include names of rod and cone cells, bipolar neuronsand ganglion cells.

Compare rod and cone cells.

use in dim light versus bright light

one type sensitive to all visible wavelengths versusthree types sensitive to red, blue and green light

passage of impulses from a group of several rod cellsto a single nerve fibre in the optic nerve versuspassage from a single cone cell to a single nerve fibre.


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Three other types of neurons contribute to

information processing in the retina Ganglion cells, horizontal cells, and amacrine

cells

Figure 49.23Opticnervefibers

Ganglion

cell

Bipolar

cell

Horizontalcell

Amacrinecell

Pigmentedepithelium

NeuronsCone Rod

Photoreceptors

Retina

Retina

Optic nerve

Tobrain


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Signals from rods and cones

Travel from bipolar cells to ganglion cells

The axons of ganglion cells are part of the opticnerve

That transmit information to the brain

Figure 49.24

Leftvisualfield

Rightvisualfield

Lefteye

Righteye

Optic nerve

Optic chiasm

Lateralgeniculatenucleus

Primaryvisual cortex


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Summary of Parts of the Eye with FunctionsPart FunctionsIris Regulates the size of the pupil

Pupil Opening that admits light

Retina Contains receptors for vision

Aqueous humour Transmits light rays and supports the eyeball

Vitreous humour Transmits light rays and supports the eyeball

Rods Allow black and white vision in low light

Cones Allow colour vision in bright light

Fovea An area of densely packed cone cells where vision is most acute

Lens Focuses the light rays

Sclera Protects and supports the eyeball

Cornea Focusing begins here

Choroid Absorbs stray light

Conjunctiva Covers the sclera and cornea and keeps eye moist

Optic Nerve Transmits impulses to the brain

Eye Lid Protects the eye


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Processing Visual Stimuli

The processing of visual stimuli, including edgeenhancement and contralateral processing.

Edge enhancement occurs within the retina and can bedemonstrated with the Hermann grid illusion andother illusions .
http://dragon.uml.edu/psych/illusion.htmlhttp://dragon.uml.edu/psych/illusion.html


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Contralateral processing is due to the opticchiasma, where the right brain processesinformation from the left visual field and viceversa (see a couple of slides back). This canbe illustrated by the abnormal perceptions of

patients with brain lesions.


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Label a diagram of the ear.

Include pinna, eardrum, bones of the middleear, oval window, round window, semicircular canals, auditory nerve and cochlea.

Explain how sound is perceived by the ear,including the roles of the eardrum, bones of themiddle ear, oval and round windows, and the

hair cells of the cochlea. The roles of the other parts of the ear are not

expected


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Exploring the structure of the human ear

Figure 49.8

Pinna

Auditorycanal

Eustachiantube

Tympanicmembrane

Stapes

Incus

Malleus

Skullbones

Semicircular canals

Auditory nerve,to brain

Cochlea

Tympanicmembrane

Ovalwindow

Eustachiantube

Roundwindow

Vestibular canal

Tympanic canal

Auditory nerve

BoneCochlear duct

Hair cells Tectorialmembrane

Basilar membrane

To auditorynerve

Axons of sensory neurons

1 Overview of ear structure 2 The middle ear and inner ear

4 The organ of Corti 3 The cochleaOrgan of Corti

Outer ear Middle

ear Inner ear


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How Sound is Perceived by the Ear..

Vibrations of the eardrum due to sound wavesare amplified by the bones of the ear (hammer,anvil and stirrup) approximately 20 times.

The stapes rests on the oval window of the

cochlea and causes it to vibrate, which vibratesliquid in the cochlea and moves hairs on hair cells in the cochlea.

Hair cells synapse with sensory neurons in theauditory nerve leading to the brain.

The degree to which the hairs bend is sound


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Draw and label a diagram of the structure of amotor neuron.

Include dendrites, cell body with nucleus, axon,myelin sheath, nodes of Ranvier and motor end

plates. The junction at which a neuron sends a

chemical to muscle tissue is known as a motor

end plate


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Neuron Structure

Most of a neurons organelles

Are located in the cell bodyDendrites

Cell body

Nucleus

AxonSignaldirection

Synapse

Myelin sheath(Schwann Cells)

Synapticterminals

Presynaptic cell Postsynaptic cell

Nodes of Ranvier


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Define resting potential and action potential(depolarization and repolarization).

Explain how a nerve impulse passes along anon-myelinated neuron.

Include the movement of Na+ and K+ ions tocreate a resting potential and an actionpotential.


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Ion pumps and ion channels maintain the restingpotential of a neuron

Across its plasma membrane, every cell has avoltage

Called a membrane potential

The inside of a cell is negative

Relative to the outside


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The membrane potential of a cell can bemeasured

Figure 48.9

APPLICATION Electrophysiologists use intracellular recording to measure themembrane potential of neurons and other cells.

TECHNIQUE A microelectrode is made from a glass capillary tube filled with an electrically conductivesalt solution. One end of the tube tapers to an extremely fine tip (diameter < 1 m). While looking through amicroscope, the experimenter uses a micropositioner to insert the tip of the microelectrode into a cell. Avoltage recorder (usually an oscilloscope or a computer-based system) measures the voltage between themicroelectrode tip inside the cell and a reference electrode placed in the solution outside the cell.

Microelectrode

Referenceelectrode

Voltagerecorder

70 mV


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A neuron that is not transmitting signals

Contains many open K + channels and fewer open Na + channels in its plasma membrane

The diffusion of K + and Na + through these

channels Leads to a separation of charges across the

membrane, producing the resting potential

The concentration of Na + is higher in theextracellular fluid than in the cytosol

While the opposite is true for K +


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The net effect is a negative charge inside thecell due to a number of negatively chargedorganic ions permanently located in thecytoplasm of the axon

G t d I Ch l


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Gated Ion Channels

Gated ion channels open or close

In response to membrane stretch or thebinding of a specific ligand

In response to a change in the membrane

potential


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Action potentials are the signals conducted by axons

If a cell has gated ion channels Its membrane potential may change in response to

stimuli that open or close those channels

An action potential Is a brief all-or-none depolarization of a neurons

plasma membrane

Is the type of signal that carries information alongaxons


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Both voltage-gated Na + channels and voltage-gated K + channels

Are involved in the production of an actionpotential

When a stimulus depolarizes the membrane

Na + channels open, allowing Na + to diffuse intothe cell


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As the action potential subsides

K+ channels open, and K + flows out of the cell

A refractory period follows the action potential

During which a second action potential cannotbe initiated


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Figure 48.14

+ + + + + +

+ + + + + +

+

+ + + +

+

+ + + + + +

+ + + +

+ ++ +

+ ++ +

+ ++ +

+ + + + + + + +

Na +

Na +

Na +

Actionpotential

Actionpotential

ActionpotentialK+

K+

K+

Axon

An action potential is generatedas Na + flows inward across themembrane at one location.

1

2 The depolarization of the actionpotential spreads to the neighboringregion of the membrane, re-initiatingthe action potential there. To the leftof this region, the membrane isrepolarizing as K + flows outward.

3 The depolarization-repolarization process isrepeated in the next region of themembrane. In this way, local currentsof ions across the plasma membranecause the action potential to be propagatedalong the length of the axon.

K+

At the site where the action potential isgenerated

An electrical current depolarizes theneighboring region of the axon membrane

Conduction Speed


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Conduction Speed

The speed of an action potential

Increases with the diameter of an axon

In vertebrates, axons are myelinated

Also causing the speed of an action potentialto increase


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Action potentials in myelinated axons

Jump between the nodes of Ranvier in aprocess called saltatory conduction

Cell body

Schwann cell

Myelinsheath

Axon

Depolarized region(node of Ranvier)

++ +

++ +

++ +

++

Figure 48.15

Synaptic Transmission


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Synaptic Transmission

Explain the principles of synaptic transmission.

Include the release, diffusion and binding of the neurotransmitter, initiation of an actionpotential in the post-synaptic membrane, andsubsequent removal of the neurotransmitter.


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In a chemical synapse, a presynaptic neuron

Releases chemical neurotransmitters, whichare stored in the synaptic terminal

Figure 48.16

Postsynapticneuron

Synapticterminalof presynapticneurons

5m

Direct Synaptic Transmission


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Direct Synaptic Transmission Calcium ions diffuse into the buttonWhen an action potential

reaches a terminal button:

Vesicles with neurotransmitter fuse with the presynapticmembrane

Neurotransmitter diffuses across cleft and binds with a receptor protein on the postsynaptic membrane, which opens an ionchannel for sodium to diffuse into post neuron

This depolarization initiates an action potential in the postmembrane.

Enzymes then break down the neurotransmitter which releases itfrom the receptor protein

Sodium ion channel closes

Neurotransmitter molecules diffuse back into presynaptic buttons


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When an action potential reaches a terminal

The final result is the release of neurotransmitters into the synaptic cleft

Figure 48.17

Presynapticcell

Postsynaptic cell

Synaptic vesiclescontainingneurotransmitter

Presynapticmembrane

Postsynapticmembrane

Voltage-gatedCa 2+ channel

Synaptic cleft

Ligand-gatedion channels

Na +K+

Ligand-gatedion channel

Postsynapticmembrane

Neuro-transmitter

1 Ca 2+

2

3

4

5

6


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Major neurotransmitters

Table 48.1

Acetylcholine


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Acetylcholine

Acetylcholine

Is one of the most common neurotransmittersin both vertebrates and invertebrates

Can be inhibitory or excitatory

Enter the Endocrine System glands with hormones


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Enter the Endocrine System glands with hormones

Homeostasis involves maintaining the internalenvironment (blood and ECF) between limits,including

blood pH,

carbon dioxide concentration,

blood glucose concentration,

body temperature and

water balance (kidney, next year).


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Homeostasis involves monitoring levels of variables and correcting changes in levels bynegative feedback mechanisms.

The nervous system, largely the ANS, and

endocrine system work together to ensurehomeostasis

Control of Body Temperature


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Control of Body Temperature

A temperature rise is sensed bythermoreceptors in the skin which signals thehypothalmus of the brain to cool things down

Increased activity of the sweat glands,

arterioles in the skin dilate allowing heat totransfer to the surface via the blood, water evaporates which cools down the skin.

Cooling reverses this process and causesshivering so muscles generate heat.

Control of blood glucose levels


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Control of blood glucose levels.

Glucose absorbed by the capillary beds of theintestinal villi, is transported by the hepaticportal vein to the liver.

Liver cells (hepatocytes) are acted upon by

insulin and glucagon, two hormones producedby the pancreas, which have antagonisticeffects with respect to blood glucoseconcentrations.


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High blood glucose levels stimulate the betacells of the pancreas to secrete insulin, whichcauses protein channels in cell membranes, toopen and facilitate diffusion of glucose intocells.

In addition, muscle cells and hepatocytes willtake up the glucose and store it as glycogenpolymers.


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As blood glucose levels drop, alpha cells of thepancreas produce and secrete glucagon, whichcirculates through the bloodstream.

When received by hepatocytes of the liver and

muscle cells, they hydrolyze their storedglycogen to produce glucose.

This glucose is released into the bloodstream

Diabetes


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Diabetes

Characterized by hyperglycaemia (high blood sugar) Twodifferent types:

Type I diabetes

When beta cells of the pancreas do not produceenough insulin

Controlled by insulin injection

Type II diabetes

Body cell receptors do not respond properly to glucose.

Controlled by diet

More on Diabetes.


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More on Diabetes.

Type I is an autoimmune disease

Bodys immune system destroys beta cells solittle or no insulin is produced

Type II body cells change response to insulin,called insulin resistance

90% of diabetes are Type II due to genetichistory, obesity, lack of exercise, advancedage.


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Bio 11 - Nerves & Hormones Powepoint

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