Warm-Up

1. Name the 2 main organs of the nervous system.

2. Draw and label the parts of a neuron.

Warm-Up

•Label the parts of the neuron below.

A

B

EF

C

G

D

Warm-Up1. One neuron transmits a nerve impulse at 40

m/s. Another conducts at the rate of 1 m/s. Which neuron has a myelinated axon?

2. List the following in order:A. K+ channels open and K+ floods out of cellB. Membrane is polarized (resting potential)C. Neurotransmitters are released from vesicles into

synaptic cleftD. Na+ channels open and Na+ floods into cellE. Stimulus triggers membrane depolarization

3. What restores the resting potential of a neuron?

The Nervous System

Nervous System

•Master controlling and communicating system

Basic Functions1.1. Sensory input Sensory input – gather information2.2. IntegrationIntegration – process and interpret

sensory input3.3. Motor output Motor output – response by muscles and

glands

Organization

A.A. Central Nervous System (CNS)Central Nervous System (CNS)▫Brain & spinal cord▫Integrative and control centers

B.B. Peripheral Nervous System (PNS)Peripheral Nervous System (PNS)▫Nerves (spinal nerves, cranial nerves)▫Communication lines between CNS and rest of body▫Two Divisions:Two Divisions:

1.1. Sensory (afferent) DivisionSensory (afferent) Division: Sensory receptors CNS

2.2. Motor (efferent) DivisionMotor (efferent) Division: CNS effectors (muscles & glands)

Motor Division

• Somatic nervous systemSomatic nervous system (voluntary) – control skeletal muscles

• Autonomic nervous systemAutonomic nervous system (ANS) (involuntary) – regulate smooth muscles, cardiac, glands▫Subdivisions: sympatheticsympathetic &

parasympatheticparasympathetic

Nervous TissueNervous Tissue1.1. NeuronsNeurons (nerve cells) - transmit message

Anatomy:▫ Cell bodyCell body – contains nucleus; metabolic center▫ DendriteDendrite – fiber that conveys messages toward

cell body▫ AxonAxon – conduct nerve impulses away from the

cell body▫ Axon terminalsAxon terminals – end of axon; contain

neurotransmitters & release them▫ Synaptic cleft/synapseSynaptic cleft/synapse – gap between neurons

Nervous TissueNervous Tissue2. Supporting cells (NeurogliaNeuroglia)CNSCNS: : astrocytes, microglia, ependymal cells, astrocytes, microglia, ependymal cells,

oligodendrocytesoligodendrocytes barrier between capillaries and neurons protect neurons immune/defense line brain and spinal cord cavities wrap nerve fibers produces myelin sheaths (covering)

PNSPNS: Schwann cells, satellite cells: Schwann cells, satellite cells surround large neurons protect & cushion

• MyelinMyelin:: whitish, fatty material that covers nerve fibers to speed up nerve impulses

• Schwann cellsSchwann cells:: surround axons and form myelin sheath

• Myelin sheathMyelin sheath:: tight coil of wrapped membranes• Nodes of RanvierNodes of Ranvier: gaps between Schwann cells

• GangliaGanglia: collections of cell bodies• Bundles of nerve fibers = tractstracts (CNS) or

nervesnerves (PNS)• White matterWhite matter: dense collections of myelinated

fibers• Gray matterGray matter: unmyelinated fibers & cell bodies

It’s a Mad, Mad, Mad Neuron

Classification of Neurons

1. Functional Classification: direction nerve impulse is traveling

Sensory neurons

Motor neurons

Interneurons

carry impulses from sensory receptors to

CNS

carry impulses from CNS to muscles &

glands

connect sensory & motor neurons

Vision, hearing, equilibrium, taste, smell,

pain, pressure, heat

2. Structural Classification: # processes extending from cell body

Multipolar Bipolar Unipolar

1 axon, several dendrites

1 axon, 1 dendrite

1 process

Most common (99%)

RareShort with 2

branches (sensory, CNS)

Eg. Motor neurons,

interneurons

Eg. retina, nose, ear

Eg. PNS ganglia

Nerve Impulses

Neuron Function

1.1. IrritabilityIrritability: ability to respond to stimulus & convert to nerve impulse

2.2. ConductivityConductivity: transmit impulse to other neurons, muscles, or glands

Exciting a Neuron:•Cell membrane at rest = polarizedpolarized

▫Na+ outside cell, K+ inside cell▫Inside is (-) compared to outside

•Stimulus excited neuron (Na+ rushes in) becomes depolarizeddepolarized

•Depolarization activates neuron to transmit an action potential action potential (nerve impulse)▫All-or-none response▫Impulse conducts down entire axon

•K+ diffuses out repolarizationrepolarization of membrane

•Na+/K+ ion concentrations restored by sodium-potassium pumpsodium-potassium pump (uses ATP)

Resting membrane potential (-70mV)

Gated Ion Channels (Na+ and K+)

Depolarization

• Saltatory conductionSaltatory conduction: electrical signal jumps from node to node along myelinated axon (30x faster!)

Multiple Sclerosis (MS)•Autoimmune disease•Myelin sheaths destroyed reduced to

hardened lesions (scleroses)•Blindness, muscle weakness, speech

disturbance, urinary incontinence•Treatment: interferons, glatiramer (hold

off attacks)

Nerve Conduction• Action potential

reaches axon terminal vesicles release neurotransmittersneurotransmitters (NT) (NT) into synaptic cleftsynaptic cleft

• NT diffuse across synapse bind to receptors of next neuron

• Transmission of a nerve impulse = electrochemical eventelectrochemical event

Neuron Talk

Neurotransmitters• 50+ identified• ExcitatoryExcitatory: cause depolarization• InhibitoryInhibitory: reduce ability to cause action

potential• Eg. acetylcholine, serotonin, endorphins

Mouse Party

NeurotransmittersNeurotransmitt

erNeurotransmitt

erActionAction Affected by:Affected by:

Acetylcholine muscle contraction botulism, curare (paralytic), nicotine

Dopamine “feeling good” cocaine, amphetamines

Serotonin sleep, appetite, nausea, mood, migraines

Prozac, LSD, ecstasy

Endorphins inhibit pain morphine, heroin, methadone

GABA main inhibitory NT alcohol, Valium, barbiturates

Reflexes

•Rapid, predictable, involuntary responses to stimuli

1.Somatic Reflexes: stimulate skeletal muscles▫ Eg. jerking away hand from hot object

2.Autonomic Reflexes: regulate smooth muscles, heart, glands▫ Eg. salivation, digestion, blood pressure,

sweating

Reflex Arc (neural pathway)

Five elements:1. Receptor – reacts to stimulus2. Sensory neuron3. CNS integration center4. Motor neuron5. Effector organ – muscle or gland

Reflex ActivitiesPatellar (Knee-jerk)

ReflexPupillary Reflex

Patellar (Knee-jerk) Reflex

Pupillary Reflex

• Stretch reflex• Tapping patellar

ligament causes quadriceps to contract knee extends

• Help maintain muscle tone, posture, & balance

• Optic nerve brain stem muscles constrict pupil

• Useful for checking brain stem function and drug use

Flexor (withdrawal) reflex:painful stimulus withdrawal of threatened body part▫Pin prick

Plantar reflex:draw object down sole of foot curling of toes▫Babinski’s sign: check to see

if motor cortex or corticospinal tract is damaged

Voluntary Reactions

•More neurons and synapses are involved longer response times

Reflex = Involuntary Reaction Voluntary Reaction

Warm-Up

1. List and describe the 5 elements of a reflex arc.

2. List an example of a reflex.

3. What is the difference between a reflex and a voluntary reaction?

Human Brain

4 Major Regions

1. Cerebral Hemispheres

2. Diencephalon3. Brain stem4. Cerebellum

1. Cerebral Hemispheres (Cerebrum)L & R hemispheresCorpus callosum: large fiber tract;

connects 2 hemispheresLobes: major regions (named for cranial

bones) ParietalParietal, frontalfrontal, occipitaloccipital, temporaltemporal

Gyri (gyrus) = elevated ridges of tissueSulci (sulcus) = shallow groovesFissures = deeper grooves, separate

large regions of brainMotor & sensory function: opposite

hemispheres

Cerebral Cortex•Grey matter•“Executive suite” conscious mind

Functions of the Major Lobes

2. Diencephalon (interbrain)3 main structures:1.Thalamus: relay station for incoming info2.Hypothalamus:

A. Autonomic control center (heart rate, BP, digestion)

B. Emotional response (limbic system)C. Body temperature regulationD. Regulate food intakeE. Sleep-wake cyclesF. Control endocrine system pituitary gland at

base3.Epithalamus: pineal gland (sleep-wake cycle)

Diencephalon

3. Brain Stem

•Programmed, automatic behaviors for survival•3 regions:

1. Midbrain: vision, hearing, reflex2. Pons: breathing3. Medulla oblongata: heart rate, BP,

breathing, swallowing, vomiting, coughing, sneezing

Brain Stem

4. Cerebellum

•Balance, equilibrium, timing of skeletal muscle activity

Protection of CNS•Meninges: connective tissue covering

CNS structures▫Dura mater (leathery outer), arachnoid

mater (web-like middle), pia mater (surface of brain)

▫Meningitis: inflammation of meninges; bacterial or viral infection

•Cerebrospinal fluid (CSF): watery cushion to protect NS from trauma▫Lumbar (spinal) tap – test for infection,

tumors, multiple sclerosis

Meningitis

Symptoms of Meningitis

Treatment for Meningitis•Bacterial antibiotics•Herpes meningitis antiviral meds•IV fluids•Prevention: vaccines for bacterial

infections (HiB)

Blood-Brain Barrier: endothelial cells in capillaries prevent substances from crossing into brain

NO:•Urea•Toxins•Proteins•White blood cells•Bacteria•Most drugs

YES:•Water•Glucose•Amino acids•Gases•Fat-soluble

substances•Some drugs:

anesthetics, alcohol, nicotine

The Senses

Special senses

• Smell• Taste• Sight• Hearing• “Touch” = temperature + pressure

+ pain of skin, muscles, & joints• Equilibrium (in the ear)

Sensory Receptors•Large complex organs (eyes, ears)

•Localized clusters of receptors (taste buds, olfactory epithelium)

Vision Tests

Are the squares inside the blue and yellow squares all the same color?

Bezold effect

The smaller squares inside the blue and yellow squares are all the same color.

They seem different (magenta and orange) because a color is perceived differently depending on its relation to adjacent colors (here blue or yellow depending on the outer square).

Are the horizontal lines straight or crooked?

Café Wall Illusion

The horizontal lines are straight, even though they do not seem straight.  In this illusion, the vertical zigzag patterns disrupt our horizontal perception.

Does Lincoln’s face look normal?

Some neurons in the brain seem specialized in processing faces. Faces are usually seen upright. When presented upside down, the brain no longer recognizes a picture of a face as a face but rather as an object. Neurons processing objects are different from those processing faces and not as specialized. As a consequence these neurons do not respond to face distortions as well. This explains why we miss the weird eyes when the face is inverted.

Can you see a baby?

Illusory ContourThe baby’s head is on the left, the baby’s feet

are against the trunk of the tree on the right.Illusory Contour: a form of visual

illusion where contours are perceived without a luminance or color change across the contour

How quickly can you say the color of the words below?

Taste Tests

Jellybean Test

Flavor = taste + smell

5 Types of Taste Receptors

Aging

•After age 50, ability to smell and taste decrease

•Membranes lining nose become thinner & drier olfactory nerve deteriorate

•# taste buds decrease with age more difficult to detect sweet/salty foods taste more bitter

•As people age, their food tastes more bland eat less possible malnutrition

Genetics of Taste

PTC = phenylthiocarbamide

•Discovered in 1931 by when a DuPont chemist named Arthur Fox accidentally released a cloud of fine crystalline PTC in the lab.

•A nearby colleague complained of the bitter taste, while Dr. Fox tasted nothing.

•Fox continued to test the taste buds of family and friends, setting the groundwork for future genetic studies.

Genetics of PTC Tasting•Gene for tasting PTC (Tas2r38) is located on Chromosome 7.

•PAV = taster (T), AVI = nontaster (t), AAV = another allele▫PAV-PAV = TT = very bitter▫PAV-AVI = Tt = somewhat

bitter▫AVI-AVI = tt = nontaster

•General Population: 70% Tasters, 30% Nontasters

TAS2R38

Bitter tastes = Result of selection pressures?•Thiocynate Compounds (bitter taste)

found in broccoli, cauliflower, mustard family▫Tasters: avoid these foods in diet▫Nontasters: more varied diet, include

green leafy veggies•Thiocynates might inhibit thyroid

function tasters may have protection against thyroid diseases

Bitter tastes = Result of selection pressures?

•Poisons = bitter taste▫Tasters: part of hunter-gatherer

societies?•Genetic Drift

▫Europeans: all 3 alleles (PAV, AVI, AAV)

▫Asians: AAV allele rare▫Native Americans: 98% have PAV

allele only

Denver Museum of Nature and Science•Expedition Health: Genetics of

Taste Study•Purpose of Study:

▫Is ability to taste bitter compounds related to what foods you eat, your % body fat, and BMI?

▫Is your ability to taste bitter compounds related to your genetic ancestry?

Substances related to PTC

•Thiourea (thiocarbamide) – very bitter!!!•Sodium benzoate – sweet, salty, bitter, no

taste▫Food preservative

Family Pedigree

•Tasters:▫Supertasters

(TT)▫Tasters (Tt)

•Non-tasters (tt)