Nervous System and Nervous System and Sense Organs = Sense Organs =

Ch 49Ch 49

• Also known as a nerve cellAlso known as a nerve cell

• Made of cell body, dendrites and axonMade of cell body, dendrites and axon

• DendriteDendrite – receives action potentials (many), extend – receives action potentials (many), extend

from cell bodyfrom cell body

• AxonAxon (one) transmits action potential away from cell (one) transmits action potential away from cell

bodybody

Neuron StructureNeuron Structure

Neuron StructureNeuron Structure

• Electrical signals Electrical signals

transmitted away from cell transmitted away from cell

body = body = action potentialaction potential

• Axon covered in lipid layer Axon covered in lipid layer

= = myelin sheathmyelin sheath

– Insulates neuron so it Insulates neuron so it

speeds up rate of speeds up rate of

transmissiontransmission

Neuron StructureNeuron Structure

• Based on membrane potential Based on membrane potential

(difference in electrical charge) across (difference in electrical charge) across

cell membranecell membrane

• Membrane potential changes w/ + or – Membrane potential changes w/ + or –

ions (Na and K)ions (Na and K)

Nerve ImpulseNerve Impulse

• Charge across membrane that exists when the neuron is Charge across membrane that exists when the neuron is

not conducting action potentialnot conducting action potential

• Neg. charged proteins greater Neg. charged proteins greater inin cell cell

• K+ ion conc. Is greater inside cellK+ ion conc. Is greater inside cell

• Na+ ions greater Na+ ions greater outsideoutside cell cell

• K+ readily diffuse out of cell leaving the cell negatively K+ readily diffuse out of cell leaving the cell negatively

charged (-70 mV)charged (-70 mV)

Resting PotentialResting Potential

• Happens when cell is stimulatedHappens when cell is stimulated

• Starts at point where cell body joins axonStarts at point where cell body joins axon

• Na+ rush in & Na+ channels openNa+ rush in & Na+ channels open

• Cell becomes more positive than outsideCell becomes more positive than outside

• Outside becomes more neg. than beforeOutside becomes more neg. than before

• Reverses “polarity” of the cell/environmentReverses “polarity” of the cell/environment

Action PotentialAction Potential

• Moves like a wave down length of axon – away Moves like a wave down length of axon – away

from cell bodyfrom cell body

• Afterward channels open, Na+ and K+ go back to Afterward channels open, Na+ and K+ go back to

“resting” state“resting” state

• Cannot “fire” again until resting state is reachedCannot “fire” again until resting state is reached

• Requires a lot of ATPRequires a lot of ATP

Action PotentialAction Potential

• A synapse is the area where neurons communicate…junction is A synapse is the area where neurons communicate…junction is

called synaptic cleftcalled synaptic cleft

• Released at end of axon across Released at end of axon across synaptic cleftsynaptic cleft (space between axon (space between axon

of one and dendrite of another)of one and dendrite of another)

• Go toward receptors on another neuron causing opening of NaGo toward receptors on another neuron causing opening of Na++

channelschannels

• If enough channels open the action potential starts and will continue If enough channels open the action potential starts and will continue

to fire, if not, then the nervous signal is stopped (is inhibited)to fire, if not, then the nervous signal is stopped (is inhibited)

NeurotransmittersNeurotransmitters

NeurotransmittersNeurotransmitters

– Gray matter = cell bodies Gray matter = cell bodies

– White matter = axons White matter = axons

1.1. Central Nervous SystemCentral Nervous System: brain + spinal cord: brain + spinal cord

2.2. Peripheral Nervous SystemPeripheral Nervous System: not brain or spinal cord: not brain or spinal cord

– Afferent neurons – from nerves in sense organs Afferent neurons – from nerves in sense organs

toward CNStoward CNS

– Efferent neurons – Efferent neurons – away from CNSaway from CNS to organs & to organs &

glandsglands

– Interneurons btwn motor & sensory neuronsInterneurons btwn motor & sensory neurons

OrganizationOrganization

Brain StructureBrain Structure

• Largest PortionLargest Portion

• Folded outer layer = cerebral cortexFolded outer layer = cerebral cortex

– Gray matterGray matter

• 2 hemispheres for motor & sensory activities2 hemispheres for motor & sensory activities

• Voluntary activityVoluntary activity

• Cerebral cortex used for:Cerebral cortex used for:

-higher mental functions, general movement, organ function, perception and -higher mental functions, general movement, organ function, perception and

behavioral reactionsbehavioral reactions

-split into the 4 lobes-split into the 4 lobes

CerebrumCerebrum

• Back of skullBack of skull

• Coordinates muscle actionCoordinates muscle action

• Movement, balance, postureMovement, balance, posture

• Receives sensory impulses from Receives sensory impulses from

muscles, tendons, joints, eyes, muscles, tendons, joints, eyes,

ears etc.ears etc.

CerebellumCerebellum

• Column of nerve tissueColumn of nerve tissue

• Spinal nerves originate hereSpinal nerves originate here

• SensorySensory (afferent) neurons carry signals (afferent) neurons carry signals

from receptors to spinal cord through from receptors to spinal cord through

dorsal rootsdorsal roots

• MotorMotor (efferent) neurons carry signals (efferent) neurons carry signals

from spinal cord to muscles and glands from spinal cord to muscles and glands

through through ventral rootsventral roots

Spinal CordSpinal Cord

• Skull and vertebraeSkull and vertebrae

• Protective layers (meninges)Protective layers (meninges)

• Cerebrospinal fluidCerebrospinal fluid

ProtectionProtection

• Divided into Divided into sensory & motorsensory & motor divisions divisions

• Important For reflexesImportant For reflexes

• Sensory divisionSensory division: : gets infogets info from internal and external from internal and external

environmentsenvironments

• Motor DivisionMotor Division- - reactionreaction to sensory info to sensory info

– Somatic nervous systemSomatic nervous system

– Autonomic Nervous SystemAutonomic Nervous System

Peripheral Nervous SystemPeripheral Nervous System

• Control movement of skeletal muscles using Control movement of skeletal muscles using

neurotransmitter (acetylcholine)neurotransmitter (acetylcholine)

• Also can be automatic = maintain balanceAlso can be automatic = maintain balance

• Controls reflexes (involuntary & often protective Controls reflexes (involuntary & often protective

movements)movements)

– Patellar reflexPatellar reflex: ex. Of spinal reflex : ex. Of spinal reflex bypasses brain = super bypasses brain = super

fastfast

Somatic Nervous SystemSomatic Nervous System

• Nerves that control internal conditions – Nerves that control internal conditions –

respiration, heartbeat, blood vessels etc.respiration, heartbeat, blood vessels etc.

• Divided into Divided into

– parasympatheticparasympathetic- used during normal conditions- used during normal conditions

– sympatheticsympathetic division – used in physical or emotional division – used in physical or emotional

stress “fight or flight” responsestress “fight or flight” response

Autonomic Nervous SystemAutonomic Nervous System

Physiological Effects of the Autonomic Nervous System

• Types of Receptors – respond to…..Types of Receptors – respond to…..

– Mechano – movement, pressureMechano – movement, pressure

– Photo – lightPhoto – light

– Chemo – chemicalsChemo – chemicals

– Thermo – temp.Thermo – temp.

– Pain – tissue damagePain – tissue damage

Perception of StimuliPerception of Stimuli

Types of Sensory Receptors

• Sensory receptors in higher conc. in Sensory receptors in higher conc. in

sense organs than other body partssense organs than other body parts

• Turn stimulus into electrical signals that Turn stimulus into electrical signals that

are sent to brainare sent to brain

Perception of StimuliPerception of Stimuli

• Ear Ear

– detects sound &detects sound &

– maintains balancemaintains balance

• Sound vibrations directed into ear by “outer ear”Sound vibrations directed into ear by “outer ear”

• Balance: fluid filled semicircular canals and small hairs Balance: fluid filled semicircular canals and small hairs

using mechanoreceptorsusing mechanoreceptors

– Bending of hairs releases neurotransmittersBending of hairs releases neurotransmitters

Hearing & BalanceHearing & Balance

Hearing & BalanceHearing & Balance

• Eyes detect light & transmit signals to brainEyes detect light & transmit signals to brain

• Retina receives the image & transmits through optic nerve to Retina receives the image & transmits through optic nerve to

brain brain

• rods & cones (photoreceptors) in retina convert light to rods & cones (photoreceptors) in retina convert light to

electrical signals brain can interpret electrical signals brain can interpret

– Rods respond dim lightRods respond dim light

– Cones respond bright light & distinguish colorCones respond bright light & distinguish color

VisionVision

Structure of the EyeStructure of the Eye

• TasteTaste– Chemicals from food enter taste bud (chemoreceptor)Chemicals from food enter taste bud (chemoreceptor)

• SmellSmell– Olfactory receptorsOlfactory receptors

in epithelium of in epithelium of

nasal passage (chemoreceptor)nasal passage (chemoreceptor)

Read info aboutRead info about

Drugs, but itDrugs, but it

Is not on the test!Is not on the test!

Endocrine System = Ch 50

Types of Glands

• Exocrine– Secrete non hormonal chemicals into

ducts– Ex: sweat, digestive, salivary, mucous

glands

• Endocrine– Ductless, secrete hormones into

bloodstream or fluid around cells

Functions of Hormones

– Regulate growth, development, behavior & reproduction

Types of Hormones• Hormones: chemicals secreted by cells to influence the activity

of other cells• Amino Acid Based or are Steroid/Thyroid Hormones…review in

text for RG

Amino Acid-Based Hormones

Steroid & Thyroid Hormones

– Lipids – can pass through target cell memb– Bind directly to receptor site in cytoplasm or

nucleus

Other Types of Hormones• Both act “locally”• Prostaglandins

– Produced by many cells rather than endocrine glands– Smooth muscles that line air passages, blood

vessels, intestines– Accumulate in injured areas

• Neuropeptides– Secreted by nervous system– Ex: endorphins

Hypothalamus & Pituitary Gland• Hypothalamus + pituitary gland

= primary regulators of endocrine system

• Control release of many other hormones

• Hypothalamus releases hormones that stimulate or inhibit release of hormones from pituitary gland= temp control

• Pituitary = Growth Hormone

• Links cerebrum w/ spinal cordLinks cerebrum w/ spinal cord

• HypothalamusHypothalamus – hunger, – hunger,

fatigue, anger, body temp. fatigue, anger, body temp.

homeostasis – hormone controlhomeostasis – hormone control

• ThalamusThalamus: relays sensory info : relays sensory info

to cerebral cortexto cerebral cortex

Upper Brain Stem Upper Brain Stem

Hormones Secreted by Pituitary Gland

Thyroid Gland• Near lower part of larynx

• Metabolism

• Heart rate, blood pressure, temp., metabolic rates

Thyroid Gland• Hyperthyroidism: overproduction of

thyroid hormones, overactivity, high blood press., body temp

• Hypothyroidism: lethargy, weight gain, low heart rate– Caused by iodine deficiency = goiter

Adrenal Glands• Above each kidney

– Epinephrine & norepinephrine: nervous system reaction “fight or flight”

– Cause liver to produce glucose increased heart rate, pupils dilate, bronchial tubes enlarge

Gonads• Ovaries/Testes

• Produce steroid sex hormones

• Estrogen/progesterone from ovaries

• Testosterone

Pancreas• Both exocrine & endocrine cells• Endocrine

– Islets of Langerhans– Insulin: absorption of glucose in cells (lowers

blood sugar)– Glucagon: liver releases glucose (increases blood

sugar)

• Type I diabetes, immune cells attack islet cells & require insulin injections

• Type II diabetes: occurs after age 40, obesity, poor diet/exercise

Other Endocrine Glands• Thymus

– Beneath sternum, between lungs, formation of T-cells

• Pineal– Near base of brain, melatonin sleep

patterns

• Parathyroid– In back of thyroid, increase

concentration of calcium ions in blood for bone growth & muscle activity

• Digestive organs– Stomach Gastrin– Small intestine secretin

Homeostasis– Stable internal environment– Antagonistic hormones: opposite effect

• Glucagon/insulin

– Negative Feedback: initial hormone stimulates other hormones that inhibit release of initial hormone – has stabilizing effect

– Positive Feedback: initial hormone stimulates other hormones that stimulate further release of initial hormone

Negative Feedback Mechanisms