overview topic: communications systems: nervous system and endocrine system

Overview Topic:

Communications Systems:

Nervous SystemAnd

Endocrine System

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Santiago Ramon Y. Cajal (1852-1934)Founding Scientist in the Modern Approach toNeuroscience. Received Nobel Prize in 1906

Human Anatomy and Physiology, 7eby Elaine Marieb & Katja Hoehn

Copyright © 2007 Pearson Education, Inc.,publishing as Benjamin Cummings.

Figure 11.1: The nervous system’s functions, p. 388.

Sensory input

Motor output

Integration



Figure 11.2: Levels of organization in the nervous system, p. 389.

Central nervous system (CNS) Brain and spinal cord Integrative and control centers

Sensory (afferent) division Somatic and visceral sensory nerve fibers Conducts impulses from receptors to the CNS

Motor (efferent) division Motor nerve fibers Conducts impulses from the CNS to effectors (muscles and glands)

Autonomic nervous system (ANS) Visceral motor (involuntary) Conducts impulses from the CNS to cardiac muscles, smooth muscles, and glands

Sympathetic division Mobilizes body systems during activity

Parasympathetic division Conserves energy Promotes housekeeping functions during rest

Peripheral nervous system (PNS) Cranial nerves and spinal nerves Communication lines between the CNS and the rest of the body

Somatic nervous System Somatic motor (voluntary) Conducts impulses from the CNS to skeletal muscles

= Structure= Function

Key:

Centralnervoussystem(CNS)

= Sensory (afferent)division of PNS= Motor (efferent)division of PNS

Key: Brain

SpinalcordSkin

Visceral organ

Skeletalmuscle

Peripheral nervous system(PNS)

Motor fiber ofsomatic nervoussystem

Somatic sensoryfiber

Sympatheticmotor fiber of ANS

Parasympatheticmotor fiber of ANS

Visceralsensory fiber

(a)

(b)



Figure 11.3: Neuroglia, p. 390.

(a) Astrocyte

(d) Oligodendrocyte

(e) Sensory neuron with Schwann cells and satellite cells

(b) Microglial cell

(c) Ependymal cells

Schwann cells(forming myelin sheath)

Cell bodyof neuronSatellite cells

Nerve fiber

Capillary

Neuron

Nerve fibers

Myelin sheath

Process ofoligodendrocyte

Fluid-filled cavity

Brain or spinal cord tissue



Figure 11.4: Structure of a motor neuron, p. 392.

(b)

(a)

Dendrites(receptiveregions)

Cell body(biosynthetic centerand receptive region)

Nucleolus

Nucleus

Terminal branches(telodendria)

Nissl bodies

Axon(impulse generatingand conductingregion)

Axon terminals(secretorycomponent)

Axon hillock

Neurilemma(sheath ofSchwann)

Node of Ranvier

Impulsedirection

Schwann cell(one inter-node)

Neuron cell body

Dendriticspine



Figure 11.5: Relationship of Schwann cells to axons in the PNS, p. 394.

(a)

(b)

(c)

(d)

Schwann cellcytoplasm

Axon

NeurilemmaMyelinsheath

Schwann cellnucleus

Schwanncell plasmamembrane

Myelin sheath

Schwann cellcytoplasm

Neurilemma

Axon



Figure 11.6: Operation of gated channels, p. 398.

(a) Chemically gated ion channel

Na+

K+K+

Na+

(b) Voltage-gated ion channel

Na+

Na+

Receptor

Neurotransmitter chemical attached to receptor

Closed Open

Membranevoltagechanges

Closed Open

Chemicalbinds



Figure 11.7: Measuring membrane potential in neurons, p. 399.

Voltmeter

Microelectrodeinside cell

Plasmamembrane

Ground electrodeoutside cell

Neuron

Axon



Figure 11.8: The basis of the resting membrane potential, p. 399.

Na+ Na+

K+

K+

K+

K+

Na+

Na+

Na+

Na+

Cell interiorNa+

15 mMK+

150 mMCl–

10 mM A–

100 mMNa+

150 mMA–

0.2 mM

Cell exterior

K+

5 mM Cl–

120 mM

Cellexterior

Cellinterior

Plasmamembrane

Na+–K+

pumpDif

fusi

on

K+ N

a+D

iffus

ion

-70 mV



Figure 11.9: Depolarization and hyperpolarization of the membrane, p. 400.

Depolarizing stimulus

Mem

bra

ne

po

ten

tial

(vo

ltag

e, m

V)

Time (ms)

0–100

–70

0

–50 –50

+50

1 2 3 4 5 6 7

Hyperpolarizing stimulus

Mem

bra

ne

po

ten

tial

(vo

ltag

e, m

V)

Time (ms)

0 1 2 3 4 5 6 7–100

–70

0

+50

Insidepositive

Insidenegative

(a) (b)

Restingpotential

DepolarizationRestingpotential

Hyper-polarization



Figure 11.10: The mechanism of a graded potential, p. 401.

(b)

Depolarized region Stimulus

Plasmamembrane

Depolarization Spread of depolarization(a)



Figure 11.11: Changes in membrane potential produced by a depolarizing graded potential, p. 402.

Distance (a few mm)

–70Resting potential

Active area(site of initialdepolarization)

Mem

bra

ne

po

ten

tial

(m

V)



Figure 11.12: Phases of the action potential and the role of voltage-gated ion channels, p. 403.

0 1 2 3 4

–70

–55

0

+30

Me

mb

ran

e p

ote

nti

al

(mV

)

Time (ms)

Re

lati

ve

me

mb

ran

e

pe

rme

ab

ilit

y

Na+Na+

K+

K+

Outsidecell

Insidecell

Outsidecell

Insidecell

Depolarizing phase: Na+

channels open

Repolarizing phase: Na+

channels inactivating, K+

channels open

Action potential

PNa

PKThreshold

Na+

Na+

K+K+

Outside cell

Insidecell

Outsidecell

Insidecell

Inactivation gate

Activationgates

Potassiumchannel

Sodiumchannel

Resting state: All gated Na+

and K+ channels closed (Na+ activation gates closed; inactivation gates open)

Hyperpolarization: K+

channels remain open; Na+ channels resetting

2

2

3

4

4

1

11



Figure 11.13: Propagation of an action potential (AP), p. 405.

–70

+30

(a) Time = 0 ms (b) Time = 2 ms (c) Time = 4 ms

Voltageat 2 ms

Voltageat 4 ms

Voltageat 0 ms

Resting potential

Peak of action potential

Hyperpolarization

Mem

bra

ne

po

ten

tial

(m

V))



Figure 11.14: Relationship between stimulus strength and action potential frequency, p. 406.

Time (ms)

Vo

ltag

eM

emb

ran

e p

ote

nti

al (

mV

)

–70

0

+30

Threshold

Actionpotentials

Stimulusamplitude



Figure 11.15: Refractory periods in an AP, p. 406.

Stimulus

Mem

bra

ne

po

ten

tial

(m

V)

Time (ms)

–70

0

+30

0 1 2 3 4 5

Absolute refractoryperiod

Relative refractoryperiod

Depolarization(Na+ enters)

Repolarization(K+ leaves)

After-hyperpolarization



Figure 11.16: Saltatory conduction in a myelinated axon, p. 407.

Node of Ranvier

Cell bodyMyelinsheath

Distalaxon



Figure 11.17: Synapses, p. 409.

(a)

(b)

Cell body

Dendrites

Axon

Axodendriticsynapses

Axoaxonicsynapses

Axosomaticsynapses

Axosomaticsynapses

Soma of postsynaptic neuron

Axon



Figure 11.18: Events at a chemical synapse in response to depolarization, p. 410.

Synaptic vesiclescontaining neurotransmitter molecules

Axon of presynapticneuron

Synapticcleft

Ion channel(closed)

Ion channel (open)

Axon terminal of presynaptic neuron

PostsynapticmembraneMitochondrion

Ion channel closed

Ion channel open

Neurotransmitter

Receptor

Postsynapticmembrane

Degradedneurotransmitter

Na+

Na+

Ca2+

Action P

otential

1

2

34

5



Figure 11.19: Postsynaptic potentials, p. 412.

Threshold

Mem

bra

ne

po

ten

tial

(m

V)

Time (ms)

+30

0

–70

–55

10 20

(a) Excitatory postsynaptic potential (EPSP)

Threshold

Mem

bra

ne

po

ten

tial

(m

V)

Time (ms)

+30

0

–70

–55

10 20

(b) Inhibitory postsynaptic potential (IPSP)



Figure 11.24: Types of circuits in neuronal pools, p. 422.

(a) Divergence in same pathway

(e) Reverberating circuit

(f) Parallel after-discharge circuit

(b) Divergence to multiple pathways

(c) Convergence, multiple sources

(d) Convergence, single source

Input Input

Output Output

Input

OutputInput

Output

Input 1

Input 2 Input 3

Output

OutputInput



Figure 11.25: A simple reflex arc, p. 423.

Stimulus

Response

Receptor

Effector

Sensory neuron

Motor neuron

Integrationcenter

Spinal cord (CNS)

Interneuron

Arnold Adolph Berthold 1803 – 1861Founder of Endocrinology

Berthold’s Experiment in Roosters….

Castration Castration &Reimplantationof testis

Castration &Transplantationof testis

Berthold’s Conclusion...

-A secretory, blood-borne product of the transplanted testesis responsible for the normal development of the birds in thesecond and third group

Today, it is called TESTOSTERONE

-’problem’: no one knows why Berthold did the experiment in the first place…. No clear rationale for it.



Figure 16.1: Location of the major endocrine organs of the body, p. 605.

Pineal glandHypothalamus

Pituitary gland

Thyroid gland

Parathyroid glands(on dorsal aspectof thyroid gland)

Thymus gland

Adrenal glands

Pancreas

Ovary(female)

Testis(male)



Figure 16.3: PIP second-messenger mechanism of amino acid-based hormones, p. 608.

PIP2

IP3

ReceptorGTP

GTP

CatecholaminesTRHADHGnRHOxytocin

Triggers responses of target cell

GDP

Extracellular fluid

Cytoplasm

Inactiveprotein kinase C

Activeprotein kinase C

Phospholipase C

Gq

Ca2+ Ca2+-calmodulin

Hormone

Endoplasmicreticulum

DAG

GTP

1

2 34 5

5

6



Figure 16.4: Direct gene activation mechanism of steroid hormones, p. 609.

Steroidhormone

Steroidhormone

Cytoplasm

Receptor-chaperonincomplex

Molecularchaperones

Receptor-hormonecomplex

Hormoneresponseelements

Binding

Transcription Chromatin

mRNA

Nucleus

New protein

Translation

Ribosome

mRNA



Figure 16.5: Three types of endocrine gland stimuli, p. 612.

Capillary blood contains lowconcentration of Ca2+, whichstimulates…

Capillary(low Ca2+ in blood)

Parathyroidglands

Thyroid gland(posterior view)

PTH

Parathyroidglands

…secretion of parathyroid hormone (PTH) by parathyroidglands

Humoral

CNS(spinal cord)

Medulla ofadrenalgland

Preganglionic SNS fiber stimulatesadrenal medulla cells…

PreganglionicSNS fiber

…to secrete catecholamines

Capillary

Neural

Hypothalamus

Thyroidgland

Adrenalcortex

The hypothalamus secretes hormones that…

…stimulatethe anteriorpituitary glandto secretehormonesthat…

Hormonal

Gonad(Testis)

Pituitarygland

…stimulate other endocrine glandsto secrete hormones

(a) (b) (c)

1 1 1

2

32

2



Figure 16.6: Relationships of the pituitary gland and hypothalamus, p. 613.

Neuronsin the ventralhypothalamus

Hypothalamicneurons in thesupraoptic nuclei

Hypothalamicneurons in theparaventricular nuclei

Hypophyseal portal system

Anterior lobe

Venule

Infundibulum(connecting stalk)

Neurohypophysis(storage area forhypothalamichormones)

Posteriorlobe

Venule

Hypothalamic-hypophyseal tract

Inferiorhypophysealartery

OxytocinADH

TSH, FSH, LH, ACTH, GH, PRL

Superiorhypophysealartery

Secretory cells ofadenohypophysis

• Primary capillary plexus• Hypophyseal portal veins• Secondary capillary plexus



Figure 16.7: Metabolic actions of growth hormone (GH), p. 615.

Growth hormone

Feedbackmechanism Inhibits GH synthesis

and release

Anteriorpituitary

Liver andother tissues

Insulin-like growthfactors (IGFs)

Indirectgrowth-promotingactions

Anti-insulinactions

Extraskeletaleffects

Skeletal effects Fat Carbohydratemetabolism

Increased cartilageformation andskeletal growth

Increased proteinsynthesis, andcell growth andproliferation

Increasedlipolysis

Increased bloodglucose and otheranti-insulin effects

Direct effects

Hypothalamussecretes growthhormone – releasinghormone (GHRH), andsomatostatin (GHIH)

Key:

Increases, stimulates

Reduces, inhibits

Initial stimulus

Physiological response

Result

Inhibits GHRH releaseStimulates GHIH release



Figure 16.8: Gross and microscopic anatomy of the thyroid gland, p. 620.

(a) (b)

Hyoid bone

Thyroid cartilage

Internal carotidartery

Common carotidartery

Epiglottis

External carotidarterySuperior thyroidartery

Isthmus ofthyroid gland

Left subclavianarteryLeft lateral lobeof thyroid gland

Inferior thyroidartery

Trachea

BrachiocephalicarteryAorta

Colloid-filledfollicles Follicle cells

Parafollicular cell



Figure 16.11: The parathyroid glands, p. 624.

(a) (b)

Pharynx(posterioraspect)

Thyroidgland

Parathyroidglands

Trachea

Esophagus

Capillary

Chiefcells

Oxyphilcells



Figure 16.12: Effect of parathyroid hormone on bone, the intestine, and the kidneys, p. 625.

Hypocalcemia (low bloodcalcium) stimulatesparathyroid glands

PTH release fromparathyroid glands

Rising Ca2+ inblood inhibitsPTH release

Activatesosteoclasts;calcium andphosphateions releasedinto blood

Increasescalciumabsorptionfrom food

Promotes activationof vitamin D

Increasescalciumreabsorption

Bone

Intestine

Kidney

PTH:

Blood-stream

= Ca2+ ions

= PTH molecules

Key:



Figure 16.13: Microscopic structure of the adrenal gland, p. 626.

(a) (b)

• Cortex

Kidney

• Medulla

Adrenal gland

CapsuleZona

glomerulosa

Zonafasciculata

Zonareticularis

Adrenalmedulla



Figure 16.16: Stress and the adrenal gland, p. 631.

Short term More prolongedStress

Hypothalamus

Nerve impulses

Adrenalcortex

CRH (corticotropin-releasing hormone)

Corticotrophcells ofanteriorpituitary

To target in blood

ACTH

Mineralocorticoids Glucocorticoids

1. Retention of sodium and water by kidneys2. Increased blood volume and blood pressure

1. Proteins and fats converted to glucose or broken down for energy2. Increased blood glucose3. Suppression of immune system

Long-term stress response

Short-termstress response

Spinal cord

Adrenalmedulla

Preganglionicsympatheticfibers

Catecholamines(epinephrineand norepinephrine)

1. Increased heart rate2. Increased blood pressure3. Liver converts glycogen to glucose and releases glucose to blood4. Dilation of bronchioles5. Changes in blood flow patterns leading to decreased digestive system activity and reduced urine output6. Increased metabolic rate



Figure 16.18: Regulation of blood glucose levels by insulin and glucagon, p. 633.

Stimulatesglycogenbreakdown

GlycogenGlucose

Liver

Stimulatesglycogenformation

Stimulatesglucose uptakeby cells

Tissue cells

Stimulus:Rising blood glucose level

Homeostasis: Normal blood glucose level (about 90 mg/100 ml)

Stimulus:Declining bloodglucose level

Bloodglucoserises tonormalrange

Bloodglucosefalls tonormalrange

Glucagon

Pancreas

Insulin

GlycogenGlucose

Liver

Pancreas

Imbalance

Imbalance



Figure 16.1: Modified to emphasize the relationship between the adrenal glands and the testes and ovaries.

Adrenal glands

Ovary(female)

Testis(male)

Testes & Ovaries

These gamete producing glands produce the lion’s share of sex hormone for each sex. Ovaries are in females and Testes are in

males. There is, however, an important role for the adrenal

glands…

overview topic: communications systems: nervous system and endocrine system

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