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BIOLOVE

ENDOCRINE SYSTEM AND NERVOUS SYSTEM

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HORMONE CLASSES

steroid glucocortisoids

mineralcortisoids

Fatty acids

derivatives

prostaglandin

juvenile hormone

amino acid

derivatives

noradrenaline

adrenaline

thyroxine

protein

and

peptide

peptide

- oxytocin

-PTH

-calcitonin

-ADH

proteins

-insulin

-glucagon

-FSH

-LH

-prolactin

Peptide hormones are shorter than proteins

Protein hormone consist of one or more polypeptide

These hormones released by endocrine glands into

blood and from blood to target cell where response

occur.

Endocrine glandbloodtarget cellresponse

Adrenaline, noradrenaline and thyroxine are from amino

acid thyrosine

Adrenaline, noradrenaline = epinephrine/norepinephrine

Prostaglandins in human

Juvenile hormone in insects

Bothe derived from arachidonic acid (20 C fatty acids)

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Neurosecretory cell

- Neuron/nerve cell

- Translate neural signal into chemical stimuli

Type of hormonal control pathways

Mechanism of Hormone Actions

mechanisms of actions

steroid

(lipid soluble)

non-steroid

(water soluble)

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Steroid hormones are able to enter the cell

Why?

- Because lipid portion of the PM does not act as a barrier for lipophilic regulators

- Steroid is lipophilic

Steroid hormones

- Cannot dissolve in blood plasma

- Need transport protein

- Always attach to protein carrier

Mechanism of steroid hormones

Flow

BindHRCactivated HRCbind on gene

regiontranscription into mRNAtranslation of mRNA

New protein and enzyme

1. Hormone combine with receptor

protein (at cytoplasm or in

nucleus)

2. Form Hormone receptor complex

(HCR)

3. Activated hormone receptor

complex will bin to specific region

in DNA

4. Results in transcription of gene

region into mRNA

5. Translation mRNA transcript

happen outside the nucleus

6. Results in formation of enzyme

and other protein

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Mechanism of non-steroid hormones

This kind of mechanism is enzyme mediated

• Signaling by any of these molecules(steroid and non-steroid) involves three key events

– Reception

Bind to receptor

– Signal transduction

– Response

Action of enzyme

Reactant to product

The same hormone may have different effects on target cells that have

Different receptors for the hormone

Different signal transduction pathways

Different proteins for carrying out the response

Non-steroid hormone cannot pass

the PM

1. Hormone bind to receptor at

cell’s surface

2. Trigger activation of 2°

messenger, cAMP by cAMP

synthesizing enzyme with the

help of ATP

3. cAMP activate inactive

enzyme

4. enzyme catalysed conversion

of reactant to products

Flow

BindcAMPactivate enzymeconversion

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• The hormone epinephrine

– Has multiple effects in mediating the body’s response to short-term stress

• The hypothalamus and pituitary integrate many functions of the vertebrate endocrine

system

• The hypothalamus and the pituitary gland

– Control much of the endocrine system

• Pituitary gland is regulated by:

1. Nervous system

2. Endocrine system

Pituitary gland called as MASTER GLAND

- Because control activity of other glands

Some of these cells in hypothalamus produce direct-acting hormones

- That are stored in and released from the posterior pituitary, or neurohypophysis

Neuroendocrine system

• The two hormones released from the posterior pituitary

– Act directly on nonendocrine tissues

– Oxytocin

o Induces uterine contractions and milk

ejection

– Antidiuretic hormone (ADH)

o Enhances water reabsorption in the

kidneys

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• Other hypothalamic cells produce tropic hormones

That are secreted into the blood and transported to the anterior pituitary or adenohypophysis

• The anterior pituitary

– Is a true-endocrine gland

• The tropic hormones of the hypothalamus

– Control release of hormones from the anterior pituitary

• The anterior pituitary

– Produces both tropic and nontropic hormones

– The four strictly tropic hormones are

o Follicle-stimulating hormone (FSH)

o Luteinizing hormone (LH)

o Thyroid-stimulating hormone (TSH)

o Adrenocorticotropic hormone (ACTH)

– Each tropic hormone acts on its target endocrine tissue

o To stimulate release of hormone(s) with direct metabolic or developmental

effects

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– The nontropic hormones produced by the anterior pituitary include

o Prolactin

– Prolactin stimulates lactation in mammals

o But has diverse effects in different vertebrates

Growth hormone (GH)/somatotropin

o Promotes tissue growth directly and has diverse metabolic effects

o Promote protein synthesis

o Stimulates the production of growth factors by other tissues

– Liver to produce insulin-like growth factors(IGFs)

– IGFs promotes tissues and skeletal growth

The pineal gland, located within the brain

o Secretes melatonin

Figure 1: Pineal Gland

• The thyroid gland

– Consists of two lobes located on the ventral surface of the trachea

– Produces two iodine-containing hormones, triiodothyronine (T3) and thyroxine (T4)

• Release of melatonin

– Is controlled by light/dark cycles

• The primary functions of melatonin

- Influence and control onset of sexual

maturity and biological clock

- Control circadian rythm (24 hour cycle)

• The thyroid hormones

– Play crucial roles in stimulating

metabolism and influencing

development and maturation

• The thyroid gland also produces calcitonin

– Which functions in calcium

homeostasis

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• Two antagonistic hormones, parathyroid hormone (PTH) and calcitonin

– Play the major role in calcium (Ca2+) homeostasis in mammals

PTH secrete by parathyroid gland at the surface of thyroid gland

Insulin and Glucagon: Control of Blood Glucose

• Two types of cells in the pancreas

– Secrete insulin and glucagon, antagonistic hormones that help maintain glucose

homeostasis and are found in clusters in the islets of Langerhans

• Glucagon

– Is produced by alpha cells

• Insulin

– Is produced by beta cells

• Calcitonin, secreted by the thyroid

gland

– Stimulates Ca2+ deposition

in the bones and secretion

by the kidneys, thus

lowering blood Ca2+ levels

• PTH, secreted by the parathyroid

glands

– Has the opposite effects on

the bones and kidneys, and

therefore raises Ca2+ levels

– Also has an indirect effect,

stimulating the kidneys to

activate vitamin D, which

promotes intestinal uptake

of Ca2+ from food

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• Type I diabetes mellitus (insulin-dependent diabetes)

– Is an autoimmune disorder in which the immune system destroys the beta cells of

the pancreas

• Type II diabetes mellitus (non-insulin-dependent diabetes)

– Is characterized either by a deficiency of insulin or, more commonly, by reduced

responsiveness of target cells due to some change in insulin receptors

Adrenal Glands

• The adrenal glands

– Are adjacent to the kidneys

– Are actually made up of two glands: the adrenal

medulla and the adrenal cortex

• Insulin reduces blood glucose

levels by

– Promoting the cellular

uptake of glucose

– Slowing glycogen

breakdown in the liver

– Promoting fat storage

• Glucagon increases blood glucose

levels by

– Stimulating the

conversion of glycogen to

glucose in the liver

– Stimulating the

breakdown of fat and

protein into glucose

• Diabetes mellitus, perhaps the

best-known endocrine disorder

– Is caused by a deficiency

of insulin or a decreased

response to insulin in

target tissues

– Is marked by elevated

blood glucose levels

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• The adrenal medulla secretes epinephrine and norepinephrine (a.k.a adrenaline and

noradrenaline)

– Hormones which are members of a class of compounds called catecholamines

• These hormones epinephrine and norepinephrine:

– Are secreted in response to stress-activated impulses from the nervous system

– Mediate various fight-or-flight responses

Fight-Or-Flight Responses

Catecholamine hormones, such as adrenaline or noradrenaline, facilitate immediate physical

reactions associated with a preparation for violent muscular action. These include the

following

1. Acceleration of heart and lung action

2. Paling or flushing, or alternating between both

3. Inhibition of stomach and upper-intestinal action to the point where digestion slows

down or stops

4. General effect on the sphincters of the body

5. Constriction of blood vessels in many parts of the body

6. Liberation of nutrients (particularly fat and glucose) for muscular action

7. Dilation of blood vessels for muscles

8. Inhibition of the lacrimal gland (responsible for tear production) and salivation

9. Dilation of pupil (mydriasis)

10. Relaxation of bladder

11. Inhibition of erection

12. Auditory exclusion (loss of

hearing)

13. Tunnel vision (loss of peripheral

vision)

14. Disinhibition of spinal reflexes

15. Shaking

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• Hormones from the adrenal cortex

– Also function in the body’s response to stress

• Adrenal cortex secrete:

• Glucocorticoids, such as cortisol

– Influence glucose metabolism and the immune system

– Promotes the liver to undergo gluconeogenesis to convert amino acid to

glucose

• Mineralocorticoids, such as aldosterone

– Affect salt and water balance

– Maintain proper balance of sodium and potassium ion in kidney tubules

The gonads—testes and ovaries

– Produce most of the body’s sex hormones:

androgens, estrogens, and progestins

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Androgen: testosterone

– Which stimulate the development and maintenance of the male reproductive

system

– Testosterone causes an increase in muscle and bone mass

– And is often taken as a supplement to cause muscle growth, which carries

many health risks

– Estrogens, the most important of which is estradiol

– Are responsible for the maintenance of the female reproductive system and

the development of female secondary sex characteristics

– In mammals, progestins, which include progesterone

– Are primarily involved in preparing and maintaining the uterus

Molting and Metamorphosis

• In insects

– Molting and development are controlled by three main hormones

- Metamorphosis is a development from egg to adult in which there is a series of distinct stages.

- Molting is a process to shed periodically part or all of a coat or an outer covering, such as feathers, cuticle, or skin, which is then replaced by a new growth.

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Nervous System

- All animals except sponges has nervous system

- What differentiate between animals is how the nervous system is organized

Flatworm has small brain composed of Ganglia

Has 2 parallel nerve cords

These 2 are CNS while the others is PNS

Have neurons arranged in nerve nets Has Radial nerve. Nerve net

connect to nerve ring by radial

nerve (uncentralized)

Leech, insect and flatworm has

bilateral nervous system

Bilateral nervous system has:

1. Cephalization – nervous

system concentrated at head

end

2. Centralization – Has central

nervous system(CNS) and

peripheral nervous

system(PNS). But CNS is

different from PNS.

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• Nervous systems in molluscs

– Correlate with the animals’ lifestyles

• Sessile molluscs have simple systems

– While more complex molluscs have more sophisticated systems

Squid has high degree of

cephalization (many nerve at the

head)

Give intelligence

• In vertebrates

– The central nervous system

consists of a brain and dorsal

spinal cord

- The PNS connects to the CNS

• Nervous systems process information in three stages

– Sensory input, integration, and motor output(motor function)

photo 1: Neural Signaling

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1 Sensory(afferent) neurons transmit information from sensors

a. That detect external stimuli and internal conditions

2 Sensory information is sent to the CNS

a. Where interneurons integrate the information

3 Motor output(motor function) leaves the CNS via motor(efferent) neurons

a. Which communicate with effector cells(muscles, glands) for response

Example:

Knee-Jerk Reflex

Integration takes place in the CNS (brain and spinal cord)

- Brain and spinal cord:

a. Receive sensory information

b. Make decisions from the information obtained

Motor output(motor function) is the stimulation of effectors

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Neurons

- Make up nervous tissue

- Also called nerve cells

What is neurons?

1. Functional units of nervous system

2. Function to receive and send information

3. Information is in form of electrical signals called nerve impulse

Most of a neuron’s organelles are located in the cell body

Types of neurons

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Differences between Sensory neuron and Motor neuron

Sensory neuron Motor neuron

Dendrites shorter Dendrite longer

Cell body located in the middle of axon Cell body located at upper axon

Transmit message from sensory receptors to CNS

Transport message from CNS to effectors

- Interneurons connect neuron to neuron

• Most neurons have dendrites

– Highly branched extensions that receive signals from other neurons

• The axon is typically a much longer extension

– That transmits signals to other cells at synapses

– That may be covered with a myelin sheath

• Glia are supporting cells

– That are essential for the structural integrity of the nervous system and for

the normal functioning of neurons

• Oligodendrocytes (in the CNS) and Schwann cells (in the PNS)

– Are glia that form the myelin sheaths around the axons of many vertebrate

neurons

Glia alson known as Neuroglia

Functions:

1. Supplies nutrients to neurons

2. Remove waste

3. Provide immune function

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Neurons Transmission of Impulse

• Across its plasma membrane, every cell has a voltage

– Called a membrane potential

• The inside of a cell is negative

– Relative to the outside

• The unequal distribution of charge is called as Electrical Gradient

– Electrical gradient is called as potential difference

• The membrane potential of a cell can be measured

• In all neurons, the differences in charge depends on:

1. Ionic concentration

2. Sodium-potassium pump

3. Ion leak channel

Ionic concentration

- Molecules such as carbohydrate, protein and nucleic acid are negative charged

- Cannot pass the PM

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- Called fixed anions

Sodium potassium pump

• The concentration of Na+ is higher in the

extracellular fluid than in the cytosol

– While the opposite is true for K+

• Pumps out three Na+ and pump out two K+

• Help to maintain concentration gradient

Ion leak channels

• Membrane protein that is more numerous for K+ than Na+

• Allows little Na+ to diffuse in

• Allows more K+ to diffuse out

• So more negative ions will remained in the cytoplasm

The resting potential

– Is the membrane potential when a cell at rest

OR

• The resting potential

– Is the membrane potential of a neuron that is not transmitting signals

Voltage: -65mV to -70mV

Why negative: inside cell more negative charge

Treshold potential

When stimulus id applied, voltage rise to point called as treshold potential

- About -50mV

- Only about 2 to 3 seconds

What is treshold potential?

- Membrane potential that must be reached before all membrane channel can open

What membrane channel?

- Sodium ion and potassium ion channels

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Action potential

- Change in membrane potential occuring in nerve, muscleor other excitable tissues when

excitation occurs

o Is a brief all-or-none depolarization of a neuron’s plasma membrane

o Is the type of signal that carries information along axons

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

o Are involved in the production of an action potential

• When a stimulus depolarizes the membrane

o Na+ channels open, allowing Na+ to diffuse into the cell

• As the action potential subsides

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

• A refractory period follows the action potential

o During which a second action potential cannot be initiated

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• An action potential can travel long distances

– By regenerating itself along the axon

• At the site where the action potential is generated, usually the axon hillock

– An electrical current depolarizes the neighboring region of the axon membrane

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• The speed of an action potential

– Increases with the diameter of an axon

• In vertebrates, axons are myelinated(has myelin sheath)

– Also causing the speed of an action potential to increase

• Action potentials in myelinated axons

– Jump between the nodes of Ranvier in a process called saltatory conduction

Action potential is all-or-none event. Whether treshold is reach to produce action potential or

treshold is not reached causing no action potential at all.

Neurons Communication

Neurons communicate with other cells at synapses

• In an electrical synapse

– Electrical current flows directly from

one cell to another via a gap junction

• The vast majority of synapses

– Are chemical synapses

• In a chemical synapse, a presynaptic neuron

– Releases chemical

neurotransmitters, which are stored

in the synaptic terminal

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• When an action potential reaches a terminal

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

• The process of direct synaptic transmission

– Involves the binding of neurotransmitters to ligand-gated ion channels

• Neurotransmitter binding

– Causes the ion channels to open, generating a postsynaptic potential

• After its release, the neurotransmitter

– Diffuses out of the synaptic cleft

– May be taken up by surrounding cells and degraded by enzymes

Summary of the process:

1. Action potential arrived at synaptic cleft will trigger the opening of Ca2+ channel.

2. Ca2+ enter the channel rapidly.

3. The fusion of Ca2+ will act as stimulus for the presynaptic neuron vesicles to fuse within its

own outer membrane(presynaptic membrane).

4. The vesicle content(neurotransmitter) will be released by exocytosis into synaptic cleft.

5. Neurotransmitter will bind to receptor protein on the surface of postsynaptic membrane.

6. The binding will cause ion channel to open and ion diffuse into receiving cell. The diffusion

will trigger new action potential.

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Neurotransmitter

• Acetylcholine

– Is one of the most common neurotransmitters in both vertebrates and invertebrates

– Can be inhibitory or excitatory

• Inhibitory neurotransmitter

- Open channel for another ion such as Cl- .

- No action potential.

- Triggering hyperpolarization.

• Excitatory neurotransmitter

- Open Na+ channel. Thus triggering action potential

- Promotes depolarization

The vertebrate nervous system is regionally

specialized

- In all vertebrates, the nervous system

o Shows a high degree of cephalization and

distinct CNS and PNS components

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CNS consist of Cranial nerve and Spinal nerve

• The cranial nerves originate in the brain

– And terminate mostly in organs of the head and upper body

• The spinal nerves originate in the spinal cord

– And extend to parts of the body below the head

The PNS can be divided into two functional components

Motor division can be divided into The somatic nervous system and the autonomic nervous system

• The somatic nervous system (allows us to control – voluntary)

– Carries signals to skeletal muscles

• The autonomic nervous system (system control – involuntary)

– Regulates the internal environment, in an involuntary manner

– Is divided into the sympathetic, parasympathetic, and enteric divisions

• The sympathetic and parasympathetic divisions

– Have antagonistic effects on target organs

PNS

sensory(afferent) pathways

from sensory receptor of all

body to the CNS

motor(efferent) pathways

carry impulse from CNS to effector

Motor pathways

(efferent)

Not in syllabus

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• The sympathetic division

– Correlates with the “fight-or-flight” response

• The parasympathetic division

– Promotes a return to self-maintenance functions

– Slows body functions, thus conserving energy

• The enteric division

– Controls the activity of the digestive tract, pancreas, and gallbladder

– speeds body functions, thus increasing energy use.

• This two system has opposite effect

- If one is activated, another one is inhibited

Endocrine VS Nervous system

Categories Endocrine system Nervous system

Nature of messages Chemical signals Electrical signals

Speed of message quite slow because it needs to be transported by blood to specific target sites

really fast due to saltatory conduction

Speed of response Slower speed Rapid speed

Duration of effect Longer duration of effect Shorter duration of effect

Accuarcy of message Precise Diffuse

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References

BIOL2060: Cell Biology. (n.d.). Memorial University. Retrieved from

http://www.mun.ca/biology/desmid/brian/BIOL2060/CBhome.html

Campbell, N. A., Reece, J. B., Urry, L. A., Cain, M. L., Wasserman, S. A., Minorsky, P. V., &

Jackson, R. (2008). Biology. San Francisco: Pearson, Benjamin Cummings.