hormone and nervous system biolove
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BIOLOVE
ENDOCRINE SYSTEM AND NERVOUS SYSTEM
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HORMONE CLASSES
steroidglucocortisoids
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 ofactions
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 receptorprotein (at cytoplasm or in
nucleus)
2. Form Hormone receptor complex(HCR)
3. Activated hormone receptorcomplex will bin to specific region
in DNA
4. Results in transcription of generegion into mRNA
5. Translation mRNA transcripthappen outside the nucleus
6. Results in formation of enzymeand 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 atcells surface
2. Trigger activation of 2messenger, cAMP by cAMP
synthesizing enzyme with the
help of ATP
3. cAMP activate inactiveenzyme
4. enzyme catalysed conversionof reactant to products
Flow
BindcAMPactivate enzymeconversion
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The hormone epinephrine Has multiple effects in mediating the bodys response to short-term stress
The hypothalamus and pituitary integrate many functions of the vertebrate endocrinesystem
The hypothalamus and the pituitary gland Control much of the endocrine system
Pituitary gland is regulated by:1. Nervous system2. Endocrine system
Pituitary gland called as MASTER GLAND
- Because control activity of other glandsSome of these cells in hypothalamus produce direct-acting hormones
- That are stored in and released from the posterior pituitary, or neurohypophysis
Neuroendocrine s stem
The two hormones released from the posterior pituitary Act directly on nonendocrine tissues Oxytocin
o Induces uterine contractions and milkejection
Antidiuretic hormone (ADH)o Enhances water reabsorption in the
kidneys
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Other hypothalamic cells produce tropic hormonesThat 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 tissueo To stimulate release of hormone(s) with direct metabolic or developmental
effects
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The nontropic hormones produced by the anterior pituitary includeo Prolactin
Prolactin stimulates lactation in mammalso But has diverse effects in different vertebrates
Growth hormone (GH)/somatotropin
o Promotes tissue growth directly and has diverse metabolic effectso Promote protein synthesiso 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 thyroidgland
Stimulates Ca2+ depositionin the bones and secretion
by the kidneys, thus
lowering blood Ca2+
levels
PTH, secreted by the parathyroidglands
Has the opposite effects onthe 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 glucoselevels by
Promoting the cellularuptake of glucose
Slowing glycogenbreakdown in the liver
Promoting fat storage Glucagon increases blood glucose
levels by
Stimulating theconversion of glycogen to
glucose in the liver
Stimulating thebreakdown of fat and
protein into glucose
Diabetes mellitus, perhaps thebest-known endocrine disorder
Is caused by a deficiencyof insulin or a decreasedresponse to insulin in
target tissues
Is marked by elevatedblood glucose levels
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The adrenal medulla secretes epinephrine and norepinephrine (a.k.a adrenaline andnoradrenaline)
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 action2. Paling or flushing, or alternating between both3. Inhibition of stomach and upper-intestinal action to the point where digestion slows
down or stops
4. General effect on the sphincters of the body5. Constriction of blood vessels in many parts of the body6. Liberation of nutrients (particularly fat and glucose) for muscular action7. Dilation of blood vessels for muscles8. Inhibition of the lacrimal gland (responsible for tear production) and salivation9. Dilation of pupil (mydriasis)10.Relaxation of bladder11.Inhibition of erection12.Auditory exclusion (loss of
hearing)
13.Tunnel vision (loss of peripheralvision)
14.Disinhibition of spinal reflexes15.Shaking
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Hormones from the adrenal cortex Also function in the bodys 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 gonadstestes and ovaries
Produce most of the bodys sex hormones:androgens, estrogens, and progestins
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Androgen: testosterone
Which stimulate the development and maintenance of the male reproductivesystem
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 ofdistinct 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 nervoussystem concentrated at head
end
2. Centralization Has centralnervous 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 sensorsa. That detect external stimuli and internal conditions
2 Sensory information is sent to the CNSa. Where interneurons integrate the information
3 Motor output(motor function) leaves the CNS via motor(efferent) neuronsa. 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 informationb. 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 system2. Function to receive and send information3. Information is in form of electrical signals called nerve impulse
Most of a neurons 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 sensoryreceptors 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 neurons2. Remove waste3. 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 concentration2. Sodium-potassium pump3. Ion leak channel
Ionic concentration
- Molecules such as carbohydrate, protein and nucleic acid are negative charged- Cannot pass the PM- Called fixed anions
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Sodium potassium pump
The concentration of Na+ is higher in theextracellular 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 restOR
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 openWhat 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 whenexcitation occurs
oIs a brief all-or-none depolarization of a neurons 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 systemo 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 sensoryreceptor of all
body to the CNS
motor(efferent)pathways
carry impulse fromCNS 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.