ASSIGNMENT OF ORGANIC CHEMISTRY
ROLL NO: 5366 (108)
SEMESTER: III FINAL
TOPIC: CARBOXYLIC ACID
SESSION:2011-2014
DISCIPLINE: CHEMISTRY MAJOR
SUBMITTED BY: TEHMINA SHEHZADI
SUBMITTED TO: MRS RAISA KHANUM
GOVT COLLEGE FOR WOMEN
GULBERG LAHORE
ASSIGNMENT OF ENGLISH
ROLL NO: 5366 (108)
SEMESTER: III FINAL
TOPIC: REPORT ON GORILA
SESSION: 2011-2013
DISCIPLINE: CHEMISTRY MAJOR
SESSION: 2011-2015
SUBMITTED BY: TEHMINA SHEHZADI
SUBMITTED TO: MRS FASEEHA
GOVT COLLEGE FOR WOMEN
GULBERG LAHORE
Invertebrate Nervous Systems
Porifera and the Origins of Neurons
NERVOUS SYSTEM OF PORIFERA
Neurons, the cellular components of brains and nervous systems, share the ability
to send and receive information through the use of electrical impulses, usually with
the aid of synapses that connect neurons to each other and emit chemical signals
known as neurotransmitters. Neurons are unique to animals, but certain animals,
such as those in the phyla Porifera and Placozoa, lack neurons. However, this does
not prevent these animals from actively interacting with their environments, and
these organisms can provide insight into the origins of neurons. Although sponges
lack neurons, they can use ion channels to conduct electrical signals through their
body and generate coordinated behaviors in a pre-neural manner Demosponges are
known to go through rhythmic changes in body size, and some species can rapidly
contract their openings and body size in response to stimulation. Although
hexactenellid (or glass) sponges cannot contract like many demosponges, they can
stop the beating of their flagella, halting the process of water intake.
Hexactenellids might also be capable of responding to light by using their spicule
skeleton as optical glass fibers. The idea that neural precursors exist in sponges is
supported by genetic evidence.
Cnidarians
Although the invertebrate nervous system is usually much simpler than the
nervous systems found in vertebrates, there is still a broad range in
complexity depending on the type of invertebrate.
NERVOUS SYSTEM OF CNIDARIA
The simplest type of nervous system is found in hydras and jellyfish
(cnidarians) and is referred to as a "nerve net." Nerve nets do not have
distinct central or peripheral regions, and lack anything that resembles a
brain. Instead, the scattered nerve cells form loose networks in each cell
layer of the body wall. Some of these neurons carry information from
sensory organs that detect touch, light, or other changes in the
environment. These neurons in turn contact neurons that control
movement of the organism, such as swimming.Both ctenophores and
cnidarians lack a centralized nervous system, and instead have multiple broad
“nerve nets” that are identifiable by distinct neurotransmitters Ctenophore neurons
can connect using any part of the cell body (and do so using a “pre-synaptic triad”
consisting of synaptic vesicles, the endoplasmic reticulum, and one or several
mitochondria .Genomic data supports the hypothesis that these simple nervous
systems are related to the more complex systems of other organisms. The genome
of the sea anemone Nematostella vecensis includes genes that code for a variety of
and other animals suggest that all neurons derive from one or a few cellular
common ancestors.
Annelids
NERVOUS SYSTEM OF EARTHWORM
The brain generally forms a ring round the pharynx ,consisting of a pair of ganglia
above and in front of the pharynx, linked by nerve cords either side of the pharynx
to another pair of ganglia just below and behind it. The brains of polychaetes are
generally in the prostomium, while those of clitellates are in the peristomium or
sometimes the first segment behind the peristomium. In some very mobile and
active polychaetes the brain is enlarged and more complex, with visible hindbrain,
midbrain and forebrain sections. The rest of the central nervous system is generally
"ladder-like", consisting of a pair of nerve cords that run through the bottom part of
the body and have in each segment paired ganglia linked by a transverse
connection. From each segmental ganglion a branching system of local nerves runs
into the body wall and then encircles the body. However, in most polychaetes the
two main nerve cords are fused, and in the tube-dwelling genus Owenia the single
nerve chord has no ganglia and is located in the epidermis.
As in arthropods, each muscle fiber is controlled by more than one neuron, and the
speed and power of the fiber's contractions depends on the combined effects of all
its neurons. Most annelids' longitudinal nerve trunks include giant the output
signal line axons.
MOLLUSCA
NERVOUS SYSTEM OF SQUID
A distinct separation of peripheral and central nervous systems is found in
invertebrates such as worms, insects, and mollusks, like the squid. Neuron
cell bodies are grouped into clusters called ganglia, which are usually
located along the animal's midline. The peripheral component of the
nervous system is formed by the extensions of the cells in these ganglia;
some carry sensory information from the environment to the ganglia, while
others carry signals from the ganglia to produce a response. To coordinate
the segments, these ganglia are connected to each other in a chainlike
fashion by a nerve cord, which is a bundle of neurons that runs the length
of the animal. Some organisms have more than one nerve cord connected
by transverse nerves, resembling a ladder.
In many invertebrates, the nerve cord is enlarged at the anterior end of
the organism. The presence of a brain allows the organism to receive a wide
array of information from the environment, analyze it, and generate a
coordinated and complex response. For example, the large brain of a squid
enables it to process visual information and rapidly generate coordinated
responses to capture prey. In fact, this invertebrate nervous system is so
specialized, it closely resembles some vertebrate nervous systems.
PLATYHELMENTHESIS
NERVOUS SYSTEM OF PLANARIA
At the head of the planarian there is a ganglion under the eyespots. This bi-lobed
mass of nerve tissue, the cerebral ganglia, is sometimes referred to as the
planarian brain and has been shown to exhibit spontaneous electrophysiological
oscillations, similar to the electroencephalographic activity of other animals. From
the ganglion there are two nerve cords which extend the length of the tail. There
are many transverse nerves connected to the nerve cords extending from the
brain, which makes the nerve system look like a ladder. With a ladder-like nerve
system, it is able to respond in a coordinated manner. The planarian has a soft,
flat, wedge-shaped body that may be black, brown, gray, or white. The blunt,
triangular head has two ocelli (eyespots), pigmented areas that are sensitive to
light. There are two auricles (earlike projections) at the base of the head, which
are sensitive to touch and the presence of certain chemicals. The mouth is located
in the middle of the underside of the body, which is covered with cilia (hairlike
projections). There are no circulatory or respiratory systems; oxygen entering and
carbon dioxide leaving the planarian's body diffuses through the body wall.
ARTHROPODA
NERVOUS SYSTEM OF ARTHROPODS
Living arthropods have paired main nerve cords running along their bodies below
the gut, and in each segment the cords form a pair of ganglia from which sensory
and motor nerves run to other parts of the segment. Although the pairs of ganglia
in each segment often appear physically fused, they are connected by
commissures (relatively large bundles of nerves), which give arthropod nervous
systems a characteristic "ladder-like" appearance. The brain is in the head,
encircling and mainly above the esophagus. It consists of the fused ganglia of the
acron and one or two of the foremost segments that form the head – a total of
three pairs of ganglia in most arthropods, but only two in chelicerates, which do
not have antennae or the ganglion connected to them. The ganglia of other head
segments are often close to the brain and function as part of it. In insects these
other head ganglia combine into a pair of subesophageal ganglia, under and
behind the esophagus. Spiders take this process a step further, as all the
segmental ganglia are incorporated into the subesophageal ganglia, which occupy
most of the space in the cephalothorax (front "super-segment").
ECHINODERMATA
STARFISH
Unlike the hydras and jellyfish, invertebrates such as sea stars (echinoderms)
display some centralized organization of the nervous system. A ring of neurons is
located in the center of the sea star, and simple bundles of neurons called radial
nerves extend from the ring to the tip of each arm. In each arm, extensions of the
radial nerves form nerve nets as in the jellyfish. This arrangement permits
coordinated movement of each arm and the tube feet located on the surface of the
arm.
They have a simple radial nervous system that consists of a modified nerve net —
interconnected neurons with no central brain (although some do possess ganglia).
Nerves radiate from central rings around the mouth into each arm or along the
body; the branches of these nerves coordinate the movements of the organism.
Invertebrate Intelligence
Because of the difficulty in directly comparing brain activity between
evolutionarily distant animals, as well as the difficulty of defining “intelligence”,
scientists are often hesitant to describe invertebrate behaviors in terms of
intelligence. However, if we think about intelligence as an organism’s ability to
adaptively respond to problems, there is clearly varying degrees of intelligence
throughout the invertebrate world. Indeed, the field of invertebrate cognition has
grown in the last few decades, and much progress has been made.
Animals without nerves or central nervous systems can actively interact with the
environment, although whether these organisms are capable of dynamic learning is
uncertain. The behaviors of sponges were discussed earlier, and cnidarians and
ctenophores can both respond to changes in light and orientation. Cubozoan
cnidarians have eyes with lenses, and despite lacking a brain, are capable of
actively hunting, maneuvering around objects, and responding differently to
different colors.
The capacity to learn has been confirmed and studied in many bilateral groups
including the roundworms molluscs annelid worms arthropods and even the
echinoderms that lack a central nervous system. The most commonly studied form
of learning in invertebrates is associative learning, or the ability to adjust a
behavior through association with a re-occurring stimulus. With advances in
molecular biology, scientists have been able to pinpoint specific neurons and
neurotransmitters that are involved in specific behaviors. Genetic mutants that
produced little dopamine were less likely to learn to associate food rewards with
location when placed in mazes.
TWO FORMS OF COMMUNICATIONIN IN AN ANIMAL
THAT INTEGRATE BODY FUNCTIONS ARE:
NEURONS
HORMONES
A neuron is an electrically excitable cell that processes and transmits
information through electrical and chemical signals. A chemical signal
occurs via a synapse, a specialized connection with other cells. Neurons
connect to each other to form neural networks. Neurons are the core
components of the nervous system, which includes the brain, spinal cord,
and peripheral ganglia. A number of specialized types of neurons exist:
sensory neurons respond to touch, sound, light and numerous other stimuli
affecting cells of the sensory organs that then send signals to the spinal
cord and brain. Motor neurons receive signals from the brain and spinal
cord, cause muscle contractions, and affect glands. Interneurons connect
neurons to other neurons within the same region of the brain or spinal cord.
A typical neuron possesses a cell body (often called the soma), dendrites,
and an axon. Dendrites are thin structures that arise from the cell body,
often extending for hundreds of micrometres and branching multiple times,
giving rise to a complex "dendritic tree".
All neurons are electrically excitable, maintaining voltage gradients across
their membranes by means of metabolically driven ion pumps, which
combine with ion channels embedded in the membrane to generate
intracellular-versus-extracellular concentration differences of ions such as
sodium, potassium, chloride, and calcium. Changes in the cross-membrane
voltage can alter the function of voltage-dependent ion channels. If the
voltage changes by a large enough amount, an all-or-none electrochemical
pulse called an action potential is generated, which travels rapidly along the
cell's axon, and activates synaptic connections with other cells when it
arrives.
TYPES
Neurons exist in a number of different shapes and sizes and can be
classified by their morphology and function. The anatomist Camillo Golgi
grouped neurons into two types; type I with long axons used to move
signals over long distances and type II with short axons, which can often be
confused with dendrites. Type I cells can be further divided by where the
cell body or soma is located. The basic morphology of type I neurons,
represented by spinal motor neurons, consists of a cell body called the
soma and a long thin axon covered by the myelin sheath.
Neurons communicate with one another via synapses, where the axon
terminal or en passant boutons of one cell impinges upon another neuron's
dendrite, soma or, less commonly, axon. Neurons such as Purkinje cells in
the cerebellum can have over 1000 dendritic branches, making
connections with tens of thousands of other cells; other neurons, such as
the magnocellular neurons of the supraoptic nucleus, have only one or two
dendrites, each of which receives thousands of synapses. Synapses can
be excitatory or inhibitory and either increase or decrease activity in the
target neuron. Some neurons also communicate via electrical synapses,
which are direct, electrically-conductive junctions between cells.
In a chemical synapse, the process of synaptic transmission is as follows:
when an action potential reaches the axon terminal, it opens voltage-gated
calcium channels, allowing calcium ions to enter the terminal. Calcium
causes synaptic vesicles filled with neurotransmitter molecules to fuse with
the membrane, releasing their contents into the synaptic cleft. The
neurotransmitters diffuse across the synaptic cleft and activate receptors
on the postsynaptic neuron.
The human brain has a huge number of synapses. Each of the 1011 (one
hundred billion) neurons has on average 7,000 synaptic connections to
other neurons. It has been estimated that the brain of a three-year-old child
has about 1015 synapses.
Mechanisms for propagating action potentials
A signal propagating down an axon to the cell body and dendrites of the next cell
The cell membrane of the axon and soma contain voltage-gated ion
channels that allow the neuron to generate and propagate an electrical
signal (an action potential). These signals are generated and propagated
by charge-carrying ions including sodium (Na+), potassium (K+), chloride
(Cl-), and calcium (Ca2+).
There are several stimuli that can activate a neuron leading to electrical
activity, including pressure, stretch, chemical transmitters, and changes of
the electric potential across the cell membrane. Stimuli cause specific ionchannels within the cell membrane to open, leading to a flow of ions
through the cell membrane, changing the membrane potential.
A hormone is a chemical released by a cell or a gland in one part of the
body that sends out messages that affect cells in other parts of the
organism. Only a little amount of hormone is required to alter cell
metabolism. In essence, it is a chemical messenger that transports a signal
from one cell to another.All multicellular organisms produce hormones;
plant hormones are also called phytohormones. Hormones in animals are
often transported in the blood. Cells respond to a hormone when they
express a specific receptor for that hormone. The hormone binds to the
receptor protein, resulting in the activation of a signal transduction
mechanism that ultimately leads to cell type-specific responses.
Types of chemical messengers
Many animals have a second, slower form of communication - the
endocrine system with its chemical messengers.
Chemical messengers can be categorized as follows:
1. Local chemical messengers.
Many cells secrete chemicals that alter physiological conditions in the
immediate vicinity. Most of these chemicals act on adjacent cells and do
not accumulate in the blood. Hormones produced in the gut that help
regulate digestion. In a wound, a substance called histamine is secreted by
mast cells and participates in the inflammatory response.
2. Neurotransmitter.
acetylcholine that act on immediately adjacent target cells.Messengers
reach high concentrations in the synaptic cleft, act quickly, and are actively
degraded and recycled.
3. Neuropeptides.
Some specialized neurons secrete neuropeptides.Neuropeptides enter the
bloodstream or other body fluids and are transported to nonadjacent target
cells where they exert their effects. In mammals, for example, certain nerve
cells in the hypothalamus release a neuropeptide that causes the pituitary
gland to release the hormone oxytocin, which induces powerful uterine
contractions during the delivery of offspring.
4. Hormones.
Endocrine glands or cells secrete hormones that are transported by the
bloodstream to nonadjacent target cells.
5. Pheromones.
Pheromones are chemical messengers released to the exterior of one
animal that affect the behavior of another individual of the same species.
Two basic mechanisms are involved
FIX MEMBRANE RECEPTORS MECHANISM
The first, the fixed membrane receptor mechanism, applies to hormones
that are proteins or amines.
Because they are water soluble and cannot diffuse across the plasma
membrane, these hormones initiate their response by means of specialized
receptors on the plasma membrane of the target cell. The e mobile
receptor mechanism applies to steroid hormones. These hormones are
lipid soluble and diffuse easily into the cytoplasm,, where they initiate their
response by binding to cytoplasmic receptors. Binding to a specific receptor
site for that hormone on the plasma membrane. The hormone receptor
complex activates the enzyme adenylate cyclase in the membrane. The
activated enzyme converts ATP into a nucleotide called cyclic AMP, which
will become the second or intracellular messenger. Cyclic AMP diffuses
throughout the cytoplasm and activates an enzyme called protein kinase,
which causes the cell to respond with its distinctive physiological activity.
After inducing the target cell to perform its specific function; cyclic AMP is
inactivated by the enzyme phosphodiesterase.
MOBILE RECEPTORS MECHANISM
The mobile receptor mechanism involves the stimulation of protein
synthesis.This newly formed hormone receptor complex acquires an affinity
for DNA that causes it to enter the nucleus of the cell, where it binds to
DNA and regulates the transcription of specific genes to form messenger
RNA.The newly transcribed mRNA leaves the nucleus and moves to the
rough endoplasmic reticulum, where it initiates protein synthesis.
Chemicals regulating growth, maturation, and reproduction were among the
first hormones to appear during the course of animal evolution.
SOME HORMONES OF INVERTEBRATES
Porifera - None
Cnidarians - Hydra contain a neuropeptide that stimulates budding,
regeneration, and growth.
Platyhelminthes - Neurosecretory cells are known. These cells are
located in the cerebral ganglion and along major nerve cords.The
neuropeptides produced by the cells function in regeneration, asexual
reproduction, and gonad maturation.
Nematodes - Neurosecretory cells associated with the central nervous
system. Controls ecdysis of the old cuticle.
Annelids - well developed endocrine control of physiological function.
Generally involved with morphogenesis, development, growth,
regeneration, and gonadal maturation.
Arthropods - The endocrine system of a crustacean, controls functions
such as ecdysis, sex determination, and color changes-organs are
neurosecretory tissues located in the crayfish eye stalks. Associated with
each X-organ is a sinus gland that accumulates and releases the
secretions of the X-organ.Y-organs, are located at the base if the maxillae.
In the absence of an appropriate stimulus, the X-organ produces moltinhibiting hormone, and the sinus gland releases it. Another hormone,
juvenile hormone, is also involved the morphological differentiation that
occurs during the molting of insects. Located just behind the insect brain
are the paired corpora allata. These structures produce juvenile hormone.
When the concentration of juvenile hormone in the blood of an insect is
high, differentiation is inhibited. In the absence of an appropriate
environmental stimulus, the corpora allata decrease the production of
juvenile hormone, which causes the insect larva to differentiate into the
pupa.
ENDOCRINE SYSTEM OF VERTEBRATE OTHER THAN
BIRDS AND MAMMALS
Vertebrates other than birds or mammals have somewhat similar endocrine
Systems, but differences do exist.
1. Hormones with the same function in deferent species may not be
chemically identical.
2. Certain hormones are species specific with respect to their function;
conversely, some hormones produced in one species may be completely
functional in another species.
3. A hormone from one species may elicit a different response in the same
target cell or tissue of a different species.
In jawed fishes, three major regions have been identified that secrete
neuropeptides.The two in the brain are the pineal gland of the epithalamus
and the preoptic nuclei of the hypothalamus. The pineal gland produces
neuropeptides that affect pigmentation and apparently inhibit reproductive
development. The preoptic nuclei produce various other neuropeptides that
control various functions in fishes. The third major region of fishes that has
neuropeptide function is the urophysis.The urophysis is a discrete structure
in the spinal cord of the tail. The urophysis produces neuropeptides that
help control water and ion balance, blood pressure, and smooth muscle
contraction.,
Function of Endocrine System OF Mammals
•Control of digestive tract & its accessories
•Control of energy production
–Storage, mobilization, interconversion& utilization of metabolic fuels
–Insulin, glucagon, epinephrine, growth hormone, cortisol, thyroxine
•Control of composition and volume of extracellular fluid (ECF)
–ADH, ACTH, aldosterone, cortisol, renin, parathyroid hormone
•Adaptation to hostile environment
–Acclimatization to cold; resistance to infection, noxious agents, stress
–Pituitary, adrenal, and thyroid hormones
•Growth and development
–Practically all
•Reproduction
–Survival of species, not individual member
–Estrogen, progesterone, lutenizing hormone, follicle stimulation
Pituitary Hormones
•Anterior Pituitary
–Growth hormone (GH)
–Adrenal corticotropichormone (ACTH)
–Thyroid stimulating hormone (TSH)
–Follicle stimulating hormone (FSH)
•Poster or Pituitary
–Oxytocin
–Anti-diuretic hormone (vasopressin)
Pituitary -Posterior Lobe
•The posterior lobe is a down growth of hypothalamic neural tissue
•Has a neural connection with the hypothalamus (hypothalamichypophysealtract)
•Nuclei of the hypothalamus synthesize oxytocin and antidiuretichormone
(ADH)
•These hormones are transported to the posterior pituitary
Activity of the Adenophypophysis
•The hypothalamus sends a chemical stimulus to the anterior pituitary
–Releasing hormones stimulate the synthesis and release of hormones
–Inhibiting hormones shut off the synthesis and release of hormones
•The tropic hormones that are released are:
–Thyroid-stimulating hormone (TSH)
–Adrenocorticotropichormone (ACTH)
–Follicle-stimulating hormone (FSH)
–Luteinizing hormone (LH)
Growth Hormone (GH)
•Produced by somatotropiccells of the anterior lobe that:
–Stimulate most cells, but target bone and skeletal muscle
–Promote protein synthesis and encourage the use of fats for fuel
–Inhibits glucose uptake
•Most effects are mediated indirectly by somatomedins–produced in liver
from HGH
•Antagonistic hypothalamic hormones regulate GH
–Growth hormone–releasing hormone (GHRH) stimulates GH release
–Growth hormone–inhibiting hormone (GHIH) (somatostatin) inhibits GH
Thyroid Stimulating Hormone (Thyrotropin)
•Tropic hormone that stimulates the normal development and secretor
activity of the thyroid gland
•Triggered by hypothalamic peptide thyrotrophic-releasing hormone (TRH)
•Rising blood levels of thyroid hormones act on the pituitary and
hypothalamus to block the release of TSH
Gonadotropins
•Gonadotropins–follicle-stimulating hormone (FSH) and luteinizing hormone
(LH)
–Regulate the function of the ovaries and testes
–FSH stimulates gamete (egg or sperm) production
–LH stimulates androgen secretion