HORMONES AND COORDINATING SYSTEMS

OF ANIMALS

• Major regulatory system of the body.

• Both Nervous System and Endocrine System
regulate and coordinate the activities of
essentially all other body structures.
• The endocrine system is more like a satellite
radio or television signals broadcast widely so
that every television set, with its receiver
adjusted properly, can receive the signals.
• Endocrine System sends information to the
cells, it controls in the form of chemical signals,
called Hormones, which are released from the • Some hormones bring about prompt responses,
Endocrine Glands. whereas others act on a long term bases,
• Hormones are organic substances produced coordinating growth of organs and metabolic
from one part of the body under certain concentrates in blood and other tissues.
circumstance and are carried to a part or parts • Hormones are transformed or destroyed so
of the body where they take their effects. their effects are not permanent unless a
continuing supply is available.
ANIMAL HORMONES AND THEIR FUNCTIONS • On the basis of their control and influence over
physiological processes, hormones may be
• In insects and other arthropods, growth and divided into four categories:
metamorphosis are controlled by pheromones 1) Hormones concerned with metabolism
synthesized by endocrine glands similar to 2) Hormones of digestion
those of more complex animals. 3) Hormones that regulate growth and development,
• Pheromones are chemicals that are released and
to the surrounding environment by animals. 4) Hormones that control reproduction.
These chemicals, once released, may alter the
physiological behavior of the receiver. For
example, pheromones in insects signal
attraction to copulation.

• Neurosecretory cells in the brain of insects

secrete prothoracicotropic hormone that
activates prothoracic glands to secrete a
hormone called ecdysone.
• This hormone induces ecdysis or molting.
 • The pituitary gland is also called the
hypophysis.
- It is a small gland about the size of a pea.
- it rests in a depression of the sphenoid bone
inferior to the hypothalamus of the brain.
• The hypothalamus is an important autonomic
nervous system and endocrine control
center of the brain located inferior to the
thalamus.

• The secretion of hormone is controlled by

negative-feedback mechanisms.
• Negative –feedback mechanisms keep the
body functioning within a narrow range of
values consistent with life.

• The hypothalamus elaborates three important

tropic hormones – gonadotropic release factor,
corticotropic release factor, and thyrotropic
release factor – which are carried by the
hypophyseal portal system or by the general
circulation to the adenohypophysis, causing it
to release its various tropic hormones.

• The endocrine system is composed of

endocrine organs which are glandular organs
whose cells or groups of cells are specialized in
structure and function to produce substances
needed in bodily processes.
• Endocrine organs or endocrine glands are
ductless glands and their products are
discharged and carried in the blood to the
target site(s) in the body.
• Their effect(s) may either excitatory or
inhibitory in its ac4on.
 • The thyroid gland consists of two lobes and
joined by an isthmus.
• Too little growth hormone secretion can be the • It lies on either side of the trachea below the
result of abnormal development of the pituitary larynx.
gland. • It consists of many follicles lined with cuboidal
• A young person suffering from a deficiency of cells and surrounded by blood vessels and
growth hormone remains a small though nerves.
normally proportioned, person called a pituitary • The follicles are filled with a colloid containing
dwarf. the hormones thyroxine and triiodothyronine,
which regulate the general metabolism of the
body as well as its growth and sexual
development.

• Hypofunction of the thyroid gland decreases

the rate of metabolism.
• A swelling of the face and body as a result of
mucoprotein development and abnormal
maturation of tissues, and impaired
neurological functions.
• The consequence is a mentally retarded
person of short stature and distinctive form
called cretin.
• Around the world, the most common cause of
congenital cretinism is dietary iodine
deficiency. Iodine is an essential trace element
necessary for the synthesis of thyroid
• Excess growth hormone secretion can result hormones.
from hormone-secreting tumors of the pituitary
gland. If excess growth hormone is present
before bones complete their growth in length,
exaggerated bone growth occurs. The result is
gigantism, and the person becomes
abnormally tall.
 The Pancreas

• Within the pancreas there are many small

• Parathyroids are glands that develop as groups of cells, the islets of Langerhans, of
outgrowth of visceral pouches. different form and staining reac:on, not
• They are often four in number in mammals. connected to the duct.
• In humans, they are small oval structures lying • The cells are of three kinds: alpha cells that
behind or partly embedded in the thyroid. produce glucagon, beta cells that produce
• Their secretion, is a polypeptide, insulin, and alpha 1 cells that evidently
parathormone, which regulates the secrete gastrin.
concentrations of calcium and phosphate in • Insulin favors glycogen forma:on and
the blood plasma and affects the metabolism storage in the muscles, liver and other
of these materials in the body. :ssues.
• Glucagon promotes the release of liver
glucose.

• Type 1 diabetes mellitus is caused by the

secretion of too little insulin from the pancreas,
causing blood glucose levels to become very
high, a condition called hyperglycemia.
• Because glucose cannot enter cells of the
satiety center of the brain without insulin, the
satiety center responds as if there were very
little blood glucose, resulting in an exaggerated
appetite.
• Type 2 diabetes mellitus is the most common
type of diabetes which occurs when your blood
sugar is too high.
• This is due to insufficient numbers of insulin
receptors on target cells, or defective
• The adrenal cortex is absolutely essential to
receptors that do not respond normally to
life; when it is completely removed, most
insulin, therefore instead of getting into the cell
animals will live only a week or two.
for use, glucose stays in the blood.
• All the adrenocortical hormones are steroid
compounds and all are structurally similar.
• They can be divided into three groups:
• glucocorticoids, such as cortisone and
hydrocortisone, which regulate food
metabolism (glucose, proteins, fats)
• Mineralocorticoids, such as aldosterone and
desoxycorticosterone, which control the
reabsorption of sodium by kidney tubules as
well as the regulation of other salts.
• Sex hormones which have androgenic and
estrogenic effects to a minor extent.

• The adrenal or suprarenal glands are found at

the superior portions of the kidneys. • Aldosterone is the major hormone of adrenal
• Each is made up of a cortex and a medulla. cortex.
• Each portion of the gland has its own internal • It binds to receptor molecules primarily in the
secretions, and each has developed differently. kidney, but it also affects the intestine, sweat
glands, and salivary glands.
• Aldosterone causes Na+2 and H2O to be
retained in the body and increases the rate at
which K+ are eliminated.
 • Several hormones are produced in cells lining
the stomach and the small intestine that
control secretion of digestive enzymes.
• The following hormones are: secretin,
enterogastrone, enterokinin, cholecystokinin,
• The cells of the adrenal medulla form the and pancreozymin.
central core of the adrenal gland.
• Sympathetic fibers secrete at their terminals,
the hormones epinephrine (adrenalin) and
norepinephrine.
• Epinephrine is one of the few hormones whose
rate of secretion is affected by nervous
stimulation.
• The general action of this hormone centers
around emergency functions of the body, such
as those of fear, flight, rage, and work.
• During emotional states epinephrine is
secreted in great amounts.
• Specifically, the hormone causes a rise in
blood pressure, increase in heart rate, increase
in blood sugar, inhibition of the gastrointestinal
tract, decrease in liver glycogen, and hastening
of blood coagulation.
• Norepinephrine of the adrenal medulla has a
similar effect but has a wider vasoconstrictor
influence. It constricts blood vessels, which
helps maintain blood pressure in times of
stress.
 • This is a large mass of lymphoid tissue located
in the upper part of the chest and covering the
great vessels at the base of the heart.
• It secretes thymosin which enhances body’s
defense of the individual.

• The primary hormones involved in the

functioning of the male reproductive system • The roof of the diencephalon bears the pineal
are follicle-stimulating hormone (FSH), body (epiphysis).
Lutienizing Hormone (LH), and testosterone. • It secretes melatonin, which inhibits gonadal
• FSH and LH are produced in the development and is involved in the regulation
adenohypophysis. Fsh is necessary in of circadian rhythms (daily physiological and
spermatogenesis while lh is for the production behavioral changes).
of testosterone.
 Human Nervous System

• Higher organisms have a nervous system to

perceive stimuli, to transmit these to various
parts of the body, and to effect responses to
maintain homeostasis.
• This system serves also to coordinate and
integrate the functions of cells, tissues, and
organ systems so that they act harmoniously
as a unit.
• Is consists of: the central nervous system, with
large anterior brain connected to a spinal cord,
and the peripheral nervous system of 12 pairs
of cranial nerves from the brain, 31 pairs of
spinal nerves from the cord exiting through the
intervertebral foramina.
• PNS is further subdivided into sensory and
motor divisions.
• The motor division can be further divided into
somatic motor nervous system and the
autonomic nervous system, which can be
divided into sympathetic and parasympathetic
systems.

• The sensory function of the nervous system

derives from sensory receptors at the ends of
peripheral neurons. Sensory receptors convert
environmental information into nerve impulses.
(see next slide for perception process)
• The motor functions of the nervous system
employ peripheral neurons, which carry
impulses from the CNS to responsive
structures called effectors.
• Mental activity. The brain is the center of
mental activity, including consciousness,
memory and thinking.

• The nervous system is composed of nerve

cells, or neurons, with cell processes known as
dendrites and axons.
• The neuron is the structural and functional unit
of the nervous system which constitute about
10% of the cells in the human nervous system.
• The remainder are glial cells (neuroglia) which
are not electrically excitable but which support
the neurons physically and are believed to
participate actively in brain function.
 • Schwann cells are also referred to as
neurolemmocytes or neurolemma cells.

• Each nerve cell is consists of a cell body and

two types of processes: dendrites and axons.
• Where the axon leaves the cell body is an area • Astrocytes, commonly found between neurons
called the axon hillock, which is devoid of Nissl and blood vessels, provide structural support,
bodies. join parts by their abundant cellular processes,
• An axon may remain unbranched or may and help regulate the concentrations of
branch to form collateral axon (fig.8.3). nutrients and ions within the tissue.
• Axons are surrounded by neuroglia called • Astrocytes also form scar tissue that fills
Schwann cells, which form a highly specialized spaces following injury to the CNS.
insulating layer of cells called the myelin
sheath.

• Ependymal cells form an epithelia-like

membrane that covers specialized brain parts
• Microglial Cells are scattered throughout the (choroid plexuses) and forms the inner linings
CNS. that enclose spaces within the brain
• They support neurons and phagocytize (ventricles) and spinal cord (central canal).
bacterial cells and cellular debris.
• Oligodendrocytes align along nerve fibers.
• They provide insulating layers of myelin, called
myelin sheath around axons within brain and
spinal cord.
• Schwann cells are glial cells surrounding the
axons of neurons in the PNS.
 postsynaptic membrane closer to threshold
and trigger nerve impulses), but those from
other knobs have an inhibitory action (make it
less likely that threshold will be reached).
• Neuromodulators are a bit different, as they are
not restricted to the synaptic cleft between two
neurons, and so can affect large numbers of
neurons at once.
• The effect on the postsynaptic neuron
depends on which presynaptic knobs are
activated from moment to moment

• Between any two related neurons in function

there is a close association, or synapse which
passes nerve impulse in only one direction,
from the axon of one neuron to the dendrite of
the other.
• Here, electrical signals that have travelled
along the axon are briefly converted into
chemical ones through the release of
neurotransmitters, causing a specific response
in the receiving neuron.

• Synaptic transmission is a one-way process

carried out by biochemicals called
neurotransmitters across the synaptic cleft.
• The neuron carrying the impulse into the
synapse is the presynaptic neuron, and the one
that receives this input at the synapse is the • Groups of neuron cell bodies and their
postsynaptic neuron. dendrites, where there is very little myelin, form
• The distal ends of axons have one or more gray matter.
extensions called synaptic knobs, absent in • Gray matter on the surface of the brain is
dendrites, which contain many membranous called, cortex, and clusters of gray matter
sacs, called synaptic vesicles. located deeper within the brain are called,
• When a nerve impulse reaches a synaptic nuclei.
knob, some of the vesicles release • In the PNS, a cluster of neuron cell bodies is
neurotransmitter. called a ganglion. Ganglia can be thought of as
• The neurotransmitter diffuse across the synaptic relay stations between neurons.
synaptic cleft and reacts with specific • Bundles of parallel axons with myelin sheaths
receptors on the post-synaptic neuron are whitish in color and are called white matter.
membrane.

• Neurotransmitters released by some of these

knobs have an excitatory action (bring the
 • A reflex arc begins with a receptor at the end of
a sensory (or afferent) neuron. This neuron
usually leads to several interneurons within
CNS, which serve as a processing center, or
reflex center.
• These interneurons can connect with
interneurons in other parts of the nervous
system.
• They also communicate with motor neurons,
whose axons pass outward from the CNS to
effectors.

• Nerves are bundles of axons. An axon is often

referred to as a nerve fiber. Nerve fibers are
classified as:
- sensory fibers or afferent fibers
- motor fibers or efferent fibers
• A nerve is a cordlike bundle of nerve fibers
within layers of connective tissue. These are
classified into:
- sensory nerves
- motor nerves
• Most nerves include both sensory and motor
fibers and are called mixed nerves.

• Bones, membranes, and fluid surround the

organs of the CNS.
• Layered membranes called meninges lie
between the bony covering and the soft tissues
of the CNS, protecting the brain and the spinal
cord.
• The meninges have three layers – dura mater,
arachnoid mater, and pia mater.

• The routes nerve impulses follow as they travel

the nervous system are called nerve pathways.
• The simplest of these pathways includes only a
few neurons and is called a reflex arc.
• It constitutes the structural and functional
basis for involuntary actions called reflexes.
• Cerebrospinal fluid (CSF) fills the ventricles, • The tracts consist of axons ascending to the
the subarachnoid space around the brain and brain or descending from the brain.
spinal cord, and the central canal of the spinal • Spinal nerves arise from numerous rootlets
cord. along the dorsal and ventral surfaces of the
• Approximately 23 ml of CSF fills the ventricles, spinal cord.
and 117ml fills the subarachnoid space. • The rootlets combine to form a ventral root and
• CSF provides a protective fluid cushion around a dorsal root at each segment of the cord.
the brain and spinal cord, protecting them from • The ventral and dorsal roots extend laterally
movements of the skull and vertebral column. from the cord, passing through the
It also provides some nutrients to CNS tissues. subarachnoid space, piercing the arachnoid
mater and dura mater, and joining one another
to form a spinal nerve.

• The spinal cord varies in size with different

vertebrates. In the average man, it is about 18
inches long, extending only to the level of the
first lumbar vertebra. • The spinal cord has two major functions –
• It is protected by the vertebral column and the conducting nerve impulses to and from the
three layers of meninges – the dura mater, brain, and serving as a center for spinal
arachnoid, and pia mater. reflexes.
• Spaces between these protective layers • The nerve tracts of the spinal cord consist of
contain cerebrospinal fluid which forms a axons that provide a two-way communication
protective cushion. system between the brain and the body parts
outside the nervous system: the ascending
tracts and the descending tracts.
• The ascending tracts carry sensory information
• The spinal cord is divided into right and left from the body, like pain, for example, up the
halves. spinal cord to the brain.
• Peripherally located is the white matter, • The descending tracts carry motor
surrounding the gray matter which is shaped informations, like instructions to move the arm,
like a butterfly. from the brain down the spinal cord to the
• The white matter in each half of the spinal cord body.
is organized into three columns, or funiculi,
called the ventral, dorsal, and lateral columns.
• Each column is subdivided into tracts, also
called fasciculi or pathways.
• There are five divisions of the brain in adult
vertebrates:
• (1) Telencephalon or cerebrum, the anterior
and largest division. It is the seat of
consciousness, intelligence, sensory
perception of sight, olfactory, and auditory
senses, and coordination of body movements,
• (2) Diencephalon or twixt brain, the part
posterior to the cerebrum and connects the
cerebrum with the other motor center for
visual sensation,
• (3) Mesencephalon or optic lobe, the center for
visual sensation,
• (4) Metencephalon or cerebellum, the seat of
unconscious motor coordination and
maintenance of muscular equilibrium, and
• The largest part of the human brain is the
• (5) Myelencephalon or medulla oblongata, the
cerebrum.
center of various secretory functions and
• It is consists of two large masses called the left
movement of the digestive tract, heart, blood
vessels, and lungs. and right cerebral hemispheres, which are
essentially mirror images of each other.
• A deep bridge of nerve fibers called corpus
callosum connects the cerebral hemispheres.
• A layer of dura mater (falx cerebri) separates
them.
• It contains about half the nerve cells in the
brain.
• The surface is called cerebral cortex and is
thrown into folds, called convolutions (gyri)
that greatly increase its area.
• A shallow groove on the cortex is called a
sulcus, and a deep groove is called fissure.
• A longitudinal fissure separates the right and
left cerebral hemispheres, a transverse fissure
separates the cerebrum from the cerebellum.
• The cell bodies of neurons predominate in the
cortex which receive information, process it,
store some in memory for future use, and
direct voluntary motor output.

• The several sulci divide each hemisphere into

lobes:
- Frontal lobe – for voluntary motor
functions, motivation, aggression,
mood and olfactory.
 - Parietal lobe – for touch, pain,
temperature balance, and taste.
- Temporal lobe – for olfactory, auditory,
and memory.
- Occipital lobe – for visual input.

• Damage to the cortex due to trauma, stroke, or

a tumor results in specific deficits, such as
problems with speech, difficulty in reading, or
inability to sense or move specific parts of the
body.
• Since brain cells cannot reproduce, once a • The hindbrain is represented by the medulla
brain region is destroyed, it cannot be repaired oblongata, the pons, and the cerebellum. This
or replaced, so these deficits are often constitute the “brainstem”.
permanent. • The medulla oblongata is the most posterior
division of the brain, and is a conical
continuation of the spinal cord. This is the
• The diencephalon has a slender dorsal pineal respiratory center of the body.
body, or epiphysis. • Between the medulla and the midbrain is a
• Below the diencephalon is the optic chiasma thick bundle of fibers, the pons (“bridge”) that
followed by the infundibulum, with the carry impulses from one side of the cerebellum
hypophysis, or pituitary gland, at its posterior to the other.
end.

• The cerebellum lies above the medulla and is

concerned with equilibrium, posture, and
movement.
• Its development is directly correlated with the
individual’s mode of locomotion, agility of limb
movement, and balance.
 • The hypothalamus contains many different
clusters of neurons.
• Some of these are neurosecretory cells that
release hormones.
• Through this hormone production and neural
connections, the hypothalamus acts as a major
coordinating center, controlling body
temperature, hunger, the menstrual cycle,
water balance, and the autonomic nervous
system.
• In addition, stimulation of specific areas of the
hypothalamus elicits emotions such as rage,
fear, pleasure, and sexual arousal.

n The limbic system is a diverse group of

structures located in an arc between the
thalamus and the cerebrum.
n These structures work together to produce our
most basic and primitive emotions, drives, and
behaviors, including fear, rage, tranquility,
hunger, thirst, pleasure, and sexual responses.

• Speech
0 o speech area is in the left cerebral
cortex.
o two major cortical areas are involved:
the Wernicke’s area which is the
sensory speech area and the Broca’s
area which is the motor speech area.
o damage to these areas may result in
aphasia, absent or defective speech or
language comprehension.
• Memory
• Hippocampus curves around the thalamus. o memory is consists of four processes:
• Stimulation of portions of the hippocampus encoding, consolidation, storage, and
can elicit behaviors that reflect a variety of retrieval.
emotions, including rage and sexual arousal. o Short-term memory or working
• It also plays an important role in the formation memory is where information is
of long-term memory, and thus is required for retained for a few seconds to a few
learning. minutes.
 o Long-term memory occurs when some VII. Facial nerve
pieces of information are transferred • The facial nerve provides both sensory and
for storage from short-term memory. motor functions, including:
The length of time that memory is moving muscles used for facial expressions as
stored may depend on how often it is well as some muscles in your jaw
retrieved and used. • providing a sense of taste for most of your
tongue
• supplying glands in your head or neck area,
such as salivary glands and tear-producing
I. Olfactory nerve glands
• The olfactory nerve transmits sensory • communicating sensations from the outer
information to your brain regarding smells that parts of your ear.
you encounter. VIII. Vestibulocochlear nerve
II. Optic nerve • Your vestibulocochlear nerve has sensory
• The optic nerve is the sensory nerve that functions involving hearing and balance. It
involves vision. consists of two parts, the cochlear portion and
III. Oculomotor nerve vestibular portion:
• The oculomotor nerve has two different motor Cochlear portion - Specialized cells within your
functions: muscle function and pupil response. ear detect vibrations from sound based off of
• IV. Trochlear nerve the sound’s loudness and pitch. This generates
• The trochlear nerve controls your superior nerve impulses that are transmitted to the cochlear
oblique muscle. This is the muscle that’s nerve.
responsible for downward and inward eye • Vestibular portion. Another set of special cells
movements. in this portion can track both linear and
V. Trigeminal nerve rotational movements of your head. This
• The trigeminal nerve is the largest of your information is transmitted to the vestibular
cranial nerves and has both sensory and motor nerve and used to adjust your balance and
functions. The trigeminal nerve has three equilibrium.
divisions, which are: IX. Glossopharyngeal nerve
• Ophthalmic. The ophthalmic division sends • The glossopharyngeal nerve has both motor
sensory information from the upper part of and sensory functions, including: sending
your face, including your forehead, scalp, and sensory information from your sinuses, the
upper eyelids. back of your throat, parts of your inner ear, and
• Maxillary. This division communicates sensory the back part of your tongue
information from the middle part of your face, • Providing a sense of taste for the back part of
including your cheeks, upper lip, and nasal your tongue
cavity. • stimulating for voluntary movement of a
• Mandibular. The mandibular division has both muscle in the back of your throat called the
a sensory and a motor function. It sends stylopharyngeus.
sensory information from your ears, lower lip, X. Vagus nerve
and chin. It also controls the movement of • The vagus nerve is a very diverse nerve. It has
muscles within your jaw and ear. both sensory and motor functions, including:
VI. Abducens nerve communicating sensation information from
• The abducens nerve controls another muscle your ear canal and parts of your throat
that’s associated with eye movement, called • Sending sensory information from organs in
the lateral rectus muscle. This muscle is your chest and trunk, such as your heart and
involved in outward eye movement. For intestines
example, you would use it to look to the side. • Allowing motor control of muscles in your
throat
 • Stimulating the muscles of organs in your • Autonomic nerves control the movements of
chest and trunk, including those that move most organs in the body. Although these
food through your digestive tract (peristalsis) nerves have both sensory and motor
• Providing a sense of taste near the root of your components, the former are considered of
tongue minor importance.
XI. Accessory nerve • Their actions are antagonistic.
• Your accessory nerve is a motor nerve that
controls the muscles in your neck. These
muscles allow you to rotate, flex, and extend
your neck and shoulders.
XII. Hypoglossal nerve
• Your hypoglossal nerve is the 12th cranial
nerve which is responsible for the movement
of most of the muscles in your tongue. It starts
in the medulla oblongata and moves down into
the jaw, where it reaches the tongue.

• There are 31 pairs of spinal nerves that moved

out from the spinal cord through the
intervertebral foramina at the sides of the
vertebral column.
• There are 8 pairs of cervical spinal nerves, 12
pairs of thoracic spinal nerves, 5 pairs of
lumbar spinal nerves, 5 pairs of sacral spinal
nerves and a pair of coccygeal spinal nerves.

• Parasympathetic division – centered partly in

the brain and partly in the lower end of the
spinal cord.
• It is for this reason that it is regarded as
craniosacral division of the autonomic nervous
system.
• The autonomic nerves govern the involuntary
functions of the body which do not ordinarily • Once stimulated, it is for the rest and repose
affect consciousness. response of the body.
• The sympathetic division is centered in the
middle part of the spinal cord. Thus it is also
known as the thoracolumbar division.
• Sympathetic fibers excite the heart, blood
vessels, sphincters of the intestines, urinary
bladder, dilator muscles of the iris and others.
• It is for the fight or flight response of the
individual.