7. THE NERVOUS SYSTEM
A biological highway of information
Can receive, send, and interpret information by
electrical signals
A complex network of nerve cells that regulates our
bodily functions and permits us to reach to the
external world
It contains nerve cells or NEURONS
8. THE NERVOUS SYSTEM
Neuron
It is the base of the nervous system
Its basic purpose is to receive information and
send a signal to other neurons, muscles, or
glands.
It is a nerve cell
It has a cell body, a very long axon sheathed in
myelin, and dendrites.
10. THE NERVOUS SYSTEM
Cell Body
Also known as the Soma
Is the bulbous end of the neuron
It contains the cell nucleus
It makes use of nutrients to supply energy for
neuronal activity.
11. THE NERVOUS SYSTEM
Axons
These are long cytoplasmic tubes that carries
electric impulses from one part of the body to
another.
They are insulated from each other by their myelin
sheaths.
May have branches called terminal buttons at its
end.
Myelin Sheath – the fatty insulating layer that surrounds many axons.
12. THE NERVOUS SYSTEM
Dendrites
These are tiny branches at the ends of all neurons
Are organelles that sense the neurotransmitter
secreted by the axon of another neuron
Dendrites and axons do not directly touch each
other; there is a gap, called a synapse.
13. THE NERVOUS SYSTEM
3 Types of Neurons
Sensory Neurons (Afferent)– posses a long
dendrite and short axon. They carry sensory
receptors to the CNS.
Motor Neurons (Efferent) – have long axon and
short dendrites. They transmit messages to from
the CNS to the muscles or the glands.
Interneurons (Connector) – located only in the
CNS where there is a neuron-to-neuron
connection.
14. THE NERVOUS SYSTEM
Neurotransmitters
Chemicals, called neurotransmitters are released
from one neuron at the presynaptic nerve terminal
then they cross the synapse where they may be
accepted by the next neuron at a specialized site
called a receptor
15. THE NERVOUS SYSTEM
Examples of Neurotransmitters
Acetylcholine – fecilitates learning and memory
Norepinephrine or Noradrenaline – too little may
lead to depression; too much causes hyperactivity
Dopamine – too much may lead to Schizophrenic
Reaction; too little causes Parkinson’s Disease
Epinephrine or Adrenaline – also called the fight-
or-flight hormone
Endorphins – natural pain-killers or “feel-good”
drugs
17. CENTRAL NERVOUS SYSTEM
Consists of the brain and the spinal cord
It causes sensory information to the brain by
the afferent and efferent nerves
It plays a key role in various reflexes
It integrates the information that it receives
from, and coordinates the activity of, all parts of
the bodies
Afferent – conveys impulse toward the CNS
Efferent – conveys impulse to effectors
18. CENTRAL NERVOUS SYSTEM
Spinal Cord
It is a bundle of nerve fibers, no thicker than the
human thumb, that links the brain with the rest of
the body
It is protected by the vertebral column
Located at the dorsal side of the body and links
the brain to the rest of the body.
20. CENTRAL NERVOUS SYSTEM
Brain
A mass of nerve tissue located in the head that
controls the body’s function
It is protected by the skull
It weigh 3lbs and contains 90% of the body
neurons
It has two hemispheres: the left and right
It has three major parts which consists of the
forebrain, midbrain, and the hindbrain
21. CENTRAL NERVOUS SYSTEM
3 Major Parts of the Brain:
1. Forebrain
Occupies the largest part and the entire upper
portion of the skull
It is composed of two major hemispheres:the left
and right
Important Parts are the:
• Thalamus
• Hypothalamus
• Cerebrum
22. CENTRAL NERVOUS SYSTEM
o Thalamus
It may be thought of as a kind of switchboard of
information
Regulates the state of sleep and wakefulness
A by-station from the sensory organs to the
cerebral cortex sensory regions
Has a somatosensory mapping of the body and
has known integrative functions
23. CENTRAL NERVOUS SYSTEM
Hypothalamus
It collects and integrates a huge variety of
information from the body and to
organize neural and endocrine responses that
maintain homeostasis
It controls the autonomic
functions, emotions, endocrine
functions, homeostasis, motor functions, regulates
food and water intake, regulates sleep-wake
cycle, and sex drive and hormones
24. CENTRAL NERVOUS SYSTEM
Cerebrum
It is the main area of the forebrain
It is the part of the brain that controls thought,
memory and the senses
It is divided into two parts - the right hemisphere,
which controls the left side of the body; and the
left hemisphere, which controls the right side of
the body.
26. CENTRAL NERVOUS SYSTEM
3 Major Parts of the Brain:
2. Midbrain
Tracts between the cerebrum and the spinal
cord and functions as part of the overall impulse
conduction system.
It also controls some auditory and visual
responses
27. CENTRAL NERVOUS SYSTEM
3 Major Parts of the Brain:
3. Hindbrain
It is close to the spinal cord
Includes the Medulla Oblongata, Pons, and
Cerebellum
• Medulla Oblongata - has an important role in
heartbeat, breathing, and blood circulation
• Pons - lies in the brainstem just above the
medullaoblongata
• Cerebellum - maintains posture, coordinates
muscular activities; called organ of motor
coordination
28. CENTRAL NERVOUS SYSTEM
The brain also consists of 4 lobes namely the:
1. Frontal Lobe - is located at the front of the brain
and is associated with reasoning, motor
skills, higher level cognition, and expressive
language
2. Parietal Lobe - is located in the middle section of
the brain and is associated with processing tactile
sensory information such as pressure, touch, and
pain
29. CENTRAL NERVOUS SYSTEM
The brain also consists of 4 lobes namely the
3. Temporal Lobe - is located on the bottom
section of the brain. This lobe is also the location
of the primary auditory cortex, which is important
for interpreting sounds and the language we hear
4. Occipital Lobe - is located at the back portion of
the brain and is associated with interpreting visual
stimuli and information
32. PERIPHERAL NERVOUS SYSTEM
It connects the CNS to sensory organs, other
organs of the body, muscles, blood vessels, and
glands
This is divided into 2 major divisions namely the
Somatic Nervous System and the Autonomic
Nervous System
33. PERIPHERAL NERVOUS SYSTEM
1. Somatic Nervous System
Made up of sensory system and motor nerves that
activate skeletal muscles responsible for
movement
Has 43 pairs of major nerves: 12 pairs of Cranial
Nerves and 31 pairs of Spinal Nerves
34. PERIPHERAL NERVOUS SYSTEM
2. Autonimic Nervous System
Functions in an involuntary, reflexive manner
Acts as a control system functioning largely below
the level of consciousness, and
controls visceral functions
Has 2 subsystems namely the Sympathetic
Nervous System and the Parasympathetic
Nervous System
Visceral – of relating to, or located on or among the viscera
35. PERIPHERAL NERVOUS SYSTEM
1. Sympathetic Nervous System
involved in the “fight or flight” response during
emergency situation or in high emotion
It increases alertness, stimulates tissue, and
prepares the body for quick responses to unusual
situations.
causes activation & energy expenditure
36. PERIPHERAL NERVOUS SYSTEM
2. Parasympathetic Nervous System
involved in “rest or repose” system as it quiets the
body and returns it to a lower intensity of arousal
calms the body after the emergency situation is
resolved
involved in relaxation
conserves energy and controls sedentary
40. ENDOCRINE SYSTEM
is made up of glands that produce and secrete
hormones
hormones regulate the body’s
growth, metabolism, and sexual development and
function
Hormones are directly released on the bloodstream
because they have no ducts or structured
passageways to the organs that they serve
42. ENDOCRINE SYSTEM
Classification of Hormones
1. Steroids – lipids derived from cholesterol and it
is secreted by the gonads, adrenal cortex, and
placenta
2. Peptides – short chains of amino acids and it is
secreted by the pituitary, parathyroid, heart,
stomach, liver, and kidneys
3. Amines – derived from amino acid tyrosine and
it is secreted by the adrenal medulla
43. ENDOCRINE SYSTEM
Pituitary Gland is the master gland and influences
growth, metabolism and regeneration
It is divided into 2 parts: the anterior and posterior
Growth Hormones (GH) is a peptide anterior
pituitary hormone essential for growth. Too little GH
may cause dwarfism and too much may cause
gigantism.
Gonadotropins affect the gonads by stimulating
gamete formation and production of sex hormones
44. ENDOCRINE SYSTEM
Prolactin is secreted near the end of pregnancy and
prepares the breasts for milk production
Antidiuretic Hormones (ADH) and oxytocin are
produced in the hypothalamus and transported by
axons to the posterior pituitary where they are
dumped into the blood
ADH controls water balance in the body and blood
pressure
Oxytocin is a small peptide hormone that stimulates
uterine contractions during childbirth
45. ENDOCRINE SYSTEM
Adrenal Glands enables us to cope with stress
It is divided into an inner medulla and an
outer cortex
The medulla synthesizes amine hormones while the
cortex secretes steroid hormones
The adrenal medulla consists of modified neurons
that secrete two
hormones: epinephrine and norepinephrine
The adrenal cortex produces several steroid
hormones in three
classes: mineralcorticoids, glucorticoids, and sex
hormones
46. ENDOCRINE SYSTEM
Thyroid Gland located in the neck and the follicles
in the thyroid secrete thyroglobulin, a storage form
of thyroid hormone
Low production of thyroid hormones is called
hypothyroidism
High production of thyroid hormones is called
hyperthyroidism
47. ENDOCRINE SYSTEM
Pancreas contains exocrine cells that secrete
digestive enzymes into the small intestine and
clusters of endocrine cells (pancreatic islets)and it
secretes the hormones insulin and glucagon, which
regulate blood glucose levels
Too high glucose level may result to hyperglycemia
Too low glucose level may result to hypoglycemia