Human Anatomy and Physiology

1. THE NERVOUS SYSTEM
 Dr.P.Thirunagalinga Pandiyan
M.Sc., (N) Ph.D.,(N)
College of Nursing
Madurai Medical College, Madurai. India.

2. THE NERVOUS SYSTEM

3. THE NERVOUS SYSTEM
The human nervous system is divided into
two parts :
 The Central Nervous System (CNS)
The Peripheral Nervous System (PNS)

4. NERVOUS SYSTEM
 The CNS includes the brain and the spinal cord
 The PNS comprises of all the nerves of the body
associated with the CNS (brain and spinal cord).
 The nerve fibres of the PNS are of two types :
(a) Afferent fibres - transmit impulses from tissues/organs
to the CNS
(b) Efferent fibres - transmit regulatory impulses from the
CNS to the concerned peripheral tissues/organs.

5. THE NERVOUS SYSTEM
The PNS is divided into two divisions called
 Somatic nervous system – Transmit impulse
from the CNS to skeletal muscles
 Autonomic nervous system - Transmits
impulses from the CNS to the involuntary
organs and smooth muscles of the body.

6. THE NERVOUS SYSTEM
The autonomic nervous system is further classified
into
 Sympathetic nervous system – excitement and
energy loss
 Parasympathetic nervous system – calmness and
energy savers

7. NEURON
 Neurons (also called neurones or nerve cells)
are the fundamental units of the brain and
nervous system, the cells.
 It is responsible for receiving sensory input
from the external world, for sending motor
commands to our muscles, and for
transforming and relaying the electrical signals
at every step in between.

8. NEURON
 A neuron is a microscopic structure composed of
three major parts, namely
1. Cell Body
2. Dendrites
3. Axon
 The cell body contains cytoplasm with typical cell
organelles and certain granular bodies called Nissl’s
granules.
 Center there is nucleus
 Short fibers which branch repeatedly and project out
of the cell body is dendrites

9. NEURON
 Each branch terminates
as a bulb-like structure
called synaptic knob or
axon terminals
 It is covered by sheath
called myelin sheath
 The gaps between two
adjacent myelin sheaths
are called nodes of
Ranvier.
 The myelinated nerve
fibres are enveloped with
Schwann cell

10. CENTRAL NERVOUS SYSTEM
1. The Brain
2. The Spinal cord
 These organs work together to integrate and
coordinate sensory and motor information for the
purpose of controlling the various tissues, organs,
and organ systems of the body.
 The central nervous system is responsible for higher
neural functions, such as memory, learning, and
emotion.

11. CENTRAL NERVOUS SYSTEM
 Brain is situated in the
skull. It is continued as
spinal cord in the vertebral
canal through the foramen
magnum
 Brain and spinal cord are
surrounded by three layers
of meninges called the
outer dura mater, middle
arachnoid mater and
inner pia mater.

12. CENTRAL NERVOUS SYSTEM
 The space between
arachnoid mater and pia
mater is known as
subarachnoid space.
 This space is filled with a
fluid called cerebrospinal
fluid. Brain and spinal cord
are actually suspended in
the cerebrospinal fluid.

13. Parts of Brain
 Brain consists of three
major divisions:
1. Prosencephalon
 2. Mesencephalon
 3. Rhombencephalon

14. BRAIN
Brain
 Weighs about nearly 1.3
kgs in adults
 75% water
 20% of oxygen
 Contains over 100 billion
neurons
 Controls bodily functions
and interactions with the
outside world

15. BRAIN
Four Parts:
 Cerebrum
 Diencephalons
 Brain stem
 Cerebellum

16. CEREBRUM
 Located above the cerebellum.
Contains two hemispheres with an
outer portion called the cerebral cortex.
 The two hemispheres are connected by
a bridge of nerve fibers that relay
information between the two
hemispheres called the corpus
callosum.
 The left and right lobes are each
divided into four lobes or parts
 Frontal lobe
 Parietal lobe
 Temporal lobe
 Occipital lobe

17. CEREBRUM
Frontal lobe.
 The largest lobe of the brain, located in the front of
the head, the frontal lobe is involved in personality
characteristics, decision-making and movement.
 Recognition of smell usually involves parts of the
frontal lobe. The frontal lobe contains Broca’s area,
which is associated with speech

18. CEREBRUM
Parietal lobe.
 The middle part of the brain, the parietal lobe helps
a person identify objects and understand spatial
relationships
 The parietal lobe is also involved in interpreting pain
and touch in the body.
 The parietal lobe houses Wernicke’s area, which
helps the brain understand spoken language.

19. CEREBRUM
 Occipital lobe
 The occipital lobe is the back part of the brain that is
involved with vision.
 Temporal lobe
The sides of the brain, temporal lobes are involved in
short-term memory, speech, musical rhythm and some
degree of smell recognition.

20. CEREBRUM – FUNCTIONS
 The cerebrum (front of brain) comprises gray matter
(the cerebral cortex) and white matter at its center. It
is covered with ridges (gyri) and folds (sulci).
 The largest part of the brain, the cerebrum initiates
and coordinates movement and regulates
temperature.
 Other areas of the cerebrum enable speech,
judgment, thinking and reasoning, problem-solving,
emotions and learning.
 Other functions relate to vision, hearing, touch and
other senses.

21. DIENCEPHALON
The deep portion of the brain
containing:
• Thalamus
 Hypothalamus
 Epithalamus

22. BRAINSTEM
 The brainstem (middle of brain) connects the
cerebrum with the spinal cord. The brainstem
includes
 The Midbrain
 The Pons
 The Medulla

23. BRAINSTEM
 Midbrain : Involved with
visual reflexes
 Pons: • Located between the
midbrain and the medulla
oblongata. It Controls certain
respiratory functions
 Medulla Oblongata:
Contains centers that regulate
heart and lung functioning,
swallowing, coughing, vomiting
and sneezing

24. CEREBELLUM
 Area that coordinates
musculoskeletal movement
to maintain posture,
balance, and muscle tone.
 Inferior to the occipital
lobes of the
cerebrum.Posterior to the
pons and medulla
oblongata .

25. Deeper Structures Within the Brain
 Pituitary Gland
 Sometimes called the “master gland,” the pituitary gland is a
pea-sized structure found deep in the brain behind the bridge
of the nose.
 Thalamus
 The primary function of the thalamus is to relay motor and
sensory signals to the cerebral cortex. It also regulates sleep,
alertness, and wakefulness.
 Hypothalamus
 The hypothalamus is located above the pituitary gland and
sends it chemical messages that control its function. It
regulates body temperature, synchronizes sleep patterns,
controls hunger and thirst

26. Deeper Structures Within the Brain
 Amygdala
 Small, almond-shaped structures, an amygdala is
located under each half (hemisphere) of the brain.
Included in the limbic system, the amygdalae regulate
emotion and memory and are associated with the
brain’s reward system, stress, and the “fight or flight”
response when someone perceives a threat.
 Hippocampus
 A curved seahorse-shaped organ on the underside of
each temporal lobe. It supports memory, learning,
navigation and perception of space

27. Deeper Structures Within the Brain
 Pineal Gland
 The pineal gland is located deep in the brain and
attached by a stalk to the top of the third ventricle.
 The pineal gland responds to light and dark and
secretes melatonin, which regulates circadian
rhythms and the sleep-wake cycle.

28. Blood Supply to the Brain
 Two sets of blood vessels supply blood and oxygen to the
brain: the vertebral arteries and the carotid arteries.
 The external carotid arteries extend up the sides of neck and
The internal carotid arteries branch into the skull and circulate
blood to the front part of the brain.
 The vertebral arteries follow the spinal column into the skull,
where they join together at the brainstem and form the basilar
artery, which supplies blood to the rear portions of the brain.
 The circle of Willis, a loop of blood vessels near the bottom
of the brain that connects major arteries, circulates blood from
the front of the brain to the back and helps the arterial
systems communicate with one another.

29. Circle of willis

30. SPINAL CORD
Situation and Extent
 Spinal cord lies loosely in
the vertebral canal. It
extends from foramen
magnum to the lower
border of first lumbar
vertebra below.

31. SPINAL CORD
Coverings
 Spinal cord is covered by sheaths called meninges,
which are membranous in nature.
 Meninges are dura mater, pia mater and
arachnoid mater.

32. SPINAL CORD
 Shape and Length
 Spinal cord is cylindrical in shape. Length of the
spinal cord is about 45 cm in males and about 43
cm in females

33. SPINAL CORD
 Segments
 1. Cervical segments/Cervical
spinal nerves = 8
 2. Thoracic segments/Thoracic
spinal nerves = 12
 3. Lumbar segments/Lumbar
spinal nerves = 5
 4. Sacral segments/Sacral spinal
nerves = 5
 5. Coccygeal segment/Coccygeal
spinal nerves = 1
 Total = 31

34. SPINAL CORD
 Spinal Nerves
 Segments of spinal cord correspond to 31 pairs of
spinal nerves in a symmetrical manner.

35. PERIPHERAL NERVOUS SYSTEM
 Peripheral Nervous System
Consists of 12 pairs of cranial nerves and 31 pairs of
spinal nerves

36. CRANIAL NERVES – 12 PAIRS

38. SPINAL NERVES
 1. Cervical segments/Cervical spinal nerves = 8
 2. Thoracic segments/Thoracic spinal nerves = 12
 3. Lumbar segments/Lumbar spinal nerves = 5
 4. Sacral segments/Sacral spinal nerves = 5
 5. Coccygeal segment/Coccygeal spinal nerves = 1
 Total = 31