The document discusses the nervous system. It begins by outlining the four primary functions of the nervous system: sensing the world, transmitting information, processing information, and producing a response. It then describes neurons and their parts including dendrites, cell body, axon, and axon terminals. It explains the three main types of neurons and provides an overview of the central and peripheral nervous systems. Key areas of the brain and their functions are identified. Finally, it discusses the autonomic nervous system and roles of the sympathetic and parasympathetic nervous systems.

1. 1
University of Hail
College of Nursing
Physiology PHYL281
Dr Jupiter V. Cajigal
Assistant Professor, University of Hail
UNIT 2
The Nervous System

2. Objectives :
At the end of this lecture, the student will be able
to:
 Describe the functions of the nervous system
 Describe the parts of a neuron cell and identify how
they transmit electrochemical impulses.
 Compare and contrast the central and peripheral
nervous systems
 Identify and explain different areas of the brain and
their functions.
 Explain how the nervous system passes information
between the external environment and the many
parts of the body.

3. FOUR PRIMARY FUNCTIONS OF
NERVOUS SYSTEM
• Sensing the world
• Vision, Hearing, Smell,
Taste, Touch
• Transmitting
information
• Processing information
• Producing a response

6. NEURONS
• a specialized cell
transmitting nerve
impulses; a nerve
cell.

7. NEURONS
Glial cells surround neurons
and provide support for and
insulation between them.
Glial cells are the most
abundant cell types in the
central nervous system.
Types of glial cells include
oligodendrocytes,
astrocytes, ependymal cells,
Schwann cells, microglia,
and satellite cells.

8. Parts of nerve cell & Function of each part:
• Dendrites : receive
chemical signals from
neighboring cells.
• Dendrites are the
structures on the
neuron that receive
electrical messages.
These messages come
in two basic forms:
excitatory and
inhibitory.

9. Parts of nerve cell & Function of each part:
• Cell Body: contains the
nucleus & organelles
• It also contains the cell's
DNA, which is essentially
the neuron's blueprint.
The nucleus is another
organelle that serves a
vital purpose to the
functioning of the
neuron. It nucleolus
produces ribosomes,
which are essential to
protein production.

10. Parts of nerve cell & Function of each part:
 Axon: long extension that
carries electrical
messages away from the
body to the terminal
axons.
 An axon, is a long,
slender projection of a
nerve cell, or neuron, that
typically conducts
electrical impulses away
from the neuron's cell
body. Myelinated axons
are known as nerve fibers.
The function of the axon is
to transmit information to
different neurons, muscles
and glands.

11. Parts of nerve cell & Function of each part:
 the somewhat enlarged,
often club-shaped
endings by which axons
make synaptic contacts
with other nerve cells or
with effector cells
(muscle or gland cells).
Axon terminals contain
neurotransmitters of
various kinds,
sometimes more than
one.

12. Parts of nerve cell & Function of each part:
 main purpose of myelin
is to increase the speed
at which electrical
impulses propagate
along the myelinated
fiber. In unmyelinated
fibers, electrical
impulses (action
potentials) travel as
continuous waves, but,
in myelinated fibers,
they "hop" or propagate
by saltatory conduction.

13. Parts of a neuron
Nerve Cell

14. Types of Neurons
 3 main types of neurons:
Sensory neuron = detect stimuli
Interneurons = relay sensory signals to
brain then return message back to motor
neurons.
Motor neuron = pass message from brain to
rest of body for muscle response.
This coordinated pathway is known as the
REFLEX ARC

16. Reflex Arc
“ what happens when you step on a nail”?
Reflexes are automatic
The Stimulus (nail ) is received by
the sensory neurons in the foot
This info travels to the spine, where
the interneuron is triggered
The interneuron transmits signal to
brain (through the spinal cord)and
carries message back and stimulates
the motor neuron, to move the foot

17. Nerve Impulse
A progressive wave of
electric and chemical
activity along a nerve
fiber that stimulates or
inhibits the action of a
muscle, gland, or other
nerve cell

18. Nervous System(Central Nervous System)
• the part of the nervous
system which in
vertebrates consists of
the brain and spinal
cord, to which sensory
impulses are
transmitted and from
which motor impulses
pass out, and which
coordinates the
activity of the entire
nervous system —
compare peripheral
nervous system.

19. NervousSystem(PeripheralNervousSystem)
• The nerves in the
PNS connect the
central nervous
system (CNS) to
sensory organs, such
as the eye and ear,
and to other organs
of the body, muscles,
blood vessels, and
glands.

22. Nervous System
 Has two main divisions
1. Central Nervous System
( CNS) brain, spinal cord
2. Peripheral Nervous System
( PNS) all other nerves

23. The Nervous system is:
• A physically connected network of cells,
tissues and organs that allow us to
communicate with and react to the
environment and perform life activities.

24. 2 main divisions:
Central Nervous System
(CNS)
• Receives, interprets and
sends signals to peripheral
nervous system (PNS).
• Has 2 main parts:
• Brain – main control
center
• Spinal Cord – connects
and relays nerve
impulses to the brain

25. Peripheral Nervous System (PNS)
 Connects CNS to all organ systems
 Made up of:
 Sensory Neurons: detect stimuli
 Motor Neurons: carry signal to stimulate response
 2 major subsystems:
 Somatic – voluntary movement (balance,
movement)
 Autonomic – involuntary movement (digestion,
fight or flight)

29. The Brain

30. Cerebrum

31. • Large front part of the brain
FUNCTIONS:
– Voluntary activity
– Memory
– Language
– Receives and responds to sensory signals
– Controls motor functions

32. Cerebellum

33. THE CORTEX

34. Top layer of the brain
Stores: experiences and/or learning
Frontal-
behavior &
emotion
Temporal- memory & emotion, speech and hearing
Occipital- vision
Parietal-
Sensory info
concerning touch

35. Brain Stem
 BRAIN STEM
 swallowing, coughing,
sneezing, and vomiting
 Includes the
Medulla Oblongata

36. Brain Stem
 PONS
 Breathing
 Heart rate
 Internal Organs

37. “controls: emotions and memories”
Damage to
these areas
can lead to
amnesia or
emotional
disturbances

38. The Autonomic Nervous System
• Divided into:
I-Sympathetic: Originate from:
The lateral horn cells of all thoracic & upper 3 lumbar
Segments of the spinal cord .
II – Parathempathetic Nervous system(cranio-sacral
Outflow):
The cranial outflow: The sacral outflow:
- 2 , 3 & 4 sacral spinal
nerves .
 Oculomotor nerve (3).
 Facial (7)
 Glossopharyngeal (9)
 Vagus (10)

40. Innervation of Body Organs
-In the body there are organs which are
innervated by both sympathetic and
parasympathetic systems:
- Heart
- Digestive tract
- Pupil of the eye
- Salivary glands
There are organs with only sympathetic
innervation:
 Adrenal medulla
 Sweat glands
 Most blood vessels

41. Functions of 1- Sympathetic system:
 Excitation of
sympathetic centers will
cause:
 - Increase in heart
rate.
 - Increase in blood
pressure,
 - Blood glucose is
elevated
 - Increase in the
rate of metabolism

42. Function of Parasympathetic system
 2-parasympathetic
system: usually has
opposite effects to those
of sympathetic
system.
 Excitation of
parasympathetic
causes:
 Decrease in heart rate,
 Increase blood flow to
the digestive system,
 Increase activity of the
digestive system.

44. Nerves Function :
 A nerve is a fiber that
connects the brain and
spinal cord with various
parts of the body.
 Nerves conduct
impulses from the
brain/spinal cord to
these receptor organs
as well as conducting
impulses from the
receptor organs back to
the brain/spinal cord.

45. SYMPATHETIC NERVOUS SYSTEM
• Cause vasoconstriction by activation of a-adrenergic
receptors on vascular smooth muscle by
norepinephrine.
• Vasoconstriction of arterioles increased vascular
resistance and redistribution of blood flow
• Vasoconstriction of veins increased circulating blood
volume, increased venous return leads to increased
ventricular filling and stroke volume.
• Increase in the activity of the heart (heart rate and
contractility)
• There are also sympathetic vasodilator fibers which
release epinephrine acting on β-adrenergic receptors.

46. PARASYMPATHETIC SYSTEM
• 75% of all parasympathetic nerve fibers are in the
vagus nerves (cranial nerve X)
• Pass to the entire thoracic and abdominal regions
of the body , including the heart.
• Preganglionic nerves pass all the way to the organ.
• Postganglionic nerves are very short and located
entirely in the wall of the organ.
• Play a role in the regulation of circulation.
• Mainly control heart rate
• Stimulation of vagus nerves results in a decrease in
heart rate and contractility