The nervous system has four basic functions: sensation, integration, reaction, and internal regulation. It is organized into two main parts: the central nervous system (CNS) and the peripheral nervous system (PNS). The CNS contains the brain and spinal cord. The PNS contains nerves that connect the CNS to the rest of the body. The brain is divided into sections that control different functions like movement, coordination, senses, and homeostasis. Neurons are the basic functional units that transmit signals via electrical and chemical processes. Reflexes are automatic responses mediated by pathways within the spinal cord that connect receptors to effectors via a reflex arc in the CNS.

1. THE NERVOUS SYSTEM PHYSIOLOGY

2. BASIC FUNCTIONS OF THE NERVOUS SYSTEM
1. Sensation
Monitors changes/events occurring in and outside
the body. Such changes are known as stimuli and the
cells that monitor them are receptors.
2. Integration
The parallel processing and interpretation of sensory
information to determine the appropriate response.
3. Reaction
Motor output - The activation
of muscles or glands (typically via
The release of neurotransmitters.
4.Internal regulation (homeostasis
for optimum performance).

3. ORGANIZATION OF THE HUMAN NERVOUS SYSTEM
Because of the complexity of the Nervous System it is
difficult to study all its parts at the same time; thus it is
usually being studied in terms of its structures (structural
classification) and in terms of its activities (functional
classification).
A. Structural Classification
1. Central Nervous System (CNS) - includes the
brain and the spinal cord
2. Peripheral Nervous System (PNS)
- includes cranial nerves and spinal nerves

4. Organization of the Human
Nervous System

6. Functions of individual parts of brain
1-Cerebrum
2-Cerebellum
3-Diencephalon
4-Brain stem

7. • In humans, the Cerebrum is the largest and most complex
part of the brain.
• The cerebral cortex controls voluntary movement and cognitive
functions
• The cerebrum has right and left cerebral hemispheres.
• Each side of the cerebral cortex has four lobes: frontal,
temporal, occipital, and parietal.
1. Frontal - Motor areas for voluntary body movements
2. Parietal – Somatosensory (interprets sensations)
3. Temporal- Auditory (interprets sounds)
4. Occipital- Visual (Interprets what a person sees)
Cerebrum

8. human cerebral cortex
Speech
Occipital lobe
Vision
Temporal lobe
Frontal lobe
Parietal lobe
Somatosensory
association
area
Frontal
association
area
Visual
association
area
Reading
Taste
Hearing
Auditory
association
area
Speech
Smell

9. The Cerebellum
•The cerebellum is important for coordination of
movements and equilibrium.

10. Diencephalon
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 Sits on top of the brain stem
 Enclosed by the cerebral hemispheres
 Made of two parts
Thalamus
Hypothalamus

11. Thalamus
Slide 7.35
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 The main function is to relay motor and
sensory signals to the cerebral cortex.

12. Hypothalamus
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Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
 Under the thalamus
1. Important autonomic nervous system
center
2. Helps regulate body temperature
3. Controls water balance
4. Regulates metabolism

13. Brain stem

14. Brain stem
• Made up of the midbrain; Pons and the medulla oblongata.
Midbrain : Involved with visual reflexes
Pons:
• Located between the midbrain and the medulla
oblongata
• Controls certain respiratory functions
Medulla Oblongata:
• Contains centers that regulate heart and lung
functioning, swallowing, coughing, vomiting and
sneezing

15. Peripheral nervous system (PNS)
• In human, the peripheral nervous system consists of:
• 12 pairs of cranial nerves
• 31 pairs of spinal nerves
• The PNS transmits signals between CNS and rest of the body.

16. B-Functional Classification OF THE NERVOUS
SYSTEM(PNS)
1. Sensory Division (Afferent division)
Conducts impulses from receptors to the CNS .Sensory nerve
fibers can be somatic (from skin, skeletal muscles or joints) or visceral
(from organs within the ventral body cavity)
2. Motor Division (Efferent division)
Conducts impulses from CNS to effector muscles/glands) through
motor nerve fibers. has two subdivisions:
a) The somatic nervous system allows voluntary control on
skeletal muscles .
b) The autonomic nervous system (ANS) regulates events that are
automatic or involuntary, such as the activity of smooth and
cardiac muscles and glands (involuntary nervous system). The
ANS itself has two parts, the sympathetic and parasympathetic.

18. Autonomic Nervous System
•It is apart of the PNS, composed of neurons
that regulate the activity of smooth and
cardiac muscle and glands.
•differs from the somatic nervous system in
that there is a chain of two motor neurons
(pre-ganglionic and post-ganglionic) from the
CNS to the effector.
•Two subdivisions serve the same organs with
different effects.

21. •(a) The Parasympathetic division is the “house keeping”
system . it controls:
• homeostasis.
•It maintains the normal digestion and elimination,
•the energy production. The first motor neurons are in the
brain or the sacral region of the spinal cord.
•The second motor neurons are in the terminal ganglia close
to the organ served. Post-ganglionic axons secrete
acetylcholine.

22. • (b) The sympathetic division is the “fight-or-flight” subdivision,
which prepares the body to cope with some threat.
• Its activation results in:
• increased heart rate and
• blood pressure. The pre-ganglionic neurons are in the gray matter
of the spinal cord. The post-ganglionic neurons are in sympathetic
chains or in collateral ganglia. Post-ganglionic axons secrete
norepinephrine.

23. Neurons
- are the functional and structural unit
of the nervous system.
-Have major functional properties:
1.Irritability – the ability to respond to a
stimulus and convert it into a nerve
impulse.
2.Conductivity – the ability to transmit
the nerve impulse to other neurons,
muscles, or glands.

24. Structure of Neuron

25. Functional Classification of Neurons
• Neurons are classified according to the direction the nerve impulse is traveling
relative to the CNS into:
1- Sensory (afferent) neurons:
•They carry impulses from sensory receptors (in the internal
organs or skin) to the CNS.
2- Motor (efferent) neurons:
•They carry impulses from the CNS to the viscera and / or
glands.
3- Associate neurons (interneurons):
•They connect the motor and sensory neurons in the neural
pathway.

26. Spinal cord reflexes and reflex arc
Definition: Spinal cord reflexes are simple behaviours produced by
central nervous system pathways that lie entirely within the spinal cord.
• Reflexes occur over neuronal pathways called reflex arcs.

27.  Receptor – detects the stimulus
 Afferent (sensory neuron) – transmits impulses to
the CNS
 Integration center – consists of one or more
synapses in the CNS
 Efferent (motor neuron) – conducts impulses from
integration center to an effector
 Effector – muscle or gland cell
◦ Responds to efferent impulses
 Contraction or secretion

28. Receptor
Sensory neuron
Integration center
Motor neuron
Effector
Spinal cord
(in cross section)
Interneuron
Stimulus
Skin
1
2
3
4
5
Five Essential Components to the Reflex Arc

29. Two types of reflexes:
1. Autonomic reflexes regulate the activity of smooth muscles, the
heart, and glands.
Autonomic reflexes regulate such body functions as digestion,
blood pressure and sweating.
2. Somatic reflexes include all reflexes that stimulate the skeletal
muscles. When you quickly pull your hand away from a hot object, a
somatic reflex is working.