Human nervous system

HUMAN NERVOUS
SYSTEM
1. CENTRAL NERVOUS
SYSTEM
2. PERIPHERAL NERVOUS
SYSTEM

CENTRAL NERVOUS SYSTEM OF
HUMAN BEING
► The human central nervous system is made up of;
► 1. Brain
► 2. Spinal cord
► The complete central nervous system consist of up to
100 billions inter-neurons
► Brain and spinal cord are protected in protected bony
armour, the skull and the vertebral column.
► Both the spinal cord and brain are covered in three
continuous sheets of connective tissue called meninges.
► A plasma like fluid, the cerebrospinal fluid (CSF)
bathing the neurons of CNS is yet another protection to
CNS.

BRAIN

► The brain of all vertebrates
develops from three
swellings at the anterior
end of the neural canal of
the embryo.
► Human brain is divided
into three parts;
► Fore-Brain
► Mid-Brain
► Hind-Brain

Fore-Brain:
► The human forebrain is
made up of;
► Telencephalon
► Diencephalon
► The telencephalon is the
largest part of fore-brain
it is differentiated into
two cereberal
hemisphere or
cereberum.

FORE-BRAIN
► Cereberal cortex is the largest and most complex part
of human brain.
► By means of a prominent groove, called the
longitudinal fissure, the brain is divided into two
halves called cerebral hemispheres.
► At the base of this fissure lies a thick bundle of nerve
fibers, called the corpus callosum, which provides a
communication link between the hemispheres
Although the right and left hemispheres seem to be a
mirror image of one another, there are important
functional distinctions.
► Each hemisphere of the cerebrum is subdivided into
four lobes.

FORE-BRAIN
► Frontal Lobe- associated with
reasoning, planning, parts of speech,
movement, emotions, and problem
solving.

► Parietal Lobe- associated with
movement, orientation, recognition,
perception of stimuli.

► Occipital Lobe- associated with
visual processing.

► Temporal Lobe- associated with
perception and recognition of auditory
stimuli, memory, and speech.

FORE-BRAIN(DIENCEPHALON):

The diencephalon consists of ;

1. Thalamus
2. Limbic system.

1. Thalamus:

► The thalamus is a large, dual lobed mass of grey matter cells
located at the top of the brainstem, superior to the
hypothalamus. The thalamus is a clearing house for sensory
impulses as it receives them from different parts of brain and
relays them to the appropriate part of the motor cortex.

► It controls the pleasure and pain.


► Limbic System:
► The limbic system, often referred to as the
"emotional brain", is found buried within the
cerebrum.

► Parts of Limbic System:
► Hypothalamus
► Amygdala
► Hippocampus
► Some other parts of thalamus

► Hypothalamus:

Hypothalamus regulates the autonomic nervous system via
hormone production and release. Affects and regulates
blood pressure, heart rate, Mood and motivation, hormonal
body processes, hunger, thirst, sexual arousal, sexual
maturation and the sleep/wake cycle.

► Amygdala:

It involved in signaling the cortex of motivationally significant
stimuli such as those related to reward, punishment and fear in
addition to social functions such as mating.


HIPPOCAMPUS:

It belongs to the
limbic system and plays
important roles in
long-term memory and
spatial navigation. In
Alzheimer's disease the
hippocampus is one of the
first regions of the brain to
suffer damage; memory
problems and disorientation
appear among the first
symptoms.

MID-BRAIN
► The midbrain is located between
the two developmental regions of
the brain known as the forebrain
and hind brain. In mammals,
particularly in man, mid brain is
relatively very small. Within the
midbrain is the
reticular formation, which is part
of a certain region of the
brainstem that influences motor
functions. It receives the sensory
information from spinal cord and
sends them to the fore-brain.

HIND-BRAIN

Cerebellum:
The cerebellum, or "little
brain", is similar to the
cerebrum in that it has two
hemispheres and has a highly
folded surface or cortex. This
structure is associated with
regulation and coordination
of movement, posture, and
balance.

HIND-BRAIN
► Pons : is a structure located on the brain stem. It is superior to
(up from) medulla oblongata, inferior to (down from) the
midbrain and ventral to (in front of) the cerebellum. The pons
measures about 2.5 cm in length. It mainly controls with sleep,
respiration, swallowing, bladder control, hearing, equilibrium,
taste, eye movement, facial expressions, facial sensation, and
posture.

► Reticular formation: is a group of nerve fibers located inside
the brainstem. Reticular formation important in regulating
Arousal, Attention, Cardiac Reflexes, Motor Functions,
consciousness or wakefulness.

HIND-BRAIN
Medulla oblongata:

► Medulla oblongata also called the
myelencephalon, the lowest part of
the brainstem. The medulla
oblongata looks like a swelling at
the tip of the spinal cord.

► The medulla oblongata regulates
the reflex responses that control
breathing, heart beat, blood
pressure, coughing, swallowing,
hiccupping, sneezing, vomiting,
digestion and other essential
involuntary functions.

BRAIN-STEM
The lower extension of the brain where it connects to
the spinal cord. It is formed by the combination of
medulla oblongata, pons and mid–brain. Neurological
functions located in the brainstem include those
necessary for survival (breathing, digestion, heart rate,
blood pressure) and for arousal (being awake and alert).
The brainstem is the pathway for all fiber tracts passing
up and down from peripheral nerves and spinal cord to
the highest parts of the brain.

SPINAL CORD
► It is thick, whitish nerve cord that lies below
the medulla and extends down through the
neural canal of vertebrae up to the hips.
► The spinal cord extends down from the brain
stem at the base of the skull, enclosed in the
vertebral column. Brain and spinal cord in
continuity comprise the central nervous
system.

► The outer layer of the spinal cord consists of
white matter, i.e., myelin-sheathed nerve
fibers. These are bundled into specialized
tracts that conduct impulses triggered by
pressure, pain, heat, and other sensory
stimuli or conduct motor impulses activating
muscles and glands.

SPINAL CORD ANATOMY
► The inner layer, or gray matter, has
a butterfly-shaped cross-section
and is mainly composed of nerve
cell bodies. Within the gray matter,
running the length of the cord and
extending into the brain, lies the
central canal through which the
cerebrospinal fluid circulates.

► The spinal cord mediates the reflex
responses to some sensory impulses
directly, i.e., without recourse to
the brain, as when a person's leg is
tapped producing the knee jerk
reflex.

Conduction Through Spinal Cord

PERIPHERAL NERVOUS
SYSTEM (PNS)
► In man, 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.
► PNS is further divided into
• Somatic Nervous System(Voluntary)
• Autonomic Nervous System(Involuntary)

Autonomic Nervous System
► Autonomic Nervous System is the division of
the peripheral nervous system that controls the
glands and the muscles of the internal organs.
► The Autonomic Nervous System operates on its
own and is involuntary.
► The two divisions of Autonomic Nervous System
are
► Sympathetic Nervous System
► Parasympathetic Nervous System

Comparison
SYMPATHETIC PARASYMPATHETIC
NERVOUS SYSTEM NERVOUS SYSTEM
► It is formed by the spinal ► It is formed by vagus nerve,
nerves arising from thoracic some of the cranial nerves and
and lumbar region. spinal nerves arising from
► It prepares the body for highly sacral region.
energetic activity such as ► It promotes all the internal
fight or flight. responses associated with a
It is responsible for relaxed state.
► Dilated Pupil It is responsible for
► Accelerated Heartbeat ► Contracted Pupil
► Slower Digestion ► Slower Heartbeat
► Stimulated glucose release ► Stimulated Digestion
► Accelerated breathing rate

Human nervous system

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