Responding to the environment: Human
Nervous system
Introduction: • The nervous system enables humans to
The nervous system (involving nerves) respond to stimuli. A stimuli must first be
and endocrine system (involving detected, processed and integrated before a
hormones) are two components that response can take place
help us respond to the environment • The nervous system enables humans to
respond to stimuli. A stimuli must first be
detected, processed and integrated before a
Introduction: response can take place
• Organisms need to detect and respond to • When receptors detect stimulus it is
stimuli through their nervous system and conducted as a nerve impulse along a
endocrine system network of nerves cells to the CNS (brain and
• Sense organs like the eye are made up of spinal cord) where the info is processed
receptor cells • The processed info is then conducted as
Human responses: nerve impulses from the brain and spinal
• The responses of humans is controlled by cord via nerve cells to the effectors
the nervous and endocrine system • The effectors are the organs (muscles or
• The nervous system consists of the brain, glands) that respond to the original stimulus
spinal cord and nerves which enables the
body to feel pain, heat and other sensations
and control movement
• The endocrine system helps control cell
metabolic reactions, various body processes
and cycles through the secretions of
hormones
• Hormones have an inhibiting effect on
target organs
• Hormones are carried by blood to their
target organs
• The homeostatic control system consists of
the nervous system and endocrine system.
There are 2 coordinating systems: These 2 systems Nervous tissue:
work together for
• Nervous system communication
and homeostasis in
• The nervous tissue consists of millions of
• coordinating system (hormones) the body by nerves called neurons
responding to the
external and • The connective tissue is known a neuroglia
internal
environmental which occurs between the neurons for
changes (stimuli)
nourishment and support
Human nervous system • Neurons can conduct nerve impulses from
• The human nervous system is composed of nerve tissue one part of the body to another
which in turn is composed of nerve cells called neurons • Neurons are the structural units of the
which are all interconnected
• Electrical nerve impulses are transmitted at a high speed
nervous system
along neurons • Electrical nerve impulses are transmitted at
What are the 2 main systems where the nervous system is sub- a high speed along neurons
dived into?
• Central nervous system (CPS)
• Peripheral nervous system (PNS)
, Responding to the environment: Human
Nervous system
Central nervous system: Cerebrum
o Nervous tissue is very soft, and most cells • The cerebrum forms the largest part of the
cannot repair or regenerate themselves. And brain
therefore the nervous tissue must be well • The outer layer, consisting of the grey
protected against injuries. matter, is known as the cerebral cortex. It
o The central nervous system is surrounded folds (gyri) and groove (sulci) that enlarges
externally by bone. The brain is enclosed by the the brain surface
skull and the spinal cord by the vertebral • White matter occurs on the inside
column • A deep longitudinal fissure (groove) divides
o The cartilaginous discs between the vertebrae the cerebrum into 2 halves the left and
and the s-shaped curvature aid shock right cerebral hemispheres
absorption and make the vertebral column • Each hemisphere is divided into lobes
more flexible. which are, in turn, associated with various
Consists of: functions of the cerebrum
• Brain • The lobes are frontal, temporal, parietal
• Spinal Cord and occipital
• Main function: is to receive nerve impulses • The 2 hemispheres are partially connected
from the receptors and interpret the to each other by a layer of white matter,
information and transmit it to the effectors to the corpus callosum
bring about the desired response • There are 4 cerebral ventricles (cavities) in
Structure of central nervous system: the brain that are filled with cerebrospinal
• Is protected by the bones of the cranium fluid
(brain) and vertebrae (spinal cord) Functions of the cerebrum
• Protective membranes called meninges enclose • Origin of all voluntary actions e.g. walking,
the brain and spinal cord jumping, speech
• Internally the brain is enveloped by 3 meninges • Receives and interprets nerve impulses
(cerebral membranes): from the sense organs where the
• The pia mater: The innermost sensations of sight, sound, smell, taste and
membrane that is tightly wrapped touch arise
around the brain and the spinal cord • Seat of higher mental functions such as
and rich in blood vessels; providing memory, intelligence, imagination,
oxygen and nutrients to the central emotions, planning, thought and power of
nervous system judgement
• Dura Mater: The tough outermost Corpus callosum
membrane that lines the skull cavity and • The corpus callosum is a C-shaped structure
spinal cord between the 2 halves of the cerebrum
• The Arachnoid membrane: A thin • It consists of white matter as it is made up of a
membrane between the pia mater and bundle of axons that connects the 2 cerebral
the dura mater hemispheres
• It is the largest bundle of nerve fibres in the
• Between the pia mater and the arachnoid is a brain with over 200 million axons
space filled with cerebrospinal fluid. Functions of the corpus callosum
Location and function of certain parts of the brain and the
spinal cord: • Conducts impulses between the 2
Brain is the enlarged upper part of the spinal cord and hemispheres of the cerebrum
is divided into the following main parts: • Forms a bridge for communication
1. Cerebrum 4. Medulla Oblongata 7. Thalamus between the hemispheres to coordinate
2. Corpus callosum 5. Midbrain 8. Hypothalamus
3. Cerebellum 6. Pons 9. Hypophysis/Pituitary gland
processes
, Responding to the environment: Human
Nervous system
Cerebellum Spinal cord
• The cerebellum is situated behind and below the • The spinal cord extends from the medulla
cerebrum oblangata and through the spinal canal of the
• It consists of 2 hemispheres, connected to each vertebral column to the lumbar region
other by a worm-like mass of nerve tissue, the The spinal cord consists of:
vermis • A central canal filled with cerebrospinal fluid runs
• The surface of the cerebellum also has grooves but through the Centre of the spinal cord from the
shallower and parallel than those of the cerebrum cerebral ventricle in the medulla oblangata
• The grey matter is situated on the outside of the • The grey matter forms an H-shape on the inside.
white matter The points of the H-shaped grey matter are known
• The matter is uniquely arranged like a branched as the dorsal and ventral horns
tree, hence ‘abor vitae’ • The white matter is on the outside it contains
Functions of cerebellum myelinated nerve fibres that extend to and from
• It coordinates and controls all voluntary actions to the brain
make smooth and precise movement possible • Spinal nerves arise from both sides of the spinal
• It coordinates and controls the muscle tone cord. Each spinal nerve has a dorsal root and
(tension in the muscles) to maintain balance and ventral nerve which enter and exit the spinal cord
posture Functions of the spinal cord
Medulla oblangata • It provides a pathway for nerve impulses to and
• The medulla oblangata is an extension of the spinal from the brain. Nerve impulses are transmitted
cord and has the same structure from the receptors, along sensory neurons in a
• It differs from the rest of the brain because the grey spinal cord. Impulses are then transmitted along
matter is on the inside and the white matter on the ascending tracts in the spinal cord to the brain. The
outside
impulses are transmitted from the brain via the
• The grey matter is arranged in a H-shape
motor neurons in descending tracts back down the
Functions of the medulla oblangata
spinal cord
• It transmits nerve impulses between the spinal cord
• The spinal cord contains reflex centers that initiate
and the brain
• It controls autonomic functions:
reflex actions. These reflex actions occur
• Rate and depth of breathing independently of the brain and protect the body
• Heartbeat from injury
• Vasomotor activity (widening and narrowing
of blood vessels)
• Peristalsis and vomiting
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