Transcript The Nervous System

The Nervous System
The Nervous System
• The nervous system is essentially a biological
information highway, and is responsible for
controlling all the biological processes and
movement in the body, and can also receive
information and interpret it via electrical signals
which are used in this nervous system
• It consists of the Central Nervous System (CNS),
essentially the processing area and the Peripheral
Nervous System which detects and sends
electrical impulses that are used in the nervous
system
The Central Nervous System
• The Central Nervous System is effectively the
center of the nervous system, the part of it that
processes the information received from the
peripheral nervous system. The CNS consists of
the brain and spinal cord. It is responsible for
receiving and interpreting signals from the
peripheral nervous system and also sends out
signals to it, either consciously or unconsciously.
This information highway called the nervous
system consists of many nerve cells, also known
as neurons
Nerve Cell
The Nerve Cell
• Each neuron consists of a nucleus situated in the cell body, where
outgrowths called processes originate from. The main one of these
processes is the axon, which is responsible for carrying outgoing
messages from the cell. This axon can originate from the CNS and
extend all the way to the body's extremities, effectively providing a
highway for messages to go to and from the CNS to these body
extremities.
• Dendrites are smaller secondary processes that grow from the cell
body and axon. On the end of these dendrites lie the axon
terminals, which 'plug' into a cell where the electrical signal from a
nerve cell to the target cell can be made. This 'plug' (the axon
terminal) connects into a receptor on the target cell and can
transmit information between cells
The Way Nerve Cells Communicate
• The "All-Or-None-Law" applies to nerve cell
communication as they use an on / off signal
(like an digital signal) so that the message can
remain clear and effective from its travel from
the CNS to the target cell or vice versa. This is
a factor because just like electricity signals,
the signal fades out and must be boosted
along its journey. But if the message is either 1
or 0 (i.e.) on or off the messages are absolute.
Brain Divisions
• There are three main components of the brain, namely the
brainstem, cerebellum and the forebrain.
• The Brainstem - The brainstem is the connection between the rest
of the brain and the rest of the central nervous system. It is
primarily concerned with life support and basic functions such as
movement
• The Cerebellum - Consisting of two hemispheres, the cerebellum is
primarily concerned with movement and works in partnership with
the brainstem area of the brain and focuses on the well being and
functionality of muscles. The structure can be found below the
occipital lobe and adjacent to the brainstem
• The Forebrain - The forebrain lies above the brainstem and
cerebellum and is the most advanced in evolutionary terms
The Forebrain
• The forebrain has many activities that it is responsible for and is
divided into many component parts.
• The Hypothalamus - A section of the brain found next to the
thalamus that is involved in many regulatory functions such as
osmoregulation and thermoregulation. The hypothalamus has a
degree of control over the pituitary gland, another part of the brain
situated next to it, and also controls sleeping patterns, eating and
drinking and speech. The hypothalamus is also responsible for the
secretion of ADH (Anti-Diuretic Hormone) via its neurosecretory
cells
• The Cerebrum - The cerebrum is the largest part of the human
brain, and the part responsible for intelligence and creativity, and
also involved in memory. The 'grey matter' of the cerebrum is the
cerebral cortex, the center that receives information from the
thalamus and all the other lower centers in the brain.
The Cerebrum
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The Cerebral Cortex - Part of the cerebrum, this part of the brain deals with almost
all of the higher functions of an intelligent being. It is this part of brain that deals
with the masses of information incoming from the periphery nervous system,
furiously instructing the brain of what is going on inside its body and the external
environment. It is this part that translates our nervous impulses into
understandable quantifiable feelings and thoughts. So important is the cerebral
cortex that it is sub-divided into 4 parts, explained below
Frontal Lobe - Found at the front of the head, near the temples and forehead, the
frontal lobe is essential to many of the advanced functions of an evolved brain. It
deals with voluntary muscle movements and deals with more intricate matters
such as thought and speech
Parietal Lobe - Situated behind the frontal lobe, this section deals with spatial
awareness in the external environment and acts as a receptor area to deal with
signals associated with tough.
Temporal Lobe - The temporal lobes are situated in parallel with the ears, they
serve the ears by interpreting audio signals received from the auditory canal
Occipital Lobe - This is the smallest of the four lobe components of the cerebrum,
and is responsible in interpreting nerve signals from the eye at the back of the
brain
Cerebral Cortex
Peripheral Nervous System
• The PNS consists of the nerves and is divided
into somatic and autonomic divisions. This
means: somatic nervous system ALWAYS
receives the stimulus from outside of the
organism and ALWAYS controls skeletal
muscles; autonomic nervous system ALWAYS
receives stimuli from inside of the organism,
and its efferents ALWAYS end on smooth
muscle, cardiac muscle or glands.
Peripheral Nervous System
• Somatic nervous system-carries messages
between the CNS and the body; consists of 12
pairs of cranial nerves and 31 pairs of spinal
nerves
• Autonomic nervous system- contains the
sympathetic (fight or flight response) and
parasympathetic (counteracts these actions)
nervous systems, which work together to
control involuntary body functions.