THE
NERVOUS
SYSTEM
THE NERVOUS SYSTEM
• The nervous system is the master controlling and
communicating system of the body.
• The nervous system has 3 overlapping functions
1. The nervous system monitors changes – millions of sensory
receptors monitor change inside and outside the body. The
gathered info is called sensory input
2. The nervous system processes and interprets sensory input
– then makes decisions about what should be done. This
process is called integration
3. The nervous system then effects a response – it activates
muscles or glands. This response is called motor output
EX. You are driving and see a red light (sensory input),the
nervous system integrates the info, (red means stop) and your
foot steps on the brake (motor output)
NERVES
• Nerves are connected to the spinal cord and carry
messages or impulses to and from the brain.
• Nerve tissue is composed of 2 types of cells:
1. Neuroglia cells – they nourish, protect, and insulate the
neurons
2. Neurons – transmit information. There are 3 parts to a
neuron
1 Dendrites – have branches and conduct electrical
currents toward the cell body
2 Nucleus – keeps the cell alive
3 Axon –generate nerve impulses away from the cell
down to the axon terminals (the end of the axon) and
stimulate chemicals called neurotransmitters
• The spaces between the neurons are called synapses.
NERVES
HOW IS INFORMATION PASSED ALONG?
• The information received in a dendrite, passes
through the cell body, travels down the axon , out
the axon terminal, over/across the synapse, and on
to the next dendrite.
• Nerves are easily damaged and take a long time to
heal/regenerate (if at all).
• Some nerve fibres have a protective coating called
the myelin sheath, which also insulate the nerve fibre
• Nerve fibres with a myelin sheath can conduct
impulses faster than those without.
BASIC NERVE CELL
THE NERVOUS SYSTEM
STRUCTURAL CLASSIFICATION
The nervous system has 2 subdivisions
1. The Central Nervous System (CNS)
2. The Peripheral Nervous System (PNS)
THE NERVOUS SYSTEM
THE CENTRAL NERVOUS SYSTEM (CNS)
•
•
Consists of the brain and spinal cord
The CNS acts as the integrating and command centre
BRAIN
• Contained in and protected by the skull and covered by meninges
• The 3 main parts of the brain are:
1. The cerebrum – the largest part of the brain,
• It controls the senses, thought, memory, and learning.
• Also controls certain voluntary muscles, such as those used for
walking, talking and writing.
• Divides into 2 halves, the right and left hemisphere
• The right hemisphere controls the left side of the body and vice
versa
• The outside of the cerebrum is called the cerebral cortex.
• It controls the highest functions of the brain.
THE BRAIN
• The cerebrum is divided into 4 sections:
1. The Frontal Lobe – controls intellect, behaviour,
attention, creative thought etc.
2. The Occipital Lobe – controls vision and reading
3. The Parietal Lobe – sense of touch, some language
and reading
4. The Temporal Lobe - controls music, fear, some
hearing, language and speech
THE NERVOUS SYSTEM
2. THE CEREBELLUM
• Regulates and controls balance and equilibrium
• Makes body movement smooth and co-ordinated
3. THE BRAINSTEM
• Connects the cerebrum to the spinal cord.
• Contains the:
• Midbrain – relays messages between the medulla and the
cerebrum
• Pons - relays messages between the medulla and the
cerebrum. Also controls breathing
• Medulla oblongata – controls heart rate, BP, breathing,
swallowing and vomiting. Controls rage and aggression
http://www.youtube.com/watch?v=VF5PyeMG8Lo
THE NERVOUS SYSTEM
THE SPINAL CORD
• Approx 17-18 inches long.
• 2 way conduction pathway to and from the brain
• Major reflex centre
• Covered by 3 layers of meninges
1. Dura mater – tough outer layer
2. Arachnoid – middle layer
3. Pia mater – delicate inner layer
• The space in between the arachnoid and pia mater is
called the subarachnoid space.
• This space is filled with CSF – cerebral spinal fluid, a
watery fluid that circulates around the brain and spinal
cord and protects the CNS by acting like a cushion
THE NERVOUS SYSTEM
THE PERIPHERAL NERVOUS SYSTEM (PNS)
• Consists mainly of the nerves that extend from the brain
and spinal cord.
• Spinal nerves carry impulses to and from the spinal cord
• Responsible for carrying impulses from the skin,
extremities, and internal structures
• 31 pairs
• Cranial nerves carry impulses to and from the brain
• Primarily serve the head and neck
• Responsible for senses, temp, pressure, voluntary and
involuntary muscle control
• 12 pairs
THE NERVOUS SYSTEM
• The PNS is subdivided into 2
systems:
1. The Somatic Nervous
System – sends sensory
info to the CNS and allows
us to voluntarily control our
skeletal muscles
2. The Autonomic Nervous
System (ANS) – regulates
involuntary activities (heart,
organs, glands). The ANS is
then further subdivided into
2 more systems:
THE NERVOUS SYSTEM
1. The Sympathetic Nervous System – speeds up functions,
such as when you are frightened, angry, excited or
exercising. Often called the “fight or flight” response.
The sympathetic nervous system:
• Increases heart rate, BP, and BS (blood glucose)
• Dilates the bronchioles and skeletal muscles
2. The Parasympathetic Nervous System – slows down body
functions and is activated when you relax and your body is
not threatened in any way. Referred to as the “resting
and digesting” system. This system is concerned with:
• Digestion
• Elimination of urine and feces
• Conserving energy
The Nervous
System
Central Nervous
System
Brain
Cerebrum
Frontal Lobe
Occipital Lobe
Parietal Lobe
Temporal Lobe
Cerebellum
Peripheral
Nervous System
Spinal Cord
Brainstem
Midbrain
Pons
Medulla
Oblongata
Somatic Nervous
System
Autonomic
Nervous System
Sympathetic
Nervous System
Parasympathetic
Nervous System