 Composed of highly specialized structures called nerves and neurons .
 This resulted in an evolution of the most complex of all of the body systems.
 The scientific study of the nervous system is called neuroscience or neurobiology . (ex. Neurologist – MD)

 A fferent = A rrive in the CNS
 Sensory neurons – up to the CNS from specific sensors
 E fferent = E xit CNS
 Motor neurons – down from the CNS to a specific muscle group

KEY TERMS
 Although the nervous system is very complex, there are only two main types of cells in the nervous tissue.
 Neurons – the conducting cells of the nervous system (unidirectional).
 Neuroglia (glial cells) – type of nerve connective tissue that supports and nourishes neurons. Much more numerous and capable of mitosis.

 Cell body ( soma ) - main part of the neuron containing all cell organelles. If soma dies, the neuron dies (amitotic).
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Axon - long, cable-like projection of the cell carries the electrochemical message ( nerve impulse or action potential ) along the length of the cell.
Dendrites or nerve endings – are branch-like projections of the cell that make connections to other cells.

Axon terminals
Cell body - Soma
Nucleus
Dendrites
Axon
Myelin sheath
Neurilemma
Schwann cell nucleus
Node of ranvier

 Neuron cannot regenerate (amitotic)
– when it dies, it is gone for ever.
 Dendrites can connect to many other neurons – these can regenerate.
 Axon length to accommodate the path of information (origin to destination).
 Receptor neurons can perceive different type of stimulus .

 Sensory neurons - carry signals from the outer parts of your body into the CNS.
 Motor neurons (motoneurons) - carry signals from the CNS to the outer parts (muscles, skin, glands) of your body.
 Receptors - sense the environment and encode this information into electrochemical messages that are transmitted by sensory neurons.
 Interneurons connect various neurons within the brain and spinal cord.

 Neuron - is a single cell.
 Neuron - has the ability to gather and transmit electrochemical signal.
 Over long distances
 Speed varies with the function.
 Transmission in one direction only.
 Nerve - actually refers to a structure made up of the fibers of many neurons.
 Bundled up in a connective tissue.

 Made up of many nerves (bundles)
 Regional
 Specific
 Control is point to point
 Hormones are “ broadcasted ” throughout the body (also control).
 Can you explain the difference?

 Central Nervous System (CNS) – is made up of the brain and the spinal cord.
 Peripheral Nervous System (PNS) – is the collection of all the neurons
(nerves) outside of the brain or spinal cord.

Sympathetic vs.
Parasympathetic nervous system

 Central Nervous System represents the largest part of the nervous system.
 Includes Brain and Spinal Cord .
 The function of the Central nervous
System is that of the control centre.
 Contained within the Dorsal cavity :
 brain within the cranial subcavity
 the spinal cord in the spinal subcavity .

 Up to 100 Billion neurons.
 Born with 1 lb (0.5 kg) of brain tissue.
 About 3 lbs (1.5 kg) in an adult.
 Makes up 2% of the body weight.
 Consumes about 20% of Oxygen.
 Single neuron can interconnect to as many as 10,000 other neurons.

Human Brain

 The central nervous system is extremely delicate, and requires a high level of support and protection if it is to function correctly.
 Two layered:
 Bone – skull, vertebral column.
 Membranes – meninges (Dura,
Arachnoid and Pia mater) plus
Cerebrospinal fluid between P&A

 Centrally locate, surrounded by the cerebrum.
 Includes:
 Thalamus - two oval masses of gray matter that serve as relay stations for sensory impulses, except for the sense of smell, going to the cerebral cortex (80 % of the diencephalon).
 Hypothalamus - maintains homeostasis through regulation of many visceral activities.
 Epithalamus - the most dorsal portion. This small gland is involved with the onset of puberty and rhythmic cycles in the body (Pineal gland)

 Literally the ' stalk ' of the brain, through which pass all the nerves carrying messages into and out from the brain.
 Midbrain
 Pons
 Medulla Oblongata (Medulla)
 Also contains the cell bodies of the cranial nerves (12 pairs) – these nerves bypass spine.

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Alertness
Arousal
Breathing
Blood Pressure
Digestion
Heart Rate
Other Autonomic Functions
Relays Information Between the Peripheral
Nerves and Spinal Cord to the Upper Parts of the Brain

(12 prs)
 12 pairs of Cranial nerves:
 I-Olfactory nerve,
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II-Optic nerve,
III-Oculomotor nerve,
IV-Trochlear nerve,
V-Trigeminal nerve,
VI-Abducens nerve,
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VII-Facial nerve,
VIII-Vestibulocochlear nerve/Auditory nerve,
IX-Glossopharyngeal nerve,
X-Vagus nerve,
XI-Accessory nerve/Spinal accessory nerve and
XII-Hypoglossal nerve.

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 Detection of stimuli
 Interpretation of stimuli
 Response to stimuli
 Control of the internal environment
 Maintenance of the internal environment

KEY TERMS
 Sensory nervous system - carrying messages into the brain (up - afferent).
 Motor nervous system - carrying messages from the brain to the muscles and organs of the body (down - efferent).
 Central nervous system - performing the complex processing of incoming messages and formulating the outgoing messages.

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 CEREBRUM
 DIENCEPHALON
 MIDBRAIN
 PONS
 MEDULLA
 CEREBELLUM
Forebrain
Brainstem

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Largest part
Two halves –
( hemispheres ) divided by fissure
 5 Lobes (bones)
 Connected to communicate inbetween ( Corpus
Callosum )

 Frontal lobe
 Cognitive functions, speech, motor control, smell, behaviour, muscle mvts
 Occipital lobe
 Visual center
 Parietal lobe
 Receives/interprets general senses, taste, focuses on comprehension
 Temporal lobe
 Hearing, smell, learning, memory, emotions, language

 Provide examples of stimuli Mr.
Shaw ’s sensory nervous system may have detected, his cerebrum ’s interpretation, and possible responses to stimuli while at the dentist
** relate to Health Care
 Frontal – conversing with hygienist
 Temporal – sounds of tools
 Parietal – taste of fluoride
 Occipital – overhead light in eyes

The Cerebelum ( Hindbrain ) – is located just above the brainstem, beneath the occipital lobes at the base of the skull.
 coordination of voluntary motor movement
 balance and equilibrium
 muscle tone

 An unpleasant sensation , ranging in intensity from slight - through severe - to indescribable.
 Is a subjective experience , occurring only in consciousness, in the mind (awake).
 The severity and quality of pain is only describable by the person experiencing it .
 Often an emotional quality+bodily location .

 Nociception (pain reception)- a measurable physiological event.
 Uses the system which carries information, about inflammation, tissue damage, to the spinal cord and brain.
 Latin: poena meaning punishment = pain.
 All pain receptors are free nerve endings .
 Pain receptors do not adapt to stimulus.

 C4 and higher - all the muscles which control breathing will be paralysed.
 The person will need a mechanical ventilator to breath for them.
 C4 and T6 - the person is able to breath on their own, however, the intracostal muscles may be weakened or paralysed, therefore breathing may be done solely by the diaphragm.

 Testing touch receptors
 Two point discrimination
 method determines the minimum distance that can be sensed between two points of touch
 can be used to determine the approximate size of the receptive field that senses light touch.

 Assignment ** complete analysis individually and hand in