Nervous and Immune Systems

• The nervous system has two divisions: the central nervous system and the peripheral nervous system.
• The central nervous system contains the brain and spinal cord.
• The peripheral nervous system is a network of nerves and neural tissues branching throughout the body.

Functions of the Nervous System

• Sensory input involves gathering information, monitoring changes inside and outside the body, with these changes being called stimuli.
• Integration is the process of interpreting sensory input and deciding if action is needed.
• Motor output involves a response to integrated stimuli which activates muscles or glands.

Structural Classification of the Nervous System

• The central nervous system (CNS) includes the brain and spinal cord.
• The peripheral nervous system (PNS) includes the nerves outside the brain and spinal cord.

Functional Classification of the Peripheral Nervous System

• Sensory (afferent) division: nerve fibers carry information to the central nervous system.
• Motor (efferent) division: nerve fibers carry impulses away from the central nervous system.
• The motor division has two subdivisions: somatic (voluntary) and autonomic (involuntary) nervous systems.

Neuron Anatomy

• Cell Body: contains the nucleus and a large nucleolus.
• Extensions Outside the Cell Body: dendrites conduct impulses toward the cell body, axons conduct impulses away from the cell body (only 1!).

Nerve Fiber Coverings

• Schwann cells produce myelin sheaths in jelly-roll fashion.
• Nodes of Ranvier are gaps in myelin sheath along the axon.

Functional Classification of Neurons

• Sensory (afferent) neurons carry impulses from the sensory receptors.
• Motor (efferent) neurons carry impulses from the central nervous system.
• Interneurons (association neurons) connect sensory and motor neurons.

Structural Classification of Neurons

• Multipolar neurons have many extensions from the cell body.
• Bipolar neurons have one axon and one dendrite.
• Unipolar neurons have a short single process leaving the cell body.

Regions of the Brain

• Cerebral hemispheres.
• Diencephalon
• Brain stem.
• Cerebellum.

Lobes of the Cerebrum

• Fissures (deep grooves) divide the cerebrum into lobes.
• Surface lobes of the cerebrum: frontal, parietal, occipital and temporal lobes.

Layers of the Cerebrum

• Gray matter is the outer layer of the cerebrum.
• Gray matter is composed mostly of neuron cell bodies.

Diencephalon

• Sits on top of the brain stem and is enclosed by the cerebral hemispheres.
• Made of three parts: thalamus, hypothalamus and epithalamus.

Thalamus

• Surrounds the third ventricle
• Considered the relay station for sensory impulses.
• Transfers impulses to the correct part of the cortex for localization and interpretation.

Hypothalamus

• It is under the thalamus.
• An important autonomic nervous system center.
• Regulates body temperature, controls water balance, and regulates metabolism.

Epithalamus

• Forms the roof of the third ventricle.
• Houses the pineal body (an endocrine gland).
• Includes the choroid plexus, which forms cerebrospinal fluid.

Brain Stem

• Attaches to the spinal cord.
• Parts of the brain stem: midbrain, pons, and medulla oblongata.

Midbrain

• Mostly composed of tracts of nerve fibers.
• Contains reflex centers for vision and hearing.
• The cerebral aqueduct connects the 3rd and 4th ventricles.

Pons

• The bulging center part of the brain stem.
• Mostly composed of fiber tracts.
• Includes nuclei involved in the control of breathing.

Medulla Oblongata

• Lowest part of the brain stem that merges into the spinal cord.
• Includes important fiber tracts.
• Contains control centers for heart rate, blood pressure, breathing, swallowing and vomiting.

Cerebellum

• Has two hemispheres with convoluted surfaces.
• Provides involuntary coordination of body movements.

Protection of the Central Nervous System

• Scalp and skin.
• Skull and vertebral column.
• Meninges.

Meninges

• Dura mater: double-layered external covering with periosteum attached to skull surface and meningeal layer as outer brain covering.
• Arachnoid layer: middle layer that is web-like.
• Pia mater: internal layer that clings to the surface of the brain.
• Folds inward in several areas.

Spinal Cord

• Extends from the medulla oblongata to the region of T12.
• Below T12 is the cauda equina, a collection of spinal nerves.
• Enlargements occur in the cervical and lumbar regions.

Spinal Cord Anatomy

• Exterior white mater consists of conduction tracts.
• Internal gray matter consists mostly of cell bodies, including dorsal (posterior) and anterior (ventral) horns.
• Central canal is filled with cerebrospinal fluid.
• Meninges cover the spinal cord.
• Nerves leave at the level of each vertebrae.
• Dorsal root is associated with the dorsal root ganglia, collections of cell bodies outside the central nervous system.

Peripheral Nervous System

• Includes nerves and ganglia outside the central nervous system.
• Nerve is a bundle of neuron fibers bundled by connective tissue.
• There is a pair of spinal nerves at the level of each vertebrae for a total of 31 pairs.
• Ventral rami form cervical plexus (C1-C5) and brachial plexus (C5-C8, T1).

Autonomic Nervous System

• Involuntary branch of the nervous system consisting of only motor nerves.
• Divided into sympathetic and parasympathetic divisions.
• The Sympathetic nervous system is responsible for the 'flight or fight' responses.
• It increases alertness, metabolic rate, respiration, blood pressure, heart rate, and sweating while decreasing digestive and urinary function.
• The parasympathetic nervous system counteracts the responses of the sympathetic system, restoring homeostasis.

The Human Immune System

• The immune system is the body's defense against disease-causing organisms, malfunctioning cells, and foreign particles.
• The first line of defense is the skin.
• The dead, outer layer of skin, known as the epidermis, forms a shield against invaders and secrets chemicals that kill potential invaders.
• 40-50 thousand skin cells are shed every day.
• The first line of defense; mucus and cilia, As you breathe in, foreign particles and bacteria bump into mucus throughout the respiratory system and become stuck.
• Hair-like structures called cilia sweep this mucus into the throat for coughing or swallowing.
• First line of defense; saliva, contains many chemicals that break down bacteria.
• Thousands of different types of bacteria can survive these chemicals, however.
• First line of defense; stomach acid, Swallowed bacteria are broken down by incredibly strong acids in the stomach that break down your food.
• The stomach must produce a coating of special mucus or this acid would eat through the stomach!
• Tube inner surface; digestive System. –Tube outer surface; Skin.
• Plastic interior Body.
• Escherichia coli is common and plentiful in all of our digestive tracts due to; these bacteria are technically outside the body and aid in digesting material we cannot.
• Only if E.Coli are introduced in an unnatural manner can they break through the first line of defense and harm us
• The Second line of defense;white blood cells.
• If invaders actually get within the body, then your white blood cells (WBCs) begin their attack.
• WBCs normally circulate throughout the blood, but will enter the body's tissues if invaders are detected.
• White blood cells are phagocytes, cells which are responsible for eating foreign particles by engulfing them
• Once engulfed, the phagocyte breaks the foreign particles apart in organelles called Lysosomes
• Viruses enter body cells, hijack their organelles, and turn the cell into a virus making-factory.
• The cell will eventually burst, releasing thousands of viruses to infect new cells.
• Second line of defense;Interferon.
• Virus-infected body cells release interferon when an invasion occur.
• Interferon is a chemical that interferes with the ability to viruses to attack other/not infected body cells
• Other white blood cells are T cells.
• T Cells, often called “natural killer" cells, recognize infected human cells and cancer cells.
• T-cells will attack these infected cells, quickly kill them, and then continue to search for more cells to kill
• The second line of defense The inflammatory response Injured body cells release chemicals called histamines, which begin inflammatory response
• capillaries dilate - pyrogens released, reach hypothalamus, and temperature rises - pain receptors activate - WBCs flock to infected area like sharks to blood
• Two divisions of the Immune system WBCs and T-cells
• The efforts of the WBCs known as phagocytes and T-cells is called the cell-mediated immune system
• protective Factor =Living cells ,Phagocytes -eat invaders T cells- kill invaders
• The other half of the immune system is called antibody-mediated immunity, meaning that is controlled by antibodies This represents the third line of defense in the immune system
• The Third line of defence Antibodies Most infections never make it past the first and second levels of defense Those that do trigger the production and release of antibodies; - proteins that latch onto, damage clunip, and slow foreign particles/ - Each antibody binds only to one specific binding site known as an atigen
• In antibody Production WBCs gobble up invading particles and break them up.
• they show the piece to t-cells, who identify the pieces and find specific B cells to help
• B calls produce antibodies that are equipped to find that specific piece on a new particle and attach
• In Immunity new particles take longer to identify, and a person remains ill until a new antibody can be crafted.
• Old Particles are quickly recognized, and a person may never become ill from that invader again This person is now known to be immuse
• Immunity = resistance to a disease causing organism or two types
• Active Immunity = you produce the antibodies - your body has been exposed to the antigen - Exposure = You fought it, you won, you remember it Planned - You detected it, eliminated it, and remember it
• Vaccine Are deliberately intruduced into - Immune -
• Because the bacteria has been killed or weakened, minimal symptoms occur Have eradicated or severely limited several diseases polio and smallpox • It deponds on the antigan • Some Dease cousing bacteria multiply into new forms thats our body desont recognis requiring annual vacanations, like flu Shot • Boostar Shut reminds than • Antagan
• The silent spread, AIDS
• The HIV viruses don't kill you-it cripples your immune sustun.
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