A Presentation by:

Timothy Dominguez

Nathan Maglasang

Jose Mari Mendoza

Structures and Functions of the Cells and Nervous System

What is the Nervous System?A very complex systemOrgan System that contain neuronsDivided into two parts:

Central Nervous System (CNS)Brain and Spinal Cord

Peripheral Nervous System (PNS)Nerves and Ganglia

The Nervous System

The CNS consists of the Brain and the Spinal CordThe brain plays a central role in the control of

most bodily functions, that include:Awareness MovementsSensations

Some reflex movements can occur via spinal cord pathways without the participation of brain structures.

The Central Nervous System (CNS)

• Thoughts • Speech • Memory

Cerebrum - is the largest part of the brain and controls voluntary actions, speech, senses, thought, and memory. 

Frontal Lobes - located in the front of the brain and are responsible for voluntary movement and, via their connections with other lobes, participate in the execution of sequential tasks; speech output; organizational skills; and certain aspects of behavior, mood, and memory.

Parietal Lobes – processes sensory information such as temperature, pain, taste, and touch.

Temporal Lobes - processes memory and auditory (hearing) information and speech and language functions.

Occipital Lobes - receives and processes visual information.

The central structures of the brain include the thalamus, hypothalamus, and pituitary gland.

Thalamus - integrates and relays sensory information to the cortex of the parietal, temporal, and occipital lobes.

Hypothalamus - located below the thalamus, regulates automatic functions such as appetite, thirst, and body temperature.

Pituitary Gland - regulates the production of many hormones that have a role in growth, metabolism, sexual response, fluid and mineral balance, and the stress response.

Midbrain - located below the hypothalamus. Some cranial nerves that are also responsible for eye muscle control exit the midbrain.

Pons - serves as a bridge between the midbrain and the medulla oblongata. The pons also contains the nuclei and fibers of nerves that serve eye muscle control, facial muscle strength, and other functions.

Medulla Oblongota - the lowest part of the brainstem and is interconnected with the cervical spinal cord. The medulla oblongata also helps control involuntary actions, including vital processes, such as heart rate, blood pressure, and respiration, and it carries the corticospinal (that is, motor function) tract toward the spinal cord.

Amygdala - The amygdala is an almond-shape set of neurons located deep in the brain's medial temporal lobe.For processsing of emotions, the amygdala forms part of the limbic system.For fear responses and pleasure.

Hippocampus - the part of the brain that is involved in memory forming, organizing, and storing. forming new memories and connecting emotions and senses, such as smell and sound, to memories. acts as a memory indexer for long-term storage and retrieving them when necessary.

Broca's area – For Language comprehension,action recognition and production, and speech-associated gestures

Wernicke's area - It is involved in the understanding of written and spoken language.

The spinal cord is an extension of the brain and is surrounded by the vertebral bodies that form the spinal columnWithin the spinal cord are 30 segments that belong to 4 sections (cervical, thoracic, lumbar, sacral), based on their location:  

Eight cervical segments: These transmit signals from or to areas of the head, neck, shoulders, arms, and hands.  

Twelve thoracic segments: These transmit signals from or to part of the arms and the anterior and posterior chest and abdominal areas. 

Five lumbar segments: These transmit signals from or to the legs and feet and some pelvic organs. 

Five sacral segments: These transmit signals from or to the lower back and buttocks, pelvic organs and genital areas, and some areas in the legs and feet. 

A coccygeal remnant is located at the bottom of the spinal cord.  

Peripheral Nervous System DivisionsThe peripheral nervous system is divided into the following sections: 

Peripheral Nervous System Sensory Nervous System - sends information to the CNS from internal organs or from

external stimuli. 

Motor Nervous System - carries information from the CNS to organs, muscles, and glands. 

Somatic Nervous System - controls skeletal muscle as well as external sensory organs.

Autonomic Nervous System - controls involuntary muscles, such as smooth and cardiac muscle.

Sympathetic - controls activities that increase energy expenditures.

Parasympathetic - controls activities that conserve energy expenditures.

The Peripheral Nervous System (PNS)

Peripheral Nervous System ConnectionsPeripheral nervous system connections with

various organs and structures of the body are established through cranial nerves and spinal nerves. There are 12 pairs of cranial nerves in the brain that establish connections in the head and upper body, while 31 pairs of spinal nerves do the same for the rest of the body.

Sources:http://biology.about.com/od/organsystems/a/

aa061804a.htmhttp://www.emedicinehealth.com/

anatomy_of_the_central_nervous_system/http://library.thinkquest.org/5777/ner1.htmhttp://en.wikipedia.org/wiki/Nervous_system

Neurons  are nerve cells that transmit nerve signals to and from the brain

DIFFERENT TYPES OF NEURONS Sensory neurons or Bipolar neurons carry messages

from the body's sense receptors (eyes, ears, etc.) to the CNS.

Motoneurons or Multipolar neurons carry signals from the CNS to the muscles and glands.

Interneurons or Pseudopolare (Spelling) cells form all the neural wiring within the CNS. These have two axons (instead of an axon and a dendrite). One axon communicates with the spinal cord; one with either the skin or muscle.

Brain Cells

Neurotransmitters are the chemicals which allow the transmission of signals from one neuron to the next across synapses.

Acetylcholine: Associated with memory, muscle contractions, and learning.

Endorphins: Associated with emotions and pain perception. The body releases endorphins in response to fear or trauma

Dopamine: Associated with thought and pleasurable feelings.

Brain Cells

Glial cells make up 90 percent of the brain's cells. Glial cells are nerve cells that don't carry nerve impulses.

The various glial cells perform many important functions, including: digestion of parts of dead neurons, manufacturing myelin for neurons, providing physical and nutritional support for neurons, and more.

Brain Cells

Microglia are special immune cells found only in the brain that can detect damaged or unhealthy neurons.

Astrocytes are star-shaped glia that hold neurons in place, get nutrients to them, and digest parts of dead neurons. 

Oligodendrocytes are cells that coat axons in the central nervous system with their cell membrane forming a specialized membrane differentiation called myelin, producing the so-called myelin sheath.

Schwann cells are involved in many important aspects of peripheral nerve biology - the conduction of nervous impulses along axons, nerve development and regeneration, trophic support for neurons, production of the nerve extracellular matrix,and modulation of neuromuscular synaptic activity

Brain Cells

Synaptic TransmissionSTEPS: a.) In order to transmit a signal between two

neurons, an electrical impulse must be communicated over a synapse.

b.) When an action potential begins in a neuron, it travels down the axon.

c.) When the action potential reaches the axon terminal, calcium channels open, and calcium ions rush into neurons.

d.) The neuron makes and stores neurotransmitter in ventricles.

e.) When calcium bind to ventricles, the vesicles carry transmitter toward the presynaptic membrane.

f.) When the vesicles contact the axon terminal membrane, the neurotransmitter is released into the synaptic cleft.

g.) Neurotransmitter diffuses across the synaptic cleft and binds to receptors on the postsynaptic neuron.

h.) The postsynaptic neuron receptors are activated. In this case, these receptors allow Sodium in the neuron by facilitated diffusion, causing an action potential to start in the postsynaptic membrane.

i.) Neurotransmitters are released from receptors and diffuse back into the synaptic cleft.

j.) Vesicles recycle some neurotransmitter to prepare the neuron for its next action potential.

Calcium Ions – a factor in the clotting of blood.

Presynaptic membrane - The part of the cell membrane of an axon terminal that faces the cell membrane of the neuron or muscle fiber with which the axon terminal establishes a synapse.

Postsynaptic membrane - The part of the cell membrane of a neuron or muscle fiber with which an axon terminal forms a synapse.

Synaptic cleft - a narrow extracellular cleft between the presynaptic and postsynaptic membranes.

Axon - a process of a neuron that conducts impulses away from the cell body. Axons are usually long and straight.

Neuron ConductionDuring a thunderstorm, Luigi Galvani

touched a frog’s leg with a metal instrument and noticed the muscles twitching.

His conclusion was nerves do transmit impulses from one part of the body to another, but in a different way than in an ordinary conductor.

The electrical properties are different in neural conduction because it is slower and does not vary in strength

The Resting Potential of the Nerve Cell

There is an excess of negative ions inside the cell membrane and an excess of positive ions outside

Potassium(K+) , sodium ions(Na+), chloride (Cl--)Nerve cells use both passive diffusion and active

transport to maintain these differentials across their cell membranes.

Specialized proteins embedded in the nerve cell membrane function as voltage-dependant channels, passing through Na+ and K+ during nerve impulse transmission.

The Stimulated Nerve Cell

If a physical or chemical stimulus is strong enough to cause depolarization from the resting potential of 70 mV to around 50 mV, the voltage-dependant Na+ transmembrane channels open.

The influx of Na+ causes a local reversal of electric polarity of the membrane, changing the electric potential to about +40 mV

The Stimulated Nerve Cell

The sodium ions(Na+) channels then close again.The movement of K+ ions and slower action of

the Na+-K+ pump soon restore concentration differentials and electric gradient to the resting state.

The transient change in the electric potential across the membrane is the action potential. After depolarization, for a brief period (milliseconds), the Na+ channels cannot be stimulated. This is called the refractory period.

Nerve Impulse Propagation

The local depolarization at the site of the original stimulus causes passive diffusion of ions into areas adjacent to the site of the stimulus.

Because of the refractory period, the nerve impulse can only be propagated in one direction, away from the nerve cell body towards the terminal branches, to release neurotransmitter substances.

The myelin sheath is a good insulator, so ions cannot flow through it. 

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