The Nervous System

The Nervous System Drew Grinsteinner Jacob McGoogan

Functions of the System • Movement • The control room for all muscle contractions • Senses • Taste • Touch • The nervous system allows us to observe and react to changes in our environment

Functions of the SystemMovement • Central Nervous System (CNS) • All intentional movements, feelings, thoughts and processes • Peripheral Nervous System (PNS) • All actions of the body that do not deal with the CNS. These are all essentially reactions. • Sounds Familiar….. Reactions are a feedback mechanism!

Functions of the System • Intentional movement (CNS) • These movements originate as nerve impulses from the brain • The impulses travel down the spinal chord and reach a particular muscle fiber • The neurons that transmit this impulse are called motor neurons

Functions of the System • Reactions (PNS) • Reactions are movements that do not deal with the CNS, but instead, the Peripheral Nervous System • Sensory Neurons transmit an impulse to interneurons located in the spinal chord • These impulses are then transferred to motor neurons connected to the muscle fiber it stimulates

Functions of the System • The Feedback Mechanism • Stimulus- A sudden force put onto the body that a sensory neuron picks up • Receptor- The sensory neuron that transmits a nerve impulse to the spinal chord. The impulse hits an interneuron and is sent back through a motor neuron pathway • Effector- The nerve impulse hits the motor neuron which then stimulates the muscle to contract briefly, causing a twitch

Structure of the Neuron • Nerve cells= Neurons • These cells are structural and functional units of the nervous system that are specialized to react to physical and chemical changes in the surrounding environment • These cells send nerve impulses which are in the form of electrochemical changes

Structure of the Neuron • Neurons have… The main rounded area which is the cell body • Off of the cell body are 2 types of attachments, dendrites and an axon Dendrites are the attachment that receive impulses Axons are the attachment that send impulses

Structure of the Neuron Cont. • All along the axon, Schwann Cells or Neurolemmocytes envelope the axon • The purpose of a Schwann Cell is to produce myelin • Myelinated Nerve cells appear white and whole groups of cells are referred to as white matter • Unmyelinated cells do not appear white and are viewed in a group as grey matter

Structure of the Neuron http://www.enchantedlearning.com/subjects/anatomy/brain/Neuron.shtml

Synapses • The junction between any two communicating neurons is called a synapses. • The impulses that are sent travel between many neurons in a series of complex nerve pathways. • The neuron carrying the impulse into the synapse is the sender or the pre-synaptic neuron • The Neuron receiving the impulse in a synapse is the receiver or the post-synaptic neuron

Axon end of synapses (Pre-Synaptic) • The distal end of the axon have either 1 or more extensions called synaptic knobs, which are absent in dendrites • When a nerve impulse reaches a synaptic knob, the synaptic vesicles in the knob release neurotransmitters • Neurotransmitters diffuse across the axon’s membrane and bind with specific receptors in the post-synaptic neuron

Dendrite end of the synapse (post-synaptic) • The post-synaptic neurotransmitter receptors receive the electro-chemical signals • The unused portion of the neurotransmitters get recycled by diffusing back in to the vesicles located in the axon • This process is then repeated until the nerve impulse reaches its destination. Ex: Muscle Fibers, Interneurons, or the Brain

Synaptic Transmission http://mycozynook.com/28_06aNeuronCommunicat-L.jpg

Central Nervous System(CNS) • The Central nervous system is composed primarily of the Brain and Spinal cord • Disruptions of the central nervous system can cause side effects ranging from paralysis to death. • So be careful

The Brain

The Brain • There are 5 lobes of the brain which include: • Frontal lobe • Occipital lobe • Parietal lobe • Temporal lobe • Insula lobe (inside the brain)

The Brain • The cerebellum is used to send signals to voluntary muscle control • The brain stem is used to send those signals outside the brain.

The Spinal Cord

The Spinal Cord • The spinal cord is made up of 31 segments each with a pair of spinal nerves • Also part of the CNS

The Spinal Cord • The spinal cord unlike the peripheral neurons can send messages to the nerves itself causing reflexes.

Peripheral Nervous System(PNS) • The peripheral nervous system is the nerves and nervous tissue outside of the central nervous system • Damage to these nerves are not as fatal and life changing unlike the central nervous system • The system is split in two categories the Autonomic and Somatic nerves.

Autonomic Vs. Somatic Somatic Nervous System The part of the PNS that functions independently Runs in two parts Sympathetic and Parasympathetic The part of the PNS that functions dependently Responsible for Senses and Cranial Nerves Autonomic Nervous System

Human Senses and Cranial Nerves

Human Senses and Cranial Nerves Optic Oculomotor • Primarily Motor • Transmit impulses that raise eyelids, move eyes, focus lenses, and adjust light entering eye • Sensory • Transmits the senses of vision

Human Senses and Cranial Nerves Trochlear Trigeminal • Mixed • Transmit messages to the mouth and tear glands • Primarily Motor • Transmit messages to move the eyes

Human Senses and Cranial Nerves Abducens Vestibulocochlear • Sensory • Transmit impulses to aid hearing and equilibrium • Primarily Motor • Transmit messages to move the eyes

Human Senses and Cranial Nerves Glossopharyngeal Vagus • Mixed • Transmit impulses to assist speech and swallowing • Mixed • Transmit impulses to throat and saliva glands as well as swallowing

Human Senses and Cranial Nerves Accessory Hypoglossal • Primarily Motor • Transmit impulses to the tongue • Primarily Motor • Cranial Branch Transmit impulses to the soft plate, pharynx, and larynx. • Spinal Branch Transmit impulses to the neck and back

Human Senses and Cranial Nerves Taste Vs. Smell Olfactory cells (sense of smell) Facial (sense of taste) The to senses are connected via limbic system which is responsible for emotions and memories Which means when you eat something you like it does not really taste good it is your body remembering it tasting good and displaying emotion accordingly.

Autonomic Nervous System(Sympathetic) • Preganglionic Fibers originate in the gray matter of the spinal cord • The axons leave through ventral roots traveling a short distance • They leave the spinal nerves and enter a member of the paravertebral ganglia • After this the postganglionic fiber returns to the spinal cord

Autonomic Nervous System(Parasympathetic) The preganglionic fibers of the parasympathetic division arise from the brain stem and the spinal cord From there they go to various viscera the relatively short postganglionic fibers go to specific muscles or glands

Diseases and disorders • Headaches Brain Tissue has no pain sensitive nerve cell therefore when somebody has a headache it is actually caused by blood vessels in the brain where other nerves in the brain transmit as pain. Migraines are just a more extreme case of the same concept.

Diseases and disorders • Multiple Sclerosis The immune system in this genetic disorder attacks the myelin in the nerve cell as a alien disease and starts to eat away at the myelin. As the myelin breaks down nerve impulses are disrupted causing many people with the disorder to lose balance and coordination.

Diseases and disorders • Epilepsy 1 in every 100 to 200 people have this condition where the brain temporally lose all control to process incoming and control skeletal muscle. The visible symptoms of this is seizures and loss of consciousness for the time the episode begins the symptoms can be treated through medication.

Thank you! Now lets play telephone to help learn these concepts

The Nervous System