Nervous SystemNervous System

Nerve CellsNerve CellsNeuron Neuron designed to respond to surrounding environment designed to respond to surrounding environment

Axons and DendritesAxons and Dendrites•Small branches called dendrites receive chemical or electrical input Small branches called dendrites receive chemical or electrical input from the body. Neurons have many dendritesfrom the body. Neurons have many dendrites•Large branches are called axons, or nerve fibers, which carry Large branches are called axons, or nerve fibers, which carry information away from the cell in the form of a nerve impulse. information away from the cell in the form of a nerve impulse. Neurons commonly have only 1 axonNeurons commonly have only 1 axon•Nerves are simply bundles of axons. Axons are surrounded by a Nerves are simply bundles of axons. Axons are surrounded by a ““Band-AidBand-Aid”” of cells called Schwann Cells. Multiple layers of these of cells called Schwann Cells. Multiple layers of these cells create a sheath, or covering, around the axon called a myelin cells create a sheath, or covering, around the axon called a myelin sheath.sheath.•The myelin sheath, allows for the super-fast conduction of nerve The myelin sheath, allows for the super-fast conduction of nerve impulses. Nerves that are mylenated appear white. Mylenated nerves impulses. Nerves that are mylenated appear white. Mylenated nerves are used to send signals over long distances.are used to send signals over long distances.•Unmylenated nerves appear gray (like gray matter in the brain) and Unmylenated nerves appear gray (like gray matter in the brain) and are often used for processing nerve informationare often used for processing nerve information

Typical Nerve Cell (Neuron)Typical Nerve Cell (Neuron)

Neurons in 3 dimensional space Neurons in 3 dimensional space

Nerve Communication Nerve Communication

•Neurons communicate to each other by sending chemical signals to Neurons communicate to each other by sending chemical signals to one another. These chemicals are called neurotransmitters.one another. These chemicals are called neurotransmitters.

•Neurotransmitters leave one neuron, travel through a small Neurotransmitters leave one neuron, travel through a small intercellular space, to another neuron. That space is called a intercellular space, to another neuron. That space is called a synapse. synapse.

•At the end of each neuron is a receptor that monitors the internal At the end of each neuron is a receptor that monitors the internal condition of the bodycondition of the body

•Receptors transmit information down the dendrite, to the cell body. Receptors transmit information down the dendrite, to the cell body. Information is processed and sent out of the axon, away from the Information is processed and sent out of the axon, away from the neuronneuron

• The nervous system consists of millions of communicating neurons, The nervous system consists of millions of communicating neurons, neurotransmitters, receptors, and synapses.neurotransmitters, receptors, and synapses.

Neuron ClustersNeuron Clusters

Neurotransmitter ReleaseNeurotransmitter Release

Conduction of a Nerve ImpulseConduction of a Nerve Impulse

•Nerve impulse in a human travels more than 600 feet per secondNerve impulse in a human travels more than 600 feet per second• Resting nerve cells tend to have lots of negatively charged proteins Resting nerve cells tend to have lots of negatively charged proteins in them, and therefore have a negative charge to them (-65mv). in them, and therefore have a negative charge to them (-65mv). •Resting nerve cells also have lots of potassium inside the cell. Resting nerve cells also have lots of potassium inside the cell. •They also have lots of Sodium just outside the cellThey also have lots of Sodium just outside the cell

Action PotentialAction Potential

1.1. Action Potentials describe how a nerve impulse is generated and Action Potentials describe how a nerve impulse is generated and conducted throughout the bodyconducted throughout the body

2.2. The nerve cell is stimulated by an electric current, change in pH, or The nerve cell is stimulated by an electric current, change in pH, or a pinch, causing an action potentiala pinch, causing an action potential

3.3. Upon stimulation, Sodium gates in the nerve cell membrane open Upon stimulation, Sodium gates in the nerve cell membrane open and sodium rushes into the cell. This rush of positive ions causes and sodium rushes into the cell. This rush of positive ions causes the cellthe cell’’s charge to rise and spike (from -65mv to +40mv). This s charge to rise and spike (from -65mv to +40mv). This process is called depolarization.process is called depolarization.

4.4. After the initial rush, the sodium gates close (stopping sodium After the initial rush, the sodium gates close (stopping sodium movement) and potassium gates open. Potassium then rushes out movement) and potassium gates open. Potassium then rushes out of the cell. The loss of these positive ions causes the cell to return of the cell. The loss of these positive ions causes the cell to return to its resting charge (-65mv). This is called repolarization.to its resting charge (-65mv). This is called repolarization.

5.5. Eventually, the sodium which rushed into the cell and the Eventually, the sodium which rushed into the cell and the potassium which rushed out of the cell are pumped out of the cell potassium which rushed out of the cell are pumped out of the cell (Na) and into the cell (K). This is done by the sodium potassium (Na) and into the cell (K). This is done by the sodium potassium pump.pump.

6.6. During this time the nerve is in its refractory period.During this time the nerve is in its refractory period.

Action PotentialAction Potential

Divisions of the Nervous SystemDivisions of the Nervous System

Central Nervous SystemCentral Nervous System Brain and spinal cord Brain and spinal cord

Peripheral Nervous System Peripheral Nervous System All other parts of the body All other parts of the body

Somatic Nervous SystemSomatic Nervous System Nerves that are controlled Nerves that are controlled voluntarilyvoluntarily

Autonomic Nervous SystemAutonomic Nervous System Nerves that are controlled Nerves that are controlled involuntarilyinvoluntarily

Types of NeuronsTypes of Neurons

•Sensory Neuron Sensory Neuron Neurons with receptors on the end. Send Neurons with receptors on the end. Send signals to the brain.signals to the brain.•Motor Neurons Motor Neurons Carry nerve impulses to from the brain to Carry nerve impulses to from the brain to your musclesyour muscles•InterneuronsInterneurons Reside in the brain and spinal cord. Connect Reside in the brain and spinal cord. Connect sensory neurons to motor neuronssensory neurons to motor neurons

Parts of the BrainParts of the Brain• Brain StemBrain Stem contains the medulla oblongata and the pons. contains the medulla oblongata and the pons.

Located at junction of brain and spinal cordLocated at junction of brain and spinal cord• Medulla OblongataMedulla Oblongata contains clusters of neurons that control contains clusters of neurons that control

heartbeat, respiration, and blood pressure. Also contains neurons heartbeat, respiration, and blood pressure. Also contains neurons that control reflexes like swallowing, coughing, hiccups, and that control reflexes like swallowing, coughing, hiccups, and vomitingvomiting

• PonsPons Means Means ““bridgebridge””. Mostly aids in sending messages from MO . Mostly aids in sending messages from MO to spinal cord. Also has limited tactile, visual, and auditory to spinal cord. Also has limited tactile, visual, and auditory functionfunction

DiencephalonDiencephalon

• HypothalamusHypothalamus Maintains Homeostasis; Regulates hunger, thirst, Maintains Homeostasis; Regulates hunger, thirst, body temperature, and sleep. Hypothalamus also controls the body temperature, and sleep. Hypothalamus also controls the pituitary gland (growth)pituitary gland (growth)

• Thalamus: Post office of the brain. Receives incoming messages Thalamus: Post office of the brain. Receives incoming messages from the spinal cord and processes the information, sends the from the spinal cord and processes the information, sends the information to the appropriate part of the braininformation to the appropriate part of the brain

Cerebellum and CerebrumCerebellum and Cerebrum

CerebellumCerebellum2 portions separated by the brain stem2 portions separated by the brain stemCerebellum functions in skeletal muscle coordination; maintaining Cerebellum functions in skeletal muscle coordination; maintaining

balance and posture. Receives information from the inner earbalance and posture. Receives information from the inner earCerebrumCerebrumSurface area of the brainSurface area of the brainArea of the brain devoted to consciousness. Area of the brain devoted to consciousness. 4 surface areas: Frontal, Parietal, Temporal, and Occipital4 surface areas: Frontal, Parietal, Temporal, and OccipitalFrontal Lobe: formation of conscious thought; thinkingFrontal Lobe: formation of conscious thought; thinkingParietal Lobe: Sensations: Pain, pressure, touchParietal Lobe: Sensations: Pain, pressure, touchTemporal Lobe: Hearing and smellingTemporal Lobe: Hearing and smellingOccipital Lobe: Visual ProcessingOccipital Lobe: Visual Processing

Other Interesting Parts of the BrainOther Interesting Parts of the Brain

Corpus callosumCorpus callosum Part of the frontal lobe that splits into right and Part of the frontal lobe that splits into right and left sides. Over excitation of CC can cause epileptic seizures.left sides. Over excitation of CC can cause epileptic seizures.

Limbic SystemLimbic System Lies below the cerebrum in the frontal lobe. Lies below the cerebrum in the frontal lobe. Controls emotions such as love, anger, sadness, guilt, etc... Also Controls emotions such as love, anger, sadness, guilt, etc... Also controls sense of memory (long and short term)controls sense of memory (long and short term)

Destruction of neurons in the limbic system leads to AlzheimerDestruction of neurons in the limbic system leads to Alzheimer’’s s diseasedisease

Most hallucinogenic drugs affect neurons in the limbic systemMost hallucinogenic drugs affect neurons in the limbic system