The Nervous System Lecture PDF

The Nervous System Lecture on BIO108: General Physiology May G. Esquejo Instructor I, Biology Department CBSUA-CAS About the Nervous System: Anatomy and Organization Function: How it Controls and Communicates How do we process our Thoughts, A...

The Nervous System Lecture on BIO108: General Physiology May G. Esquejo Instructor I, Biology Department CBSUA-CAS About the Nervous System: Anatomy and Organization Function: How it Controls and Communicates How do we process our Thoughts, Actions and Emotions? Principles? FUNCTIONS OF THE NERVOUS SYSTEM FUNCTIONS OF THE NERVOUS SYSTEM gathering information To monitor changes occurring inside and outside the body; FUNCTIONS OF THE NERVOUS SYSTEM processing information to process and interpret sensory input and decide if action is needed; what should be done FUNCTIONS OF THE NERVOUS SYSTEM Response to information A response to integrated stimuli The response activates muscles, glands and other parts of the body Structural Classification of Nervous System Brain Central Nervous System (CNS) Spinal cord Nervous System Peripheral Nerves outside Nervous System CNS (PNS) Central Nervous System (CNS) Receives, interprets and sends signals to PNS 2 main parts: Brain – main control center Spinal cord – connects and relays nerve impulses to the brain Peripheral Nervous System: Classification Sensory (afferent) division Nerve fibers that carry information to the central nervous system Motor (efferent) division Nerve fibers that carry impulses away from the central nervous system down to the muscles and glands Peripheral Nervous System: Classification Motor (efferent) division Two subdivisions: Somatic ns – voluntary actions Autonomic ns- involuntary actions Nervous Tissue: Support cells in CNS Astrocytes Abundant, star-shaped cells Brace neurons Form barrier and responsible for for exchange of materials between capillaries and neurons Control the chemical environment of the brain (CNS)  Nervous Tissue: Support cells in CNS Microglia Spider-like phagocytes Immune defense of CNS; Dispose of debris Ependymal cells Line cavities of the brain and spinal cord Create, secrete and circulate cerebrospinal fluid Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Nervous Tissue: Support cells in CNS Oligodendrocytes Produce the insulating barrier in neurons called the myelin sheath Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Neuroglia vs. Neurons Neuroglia divides. Neurons do not. Most brain tumors are “gliomas.” Most brain tumors involve the neuroglia cells, not the neurons. Consider the role of cell division in cancer!  Nervous Tissue: Support cells in PNS Satellite cells Protect, surround and support neuron cell bodies Schwann cells Form myelin sheath Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Nervous Tissue: NEURONS Neurons = nerve cells Highly specialized cells made to transmit information and messages Major regions of neurons Cell body – nucleus and metabolic center of the cell Processes – fibers that extend from the cell body (dendrites and axons) Nervous Tissue: NEURONS Neurons life support is found in the cell body Nucleus, other materials needed to function Nervous Tissue: NEURONS Neurons life support is found in the cell body Nucleus, other materials needed to function Nervous Tissue: NEURONS Dendrites – “listeners” of neurons; picks up information Conduct impulses toward the cell body Nervous Tissue: NEURONS Axon– “talker” of neurons; long extension fiber transmits electrical impulses away from the cell body to the other cells Nervous Tissue: NEURONS Axon– “talker” of neurons; long extension fiber transmits electrical impulses away from the cell body to the other cells Nervous Tissue: NEURONS Neurons are some of the longest-lived cells in your body Neurons are IRREPLACEABLE. Amitotic-does not divide Neurons have huge appetite high metabolic rate, need constant and huge amount of supply of glucose and oxygen Axons and Nerve Impulses Axons end in axonal terminals Axonal terminals contain vesicles with neurotransmitters Axonal terminals are separated from the next neuron by a gap Synaptic cleft – gap between adjacent neurons Synapse – junction between nerves Axons and Nerve Impulses Postsynaptic cell Presynaptic cell 5 Na+ Synaptic vesicles Neuro- K+ containing transmitter Presynaptic neurotransmitter membrane Postsynaptic membrane Ligand- gated Voltage-gated ion channel Ca2+ channel 1 Ca2+ 4 Postsynaptic 2 6 membrane 3 Synaptic cleft Ligand-gated ion channels Axons and Nerve Impulses Presynaptic Postsynaptic cell cell Synaptic vesicles 5 Na+ Neuro- containing K+ Presynaptic transmitter neurotransmitter membrane Postsynaptic membrane Ligand- Voltage-gated gated Ca2+ channel ion channel 1 Ca2+ 2 4 Postsynaptic 6 membrane Synaptic cleft 3 Ligand-gated ion channels 1) When an AP depolarizes the membrane at the synaptic terminal it 2) opens voltage-gated Ca++ channels, 3) the Ca++ that gets in causes vesicles full of neuro-transmitter to empty (4). The neurotransmitter binds to ligand-gated ion channels. The result is a post-synaptic potential (PSP). PSPs are, unlike action potentials, graded. Sometimes PSPs generate a new AP, but not always. Functional Classification of Neurons Sensory (afferent) neurons Carry impulses from the sensory receptors Cutaneous sense organs Proprioceptors – detect stretch or tension Motor (efferent) neurons Carry impulses from the central nervous system Functional Classification of Neurons Interneurons (association neurons) Found in neural pathways in the central nervous system Connect sensory and motor neurons Neuron Classification Structural Classification of Neurons Structural Classification of Neurons Multipolar neurons Many extensions from the cell body Structural Classification of Neurons Bipolar neurons Has one axon and one dendrite Structural Classification of Neurons Unipolar neurons Has short single process leaving the cell body To be continued…. Study: Regions of the Brain and its functions