Nervous System Intro PDF

Intro to Nervous System Devin Mott PT, DPT Objectives Organize the nervous system structurally and functionally Define Afferent and Efferent Explain how an action potential occurs (general overview) Describe different neurotransmitters and their actions in the body Overview The...

Intro to Nervous System Devin Mott PT, DPT Objectives Organize the nervous system structurally and functionally Define Afferent and Efferent Explain how an action potential occurs (general overview) Describe different neurotransmitters and their actions in the body Overview The nervous system monitors conditions and takes corrective action, when necessary, to keep everything running smoothly. The control systems of your body are the nervous and endocrine systems which receive help from your special senses. Organization Central Nervous System (CNS): brain and spinal cord Peripheral Nervous System (PNS): everything outside of the brain and spinal cord Autonomic Nervous System (ANS): Controls involuntary components (cardiac muscle, smooth muscles, several glands) Somatic Nervous System: Controls all voluntary movement Nervous System Organization Structurally: ○ Central Nervous System Brain Spinal Cord ○ Peripheral Nervous System Cranial Nerves Spinal Nerves and their derivatives Functionally: ○ Autonomic nervous system ○ Somatic nervous system Parts and Basic Operations (1 of 4) The brain and spinal cord comprise the central nervous system (CNS) which controls the total nervous system. Everything outside the brain and spinal cord is part of the peripheral nervous system (PNS). Parts and Basic Operations (2 of 4) The input side of the (peripheral) nervous system is the sensory system. The output side of the nervous system is the motor system. Parts and Basic Operations (3 of 4) The somatic nervous system controls skeletal muscle and mostly voluntary movements. The autonomic nervous system controls smooth muscle and cardiac muscle, along with several glands. Parts and Basic Operations (4 of 4) The autonomic system is divided into two branches ○ Parasympathetic system deals with normal body functioning. ○ Sympathetic nervous system controls the “fight or flight” response system. Terms and Directions Afferent: ○ Carries SENSORY information to the CNS Efferent: ○ Carries MOTOR information away from the CNS to the body Terms Ion Channels ○ Proteins located in membrane of excitable calls Important: converts chemical or mechanical messages into electrical signals G-Proteins ○ “Memory” protein that allows for door to stay open longer Tissue Types The Main Actor: ○ The Cell Body: Nuclei: In the CNS Ganglia: In the PNS The Supporting Actor: ○ Glial Cells Neurons (1 of 3) All of the control functions of the nervous system must be carried out by a group of cells called neurons. Neurons have many branches and even what appears to be a tail. Each part of a neuron has a specific function. Neurons (2 of 3) Neuron body ○ Cell metabolism Dendrites ○ Receive information from the environment Axon ○ Generates and sends signals to other cells Neurons (3 of 3) Axon terminal ○ Where the signal leaves the cell Synapse ○ Where the axon terminal and receiving cell meet Figure 9–3 Neurons Soma: protein synthesis for neurotransmitters Dendrites: INPUT site to neuron Axon: OUTPUT portion of neuron Presynaptic Terminals: Transmitting portion of neuron; transmit information via neurotransmitters Neuron Types Multipolar: most common type - all motor neurons to skeletal muscle and those in the ANS Pseudounipolar: except for special senses - all sensory neurons in the PNS Classification of Neurons (1 of 2) Structure ○ Bipolar: Has two processes, one axon, and one dendrite ○ Unipolar: Has one process, split into central and peripheral projection ○ Multipolar: Has many processes, usually one axon and many dendrites Classification of Neurons (2 of 2) Function ○ Sensory neurons: input ○ Motor neurons: output ○ Interneurons: communication between neurons (association neurons) Central Nervous System Glial Cells Astrocytes : ○ most abundant, give support and nutrients to the neuron, controls chemical environment through mopping up of leaked K+, part of info processing in the brain. Plays role in blood brain barrier Microglial ○ play immune system role in CNS, monitors health Ependymal ○ aids in circulation on CFS through their cilia Oligodendrocytes ○ produce myelin sheath in CNS Peripheral Nervous System Glial Cells Satellite Cells ○ support and nutrients - astrocytes of the PNS. Function is largely unknown Schwann Cells ○ supplies myelin sheath in PNS - plays important role in nerve regeneration How Neurons Work (1 of 2) Neurons excitable cells ○ Carry an electrical charge at rest ○ Each time charged particles flow across a cell membrane, a tiny charge is generated ○ Send and receive signals via tiny electrical currents How Neurons Work (2 of 2) All three muscle types are excitable cells, as are many gland cells. Cells are like miniature batteries, able to generate tiny currents simply by changing the permeability of their membranes. Propagation of Information Overview: ○ Electrical potential is possible when the distribution of ions crease of difference in charges ○ Four types of channels: Leak: allows diffusion of a small number of ions at a constant rate Maintenance of osmotic gradients Modality Gated: open in response to force: stretch, touch, pressure Specific to sensory nerves Ligand Gated: open in response to a neurotransmitter Voltage Gated: important in action potential propagation Electric Potentials Resting Membrane Potential: ○ Typically about -70 mV ○ Maintained by NaK Pump Local Potentials: ○ Impulse Conduction: not an all or none Sensory system Action Potential ○ All or None Rapid Depolarization due to opening of voltage gated Na+ channels Decrease in Na+ Conduction due to closing of Na+ channels Rapid repolarization due to opening of voltage gated K+ channels How A Nerve Works Propagation of Action Potential Speed of Conduction: ○ Dependent on diameter of the axon ○ Myelination Saltatory Conduction Synapses Neurotransmitters Neurotransmitter Systematic Effect Pathologies Acetylcholine Either Excitatory or Alzheimer’s Disease Inhibitory Dopamine Either Excitatory or Parkinson’s Disease Inhibitory Glutamate Excitatory Stroke GABA Inhibitory Seizures Serotonin Inhibitory Major Depression