Central Nervous System PDF

The Central Nervous System Veterinary Physiology I VS1107 LGS Lokugalappatti  Nervous system Composed of trillions of cells distributed in a network throughout the brain, spinal cord, and periphery These cells communicate with each other by electri...

The Central Nervous System Veterinary Physiology I VS1107 LGS Lokugalappatti  Nervous system Composed of trillions of cells distributed in a network throughout the brain, spinal cord, and periphery These cells communicate with each other by electrical and chemical signals They maintain homeostasis by coordinating the functions of internal organs, as well as mediating sensation, controlling movements, and encoding the fabulous complexity that is mind  Two categories of cells in the nervous system Neurons – The basic unit of the nervous system is the nerve cell, or neuron Neuroglia – Provide structural, metabolic, and protective support for neurons – Schwann cells, Astrocytes, Oligodendrocytes and Microglia  Organization of the Nervous System Central Nervous System(CNS) The Nervous System (Receive and process information; Initiate action) Peripheral Nervous System(PNS) (Transmit signals between CNS and the rest of the body)  Brain (Receive and process sensory information; Initiate responses; store memories; generate thought Central Nervous and emotions) System(CNS) (Receive and process information; Initiate action) Spinal cord (Conduct signals to and from the brain; control reflex activities)  Peripheral Motor Neurons Nervous (Carry signals from the CNS that control System(PNS) the activities of muscles and glands) (Transmit signals between CNS and Sensory Neurons the rest of the body) (Carry signals to the CNS from sensory organs) Cranial nerves 12 – pairs 11 pairs – in head 1 pair – in head and stretches up to visceral organs (Vagus nerve) Spinal nerves - in pairs - numbers vary with species  Somatic Nervous System (Control voluntary movements by activating skeletal muscles) Motor Neurons (Carry signals from the CNS that control the activities of Autonomic Nervous System muscles and glands) (Control involuntary responses by influencing organs, glands and smooth muscles)  Upper Motor Neuron (UMN) (Regulate the activity of LMN, Initiate voluntary movement and maintain relatively stable body posture and balance) Somatic Nervous System (Control voluntary movements by activating skeletal muscles) Lower Motor Neuron (LMN) (Relay the movement instructions provided by the UMN, to the muscles)  Sympathetic Division (Prepare the body for stress or energetic activity; “fight or flight”) Autonomic Nervous System (Control involuntary responses by influencing Parasympathetic Division organs, glands and (Dominates during times of “rest smooth muscles) and rumination”; directs maintenance activities)  Forebrain (Processes signals, stores memories, Brain creates thought) Midbrain (Coordinates signals) Hindbrain (Carries out the most basic functions)  Hypothalamus Thalamus (overall regulation of (Relay station the Endocrine System) channeling sensory information) Limbic system (Basic emotions, Forebrain/Proencephalon motivations, drives, and (Processes signals, stores behaviors) memories, creates thought) Cerebral Cortex (Higher thought)  Reticular formation (The “traffic cops” of the brain/ Filters sensory input, which allows us to Midbrain/Mesencephalon concentrate / Filtering can be affected by higher (Coordinates signals) thoughts  Medulla (Controls autonomic functions) Hindbrain/ Pons Rhombencephalon (Controls sleep (Carries out the most stages) basic functions) Cerebellum (Coordinates movement, stores some motor memory)  Neurotransmitters in CNS There are many different neurotransmitters in the CNS, each binding to a specific receptor type which has a distinct distribution and role within the CNS. Defects in many neurotransmitter pathways have been implicated in psychiatric disorders. The variety of neurotransmitters that operate within the CNS adds to the functional complexity of the brain. Different neurotransmitters can produce different responses on the same neurone; e.g., a neurone might be excited by serotonin but inhibited by the binding of GABA.  Neurotransmitters and receptors Neurotransmitter Receptor subtypes Glutamate Ionotropic receptors: AMPA, kainate, NMDA receptors; metabotropic receptors (mGluR1-8 subtypes) GABA GABAA-C subtypes Serotonin 5-HT receptors (5-HT1A-F, 5-HT2A-C, 5-HT3-7 subtypes) Noradrenaline α-adrenergic receptors (α1A-C, α2A-C subtypes); β-adrenergic receptors (β1-3 subtypes) Dopamine Dopaminergic receptors (D1-5 subtypes) Acetylcholine Cholinergic receptors: muscarinic receptors (M1-5 subtypes) nicotinic receptors Histamine Histaminic receptors (H1-4 subtypes) NMDA=N-methyl-D-aspartate; AMPA=α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid; GABA=gamma-aminobutyric acid 17