September 17 - Intro to NS.docx

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Anatomy and Cell Biology
Anatomy and Cell Biology 3319

September 17, 2013 Introduction to Central Nervous System Pp. 348-355 & 359-360 1) Know and understand the basic functions of the nervous system and the divisions responsible for these functions 2) Know the anatomical parts of a neuron, the types of neurons and compare the types of neurons found in the nervous system - Simple: pain reflex o Ex. Step on sharp object = you retract foot o Signal doesn’t need to travel to brain o Fast and important for survival Functions of the Nervous System 1) Sensory input (gathered information): it uses its millions of sensory receptors to monitor change occurring both inside and outside the body  Changes = stimulus  Sight, smell, taste, touch, pain, temperature, etc.  Afferent = input into brain 2) Integration: it processes and interprets the sensory input and makes decisions about what should be done at each moment 3) Motor output: it dictates a response by activating the effector organs, our muscles or glands - example in class: not testable o DLPFC (dorsal lateral prefrontal cortex): area where you set goals  The brains of people who were non reactors (to stress) (most of population) were active in the DLPFC; the reactors weren’t o INS (insular cortex)  Pattern of activity in brain is different in this area too for reactors and non reactors o Difference in brain activity in these different brain areas Basic Divisions of the Nervous System 1) Central Nervous System a. Structure: brain and spinal cord b. Function: integrative and control centers i. Receives incoming sensory signals, interprets these signals, and dictates motor responses based on past experiences, reflexes, and current conditions 2) Peripheral Nervous System a. Structure: cranial nerves and spinal nerves (outside the CNS) i. Cranial nerves: carry signals to and from brain ii. Spinal nerves: carry signals to and from spinal cord iii. Spinal ganglia: areas where cell bodies of neurons are clustered b. Function: communication lines between the CNS and the rest of the body - Sensory (afferent = “carrying toward”/inward) division o These signals are picked up by sensory receptors located throughout the body and carried by nerve fibers of the PNS into the CNS o Structure: somatic and visceral sensory nerve fibers o Function: conducts impulses from receptors to the CNS - Motor (efferent = “carrying away”/outward) division o These signals are carried away from the CNS by nerve fibers of the PNS to innervate the muscles and glands (causing them to contract or secrete) o Structure: motor nerve fibers o Function: conducts impulses from the CNS to effectors (muscles and glands) - Somatic nervous system – interactions with environment o Structure: somatic motor (voluntary) o Function: conducts impulses from the CNS to skeletal muscles o Structure: somatic sensory fiber o Function: conducts impulses from the skin, muscles or bones (somatic body region – structures external to the ventral body cavity/outer tube) to the CNS - Autonomic nervous system (ANS) – visceral – within your body o Structure: visceral motor (involuntary) o Function: conducts impulses from the CNS to cardiac muscles, smooth muscles, and glands o Structure: visceral sensory fiber o Function: conducts impulses from the digestive tube, lungs, heart or bladder (visceral body region – structures within ventral body cavity/inner tube) o Sympathetic division  Function: mobilizes body systems during activity  Ex, to the heart o Parasympathetic division  Function: conserves energy  Function: promotes house-keeping functions during rest  Ex, to the bladder Subdivisions of PNS 1) Somatic sensory (SS): sensory innervation of the outer tube: skin, body wall, and limbs o General/widespread: touch, pain, pressure, vibration, temperature, and proprioception (sensing one’s own body) from the skin, body wall and limbs o Special/localized: hearing, equilibrium, and vision 2) Visceral sensory (VS): sensory innervation of the viscera o General: stretch, pain, temperature, chemical changes, and irritation in viscera; nausea and hunger o Special: taste and smell 3) Somatic motor (SM)/voluntary motor: o Motor innervation to skeletal muscles (outer tube) – causes contraction 4) Visceral motor (VM)/autonomic nervous system/involuntary motor: o Motor innervation to smooth muscle, cardiac muscles, and glands (inner tube) – causes contraction Nervous Tissue 1) Neurons/nerve cells: the excitable nerve cells that transmit electrical signals o Structural unit of the nervous system 2) Neuroglia: nonexcitable supporting cells that surround and wrap the neurons - they both develop from neural tube and neural crest Neurons - Signals are transmitted along the plasma membrane in the form of nerve impulses, or action potentials o Myelin sheath insulates the axon allowing the action potential to jump from one node of Ranvier to another (AP traveling faster) o Schwann cells: lay down myelin sheath in the PNS o Oligodendrocyte: insulate the axons ONLY in the CNS o There are some neurons in the PNS that their axons are unmyelinated  these axons are slow conducting - They have extreme longevity - neurons can live and function for over 100 years - They do not divide – cannot undergo mitosis, so can’t replace themselves if destroyed - They have high metabolic rate – requiring continuous and abundant supplies of oxygen and glucose - Cell body/soma: receptive region o All have a single nucleus, containing a nucleolus, surrou
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