KIN 3304 1st Edition Exam 2 Study Guide Lectures 10 17 Lecture 10 September 22 The Nervous System can be divided into 2 parts The Central Nervous System and The Peripheral Nervous System The Central Nervous System consists of the brain and the spinal cord and is responsible for integrating processing and coordinating sensory input and motor output It also holds higher functions such as intelligence memory learning and emotion The Peripheral Nervous System consists of all of the remaining neural tissue outside of the CNS and it provides sensory information to the CNS and carries motor commands from the CNS to peripheral tissues The PNS is split into two subdivisions Afferent PNS and Efferent PNS The Afferent PNS brings sensory information to the CNS The afferent division begins at receptors that monitor the environment There are 3 receptors we talked about A dendrite sensory process of a neuron A specialized cell or cluster of cells like a muscle A complex sensory organ like the eye Then the stimulation of the receptor will provide information to the CNS The Efferent PNS carries motor commands to muscles and glands The efferent division begins at the CNS and ends at an effector An effector could be a muscle cell gland cell or another cell that performs a function The Efferent PNS can further be divided into the Somatic Nervous System and the Autonomic Nervous System Somatic Nervous System deals with our muscles and can be voluntary of involuntary Autonomic Nervous System deals with things we don t control Both the Afferent PNS and Efferent PNS have somatic and visceral sensory receptors Somatic sensory receptors monitor voluntary things like skeletal muscles Visceral sensory receptors monitor things that you don t control like breathing and digesting TQ Know Figure 13 2 There are different types of GLIAL CELLS in the CNS and the PNS The CNS has oligodendrocytes astrocytes microglia and ependymal cells but we only talked about the Oligodendrocytes and astrocytes The PNS has satellite cells and schwann cells We just talked about schwann cells Astrocytes CNS Largest and most numerous glial cells Have 5 functions o Control The Interstitial Environment Astrocytes have cytoplasmic processes which increase the SA of the cell so that it can exchange ions to the extracellular fluid of the CNS so that it therefore controls the interstitial environment of CNS The cytoplasmic processes also contact neurons and isolate them so that the neurons cant make chemical changes in the interstitial space of the CNS o Maintain BBB The neural tissues must be physically and biochemically separated from the blood at all times The cytoplasmic processes of the astrocyte cover the surface of the capillaries within the CNS and provide a blanket separating the interstitial fluid from the blood so that the hormones and chemicals in blood will not harm the neuronal function o Create a 3D Framework for CNS Astrocytes have microfilaments throughout the whole cell that provides mechanical strength Because of this astrocytes form a framework like lady liberty being built that supports the neurons of the brain and spinal cord o Repair Damaged Neural Tissue After damage to the CNS astrocytes stabilize the repair and then prevent another injury there by producing scar tissue o Guide Neuronal Development Astrocytes direct the growth of developing neurons in the embryonic brain by secreting neurotropic factor chemicals Oligodendrocytes CNS o The structures of these glial cells compared to astrocytes have smaller bodies but they tie their axons together Oligodendrocytes improve the function of neurons by wrapping the axons in myelin Many axons in the CNS are sheathed by Oligodendrocytes Oligos expand the plasmalemma creates a pad around the axon which creates a sheath composed of phospholipids Myelin Sheaths improve the action potential or nerve impulse speed The myelin sheath can form along the entire length of the axon The long myelinated areas are called Internodes The gaps between internodes are called Myelin Sheath Gaps or Nodes of Ranvier The area where most myelinated axons are is the white matter of the CNS The area where there are many UNmyelinated axons nerves and dendrites is called the gray matter of the CNS Loss of myelin loss of conduction as in the disease Multiple Sclerosis Schwann Cells PNS o Every peripheral neuron is covered by Schwann cells which are also called neurolemmocytes It can only myelinate about 1mm of an axon which is much less than what an oligo can The sheath of schwann cells is called neurilemma All Unmyelinated axons are enclosed by schwann cells Schwann cells also play a role in repairing damaged nerves Now we ll talk about NEURONS A Neurotransmitter is a chemical compound that is released by a neuron to communicate with another neuron Neurons can be classified into 3 groups sensory neurons motor neurons and interneurons Sensory neurons detect stimuli in the PNS and send that information to the CNS Motor neurons carry instructions from the CNS to peripheral effectors Interneurons in the CNS process sensory information and coordinate motor activity There are 3 kinds of Receptors o Exteroceptors o Provide information about the external environment that are in the form of touch temperature pressure and the special senses of sight smell and hearing o Proprioceptors o Monitor the position and movement of the muscles and joints o Interoceptors o Monitor the digestive cardiovascular urinary and reproductive systems and also provide sensations of deep pressure and pain and tastes Lecture 11 September 24 Neuronal Regeneration Neurons have a limited ability to recover after an injury After the injury the chromatophillic substance disappears and the nucleus moves away from where its supposed to be But there is such a thing called Wallerian Degeneration where at the injury site the axon deteriorates macrophages eat the debris and then schwann cells form a cord that follows the path of the original axon and schwann cells release growth factors to promote axonal regrowth If this new axon is cut new axons will emerge within hours But this isn t always the case In a common tearing or crushing of a neuron the axon will die and new axon segments will sprout a week or more later The Rate of Nerve Impulse depends on 2 properties of the axon that the action potential or electrical impulse is traveling through o The presence of a myelin sheath o If the axon is myelinated it will conduct 5 7x faster o The