Textbook Notes (363,140)
Canada (158,217)
BIOD27H3 (42)
A.Elia (24)

Chapter 8 Study Guide

12 Pages
Unlock Document

University of Toronto Scarborough
Biological Sciences

CHAPTER 8 - brain and spinal cord are integrating centres for homeostasis, movement, and many other body functions. They are the control centre of the nervous system, a network of billions or trillions of nerve cells linked together in a highly organized manner to form the rapid control system of the body - neurons designed to carry electrical signals rapidly, and in some cases, over long distances. They are uniquely shaped cells, and most have long, thin extensions, or processes, that can extend up to a meter in length - in most pathways, neurons release chemical signals, called neurotransmitters, into the extracellular fluid. In a few pathways, neurons are linked by gap junctions, allowing electrical signals to pass directly from cell to cell - intricacy of neural networks underlies the emergent properties of the nervous system: complex processes, such as consciousness, intelligence, and emotion Organization of the Nervous System - nervous system can be divided into 2 parts: o central nervous system (CNS) consists of brain and the spinal cord o peripheral nervous system (PNS) consists of afferent ( or sensory ) neurons and efferent neurons - sensory receptors throughout the body continuously monitor conditions in both the internal and external environments. They send information along afferent neurons to the CNS - CNS integrating centre for neural reflexes. Neurons integrate information that arrives from the afferent brancj of the PNS and determine whether a response is needed Cells of the nervous system - nervous system is composed of 2 cell types: o neurons basic signalling units o glial cells (or glia or neuroglia) support cells of nervous system - Neurons o Functional unit of nervous system o Uniquely shaped cells o Have long processes that extend outward from the cell body these are either dendrites ( receive incoming signals) or axons (carry outgoing information) o Shape, number and length of axons and dendrites vary from one neuron to the next o Neurons are classified according to structure: sensory neurons ( carry info about temp, pressure, light and other stimuli from sensory receptors to the CNS), interneurons (have complex branching processes that allow them to communicate with many other neurons) and efferent neurons o Long axons of both afferent and efferent peripheral neurons are bundled together with connective tissue into cordlike fibers called nerves that extend from the CNS to the targets of the component neurons. They may carry only afferent signals only ( sensory nerves ), efferent signals only (motor nerves), or signals in both directions (mixed nerves) Cell body: o control centre of the neuron o Has a nucleus and all organelles needed to direct cellular activity o Position in neurons varies, but mostly it is small, generally making up one-tenth or less of the total cell volume Dendrites: o Thin, branched processes that receive incoming information form neighbouring cells o Increase surface area of neuron allows it to communicate with multiple other neurons Axons: o A single axon originating from a specialized region of the cell body is called the axon hillock www.notesolution.com o Vary in length o Often branch sparsely along the length, forming collaterals. Each collateral ends in a swelling called an axon terminal (contains mitochondria and membrane-bound vesicles filled with neurocrine molecules) o Transmits outgoing electrical signals from the integrating center of the neuron to the end of the axon o Synapse region where an axon terminal meets its target cell o Presynaptic cell neuron that delivers the signal to the synapse o Postsynaptic cell cell that receives the signal o Synaptic cleft narrow space between the two cells o Slow axonal transport moves material by axoplasmic (cytoplasmic) flow from the cell body to the axon terminal o Fast axonal transport moves organelles at rates up to 400 nm per day - Glial cells o There are more of these cells compared to neurons o Provide structural stability to neurons by wrapping around them o $420574;L0209,-4OL.8:554799430:7438,39K0K0O52,L39,L3K420489,8L8419K0-7,L38 extracellular fluid by taking up excess metabolites and K+ o Peripheral nervous system has 2 types of glial cells: Schwann cells and satellite cells o CNS has 4 types: oligodendrocytes, microglia, astrocytes, and ependymal cells o Schwann cells in the PNS and oligodendrocytes in the CNS support and insulate axons by forming myelin, a substance composed of multiple concentric layers of phospholipid membrane. Myelin forms when these glial cells wrap around an axon, squeezing out the glial cytoplasm so that each wrap becomes two membrane layers o In CNS, one oligodendrocyte forms myelin around portions of several axons. In PNS, one Schwann cell associates with a single axon; a given axon may have as many as 500 Schwann cells, each wrapped around a 1-1.5mm segment of the axon o Between the myelin-insulated areas, a tiny region of axon membrane remains in direct contact with the extracellular fluid. These gaps, called the nodes of Ranvier, play an important role in the transmission of electrical signals along the axon ELECTRICAL SIGNALS IN NEURONS - Two factors that influence the membrane potential are: o Concentration gradients of ions across the membrane. Na+, Cl- and Ca(2+) are concentrated in the extracellular matrix and K+ ions are more concentrated in the cytosol o Membrane permeability to those ions. The resting cell membrane is much more permeable to K+ than to Na+ or Ca(2+). This makes K+ major ion contributing to the resting membrane potential - An average value for the resting membrane potential of neurons is -70mV (inside cell relative to outside). Neurons at rest are slightly permeable to Na+, and the leak of positive Na+ into cell makes resting membrane potential slightly more positive than it would be if the cell were permeable only to K+ - The GHK Equation Predicts Membrane Potential using multiple ions o Goldman-Hogkin-Katz equation o Used to calculate the resting M.P that results from contribution of all ions that can cross the membrane o Includes membrane permeability values as the permeability of an ion will influence its contribution to the M.P o Look at pg. 253 for equation o Predicts resting membrane potentials based on given [ion]s and membrane permeability o Can be used to predict what happens to the M.P when [ion]s or membrane permeabilities change - Ion movement across the cell membrane creates electrical signals o A change in either the K+ concentration gradient or ion permeabilities will change the M.P www.notesolution.com
More Less

Related notes for BIOD27H3

Log In


Don't have an account?

Join OneClass

Access over 10 million pages of study
documents for 1.3 million courses.

Sign up

Join to view


By registering, I agree to the Terms and Privacy Policies
Already have an account?
Just a few more details

So we can recommend you notes for your school.

Reset Password

Please enter below the email address you registered with and we will send you a link to reset your password.

Add your courses

Get notes from the top students in your class.