Nervous System. Mosby items and derived items © 2008 by Mosby, Inc., an affiliate of Elsevier Inc....
-
Upload
daisy-julia-brooks -
Category
Documents
-
view
215 -
download
0
Transcript of Nervous System. Mosby items and derived items © 2008 by Mosby, Inc., an affiliate of Elsevier Inc....
Mosby items and derived items © 2008 by Mosby, Inc., an affiliate of Elsevier Inc.
• The nervous system is the communication and control system of an animal’s body.
• Composed of two main divisions:• ____________ Nervous System (CNS)
• Composed of brain and spinal cord• _______________ Nervous System (PNS)
• Consist of nerves that come off of the CNS and innervate rest of body
• Function of nervous system activities:• _____________ (sense changes within or outside the body and sends it
to the spinal cord and brain)• _____________ (brain and spinal cord receive, analyze, store, and
integrate the info to produce a response)• _____________ (an instruction of the body to do something)
Introduction
Mosby items and derived items © 2008 by Mosby, Inc., an affiliate of Elsevier Inc.
• Neuron: basic functional units of nervous system• High requirement for ____________.
• Brain must always have O2 supply
• Cannot ___________ but can _____________ cell processes if the cell body remains intact
• Neuroglia (glial cells; these are not neurons): provide structural and functional support and protection to neurons
Neuron•Soma/Perikaryon• Central cell body
•Cell processes• _____________ – receive stimuli/impulses from other
neurons and transmit information_____soma.• Can also be sensory receptors for heat, cold, touch,
pressure, stretch or other physical changes inside or outside the body
• Short and branched
• ________ - conducts nerve impulses _______ from soma towards another neuron or an effector cell (muscle, gland)• Long, single process
Myelin
• Axons are often covered in myelin (fatty/protein substance)• Nervous tissue containing myelinated
axons is called ___________ matter.
• Myelin sheath: cell membrane of glial cells tightly wrapped around the axon• _____________________ in the brain
and spinal cord • ____________ ______ in the nerves
outside the brain and spinal cord
• Myelinated axons conduct impulses
faster than unmyelinated ones
Nodes of Ranvier
• Multiple Schwann cells or oligodendrocytes cover the entire length of the axon
• _____________________: gaps in the myelin sheath between adjacent glial cells
• Myelin sheath and nodes of Ranvier work together to enhance the ___________ of conduction of nerve impulses along the axon.
Organization of Nervous System
1. Anatomical
• _________ nervous system (CNS)• Brain and spinal cord
• ___________ nervous system (PNS)• Extends outward from the central axis
toward the periphery of the body• Cranial nerves originate directly from the
brain• Spinal nerves emerge from the spinal cord
Organization of Nervous System
2. Direction of Impulses
• _____________ nerves - conduct impulses TOWARD CNS
• a.k.a. sensory nerves - conduct sensations from sensory receptors in skin and other locations to CNS
• ______________ nerves - conduct impulses AWAY from CNS
• a.k.a. motor nerves - cause skeletal muscle contraction/movement
• Some nerve fibers are sensory (optic), motor (oculomotor), or both (glossopharyngeal)
Organization of Nervous System3. Function: Autonomic vs. Somatic
• _________________ nervous system - actions under conscious, or voluntary, control• Motor nerves lead to skeletal muscle and cause limb or body movement• Example: turning your head when your name is called
• _________________ nervous system - controls and coordinates automatic functions• Motor nerves lead to smooth muscle, cardiac muscle, and glands• Example: slowing of the heart rate in response to an increased blood
pressure, stomach releasing HCl when food is present
3.______________________ Division (fight or flight)
4.______________________ Division (feed or breed)
Neuron Function: DEPOLARIZATION AND REPOLARIZATION
• Resting __________ - when neuron is not stimulated• But, it’s still working to maintain a resting state (Na/K pump)
• Resting __________ ____________- difference in electrical charge across neuronal membrane• Due to differences in distribution of positive and negative charges from
sodium, potassium, proteins, and other charged ions on either side of neuronal membrane
• Inside of the neuron ends up having a more negative charge than the outside• Resting membrane potential is a negative number (-70 mV), indicating the
negative charge inside the cell• The Na/K pump maintains a negatively charges resting membrane potential
Neuron Function• Na+/K+ pump: specialized molecules located in the neuron’s cell
membrane that maintains cell resting state.• Pumps ____ (Na+) out of neuron• Pumps ____(K+) into neuron Cell membrane becomes ________________
DepolarizationSTEPS: •Neuron receives external stimulus•______ channel opens on cell membrane•Na+ flow into cell by passive _____________
• Down the concentration gradient• Electrical gradient (opposites attract)
DepolarizationSTEPS:• During depolarization, inside of neuron goes from being
__________ to _________ charged due to inflow of Na+ ions• ACTION POTENTIAL = significant change in electrical charge
RepolarizationSTEPS:•Na+ channels close•______ channels open•K+ diffuses out of cell
• Electrical and concentration gradient, just like Na
•Resting potential (charge) restored• Cell is ___________________• But, Na+ is inside, K+ outside