Central Nervous System
Brain & Spinal Cord
Peripheral Nervous System (PNS)
12 Pairs of cranial nerves, 31 pairs of spinal nerves... the sensory and motor neurons that connect the central nervous system
Somatic Nervous System (SNS)
Voluntary - any skeletal muscle tissue. (contains sensory neurons, voluntary and conciously controlled)
Autonomic Nervous System (ANS)
Involuntary - any SMOOTH muscle etc.(nerves that carry involuntary impulses to smooth muscle, cardiac muscle, and various glands)
"Fight or flight" - prepares for emergency. (the part of the autonomic nervous system that arouses the body to deal with perceived threats)
"Rest and Digest" - "Feed and Breed" - calms you down. (branch of the autonomic nervous system; it calms and relaxes the body)
Functions of The Nervous System
Orientation of the body and its parts, coordination and control. Assimilation of learning experiences (learning, memory, intelligence), instinctual behavior. (recieve messages, proccess info and responds to stimuli, controls and coordinate body functions)
Cells of the Nervous System
The structural and functional unit of the nervous system. (individual cells that are the smallest units of the nervous system)
Cytoplasmic Extensions. They collect and carry impulses TOWARD the cell body, have receptors for certain neurotransmitters.
Cell Body. Contains chromatophilic Nissl bodies (RER), contains most of the organelles, nucleus. Axon Hillock: Connects soma to axon, sums the potential to determine if the axon will fire. Neuron cell body. Eucromatic nucleus, nissl bodies (stacks of rough ER), numerous mitochondria, large perinuclear Golgi apparatus.
Autonomic Nervous System
Sympathetic Division and Parasympathetic Division
Peripheral Nervous System
Somatic Nervous System and Autonomic Nervous System
Structure of a Neuron
Cell body=perikaryon=soma (body), vast # short dendrites, receive signals from environment, singe axon (nerve fiber) arises from axon hillock
Cytoplasmic Extensions; Carries impulses AWAY from soma (cell body), synaptic knob contains neurotransmitters.
Structural Types of Neurons
Unipolar - Bipolar - Multipolar
(Fastest) Have a single point of attachment to perikaryon. Sensory: some aggregate into ganglia associated with spinal cord (reflexes). Used for sending signals to the brain quickly.
Area where the axon joins the cell body. Portion of the neuron that connects the cell body, soma, to the axon. The impulses the neuron receives from all the dendrites are summed up at the axon hillock to determine whether an action potential will be initiated.
(Mid-way) Neuron with one dendrite and one axon. Found in eyes, ears, nose. Ex: pathway of vision.
(Slowest) 1 axon, many dendrites. Most common, integration (interneurons).
Types of Neurons
Sensory - Motor - Interneuron
AFFERENT: Carry sensory information from sensory receptors TO the central nervous system.
EFFERENT: Carry sensory information FROM central nervous system to muscles and glands.
Relays information from the afferent neurons to the efferent neruons. Found between sensory and motor neurons, integration. (Does the "thinking")
Helper or Supporter Cells - Responsible for keeping the neurons alive an function at their peek. Cells which support, insulate, and protect neurons.
Schwann Cells (Myelin Producing)- Oligodendrocytes (Myelin Producing)- Microglia - Astrocytes - Ependymal Cells
(PNS) Neurilemmocyte - Produce a myelin sheath around PNS formed by wrapping around axon or dendrite.
(CNS) (Means Few Branches) Produces a myelin sheath around CNS, formed by wrapping cytoplasmic extensions around multiple axons or dendrites.
(CNS) Specialized Phagocytic (immune cells) of the CNS. Cells that protect neurons by engulfing disease causing microorganisms.
(CNS) Structural support, astrocytes, hold neurons in place, help form Blood Brain Barriers (BBB) and form scar tissue.
(CNS)Line the ventricles, regulates (makes) the cerebral spinal fluid (CFS) composition.
Process by which lipid membranes are formed and wrapped around axons in the central and peripheral nervous systems.
Electrical insulator of axons and dendrites - White lipoprotein (think plasma membrane) produced by Schwann Cells and Oligodendrites. Increases the speed of the signal conduction by using salutatory (jumping) conduction.
Covers the axon of some neurons and helps speed neural impulses. Comprised of the membranes of the insulating cell.
Outermost cell membrane of the Schwann Cell neuroglia.
Node of Ranvier
Gaps between segments in the myelin sheath that allow for conduction.
Steps of Neuronal Regeneration
Neurons are amitotic (if destroyed no repair but if damaged, can be repaired) 1. Axon is severed, everything distal of this will degenerates, particles are phagocytized. 2. Schwann cells regenerate and myelin tube may form. 3. Proximal portion sprouts and attracted to the regeneration tube. 4. Axon grows down and the connection is reformed.
Properties of Neuronal Tissue
Irritability - Conductivity
Capable of responding to stimulus.
Can turn a stimulus into electrical impulse or (action potential) AP
-70mv - Charge maintained by relative levels of anions.The difference in electric charge between the inside and outside of a neuron's cell membrane.
-55mv - Charge that must be reached for an AP to occur.
+30mv - Charge that is reached during impulse transmission. The "SPARK"
Increase in voltage toward the AP.Cell becomes less negative i.e. -70 to -55
Decrease in voltage back toward the resting potential.
<-70mv - Decrease in voltage beyond the resting potential.
Steps of Nerve Impulse Conduction
1. Stimulus occurs (must bring cell to threshold potential). 2. Depolarization occurs - VOLTAGE gated Na+ channels open, Na+ rushes in, increasing the intracellular voltage. 3. Action Potential is reached - electrical impulse that travels along the axon; REPOLARIZATION - VOLTAGE gated K+ channels open, K+ EXITS cell, Na+ gates CLOSE, voltage begins to decrease. 4.Hypolarization - Na+/K+ pumps begin to move Na+ OUT of the cell and K+ INTO the cell. 5. This exchange of electrons occurs sequentially along the axon. 6. Refractory Period - absolute vs relative.
Speed of Transmission
Based on many factors: 1. Diameter of fibers 2. Type of Fiber 3. Myelination 4. General Conditions of fibers
Junction of a neuron and another neuron. the junction between two neurons (axon-to-dendrite) or between a neuron and a muscle noun
Ex. "nerve impulses cross a synapse through the action of neurotransmitters"
Neuron before the synapse, contains synaptic vessicles with neurotransmitters
Set up of the Synapes
Presynaptic Neuron - Synaptic Cleft - Postsynaptic Neuron -
Gap between the pre and post synaptic neurons.
Neurons following the synapse, location of the receptors of the neurotransmitters.
Types of Postsynaptic Potentials
Excitatory (EPSP) - raises the intracellular voltage TOWARD the threshold. Inhibatory (IPSP) - drives the intracellular voltage further FROM the threshold
Chemical messengers found in the synapese. Ex: ACh, GABA, dopamine, norepinephrine, seratonin
Acts as neurotransmitters or neuromodulators.
Enkephalins - B-Endorphins - Substance P
neurotransmitters that regulate how much pain transmissions of slow fibers reach the brain (Pain relievers)
Very strong pain reliever (euphoria)
Substance - P
Strong neuropeptides, transmits pain within the spinal cord.
Organized group of neurons with in CNS
Making stimulation of a neuron easier.
2 or more presynaptic neurons per 1 post synaptic neuron.
1 presynaptic neuron per 2 or more post synaptic neurons.