Module 9: Fundamentals of the Nervous System Flashcards
2 main divisions
central nervous system
peripheral nervous system
Central nervous system consists of
brain
spinal cord
Peripheral nervous system consists of
nerves (cranial and spinal)
Ganglia
PNS divided into 2 systems
Somatic nervous system (voluntary)
Autonomic nervous system (involuntary)
Somatic nervous system
under voluntary control
stimulates skeletal muscles
Autonomic nervous system
under involuntary control
Controls organs, glands, cardiac muscle, smooth muscle
Divided into sympathetic nervous system and parasympathetic nervous system
Sympathetic nervous system
division of autonomic nervous system
reacts in emergency situations “fight or flight”
Parasympathetic nervous system
division of autonomic nervous system
involved in digestion, elimination, glandular activities
“feed and breed”, “rest and digest”
Functions of nervous system (3)
SIM
Sensory: gather info from external and internal environment
Integrative: info is processed/interpreted by brain (creates a plan)
Motor: nerves convey info from CNS towards muscles and glands (converts the plan into action)
2 types of nervous tissue cells
neurons and neuroglia
Neurons
nerve cell are electrically active cells
conduct messages throughout body
consist of cell body and branching fibers (dendrites and axon)
Cell body
aka perikaryon or soma
contains all organelles except centrioles
Nissl bodies-specialized layers of rough ER
Dendrites
processes that look like tree branches
receive and transmit stimuli towards the cell body
Axon
long extension that transmits into away from cell body
axon forms branches near its ends (axon terminals, synaptic knobs)
side branches called collaterals
axons surrounded by myelin sheath
Neuron classification (structural)
multipolar- 99% of neurons, many dendrites and 1 axon
bipolar- 1 axon and 1 dendrite
unipolar-one process that extends from cell body
Neuron classification (functional)
sensory (afferent)-carry impulses from peripheral receptors to CNS
motor (efferent)- carry impulses from CNS to effectors
Interneurons (association)- lie entirely within CNS, receive input from sensory and communicate with motor neurons
Neuroglia
aka glia
do not conduct nerve impulses
Role is to support, nourish and protect neurons
capable of mitosis
6 types of neuroglia
Astrocytes (CNS) Oligodendrocytes (CNS) Microglia (CNS) Ependymal cells (CNS) Schwann cells/ neurolemmocytes (PNS) Satellite cells (PNS)
nerve
bundle of nerve cell fibers (axons and dendrites) following same path
usually contain sensory and motor neurons
found only in PNS
Tract
bundle of nerve cell fibers
in CNS only
Ganglia
clusters of neuron cell bodies
in PNS only
Nuclei
clusters of neuron cell bodies
in CNS only
Blood brain barrier
keeps harmful substances out of the brain
astrocytes form wall around outside of blood vessels
Myelin sheath
formed by myelin/myelin sheath
protects and insulates the axons of nerve cells in CNS and PNS
IN PNS: neurolemmocytes/ Schwann cells form sheath (plasma membrane called neuolemma)
IN CNS: oligodendrocytes form sheath (gaps between sheaths are called nodes of Ranvier)
White matter
nervous tissue in CNS appears white due to myelinated neurons
Grey matter
nervous tissue in CNS appears grey due to unmyelinated neurons
Cell membrane of neuron
Resting state- extracellular fluid dominated by Na and Cl, intracellular fluid dominated by K and proteins
Resting cell is polarized (charged) - excessive pos charges on outside of cell membrane, excessive neg charges on inside (membrane potential)
Action potential has developed and spot will become depolarized
Synapse parts (3)
Presynaptic neuron - neuron sending the impulse
Synaptic cleft- space between presynaptic and postsynaptic
Postsynaptic neuron- neuron receiving the impulse
How does action potential cross synaptic cleft to another cell
action potential arrives at synaptic knob
Presynaptic neuron releases neurotransmitter
Exocytosis(active transport)- neurotransmitter molecules released
Neurotransmitters diffuse across synaptic cleft until they reach receptors of postsynaptic neuron
Bind to receptors (opens ion channels and allows movement of Na across cell membrane)
Triggers the formation of an action potential in the postsynaptic cleft
4 types of neurotransmitters
Acetylcholine (ACh) - between neurons and skeletal muscle cells
Norepinephrine (NE) - aka noradrenaline, stimulates postsynaptic neurons
Dopamin- found in brain, regulates body and facial movement
Serotonin- found in brain, for temp regulation, sensory perception and onset of sleep
