Nervous System Flashcards
master control and communication system
Nervous System
Nervous system three overlapping functions:
a. SENSORY INPUT
b. INTEGRATION
c. MOTOR OUTPUT
uses its millions of sensory receptors to monitor changes occurring both inside and outside the body
SENSORY INPUT
processes and interprets the sensory input and decides what should be done at each moment
INTEGRATION
causes a response, or effect, by activating muscles or glands
MOTOR OUTPUT
Aka “Glial cells”
Neuroglia
✓Supports the nerve cells/ neurons
✓Non-excitable cells
✓Support cells
Neuroglia
Macrophages in the CNS
MICROGLIA
Defense against infection et injury
MICROGLIA
Form & maintain myelin sheath in the CNS
OLIGODENDROCYTES
✓Star-shaped cells
✓Most numerous/ abundant
ASTROCYTES
Fnxs:
a. Provide structural support to the CNS
b. Take up extracellular K ion
c. Regulate the extracellular concentration of
neurotransmitter
d. Glycogen storage
e. Capable of cell multiplication/ replacement
gliosis
ASTROCYTES
Located in the ventricles et central canal of the
spinal cord
Assist in the circulation of cerebrospinal fluid (CSF)
EPENDYMAL CELLS
form the myelin sheaths around nerve fibers in the PNS
SCHWANN CELLS
act as protective, cushioning cells for peripheral neuron cell bodies
SATELLITE CELLS
(+) nucleus, cytoplasm with typical organelles
CELL BODY
Highly branched structures that carry impulses to the cell body
DENDRITES
Conducts away from cell body towards
another neuron, muscle/ gland
Emerges at cone-shaped axon hillock
AXON
Contain synaptic vesicles that can release neurotransmitter
AXON TERMINALS
whitish, fatty material which has a waxy appearance
protects and insulates
the fibers
increases the transmission rate of nerve impulses
MYELIN SHEATHS
gaps, or indentations
Facilitates Saltatory Conduction
NODES OF RANVIER
Collection of cell bodies inside the CNS
NUCLEI
Collection of cell bodies outside the CNS
GANGLIA
Bundles of nerve fibers running through the CNS
TRACTS
Bundles of nerve running through the PNS
NERVES
consists of dense collections of myelinated fibers (tracts)
WHITE MATTER
Contains mostly unmyelinated fibers and cell bodies
GRAY MATTER
Convey impulses into the CNS
Examples:
a. Cutaneous sense organs
b. Proprioceptors
SENSORY (AFFERENT)
Convey impulses from brain/ SC out through PNS to effector (muscle or organs)
MOTOR (EFFERENT)
Aka “associated neurons”
Most are within the CNS
Transmit impulses between neurons, such as between sensory and motor neuron
INTERNEURON
Motor, pyramidal, purkinje cell
Have several/ many dendrites and 1 axon
Most common type in the CNS
MULTIPOLAR
One dendrite and one axon
Example:
a. Retina of the eye
b. Inner ear
c. Nose
BIPOLAR
Have fused dendrite and axon
Sensory neurons of spinal nerves
Touch and pain sensory neuron
UNIPOLAR
Two major functional properties:
a. Irritability
b. Conductivity
Nervous Physiology
also called a nerve impulse in neurons
Action Potential
An increase in membrane potential of 15-30 mV usually is required to cause an explosive
development of action potential
All-or-None Principle
Overshoot period/ phase
Cause:
a. Fast opening of voltage voltage gated Na channel channel (opening of activation gate)
Na influx
Charge of the cell becomes positive
DEPOLARIZATION
Cause:
a. Fast closure of voltage-gated Na channels (closure of inactive gates)
K efflux
Charge of the cell becomes negative
REPOLARIZATION
Aka “Positive after potential”
Cause:
a. Slow late closure of voltage gated K channels
Charge of the cell becomes more negative
HYPERPOLARIZATION
A state wherein a (+) charge outside & (-) charge inside the cell
Activation of Na-K ATPase Pump
The charge of the cell returns to normal membrane potential
a. RMP of nn= -70 Mv
b. RMP of skeletal ms=
c. RMP of cardiac ms= -
d. RMP of GI tract= -56_56 mV
RESTING MEMBRANE POTENTIAL
Period during which a 2nd AP cannot be elicited even with a strong stimulus
At the peak of depolarization
ABSOLUTE REFRACTORY PERIOD
Starts at 1/3 o repolarization onwards
Stronger than normal stimulus elicits new AP
RELATIVE REFRACTORY PERIOD
