A & P II Nervous System
neural pathways over which reflexes occur; have five essential components (receptor, sensory neuron, CNS integration center, motor neuron, and effector).
central mass of a neuron from which the axon and dendrites branch. AKA perikaryon or soma. The major biosynthetic center of a neuron.
short, tapering, diffusely branching extension of motor neurons.
neuron that releases the neurotransmitter during intercellular communication
neuron that receives the neurotransmitter during intercellular communication
has one process extending directly from the cell body which splits into a long dendrite and a long axon. ex: touch receptor
has two processes, one dendrite, one axon. ex:retina, auditory canal, olfactory epithilium
more than two processes, 1 axon, many dendrites. integrates incoming information ex: majority of neurons in the bran and body, all motor neurons, all interneurons.
(efferent neurons) carry impulses away from the CNS to effector organ. Mostly multipolar in structure. Part of the CNS.
(afferent neurons) transmit impulses from sensory receptor toward the CNS from the PNS. part of the PNS. All are unipolar.
nerve cells which are the structural units of the nervous system. Highly specialized cells that conduct messages in the form of nerve impulses from one part of the body to another.
neuron process that carries the impulses away from the nerve cell body (efferent process); the conducting portion of a nerve cell.
knob-like distal endings of the terminal branches of an axon.
site of release of neurotransmitter
bundles of intermediate filaments (neurofilaments) important in maintaining the cell shape and integrity.
Nerve Impulse. an electrical impulse generated and conducted along the length of an axon, when a neuron is adequately stimulated.
short-distance electrical signals or (incoming messages) that occur in the dendrites and cell body. SUB THRESHOLD stimulus.
short-lived CHEMICAL substance released from the synaptic end-bulb of a neuron (chemical component of a nerve impulse).
space between the axon terminal and the muscle fiber of a neuro-muscular junction.
small membranous sacs containing the nuerotransmitter.
"fight or flight" A division of the ANS that brings the body away from homeostasis.
"stay and rest" A division of the ANS that brings the body back towards homeostasis.
Found in the CENTER of the brain and spinal cord. composed of neuron cell bodies and neuroglial cells.
Found in the OUTER layer of the brain and spinal cord. composed of myelinated axons and neuroglial cells.
Rough endoplasmic reticulum (ER) of a neuron cell body responsible for protein synthesis.
Glial Cells. Six types (four in the CNS - astrocytes, microglia, ependymal cells, oligodendrocytes); two in the PNS (satellite cells, Schwann cells).
Inhibitory post-synaptic potential. A graded potential in post synaptic neuron that inhibits action potential generation; usually hyper-polarization.
Excitatory post-synaptic potential. Depolarizing graded potential in a post synaptic neuron.
occasional branches of an axon which extend at more or less right angles.
covers the myelin sheath of peripheral axons.
covers fascicles of nerve cells.
covers the entire nerve.
Central Nervous System - integrates information and draws conclusions. Afferent nerves - towards CNS; Efferent Nerves - away from CNS.
Peripheral Nervous System - gathers information about changes in the body's internal and external environment, responds to information via effector organs (muscles or glands).
List main functions of the nervous system:
1. Collection of stimuli and gather (5 senses)
2. Analyze and interpret stimuli (CNS)
3. Take action & respond (PNS)
Classify Neurons STRUCTURALLY
unipolar - has ONE process
bipolar - has TWO processes
multipolar - MORE than two processes
Classify Neurons FUNCTIONALLY
a. SENSORY (afferent)- transmit impulses from sensory receptor toward CNS from PNS/are UniPolar.
b. MOTOR (efferent)- carries impulses away from CNS to effector organ/ are multi-polar/confined to PNS
c. INTERNEURONS (association neurons)- lies between sensory and motor neurons/confined to CNS/99.9% of nervous system/ALL multi-polar
Describe function of basic neuroglial cells (helper cells): SCHWANN CELL
surround axons of PNS.
form myelin sheaths around peripheral axons. Protect from environmental threats and bacteria.
Describe function of basic neuroglial cells (helper cells): OLIGODENDROCYTES
-form myelin sheets around CNS axons (only around WHITE matter).
-Provide structural framework.
Describe function of basic neuroglial cells (helper cells): MICROGLIA
(PHAGOCYTES)phagocytic cells that migrate through CNS and remove foreign / degenerated material.
Describe function of basic neuroglial cells (helper cells): ASTROCYTES
help regulate external environment around neurons of CNS.
Describe function of basic neuroglial cells (helper cells): EPENDYMA
lines ventricles of the brain and central canal of the spinal cord. Manufactures CSF (cerebral spinal fluid).
Describe function of basic neuroglial cells (helper cells): SATELLITE CELLS
support neurons within the ganglia of PNS.
Explain how action potentials are generated and propogated along axons?
After the voltage (mV) from the threshold stimulus opens the FIRST sodium (NA+), it triggers a domino effect of cascade or DEPOLARIZATION down the length of the [post-synaptic] axon. The mV never degrades because it is 'refreshed' at each local region of membrane, until it reaches the last voltage-regulated ion gate at the next [pre]synaptic end-bulb, which releases calcium ions(CA+).
Stages of ACTION POTENTIAL
RESTING MEMBRANE POTENTIAL ---> depolarization --> wave of depolarization --> repolarization --> hyperpolarization --> RESTING MEMBRANE POTENTIAL
Relate the effects of GRADED POTENTIALS on the axon hillock...?
1. Short lived, localized changes in Membrane Potential
2. Begins in area beneath a synapse (post synaptic) and travels through dendrite and/or cell body.
3. Graded because the magnitude varies inversely with the time and distance traveled (its mV degrades over time and distance).
4. If 2nd stimulus occurs before 1st stimulus disappears, the two are addetive and result in summation of the axon hillock.
5. When graded potentials summate to threshold level at the axon hillock, an action potential (AP)is initiated and propagated along the axon.