Unit 2 - Neurophysiology Flashcards
Chapter 8
what are the 3 functions of the nervous system?
- receiving info (using sensory neurons)
- integrating info (organizes and looks at already stored info)
- transduces info (send to appropriate target)
what is contained in the CNS and PNS?
CNS is purely just the brain and spinal cord and the PNS is everything else, consisting of sensory/afferent and motor/efferent neurosn
define soma
- center of chemical processes
- clusters of cell bodies in CNS is nuclei and in PNS is ganglia
define dendrites
- receive information
- transmits electrical signals towards soma
define axon
- cytoplasmic extension that sends out information
- transmits electrical signals away from soma
- bundles of axons in CND is tracts and in PNS is nerves
define axon terminal
- end of axon where it is the connection between other neurons and cells
- contains presynaptic part of connection
define nervous system
network of billions of nerve cells linked together in a highly organized manner to form the rapid control system of the body
define neurotransmitter
a chemical signal released by a neuron that influence the neuron’s target cell
what are the 2 divisions of the CNS?
The somatic motor controls skeletal muscles and the autonomic controls smooth and cardiac muscles, exocrine glands and some adipose tissues.
how is the autonomic division divided?
sympathetic is responsible for flight-or-fight response and parasympathetic is responsible for day-to-day activities (rest and digest)
define enteric nervous system
neurons in the wall of the gastrointestinal tract that are capable of sensing and integrating information and carrying out a response without input from the CNS. A possible 3rd division of the nervous system found in recent years.
What are the 3 steps in the signal pathway that go with the axon?
input signal (dendrites) –> integration (soma) –> output signal (presynaptic axon terminal)—> input signal (postsynaptic dendrite) –> and continues in this same pattern
what are the different classifications of neurons?
multipolar: many dendrites and branched axons
pseudounipolar: have a cell body located off one side of a single longaxon
bipolar: single axon and single dendrite coming from the soma
anaxonic: lack an identifiable axon but have many dendrites
define interneurons
neuron that is completely contained within the CNS, short for interconnecting neurons
what is the branch of a axon called?
collateral
define axon terminal
the distal end of a neruon where neurotransmitters are released into a synapse
define sensory neurons
carry info about temperature, pressure, light and other stimulus to the CNS
define nerve
a collection of axons running between the CNS and the peripheral target cells, both afferent and efferent peripheral neurons create this when bundled together
what are the different kinds of nerves
- afferent/sensory: receives info from receptor cell and cytoplasmic extensions and transmits it to CNS, located outside of CNS
- interneurons: inside CNS, transmits info and acts as integrating centre (gets afferent signal and send it efferent)
efferent/motor: get info from the interneurons, located in the CNS but transmit info away from CNS to effectors (muscles, glands, etc.)
define dendritic spines
projections of the dendrites membrane that increase surface area to be able to accept neural signals. can chance their size and shape in response to input from neighbouring cells
define axon hillock
the region of the axon where it joins the cell body, often contains the trigger zone
define axonal transport
movement of material between the axon terminal and the cell body
the axon is filled with cytoplasm but lacks ribosomes and ER, so proteins must be created in the soma and then moved down via vesicles to reach axon or axon terminal
what is the difference between anterograde and retrograde transport?
anterograde is moving vesicles from the cell body to the axon terminal and retrograde is going the opposite direction. this si down on microtubules with the help of motor proteins (kinesin and dynein)
define the main parts of the synapse junction
synapse: where the axon temrinal meets the target cell
presynaptic cell: delivers the signal
postsynaptic cell: receives the signal
synaptic cleft: narrow space between the cells
define neurotrophic factor
chemicals secreted by Schwann cells that keep damaged neurons alive, this is what the survival of neuronal pathways depends on, and is secrete by neruons and glial cells
define glial cells
- non-excitable support cells of the CNS
- do not carry electrical signals over long distances
- only communicate with nearby cells
what are the types of cells that glial cells create?
PNS
- Schwann cell are to support and insulate axons by creating myelin, forms of membrane around the axon
- Satellite cells are nonmyelinating Schwann cells, support cell bodies (nutrients)
CNS
- oligodendrocytes are the same thing as Schwann cells but can myelinate multiple cells at once
- AStrocytes are highly branched glial cells, some work with the synapse, some do metabolic substrates for ATP procedures and they help to maintain homeostasis in CNS, and create a blood-brain barrier to regulate the movement of material between blood and extracellular fluid
- microglia are specialised immune cells that help to remove damaged cells and foreign invaders (phagocytosis)
- ependymal are cells that create a selectively permeable epithelial layer to separate fluid compartments, produce cerebral spinal fluid
define node of Ranvier
unmyelinated regions on myelinated axons, this si where the axon memrbane remains in contact with extracellular fluid to move the transmission of the signal along the axon.
what are the 4 kinds of selective ion channels in the neuron?
Na+, K+, Ca2+ and Cl-
what are th 3 kinds of channels on the neuron
- mechanically gated: found in sensory neruons and open in response to physical forces such as pressure
- chemically gated: responding to a ligand
- voltage-gated: responds to changes in cell membrane potential (Na and K)
define the difference between graded and action potentails
graded are varibale-strength signals that travel over short distances and lose strength as they move where action are large depolarizations that travel for long distances without losing strength. Graded can stimulate an action potential.
define trigger zone
the region of the axon where graded potentials are integrated (initial segment) an an action potentials begins if the signal is above threshold
define the all-or-none phenomena
a stimulus is either above the threshold potential or not. once above the threshold, will always create the same size in stimulus
what are the 9 main steps in ana action potential?
- at rest, -70mV
- depolarizing stimulus
- voltage gated Na and K open
- rapid entry of Na depoloarizes cell
- Na channel close and slower K channels open
- K moves fromcell to ECF
- K channel remain open and extra K leave cell, hyperpolarizaing it
- voltage gated K channel close, less K leaves cell
- cell returns to resting potential
what are the 2 kinds of gates of Na+?
activation, that opens to initiate an action potential, and inactivation gate, that closes and stops ion flow
what is the difference between absolute and relative refractory period?
absolute is when no other stimulus can be conducted and relative is when another stimulus can occur ut it has to be way above threshold to make it create another action potential
define saltatory conduction
the apparent leap-frogging of the action potential down myelinated axons. this creates faster conduction down the length of the axon
define ionotropic receptor
neurotransmitter receptor that alters ion channel function (receptor-channels)
define metabotropic receptor
neurotransmitter receptor that act through a second messenger system (GPCR)
define acetycholine
a neurotransmitter sed y neurons of the central and peripheral nervous system, the synthesis of the molecule is a simple reaction that takes place in the axon terminal
what is a majoy neurotransmitter of the PNS autonomic sympathetic division?
norepinephrine, neurons that secrete this are called adrenergic neurons