study guide 3 improved Flashcards
What do synaptic vesicles do?
They release neurotransmitters at chemical synapses.
How can synaptic vesicles release neurotransmitters
Through a process called exocytosis which is triggered by calcium ions
What is a central synapse?
A connection between neurons in the central nervous system.
is a central synapse the same as the NMJ?
Central synapses and the NMJ are not the same. Both are synapses but a central synapse is in the brain while the NMJ is where a motor neuron meets a muscle fiber.
What is a bouton?
Boutons (buttons)= numerous presynaptic terminals.
What molecules can be neurotransmitters?
Small molecules
- Acetycholine
- Adenosine triphosphate (ATP)
- Nitric oxide (NO)
Amines
Amino Acids
What is an ionotropic receptor?
An ionotropic receptor is a ligand-gated, chemically gated, neurotransmitter-gated receptor with a built in ion channel
What is a metabotropic receptor?
Membrane receptor that modulates cell activity by initiating metabolic steps. dont have a built in ion channel
EPSP and IPSP
Inhibitory postsynaptic potential (IPSP)
Excitatory postsynaptic potential (EPSP)
Excitatory cholinergic synapse
-AP depolarizes axon terminal, opens VGCC, Ca2+ enters and triggers release of ACh
-ACh diffuses across cleft, binds to postsynaptic receptors
- ACh receptor are ionotropic ligand gated ion channels that open and allow Na+ and K+ across the membrane
Inhibitory GABA-ergic synapse
- Uses y-aminobutyric acid (GABA) as neurotransmitter
- GABA receptors are chloride channels
-Cl- current hyperpolarizes the postsynaptic membrane - Postsynaptic neuron inhibited, less likely to fire action potential
- chloride goes in
- Are neurotransmitters inhibitory or excitatory? What determines if a neurotransmitter will
lead to inhibition or excitation. Are they always one or the other?
can be either, depends on the synapse, can be inhibitory at one and excitatory at another
How do you end a signal sent from a presynaptic cell to a postsynaptic cell? What
happens to released neurotransmitters?
Presynaptic cell stops releasing neurotransmitter
The neurotransmitter already in the synapse is cleared
- diffusion: diffuses out/away from the cleft
-degradation: degraded by enzymes present w/in synaptic cleft (like AChE for ACh)
- reputake via specialized transporter protiens into presynaptic terminals
- uptake (via special transport protiens) into surround glial cells
What are the modes of synaptic transmission?
Vesicular secretion
- Movement from the presynaptic to the postsynaptic cell
Retrograde
- Release of a lipid-soluble molecule from the postsynaptic cell.
Non-vesicular
- Release of water-soluble molecules through a transmembrane channel within the plasma membrane.
Vesicular secretion
vesicles release cargo, the release is ca2+ triggered exocytosis. This is the first to be discovered and is the “classic” mode of vesicular secretion.
The movement is “orthograde,” which means the movement from presynaptic to postsynaptic cell.
Retrograde
Release of a lipid-soluble molecule from the postsynaptic cell. Nitric Oxide (NO) released
Non vesicular
a vesicle is not needed. Release of a water-soluble molecule through a transmembrane channel within the plasma membrane. Thought to be CALHM1 in type II taste receptor cells within taste buds.
What did Santiago Ramon y Cajal do? and what is the black reaction
Santiago Ramon y Cajal discovered the synaptic cleft. Used a tissue staining method known as the Black Reaction.
who created the black reaction?
The black reaction was created by Camillo golgi
cells bodies in the cns vs pns
CNS: nucleus
PNS: Ganglion
What is the central nervous system composed of? How is the peripheral nervous system different?
CNS: brain & spinal cord
PNS: sensory & motor
neurons in the nervous system
around 1 trillion
neuroglia cells
cells that support neurons in the nervous system
How many neuroglia cells in the nervous sytem
About 10 trillion in the nervous system
Four types of neuroglia cells in the CNS
Oligodendrocytes, ependymal cells, microglia, and astrocytes.
ollie puts an epipen in his leg and he mutates so astroctyes come from his hands
Two types of neuroglia cells in the PNS
Schwann cells and satellite cells
Universal properties of neurons
Excitability (irritability)
Respond to environmental changes (stimuli)
Conductivity: Produce electrical signals that travel along nerve fibers (axons) to reach other cells at distant locations.
Secretion: Nerve fiber endings (axon terminals) release chemical neurotransmitters that influence other cells
dendrites
multiple branches that come off the soma, primary site for receiving signals from other neurons.
soma (cell body)
has a centrally located nucleus with large nucleolus. Contains mitochondria, lysosomes, Golgi complex, rough ER, inclusions, and cytoskeleton like other cells. No centrioles.
axon (nerve fiber)
specialized for rapid conduction of electrical signals, only one axon per neuron, Originates at the axon hillock.
axon terminals
swellings that form contact points (synapses) with other cells. Contain synaptic vesicles full of neurotransmitters.
myelin sheath
insulating layer surrounding some axons. Formed by glial cells.
Multipolar neurons
One axon and multiple dendrites (most neurons in the CNS)
Bipolar neuron
One axon and one dendrite (olfactory cells, retina, inner ear, taste buds)
PNS
Unipolar neuron
a single process leading away from soma that splits into axon and dendrite (sensory cells from skin and organs to the spinal cord)
PNS
Where do you find bipolar neurons
You’d find bipolar neurons in olfactory cells, retina, inner ear, or taste buds.
PNS
Where do you find anaxonic neurons
many dendrites but no axon (retina, brain, adrenal gland.)
What is gray matter?
Gray matter contains cell bodies, dendrites, and synapses. Darker color due to very little myelin present in the tissue. Forms surface layer (cortex) over cerebrum and cerebellum. Forms nuclei deep within the brain.
White matter
White matter: Bundles of axons. White color from lots of myelin. Called “tracts” in the CNS and “nerves” in the PNS. Deep to cortical gray matter in the brain. Superficial to gray matter in the spinal cord.
What does the nervous system develop from in the embryo (which tissue layer)?
The nervous system develops from the ectoderm (outermost tissue layer of the embryo)
How does the neural tube form
- Dorsal midline of embryo thickens to form neural plate
- Neural plate sinks and its edges thicken.
- Forms neural groove with a raised neural fold on each side.
- Neural folds fuse, creating a hollow neural tube by day 26.
How much blood flow goes to the brain?
Estimated 15% of cardiac output
Why does the brain need so much blood
It requires a constant supply of blood to deliver oxygen and nutrients to its cells and to support its high metabolic demand.
The brain is protected by the skull, membranes, and fluid. What are these membranes?
From outermost to innermost
Dura mater
Arachnoid mater
Pia mater
What is the fluid? What is the benefit to having our brain surrounded by fluid?
Cerebrospinal fluid (CSF). It protects and nourishes the brain & spinal cord.
What is the choroid plexus?
structues in the ventricals made of ependymal cells that make CSF
What does the choroid plexus do
create cerebrospinal fluid.
What is the cerebrum?
The cerebrum is the largest, most conspicuous part of the human brain. It’s the seat of sensory perception, memory, thought, judgment, and voluntary motor actions.
Outer layer of the cerebrum is called? What color is it
The outer layer, the cerebral cortex, is made up of grey matter.
Frontal lobe
- Voluntary motor control of skeletal muscles; personality; high intellectual processes; verbal communication.
Parietal lobe
- Cutaneous and muscular sensations, understanding speech and formulating words to express thoughts and emotions, interpretation of textures and shapes.
Occipital lobe
- Integration of movements in focusing the eye; correlation of visual images with previous visual experiences and other sensory stimuli.
Temporal lobe
- Memory; sensory and visceral integration.
What is the primary motor cortex?
The motor area that controls voluntary skeletal muscles is known as the primary motor cortex.