Topic 5: Neurons, Ion channels and Action Potentials, Neuronal Functioning

Ependymal cells

PNS. Produce cerebrospinal fluid.

Microglia

CNS. Ingest and break down pathogens and waste products.

Astrocytes

CNS. Structurally support blood vessels and monitor ion concentration levels in fluid surrounding them.

Satellite cells

PNS. Structurally support blood vessels and monitor ion concentration levels in fluid surrounding them.

Schwann cells

PNS. Form the myelin sheath.

Ogliodendrocytes

CNS. Form the myelin sheath.

How afferent neurons differ from textbook neuronal structure

Afferent neurons lack cell-body protruding dendrites

Neurons vs Nerves

Neurons: single cells that exist in the PNS and CNS

Nerves: cordlike structures consisting of many axons. Exist only in the PNS, while nerve tracts (an analog of nerves) exist in the CNS.

Na+/K+ ATPase pump function

Maintains membrane potential. 3Na+ ions exit the membrane for every 2K+ that enter

Selective permeability in relation to Na+/K+ ATPase pump

Resting membrane is more permeable to K+ than Na+

Nerst equation

Predicts the equilibrium potential across the membrane of a cell for a singly charged positive ion.

Location of ungated channels

Resting neuron

Location of voltage-gated channels

Axon membranes

Location of ligand-gated channels

Synapses

Location of mechanically-gated channels

Sensory receptors

Acetylchloline

Transmits between nerves and muscle, in the brain, and in the heart. Relates to memory, attention, and learning, and binds to muscarinic receptors.

Gamma aminobutyric acid (GABA)

Inhibits neurotransmission and opens Cl- channels on the postsynaptic membrane.

Glycine

Inhibits neurotransmission and increases Cl- influx.

Glutamate

Excitatory and involved with learning and memory.

Norepinephrine and epinephrine

Derived from tyrosine. Hormones and neurotransmitters involved in the pleasure/reward pathway, memory, motor control, attention and mental focus (ADHD drugs). Can be excitatory or inhibitory.

Dopamine

Derived from tyrosine. Neurohormone/transmitter involved in behavior, cognition, voluntary movement, motivation and reward, prolactin production inhibition, sleep, mood, attention, and learning.

Serotonin

Derived from tryptophan. Regulates intestinal movements, involved in mood, appetite, and sleep.

Endorphins

Neuropeptide (indirect neurotransmitter). Released during pleasurable experience, reduces pain perception, work in the PNS.

Enkephalins

Neuropeptide (indirect neurotransmitter). A subset of endorphins. Modulates pain response, works in the CNS.

Substance P

Neuropeptide (indirect neurotransmitter). Released by the spinal cord to increase pain perception.

Dissolved CO

Regulates the release of hormones from the hypothalamus.

Dissolved NO

Learning, muscle movement (relaxes smooth muscle in the walls of blood vessels, causing dilation).