Exam II Neuroscience

Glycine

An inhibitory neurotransmitter that is more localized than GABA and is used in about 50% of inhibitory synapses.

Synthesis of Glycine

Glycine is synthesized from serine by the enzyme serine hydroxymethyltransferase.

Inactivation of Glycine

Glycine is inactivated by reuptake into the presynaptic membrane via glycine transporters.

Glycine Receptors

Glycine acts on ligand-gated Cl- channels.

Biogenic Amines

Regulate brain functions and are active in the peripheral nervous system (PNS).

Catecholamine Synthesis

All catecholamines derive from tyrosine.

Tyrosine to DOPA conversion

Tyrosine is converted to DOPA by the addition of a hydroxyl group via tyrosine hydroxylase.

DOPA to Dopamine conversion

DOPA is decarboxylated to Dopamine by DOPA decarboxylase.

Dopamine Synthesis

Dopamine is further converted to Norepinephrine by adding a hydroxyl group using dopamine hydroxylase.

Epinephrine Synthesis

Norepinephrine is converted to Epinephrine by Phenylethanolamine N-methyltransferase.

Dopamine Functions

Dopamine is involved in coordination of movement, motivation, reward pathways, motor control, cognition, and impulse control.

Dopamine Inactivation

Dopamine is inactivated through uptake by glial cells or presynaptic neurons via dopamine transporter (DAT) and enzymatic degradation (MAO and COMT).

Dopamine Receptor Action

Dopamine receptors are metabotropic, and their location and subtype determine their action.

Adenylyl Cyclase

An enzyme that converts ATP to cAMP when stimulated by G-proteins.

Norepinephrine Roles

Norepinephrine is responsible for attention, wakefulness, and feeding behavior.

Norepinephrine Synthesis Location

Norepinephrine is made in the Locus Coeruleus.

Norepinephrine Inactivation

Inactivation occurs through reuptake by norepinephrine transporter (NET) and enzymatic degradation (MAO and COMT).

Adrenergic Receptors

Norepinephrine acts at metabotropic alpha and beta adrenergic receptors.

Alpha1 Receptors

Alpha1 receptors slow depolarization by inhibiting K+ channels.

Alpha2 Receptors

Alpha2 receptors slow hyperpolarization by activating K+ channels.

Epinephrine Characteristics

Found in lower levels than other catecholamines, it binds to alpha and beta adrenergic receptors.

Histamine Function

Histamine promotes wakefulness and attention, controlling vestibular system reactivity.

Histamine Synthesis

Histamine is synthesized from histidine by histidine decarboxylase.

Serotonin

Also known as 5-hydroxytryptamine (5-HT), it is derived from tryptophan and regulates sleep and wakefulness.

Serotonin Receptors

Most serotonin receptors are metabotropic with one exception: the ionotropic 5-HT3.

ATP as a Neurotransmitter

ATP is an excitatory neurotransmitter involved in motor neuron function in the spinal cord.

Peptide Neurotransmitters

Peptide neurotransmitters bind to metabotropic receptors and include substances like substance P and endorphins.

Peptide Categories

Five categories based on amino acid sequence include: brain-gut peptides, opioid peptides, pituitary peptides, hypothalamic-releasing peptides, and miscellaneous peptides.

Pre-propeptides

Inactive forms of final neurotransmitters, synthesized in the endoplasmic reticulum.

Pro-peptides

Processed polypeptides that can be modified to produce multiple active peptides.

Sensory System Afferent Fibers

Afferent fibers reside in ganglia alongside the spinal cord and brainstem.

Afferent vs Efferent

Afferent signals travel from the PNS to the CNS, while efferent signals leave the CNS.

Dorsal Root Ganglia

Ganglia that supply sensory information from the body to the CNS.

Pseudounipolar Neurons

Sensory afferent neurons with a single projection that splits into two branches.

Sensory Transduction

The process of converting external stimuli into electrical signals for the nervous system.

Mechanoreceptors

Sensory receptors responsible for detecting touch and pressure.

Merkel Cells

Slow-adapting mechanoreceptors found in the epidermis, detecting fine touch and pressure.

Meissner's Corpuscles

Rapidly adapting mechanoreceptors that detect low-frequency vibrations.

Pacinian Corpuscles

Rapidly adapting mechanoreceptors that detect high-frequency vibrations.

Ruffini Afferents

Slow-adapting receptors in ligaments that detect skin stretch.

Free Nerve Endings

Afferent fibers without specialized receptors, important in pain sensation.

Group 1a Afferents

Sensory receptors supplying muscle spindle information; the largest and fastest.

Alpha Motor Neurons

Efferent neurons that innervate extrafusal muscle fibers for contraction.

Muscle Stretch Reflex

A reflex circuit that controls muscle tension through a direct pathway.

Muscle Spindles

Sensory receptors embedded in muscles that detect stretch.

Intrafusal Fibers

Fibers within the muscle spindle that run parallel to extrafusal fibers.

Group 1a Neurons

Primary sensory afferents that coil around all intrafusal fibers and inform on length and velocity of stretch.

Group II Neurons

Secondary sensory afferents that innervate nuclear chain fibers and provide information about muscle length.

Reciprocal Innervation

The simultaneous contraction of a stretched muscle and relaxation of its antagonist.

Gamma Motor Neurons

Efferent fibers that control intrafusal fibers to keep them taut.

Co-activation of Motor Neurons

Simultaneous activation of gamma and alpha motor neurons to maintain spindle sensitivity.