General Physiology Exam 2

Neurotransmitters

Neurotransmitters

Released form a pre-synaptic cell by the opening of voltage-gated Ca channels on the synaptic nerve terminal

Less are released when an axo-axonic synapse causes the membrane of the synaptic knob to be hyperpolarized before the arrival of an action potential down the axon

Reduced in the Synaptic Cleft in a number of ways:

1. Reuptake by the pre-synaptic nerve terminal

2. Destruction by enzymes in the membrane of post-synaptic neurons

3. Internalization of receptor and this

Ex.

• Glycine

• GABA

• Glutamate

• ACh

• NE

• Dopamine

Agonist

A chem that binds a receptor and activates it signaling system

Glycine

The most common inhibitory neurotransmitter in the spinal cord

Also an amino acid

Antagonist: Strychnine

Antagonist

A drug that binds a receptor and blocks or prevents neurotransmitter binding and activity

Alpha Adrenergic Receptor

A GPCR for NE or Epinephrine that causes smooth muscle contraction or inhibition of gland secretion

NMDA Receptor (Ca Channel)

This channel needs initial depolarization before it can generate its own synaptic potential during long term potentiation at a glutamatergic synapse

GABA (Gamma-aminobutyric Acid)

The most common inhibitory neurotransmitter in the brain

An amino acid

Agonist: Valium

Long Term Memory

The type of memory that results from new connections or dramatic changes to synaptic strength

Lasts weeks to a lifetime

EPSP

A depolarizing graded potential created at a synapse, generated by either opening an Na+ or Ca++ channel

More than 1 are required to reach threshold and fire an action potential

Ex.

• Inward movement of K+ in the cochlea, generating a receptor potential

Temporal Summation

When many EPSPs are generated rapidly at 1 synapse w/in a post-synaptic neuron and arrive at the initiation zone before initial EPSPs have decayed

Caused by multiple action potentials arriving on single synaptic connection to a post-synaptic cell

Isoproterenol

An agonist for epinephrine at Beta Adrenergic receptors used to speed up the heart and can also be administered in inhaled form to relax airways (bronchioles) during an asthma attack

Glutamate

The most common excitatory neurotransmitter in the CNS

An amino acid

A receptor molecule on a taste cell generates the flavor of umami when this is bound to it

Agonist: MSG

Pre Synaptic Density

Caused by the clustering of SNARE and docking proteins in the membrane

Repetition

Translated into a stronger synapse at a glutamatergic synapse w/ long term potentiation as frequent activity at that synapse increases the production of receptor proteins leading to larger EPSPs

IPSP

A hyperpolarizing graded potential created at a synapse generated by the opening of either K+ or Cl- channels

Oxytocin

A neuropeptide

Input Neurons

Many synaptic connections from this neuron are required to cause a post-synaptic neuron to fire an action potential

Acetylcholinesterase

The enzyme that helps degrade ACh in the synaptic cleft

Reuptake Inhibitor

A chem that prevents neurotransmitter reuptake

Acetylcholine (ACh)

The neurotransmitter that:

• Is released by post-ganglionic neurons in the parasympathetic division of the ANS

• Is found in the muscarinic receptor of most target cells where the post-ganglionic axon synapses onto the target organ of the parasympathetic division of the ANS

• Is found in the nicotinic cholinergic receptor in the ganglia of the ANS

• Is found in the nicotinic receptors in the synapse between the motor neuron and the ganglionic neuron in the ANS of both sympathetic and parasympathetic divisions

• Is found at the neuromuscular junction

Degraded by Acetylcholinesterase in the synaptic cleft

Norepinephrine (NE)

The catecholamine neurotransmitter that:

• Is important in regulation of alertness

• Is found in the adrenergic receptor of most target cells of the sympathetic division of the ANS

• Binds to Alpha Adrenergic Receptors to illicit smooth muscle contraction

• Binds to Beta Adrenergic Receptors to illicit smooth muscle relaxation

Degraded by Monoamine Oxidase in the synaptic cleft

Divergence

When 1 neuron has axon collaterals to make synaptic connections on many different neurons

Muscarinic Cholinergic Receptor

A GPCR that activates enzymes and second messenger systems

ACh binds here on most target cells of the parasympathetic system of the ANS

Synapse

The space between neurons that electricity and chemicals pass through to get from neuron to neuron

Strength indicated by the amplitude of the post-synaptic potential in either the depolarizing or hyperpolarizing direction

Neurotransmitter binding to receptor depends on the concentration of neurotransmitter in the Cleft

Post Synaptic Density

Caused by the clustering of receptor proteins and other signaling pathway proteins in the membrane

Dopamine

A catecholamine that is an important neurotransmitter in regulation of motor pathways

Nicotinic Cholinergic Receptor

A receptor that is also a ligand-gated Na+ ion channel found in the synapse between the motor neuron and the ganglionic neuron in the ANS of both sympathetic and parasympathetic divisions

Binds ACh in the ganglia of the ANS

Spatial Summation

When many EPSPs are generated at several different synapses w/in a post-synaptic neuron and reach the initiation zone of the axon at the same time

Caused by action potentials arriving simultaneously at different synapses to a post-synaptic cell

Serotonin

The most common neuromodulator in the CNS and brain

Antagonist: LSD

Pre Synaptic Facilitation

When an axo-axonic synapse causes the membrane of the synaptic knob to be depolarized a little before the arrival of an action potential down the axon

Tyrosine Hydroxylase

The rate limiting step in catecholamine synthesis

Beta Adrenergic Receptor

A GCPR for NE or epinephrine to bind to to cause smooth muscle relaxation, dilation of tubes/blood vessels, and stimulation of gland secretion

Agonists:

• Speed up the heart

• Relax the bronchioles

Synaptic Plasticity

The ability for to make and maintain new synapses as well as the ability to modify synaptic strength

Monoamine Oxidase

The enzyme that helps degrade NE in the synaptic cleft

Convergence

When many axons form synapses on 1 neuron

Memory

Can be changed during or after formation

2 durations:

• Working lasts seconds to hours and results from modest changes to synaptic strength

• Long Term lasts weeks to a lifetime, formed by repetition and sleep and results from dramatic changes to synaptic strength

2 types:

• Implicit is procedural, like riding a bike

• Explicit is declarative, like memorization and actively remembering

Connected to olfaction and emotion in the Limbic System

Autoreceptor

A receptor on the nerve terminal for the neurotransmitter that the synapse releases

Receptor Potential

A graded potential generated by sensory receptor due to opening/closing of gated channel

A graded potential created by sensory stimuli in an afferent sensory neuron

Generated by the inward movement of K+, creating an EPSP, in the cochlea

Hair cells create this when a wave of vibration in the fluid of the scala, which is caused by vibration of the oval window, which causes to basilar membrane to vibrate

Axo Axonic Synapse

A synapse (B) that modifies activity in a nerve terminal (A) to reduce released of neurotransmitter from the nerve terminal (A) onto its post-synaptic cell

Pre Synaptic Inhibition

When an axo-axonic synapse causes the membrane of the synaptic knob to be hyperpolarized before the arrival of an action potential down the axon

Viagra

A drug that increases the ability of the body to produce the neurotransmitter nitric oxide

Dorsal Root Ganglion

Where the soma are located for afferent sensory neurons that receive in put from skin, skeletal muscles, and joints:

• Somatic sensory

Thalamus

The center of the “onion” of the cerebral hemispheres that acts as a “routing system” and connects incoming sensory signals to the part of the cortex that normally processes those signals

Most of the actual info processing of sensory info and initial generation of outgoing motor signals happens here

Part of the Limbic System

Dorsal Horn

Where afferent neurons make synaptic connections

Olfactory

The sense of smell using about 400 different odorant molecules that allows humans to distinguish upwards of 10,000 different odors

Humans can detect 2000-4000 different odors by combining detection of different odorant molecules and different strengths (concentrations) of those odorant molecules

Key element of the Limbic System

The most rapidly adapting sense

Lumbar

Spinal nerves that carry most of the sensory info from the hips and legs

Parasympathetic System

Portion of the ANS that has many fibers that exit the CNS through the T1 to L2 spinal nerves

Functions:

• Focuses to near objects

• Slows heart rate

• Increases digestive activity

• Increases blood flow

• Coordinates visceral responses for relaxation, maintenance, and many aspects of reproduction

Has:

• ACh and Nicotinic Cholinergic Receptors found in the synapses between the motor neuron and the ganglionic neuron of the ANS

• Ganglia located in the wall of the organ where it is innervated called intramural ganglia

Nerves leave the CNS via:

• Vagus Nerve (X)

• Sacral nerves

Swallowing

Involves the cranial nerves:

• Facial (VII)

• Glossopharyngeal (IX)

• Vagus (X)

• Hypoglossal (XII)

Temporal Lobe

Helps to process sensory info along with other parts of the cortex posterior to the Central Sulcus

Has:

• The Primary Auditory Cortex

Eyeball

The following cranial nerves carry motor signals to the muscles on/near here:

• Oculomotor (III)

• Trochlear Nerve (IV)

• Abducens Nerve (VI)

Trigeminal Nerve (V)

The cranial nerve that carries a lot of sensory and motor innervation for the face

Innervates tooth sockets and is a frequent target of dentists

Efferent:

• Innervates skeletal muscles used for chewing

Afferent:

• Transmits info from receptors in skin, skeletal muscles of face, nose, mouth, and teeth sockets

Visceral Sensory Neurons

Neurons that make a synaptic connection onto cell bodies in gray matter between the dorsal horn and the lateral horns of the spinal cord

Frontal Lobe

Contains the Primary Motor Cortex

Also responsible for:

• Personality

• Decision

• Initiative

• Morals

• Conscience

• Executive function

• Motor memory patterns

• Primary motor cortex

Arachnoid Mater

The middle membrane of the brain and spinal cord that has spider web-like connections to the inner membrane

CSF circulates just beneath this membrane, the sub area

Thoracic Nerves

Spinal nerves that carry most of motor info for breathing muscles such as intercostal muscles

Carry the sensory info coming from and motor info going to the trunk

Where Sympathetic nerves leave the CNS

Fourth Ventricle

The ventricle located between the brainstem and the cerebellum

Rostral Gray Matter

The anterior half of the cerebral cortex that stores motor patterns and sends signals to activate motor neurons

Ventral Horn

Where the soma of somatic and autonomic motor neurons are found in the gray matter of the spinal cord

The motor neurons that innervate skeletal muscles have soma located here

Neurons here are responsible for the initiation of contraction of quadriceps in the patellar reflex

Wernicke’s Area

The cortex necessary for comprehension of speech

Limbic System

The system that helps connect emotion, olfaction, and memory formation

Made up of:

• Hippocampus

• Amygdala

• Hypothalamus

• Thalamus

Optic (Cranial Nerve II)

The cranial nerve that carries visual signals from the eye (vision)

Only contains afferent fibers

Cervical Spinal Nerves

Spinal nerves that carry most of the sensory info from the shoulders/arms as well as the back of the head

Epineurium

The membrane that wraps around a nerve

Hypothalamus

The part of the brain that regulates:

• Body temp

• Hunger/satiety

Part of the Limbic System

Central Sulcus

Vertical midline of the brain that separates it into two halves:

• Anterior

• Posterior, which processes sensory info, along with Temporal Lobe

Third Ventricle

The ventricle located on the midline near the base of the Hypothalamus

A fluid-filled space that divides the right and left sides of the thalamus and hypothalamus

Pia Mater

The membrane that is closely attached to the brain and spinal cord

Lips and Mouth

Has the largest area of the primary somatosensory cortex devoted to processing info from that body part and a larger part of primary motor cortex devoted to controlling it

First/Second Ventricles

The large ventricles located in each of the cerebral hemispheres

Sympathetic Nervous System

The division of the ANS that coordinates visceral responses to dangerous or stressful situations

Functions:

• Increases heart rate

Nerves leave the CNS via:

• T1 to L2 spinal nerves

• Thoracic spinal nerves

Cerebellum

The part of the brain that is essential for proper balance when standing

Choroid Plexus

The structure that produces most of the CSF

Rods

The photoreceptors in the periphery of the retina that produces black and white vision used for vision at night (scotopic vision)

Responds well to low intensity light of a broad spectrum of wavelengths

Sour

The taste sensation caused by H+ ions entering gustatory taste receptors via ion channels

Tactician

The sense of touch

Touch felt on the left side of the body is perceived by the cortex on the right side of the brain and vice versa

Sensory Adaptation

Decreased receptor response w/ continued stimulation that enhances ability to detect change and ignore background

Described by when the frequency of action potentials traveling along the afferent fibers is decreased

The reason we are able to ignore constant sounds and adjust to room lighting levels

A rapidly adapting sensory cell responds to the onset of a steady stimulation and to the removal of a steady stimulation by producing a brief burst of action potentials at the onset of stimulation, but stops firing until the stimulation stops, which causes a second brief burst of action potentials

Illustrated by the Afterimage Test

The frequency of action potentials decreases due to continued stimulation of constant intensity affect action potentials in the afferent neuron

Volume

Determines by the amplitude of the sound wave

In tandem w/ Frequency to determine the energy in a sound wave

Vision

The sense of seeing

The left part of the visual field creates signals in primary visual cortex in the right cerebral hemisphere

Notes:

• When you view an object that is in front of you and on your left, light hits the medial side of your left retina and travels to the right occipital lobe

• When you view an object that is in front of you and on your right, light hits the lateral side of your left retina and travels to the left occipital lobe

Ganglion cells have the axons that form optic discs, nerves, and tracts

Receptors: Photoreceptors

Cornea

Where the greatest refraction takes place in the eye

Opiates

Reduce acute pain sensation by acting as agonists to receptors along descending pathways capable of modifying and inhibiting signals from nociceptor input pathways

Acuity (Tactile Accuracy)

Precision of the sensation often related to ability to localize stimulus generated by size of receptive fields and/or lateral inhibition

Increases w/ a high density of small receptive fields

Decreases w/ a low density of large receptive fields

Sensory units define receptive fields

Increased Stimulus Intensity

Increases the frequency of action potentials

Pitch (Tone)

Determined by the frequency of sound waves

In tandem w/ Amplitude to determine the energy of a sound wave

Cones

Photoreceptors in the central portion of the retina that produce color vision and is better in bright light

Produces photopic vision

When you point your nose at an object, the light reflected from that object hits a densely packed area of these

Changes in output signals from different types of these when equally stimulated by the reflected white light create Afterimages

Responds to high intensity light of specific wavelengths

3 types:

• Red

• Green

• Blue

Pupillary Reflex

A brainstem reflex arc to constrict the pupil and reduce the amount of light entering the eye to protect the retina from overstimulation

Kidney

Damage/inflammation caused here would result in referred pain that is felt in the lower abdominal area, lower back, and hips

Afterimage

Caused by the changes in output signals from different types of Cones when equally stimulated by the reflected white light

Association Cortex

An area of cortex near primary sensory cortex that stores memories associated w/ acquired knowledge about that sensory info as well as other info to allow one to associate a particular sensation w/ its various meanings

Parietal Lobe

A lobe of the cerebral cortex where somatosensory info is processed and where the primary somatosensory cortex is located

Helicotrema (Apex) of Cochlea

Low-pitched bass sounds cause vibration of the basilar membrane near here, where it is thick and loose

Round Window

High-pitched sounds cause vibration of the basilar membrane near here, where it is thin and taut

Heart

Referred pain that is felt along the left chest, axilla, or underside of the left arm might be caused by damage/inflammation here

Optic Disc

The “blind spot” of the visual field (only observed when looking at something w/ 1 eye) is created by this

Fovea (Macula)

The central area of the retina w/ the highest density of photoreceptors

When you want to see something clearly and in color, you position your head so that incoming light will fall on this structure

Lateral Horn

Where autonomic motor neurons have their soma located in the spinal cord

Pyramidal Decussation

The area of the brain where many descending motor fibers cross from the right to the left side

Ganglion

A collection of neuronal cell bodies outside the CNS in the PNS

Decussation of Medial Lemniscus

The place in the brainstem where several tracts carrying sensory info cross to the contralateral side of the body

Reticular Activating System

A system that helps maintain alertness, attention, and focus on a task

Brainstem

Part of the brain that contains the neurons that send signals to generate breathing rhythms and patterns and speeds the heart up/slows it down

Contains:

• The Decussation of Medial Lemniscus, where several tracts carrying sensory info cross to the contralateral side of the body