Cellular & Neuro Physiology- Exam 2

The ____ nervous system is the involuntary branch of the peripheral efferent division.

autonomic

(Ex: cardiac, digestive, & vascular systems)

The ____ nervous system is the efferent branch subject to voluntary control.

somatic

(Ex: skeletal muscle)

What is the primary purpose of efferent output on the body?

maintain homeostasis

Which 2 neurotransmitters directly mediate almost all neurally controlled effector organ responses?

AcH and norepinephrine

The ____ fiber is where neurotransmitters are released.

preganglionic

T/F: Postganglionic receptor terminal branches only release neurotransmitters to have an effect on one cell.

false -- innervates a large area, not just a single cell

Parasympathetic preganglionic fibers are ____, and postganglionic fibers are ____.

long (pre)

short (post)

Sympathetic preganglionic fibers are ____, and postganglionic fibers are ____.

short (pre)

long (post)

Sympathetic preganglionic cells are primarily found in which regions?

thoracic & lumbar areas

Parasympathetic preganglionic cells are primarily found in which regions?

cranial & sacral areas

Which postganglionic fibers contain nicotinic receptors?

both parasympathetic & sympathetic

Which postganglionic fibers contain muscarinic receptors?

only parasympathetic

T/F: Sympathetic & parasympathetic preganglionic fibers release the same neurotransmitter.

true -- both release AcH

Sympathetic postganglionic fibers release ____.

norepinephrine

What neurotransmitter do parasympathetic postganglionic fibers release?

AcH

Would a drug that interferes with AcH action at the nicotinic receptors block the influence of:

A) parasympathetic nervous system
B) sympathetic nervous system
C) both

both

Where are nicotinic receptors found?

parasympathetic & sympathetic postganglionic fibers

Where are muscarinic receptors found?

effector cell membranes

___ is referred to as innervation of a single organ by both branches of the autonomic nervous system.

dual innervation

T/F: Visceral organs are innervated by both sympathetic & parasympathetic nerve fibers.

true -- usually both systems are partially active, and in certain circumstances, one becomes dominant over the other

Digestive & urinary activity is inhibited by which nervous system?

sympathetic

What is the advantage of dual autonomic innervation?

enables precise control over an organ's activity

Where are norepinephrine & epinephrine released from?

adrenal medulla

Stress hormones reinforce activity of the ____ nervous system.

sympathetic

The release of which hormone causes your blood vessels to narrow?

norepinephrine

Name the 2 types of cholinergic receptors and where they're found:

1) Muscarinic - effector cell membranes
2) Nicotinic - postganglionic cell bodies

Name the adrenergic receptors:

alpha 1, Beta 1, Beta 2

Which hormones can bind to alpha and beta receptors?

norepinephrine & epinephrine

____ receptors are found in the vascular system and cause vasoconstriction when activated.

a1

____ receptors are found only in the heart and increase cardiac output by increasing SV and contractions of the heart when activated.

B1

____ receptors are found on smooth muscles of arterioles & bronchioles and cause vasodilation when activated.

B2

Which receptor will help to open up airways?

B2

Which hormone excites both alpha and beta receptors equally?

epinephrine

____ hormone excites mainly the alpha receptors.

norepinephrine

The response to ____ adrenergic receptor activation is generally inhibitory.

B2

What would happen if alpha receptors were blocked?

A) vasoconstriction
B) vasodilation

vasodilation

A ____ binds with the autonomic receptor, preventing the neurotransmitter from binding and causing a response.

antagonist

Atropine blocks the effect of ACh at ____ receptors, but NOT ____ receptors.

muscarinic (blocks)

nicotinic (does not affect)

** blocks parasympathetic effects

If someone is hypertensive, which receptor would you want to block?

B1 receptors (you'll want to decrease the amount of blood the heart pumps to blood vessels)

What is the target tissue of the somatic motor division?

skeletal muscle

What is the synapse of the somatic motor neuron on a muscle fiber called?

NMJ

Which region of the neuromuscular junction is ACh released from?

presynaptic axon terminal

What kind of receptors line the motor end plate of the NMJ?

nicotinic ACh receptors

____ breaks down AcH by degrading it into acetyl and chlorine.

AChE

How does an action potential travel down the muscle fiber?

ACh binding to nicotinic receptors on motor end plate causes non-specific cation channels to open --> Na+ enters, causing more Na+ channels to open down the motor end plate

____ has to enter the neuromuscular junction in order for the muscle to relax and break down ACh.

AChE

Explain what happens at the neuromuscular junction:

1) AP sent down motor neuron
2) AP activates voltage-gated Ca++ channels
3) Ca++ rushes into presynaptic terminal, triggering release of vesicles
4) Vesicles bind to membrane, release ACh
5) ACh binds to nicotinic receptors on motor end plate
6) Na+ enters, causing channels to open and spread AP down motor neuron

Signals are passed between nerve terminal and muscle fiber by what transmitter?

ACh

How does AChE turn off a muscle cell's electrical response?

inactivates ACh

The presence of which toxin would block the release of ACh?

botulinum toxin

(prevents muscles from responding to nerve impulses --> person can't depolarize)

In which disorder does the body produce antibodies against it's own motor end plate ACh receptors?

myasthenia gravis

(ACh and antibodies compete for same receptor --> extreme muscular weakness)

What happens to ACh released when antibodies are produced against their own motor end plate ACh receptors?

the ACh that's released gets broken down by AChE

What group of chemicals inhibit AChE?

organophosphates

What happens when ACh can NOT get broken down?

constant muscle contraction --> person can't repolarize (muscle never relaxes)

T/F: Skeletal muscle cells are multinucleated.

true

Which part of a skeletal muscle fiber contains calcium?

sarcoplasmic reticulum

The ____ of muscle fibers is where the action potential runs down.

T-tubules

___ acts as a barrier between actin and myosin, only moving when calcium binds to troponin.

tropomyosin

In order for actin and myosin to bind, ____ has to bind to troponin.

calcium

Does cross-bridging occur during a relaxed or contracted muscular state?

contracted

The ___ band in a sarcomere contains only thin filaments, and the ____ zone contains only thick filaments.

I band (thin)

H zone (thick)

The ____ band in a sarcomere contains both thick & thin filaments and remains constant during contraction.

A band

Which 2 regions of a sarcomere almost disappear during muscle contraction?

I band and H zone

___ is needed to bind to myosin to detach myosin from actin.

ATP

What causes the myosin head to change shape?

breakdown of ATP into ADP and inorganic phosphate

If no ATP is available during the cross bridge cycle, what happens?

actin & myosin remain attached and stay contracted = rigor state

T/F: You have to have both ATP and calcium to keep a muscle from entering a rigor state.

true

ACh opens ligand gated channels during muscular contraction that cause ____ to enter the cell, causing local depolarization.

Na+

What kind of potentials are receptor potentials?

graded potentials -- local, travel short distances

____ receptors detect chemical or physical damage occurring in the tissues.

nociceptors

____ is a change in sensory receptor membrane potential.

receptor potential

A receptor potential must be converted into a ____ for long distance transmission.

action potential

What's the primary difference between conversion of receptor potential to AP of a specialized afferent ending and a separate receptor cell?

separate receptor cells release Ca++, causing a release of neurotransmitters

Does a smaller receptive field or larger receptive field have a higher sensitivity?

smaller receptive field = more sensitive area

Small receptive fields have low ____, making the area much mores sensitive.

convergence (less primary sensory neurons on the one stimulated secondary neuron)

Where is sensory information that initiates visceral reflexes integrated?

brain stem or spinal cord

T/F: Visceral reflexes usually do not enter conscious perception.

true

(Ex: change in BP -- body won't recognize the change unless extreme, the body will just take care of it)

____ is referred to as the level of stimulus intensity necessary for you to be aware of a particular sensation.

perceptual threshold

What 4 factors must the CNS use to distinguish properties of a stimulus?

1) nature (what type)
2) location
3) intensity
4) duration

What are the 2 ways the brain can determine the location of a stimulus?

1) activated receptor fields
2) lateral inhibition

____ enhances the contrast between the center and sides of receptive fields, making the sensation more easily located.

lateral inhibition

During lateral inhibition, the pathway ____ to the stimulus inhibits the neighboring pathways, essentially enhancing the perception of the stimulus.

closest to stimulus

In order to depress the responsiveness of pathways in lateral inhibition, what kind of ion channels might open to do so?

K+ or Cl-

(both would cause a hyperpolarization of the cell)

____ coding used to determine the intensity of a stimulus refers to the number of receptors activated.

population

____ coding refers to the frequency of action potentials coming from receptors.

frequency

A ____ stimulus generates a longer series of action potentials.

longer

Tonic receptors adapt ____.

slowly or not at all

Phasic receptors adapt ____.

rapidly -- once it realizes the stimulus isn't causing any harm, it stops adapting

Which kind of receptor is responsible for keeping information going to the brain?

tonic receptors

Nociceptors are considered what kind of receptor?

tonic -- you don't want these to adapt to painful stimuli, but need to still generate AP to relay info to CNS