Animal Physiology Exam 2: Nervous System, Sensory Physiology, and Muscle Phys

presynaptic inhibition

Action of an axoaxonic synapse at a synaptic terminal that decreases the neurotransmitter released by presynaptic membrane

Information coming into the central nervous system is transmitted along ________ neurons.

Afferent and Sensory

Glial cells only help maintain homeostasis of the brain's extracellular fluid. provide structural and metabolic support and help maintain homeostasis of the brain's extracellular fluid. only guide neurons during growth and repair. only provide structural and metabolic support. All of the answers are correct.

All of the answers are correct

visceral stimuli

Blood pressure, distension of gastrointestinal tract, blood glucose concentration, internal body temperature, osmolarity of body fluids, lung inflation, pH of cerebrospinal fluid, pH and oxygen content of blood

A nerve cell's resting membrane potential is -70mV. The equilibrium potential for sodium (Na) is +30mV. A neurotransmitter opens ion channels in the dendrites and increases permeability to Na. The result will be

Depolarization

A nerve cellʼs membrane potential is hyperpolarized to -90 mV. The K+ Nernst (equilibrium) potential is -86 mV. A neurotransmitter released onto the postsynaptic terminal of this cell opens a K+ conductance. The result will be:

Depolarization: when the membrane becomes more permeable to an ion, the RMP will move toward the equilibrium potential for that ion.

A secondary sensory neuron (X) receives input from three primary sensory neurons (A, B and C). Stimulation of A, B, or C individually do not cause an action potential in X. Stimulation of A and B together cause an action potential in X. Stimulation of A, B, and C together does not cause an action potential in X. A. Sensory neuron A only causes a graded depolarization of X. B. This is an example of spatial summation. C. Sensory neuron C could cause inhibition D. A, B and C.

Sensory neuron A only causes a graded depolarization of X. This is an example of spatial summation. Sensory neuron C could cause inhibition

Mechanoreceptors

Sensory receptors responsible for sensing distortion in body tissues.

temporal summation

Summation by a postsynaptic cell of input (EPSPs or IPSPs) from a single source over time.

Neuron Doctrine

The idea that individual cells called neurons transmit signals in the nervous system, and that these cells are not continuous with other cells as proposed by nerve net theory.

What characterizes depolarization, the first phase of the action potential?

The membrane potential changes from a negative value to a positive value.

What event triggers the generation of an action potential?

The membrane potential must depolarize from the resting voltage of -70 mV to a threshold value of -55 mV.

axon transport

The transportation of materials from the neuronal cell body to distant regions in the dendrites and axons (forward), and from the axon terminals back to the cell body (backward).

How does the action potential propagate to myofibrils?

Transverse tubules depolarize leading to a release of calcium ions from SR

Relaxed muscle filaments

Tropomyosin partially blocks actin binding site while myosin heads weakly bind to actin

Schwann cells

Type of glia in the PNS, Supporting cells of the peripheral nervous system responsible for the formation of myelin.

Acetylcholine breaks down to form

acetic acid and choline

Each myosin head has a binding site for

actin and ATP

inhibitory postsynaptic potential (IPSP)

an inhibitory hyperpolarization of the postsynaptic membrane of a synapse caused by the liberation of a neurotransmitter by the terminal button

Phasic receptors

are quick to adapt to a constant stimulus

Thick filaments are composed of

myosin

Santiago Ramon y Cajal

neuron doctrine

glial cells

cells in the nervous system that support, nourish, and protect neurons. membrane potentials ca -70mV

Special senses receptors

cells that release neurotransmitter onto sensory neurons, initiating an action potential

receptor potential

change in membrane potential

The binding of acetylcholine to its receptor at the neuromuscular junction causes the opening of a

channel for both Na+ and K+

Chemoreceptors

chemical sensors in the brain and blood vessels that identify changing levels of oxygen, carbon dioxide, pH, and organic molecules

Intensity of stimulus

coded by number of receptors activated and frequency of action potentials

What is the neuromuscular junction?

connection between the motor neuron and the muscle fiber it controls

Simple receptors

neurons with free nerve endings

In sensory processing, lateral inhibition:

enhances the perception of a stimulus

Anterograde and retrograde axonal transport are forms of _____________ transport

fast

The force generated by a single muscle fiber that can be increased by increasing

frequency of action potentials only

When light only shines on the center of an on-center visual field, the ganglion response is

fully excited

The blood brain barrier is formed by

glial cells

The highest frequency sound is detected by

hair cells located near the oval window end of the basilar membrane.

Actions potentials are

not degraded over distance all-or-none

Internerons are found

in the CNS

A decrease in the release of neurotransmitter from the photoreceptor would indicate a(n)

increase in light intensity

A motor unit consists of

one neuron and all the skeletal muscle fibers it controls.

lateral inhibition

increases contrast between activated receptive fields and inactive neighbors

Polarization

information flows in one direction

Where do most action potentials originate?

initial segment

When a rod located in the retina is stimulated by light,

intracellular concentration of cGMP decreases

Multiple Sclerosis (MS)

is an autoimmune disease in which myelin is attacked

hair cells in ear

long tufts of stereocilia on top surface, once basilar membrane vibrates, stereocilia swap back and forth within endolymph - causes opening of ion channels

Sacrolemma

plasma membrane of a muscle fiber

Which ion(s) is/are higher in concentration inside the cell compared to outside?

potassium

Phineas Gage

railroad worker who survived a severe brain injury that dramatically changed his personality and behavior; case played a role in the development of the understanding of the localization of brain function; frontal lobe

The function of transverse tubules is to

rapidly move action potentials to the interior of the muscle fiber

What happens to calcium released by SR

re-uptake by SR by Ca2+ ATPase pumps, Calsequestrin binds to calcium ions against their concentration gradient

For antagonistic muscle groups to move a limb, flexor contraction occurs coincident with

relaxation of the extensor

As ATP binds to the myosin head at the beginning of a muscle contraction cycle, the myosin head immediately

releases actin

A sacromere is best described as

repeated functional units of filaments

Photoreceptors

respond to light

Slow voltage-gated K+ channels

responds slowly to depolarizing membrane potential

Graded (local) potentials

restricted to one place in the neuron, can be summed, involves Na+, Cl-, and Ca2+

The hydrolysis of ATP causes myosin to immediately

rotate into a position (cocked) to bind to actin.

somatic senses

senses of touch, temperature, pain, itch, and proprioception

two point discrimination

the ability to recognize or differentiate two blunt points when they are simultaneously applied to the skin

How would blocking retrograde transport in an axon affect the activity of a neuron?

the cell body would not be able to respond to changes in the distal end of the axon

A blind spot in the retina occurs where

the optic nerve leaves the eye

What does the Goldman-Hodgkin-Katz equation take into account that the Nernst equation does NOT?

the permeabilities of the ions

adequate stimulus

the type of stimulus for which a given sensory organ is particularly adapted

If the concentration of Na+ ions is 110mM outside a cell and 35 mM inside, the Nernst (equilibrium) potential for Na+ will be:

+30 mV

Membrane potential is influenced by

-Concentration gradient of ions -Membrane permeability to those ions -Valence (z)

Membrane potential for multiple ions

-Potassium is much greater than sodium's potential -Sodium-potassium pump stabilizes the resting membrane potential and lowers by 5-8 mV

Sensory Pathways

-Receptors act as transducers -Intracellular signals usually include change in membrane potential -stimulus > thresold: action potential to CNS -Integration in CNS -> cerebral cortex or acted on subconsciously

Contraction

1) Calcium ions levels increase in cytosol 2) Ca2+ binds to troponin 3) Ca2+ activates and allows troponin to move tropomyosin away from actin-myosin site 4) myosin strongly binds and completes power stroke and moving actin filaments

Put these events in the correct chronological sequence: 1. End-plate potentials trigger action potentials. 2. Transverse tubules bring potentials into the interior of the cell. 3. Acetylcholine binds to receptors on the motor end plate. 4. Ca2+ is released from the sarcoplasmic reticulum.

3, 1, 2, 4

What is the main distinction between fascicles and motor units?

A motor unit is a group of muscle fibers controlled by the same neuron

sarcoplasmic reticulum (SR)

A specialized endoplasmic reticulum that regulates the calcium concentration in the cytosol of muscle cells.

Which statement about motor units and their activation is FALSE? At its peak intensity, a contractile stimulus will activate muscle fibers that are easily fatigued. All muscle fibers in a single motor unit are of the same fiber type. The metabolic capacity of muscle fibers within a motor unit can be altered. A weak contractile stimulus activates fast-twitch motor units. A motor unit in muscles of gross movement can have thousands of muscle cells.

A weak contractile stimulus activates fast-twitch units

duration of stimulus

Coded by duration of action potentials Some receptors can adapt, or cease to respond

Sir Alan Hodgkin, Sir Andrew Huxley, and Sir John C Eccles

Graded local potential and the basis of action potential; Nobel prize 1963

voltage-gated sodium ion channels

Have 2 gates: activation and inactivation; at rest activation gate closes channel. Depolarizing stimulus arrives at the channel and activates gate open; approximate EP for sodium is +30 mV

A nerve cell's membrane potential is held at -70mV. The K+ Nernst (equilibrium) potential is -86 mV. A neurotransmitter released onto the postsynaptic terminal of this cell opens a K+ conductance. The result will be:

Hyperpolarization

Spatial summation

Integration by a postsynaptic neuron of inputs (EPSPs and IPSPs) from multiple sources.

The major determinant of the resting potential of all cells is

K+ gradient between the blood and interstitial fluid

speed of action potential

Large axons (diameter) are faster, resistance of axon membrane to ion leakage out of the cell (myelinated axons are faster)

In general, the nervous system is made up of which two types of cells?

Neurons and Glia

What characterizes repolarization, the second phase of the action potential?

Once the membrane depolarizes to a peak value of +30 mV, it repolarizes to its negative resting value of -70 mV.

____________ received the Nobel Prize in _____________ for proposing the Neuron Doctrine for how neurons work

Ramon y Cajal, 1906

Fast voltage-gated Na+ channels

Responds rapidly to depolarizing membrane potential

Myelin is formed by

Schwann cells and oligodendrocytes

What is the first change to occur in response to a threshold stimulus?

Voltage-gated Na+ channels change shape, and their activation gates open.

cochlea

a coiled, bony, fluid-filled tube in the inner ear through which sound waves trigger nerve impulses

A receptor potential is

a graded potential

A receptor potential is:

a graded potential

Refractory period

a period of inactivity after a neuron has fired; loss K+ repolarizes membrane

Choline is taken up from extracellular fluid by

a specific transporter that requires the co-transport of Na+ to power the movement of choline

Which is the most common location where action potentials start in efferent neurons?

axon hillock

neurtransmitters are released from

axon terminals

The structure that separates the cochlear duct from the tympanic duct is the

basilar membrane

Vesicles and organelles are moved by cytoskeletal system by

dynein, kinesin, and ATP

Sarcoplasm

cytoplasm of a muscle fiber

If the sodium pump in the membranes of the photoreceptors were completely blocked, the result would be

darkness (blindness)

The multiple thin, branched structures on some neurons whose main function is to receive incoming signals are the

dendrites

Excitatory Post-Synaptic Potential (EPSP)

depolarization of the postsynaptic membrane potential by the action of a synaptically released neurotransmitter

A nerve cell's resting membrane potential is -70mV. The equilibrium potential for sodium is +55 mV. A neurotransmitter opens ion channels in the dendrites and increases permeability to Na. The result will be

depolarization; when the membrane becomes more permeable to an ion, the RMP will move toward the equilibrium potential for the ion

The action potential traveling along the t-tubule changes he conformation of the

dihydropyridine (DHP) receptor (L-type calcium channel)

Camillo Golgi

discovered golgi apparatus leading to Nobel Prize 1906

threshold

minimum stimulus that causes a change in signal transduction

Concentration gradients exist across the plasma membrane. Specifically, there are ___________

more potassium ions inside and more sodium ions outside the plasma membrane

The origin is the end of the skeletal muscle that attaches to the

more stationary bone

Population coding

multiple receptors functioning together

Match the structures with the accurate description. A. muscle fiber B. fascicle C. sarcolemma D. myofibril E. t-tubules a single muscle cell

muscle fiber

somatic stimuli

muscle length and tension, proprioception

Tonic receptors

slowly decrease the frequency of action potentials generated to a constant stimulus.

mechanoreceptors

stretch

The region where the axon terminal meets its target cell is called the

synapse

A flexor is a skeletal muscle whose shortening moves attached bones

towards one another

The hair cell of the cochlea is depolarized when the stereocilia are bent

towards the smallest stereocilia

postsynaptic neuron

transmits impulses away from the synapse

Sound waves are converted into vibrations by the

tympanic membrane

The resting membrane potential results from

uneven distribution of ions across the cell membrane and differences in membrane permeability to ions

Thermoreceptors

varying degrees of heat

Special Senses

vision, hearing, taste, smell, equilibrium

What opens first in response to a threshold stimulus?

voltage-gated Na+ channels

Diffused light illuminates both center and surround of on-center cell creates a _________ ganglion cell response

weak response

Trigger Zone

where action potential is generated -positive charge spreads along adjacent sections of axon by local current flow