Exam 1

Rate of impulse propagation depends on:

-axon diameter- larger diameter, faster it conducts impulses -degree of myelination --unmyelinated axons are slowest --myelinated axons conduct impulses 30 times faster (saltatory conduction)

Neurophysiology: Membrane Channels: Ion channels in the Plasma Membrane

1. Leakage channels randomly open and close

Five Main Membrane Processes in Neural Activities

1. resting potential 2. graded potential 3. action potential 4. synaptic activity 5. information processing

Neurophysiology: Membrane Channels: Ion channels in the Plasma Membrane

2. A chemical stimulus opens a ligand-gated channel

Neurophysiology: Membrane Channels: Ion channels in the Plasma Membrane

3. Mechanical stimulus opens a mechanically gated channels (requires movement, physical stimuli, primarily on dendrites)

Neurophysiology: Membrane Channels: Ion channels in the Plasma Membrane

4. A change in membrane potential opens voltage-gated channels

Hyperpolization

A change in a cell's membrane potential such that the inside of the membrane becomes more negative relative to the outside. It reduces the chance that a neuron will transmit a nerve impulse.

multipolar neuron

A neuron with a single axon and multiple dendrites; the most common type of neuron in the nervous system.

unipolar neuron

A neuron with one axon attached to its soma; the axon divides, with one branch receiving sensory information and the other sending the information into the central nervous system.

Based on your understanding of this cell's function, these cells influence neuronal function by "mopping up" leak potassium and by recapturing and recycling released neurotransmitters. These cells also participate in information processing in the brain.

Astrocyte

Which of the following neuroglia is most responsible for helping determine capillary permeability in nervous tissue?

Astrocytes

Which of the following types of glial cells are the most abundant and versatile and aid in making exchanges between capillaries and neurons?

Astrocytes

Which statement is true of the glial cell pictured above?

Glial cell processes touch nearby neurons, monitoring their health, and when they sense that certain neurons are injured or in other trouble, the microglial cells migrate toward them.

Dendrites

Highly branched extensions that receive signals from other neurons. -transmit signals TOWARD cell body *Graded potentials

Transmembrane potentials: synaptic activity

Releases neurotransmitters at presynaptic membrane Produces graded potentials in postsynaptic membrane

Transmembrane potentials: information processing

Response (integration of stimuli) of postsynaptic cell

Considering the direction of axonal transport, which type of transport allows certain viruses to circumvent the barrier created by astrocytes to enter into the CNS?

Retrograde transport

Two divisions of PNS

Sensory (afferent) Motor (efferent)

Multiple sclerosis is __________

an autoimmune disease that leads to destruction of the myelin sheaths in the CNS

Neuroglia: Astrocytes (CNS)

assists in exchanges between capillaries and neurons least permeable most numerous

The somatic nervous system __________.

conducts impulses from the CNS to the skeletal muscles

parasympathetic nervous system

conserves energy; housekeeping

The central nervous system __________.

consists from the brain and spinal cord to skeletal muscles

Match the system with its correct description: The peripheral nervous system __________

consists of cranial and spinal nerves carrying impulses to and from the brain and spinal cord

Cell body

contains typical organelles (except centrioles) -rough ER (Nissl bodies) well developed -microtubules and neurofibrils (bundles of intermediate filaments) maintain cell shape

Many axons are myelinated

covered with a fatty myelin sheath -protects and insulates axon

clusters of cell bodies in CNS

nuclei

Based on your understanding of the different types of glial cells, the cell depicted by the arrow is most likely a __________.

oligodendrocyte or a Schwann cell

bipolar neuron

one axon and one dendrite; rare (found in retina of eye and olfactory mucosa)

grey matter

processing nervous impulses

Reflexes are __________

rapid automatic responses to a stimulus in which the particular stimulus always produces the same motor response

white matter

sending nervous impulses

The somatic sensory (afferent) fibers of the peripheral nervous system transmit information from the __________ to the CNS.

skin

Neurons

structural units of NS -conduct electircal impulses -extremely long-lived -amitotic -high metabolic rate (constant supply of O2 and glucose) -composed of 1 cell body and 1 or more processes

Neuroglia: Microglia (CNS)

surround and engulf debris eliminate microbes and damaged neurons least numerous

Neuroglia in PNS: Satellite cells

surround neuron cell abides in PNS; function similar to astrocyte in CNS

Transmembrane potentials: graded potential

temporary, localized change in resting potential caused by stimulus

Bodily functions that follow "a law unto itself" are controlled by the involuntary nervous system. This system is also termed __________ and functions to __________.

the autonomic nervous system (ANS); conduct impulses from the CNS to cardiac muscle, smooth muscle, and glands

Resting Membrane Potential (RMP)

the charge difference across the plasma membrane; -70mV (the - value means there are more - charged part. inside the memo. than out)

Neurotransmitters

"language of nervous system" chemicals to send signals between neurons

In a resting neuron

Na+ greater outside neuron K+ greater inside neuron they are essentially equal, but since large negatively charged proteins, it has a negative charge

You are driving and see a red light ahead. Your nervous system indicates "stop", and your foot hits the brake. Which portion of the nervous system, as indicated in the figure, is responsible for the decision to stop?

B. Integration. The nervous system processes and interprets sensory input and decides what should be done at each moment—a process called integration.

Central Nervous System (CNS)

Brain Spinal cord (dorsal body cavity)

Telodendria (axon terminals)

Branches at the end of an axon, with each process containing a synaptic knob at its end

What is the difference between nerves and tracts?

Bundles of axons are called tracts in the CNS and nerves in the PNS.

If blue, in the figure shown, represents a neuron communicating between the eye and the portion of the brain responsible for interpreting vision, then neuron A is in what type of nerve?

Cranial nerve

If blue, in the figure shown, represents a neuron communicating between the eye and the portion of the brain responsible for interpreting vision, then neuron blue is in what type of nerve?

Cranial nerve

Peripheral Nervous System (PNS)

Cranial nerves Spinal nerves Ganglia

Summary on Processes

Dendrite-recieves info, produces graded potential Cell Body- info processing integration center Axon Hillock- production of action potential Axon-sends/transmits neural impulses AWAY from cell body

Hyperpolarization

K channels remain open TEMPORARILY NA channels reset

"Graded"

Magnitude varies from small to large depending on stimulus strength or intensity increase change in voltage, increase current flow sodium makes it more postive

Based on your understanding of this cell's function, you might expect this cell to be active in neurodegenerative disorders like Alzheimers where this cell removes damaged neurons. Additionally, this cell is active in preventing encephalitis and meningitis due to its ability to phagocytize microorganisms.

Microglia

Considering the function of the soma, what structures are likely carried by anterograde movement?

Mitochondria, cytoskeletal elements, membrane components used to renew the axon plasma membrane, and enzymes needed to synthesize certain neurotransmitters

Which disease is directly related to demyelination?

Multiple sclerosis

Neurons can be classified structurally by the number of processes extending from their cell bodies. Which of the following is the most common neuron type in humans?

Multipolar

Classification of Neurons (based on # of processes)

Multipolar Bipolar Unipolar

If we consider the process where neurons receive signals from and send signals to score of other neurons a "conversation," which type of neuron seems to have the most to "listen and say?"

Multipolar neurons

Based on your understanding of this cell's function, diseases that affect the myelin sheath of neurons, like multiple sclerosis, likely affects which of the cells in the figure?

Oligodendroctye

Divisions of the Motor Division

Somatic nervous system Autonomic nervous system (ANS)

Divisions of the ANS

Sympathetic division Parasympathetic division

Thinking of the structure and function of the neuron, as well as the structure of the PNS, which portion of the neuron is predominately found only in the PNS?

The PNS consists chiefly of neuron processes which include both axons (C) and dendrites (A)

Which of the following statements about the developmental aspects of neurons is incorrect?

The number of adult neurons is the same as the number formed during the embryonic period.

The somatic nervous system __________

conducts impulses from the CNS to the skeletal muscles

Depolarization

The process during the action potential when sodium is rushing into the cell causing the interior to become more positive.

In the figure above, the arm most specifically represents which subdivision of the nervous system?

The somatic nervous system

What is the primary difference between the somatic nervous system and the autonomic nervous system?

The somatic nervous system allows us to consciously control our skeletal muscles, and the autonomic nervous system controls activity that humans cannot consciously control, such as the pumping of the heart and the movement of food through the digestive tract.

Ohm's Law

V=IR The relationship of voltage, current, and resistance greater the voltage (potential difference), greater the current current is inversely proportional to resistance

Repolarization

Voltage gates Na+ channels CLOSE (inactivation gates close) Voltage gated K+ channels OPEN

Principles of Electricity

Voltage: a measure of potential energy generated by separated, in V or mV Current: flow of electrical charge (ions) between two points Resistance: hindrance of charge flow Ohm's law: gives relationship of voltage, current, resistance

Graded potential

a localized change (depolarization or hyperpolarization) in the membrane potential -magnitude varies w/ stimulus strength -magnitude descreases w/ distance

In the figure above, which color(s) correspond to the peripheral nervous system?

blue and red represent portions of the peripheral nervous system (PNS).

Action potential (nerve impulse)

brief REVERSAL of membrane potential (-70mV to +30mV) -must depolarize to threshold -al or none response -always a DEPOLARIZATION -no matter how strong stimulus is, cannot make another action potential

Neuroglia: Ependymal Cells (CNS)

ciliated line central cavities of brain and spinal cord

Interneurons (association neurons)

conduct info from sensory neuron to motor neuron -most are multipolar; found ONLy in CNS within nuclei

sensory (afferent) neurons

conduct info from sensory receptors TOWARD CNS -most are unipolar

Which of the following line the central cavities of the brain and spinal cord and provide a fairly permeable barrier between the CSF and nervous tissue?

ependymal cells

Which of the following types of glial cells line the central cavities of the brain and spinal cord, where they help to circulate the cerebrospinal fluid?

ependymal cells

EPSP

excitatory post synaptic potential -neurotransmitter opens Na+/K+ gates; casues local DEPOLARIZATION of postynaptic neuron

Process

extend from cell body (two types: dendrites and axons)

Neuroglia: Oligodendrocytes

form myelin sheaths

Neuroglia in PNS: Schwann cells

form myelin sheaths around neurons in the PNS; vital to regeneration of damaged peripheral nerve cells

clusters of cell bodies in the PNS

ganglia

IPSP

inhibitory postsynaptic potential -Neurotransmitter opens K+ or Cl- gates; causes a local HYPERPOLARIZATION of postsynaptic neuron -makes generating an AP more DIFFICULT in postsynaptic neuron

resting membrane potential

inside ion higher potassium lower sodium negative charge on inside postive charge on outside rapidly changes in polarity negative on outside postive on inside

Transmembrane potentials: action potential

is an electrical impulse always generated in axon itself produced by graded potential propagates along surface of axon to synapse

Nervous system

master controlling and communication system of the body

sympathetic nervous system

mobilizes body systems during activity

Axons

nerve fiber, only 1 axon/neuron on every single nerve -generate and transmit nerve impulses AWAY from cell body -branches at tip to form TERMINAL BRANCHES (telodendria)

Motor (efferent) neurons

neurons that carry outgoing information (info AWAY from CNS towards effectors) -all multipolar; most cell bodies concentrated INSIDE CNS within nuclei

The voluntary nervous system is to the involuntary nervous system as __________.

the somatic nervous system is to the autonomic nervous system

Transmembrane potentials: resting potential

transmembrane potential of resting cell

Depolarization

voltage change that occurs when the difference in charge across a membrane decreases

Propagation of an Action potential

wave of impulse moving down the axon to the axon terminals; action potentials are generated at one end of the axon and move toward the axon terminals