Chapter 11 Introduction to the Nervous System and Nervous Tissue

list the major functions of the nervous system.

sensory,integration,motor

sensory

detects changes and gather information about internal and external environments of the body.

integrative

analyze and interpret incoming sensory information and determine an appropriate response

motor

actions performed in response to integration

List the anatomical and functional divisions of the nervous system

Define neuron

excitable cell type responsible for sending and receiving signals in form of action potentials

Describe the structure and function of each component of the neuron

Define nuclei

clusters of neuron cell bodies in CNS

Define tract

bundles of axons in CNS

Define ganglia

clusters of neuron cell bodies in PNS

Define nerve

bundle of axons in PNS

list the structural classifications of neurons

multipolar,bipolar,pseudounipolar

multipolar neurons

a single axon and multiple dendrites, makes up 99% of all neurons

bipolar neurons

one axon and one dendrite and a cell body between them

pseudounipolar neurons

only one fused axon that extends from cell body and divides into two processes

list the functional classification of neurons

sensory(afferent), interneurons(association), motor(efferent)

sensory(afferent)

carry information towards CNS

interneurons(association)

relay information within CNS betweeen sensory and motor neurons

motor(efferent)

carry information away from cell body in CNS to muscles and glands

list the four type of CNS neuroglial cells

astrocytes,oligodendrocytes,microglia,ependymal cells

structure function of astrocytes

large star shaped cells whose many processes terminate in structure called end-feet

function;angie neurons and blood vessels in place to help define and maintain three-dimesnsional structure of the brain

structure and function of oligodendrocytes

have radiating processes with flattens sacs that wrap around axons of nearby neurons to form myelin sheath

structure and function of microglia

small and scarce cells that are activated by injury into wandering phagocytic cells

structures and function of ependymal cells

ciliated cells that line hollow spaces found within brain and spinal cord

function; manufacture and circulate cerebrospinal fluid

describe two types

of PNS neuroglial cells.

schwann cells, satelite cells

structure and function of schwann cells

encircle axons found in PNS to provide them with myelination

structure and function of satelite cells

found surrounding cell bodies of neurons in PNS to provide supportive functions

Describe the myelin sheath

composed of repeating layers of plasma membrane of a schwann cell or an oligodendrocyte

Define myelination

the process that forms a myelin sheath from plasma membranes of neuroglial cells

compare myelination in the PNS and CNS

Neurolemma - found on outer surface of a myelinated axon in PNS and is composed of Schwann cell nucleus, organelles, and cytoplasm

• It is not present in CNS

Number of axons myelinated - oligodendrocytes have multiple processes that can provide myelination for multiple axons in CNS, while a Schwann cell only provides myelination for one axon in PNS

Timing of myelination - myelination begins early in fetal development in PNS and much later in the CNS (little myelin present in brain of newborn)

contrast myelination in the PNS and CNS

• Axons in both CNS and PNS are generally longer than neuroglial cells so multiple cells must provide complete myelin sheath

• Internodes - segments of axon that are covered by neuroglia

• Node of Ranvier - gap between adjacent neuroglia

• where myelin sheath is absent

Define myelin sheath gap (node of Ranvier

gap between adjacent neuroglia

define white matter

cruises of myelinated axons that appear white

define grey matter

composed of neuron cell bodies, unmyelinated dendrites and axon that spider gray

compare myelination in the PNS

and CNS.

contrast myelination in the PNS

and CNS.

Define ion channel.

ions cannot diffuse through lipid component of plasma membrane

list the four type of ion channels

leakage ,ligand-gated. voltage-gated, mechanically gated

leak channel

shared open and continuously allow ions to flow down concentration gradients between cytosol and ECF

ligand-gated channels

open in response to consuming of specific chemical or ligand to a specific receptor

voltage-gated channels

open in response to change in voltage across membrane

mechanically-gated channels

open or close in response to mechanical stimualtion

Describe resting membrane potential;

voltage present when a cell is at rest (-70mV)

define voltage

electrical gradient established by separation of charges between two locations across the membrane

define membrane potential

electrical potential across cell membrane.difference between inside and outside

define polarized

when voltage difference across plasma contact does not equal 0mV.when inside is more negative than outside

define local potentials

small local changes in potential of a neurons plasma membranre

describe two possible effects of local potentials

• Depolarization - positive charges enter cytosol and make membrane potential less negative (a change from -70 to -60 mV)

• Hyperpolarization - either positive charges exit or negative charges enter cytosol and makes membrane potential more negative (a change from -70 to -80 mV)

Interpret a graph showing the voltage-versus-time relationship of an action potential, and relate

the terms depolarize, repolarize, and hyperpolarize to the events of an action potential

1. Resting state: The neuron is at approximately -70 mv.

2.   Threshold: The membrane reaches approximately -55 mV, triggering an action potential.

3.   Depolarization: Voltage-gated sodium channels open, and Nat rushes into the neuron.
   The inside becomes positive.

4.   Repolarization: Sodium channels inactivate and potassium channels open. K+ moves out, making the inside negative again.

5.   Hyperpolarization: Potassium channels close slowly, allowing extra K* to leave. The membrane becomes more negative than its resting potential.

6.   Return to resting potential: The neuron returns to approximately -70 mV

relate

the terms depolarize, repolarize, and hyperpolarize to the events of an action potential.

Define refractory period

oh of time after neuron has generated an acton potential, when neurons cannot be stimulated to generate another action potential

Explain the physiologic basis of the absolute periods.

when no additional stimulus is able to produce an additional action potential

Explain the physiologic basis of the relative refractory periods.

only a strong stimulus can produce an action potential

Make a complete comparison between local potentials and action potentials

Define nerve impulse.

action potential propagation down an axis

Explain how axon diameter and myelination affect conduction velocity.

Compare continuous and saltatory conduction.

contrast continuous and saltatory conduction.

Define synapse.

where a neuron meets its target cell

Compare electrical and chemical synapses.

contrast electrical and chemical synapses.

Describe the events of chemical synaptic transmission in chronological order.

Define excitatory postsynaptic potential (EPSP)

Define inhibitory postsynaptic potential

(IPSP).

List the three ways synaptic transmission is terminated.

Discuss the four major categories of neurotransmitters

provide examples of each

category

discuss the relationship between a neurotransmitter and its recepto