Ch. 11 Fundamentals of the Nervous System and Nervous Tissue

Peripheral nervous system (PNS) has two functional divisions:

1. Sensory (afferent) division 2. Motor (efferent) division

Nervous system has three overlapping functions:

1. Sensory input 2. Integration 3. Motor output

_______________ potentials Incoming signals operating over short distances. ____________ potentials Long-distance signals of axons.

Graded Action

_____________________________: increase in membrane potential (away from zero). More negative.

Hyperpolarization

_______________________________: Some K+ channels remain open, and Na+ channels reset.

Hyperpolarization

***_______________ _________________________ postsynaptic neuron is stimulated by large number of terminals simultaneously.

Spatial summation

***_________________ _______________________ one or more presynaptic neurons transmit impulses in rapid-fire order.

Temporal summation

***Two types of summations by the postsynaptic neuron:

Temporal summation Spatial summation

________________ bundles of neuron processes in the CNS. ________________ bundles of neuron processes in the PNS.

Tracts Nerves

The symptoms of MS:

Visual disturbances Weakness Loss of muscular control Speech disturbances Incontinence

***_______________ _______________ regions of brain and spinal cord with dense collections of myelinated fibers. ______________ ________________ mostly neuron cell bodies and nonmyelinated fibers.

White matter Gray matter

Myelin sheaths in the CNS are formed by processes of __________________________, not whole cells. No outer collar of perinuclear cytoplasm. Myelin sheath is _______________.

oligodendrocytes present

Neuron Cell Body also called the Most neuron cell bodies are located in CNS (2):

perikaryon or soma -Nuclei -Ganglia

Nervous system originates from neural ________ and neural crest formed from ectoderm.

tube

Neuroglia (glial cells) are small cells that surround and _________ delicate neurons. Neurons (nerve cells) excitable cells that transmit _______________ signals.

wrap electrical

***Threshold is what #? The membrane is said to be polarized. Resting membrane potential (RMP) is what #? Hyperpolarization is what #?

-55mV -70mV -90mV

Four main neuroglia support CNS neurons:

-Astrocytes -Microglial cells -Ependymal cells -Oligodendrocytes

Central Nervous System (CNS)

-Brain and spinal cord of dorsal body cavity -Integration and control center

Oligodendrocytes

-Branched cells -Processes wrap CNS nerve fibers, forming insulating myelin sheaths in thicker nerve fibers

***Astrocytes

-Most abundant, versatile, and highly branched of glial cells -Cling to neurons, synaptic endings, and capillaries

Nervous tissue consists of two principal cell types:

-Neuroglia (glial cells) -Neurons (nerve cells)

Ependymal cells

-Range in shape from squamous to columnar -May be ciliated • Cilia beat to circulate CSF -Line the central cavities of the brain and spinal column -Form permeable barrier between cerebrospinal fluid (CSF) in cavities and tissue fluid bathing CNS cells

Two major neuroglia seen in PNS:

-Satellite cells -Schwann cells (neurolemmocytes)

Microglial cells

-Small, ovoid cells with thorny processes that touch and monitor neurons -Migrate toward injured neurons -Can transform to phagocytize microorganisms and neuronal debris

Somatic nervous system:

-Somatic motor nerve fibers conduct impulses from CNS to skeletal muscle -Voluntary nervous system • Conscious control of skeletal muscles

***Astrocytes (cont.) Functions include:

-Support and brace neurons -Play role in exchanges between capillaries and neurons -Guide migration of young neurons -Control chemical environment around neurons -Respond to nerve impulses and neurotransmitters -Influence neuronal functioning -Participate in information processing in brain

Schwann cells (neurolemmocytes)

-Surround all peripheral nerve fibers and form myelin sheaths in thicker nerve fibers • Similar function as oligodendrocytes -Vital to regeneration of damaged peripheral nerve fibers

Satellite cells

-Surround neuron cell bodies in PNS -Function similar to astrocytes of CNS

Peripheral Nervous System (PNS)

-The portion of nervous system outside CNS -Consists mainly of nerves that extend from brain and spinal cord Spinal nerves to and from spinal cord Cranial nerves to and from brain

Nuclei

-clusters of neuron cell bodies in CNS.

Ganglia

-clusters of neuron cell bodies in PNS.

***Sensory (afferent) division consists of somatic and visceral sensory fibers. Somatic sensory fibers: Visceral sensory fibers:

-convey impulses from skin, skeletal muscles, and joints to CNS -convey impulses from visceral organs to CNS

Autonomic nervous system consists of ________________ motor nerve fibers. Regulates smooth muscle, cardiac muscle, and glands. __________________ nervous system. Two functional subdivisions of this system are:

-visceral -Involuntary -Sympathetic -Parasympathetic

Nervous system is divided into two principal parts:

1. Central Nervous System (CNS) 2. Peripheral Nervous System (PNS)

+++There are two types of refractory periods: ___________________ refractory period. Not "firing" absolutely not. ___________________ refractory period. If strong enough signal, it'll fire.

Absolute Relative

Motor output

Activation of effector organs (muscles and glands) produces a response

_______________________ amnesia is consolidated memories are not lost, but new inputs are not associated with old one.

Anterograde

__________ is the conducting region of neuron. They rely on cell bodies to renew ______________ and membranes.

Axon proteins

Tx of MS: drugs that modify immune system activity. May not able to prevent, but maintaining high blood levels of Vitamin _____ may reduce risk of development.

D

_______________________ are the receptive (input) region of neuron. Convey incoming messages toward cell body as ______________ _____________________ (short distance signals).

Dendrites graded potentials

________________________: Na+ channels open. At threshold (-55 to -50 mV), positive feedback causes opening of all Na+ channels.

Depolarization

__________________________: decrease in membrane potential (moves toward zero and above). Less negative (more positive)

Depolarization

Sensory input

Information gathered by sensory receptors about internal and external changes

***__________________________ also called association neurons. Lie between motor and sensory neurons. Shuttle signals through CNS pathways. You will only find them in the CNS.

Interneurons

Axons have efficient internal transport mechanisms. __________________ and ___________________ are moved along axons by motor proteins and cytoskeletal elements. Movement occurs in both directions: ____________________ and _____________________.

Molecules organelles anterograde retrograde

__________________ neurons carry impulses from CNS to effectors. Multipolar. Most cell bodies are located in CNS (except some autonomic neurons).

Motor

***____________________ ______________________ is an autoimmune disease that affects primarily in young adults. The ______________ ________________ in CNS are destroyed when the immune system attacks it.

Multiple sclerosis myelin sheath

***_____________________ is the most common and major neuron type in CNS. _______________ is rare.

Multipolar Bipolar

______________ ______________ _________ are gaps between adjacent Schwann cells. Sites where axon _________________ can emerge. Formerly called nodes of Ranvier.

Myelin sheath gaps collaterals

***______________________ _____________ segmented sheath surrounds most long or large-diameter axons. __________________________ _____________do not contain sheath. Conduct impulses more slowly. Surrounde by Schwann cells, but no coiling.

Myelinated fibers Nonmyelinated fibers

______________ ___________________ are armlike processes that extend from cell body. CNS contains both neuron cell bodies and their processes. PNS contains chiefly neuron processes.

Neuron processes

Integration

Processing and interpretation of sensory input

______________________: Na+ channels are inactivating, and K+ channels open.

Repolarization

______________________ amnesia is loss of memories formed in the distant past.

Retrograde

Myelination in the PNS is formed by _________________ cells. Wraps around axon in jelly roll fashion. One cell forms one segment of myelin sheath.

Schwann

____________________ neurons transmit impulses from sensory receptors toward CNS. Almost all are unipolar. Cell bodies are located in ganglia in PNS.

Sensory

Three types of neurons grouped by direction in which nerve impulse travels relative to CNS: ____________________, ______________________, and ____________________________.

Sensory motor interneurons

***_______________- __________________ pump (Na+/K+ ATPase) stabilizes resting membrane potential. This is a 3:2 ratio

Sodium-potassium

***Anterograde is ___________ from cell body. Examples: mitochondria, cytoskeletal elements, membrane components, enzymes Retrograde is ______________ cell body. Examples: organelles to be degraded, signal molecules, viruses, and bacterial toxins

away toward

Each neuron has one axon that starts at cone-shaped area called __________ _______________.

axon hillock

Two types of neuron processes are ___________________ and ______________.

dendrites axons

Myelin sheath functions are to protect and electrically _______________ ___________. Its other function is to increase speed of ___________ ________________ transmission.

insulate axon nerve impulse

Motor (efferent) division transmits impulses from CNS to effector organs (______________ and ____________). Motor (efferent) division has two divisions:

muscles glands Somatic nervous system Autonomic nervous system

Long axons are called _____________ _________________. Axons have occasional branches called axon ____________________.

nerve fibers collaterals

***Action potentials (APs) also referred to as a ______________ __________________.

nerve impulse

Apoptosis is what?

programmed cell death

Like all cells, neurons have a ________________ membrane potential. Neurons are highly excitable.

resting

Certain viruses and bacterial toxins damage neural tissues by using _________________ _____________ transport. Example: polio, rabies, and herpes simplex viruses, and tetanus toxin

retrograde axonal

Distal endings of an axon are called axon _______________ or terminal boutons.

terminals