BIO 167 Exam 5 - Nervous System

organization of the nervous system

central nervous system (CNS) + peripheral nervous system (PNS)

What are the components of the CNS?

brain and spinal cord

What are the components of the PNS?

cranial nerves, spinal nerves, ganglia

What is the difference b/t motor (efferent) and sensory (afferent) division of the nervous system?

sensory (afferent) = towards CNS

motor (efferent) = away from CNS

sensory (afferent) neuron

transmits impulses from sensory receptors to CNS

motor (efferent) neuron

transmits impulses away from CNS to effecto

effector

muscles and glands that respond to stimulus

What is the difference b/t the somatic nervous system and autonomic (visceral) nervous system?

somatic = voluntary movement

autonomic = involuntary movement

Describe the histology of the nervous system.

neurons and neuroglial cells

List the general fxns of neuroglial cells and neurons.

maintain homeostasis, support, protect, regulate ions in interstitial spaces

astrocyte

structure: highly branched glial cell

location: neurons, synaptic endings, capillaries

fxn:

- support and brace neurons

•Nutrient exchange b/t neuron and capillaries

•Guide migration of young neurons

• control chem environ around neurons

•Have been found to respond to nerve impulses and release neurotransmitters

•Participate in information processing

oligodendrocyte

structure: branched cell

location: around CNS nerve fibers

fxn: accelerating nerve impulse via saltatory conduction, metabolic support to axons, and maintaining axonal health

microglia

structure: Small, ovoid cells with thorny processes that touch and monitor neighboring neuron health

location: injured neurons

fxn: transform into special macrophage to phagocytize microorganisms or neuronal debris

ependymal

structure: squamous or columnar, some have cilia

location: line central cavities of brain and spinal cord

fxn: forms permeable barrier b/t CSF in cavities and tissue fluid bathing CNS cells

Schwann cells

structure: form myelin sheaths around thicker nerve fibers

location: peripheral nerve fibers

fxn: vital to regeneration of damaged peripheral nerve fibers

satellite cells

structure: lie flat

location: surround neuron cell bodies in PNS

fxn: muscle repair, regeneration, and growth

Describe the specific anatomy of a neuron.

nerve cell body

chromatophilic substance (Nissl body)

rough ER of neuron cell body

axon hillock

site where nerve impulse begins

dendrite

convey incoming messages toward cell body as graded potentials

axon

conducting region of neuron that generates nerve impulses

axoplasm

specialized cytoplasm contained within the axon of a neuron

axolemma

axon cell membrane

axon collateral

occasional branches of axon at approx. right angles

myelin sheath

protect and insulate axon, increases speed of nerve impulse transmission

sheath of Schwann (neurilemma)

outer collar of perinuclear cytoplasm

node of Ranvier

gab b/t adjacent Schwann cells

axon terminals (synaptic end bulb)

knoblike distal ending of terminal branches

terminal branches (telodendria)

branching at end of axon

What is the difference b/t the structure of a myelinated and unmyelinated axon (nerve fiber)?

Myelinated fiber: Segmented sheath found around most long or large diameter axons

Nonmyelinated fibers: lack sheath and conduct impulses slower

multipolar neuron

structure: 3 or more processes

location: major neuron type in CNS

bipolar neuron

structure: one axon, one dendrite

location: rare, found in some special sensory organs (olfactory mucosa, eyes, ears)

unipolar neuron

structure: single short process off the neuron cell body

location: mainly in PNS, dorsal root ganglia of spinal cord, sensory ganglia of cranial nerves

List and describe the functional components in a peripheral nerve.

resting membrane potential

Explain why a resting membrane potential occurs and how it is maintained.

excitability

ability of neurons to respond to stimuli & to convert this information into nerve impulses

action potential

brief reversal of membrane potential

Describe the physiology of a continuous conduction.

Interpret a voltage vs. time graph of an action potential and describe its periods and events.

depolarization

decrease in membrane potential (-70mV → -60mV)

repolarization

hyperpolarization

increase in membrane potential (-70mV → -80mV)

refractory period

absolute refractory period

nerve cannot respond to another stimulus no matter how strong

relative refractory period

an exceptionally strong stimulus can reopen Na⁺ channels and generate another AP; threshold is elevated

all-or-none principle of impulse conduction

threshold stimulus

subthreshold stimulus

temporal summation

spatial summation

saltatorial conduction

Compare and contrast continuous and saltatorial conduction of nerve impulses.

Name the specific fiber types based on the speed of impulse conduction.

A fibers

structure: large diameter, thick myelin sheath

conduction speed: up to 150 m/s (300 mph)

location: somatic sensory and motor fibers serving skin, skeletal muscles, and joints

B fibers

structure: medium-sized, lightly myelinated fibers

conduction speed: 15 m/s (30 mph)

location: ANS visceral motor and sensory fibers, and smaller somatic sensory fibers from skin

C fibers

structure: small, nonmyelinated fibers

conduction speed: 1 m/s (2 mph)

location: ANS visceral motor and sensory fibers, and smaller somatic sensory fibers from skin

neuromuscular junction

neuron - muscle

neuroglandular junction

neuron - gland

synapse

neuron - neuron

What is the general structure of a synapse?

Presynaptic neuron - postsynaptic neuron

Axodendritic synapses

Axosomatic synapses

synaptic cleft

presynaptic neuron

postsynaptic neuron

one-way impulse conduction

neurotransmitter

synaptic vesicle

facilitation

Explain the physiology of an excitatory postsynaptic potential (EPSP).

Explain the physiology of an inhibitory postsynaptic potential (IPSP).

Describe the neural integration of EPSP’s and IPSP’s.

acetylcholine

site of release: neuromuscular junctions and by many neurons of the autonomic nervous system

general action: binds to postsynaptic receptors

mechanism for inactivation: acetylcholinesterase

norepinephrine

site of release:

general action:

mechanism for inactivation: Catechol-O-Methyltransferase (COMT), Monoamine Oxidase (MAO)

cholinergic effect

adrenergic effect

List examples of neurotransmitters.

white matter

gray matter

nerve

ganglion

nucleus

tract

ascending tract

descending tract

Identify the major regions of the brain and list the specific parts contained within each major region.

cranial meninges

structure:

location:

List in order the structures passed from the bone of the skull to the surface of the brain.

epidural space

dural veinous sinus

arachnoid villi

arachnoid trabeculae

falx cerebri

tentorium cerebelli

falx cerebelli

Compare and contrast the structure of cranial and spinal meninges.

medulla oblongata

location:

structure:

fxn:

pons

location:

structure:

fxn:

midbrain

location:

structure:

fxn:

structural/functional significance: ascending and descending tracts