unit 4 A&P

o (The membrane of a resting neuron is polarized, and the potential difference of this polarity (approximately _____) is called the _________ ______ _______

-70 mV resting membrane potential.

CSF is reabsorbed by ________ _________

arachnoid granulations

Generation of an Action Potential

local stimulus changes membrane potential to open gates and let sodium in you have to have enough gates open that it reaches a threshold number (-50/-55) in order to have an AP

Describe how meninges, cerebrospinal fluid, and the blood-brain barrier protect the CNS

meninges-three membranes surrounding brain and spinal cord-protect against physical damage CSS-protect against physical damage BBB-provides a defence against disease-causing pathogens and toxins that may be present in our blood

identify the three major regions of the brain stem and note the functions of each area

midbrain-is comprised of the cerebral peduncles pons-contains fiber tracts that complete conducting pathways between the brain and spinal cord. medulla oblongata=location of several visceral motor muclei controlling vital funtions such as cardiac and respiratory rate.

thalamus

motor control sensory emotion "Gateway to the cerebral cortex" Nearly all input to cerebrum synapses in thalamic nuclei

Define neuron describe its important structural components, and relate each to a functional role.

nerve cell

The resting membrane potential exists only across the membrane and is mostly due to two factors: differences in ionic makeup of intracellular and extracellular fluids and differential membrane permeability to those ions.)

positive outside negative inside=polarized(at rest) regulated by sodium-potassium pump

Distinguish between electrical and chemical synapses by structure and by the way they transmit information.

presynaptic and postsynaptic

Action Potentials

rapid up and down shift in membrane potential that can travel a long distance down axon ALWAYS A RAPID DEPOLARIZATION FOLLOWED BY HYPERPOLARIZATION

Prefrontal cortex

responsible for judgement

Peripheral nervous system contains __________ and ___________ divisions each with __________ and ________ subdivisions

sensory-carries signals from receptors to CNS motor- carry signal to effectors FROM CNS somatic(sensory division)-carries signals from receptors in the skin, muscles, bones, and joints visceral(sensory division)-carries signals from the viscera (heart, lungs, stomach, and urinary bladder)

o 2- Optic

sight

All CSF ultimately escapes through three pores that lead into _________ ________ of brain and spinal cord surface

subarachnoid space

local potential

temporary,short range change in voltage can be excitatory(depolarized) or inhibitory(hyperpolarize)

Diancephalon

thalamus, hypothalamus, epithalamus

Synapses

tiny gaps between dentrites and axons of different neurons

true or false usually only nerves in pns can regenerate

true

true or false Damaged CNS axons usually unable to regenerate

true

The cranial dura mater is comprised of ____ layers that are separated by ________ _______ , which collect blood circulating through brain

two dural sinuses,

Ependyma

type of neuroglia that lines ventricles and covers choroid plexus Produces cerebrospinal fluid

CSF penetrates the walls of the ______ and mixes with the ______ in the sinus

villi blood

List the types of neuroglia, where they are found and what they do

where are they found-in nervous system-more glia than neurons 10:1 ratio what does it do- GLIA ARE KNOWN TO HAVE A CENTRAL ROLE IN CHRONIC PAIN-glia is glue-bind neurons together- make framework-guide and protect neurons 4 types of glia IN CNS 1. Oligodendrocytes • Form myelin sheaths in CNS that speed signal conduction • Arm-like processes wrap around nerve fibers 2. Ependymal cells • Cuboidal epithelium with cilia on apical surface • Line internal cavities of the brain • Secrete and circulate cerebrospinal fluid (CSF) 3. Microglia • Macrophages • Develop from white blood cells (monocytes) and become concentrated in areas of damage 4. Astrocytes • Most abundant glia in CNS • Cover brain surface and most nonsynaptic regions of neurons • Diverse functions: • Create a supportive framework • Form the blood-brain barrier • Monitor activity; regulate blood flow to match the metabolic need • Convert glucose to lactate; supply this to neurons • Secrete nerve growth factors • Communicate electrically with neurons. • Regulate the chemical composition of tissue fluid • Astrocytosis or sclerosis—when neuron is damaged, astrocytes form hardened scar tissue and fill in space Two types of glia in PNS 1. Schwann cells • Wind around the axon • Form myelin sheaths • Assist in regeneration of damaged fibers 2. Satellite cells • Surround the somas of PNS neurons inside ganglia • Provide electrical insulation • Regulate the chemical environment

if a neuron doesn't have a myelin sheath does it still conduct an action potential

yes

Cerebrospinal fluid (CSF)

• Clear, colorless liquid • Fills the ventricles and canals of CNS• Surrounds brain and bathes its external surface continuously flows through the CNS

meninges layers inner to outer

• Dura mater • Arachnoid mater • Pia mater

Explain the importance of the myelin sheath and describe how it is formed in the central and peripheral nervous systems.

• Insulation around the axon • Increases action potential conduction velocity • Consists of the plasma membrane of glial cells • 20% protein and 80% lipid • Formed by: • Oligodendrocytes in CNS • Schwann cells in PNS

myelin sheath segmentation

• Many Schwann cells (PNS) or oligodendrocytes (CNS) are needed to myelinate one axon • Nodes of Ranvier—gaps between segments • Internodes—myelin-covered segments • Trigger zone—axon hillock and initial segment • Plays important role in initiating nerve signal

Epithalamus

Pineal gland: endocrine gland

Two major subdivisions of nervous system:

-Central nervous system (CNS) • Brain and spinal cord• Enclosed by cranium and vertebral column Peripheral nervous system (PNS) • Entire nervous system except the brain and spinal cord; composed of nerves and ganglia • Nerve—a bundle of nerve fibers (axons) wrapped in fibrous connective tissue • Ganglion(little bubble)—a knot-like swelling in a nerve where neuron cell bodies are concentrated

o I - Olfactory

1

Define absolute and relative refractory periods.

Refractory Period- period of resistance to stimulation Absolute Refractory Period - Incapable of generating another action potential Relative Refractory Period - Requires greater than normal amount of stimulation to generate another action potential

one cerebellum can have ______ synapes

100,000

11. Accessory

11

12. Hypoglossal

12

III. Oculomotor

3

4. Trochlear

4

6. Abducens

6

o 7- Facial

7

9. Glossopharyngeal

9

Visceral motor division categories

Sympathetic division "fight or flight" • Tends to arouse body for action• Accelerates heartbeat and respiration• Inhibits digestive and urinary systems Parasympathetic division "read, rest, sex, and digest" • Tends to have calming effect• Slows heart rate and breathing• Stimulates digestive and urinary systems

Describe the structure and function of the cerebellum vs cerebrum

Cerebrum (cerebral hemispheres) 83% of brain volume Seat of sensory perception, memory, thought, judgment, and voluntary motor actions cerebellum 11% of brain mass Dorsal to pons and medulla processes input from cortex, brain stem and sensory receptors Allows smooth, coordinated movements Superficial cortex of gray matter with folds (folia), branching white matter (arbor vitae), and deep nuclei

o Identify the components of a spinal nerve

Dorsal (sensory) and ventral (motor) roots

Define resting membrane potential and describe its electrochemical basis.

Electrical gradient (voltage) across the membrane when neuron is "at rest" (not actively sending electrical signals) RMP exists because: • Specific ions are unequally distributed between the extracellular fluid (ECF) and intracellular fluid (ICF) • The membrane is selectively permeable to certain ions, especially sodium (Na+ ) and potassium (K+ )

functional properties of neurons ECS

Excitability (irritability) • Respond to environmental changes (stimuli) Conductivity • Produce electrical signals that travel along nerve fibers (axons) to reach other cells at distant locations Secretion • Nerve fiber endings (axon terminals) release chemical neurotransmitters that influence other cells

List the major lobes, fissures, and functional areas of the cerebral cortex

GYRI: elevated ridges of tissue. SULCI: shallow grooves FISSURES: deeper grooves LONGITUDINAL FISSURE: seperates the cebral hemispheres Corpus callosum—thick nerve bundle at bottom of longitudinal fissure that connects hemispheres cerebral cortex-covers surface of the hemispheres

Differentiate between (1) a nucleus and a ganglion and (2) a nerve and a tract.

Ganglion—a knot-like swelling in a nerve where neuron cell bodies are concentrated nucleus-holds dna and chromosomes nerve-—a bundle of nerve fibers (axons) wrapped in fibrous connective tissue tract-

what are the cranial nerves

I. Olfactory II. Optic III. Oculomotor IV. Trochlear V. Trigeminal VI. Abducens VII. Facial VIII. Vestibulocochlear IX. Glossopharyngeal X. Vagus XI. Accessory XII. Hypoglossal

Higher brain functions

Involve interactions between cerebral cortex and basal nuclei, brainstem, and cerebellum• Do not have easily defined anatomical boundaries • Combined action of multiple brain levels

o 10 -Vagus

Major role in the control of cardiac, pulmonary, digestive, and urinary function • Swallowing, speech, regulation of viscera

diseases of myelin sheath

Multiple Sclerosis (MS)-• Oligodendrocytes and myelin sheaths in CNS deteriorate • Myelin replaced by hardened scar tissue can be autoimmune Tay-Sachs Disease-• Hereditary disorder seen mainly in infants of Eastern European Jewish ancestry • Usually fatal before age 4 • Abnormal accumulation of glycolipid called GM2 in the myelin sheatha

structural classifications of neurons

Multipolar neuron • One axon and multiple dendrites • Most neurons in CNS Bipolar neuron • One axon and one dendrite • Olfactory cells, retina, inner ear Unipolar neuron • Single process leading away from soma • Sensory cells from skin and organs to spinal cord Anaxonic neuron • Many dendrites but no axon • Retina, brain, and adrenal gland

Action potentials are all-or-none phenomena: they either happen completely, in the case of a threshold stimulus, or not at all, in the event of a subthreshold stimulus. what are two characteristics of action potentials

Nondecremental—do not get weaker with distance Irreversible—once started, an action potential travels all the way down the axon cannot be stopped

3 functional classes of neurons SIM

Sensory (afferent) neurons • Detect stimuli and transmit information about them toward the CNS Interneurons (middle men) • Lie entirely within CNS connecting motor and sensory pathways (about 90% of all neurons) • Receive signals from many neurons and carry out integrative functions (make decisions on responses) Motor (efferent) neurons • Send signals out to muscles and gland cells (the effectors)

structural components of neurons

Soma (cell body) • Has centrally located nucleus with large nucleolus • Cytoplasm contains all typical Organelles • Nutrients or pigments found within a cell • Cytoskeleton • Dense mesh of microtubules and neurofibrils (actin filaments) • No centrioles • Neurons cannot undergo mitosis after adolescence Dendrites (incoming) • Multiple branches that come off the soma • Primary site for receiving signals from other neurons • Axon (nerve fiber) (outgoing) • Specialized for rapid conduction of electrical signals • Only one axon per neuron (some neurons have none) • Originates at the axon hillock (mound on the neurosoma)

functions of network

Somatic motor control Cardiovascular control- Cardiac and vasomotor centers of medulla oblongata Sleep and consciousness

o Understand the roles / components of these divisions (i.e., somatic vs. autonomic, sympathetic vs. parasympathetic

Somatic motor division • Carries signals to skeletal muscles • Output produces: • Muscular contraction • Somatic reflexes (involuntary muscle contractions) (autonnomic)Visceral motor division • Carries signals to glands, cardiac and smooth muscle• Its involuntary responses are visceral reflexes *divided into sympathetic and parasympathetic* -sympathetic----> amps up, excites -parasympathetic---> calms down, rest, undoes sympathetic

conduction velocity

Speed at which a nerve signal travels down an axon depends on two factors: • Diameter • Larger axons have more surface area and conduct signals more rapidly • Presence or absence of myelin • Myelin speeds signal conduction

unmyelinated axons

Thin nerve fibers are unmyelinated One Schwann cell may incompletely enclose 15 or more unmyelinated axons

Hypothalamus

attaches to the pituitary through a stalklike structure called the infundibulum major control center of autonomic nervous system and endocrine system• Essential role in homeostatic regulation of all body systems

what does the motor (efferent)division do?

carries signals FROM CNS to effectors (glands and muscles that carry out the body's response)

Neurons use changes in membrane potential as ___________ signals and can be brought on by changes in membrane permeability to any ion or alteration of ion __________ on the two sides of the membrane.

communication concentrations

Compare and contrast the roles of rods and cones in vision. Ear/Hearing/Equilibrium

cones= high color conditions vision rods=used in low color condition

in a fetus, Nervous system develops from _____

ectoderm-Outermost tissue layer of the embryo

myelinated axons

electrical signal jumps from node to node-saltatory

Define saltatory conduction and explain how it differs from continuous conduction.

electrical signal jumps from node to node-saltatory Like a wave of falling dominoes-slow conduction that occurs in nonmyelinated axons

Regeneration is not _________, __________, or _________

fast, perfect, or always possible

5 Lobes of the brain

frontal,-Voluntary motor functions, motivation, foresight, planning, memory, mood, emotion, social judgment, and aggression parietal-Integrates general senses, taste, and some visual information , occipital, -Primary visual center of brain temporal-Functions in hearing, smell, learning, memory, and some aspects of vision and emotion Insula (hidden by other regions) • Helps in understanding spoken language, taste and integrating information from visceral receptors

Changes in membrane potential can produce either __________ _________, usually incoming signals that travel ________ distances, or action potentials, ________ distance signals on axons.

graded potentials short long-

gray matter vs. white matter

gray- on outside of brain, inside spinal cord Contains cell bodies, dendrites, and synapses• Darker color due to very little myelin present in tissue• Forms surface layer (cortex) over cerebrum and cerebellum• Forms nuclei deep within brain white- inside brain, on outside of spinal cord Bundles of axons• White color from lots of myelin• Called "tracts" in the CNS, "nerves" in the PNS

o 5- Trigeminal

has three branches

o 8 - Vestibulocochlear

hearing

Feelings (for example, fear) arise from

hypothalamus and amygdala

lymbic system

important center of emotion and learning There is a limbic system in each cerebral hemisphere Limbic system structures have centers for gratification and aversion •Gratification: sensations of pleasure or reward • Aversion: sensations of fear or sorrow

recticular formation

in midbrain of brainstem Loose web of gray matter that runs vertically through all levels of the brainstem and into the upper spinal cord

Remember: Relative to the resting state, potential changes can be depolarizations, in which the ____________ of the membrane becomes _______ negative, or hyperpolarizations, in which the inside of the membrane becomes _______ negatively charged.

inside less more

Nervous system carries out its task in three basic steps:

• Sense organs receive information about changes in the body and external environment, and transmit coded messages to the brain and spinal cord (CNS: central nervous system). Incoming =sensory=afferent • CNS processes this information, relates it to past experiences, and determines appropriate response. • CNS issues commands to muscles and gland cells to carry out such a response. Outgoing = motor=efferent

Conduction speed

• Small, unmyelinated fibers: about 0.5 to 2.0 m/s • Small, lightly myelinated fibers: 3 to 15.0 m/s • Large, myelinated fibers: up to 120 m/s • Faster conduction velocities are required for some things, such as motor control/muscle coordination • Slower conduction velocities are sufficient for processes in which quick responses aren't needed

Regeneration of damaged PNS nerve fiber (axon) can occur if:

• Soma intact • At least some neurilemma remains