Test Five Review

1. List and describe the characteristics of the major subdivisions of the nervous system

2. List, describe and give the functions of the neuroglia found in the CNS and the PNS.

Neuroglia

• Provide the support for neurons via glia cells• Six types– In the CNS• Astrocytes• Microglia• Ependymal cells• Oligodendrocytes

– In the PNS• Satellite cells• Schwann cells

Astrocytes (CNS)

• Most abundant, versatile & highly branched glia cells

• They cling to neurons w/ their synaptic endings & cover capillaries

• Function:– Support and brace neurons– Anchor neurons to their nutrient supplies– Guide migration of young neurons– Control the chemical environment

3. Diagram, label and give the functions for the parts of a typical neuron.

Processes of Neurons

• Arm like processes extend from the cell body of all neurons– Bundles in the CNS= tracts– Bundles in the PNS= Nerves

• Two types of processes:– Dendrites– Axons

The Axon, continued

• Two regions– Conducting region• Generates and transmits nerve impulses

– Secretory region• At the axon terminals• When stimulated by the preceding nerve impulses

releases neurotransmitters (can be + or -)

The Axon, continued

• Organelles– Contains same organelles as cell body and

dendrites– Except NO nissil bodies and golgi apparatus• Depends on cell body for these functions

• Axolemma– Axon plasma membrane

The Axon, continued

• Movement of substances– Anterograde-toward axon terminal• Mitochondria, cytoskeletal elements, membrane

components, enzymes

– Retrograde-toward cell body• Organelles being returned for destruction• Intracellular communication• Certain viruses or bacteria

4. Classify neurons based on their structure and function.

*Classification of Neurons

• Structurally– Multipolar– Bipolar– unipolar

• Functionally– Sensory (afferent)– Motor (efferent)– Interneurons or

association

Functional Classification

• Sensory (afferent) neurons– Transmit impulses from sensory receptors in the

skin or internal organs toward the CNS– Most are unipolar– Cell bodies located in sensory ganglia outside the

CNS– Peripheral processes can be very long

Functional Classification

• Motor (efferent) neurons– Carry impulses away from the CNS to the effector

organs (muscles and glands)– Multipolar– Cell bodies located in the CNS

Functional Classification

• Interneurons or Association neurons– Lie b/w motor and sensory neurons in neural

pathways– Multipolar– 99% of neurons in the body

5. Describe resting membrane potential and describe how it is created and maintained.

6. Define action potential and be able to draw and label a typical neuronal action potential.

7. List the events involved in the initiation and propagation of an action potential.

8. Define all or none response in neurons.

potentials

9. Compare absolute and relative refractory periods.

10. Compare rate of impulse conduction on myelinated and unmyelinated neurons.

of

11. Define graded potential an give examples of types of graded potentials.

Graded Potentials

• Receptor potential or generator potential– when the receptor of a sensory neuron is excited by some form of energy (heat, light or other

• Postsynaptic potential—when the stimulus is a neurotransmitter released by another neuron.. The neurotransmitter is released into a fluid-filled gap called a synapse and influences the neuron beyond (post) the synapse

12. Compare graded and action potentials.

13. Describe the structure of electrical and chemical synapses.

Electrical Synapses

• Are less common than chemical synapses• Correspond to gap junctions found in other

cell types• Are important in the CNS in:– Arousal from sleep– Mental attention– Emotions and memory– Ion and water homeostasis

Chemical Synapses

• Specialized for the release and reception of neurotransmitters

• Typically composed of two parts:– Axonal terminal of the presynaptic neuron, which

contains synaptic vesicles• Contain neurotransmitters

– Receptor region on the dendrite(s) or soma of the postsynaptic neuron

14. List the events in nerve-nerve chemical synaptic transmission.

15. Distinguish between temporal summation and spatial summation.

Summation

• A single EPSP cannot induce an AP– But multiple hits can increase the probability– Adding together = summate– Two types• Temporal summation• Spatial summation

Summation

• Temporal summation– When one or more presynaptic neurons transmits

impulses in rapid bursts• Releases NTs quickly

• Spatial Summation– When the postsynaptic neurons is stimulated by a

large # of terminals from the same or multiple neurons

Summation

• IPSPs can also summate with EPSPs, canceling each other out

• Neurons can also be facilitated – More easily excited by successive depolarization

events b/c they are already near threshold

16. Describe the structure and function of the spinal cord.

Spinal cord

• CNS tissue is enclosed within the vertebral column from the foramen magnum to the first Lumbar vertebrae

• Provides two-way communication to and from the brain

• Protected by bone, meninges, and CSF• Epidural space- space between the vertebrae

and the dural sheath (dura mater) filled with fat and a network of veins

17. List the three meninges that surround the brain and spinal cord and their functions.

Meninges

• Three connective tissue membranes lie external to the CNS—dura mater, arachnoid mater, and pia mater

• Functions of the meninges– Cover and protect the CNS– Protect blood vessels and enclose venous sinuses– Contain cerebrospinal fluid (CSF)– Form partitions within the skull

Dura Mater

• Leathery, strong meninx composed of two fibrous connective tissue layers

• The two layers separate in certain areas and form dural sinuses

• Three dural speta extend inward and limit excessive movement of the brain– Falx cerebri—fold that dips into the longitudinal fissure– Falx cerebelli—runs along the vermis of the cerebellum– Tentorium cerebelli—horizontal dural fold extends into

the transverse fissure

Arachnoid Mater

• The middle meninx, which forms a loose brain covering

• It is separated from the dura mater by the subdural space

• Beneath the arachnoid is a wide subarachnoid space filled with CSF and large blood vessels

• Arachnoid villi protrude superiorly and permit CSF to be absorbed into venous blood

Pia Mater

• Deep meninx composed of delicate connective tissue that clings tightly to the brain

18. Know the three dural septa (in the powerpoint) and where they are located.

Dura Mater

• Leathery, strong meninx composed of two fibrous connective tissue layers

• The two layers separate in certain areas and form dural sinuses

• Three dural speta extend inward and limit excessive movement of the brain– Falx cerebri—fold that dips into the longitudinal fissure– Falx cerebelli—runs along the vermis of the cerebellum– Tentorium cerebelli—horizontal dural fold extends into

the transverse fissure

19. Know the features of CSF and its functions.

Cerebrospinal Fluid (CSF)

• Watery solution similar in composition to blood plasma

• Forms a liquid cushion that gives buoyancy to the CNS organs

• Prevents the brain from crushing under its own weight

• Protects the CNS from blows and other trauma• Nourishes the brain and carries chemical signals

throughout it • Runs in subarachnoid space

20. List the major regions of the brain (functional areas i.e. cortices, association areas, language areas) and their functions.

Functional areas of the Cerebral Cortex

• The three types of functional areas are:– Motor areas—control voluntary movement• Mostly anterior to central sulcus

– Sensory areas—conscious awareness of sensation• Most posterior to central sulcus

– Association areas—integrate diverse information

Cerebral Cortex: Motor Areas

• Primary (somatic) motor cortex• Premotor cortex• Broca’s area• Frontal eye field

Premotor cortex

• Located anterior to the precentral gyrus• Controls learned, repetitious, or patterned

motor skills• Coordinates simultaneous or sequential

actions• Involved in the planning of movement

Sensory Areas

• Primary somatosensory cortex• Somatosensory association cortex• Visual and auditory areas• Olfactory, gustatory, and vestibular cortices

Somatosensory association cortex

• Located posterior to the primary somatosensory cortex

• Integrates sensory information• Forms comprehensive understanding of the

stimulus (memory of objects)• Determines size, texture, and relationship of

parts• Temperature, pressure, etc.

Visual Areas

• Primary visual (striate) cortex– Seen on the extreme posterior tip of the occipital

lobe– Most of it is buried in the calcarine sulcus– Receives visual information from the retinas

• Visual association area– Surrounds the primary visual cortex– Interprets visual stimuli (e.g., color, form, and

movement)

Auditory Areas

• Primary auditory cortex– Located at the superior margin of the temporal lobe– Receives information related to pitch, rhythm, and

loudness• Auditory association area– Located posterior to the primary auditory cortex– Stores memories of sound and permits perception

of sounds– Wernicke’s area

Association Areas

• Prefrontal cortex• Language areas• Visceral association area

Prefrontal Cortex

• Located in the anterior portion of the frontal lobe

• Involved with intellect, cognition, recall, and personality

• Necessary for judgment, reasoning, persistence, and consciences

• Closely linked to the limbic system (emotional part of the brain)

Language Areas

• Located in a large area surronding the left (or language-dominant) lateral sulcus

• Major parts and functions:– Wernicke’s area—sounding out unfamiliar words– Broca’s area—speech preparation and production– Lateral prefrontal cortex—language

comprehension and word anaylysis– Lateral and ventral temporal lobe—coordinate

auditory and visual aspects of language

Functional areas of cerebral cortex• Motor areas:

– Primary motor and premotor cortices of the frontal lobe– The frontal eye field, and Broca’s area in the frontal lobe of one

hemisphere (usually left)• Sensory areas

– Primary somatosensory cortex and somatosensory association cortex in the parietal lobe

– Visual areas in the occipital lobe– Olfactory and auditory areas in the temporal lobe– Gustatory, visceral, and vestibular areas in the insula

• Association areas– Anterior association areas in the frontal lobe– Posterior and limbic association areas spanning several lobes

21. List the different lobes, gyri, and sulci discussed in class and what each separate or are associated with.

Major Lobes, Gyri, and Sulci of the Cerebral Hemisphere

• Deep sulci divide the hemispheres into five lobes:– Frontal, parietal, temporal, occipital, and insular

• Central sulcus—separates the frontal and parietal lobes– The precentral and postcentral gyri border the central

sulcus• Parieto-occipital sulcus—separates the parietal and

occipital lobes• Lateral sulcus—separates the parietal and temporal

lobes

22. Know the features of the cerebral cortex.

Cerebral Cortex

• The cortex—superficial gray matter; accounts for 40% of the mass of the brain

• It enables sensation, communication, memory, understanding, and voluntary movements

• Each hemisphere acts contralaterally (controls the oppisite side of the body)

• Hemispheres are not equal in function• No functional area acts alone; conscious behavior

involves the entire coretex

23. List the parts to the diencephalon and their functions.

Diencephalon

• Central core of the forebrain• Consists of three paired structures– Thalamus– Hypothalamus– Epithalamiums

• Encloses the third ventricle

Thalamus

• Paired, egg-shaped masses that form the superolateral walls of the third ventricle

• Connected at the midline by the intermediate mass• Contains 4 groups of nuclei—anterior, ventral,

dorsal, and posterior• Nuclei project and receive fibers from the cerebral

cortex• *afferent impulses from all senses and all parts of

the body converge on the thalamus and synapse

Hypothalamus

• Located below the thalamus, it caps the brainstem and forms the inferolateral walls of the third ventricle

• Mammillary bodies– Small, paired nuclei bulging anteriorly from the

hypothalamus– Relay station for olfactory pathways

• Infundibulum—stalk of the hypothalamus; connects to the pituitary gland– Main visceral control center of the body

• homeostasis)

Hypothalamic Function

• Regulates blood pressure, rate and force of heartbeat, digestive tract motility, rate and depth of breathing, and many other viceral activities

• Perception of pleasure, fear, and rage– Close connection w/ limbic system

• Maintains normal body temperature• Regulates feelings of hunger and satiety (satisfaction

*fullness)

• Regulates sleep and the sleep cycle

Endocrine functions of the hypothalamus

• Releasing hormones control secretion of homones by the anterior pituitary gland– GH, TSH, LH, FSH, ACTH

• The supraoptic and paraventricular nuclei produce ADH and oxytocin– Which is released form the posterior pituitary

gland

Epithalamus

• Most dorsal portion of the diencephalon; forms roof of the third ventricle

• Pineal gland—extends from the posterior border and secretes melatonin– Melatonin—hormone involved with sleep

regulation, sleep-wake cycles, and mood• Choroid plexus—a structure that helps form

cerebral spinal fluid (CFS)

24. List the ventricles, their locations, how they are connected, and the source of cerebrospinal fluid in them, its functions, how is it circulated and how frequently is it replaced.

Ventricles of the Brain

• Lateral Ventricles (w/in hemishperes)– Anterior separated by a septum pellucidum

• Interventricular foramen (lateral3rd)• Third Ventricle (w/in diencephalon)• Cerebral Aqueduct – runs through midbrain

(3rd-4th)• Fourth Ventricle (w/in hindbrain dorsal to the

pons)

Ventricles

• Continuous with one another and with central canal of spinal chord

• Hollow chambers filled with CSF and lined by ependymal cells

CSF and Choroid Plexes

– Properties of CSF slide 92.• choroid Plexuses– clusters of capillaries that form tissue fluid filters,

which hang from the roof of each ventricle– Have ion pumps that allow them to alter ion

concentrations of the CSF– Help cleanse CSF by removing wastes

25. Know the parts that make up the brainstem and what cranial nerves (CN) are associated with each along with the functions of each area.

Brain Stem

• Consists of three regions—midbrain, pons, and medulla oblongata

• Similar to spinal cord but contains embedded nuclei• Controls automatic behaviors necessary for survival• Provides the pathway for tracts between higher and

lower brain centers• Associated with 10 of the 12 pairs of cranial nerves

Midbrain Nuclei

• *substantia nigra– Functionally linked to basal nuclei– Contains melanin-precursor to dopamine– Related to Parkinson's

• Red nucleus– Largest nucleus of the reticular formation; red

nuclei are relay nuclei for some descending motor pathways

Pons

• Between midbrain and the medulla oblongata• Forms part of the anterior wall of the 4th ventricle• Fibers of the pons:– Connect higher brain centers and the spinal chord– Pontine nuclei fibers

• Relay impulses between the motor cortex and the cerebellum• Middle cerebellar peduncles

• Origin of cranial nerves V (trigeminal), VI (abducens), and VII (facial)

• Contains nuclei of the reticular formation

Medulla Oblongata

• Most inferior part of the brain stem• Along with the pons, forms the ventral wall of the

fourth ventricle• Contains a choroid plexus of he fourth ventricle• Pyramids-two longitudinal ridges formed by

cortiocospinal tracts• Decussation of the pyramids—crossover points of the

corticospinal tracts• Cranial nerves VII, IX, X, XI, AND XII are associated

with the medulla

Medulla Nuclei

• Cardiovascular control center- adjusts force and rate of heart contraction

• Respiratory centers- control rate and depth of breathing

• Additional centers- regulate vomiting, hiccouping, swallowing, coughing, and sneezing

26. Know the anatomy of the cerebellum and the functions of it.

Anatomy of the Cerebellum

• Two bilaterally symmetrical hemispheres connected medially by the vermis

• Folia- transversely oriented gyri• Each hemisphere has three lobes- anterior,

posterior, and flocculondular• Neural arrangement- gray matter cortex,

internal white matter, scattered nuclei• Arbor vitae—distinctive treelike pattern of the

cerebellar white matter

Cerebellar Processing

• Cerebellum recieves impulses of the intent to initiate voluntary muscle contraction– Proprioceptors and visual signals “inform” the cerebellum

of the body’s position– Cerebellar cortex calculates the best way to perform a

movement– A “blueprint” of coordinated movement is sent to the

cerebral motor cortex and spinal cord neurons• Cognitive function– Recognizes and predicts sequences of events – Word association and puzzle solving