What two structures make up the CNS?

Brain and Spinal Cord

Describe the roles of the three types of neurons in the spinal cord (sensory, motor, and interneuron). SENSORY

Sensory Neuron-

–about 10 million

–deliver information to CNS

Describe the roles of the three types of neurons in the spinal cord (sensory, motor, and interneuron). MOTOR

Motor Neuron-

–about 1/2 million

–deliver commands to peripheral effectors

Describe the roles of the three types of neurons in the spinal cord (sensory, motor, and interneuron). INTERNEURON

Interneuron-

(AKA - association neurons)

–about 20 billion

–interpret, plan, and coordinate signals in and out

Draw AND label (including the functions of the regions that you label) of a spinal cord cross section.

Diagram AND label the five steps that occur in a neural reflex. Make sure to keep the sensory and motor neurons straight!

Compare and contrast innate and acquired reflexes.

Innate reflexes:

• basic neural reflexes
• formed before birth

Acquired reflexes:

• rapid, automatic
• learned motor patterns

Compare and contrast somatic and visceral reflexes.

Somatic reflexes:

• involuntary control of nervous system

–superficial reflexes of skin, mucous membranes

–stretch reflexes (deep tendon reflexes) e.g., patellar reflex

Visceral reflexes (autonomic reflexes):

• control systems other than muscular system

Compare and contrast monosynaptic and polysynaptic reflexes.

–monosynaptic - sensory neuron synapses directly onto motor neuron

–polysynaptic - at least 1 interneuron between sensory neuron and motor neuron

Compare and contrast spinal reflexes and cranial reflexes.

–spinal reflexes:

• occurs in spinal cord

–cranial reflexes:

• occurs in brain

Diagram AND label a monosynaptic spinal reflex, using the stretch reflex as an example

Have least delay between sensory input and motor output:–i.e. patellar reflex)

Brain cannot override the reflex

Completed in 20–40 msec

Explain the roles of intrafusal and extrafusal muscle fibers in the stretch reflex as well as the adjustment of muscles tension in postural reflexes

Bundles of small, specialized intrafusal muscle fibers:

–innervated by sensory and motor neurons

Surrounded by extrafusal muscle fibers:

–which maintain tone and contract muscle

Get acquainted with some of the common clinical tendon reflexes (as you will be testing these in your patients!)

Diagram AND explain the events that occur during the flexor reflex. Make sure to include that little interneuron!

Explain the importance of reciprocal inhibition. Give an example!

For Stretch R eflex or the F lexor R eflex to work:

–the stretch reflex of antagonistic (extensor) muscle must be inhibited (reciprocal inhibition) by interneurons in spinal cord

Diagram AND label the events which occur during the tendon reflex. What would happen to us if we didn’t have this reflex?

What would happen to us if we didn't have the tendon reflex?

If we did not have the tendon reflex then we would not be preventing skeletal muscles from developing too much tension, tearing or breaking tendons

What does ipsilateral mean? How about contralateral?

Ipsilateral reflex arcs:

–occur on same side of body as stimulus

–stretch, tendon, and withdrawal reflexes

Crossed extensor reflexes:

–involves a contralateral reflex arc

–occurs on side opposite stimulus

Now that you know what ipsilateral and contralateral mean, diagram an example of the crossed extensor reflex.

Polysynaptic Spinal Reflexes - The Crossed Extensor Reflex

Occur simultaneously, coordinated with flexor reflex

e.g., flexor reflex causes leg to pull up:

crossed extensor reflex straightens other leg

to receive body weight

Review the meanings of rostral and caudal.

Areas of the brain:

Rostral (toward forehead)

Caudal (toward cord)

What region comprises the bulk of the volume of the human brain?

–cerebrum is 83% of brain volume; cerebellum contains 50% of the neurons

Explain the difference between a gyrus and a sulcus.

–Gyri = folds; mountain

–Sulci = grooves; valley

What is a fissure in the brain?

Divides cerebral hemispheres

Explain the difference between nuclei and tracts in the brain

Nuclei = deeper masses of gray matter

Tracts = bundles of axons (white matter)

Compare and contrast grey and white matter in the brain.

Gray matter = neuron cell bodies, dendrites, and synapses

–forms cortex over cerebrum and cerebellum

–forms nuclei deep within brain

White matter = bundles of axons

–forms tracts that connect parts of brain

List the three meninges and the two spaces. Which of these three is located deepest (closest to the brain)?

Three Meninges:

Dura Mater- outermost layer- contains the Subdural space

Arachnoid Layer-contains the subarachnoid space

Pia mater-***deepest layer

Two Spaces:

Subdural Space

Subarachnoid space

Under which layer of the brain does CSF circulate?

–from choroid plexus

–through ventricles

–to central canal of spinal cord

–into subarachnoid space around the brain, spinal cord, and cauda equina

Meninges of the Brain

Under which of the layers in the brain are the dural sinuses located?

Dura mater

Where would a subdural hematoma occur if someone got hit in the head?

A subdural hematoma would occur in the space between the dural mater and middle layer of the meninges.

Describe the pathophysiology of meningitis? Make sure to include where you would insert a needle during a spinal tap.

• Inflammation of the meninges
• Usually a disease of infancy and childhood - between 3 months and 2 years of age
• Bacterial and virus invasion of the CNS by way of the nose and throat
• Signs include high fever, stiff neck, drowsiness and intense headache and may progress to coma
• Diagnose by examining the CSF

–lumbar puncture (spinal tap)

Label the locations of the following ventricles:

1. Lateral ventricle
2. Third Ventricle
3. Fourth Ventrilce

What two ventricles of the brain do each of the following connect:

1. Interventricular foramen
2. Cerebral aqueduct

Interventricular foramen- connects to LV and 3rdV

Cerebral aqueduct- connects to 3rd and 4th Ventricle

Predict the effects if either the interventricular foramen or the cerebral aqueduct were to become occluded.

Brain damage from build up of CSF.

– hydrocephalus

• Enlargement of the head in babies and brain damage in adults

Where is cerebrospinal fluid made, how is it circulated, and what is its purpose in the CNS? Spend some time looking at the choroid plexus!

Formed by the choroid plexus

CIRCULATES through ventricles, to central canal of spinal cord, into subarachnoid space around the brain, spinal cord, and cauda equina

Functions:

–Forms cushion for brain and other CNS organs

–Gives buoyancy to brain (which reduces weight by 97%) to prevent brain from crushing under own weight

Transports nutrients, chemical messengers, and waste

Explain the role of arachnoid villi and arachnoid granulations on the circulation of CSF.

Arachnoid villi:

–extensions of subarachnoid space

–extend through dura mater to superior sagittal sinus

Arachnoid granulations:

–large clusters of villi

–absorb CSF into venous circulation

What causes hydrocephalus?

When CSF becomes obstructed

Compare and contrast the structures involved AND the functions of both blood brain barrier and the blood CSF barrier.

BLOOD BRAIN BARRIER

BLOOD BRAIN BARRIER-

Structure: Endothelial cells stitched together by tight junctions

Very effectively protects the brain from many common bacterial infections. Thus, infections of the brain are very rare. ***ASTROCYTES

Compare and contrast the structures involved AND the functions of both blood brain barrier and the blood CSF barrier.

BLOOD CSF BARRIER

BLOOD CSF BARRIER- barrier at choroid plexus are ependymal cells joined by tight junctions

Function: Acts as barrier and produces CSF

Which portions of the brain make up the brain stem?

–Midbrain

–Pons

–Medulla oblongata

The midbrain is responsible for which functions?

Coordinates head and eye movement when we visually follow a moving object or see something out of corner of eye, even when we are not conscious of it

Coordinates head reflex movement to unexpected auditory stimulus – startle reflex

What is the major function of the pons?

Helps to maintain normal rhythm of breathing

Which portion of the brain stem adjusts the force and rate of heartbeat, vomiting, sneezing, etc?

Medulla Oblaganta

Which major region of the brain coordinates skeletal muscle contractions needed for smooth, coordinated movements of our daily lives?

Cerebellum

List the three bilaterally symmetric structures of the diencephalon.

–Thalamus

–Hypothalamus

–Epithalamus

List the three bilaterally symmetric structures of the diencephalon.

Which of these three makes up the major portion of the diencephalon?

The thalamus makes up 80% of the diencephalon

List the three bilaterally symmetric structures of the diencephalon.

Which of these three regulates hunger and fullness?

Hypothalamus

List the three bilaterally symmetric structures of the diencephalon.

Which portion serves as a gateway between the cerebral cortex and the rest of the body (where a sorting out and “editing” process occurs)?

Thalamus

List the three bilaterally symmetric structures of the diencephalon.

Which portion of the diencephalon is responsible for regulation body temperature (and does so by initiating sweating or shivering)?

Hypothalamus

List the three bilaterally symmetric structures of the diencephalon.

Which portion contains the gland responsible for the sleep/wake cycle?

Epithalamus

What are some of the structures that comprise the "limbic" system, and where in the brain are they located? What are the general functions of the limbic system?

Hippocampus –organizes sensory and cognitive information into a new memory

Amygdala- emotional memory

They are located in the cerebral hemispheres and diencephalon.

Describe the role of the basal ganglia, using Parkinson’s disease to aid in your explanation. Be specific!

With Parkinson's Disease, an inhibition of dopamine produces a balanced, restrained output of muscle-regulating signals from the basal nuclei. However with PD, neurons leading from the substantia nigra degenerate and thus do not release normal amounts of dopamine. Without the dopamine the excitatory effects of acetylcholine are not restrained, and the basal nuclei produce an excess of signals that affect voluntary muscles in several areas of the body. Overstimulation of these muscles cause rigidity and tremors of the head and limbs; an abnormal, shuffling gait: absence of relaxed arm-swinging while walking; and a forward tilting of the trunk.

What are some of the functions of the reticular formation. Make sure to describe the different “types” of sleep.

Normal Sleep: decreased activity of Ret. Form. = decreased cerebral cortex activity

Paradoxical Sleep (REM: dream sleep): impulses received by some parts of the brain but not by others.

Comatose: Ret. Form. ceases to function – cerebral cortex can’t be aroused

Compare the roles of association fibers, commissural fibers, and projection fibers of white matter. Association Fibers

Fibers that connect areas of the cerebral cortex within the SAME hemispheres of the cerebral cortex

Compare the roles of association fibers, commissural fibers, and projection fibers of white matter. Commissural Fibers

Fibers that connect one cerebral hemisphere to the other

Compare the roles of association fibers, commissural fibers, and projection fibers of white matter. Projection Fibers

Fibers that connect the cerebrum and other parts of that brain and/or spinal cord

The cerebrum is also called the

The cerebral cortex

Where is the corpus callosum located, and what is its primary function?

Corpus Callosum is a major pathway between the hemispheres.

Aids communication between cerebral areas and between cerebral cortex and CNS

The gray matter makes up which portion of the cerebrum? The white matter makes up which portion of the cerebrum?

The gray matter makes up the outer portion of the cerebrum and the white matter makes up the inner portion of the cerebrum

Locate the following of the cerebrum:

1. Longitudinal fissure
2. Central sulcus
3. Precentral gyrus
4. Postcentral gyrus

Longitudinal fissure

List the four major lobes of the cerebrum AND the main functions of each lobe.

Frontal Lobe

–voluntary motor functions

–planning, mood, smell and social judgment

Parietal Lobe

–receives and integrates sensory information

Occipital Lobe

–visual center of brain

Temporal Lobe

–areas for hearing, smell, learning, memory, emotional behavior

Describe the location AND functions of the sensory association areas of the cerebrum.

Interpret sensory information

Somesthetic association area (parietal lobe)

–position of limbs; location of touch or pain; shape, weight and texture of an object

Visual association area (occipital lobe)

–identify things we see

–faces recognized in temporal lobe

Auditory association area (temporal lobe)

–recall the name of a piece of music or identify a person by his voice

Describe the location AND functions of the area(s) of the cerebrum involved in motor control.

Intention to contract a muscle begins in motor association (premotor) area of frontal lobes

Precentral gyrus (primary motor area) relays signals to spinal cord

–pyramidal cells called upper motor neurons

–supply muscles of contralateral side

What does contralateral motor control refer to? Make sure to explain what decussate means!

Right hemisphere controls left side of body

Left hemisphere controls right side

Decussate is a crossing in the medulla

Why are the face and hands represented by such a large region of the cerebral cortex?

lots of sensations needed so they have larger area in cerebral cortex

Compare and contrast the locations AND functions of Wernicke and Broca’s area in the cerebral cortex.

Wernicke area posterior

–permits recognition of spoken and written language and creates plan of speech (sensory speech)

Broca area anterior

–generates motor signals for larynx, tongue, cheeks and lips

–transmits to primary motor cortex for action (Motor speech)

List AND describe the three types of aphasias covered in class. Lesion to Broca

Lesion to Broca = nonfluent aphasia

–slow speech, difficulty in choosing words

List AND describe the three types of aphasias covered in class. Lesion to Wernicke

Lesion to Wernicke = fluent aphasia

–speech normal and excessive, but makes little sense

List AND describe the three types of aphasias covered in class. Anomic aphasia

Anomic aphasia

–speech and understanding are normal but text and pictures make no sense

What is a lobotomy?

a surgical operation involving incision into the prefrontal lobe of the brain

Describe, in detail, the concept of lateralization.

Left hemisphere - categorical hemisphere

–specialized for spoken and written language, sequential and analytical reasoning (math and science), analyze data in linear way

Right hemisphere - representational hemisphere

–perceives information more holistically, perception of spatial relationships, pattern, comparison of special senses, imagination and insight, music and artistic skill

Highly correlated with handedness

–91% of people right-handed are left side dominant

Lateralization develops with age

females have more communication between hemispheres (corpus callosum thicker posteriorly)

MEMORIZE the names, numbers, functions, and whether or not each cranial nerve is sensory, motor, or both! You will thank me later for this, even though it seems like a pain in the rear right now! J

Making Separate Cards.

Predict what effects damage to each of the cranial nerves might cause. For example, a person will have trouble moving their right eye in which directions if the Oculomotor Nerve (CN III) is damaged.

Come Back *****

Use the idea of two point discrimination to explain what a receptive field is.

Area is monitored by a single receptor cell

The larger the receptive field, the more difficult it is to localize a stimulus

So, when you use the two point pair of blunt dividers, the minimum point to where they can feel both points at the same time then that is where you can locate the nerve densities. Therefore, the further apart the dividers are the more difficult it is to localize a stimulus.

Compare and contrast tonic and phasic receptors. Draw a couple of graphs!

Tonic

–Are always active

Phasic

–Are normally inactive

–Become active for a short time whenever a change occurs

–Provide information about the intensity and rate of change of a stimulus

Use a graph to explain the concept of adaptation.

Pain receptors =

AKA nociceptors

Where are pain receptors found?

Are common in the:

–superficial portions of the skin

–joint capsules

–within the periostea of bones

–around the walls of blood vessels

Free nerve endings with large receptive fields

What are the two types of pain receptor fibers and what types of information do each of them carry?

Myelinated Type A Pain Fibers- Carry sensations of fast pain, or prickling pain, such as that caused by an injection or a deep cut

Type C Pain Fibers- Carry sensations of slow pain, or burning and aching pain

Where might one find thermoreceptors?

Are free nerve endings located in:

–the dermis

–skeletal muscles

–the liver

–the hypothalamus

Compare and contrast, in detail, the three classes of mechanoreceptors. Tactile receptors

Tactile receptors:

–provide the sensations of touch, pressure, and vibration

Compare and contrast, in detail, the three classes of mechanoreceptors. Baroreceptors

Baroreceptors:

–detect pressure changes in the walls of blood vessels and in portions of the digestive, reproductive, and urinary tracts

Monitor change in pressure

Consist of free nerve endings that branch within elastic tissues in wall of distensible organ (such as a blood vessel)

Compare and contrast, in detail, the three classes of mechanoreceptors. Proprioceptors

Proprioceptors:

–monitor the positions of joints and muscles

–the most structurally and functionally complex of general sensory receptors

Muscle spindles: monitor skeletal muscle length, trigger stretch reflexes

Golgi tendon organs: located at the junction between skeletal muscle and its tendon, stimulated by tension in tendon, monitor external tension developed during muscle contraction

Receptors in joint capsules: free nerve endings detect pressure, tension, and movement at the joint

Where might you find chemoreceptors? Briefly, how do they work

Located in the:

–carotid bodies:

–near the origin of the internal carotid arteries on each side of the neck

Aortic bodies:

–between the major branches of the aortic arch

–Receptors monitor Ph, carbon dioxide, and oxygen levels in arterial blood

Describe the difference in terms of location AND function of white matter and gray matter in the spinal cord.

Exterior white mater – conduction tracts

Internal gray matter - mostly cell bodies

Compare and contrast the dorsal and ventral horns of the spinal cord.

Dorsal (posterior) horns – SENSORY NEURONS!

Ventral (anterior) horns – MOTOR NEURONS!

Compare and contrast afferent and efferent neurons. Afferent

The Afferent (sensory) nervous system is all of the nerve pathways carrying signals TO the brain and/or spinal cord.

Carries toward the central nervous system.

Compare and contrast afferent and efferent neurons. Efferent

The Efferent (motor) nervous system consists of all the nerve pathways carrying signals OUT of the brain and/or spinal cord.

Carries away from the central nervous system

Draw out, in detail, the following SENSORY pathways from the spinal cord to the brain, making sure to include what type of information is relayed in each pathway:

1. Posterior columns
2. Anterior spinothalamic tract
3. Lateral spinothalamic tract
4. Spinocerebellar tract

Sensory pathway- Posterior column

Carries sensations pressure, vibration, and proprioception

Sensory pathway- Anterior spinothalamic tract

Carries crude touch and pressure sensations

Sensory pathway- Lateral spinothalamic tract

Carries pain and temperature sensations

Sensory pathway- Spinocerebellar tract

conveys information to the cerebellum about limb and joint position

Diagram AND explain the differences between upper and lower motor neurons.

Upper motor neuron:

cell body lies in a CNS processing center (i.e. cerebral cortex)

• Synapses on the lower motor neuron
• Innervates a single motor unit in a skeletal muscle:

activity in upper motor neuron may facilitate or inhibit lower motor neuron

Lower motor neuron:

cell body lies in a nucleus of the brain stem or spinal cord

• Triggers a contraction in innervated muscle:

–only axon of lower motor neuron extends outside CNS

–destruction of or damage to lower motor neuron eliminates voluntary and reflex control over innervated motor unit

Where do most motor fibers decussate as they descend?

Medulla Oblaganta

Draw out the following MOTOR pathways from the brain to the spinal cord, making sure to include what type of information is relayed in each pathway:

Draw out the following MOTOR pathways from the brain to the spinal cord, making sure to include what type of information is relayed in each pathway: Lateral corticospinal tract

***Lateral c orticospinal tracts (to skeletal muscles of trunk and limbs)

Draw out the following MOTOR pathways from the brain to the spinal cord, making sure to include what type of information is relayed in each pathway: Anterior corticospinal tract

Draw out the following MOTOR pathways from the brain to the spinal cord, making sure to include what type of information is relayed in each pathway: Corticobulbar tract

What are the “pyrmids” in the medulla of the brainstem?

As they descend, corticospinal tracts are visible along the ventral surface of medulla oblongata as pair of thick bands, the pyramids

Predict the effects of an upper vs. a lower motor neuron lesion in the lateral corticopsinal tract.

Briefly describe the components and functions of the medial and lateral pathways.

a. Medial Pathway Components - Primarily concerned with control of muscle tone and gross movements of neck, trunk, and proximal limb muscles
b. Lateral Pathway Components - Primarily concerned with control of muscle tone and more precise movements of distal parts of limbs