Midterm paper

LAB 2: NERVOUS SYSTEM Protocol slides PCB 3702L FIU

LAB 2 PROTOCOL OBJECTIVES

1. Identify brain structures while performing brain dissection.

2. Explain the mechanism involved and perform pupillary, patellar and ciliospinal reflexes.

3. Explain the mechanism involved and perform smell and taste reflexes.

4. Explain the mechanism involved in balance.

CLINICAL APPLICATION: ENCEPHALITIS

Ø Inflammation of the brain Ø Mostly caused by viral

infections, although it can also result from bacterial, fungal, or autoimmune factors

ENCEPHALITIS

CLINICAL APPLICATION: MENINGITIS

Ø Inflammation of the protective membranes covering the brain and spinal cord

ØUsually caused by a bacterial or viral infection

ØA doctor confirms a diagnosis of bacterial meningitis with a spinal tap, what is the name of the fluid that he draws?

ØCSF!!!

CLINICAL APPLICATION: LUMBAR PUNCTURE

ØA lumbar puncture, also called a spinal tap, is performed in the lower back (lumbar region) and can be done for various reasons

ØMeningitis is often diagnosed using this technique because individuals with meningitis typically exhibit low sugar (glucose) levels, an increased white blood cell count, and elevated protein levels in their CSF

5

PLANES AND SECTIONS ­ Midsagittal Plane: Passes through

the body's midline, dividing it equally into left and right sides.

­ Parasagittal Plane: Splits the body into unequal right and left sides.

­ Frontal/Coronal: Divides the body or structures into front (anterior) and back (posterior).

­ Transverse/Axial: Divides the body or structures into superior (upper) and inferior (lower) portions.

The flow of CSF through the ventricles: Lateral Ventricles à Interventricular Foramen à

Third Ventricle à Aqueduct of Midbrain à Fourth Ventricle

VENTRICLES OF THE BRAIN

HUMAN BRAIN vs. SHEEP BRAIN

8

IDENTIFYING STRUCTURES

9

IDENTIFYING STRUCTURES

10

1 3

4

58

9 10

11

Cerebellum Cerebrum

Corpus Callosum

Septum Pellucidum (Covers Lateral Ventricle)

Thalamus

Midbrain/ Mesencephalon

Medulla Oblongata

Pons

2 Pineal Gland

6

IDENTIFYING STRUCTURES

Ø Arbor Vitae

Fornix

Hypothalamus7

What structures compose the brain stem? • Midbrain • Pons • Medulla Oblongata

How does the location of grey and white matter differ between the brain and spinal cord? • Brain: grey outside/white

inside • Spinal cord: white

outside/grey inside

PATELLAR/KNEE-JERK REFLEX

12

• A monosynaptic reflex commonly used by healthcare professionals to assess the function of the nervous system.

• Elicited by a rubber hammer struck against the patellar ligament. • This will stretch the quadriceps femoris muscle, activating muscle

spindle receptors. The axon from this receptor structure will cause direct contraction of the muscle. A collateral of the muscle spindle fiber will also inhibit the motor neuron of the antagonist muscle, namely the hamstring muscles. The reflex helps to maintain muscles at a constant length.

• Ipsilateral reflex.

•Medical maneuver in which the patient clenches their teeth, flexes both sets of fingers into a hook-like form, and interlocks those sets of fingers together. The tendon below the patient's knee is then struck with a reflex hammer to elicit the patellar reflex

•Do you think this would enhance or diminish the knee-jerk reflex?

JENDRASSIK MANEUVER

REFLEXES OVERVIEW 1. Pupillary Reflex ◦ Shining a bright light to one eye, makes the pupils in both eyes constrict à

Activation of the parasympathetic system ◦ Direct Response: Shining a light in one eye causes a pupil response in that same

eye. ◦ Consensual Response: Shining a light in the left eye causes pupil constriction in the

right eye and vice versa.

2. Patellar Reflex ◦ Striking the patellar tendon under the knee, causes the leg on the ipsilateral

side to jerk and straighten. Reaction tends to be small ◦ Jendrassik maneuver: clasp hands in front of you and try pull them away

from each other ◦ Reaction tends to be more pronounced/enhanced

◦ What muscle(s) do you think contract as a result? Which muscle(s) relax? ◦ Quadricep muscles contract while the hamstring muscles relax

3. Ciliospinal Reflex ◦ Pinching the neck of an individual will cause the pupil on that same side to

dilate à Activation of the sympathetic system ◦ Ipsilateral Response: Results in pupil dilation in the same side that is pinched.

Pupil constriction Pupil dilation

SPECIAL SENSES ACTIVITY – SMELL AND TASTE Tasting jellybeans when:

1. Eyes and nostrils are closed

2. Eyes are closed but nostrils are open

Could the subject(s) taste the jellybean while holding their nose(s)?

• Most likely no.

Was the subject(s) able to taste the jellybean once they regained their sense of

smell?

• Yes (typically).

Why does food often seem tasteless when you have a cold?

• When you have a cold or are suffering from allergies and cannot taste your

food, it is olfaction that is blocked, not gustation.

• About 80% of our perception of taste comes from chemical stimuli of olfactory

cells in the nose; 20% of perceived taste comes from the tongue 15

• Smell is concerned more with detecting the presence or absence of odors than with quantifying their intensity.

• Both smell and taste sensory information is integrated into determining flavor.

SPECIAL SENSES – BALANCE & EQUILIBRIUM The vestibular apparatus/system of the inner ear contains the:

­ The Utricle and saccule which detect gravity and linear acceleration.

­ The semicircular canals which detect rotational movements.

­ Each of the three canals is oriented along one of the 3 dimensions

of the body (the x, y and z axes), so motion in any angular

direction is felt when the fluid inside the canals triggers tiny hairs

on the inside.

How does vision work in concert with the sense of balance?

­ Good balance requires sensory input from: (1) the vestibular

system/apparatus, (2) the visual system, and (3) proprioceptive input

from the muscles, tendons, joints. 16

Spotting is a technique used by ballerinas to prevent dizziness.

BALANCE AND ALCOHOL Can you see why people are asked to walk a straight line to test sobriety?

• Alcohol consumption can lead to changes in the density of the endolymph,

a fluid within the semicircular canals of the inner ear. These density

changes result from alcohol’s ability to dilute bodily fluids, including

endolymph

• Altered endolymph density can disrupt the normal functioning of the

semicircular canals, which are responsible for detecting rotational

movements and changes in head position

• As a consequence of these density changes, the hair cells within the

semicircular canals can bend, sending signals to the brain when the head

is not rotating

• This disruption in the functioning of the inner ear contributes to symptoms

such as dizziness and impaired balance often experienced after alcohol

consumption 17

Spotting is a technique used by ballerinas to prevent dizziness.

18

HYDROCEPHALUS

Subdural Hematoma

CLINICAL APPLICATIONS

Hydrocephalus – Ventricles become enlarged due to CSF buildup, placing extra pressure on the brain and may disrupt the flow of CSF.

Subdural Hematoma – Collection of blood within the subdural space of the brain.

CLINICAL APPLICATION: WERNICKE’S APHASIA

19

• Also referred to as “word salad” • Fluent speech but formed sentences do not make sense

CLINICAL APPLICATION: BROCA’S APHASIA

20

• Expressive Aphasia

• Comprehension of language

remains intact, but these

individuals have difficultly with

communicating efficiently

• Patients get frustrated since they

know what they want to say but

have difficulty doing so