Lecture 15: Nervous System Spinal Cord, Reflexes, Ear

What is described as a slender nerve column that passes downward from the brain into the vertebral canal?

spinal cord

Where does the spinal cord start?

just outside the skull (foramen magnum)

Where does the spinal cord end?

between the 1st and 2nd lumbar vertebrae

Spinal cord consists of ______ segments which gives rise to spinal nerves

31

What can happen if the spinal cord is damaged?

can lead to paralysis

What are the major functions of the spinal cord?

• connects body to brain via nerve impulses

• center for spinal relfexes

What are the tracts of the spinal cord?

1. Ascending tract (spinothalamic)

2. descending tract (corticospinal)

What spinal tract carries sensory information via afferent neurons to the brain?

Ascending tract

What spinal tract is associated with motor impulses from the brain to muscles and glands via efferent neurons?

Descending tract

Ascending tract =

towards brain

Descending tract =

away from brain

What divides the right and left halves of the spinal cord?

anterior median fissure and posterior median sulcus

What does the gray matter part look like?

butterfly core

what are posterior horns?

where afferent (sensory) fibers enter

What are anterior horns?

where efferent (motor) fibers exit

__________ surrounds the gray matter

white matter

On the spinal cord, large wings are which side?

ventral/anterior side

On the spinal cord, small wings are which side?

dorsal side

Label figure 1.

central canal

Label figure 2.

dorsal column

Label figure 3.

dorsal root of spinal nerve

Label figure 4.

dorsal root ganglion

Label figure 5.

spinal nerve

Label figure 6.

ventral root of spinal nerve

Label figure 7.

ventral column

Label figure 8.

anterior median fissure

Label figure 9.

ventral horn

Label figure 10.

lateral horn

Label figure 11.

lateral column

Label figure 12.

gray commissure

Label figure 13.

dorsal horn

Label figure 14.

posterior median sulcus

What is the posterior root of the spinal cord?

where sensory (afferent) fibers enter

What is the anterior root of the spinal cord?

where efferent (motor) fibers exit

What is the tube in the middle of the gray matter that contains cerebrospinal fluid called?

central canal

What is the enlarged area; location of the cell body of sensory neurons called?

dorsal root ganglion

Rapid, automatic, subconscious response to a stimulus causing an ____________________

involuntary reaction

Reflexes are?

“built in” or learned

What kind of pathway does a reflex have?

simple; including a few neurons

What are examples of reflexes?

• patellar reflex (posture)

• withdrawl reflex (protection)

What is the function/importance of reflexes?

• protection

• detects disease or injury (pupil)

• maintaining homeostasis

• check for infant development

What is step one of reflex arc pathway?

stimulus

What is step two of reflex arc pathway?

afferent/sensory neurons carry impulse towards the CNS

What is step three of reflex arc pathway?

enter the dorsal root of spinal cord

What is step four of reflex arc pathway?

enter the dorsal horns of gray matter

What is step five of reflex arc pathway?

exit ventral horn of gray matter

What is step six of reflex arc pathway?

exit ventral root of spinal cord

What is step seven of reflex arc pathway?

response travels via spinal efferent/motor neurons

What is step eight of reflex arc pathway?

effector- reaction of muscle or gland

What are the three parts of the ear?

external, middle and inner

How do organs for hearing work?

sound waves are produced from vibrating objects

The inner ear provides sense of?

equilibrium

What structures are part of the external ear?

1. auricle (pinna)

2. external auditory canal

What structure is outer, funnel-like; directs sound waves into ear; locating direction of sound ?

auricle (pinna)

What structure is a “tube” in temporal bone that carries sound waves inward to the eardrum located in middle ear?

external auditory canal

What structures are part of the middle ear?

1. eardrum/tympanic membrane

2. auditory ossicles

3. eustachian tube

What structure is a semitransparent membrane that vibrates from sound waves; attached to the malleus?

eardrum/tympanic membrane

What is known as the three small bones in the ear that connect vibrations from eardrum to oval window (inner ear); increases (amplifies) the force of vibration?

auditory ossicles

What are the auditory ossicles (list largest to smallest)?

• malleus

• incus

• stapes

What structure connects the middle ear to the throat; helps maintain equal air pressure on both sides of the eardrum; helps drain fluid from middle ear?

eustachian tube

What are the three main parts of the inner ear?

1. cochlea

2. vestibule

3. semicircular canals

What is also known as the “snail shell” organ of hearing?

cochlea

How many chambers does the cochlea have?

3 chambers

What are the chambers of the cochlea?

• cochlear duct (middle)

• scala vestibule (above cochlear duct)

• scala tympani (below cochlear duct)

Where is the organ of corti located?

cochlea → cochlear duct

What occurs in cochlear duct?

• vibrations from stapes cause fluid to vibrate

• hair cells connected to nerves bend causing action potential sent to brain

Label figure 1.

cochlear nerve

Label figure 2.

stapes in oval window

Label figure 3.

round window

Label figure 4.

scala vestibuli

Label figure 5.

scala vestibuli

Label figure 6.

spiral ganglion

Label figure 7.

cochlear nerve fibers

Label figure 8.

scala tympani

Label figure 9.

basilar membrane

Label figure 10.

organ of corti

Label figure 11.

cochlear duct

Label figure 12.

vestibular membrane

What structures work together to maintain balance and equilibrium in ear?

• vestibule

• semicircular canals

What structures are part of vestibule for balance?

• utricle

• saccule

What do the vestibule and semicircular canals have?

fluid and hair cells that move and bend in response to motion

What are the two states of equilibrium?

1. static equilibrium

2. dynamic equilibrium

Which type of equilibrium is associated with sense of position of the head when body isnt moving; maintaining balance relative to the force of gravity?

static equilibrium

The vestibule is associated with which type of equilibrium?

static equilibrium

Which type of equilibrium maintains balance when head and body are in motion; rotational acceleration?

dynamic equilibrium

The semicircular canals are associated with what kind of equilibrium?

dynamic equilibrium