Spinal Cord
Spinal Cord
• It is continuous with the medulla oblongata
• Extends from the foramen magnum of the
occipital bone to the upper boarder of L2
• 2 main Functions:
– Impulse conduction
• Communication to and from the brain through tracts of
white matter
– Reflex integration
• Reflexive movements as opposed to those initiated
voluntarily
• There are 31 pairs of spinal
nerves
– C1-C8
– T1-T12
– L1-L5
– 5 sacral nerves
Gray & White Matter
• Gray Matter:
– Nerve cell bodies,
neuroglia, axon
terminals, and
unmyelinated
association neurons
(interneurons)
• White matter
– Bundles or tracts of
myelinated fibers of
sensory and motor
neurons
Horns
• Ventral Horn
– Cell bodies and dendrites of
the Somatic motor neuron
cell bodies and dendrites
• Dorsal Horn
– Somatic & Autonomic:
sensory axons from the
sensory nerve roots
• Lateral Horn
– Present only in thoracic,
lumbar, and sacral segments
of the cord
– Contain cell bodies of the
autonomic motor neurons
and interneurons
Nervous System
Figure 11.1
Reflex Arc
Spinal cord
(in cross-section)
Stimulus
2 Sensory neuron
1
3 Integration
center
Receptor
4 Motor neuron
Skin
5 Effector
Interneuron
Figure 13.14
• Denticulate ligament
– Formed by lateral
extensions of pia
mater
– Attaches the spinal
cord to the dura
mater
– Anchors spinal cord in
place
Reflexes
• Fast, predictable, automated responses to
changes in the environment
• Somatic reflexes involve contraction of skeletal
muscles
• There are automatic or visceral reflexes which
we are not usually conscious of
Reflex Arc
• Pathway followed by nerve impulses that
produce a reflex
– 5 functional components
1. Sensory receptor
2. Sensory neuron
3. Integrating center (in gray matter where sensory and
motor neuron synapse)
4. Motor neuron
5. Effector (part of body that responds to the motor
impulse
Reflex Arc
Spinal cord
(in cross-section)
Stimulus
2 Sensory neuron
1
3 Integration
center
Receptor
4 Motor neuron
Skin
5 Effector
Interneuron
Figure 13.14
Somatic Reflexes
• Stretch Reflexes
– Involves only two neurons and one synapse
(monosynaptic reflex arc)
– Stretch reflexes can be elicited at the elbow, wrist,
knee and ankle joints
– Examples:
• Patella or knee-jerk reflex
• Achilles or ankle-jerk reflex
– (Dorsiflex the ankle and tap the Achilles tendon
Stretch Reflex
____
Figure 13.17
• Superficial cord reflexes:
– (abdominal, cremaster, and plantar) result from
pain and temperature changes
– Example: Plantar reflex
• Stimulate cutaneous receptors on the sole of the foot
• Babinski’s reflex: damage to pyramidal (corticospinal)
tract
Nervous Physiology Extra Credit
• Complete these activities in lab book (listed in your outline)
Have to answer questions from the activity to get credit
can do all these at home:
– Reaction time from a learned stimulus (with the ruler) p.345
Act.9
– Two-point discrimination p356 Act.2
– Adaptation of touch receptors p.357 Act. 5
– Determination of blind spot p. 371 Act. 5
• From Outline- Write a really short paragraph about what
happened
– “B-r-r-r, That’s Hot”
• 2 points for each assignment completed
Ear
• 2 Important Functions
– Hearing
• The conversion of sounds waves (mechanical and fluid)
into action potentials (electrical)
– Equilibrium
• Ability to subconsciously detect changes in head
position, rotational movement and
acceleration/deceleration
• Reflexes maintain the body in a stable position in spite
of any changes or movements
Ear is divided into 3 regions
• External Ear
– Collect sound waves and channels them
• Middle Ear
– Conveys sound vibration
• Inner Ear
– Labyrinth that houses receptors for hearing and
equilibrium
External Ear
• Pinna or auricle
– Flap of elastic
cartilage
• External auditory
canal (or meatus)
• Ceruminious glands
(blue on model)
– Secrete earwax
(cerumen)
• Tympanic
membrane
(eardrum)
Middle Ear
• Ear Ossicles
– Malleus, Incus, Stapes
– (MAiling, INCludes,
STAmps)
• Auditory tube
(phayngotympanic tubes)
– Duct connecting middle ear
to throat
• Oval Window
– Creates fluid waves within
cochlea
• Round window
– Equalizes pressure created
by vibration of oval window
Inner Ear
• Bony chambers called osseous
or bony labyrinth
– Cochlea (hearing)
– Vestibule (equilibrium)
• Consists of 2 sacs: Utricle &
saccule
– House equilibrium receptor
regions: maculae
– Semicircular canals
(equilibrium)
• Respond to rotational
movement in head
• Ampulla
– Base of semicircular canals
– Houses equilibrium receptor
(crista ampullaris)
Inner Ear
Figure 15.27
Cochlea
• Scala vestibuli
– Provides brain with info
concerning position
• Scala tympani
• Cochlear duct
• Tectorial membrane
– Where hair cells are
embedded
Auditory Transduction Video
• https://www.youtube.com/watch?v=PeTriGTE
Noc