Transcript Abbreviated 11-15

Biology 463 - Neurobiology
Topic 11
The Central Visual System
Lange
The Retinofugal Projection
The retinofugal projection consists of the Optic Nerve, Optic Chiasm, and
Optic Tract
The Retinofugal Projection
• Right and Left Visual Hemifields
– Left hemifield projects to right side of brain and right to the left
Visual deficits from lesions in
the retinofugal projection are
shown in these images.
Notice the specific types of loss shown in
black as compared to the intact fields
Nonthalamic Targets of the Optic Tract are areas that will use visual input
but not in the sense of SEEING OBJECTS.
– Hypothalamus: Biological rhythms, including sleep and
wakefulness
– Pretectum: Size of the pupil; certain types of eye movement
– Superior colliculus: Orients the eyes in response to new stimuli
X
X
X
The Lateral Geniculate Nucleus
(LGN)
The pathways occur in alternating
layers.
Contralateral = on the other side
Ipsilateral = on the same side
Parvocellular Cells
•
•
•
Parvocellular cells, also called P-cells, are neurons located within the
parvocellular layers of the lateral geniculate nucleus (LGN) of the
thalamus.
"Parvus" means "small" in Latin, and the name "parvocellular" refers to
the small size of the cell compared to the larger magnocellular cells.
The parvocellular neurons are sensitive to color, and are more capable
of discriminating fine details than their magnocellular counterparts.
Parvocellular cells have greater spatial resolution, but lower temporal
resolution, than the magnocellular cells.
Magnocellular Cells
•
•
•
Magnocellular neurosecretory cells are large cells within the supraoptic
nucleus and paraventricular nucleus of the hypothalamus.
There are two types of magnocellular neurosecretory cells, oxytocinproducing cells and vasopressin-producing cells, but a small number
can produce both hormones.
These cells are neuroendocrine neurons, they are electrically excitable,
and generate action potentials in response to afferent stimulation.
The Lateral Geniculate Nucleus (LGN)
Inputs Segregated by Eye and Ganglion Cell Type
P type = (also known as beta or midget ganglion cells) are believed to be
responsible for detecting details in vision.
M type = (also known as alpha or parasol ganglion cells) are believed to be
responsible for detecting motion.
nonM-nonP type =are a diverse group of cell types that make up the remaining 5%
of RGCs. Their roles in vision are less understood than M- and P-type ganglion
cells, but it is known that some non-M, non-P type cells are involved in color
vision.
Anatomy of the
Striate Cortex
The calcarine sulcus is
where the primary visual
cortex is concentrated. The
central visual field is located
in posterior portion of the
calcarine sulcus and the
peripheral visual field in the
anterior portion.
Anatomy of the Striate Cortex
Inputs to the Striate Cortex
– First binocular neurons found in striate cortex - most
layer III neurons are binocular (but not layer IV)
END.
Biology 463 - Neurobiology
Topic 12
The Auditory and
Vestibular Systems
Lange
Introduction
Sensory Systems
– Sense of hearing, audition
• Detect sound
• Perceive and interpret nuances
– Sense of balance, vestibular system
• Head and body location
• Head and body movements
The Nature of Sound
Sound
– Audible variations in air pressure
– Sound frequency: Number of cycles per second expressed
in units called hertz (Hz)
– Cycle: Distance between successive compressed patches
The Nature of Sound
Sound
– Range: 20 Hz to 20,000 Hz
– Pitch: High pitch = high frequency; low frequency = low
pitch
– Intensity: High intensity louder than low intensity
The Structure of the Auditory System
The Middle Ear
Components of the Middle Ear
5 – Stapedius muscle
9 – Tensor Tympani muscle
The Middle Ear
• Sound Force Amplification by the Ossicles
– Pressure: Force by surface area
– Greater pressure at oval window than tympanic
membrane, moves fluids
• The Attenuation Reflex
– Response where onset of loud sound causes tensor
tympani and stapedius muscle contraction
– Function: Adapt ear to loud sounds, understand speech
better
The Inner Ear
•
•
•
•
Anatomy of the Cochlea
Perilymph: Fluid in scala vestibuli and scala tympani
Endolymph: Fluid in scala media
Endocochlear potential: Endolymph electric potential 80
mV more positive than perilymph
The Inner Ear
• Physiology of the Cochlea
– Pressure at oval window, pushes perilymph into
scala vestibuli, round window membrane bulges
out
• The Response of Basilar Membrane to Sound
– Structural properties: Wider at apex, stiffness
decreases from base to apex
• Research: Georg von Békésy
– Endolymph movement bends basilar membrane
near base, wave moves towards apex
Georg von Békésy - Hungarian biophysicist born in Budapest.
In 1961, he was awarded the Nobel Prize in Physiology or Medicine for his research
on the function of the cochlea in the mammalian hearing .
The Inner Ear
Travelling wave in the Basilar Membrane
The Inner Ear
The Organ of Corti and Associated Structures
External ear
Tympanic
membrane
Malleus, incus,
stapes
(ossicles)
Internal ear
Oval
window
Fluids in cochlear canals
Upper and middle
Lower
Pressure
Pinna
Air
External
acoustic
meatus
Middle ear
One
vibration
Amplitude
Amplification
in middle ear
Spiral organ
(of Corti)
stimulated
Time
Central Auditory Processes
Auditory Pathway
Mechanisms of Sound Localization
• Techniques for Sound Localization
– Horizontal: Left-right, Vertical: Up-down
• Localization of Sound in Horizontal Plane
– Interaural time delay: Time taken for sound to reach
from ear to ear
– Interaural intensity difference: Sound at high
frequency from one side of ear
Mechanisms of Sound Localization
Interaural time delay and interaural intensity difference
Mechanisms of Sound Localization
The Sensitivity of Binaural Neurons to Sound Location
Mechanisms of Sound Localization
Localization of Sound in Vertical Plane
– Vertical sound localization based on reflections from the
pinna
Auditory Cortex
Primary Auditory Cortex
– Axons leaving MGN project to auditory cortex via
internal capsule in an array
– Structure of A1 and secondary auditory areas:
Similar to corresponding visual cortex areas
The Vestibular System
• Importance of
Vestibular System
– Balance,
equilibrium,
posture, head,
body, eye
movement
• Vestibular Labyrinth
– Otolith organs gravity and tilt
– Semicircular canals
- head rotation
– Use hair cells, like
auditory system, to
detect changes
Figure 15.35: Structure of a macula, p. 594.
Macula of
saccule
Macula of
utricle
Kinocilium
Stereocilia
Otoliths Otolithic
membrane
Hair bundle
Hair cells
Vestibular
nerve fibers
Human Anatomy and Physiology, 7e
by Elaine Marieb & Katja Hoehn
Supporting
cells
Copyright © 2007 Pearson Education, Inc.,
publishing as Benjamin Cummings.
Figure 15.36: The effect of gravitational pull on a macula receptor cell in the utricle, p. 595.
Otolithic
membrane
Kinocilium
Ster eocilia
Depolarization
Hyperpolarization
Receptor
potential
(Hairs bent towar d
kinocilium)
Nerve
impulses
generated in
vestibular fiber
Increased
impulse frequency
Human Anatomy and Physiology, 7e
by Elaine Marieb & Katja Hoehn
Excitation
(Hairs bent away
from kinocilium)
Decreased
impulse frequency
Inhibition
Copyright © 2007 Pearson Education, Inc.,
publishing as Benjamin Cummings.
Figure 15.37: Location and sturcture of a crista ampullaris, p. 596.
Flow of
endolymph
Crista
ampullaris
(a)
Fibers of
vestibular nerve
Cupula
(b)
Turning motion
Cupula
Position
of cupula
during turn
(c)
Human Anatomy and Physiology, 7e
by Elaine Marieb & Katja Hoehn
Increased firing
(d)
Ampulla
of left ear
Ampulla of
right ear
Cupula at rest
Position of cupula
during turn
Fluid motion in
ducts
Horizontal ducts
Decreased firing
Afferent fibers of vestibular nerve
Copyright © 2007 Pearson Education, Inc.,
publishing as Benjamin Cummings.
The Vestibular System
Push-Pull Activation of
Semicircular Canals
– Three semicircular
canals on one side
• Helps sense all
possible headrotation angles
– Each paired with
another on opposite
side of head
– Push-pull
arrangement of
vestibular axons:
The Vestibular System
The Vestibulo-Ocular Reflex (VOR)
•
also known as the oculocephalic reflex
•
a reflex eye movement that stabilizes
images on the retina during head
movement
•
Stabilization occurs by producing an eye
movement in the direction opposite to
head movement, thus preserving the
image on the center of the visual field
END.
Biology 463 - Neurobiology
Topic 13
The Somatic Sensory
System
Lange
Introduction
Somatic Sensation
– Enables body to feel, ache, chill
– Responsible for touch and pain
– Somatic sensory system: Different from other systems
• Receptors: Broadly distributed
• Responds to many kinds of stimuli
Touch
• Types and layers of skin
– Hairy and glabrous (hairless - e.g., palms)
– Epidermis (outer) and dermis (inner)
• Functions of skin
– Protective
– Prevents evaporation of body fluids
– Provides direct contact with world
• Mechanoreceptors
– Most somatosensory receptors are mechanoreceptors
Touch
•
•
•
•
•
•
Mechanoreceptors
Pacinian corpuscles
Ruffini's endings
Meissner's corpuscles
Merkel's disks
Krause end bulbs
Touch
Mechanoreceptors
– Small and large receptive fields
Touch
Mechanoreceptors
– Two-point
discrimination
• Receptive field
density
• Receptive field
size
Touch
Primary Afferent Axons
– Aa, Ab, Ad, C
– C fibers mediate pain and temperature
– Ab mediates touch sensations
Pain Perception
Primary Afferents and Spinal mechanisms
– First pain and second pain
– Referred pain: Angina
Touch
The Spinal cord
– Spinal segments (30)- spinal nerves within 4 divisions of spinal
cord
Touch
The Spinal cord
– Dermatomes- 1-to-1 correspondence with segments
– Shingles
Touch
Dorsal Column–Medial
Lemniscal Pathway
– Touch and
proprioception
Touch
Homuncular Mapping
Figure 12.6a-b: Lobes and fissures of the cerebral hemispheres, p. 435.
Central sulcus
Precentral gyrus
Postcentral gyrus
Parietal lobe
Frontal lobe
Parieto-occipital sulcus
(on medial surface
of hemisphere)
Lateral sulcus
Frontal lobe
Central sulcus
Occipital lobe
Temporal lobe
Transverse
cerebral fissure
Cerebellum
Pons
Medulla oblongata
(a)
Spinal cord
Gyri of insula
Gyrus
Cortex
(gray matter)
Sulcus
Temporal lobe
(pulled down)
(b)
White matter
Fissure
(a deep sulcus)
Human Anatomy and Physiology, 7e
by Elaine Marieb & Katja Hoehn
Copyright © 2007 Pearson Education, Inc.,
publishing as Benjamin Cummings.
Wilder Penfield 1891 – 1976
Physician and Neuroscientist who mapped
the brain in what became the “humunculus”
Figure 12.9: Motor and sensory areas of the cerebral cortex, p. 438.
Sensory
Leg
Motor
Toes
Face
Genitals
Lips
Jaw
Tongue
Swallowing
Human Anatomy and Physiology, 7e
by Elaine Marieb & Katja Hoehn
Motor cortex
(precentral gyrus)
Intraabdominal
Copyright © 2007 Pearson Education, Inc.,
publishing as Benjamin Cummings.
Touch
Homuncular Mapping of a variety of mammals shows differences
in distribution of sensory structures that relate to habitat and
environmental success.
Temperature
Thermoreceptors
– Hot and cold receptors
END.
Biology 463 - Neurobiology
Topic 14
Spinal Control of
Movement
Lange
Introduction
Motor Programs
– Motor system: Muscles and neurons that control muscles
– Role: Generation of coordinated movements
– Parts of motor control
• Spinal cord coordinated muscle contraction
• Brain motor programs in spinal cord
The Somatic & Autonomic Motor Systems
Types of Muscles
– Smooth:
digestive tract,
arteries, related
structures
– Striated:
Cardiac (heart)
– skeletal (bulk of
body muscle
mass)
Lower Motor Neurons
Graded Control of Muscle Contraction by Alpha Motor Neurons
– Varying firing rate of motor neurons
– Recruit additional synergistic motor units
Tetanus – as painted by Sir Charles Bell in 1809.
Lower Motor Neurons
Types of Motor Units
– Red muscle fibers: Large number of
mitochondria and enzymes, slow to contract,
can sustain contraction
– White muscle fibers: Few mitochondria,
anaerobic metabolism, contract and fatigue
rapidly
– Fast motor units: Rapidly fatiguing white
fibers
– Slow motor units: Slowly fatiguing red fibers
Figure 9.7a
Excitation-Contraction Coupling
Muscle Contraction
– Alpha motor neurons
release ACh
– ACh produces large EPSP in
muscle fiber
– EPSP evokes muscle action
potential
– Action potential triggers
Ca2+ release
– Fiber contracts
– Ca2+ reuptake
– Fiber relaxes
Spinal Control of Motor Units
Sensory feedback from muscle spindles - stretch receptor
Spinal Control of Motor Units
The Myotatic Reflex
Spinal Control of Motor Units
Golgi Tendon Organs
– Additional proprioceptive input - acts like strain gauge monitors muscle tension
Spinal Control of Motor Units
Golgi Tendon Organs
– Spindles in parallel with fibers; Golgi tendon organs in
series with fibers
Spinal Control of Motor Units
Excitatory Input
– Crossed-extensor
reflex: Activation
of extensor
muscles and
inhibition of
flexors on
opposite side
Information gleaned about nicotinic ACh
receptors utilzed the electric organs of
electric eels because of their high
concentration of the Ach receptor. The
Disease Myasthenia gravis is an
autoimmune disease where the body's
immune system has damaged receptors on
your muscles causing long term weakness
and eventual, premature death.
Individual showing classic, early signs of
Myasthenia gravis
END.
Biology 463 - Neurobiology
Topic 15
Brain Control of Movement
Lange
George Huntington
James Parkinson
The Cerebellum
Function: Sequence of muscle contractions
Cerebellar lesions
• Ataxia: Uncoordinated and inaccurate movements
• Dysynergia: Decomposition of synergistic multijoint
movements
• Dysmetria: Overshoot or undershoot target
The Planning of Movement by the Cerebral Cortex
Motor Cortex
– Area 4 and area 6 of the frontal lobe
END.