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The Brain & Special Senses (THE SPINAL CORD (The meninges (superficial…
The Brain & Special Senses
BRAIN ANATOMY
Cerebellum
The second largest part of the brain that develops from the metencephalon
Produces fine control over muscular actions and stores memories of movements. maintains equilibrium and posture, as well as receives sensory info. from muscles and joins to regulates the body's position.
Diencephalon
Sandwiched in between the inferior regions of the cerebral hemispheres. Provides relay and switching centers for some sensory and motor pathways, as well as control of visceral activities.
Components include: Epithalamus, thalamus, and hypothalamus.
Epithalamus
:
Partially forms the posterior roof of diencephalon and covers the third ventricle.
Houses the
pineal gland
and the
habenular nuclei
-- Pineal gland is an endocrine gland that secretes melatonin (responsible for circadian rhythm(regulates day-night cycles))
-- Habenular nuclei help relay signals from the limbic system to the midbrain, as well as involved in visceral and emotional responses to odors.
Thalamus
:
The paired oval masses of grey matter that lie on either side of the third ventricle, forming it's superolateral walls.
Is the principal and final relay point for incoming sensory info. that is processed and then projected to the primary somatosensory cortex.
Only a relatively small portion of the sensory info arrives to the thalamus is forwarded to the cerebrum because the thalamus acts as an info. filter.
Hypothalamus
:
Under the anterior region of the diencephalon.
It is a thin, stalklike infundibulum (funnel) extends inferiorly from the hypothalamus to attach to the pituitary gland.
Functions include:
--
Master control of the autonomic nervous system
: it projects descending autonomic nuclei in the inferior brainstem that influences heart rate, blood pressure, digestive activities, and respiration.
--
Master control of the endocrine system
: secretes hormones that control secretory activities in the pituitary gland.
--
Regulation of body temperature
: neurons in the proptic area detect altered blood temps. and signal other hypothalamic nuclei (cool/heat the body)
--
Control emotional behavior
: hypothalamus is located at the center of the limbic system, controlling emotions such as: pleasure, aggression, fear,, rage, contentment, and ex drive.
--
Control food and water intake, as well as regulation of circadian rhythm
Cerebrum
Location of
conscious
thought process and origin of all complex intellectual functions.
It is the center of intelligence, reasoning, sensory perception, thought, memory, and judgement, as well as voluntary motor, visual, and auditory activities.
Broken into a Left and Right cerebral hemisphere, which are held together by the corpus callosum (bundle of axons)
Left is known as the logical side and the right the artistic side.
The left side is where Brocha's area and Wenickie's area are located.
Composed of 5 lobes:
Frontal
: primary motor cortex, premotor cortex, frontal eye field, motor speech (Brocha's area -- left side of brain)
Parietal
: Primary somatosensory cortex, somatosensory assoc. area, Wernicke's area (speech interpretation), snd Gnostic area (understands current activities.
Occipital
: Primary visual cortex, visual assoc. area
Temporal
: primary auditory cortex, auditory assoc. cortex, and primary olfactory cortex
Insula
: primary gustatory cortex
Central sulcus
: separates front (output), from back (input)
Primary motor cortex
: makes muscles move; gyrus infront of CS
Premotor cortex
: helps coordinate muscle movement
Prefrontal cortex
: located behind the forehead. Controls ethics, personality, and behavior.
Brain stem
Connects the cerebrum, cerebellum, and diencephalon to the spinal cord. Primary function is life support.
Three regions that form the brainstem:
midbrain
: superior portion of brain stem.
pons
: bulging region on the anterior part of the brainstem.
-- contains sensory motor tracts that extend through it to connect to the brain and spinal cord.
--connected to the cerebellum by the middle cerebellar peduncles
--houses autonomic nuclei and sensory and motor cranial nerve nuclei (V,VI,VII, and some VIII)
medulla oblongata
: the most caudal (inferior) part of the brainstem and continuos with the spinal cord.
-- contains several autonomic nuclei (cardiac center, vastomotor center, and medullary respiratory center.
THE SPINAL CORD
The meninges (superficial to deep): dura mater, arachnoid, and pia mater
Has both sensory (ascend to brain) and motor pathways (descend from the brain).
May be subdivided into:
Cervical
: superior most part of the spinal cord.
contains neurons whos axons contribute to the cervical and spinal nerves.
Thoracic
: inferior to cervical part, containing the neurons for the thoracic spinal nerves.
Lumbar
: shorter segment of the spinal cord that contains the neurons for the lumbar and spinal nerves.
Sacral
: inferior to lumbar part
Coccygea
l: the most inferior tip, containing the one pair of nerves.
Composed of both grey (neural cells, dendrites, and axon terminals) and white matter (axons and Myelin).
Ventral roo
t: Contains motor axons; incoming neurons; unipolar
Dorsal root
: Sensory axons; outgoing; multipolar
Dorsal root ganglion
: the cell bodies in the bump
There are 31 pairs of spinal nerves connected to the CNS to muscles, glands, and receptors
THE EAR
Inner Ear
The
semicircular canals
are three cavities at right angles to each other that contain sensory cells and fluid. Assoc. structures aid in the sense of equilibrium.
The
Cochlea
is a spiral bony chamber that contains fluid. when this fluid is set in motion by sound waves, it is picked up by the tympanic membrane and transferred via ossicles to the oval window.
The cochlea also houses the
Organ of Corti
. This structure is composed of hair cells that are moved against the overlying membrane as the cochlear fluid is made to vibrate.
-- These hair cell initiate nerve impulses, transmitted via the cochlear branch of the auditory nerve to the temporal lobe (perception)
External Ear
The outermost part of the ear that serves as a funnel for sound is the
pinna
.
The
External auditory canal(meatus)
carries the sound from the pinna to the tympanic membrane.
-- This canal house
ceruminous glands
, that secrete wax, and hairs that serves as protection from foreign particles.
The
tympanic membrane
is set in motion by sound waves.
Middle Ear
Here is where the
ossicles
lie:
Malleus
(hammer) : vibrations form the tympanic membrane causes the malleus to vibrate.
Incus
(anvil): vibrations from the malleus cause the incus to vibrate.
Stapes
(stirrup): vibrations of the incus cause the stapes to vibrate and press against the oval window.
The
oval window
is a membrane covered opening into the inner ear. Vibrations of the membrane cause waves in the fluid of the inner ear.
Waves of the inner ear fluid press against the
round window
causing it to bulge into the middle ear cavity.
The
eustachian tube
connects the middle ear with the nasopharynx of the throat, equalizing the air pressure on the two sides of the tympanic membrane.
-- This is where infections may travel through
THE EYE
Three layers of the eye: (Superficial to deep)
Sclera
: this is the white and the outermost layer that serves as protection and maintenance of shape. The
cornea
, through which light enters, lies anteriorly.
Choroid
: the dark middle layer that absorbs light to prevent reflection.
Retina
: Translucent inner layer, which contains the photoreceptors (pigment molecules;rods and cones) and the
fovea centralis
(small pit).
--
Rods
function in dim light; located away form fovea centralis
--
Cones
function in bright light and help in color vision; conc. in fovea centralis.
-- Medial to fovea centralis is the
blind spot
.
Between the cornea and iris is the
anterior chamber
, which contains aqueous humor, thus nourishes and maintains the shape of the front of the eye.
The
iris
is the colored part of the eye. The
pupil
is the opening of the cavity which responds to light (gets bigger in dim light)
Thus, light goes through the pupil of the iris.
Behind the iris is the
lens
, which focuses light on the retina. It is held in place by
suspensory ligaments
that extend from the
ciliary body
, which is a muscular ring for changing the shape of the lens.
There is also a posterior cavity that houses the vitreous humor (viscous fluid), which maintains the shape of the eye and supports the internal parts.
