Nervous system Part 2 Flashcards
What are the four main divisions of the brain?
the cerebrum, cerebellum, brainstem, diencephalon
What are the protective structures of the brain and why is it important to have those protections?
Meneges, cerebrospinal fluid, the skull, and blood brain barrier.
Nervous tissue is damaged by even the slightest pressure, and can not regenerate once damaged.
Ventricles
The brain has 4 ventricles
These are cavities in the brain that are filled with cerebrospinal fluid.
Two lateral ventricles, third and fourth ventricle
Where does the 4th ventricle drain?
into the central canal of the spinal cord, which also has cerebrospinal fluid.
meninges
Three layers of connective tissue membranes that cover and protect the CNS organs and enclose the cerebrospinal fluid.
Three layers of the meninges
Dura mater (outer menix)
arachnoid (middle menix)
pia mater (inner menix)
Dura mater
leathery double-layer outer menix
arachnoid menix
a loose layer seperated from the dura mater by the subdural space (middle menix)
**beneath the arachnoid menix is the subarachnoid space.
subarachnoid space
beneath the arachnid menix
contains blood vessels and is filled with cerebrospinal fluid
Pia mater
inner menix - thin connective tissue tissue tightly attached to the brain.
Cerebrospinal Fluid
a special fluid formed in the walls of ventricles from blood plasma by permeating the choroid plexus
choroid plexus
formed by a network of blood vessels and within the ventricles
CSF that is made in the walls of the ventricals by blood plasma permeates the choroid plexus
CSF circulates through the ventricles and into the mengines.
Cerebrospinal fluid
circulates through the ventricles into the meninges
cushions the brain and spinal cord by providing buoyancy allowing the brain to float
Blood brain barrier
a diffusion barrier that prevents most particles from entering the system tissue
this keeps the brain and spinal cord separate from general blood circulation
formed by glial cells- astrocytes
astrocytes
glial cell
blood brain barrier is formed by relatively impermeable brain capillaries, due to astrocytes
this barrier provides a stable chemical environment for the neurons
why is a stable chemical environment important in the brain?
to protect neurons from chemical variations that could cause uncontrollable firing of neurons
cerebrum
foremost part of brain
largest part of brain -83% of brain mass
contains 2 large masses - left and right cerebral hemispheres
median longitudinal fissure
separates the right and left cerebral hemispheres
The right cerebral hemisphere controls the left side of the body and the right cerebral hemisphere control the left side of the body
gyri
the cerebral cortex has raised ridges of tissue called gyri (like mountains)
sulci separate the gyri -these are shallow grooves (valley in between the mountain)
transverse fissure
separates the cerebrum from the cerebellum
corpus callosum
a bridge of white nerve fibers called corpus callosum that connects the cerebral hemispheres
cerebral cortex
outer portion of cerebral hemispheres that is highly convoluted and gray in color
Frontal lobe
controls higher levels of executive functions such as reasoning and decision making
controls motor function
permits control over voluntary muscle actions
parietal lobe
receives sensory information from receptors in the mouth for taste and located in the skin, such as those for touch, pressure, pain
occipital lobe
interprets visual imput
temporal lobe
has sensory areas for hearing and smelling
Primary areas of cerebral cortex
in each lobe receive or send information for one type of sensory or motor information
association areas of cerebral cortex
mainly work to integrate more than one type of sensory information for purposeful action- ex. primary motor cortex in the frontal lobe
primary motor cortex
controls voluntary motor movements for all parts of the body
primary sensory cortex
receives all direct sensory imput from the body
also called post central gyrus or somatosensory cortex
What do all four lobes have?
association areas which receives information from other lobes and integrates it to higher, more complex levels of consciousness
ex. artist abilities, learning, memory intellect
Broca’s area
located in the frontal lobe and is responsible for speech production
Wernicke’s area
located in the temporal lobe and is responsible for speech comprehension
consciousness
the cerebrum is responsible for consciousness - a state of being aware and awake to a person’s surroundings
Cerebrum
portion of the brain that governs higher thinking, intelligence, reasoning
controls activités of lower parts of the brain including the brain stem, diencephalon, limbic system and cerebellum
can override the functioning of lower parts of the brain (ex. when a person uses meditation to reduce a high heart rate.
how does the cerebrum initiate voluntary control?
by acting on sensory input via the thalamus
brainstem
the medulla oblongata, midbrain, pons are in the midbrain
medulla oblongata
lies between the spinal cord and pons and anterior to the cerebellum.
contains vital centers for regulating heartbeat, breathing and vasoconstriction(blood pressure)
also has a reflex centers for vomiting, coughing, sneezing, hiccuping and swallowing
vasoconstriction
constriction of the blood vessels involved in regulation of blood pressure
Tracts in the medulla
the medulla has tracts that descend or ascend between the spinal cord and brain’s higher centers
The pons
contains bundles of axons traveling between the cerebellum and the rest of the CNS
The pons functions with the medulla to regulate breathing rate
has reflexes that deal with head movement in response to visual and auditory stimuli
midbrain
acts as a relay station for tracts passing between the cerebrum and spinal cord or cerebellum
what reflexes does the midbrain have?
reflex centers for higher level reflexes for involving visual, auditory, and tactile responses
superior and inferior colliculi
located in the posterior region of the midbrain - these regions control reflexes for the head and neck in response to sudden visual or auditory responses
spinal cord
extends from the brainstem to first lumbar vertebrae where it terminates at the conus medullaris
conus medullaris
where the spinal cord terminates
cauda equina
an extention of the cord beyond L1 that is a collection of nerve roots which ends at the coccyx
the spinal cord and the caudal equina are how all electrical impulses travel between the brain and the rest of the body
protection of the spinal cord
like the brain the spinal cord is protected by three things:
vertebrae, cerebrospinal fluid, and meninges - these are continuous from the brain
spinal dura mater
the spinal cord has a single layer of sheath called spinal dura mater that
it is separated from the the vertebral column by a cushioning fat- filled space called epidural space
epidural space
a fat filled space that separated the vertebral column from the spinal dura mater
filum terminale
an extension of Pia mater in the spinal cord that runs from the conus medullaris to the coccyx where it provides an anchor for the spinal cord
** the space between the middle arachnoid and inner pia is filled with CSF
spinal tap
the CSF filled subarachnoid space inferior to the end of the spinal cord at L1 is the location for a spinal tap - this a removal of CSF for testing/diagnostics
This region is chosen because there is less risk to damaging the spinal cord from the insertion of the long needle
two grooves of the spinal cord
anterior median fissure and shallower posterior median sulcus
central canal
the opening in the spinal cord that runs the entire length and is filled with CSF
white matter
is composed of myelinated and unmyelinated nerve fibers organized into regions called columns
tract
a bundle of axon in the CNS
ALL the tracts cross over to the opposite side in the spinal cord - this makes the left brain control the right side and the right side to control the left
ascending tracts
the white matter fibers of the spinal cord are mostly composed of ascending tracts
these proceed up to the brain to carrying sensory input
descending tracts
proceed down or within the cord carrying motor outputs with a few commissural tracts across the cord (these allow for communication between the right and left sides)
dorsal root
of the spinal cord carries incoming afferent/sensory neurons
dorsal root ganglion
contains the cell bodies of the afferent neurons from the dorsal root
ventral root
contains the axons of motor neurons
spinal nerve
the dorsal and ventral roots on each side of the spinal cord come together to form a spinal nerve
gray matter
of the cord is composed of a mixture of cell bodies of neurons
the grey matter is organized into regions called horns
there are two posterior dorsal horns and two anterior ventral horns
gray commissure
the small anterior horns are connected by a cross bar called the gray commissure
anterior ventral horns
contain somatic motor neurons whose axons serve as efferent pathways to skeletal muscles by way of the ventral roots of the spinal cord
SOMATIC motor neurons
posterior (dorsal) horns
serve as one of the afferent pathways from receptors by way of the dorsal roots of the spinal cord
lateral horns
of the gray matter are primarily located at the thoracic level of the spinal cord
these contain automatic sympathetic motor neurons whose axons serve as an efferent pathways to visceral organs
Where do the efferent pathways exit
the ventral roots of the spinal cord along with those of the somatic motor neurons
peripheral nervous system
lies outside the CNS
made up of nerves that are apart of the somatic or automatic system
somatic nervous system
somatic system contains nerves that control the skeletal muscles, skin, and joints
includes all the nerves the serve the muscular skeletal system and exterior sense organs, including the skin
exterior sense organs, including ones embedded in the skin, are receptors
receptors
receive environment stimuli and then initiate nerve impulses towards the CNS