Nervous System 2 Flashcards
What 3 major portions can the brain be divided into?
- Cerebrum
- Cerebellum
- Brainstem
What is brain size proportional to?
Body size only and can be divided into three major portions
Cerebrum appearance
- 83% of brain volume
- consists of 2 cerebral hemispheres
- divided into multiple lobes each marked by gyri and sulcus
Sulcus
shallow groves (slits)
Fissure
DEEP groves (deep slits)
Gyrus
Convolutions (ridges that stick out)
Longitudinal fissure
Separates the left and right hemispheres, although they remain connected through the corpus callosum
Central sulcus
Separate front and back of cerebrum
Cerebellum location
Lies inferior and posterior to the cerebrum; more delicate surface markings
(Below and to the back of cerebrum)
Brainstem parts
Base of brain Thalamus Hypothalamus Midbrain (top of brains stem/middle of brain) Pons (bump) Medulla oblongata (slight bump)
Cerebrospinal fluid location
Make in ventricles (lined with epithelium- ependemial cells)
-fills 4 hollow spaces in brain
Gray matter
Consisting of non-myelinated soma and dendrites
White matter
Myelinate nerve fibers (myelin is on axon)
**Location of gray matter in brain and spinal cord
Gray matter forms outer cortex* in brain, but is an inner core* in the spinal cord
White matter location in brain and spinal cord
White matter is inside brain and outside spinal cord
Meningitis
Very courageous and very deadly inflammation/infection in brain. Perform spinal tap to detect
Meninges
(Singular=meninx)
3 protective fibrous coverings that separate the brain and spinal cord from the skull and vertebrae
What separates brain and spinal cord from the skull and vertebrae
Meninges
Dura mater
Outermost meninx, really rough, consists of a periosteal layer and an inner meningeal layer
What part of and what does the dura mater form within the vertebral canal?
The meningeal layer (inner layer of dura mater) forms a dural sheath
Dural sheath
Same thing as the meningeal layer (inner layer) of the dura mater just the name for when it’s in the vertebral canal!
Epidural space location
Between the dural sheath and surrounding bone
Space is between the skull and the dura mater
Arachnoid mater
The second meninx that adheres to the dura and sends spider like extensions out to the #3 pia mater (highly vascular)
3 pia mater
Highly vascular, closely follows the contour of the brain
Subdural space
Between (below) dura mater and (above) arachnoid mater
Subarachnoid space
Separates arachnoid and pia mater
Cerebrospinal fluid appearance and function
Clear, colorless liquid that functions to lend buoyancy, for protection, in waste removal, and in providing a stable chemical environment
What is CSF produced by
The choroid plexus (area with ependymal cells) within each of the 4 ventricles
What do the ventricles in brain consist of?
Capillaries covered by simple cuboidal epithelium (ependymal cells that make CSF)
Blood-CSF fluid barrier
Tight junctions within capillaries in the choroid plexus form this that protects the brain; regulates substance entering the brain
Lateral ventricle
(2) located in each cerebral hemisphere; communicates with a third ventricle through an inter ventricular foramen
Interventricular foramen
How 2 lateral ventricles in each cerebral hemisphere communicate with a third ventricle
Cerebral aqueduct
Connects the third ventricle with the fourth ventricle
Circulation of CSF
Originated in choroid plexus, circulated through ventricles, makes its way into central canal of spinal cord, exits the fourth ventricle through two apertures (openings)
Does spinal cord go whole length of vertebrae?
NOOOO
Hydrocephalus
Hydro=water
Cephalus= head
“Water on the brain”- results from blockage of the route of CSF and its absorption
-causes- injury, rumors, infections, etc.
What fills up in hydrocephalus
The ventricles causing pressure and displacement
Blood supply in brain
Very metabolically active (demand for oxygen and glucose). Stopping blood supply for as little as 4 minutes can cause irreversible damage!!
Where is the blood-brain barrier NOT located?
It’s absent in areas of the brain (called circumventricular organs) that monitor blood glucose, pH, salinity, etc.
Circumventricular organs
Circum= around
Ventricular= ventricles
Monitor blood glucose, pH, salinity etc. Blood-brain barriers absent here **
3 functions of spinal cord
Locomotion, conduction, and reflex activity control
Where does the spinal cord begin and end?
Begins at the foramen magnum and ends and the FIRST lumbar vertebrae
How many pairs of spinal nerves are there?
31 pairs
How many cranial nerves are there
12 pairs
where does the spinal cord enlarge?
Cervical and lumbar areas; nerves to the appendages arise
Conus medullaris
Cord tapers to a point and end
Cauda equina
Nerve bundle exits the bottom of spinal cord (nerve fibers coming off conus medullaris)
*cauda-caudal-tail
Filum terminale
In addition to cauda equina
Lumbar puncture
Between vertebrae through fibrocartilage, punctures dura mater to get fluid; gives idea of what’s going on in brain
Fissure and sulcus in spinal cord cross section
Anterior median fissure (deep) and posterior median sulcus (not so deep)
Horns of spinal cord
Divided regions of a central area of gray matter in the spinal cord; 2 dorsal or posterior horns and 2 ventral or anterior horns
Gray commissure
Connects the right and left halves of horns in spinal cord
Central canal
Center of central gray matter (horns) in spinal cord
Route of sensory fibers **
Enter dorsal horn, synapse with an interneuron and somatic motor neurons exit via the central root of the spinal nerve.
How do nerves come out of spinal cord
In pairs (two roots)
Are tracts white or gray matter?
White matter
They are axons !!!
Ascending tracts
Spinal tracts that carry sensory information UP the spinal cord
Descending tracts
Spinal tracts that carry motor information DOWN the spinal cord
Decussation
a crossed tract of nerve fibers passing between centers on opposite sides of the nervous system
Left/right, right/left
What is the most important part of the brain?
Medulla oblongata
What does the medulla oblongata (hindbrain)control?
Coughing, hiccuping, sneezing, sweating, vomiting etc.
What 3 centers are in the medulla oblongata (hindbrain)
Cardiac, vasomotor, and respiratory centers
Hindbrain
Consists of the cerebellum, pons, and medulla oblongata
Brain stem
How does info get from the cerebrum to the cerebellum
Must go through pons
What does the pons (hindbrain) control
The gray matter of the pons contains nuclei (gray matter masses) concerned with sleep, posture, respiration, swallowing, and bladder control.
Nuclei in brain
Little areas of gray in inside (gray is usually outside of brain)
Cerebellum physical features
Largest of the hindbrain !!
Right and left cerebellar hemispheres connect via the vermis; three paired cerebellar peduncles (nerve tracts) connect the cerebellum to the brainstem
What connect he cerebellum (hindbrain) to the brainstem
3 paired peduncles (nerve tracts)
Peduncles
3 paired peduncles= nerve tracts that connect the cerebellum to the brainstem
What does the cerebellum (hindbrain) control?
Modulates and coordinates VOLUNTARY movement of the limbs, maintains muscle tone and posture, coordinated eye movements, and helps in learning motor skills
Tectum
Midbrain!
Consists of 4 nuclei called the corpora quadrigemina
What does the tectum (mid-brain) control
The corpora quadrigemina of the tectum function in visual attention, tracking objects, and visual reflexes
Reticular formation location
A group of 100 nuclei scattered throughout the medulla, midbrain, and pons
What does the reticular formation do?
Function in somatic motor control, autonomic control, arousal, and pain modulation.
What does the thalamus consist of (top of brain stem)
Two oval masses of gray matter, underneath each cerebral hemisphere
Function of the thalamus (top of brain stem)
It’s the gateway to the cerebral cortex, nearly all info heading to the cerebrum passes through the thalamus, EXCEPT for sensory input from smell
What is the one thing that does not pass through the thalamus?
Sensory input from smell
What does the hypothalamus (brains stem) control
Major control center for ANS and endocrine; also homeostasis (involuntary and hormones)
Function of nuclei
(Gray covered by white)
Regulate food-water intake, thermoregulation, cardiovascular (medulla oblongata) regulation, sleep/waking, emotions
Epithalamus function
cone-shaped gland, best known for synthesis of melatonin from serotonin. Role in light-sensitive circadian rhythms
Melatonin
Influence on sleep; regulates time clock (nightly sleep cycle)
Cerebral white
The white matter of the cerebrum does NOT make decisions, but comprises most of the cerebral volume
Cerebral cortex anatomy
(40% of brain mass) a layer of gray matter (2-3mm thick) covering the cerebral hemispheres
What are the 4 lines regions of the cerebral cortex
Frontal, parietal, occipital, and temporal
Basal nuclei
Masses of gray matter buried deep in the cerebral hemispheres, involved in motor control and some thought process
Limbic system
A loop of cortical structures surrounding the corpus callosum and thalamus
PERSONALITY AND EMOTIONS
What emotions are controlled by limbic system
Fear, anger, love, and others
Brain waves
Rhythmic voltage changes resulting from synchronized postsynaptic potentials in the cerebral cortex
How can brain waves be recorded
As as electroencephalogram (EEG); often used as a legal criteria for death
Sleep
A temporary state of unconsciousness (can be aroused)
Coma
Person cannot be aroused
What in the brain controls sleep
Hypothalamus and brain stem
How many stages of sleep are there
4
The 4th stage is deep (slow wave)
What happens during sleep several times a night?
Person backtracks to stage 1 and enters REM sleep
Rapid eye movement (REM) sleep
Enter several times a night, also called paradoxical sleep because of the difficulty with which a sleeper can be aroused. Most dreams occur during this period. As sleep continues periods of REM get longer
What happens during REM and what happens to it as sleep continues
Dreams and periods of REM sleep get longer as sleep continues
Insomnia
Symptoms and percent of population
Inability to fall or remain asleep
10%
Narcolepsy
Abnormal REM sleep causes extreme daytime sleepiness, behind between ages 15 and 25.
0.02-0.06%
Obstructive sleep apnea syndrome
Upper airway collapses repeatedly during sleep, blocking breathing. Snoring and daytime sleepiness
4-5%
Parasomnias
Sleepwalking, sleep talking, and night terrors outgrown less than 5% children
Restless leg syndrome
Brief, repetitive leg jerks during sleep. Leg pain forces person to get up several times a night
Very rare
7 functions of the cerebral cortex
Motor control, somatic control, special senses, association areas, cerebral lateralization, language, and memory
Motor control
(Cerebral cortex)
Volunteers muscle contractions are initiated in the motor association area of the frontal lobes. The impulse is then sent to the precentral (front) of the gyrus (primary motor area)
Somatic control
(Cerebral cortex)
The postcentral gyrus functions as the primary sensory area. Here neurons receive sensory info. (Receive sensory info in back)
Special senses
(Cerebral cortex)
Input from the special senses (light, hearing, etc) does NOT enter the postcentral gyrus but instead travels to other specialized areas of the brain
Association areas
(Cerebral cortex)
Carious association areas are located in the cerebral cortex including the somatosensory association area, the visual association area, the auditory association area, and the front association area.
Cerebral lateralization
(Cerebral cortex)
The assignment of different tasks to different hemispheres, and is correlated with handedness. Most Americans are right handed (left hemisphere). Males show more lateralization.
Language
(Cerebral cortex)
Includes several abilities and is assigned to different regions of the cerebral cortex
Memory
(Cerebral cortex)
The storage and retrieval of acquired info or skills; established in phases
Short term memory
(Cerebral cortex)
Lasts up to a few hours and is limited to 7-12 bits of info
Long-term memory
(Cerebral cortex)
Last longer and can store an unlimited amount of info
Positron emission tomography (PET)
Shows both blood flow and metabolism (of oxygen and glucose) in the tissues of the working brain (sees how active the brain is)
Magnetic resonance imaging (MRI)
Uses magnetic fields and radio waves to produce high quality images of brain structures (better than CT in analyzing the nervous system and other soft tissue)
Cranial nerve name and function
I
Olefactory
Smell
Cranial nerve name and function
II
Optic
Vision
Cranial nerve name and function
III
Oculomotor
Eyelid and eyeball movement
Cranial nerve name and function
IV
Trochlear
Innervates superior oblique and turns eye downward and laterally
Cranial nerve name and function
V
Trigeminal
Chewing, face and mouth touch and pain
Cranial nerve name and function
VI
Abducens
Turns eye laterally
Cranial nerve name and function
VII
Facial
Controls most facial expressions, secretion of tears and saliva taste
Cranial nerve name and function
VIII
Vestibulocochlear (auditory)
Hearing; equilibrium sensation
Cranial nerve name and function
IX
Glossopharyngeal
Taste; sense carotid blood pressure
Cranial nerve name and function
X
Vagus
Senses aortic blood pressure, slows heart rate, stimulates digestive organs, taste
Cranial nerve name and function
XI
Spinal accessory
Controls trapezius and sternocleidomastoid, controls swallowing movements
Cranial nerve name and function
XII
Hypoglossal
Controls tongue movements
What are the two cranial nerves that take part in controlling taste?
X Vagus
and
VII facial
What 2 cranial nerves have to do with the heart and blood pressure
IX Glossopharyngeal
and
X vagus
What 4 cranial nerves have to do with eye movement
II Optic III oculomotor IV Trochlear and VI abducens
Frontal lobes
Motor areas- voluntary skeletal muscle
Association areas- high intellectual processing
Parietal lobes
Sensory areas- temp., touch, pressure, pain (skin)
Association areas- understanding speech and words to express thoughts and feelings
Temporal lobes
Sensory areas- hearing
Association areas- interpret sensory experiences and remember visual scenes, music, etc.
Occipital lobes
Sensory areas- vision
Association areas- combine visual images with other sensory experiences
How are fibers classified
Direction (afferent/efferent), types of organs they innervate (somatic/visceral) and distribution (general/local)
** S-A-M-E
Mixed nerves
Have BOTH motor and sensory fibers
Sensory nerves (Olfactory and optic) contain…
Mostly sensory fibers
Motor nerves contain ….
Motor fibers
Ganglion
Cluster of nerve cell bodies generally outside the CNS
Location of cranial nerves
(12 pairs)
Emerge from base of brain lead to muscles and sense organs in head and neck for most part
Are spinal and cranial nerves part of the CNS or ANS?
ANS NOT the CNS !!!
How does each spinal nerve branch?
Into dorsal root and ventral root
Dorsal root ganglion
Occupied by cell bodies from afferent neurons
Spinal nerve is formed by..
Convergence of dorsal and ventral roots
Cauda equina is formed by…
The roots arising from segments L2 to Cx of the spinal region
What does the spinal nerve do after emerging from the vertebral column
It divides into dorsal root and ventral root and a small meningeal branch that leads to the meninges and vertebral column
dorsal ramus
Innervates the muscles and joints of the spine and the skin of the back
Ventral ramus
Innervate a the ventral and lateral skin and muscles of the trunk, plus gives rise to nerves leading to the extremities
What spinal nerve receives sensory input from a specific area of the skin (dermatome)?
Every spinal nerve except C-1
How long do spinal nerves extend
From foramen magnum to 2nd lumbar vertebra
End= conus medullaris
What continues after conus medullaris and attaches to coccyx?
Pia mater as filum terminale
Spinal nerve extending downward from conus
cauda equina
What two groves extend the length of the spinal cord
Anterior medial fissure and posterior median sulcus
Somatic reflexes
Quick, involuntary, stereotypes reactions of peripheral effectors to stimulation.
What is a spinal reflex made up of?
Reflex arc including: Somatic receptors, afferent nerve fibers, interneurons (association neurons), efferent nerve fibers, and skeletal muscle
What happens when a muscle is stretched
It contracts to maintain tone (*stretch flex)
Tendon reflex
(Knee jerk)
An example of monosynaptic reflex arc.
Golgi tendon organs
Located at junction of a muscle and its tendon
What do Golgi tendon organs produce?
An inhibitory response called the Golgi tendon reflex when muscle contracts too tightly (prevents damage to tendon)
What is the peripheral nervous system a part of?
ANS
What are the two parts of the peripheral nervous system
Somatic (motor and sensory) and autonomic (just motor)
Is the peripheral nervous system in the spinal cord?
NO outside of CNS
Somatic motor (efferent) divisions
Skeletal muscle, one efferent neuron, excitatory, acetylcholine (ONLY), voluntary
Autonomic divisions
Motor/efferent ONLY
Smooth muscle/cardiac muscle/glands (not endocrine), two efferent neurons, excitatory or inhibitory, post ganglionic, acetylcholine or norepinephrine, and involuntary
Can excitatory and inhibitory neurons go to same place?
Yea but stronger one wins or cancel each other out
What are the two efferent neurons in the autonomic peripheral nervous system
Pre ganglionic and post ganglionic
Pre ganglionic neuron
Dendrite + soma in CNS, axon exits
CNS proceeds to autonomic ganglion, always produces ACh!
Post-ganglionic neuron
Cell body WITHIN autonomic ganglion but refer to it as entirely in ANS. Produces ACh or Norepinephrine
What’s the one exception with the 2 efferent neurons in the autonomic peripheral nervous system?
Usually 2 efferent neuron pathways found in ANS but there is NO post ganglionic neuron to the adrenal medulla (one 1 pre gang.)
—> direct route to adrenal medulla, NO connection to autonomic ganglion. ACh
Adrenal medulla gland
Above kidney, stimulated by norepinephrine; gland produces norepinephrine and 80% epinephrine, releases into blood can act as neurotransmitter
What are the two divisions of the ANS?
Sympathetic and parasympathetic
What division of ANS are most organs innervate by?
BOTH sympathetic and parasympathetic
Sympathetic
- Division of ANS
- EXCITATORY
- (Aka thoracolumbar)
Where are pre ganglionic neurons in sympathetic division of ANS
They exit the CNS from this region of the spinal cord (thoracolumbar)
What does the sympathetic division of the autonomic nervous system do for us?
Preparation for stressful situations … “fight or flight system”
Do sympathetic and parasympathetic nervous systems combine?
Not usually bc they have opposite affects on cells/organs but they may both be active
Parasympathetic
- INHIBITORY
- craniosacral (head to tail)
- pre ganglionic neurons exit CNS from this region of the spinal cord
What does the parasympathetic nervous system do for us?
Returns body to normal conditions after stress
“Feed and breed”
“Resting and digesting”
What happens if both sympathetic and parasympathetic nervous systems are active?
The overall effect is influenced by the degree which one may predominate over the other and the particular nature of receptor sites
What is the result of the adrenal medulla exception to the sympathetic division of ANS?
Adrenal medulla releases its own norepinephrine, mostly epinephrine, which is carried via the blood stream to responsive receptor sites
What is a second exception to the sympathetic division of ANS?
Innervation of sweat glands, external genitalia, some skeletal muscle blood vessels. Here the post ganglionic neuron releases ACh not norepinephrine
What about the pre ganglionic cell is the same in both sympathetic and parasympathetic divisions?
It is ALWAYS myelinated sneaking out of spinal cord and ALWAYS releases ACh
How is the post ganglionic neuron different in sympathetic and parasympathetic?
Sympathetic- releases norepinephrine
Parasympathetic- ACh
Difference between pre and post ganglionic in both sympathetic and parasympathetic
Pre- myelinated
Post- not myelinated !!
Cholinergic receptors (membrane proteins)
Receptors that respond to ACh
2 different cholinergic receptors that bind ACh and other molecules with similar activity
Muscarinic (excite or inhibit)
and
Nicotinic (excite only)
Cholinergic fibers
Nerve fibers (cells) which produce (excite) ACh
Muscarinic receptors
- either excite or inhibit
- stimulated by muscarine (respond to mushroom poison)
Nicotinic receptors
- Stimulated by/respond to nicotine
- excite
Can you OD on nicotine?
Yes
Does it have to be ACh that turns on the cholinergic fibers: muscarinic receptors and Nicotinic receptors?
No, some chemicals can turn these on even though they’re not ACh
Two catecholamines
-Norepinephrine and epinephrine
What can adrenergic receptors do and where are they found?
️-Bind catecholamines (epinephrine and norepinephrine) and other molecules with similar activity
- found on autonomic effector organs regulated by catecholamines
Alpha receptors
Norepinephrine/epinephrine
EXCITATORY
Beta receptors
Norepinephrine/epinephrine
INHIBITORY
Why are there exceptions for both beta and alpha receptors of adrenergic receptors?
Because of the existence of different alpha and beta subtypes
What’s an example of a beta receptor exception?
Beta heart receptors- increased heart activity! (Excite instead of the normal function to inhibit)
Adrenergic fibers produce …
NOREPINEPHRINE
Epinephrine is produced by…
ADRENAL MEDULLA