Nervous Tissue/Brain and Cranial Nerves (Ch 14/15) Flashcards
What is included in the nervous system?
all neural tissue in body
- neurons
- glial cells
What are the functions of the nervous system?
- Collect info: monitor external/internal changes (sensory input from the PNS)
- Process/evaluate info: processes sensory input and determines response
- Respond to info: dictates response by activating effector organs
What are the divisions of the nervous system?
Central Nervous System (CNS): brain + spinal cord
Peripheral Nervous System (PNS): all neural tissue outside of CNS, spinal/cranial nerves + ganglia
ganglia
collection of cell bodies outside of the nervous system
Nervous System Divisions
- Sensory Nervous System
- Somatic Sensory
- Visceral Sensory - Motor Nervous System
- Somatic Motor
- Autonomic Motor
Sensory Nervous System
- contains receptors
- transmits info from receptors –> CNS
- -> somatic sensory and visceral sensory
Motor Nervous System
- transmits info from CNS to body
- sends motor info to effectors
- -> somatic motor and autonomic motor
Somatic Sensory
- part of Sensory Nervous System
- receives sensory info from skin, fascia, joins, skeletal muscles
- free nerve endings in almost all body tissues
- includes receptors for touch, pain, pressure, vibration, and temp
- ->also proprioception (sense of body in space) in skin, body wall, and limbs
- “special senses” (vision, taste, hearing, balance, smell)
Visceral Sensory
*part of Sensory Nervous System
receives sensory info from viscera (organs)
-stretch/temp
Somatic Motor
- part of Motor Nervous System
- a.k.a. “voluntary” nervous system: innervates skeletal muscle
- contraction of skeletal muscles (ex. walking)
Autonomic Motor
- part of Motor Nervous System
- a.k.a. autonomic nervous system (ANS) or “involuntary” nervous system
- regulates contraction of smooth/cardiac muscle and gland secretion
- subdivides into sympathetic and parasympathetic nervous system
What are the types of nervous tissue cells?
neurons and glia
neurons
transmit electrical signals and nerve impulses
–> include: soma, dendrites, axon, myelin sheath
glia
“nerve glue” - supporting cells
Soma
- part of neuron
- “cell body”
- contain nucleus, cytoplasm, organelles
Dendrites
- part of neuron
- receive signal, transmit to soma (cell body)
Axon
- part of neuron
- transmits signal to axon terminals
Myelin Sheath
- part of neuron
- insulates neuron, helps propagate signal
What is the signal pathway of nerve impulses?
dendrite –> cell body –> axon –> axon terminal –> synapse/skeletal muscle
Synapse
a site where an axon connects with another cell (neuron cell or muscle/gland cells)
Glia
- support and nourish the neurons
- each type has a slightly different function
- carry no information
What are the types of Glia of the CNS?
ependymal cells
microglia
oligodendrocytes
astrocytes
What are the types of Glia of the PNS?
schwann cells
satellite cells
schwann cells
myelinated axons on the PNS
satellite cells
found in ganglia, surround neuron cell bodies
Nerve
a collection of axons in the PNS
- axons arranged in parallel and wrapped in CT
- nerve can contain myelinated and/or non-myelinated sensory and/or motor axons depending on nerve function
Nerve Structure
- each axon surrounded by myelin sheath (Schwann Cells)
- group of axons = nerve fascicles
- group of fascicles = nerve
- -> similar to skeletal muscle
What are the 3 parts of a nerve?
- Endoneurium: surrounds axon and myelin sheaths
- Perineurium: surrounds the fascicle
- Epineurium: surround the entire nerve
Meninges
membranes that surround/protect the brain
Cerebrospinal Fluid
-cushions the brain –> brain/spinal cord “float” in CSF
-resists compressive forces
Functions:
-feeds brain
-removes wastes
-carries chemical signals
Blood Brain Barrier
protects brain from exposure to toxins
What are the functions of meninges?
- cover/protect CNS
- enclose/protect blood vessels to CNS
- contain/circulate CSF
What are the parts of the meninges?
- Pia Mater
- Arachnoid Mater
- -> subarachnoid space - Dura Mater
Pia Mater
“tender mother”
- innermost layer, follows curves of brain
- very delicate
- lots of blood vessels
Arachnoid Mater
“spider mother”
-superficial to pia mater
Subarachnoid space
web-like threads attach arachnoid mater to pia mater
-filled with CSF
Dura Mater
“hard mother”
- outermost layer
- two layers of dense fibrous CT (meningeal and periosteal (next to bone))
- in some spots…separates to form dural sinuses inside
Dural Venous Sinuses
- drain blood from brain and into internal jugular veins to heart
1. Superior Saggital Sinus
2. Straight Sinus
3. Transverse Sinus
4. Sigmoid Sinus
Superior Saggital Sinus
- dural venous sinus
- along midline of cranium between cerebral hemispheres
Straight Sinus
- dural venous sinus
- between cerebral hemispheres
Transverse Sinus
- dural venous sinus
- along posterior/lateral side of cranium
Sigmoid Sinus
- dural venous sinus
- “S” shaped
- drains into internal jugular veins
Ventricles
- -> 4 interconnected cavities/expansions within brain for circulating CSF
- lateral ventricles (2) communicate with third ventricle via interventricular foramen
- third ventricle drains into fourth ventricle via cerebral aqueduct
Where are the 2 lateral ventricles found?
in the cerebrum
Where is the third ventricle found?
in diencephalon
Where is the fourth ventricle found?
between the brainstem and the cerebellum
What is the process of the creation of CSF?
- made in choroid plexuses in ventricles
- flows through ventricles and into subarachnoid space
- flows through subarachnoid space
- absorbed in dural venous sinuses –> drains into internal jugular veins
* 500ml/day is processed/circulated
What are the functions of the brain?
- control HR, BP, and maintain homeostasis
- innervation of head, neck, and viscera
- high level tasks: intelligence, consciousness, memory, emotion, behavior
Parts of the Brain
- Cerebellum
- Cerebrum
- Diencephalon
- Brain Stem
What is the grey matter of the brain?
on the outer part of brain (cerebellar/cerebral cortexes) as well as the innermost regions
-unmyelinated neurons and neuron cell bodies
What is the white matter of the brain?
made of myelinated (and some non-myelinated) axons
Diencephalon
- surrounded by cerebral hemispheres, deep to cerebrum
- contains 3rd ventricle
1. thalamus: lateral walls
2. hypothalamus: floor
3. epithalamus: roof
Thalamus
*part of diencephalon
“gate-keeper” for sensory info
-lateral walls of 3rd ventricle
-relays somatosensory, visual, and auditory info (NO smell)
-> any part of brain (sensory or not) that communicates with cerebral cortex must go through thalamus
Hypothalamus
*part of diencephalon MAIN visceral control center of the body, regulates many activities: -controls ANS -regulates body temp -regulates hunger/thirst -regulates sleep-wake cycles -controls endocrine system -controls emotional responses -controls motivational behavior -formation of memory
-related to pituitary gland (“master” gland)
Epithalamus
- part of diencephalon
- forms roof of third ventricle
- includes pineal gland (endocrine function) and a few brain nuclei
Brain Stem and functions
composed of medulla (inferior), pons (mid), and midbrain (superior)
Functions:
1. passageway for fiber tracts between cerebrum and spinal cord
2. cranial nerves and innervation of face/head
3. automatic behaviors needed for survival (ex. breathing)
4. integrates auditory and visual reflexes
Midbrain
- part of brainstem
- located between diencephalon and pons
- internal cavity is cerebral aqueduct (connects 3rd/4th ventricles)
- tectal plate
Tectal Plate
- part of midbrain
- ->integrates auditory and visual reflexes
- Superior Colliculus: acts for visual reflexes
- Inferior Colliculi: responds to sound
- ->on posterior midbrain
Pons
- part of brainstem
- located between midbrain and medulla, separated by cerebellum by 4th ventricle
- bridge between brainstem and cerebellum (passes motor reflexes from here)
Medulla Oblongata
- part of brainstem
- most posterior part of brainstem
- pyrimidal tracts carry voluntary motor output from cerebrum to brain stem
- fibers “decussate” so left brain controls right side of body (and vice versa)
Cerebellum
-makes up 11% of brain mass
-posterior to pons and medulla oblongata
-connected to brainstem by cerebellar pundicles
-2 hemispheres connected by vermis
-folia are leaf-like folds that increase SA in white matter
-outer cortex is gray matter/arbor vitae is white matter
Functions: SMOOTHS and COORDINATES body movements, helps maintain posture/equilibrium
cerebellar pundicles
what connects the cerebellum and brainstem
vermis
what connects the two hemispheres of the brain
folia
leaf-like folds that increase SA in white matter of cerebellum
Processing of the Cerebellum
- receives info from cerebrum on movements planned
- compares planned movements with current body position
- sends instructions back to cerebral cortex to readjust/refine motor commands
Cerebrum
- divided into two halves *largest part of brain
- each hemisphere has 5 distinct lobes (frontal, parietal, occipital, temporal, insula) –> lobes named for overlying bones
Insula
lobes of brain deep to frontal/temporal lobes
Gyri
ridges of brain tissue, allow for more cerebral cortex to fit into the cranial vault
–> pre central and post central gyri
pre central gyri
in posterior frontal lobe
postcentral gyri
in parietal lobe
Sulci
grooves between the gyri
–> central, parieto-occipitaq, and lateral sulci
central sulcus
separates pre central and post central gyri
lateral sulcus
separates temporal and frontal lobes
Functional areas of the cerebrum
- Sensory: conscious awareness of sensation (ex. touch/hearing)
- Association Areas: integrate information
- Motor Areas: voluntary motor functions
Primary Somatosensory Cortex
- in cerebrum
- receives info from somatic senses and enables conscious awareness of the senses (“know what you are feeling”)
- located in postcentral gyrus
Sensory Homuniculus
- -> each region of the sensory cortex receives sensory stimuli from a specific body region so a “map” can be created
- amount of cortex used for sensory info is NOT related to absolute size, but to amount of info (ex. lips/fingertips are most sensitive)
Sensory Cortical Regions
- in cerebrum
1. Primary Auditory Cortex
2. Primary Visual Cortex
Primary Auditory Cortex
- Sensory Cortical region (cerebrum)
- in temporal lobe, receives/processes auditory info from inner ear
Primary Visual Cortex
- Sensory Cortical region (cerebrum)
- in occipital lobe, receives visual info from retina of eye
Primary Motor Cortex
- located in pre central gyrus
- controls voluntary skeletal muscle activity
- other motor areas include Broca’s
Motor Homuniculus
- ->as with sensory homunculus, human body represented spatially in primary motor cortex
- face and hand are very large because of need for very precise motor control
Broca’s Area
- Left Hemisphere
- motor speech area
- if damaged…can understand speech but cannot speak fluently
Wernike’s Area
- Left Hemisphere
- recognition/understanding of speech
- if damaged…can speak but cannot understand language
Corpus Callosum
- white matter of cerebrum
- largest, most visible band of commissural fibers that connect two hemispheres
Association Fibers
- white matter of cerebrum
- short fibers that connect regions in the same hemispheres
Basal Nuclei (ganglia)
- deep gray matter of cerebrum
- involved in motor control
- composed of caudate nucleus, putamen, and globes pallid us
- work with cerebral nuclei to control movement
- start, stop, and regulate the intensity of voluntary movements
- -> damage = Parkinson’s disease
Limbic System
- includes part of cerebrum/diencephalon
- involved with emotion/motivation
- creating, storing, and retrieving memories
- -> includes cingulate gyrus, hippocampus, various nuclei (all linked together by fornix)
cingulate gyrus
- part of limbic system
- superior to corpus callosum
- emotional response
hippocampus
- part of limbic system
- stores long-term memory
What are the arteries of the head?
- R/L common carotid arteries
- internal/external carotid arteries
–> common carotid a. both ascend into the neck/head and divide into internal/external carotid a. which feed head, brain, and orbital regions
(internal supplied anterior brain/eyes)
Blood supply for the brain
internal carotid a. –> anterior/middle cerebral a.
anterior cerebral a. –> anterior communicating a. (supplies frontal lobe)
middle cerebral a. –> supplies parts of temporal/parietal lobes (80% of cerebrum)
R/L vertebral a. fuse –> basilar a. –> posterior cerebral a. (connected by posterior communicating a. to anterior cerebral a.)
Cerebral Arterial Circle
“Circle of Willis”
- an anastomosis to protect brain’s blood supply (re-routing of blood flow)
- circle around base of cerebrum
Formed by:
- L/R posterior cerebral a.
- L/R posterior communicating a.
- L/R internal carotid a.
- L/R anterior cerebral a.
- anterior communicating a.
Central Nervous System
- includes neural tissue, blood vessels, and connective tissues
- responsbile for integrating, processing, and coordinating sensory data/motor commands
- where higher level functions occur (intelligence, memory, learning, emotion)
Peripheral Nervous System
- includes nerves outside of spinal cord, brain, and ganglia
- link all regions of body to CNS
- delivers sensory info to CNS, carries motor commands to peripheral tissues/systems
Parkinsons Disease
Damage to Basal (Cerebral) nerve –> basal ganglia overfiring
- “resting tremors” while sitting still
- hard to navigate small spaces
- shuffled gait
Stroke
tissues of brain deprived of oxygen/nutrients/blood supply causing them to die
Ischemic Stroke
brain deprived of oxygen = occlusion of blood vessel –> cut off blood from brain
- usually die from plaque buildup in artery
- blood clots form directly in brain or travel there from other body parts
Hemorrhagic Stroke
hemorrhage or aneurysm (region in blood vessel wall weakened –> blood balloon –> rupture with increased BP)
Broca’s Aphasia
Brocas = speech production
- not speaking properly
- repeat words in odd order
Wernikes Aphasia
Wernikes = speech comprehension
-speak quickly/fluently but incorrect meaning
Hematoma
tear through blood vessel –> bleeding into portion of brain (blood pools)
- puts pressure on parts of brain
- common in epidural and subdural space
- -> bad if damage to artery due to increased BP
concussion
short period of brain not working properly due to a blow to the head
