Test 4 Flashcards
Embryonic development of the brain:
- Telencephalon
- Diencephalon
- Mesencephalon
- Metencephalon
- Myelencephalon
top of the brain, cerebrum
telencephalon
second part, thalamus and hypothalamus
diencephalon
cerebellum and pons
metencephalon
medulla
myelencephalon
Cerebral ventricles:
- filled with CSF and lined with ependymal cells (neuroglia)
- ventricles are a continuous tube running through the CNS
- 2 lateral ventricles
- septum pellucidum
- 3rd ventricle
- interventricular foramen
- mesencephalic aqueduct
- 4th ventricle
located in the cerebrum
2 lateral ventricles
separates the 2 lateral ventricles
septum pellucidum
located in the diencephalon
3rd ventricle
allows lateral ventricles to communicate with 3rd ventricle
interventricular foramen
connects 3rd ventricle to 4th ventricle
mesencephalic aqueduct (cerebral aqueduct/aqueduct of Sylvius)
Major areas and structures of the brain:
- Cerebrum
- Cerebral hemisphere
- Cerebral cortex
- Gyri
- Sulci
- Cerebellum
- Diencephalon
- Infundibulum
- Pituitary gland
- Brain stem
outer layer of gray matter
cerebral cortex
80% thalamus, hypothalamus
diencephalon
mesencephalon (midbrain), pons, medulla oblongata
brain stem
Protection of the brain:
- Skull
- Membranes–meninges
- Liquid cushion–CSF
- Blood-brain barrier–ensures the brain’s environment remains stable
What are the aspects of the dura mater?
- strongest
- double layer of connective tissue–periosteal layer attached to inner surface of the skull and meningeal layer forms the true external covering of the brain and continues to the vertebral canal
- Dural sinuses are located where two layers are not fused and collect venous blood from the brain and funnel to jugular veins
What are the aspects of arachnoid mater?
- loose brain covering
- separated from dura mater by subdural space
- subarachnoid space separates arachnoid from pia mater–contains CSF and contains largest blood vessels serving the brain (poorly protected)
- CSF is absorbed into the venous blood of the dural sinuses by the arachnoid villi
What are the aspects of pia mater?
- clings tightly to the brain
- anchored by processes of the astrocytes
- composed of connective tissue and tiny blood vessels
- external to the CNS
Membranes: dural folds
- stabilise and support the brain
- falx cerebri
- tentorium cerebelli
- falx cerebelli
projects at the longitudinal fissure, attaches at crista galli inferiorly and to internal occipital crest; encloses the superior sagittal sinus and inferior sagittal sinus
falx cerebri
separates the hemispheres of cerebellum from those of cerebrum; encloses the transverse sinus
tentorium cerebelli
separates cerebellar hemispheres along the midsagittal line
falx cerebelli
Protection of the brain: Liquid cushion
- gives buoyancy to CNS organs–reduces brain weight by 97%
- protects from blows and trauma
- may carry chemical signals–hormones
- arises from blood plasma
- choroid plexuses form CSF–filters tissue fluid from bloodstream and removes waste
- hydrocephalus
- circulation–replaces every 8 hours
- arachnoid granulation
What are the aspects of the hydrocephalus?
- failure to reabsorb fluid causes build up
- in infants causes head to enlarge
- in adults may result in brain damage because the skull is rigid
CSF returned to venous system by:
arachnoid granulation
Protection of the brain: Blood-brain barrier
- ensures the brain’s environment remains stable
- within most parts of the body, extracellular concentrations of hormones, amino acids, and ions are constantly changing, particularly after eating and exercise
- Exposure to chemical variations of hormones, amino acids, and ions would cause neurons to fire uncontrollably since they serve as neurotransmitters and ions like K+ can modify threshold for nerves
- Astrocytes stimulate endothelial cell of the brain capillaries to form tight junction
- selective barrier rather than absolute barrier
- nutrients, such as glucose, essential amino acids, and some electrolytes, move by passive transport through the endothelial cell membranes of capillaries
- Blood-borne metabolic wastes, such as urea and creatinine, as well as proteins, certain toxins, and most drugs, are prevented from entering the brain
- not well developed in newborns and preemies so toxic substance can readily enter the CNS
Blood-borne substances within the brain’s capillaries are separated from the extracellular space and neurons by:
These three conditions do what?
- the continuous endothelium of the capillary wall
- a relative thick basal lamina surrounding the external face of the capillary
- the bulb like “feet” of the astrocytes that cling to the capillaries
help provide tight joints and form “seamless” capillary walls
The blood-brain barrier is ineffective against what?
- Fats
- Fat-soluble molecules
- fatty acids
- oxygen
- carbon dioxide
- alcohol
- caffeine
- heroin
- nicotine
- anesthetics
Blood-brain barrier absent from the choroid plexuses causes what?
- The brain allows blood-borne molecules easy access to the neural tissue.
- The vomiting center of the medulla monitors blood for poisonous substances.
- The hypothalamus samples the blood to regulate water balance, body temperature, and other metabolic activities.
The brain stem consists of:
- medulla oblongata
- Pons varolii
- Mesencephalon or midbrain
contains vital centers necessary for survival; continuous with the spinal cord
medulla oblongata
What are the aspects of the medulla oblongata?
- cardiac center
- respiratory center
- vasomotor center
- Interconnections are made between all the vital centers so that responses of breathing, heart action, and blood pressure are coordinated
- contains non-vital centers for vomiting, sneezing, coughing, and hiccuping
regulates heartbeat and force of contraction
cardiac center
contains two of the three centers initiating rate and depth of breathing
respiratory center (medullary rhythmicity center)
helps control blood pressure by controlling diameter of muscular blood vessels
vasomotor center
What are the cranial nerves in the medulla oblongata that originate from the medulla?
- Vestibulocochlear nerve-8
- cochlear branch
- Glossopharyngeal nerve-9
- vagus nerve-10
- accessory nerve-11
- hypoglossal nerve-12
What are the aspects of the pons varolii?
- the basal portion of the pons acts as a relay station for motor fibers from the cerebrum to the cerebellum
- contains the pneumotaxic center
- contains the apneustic area
inhibits sustained inspiration–contributes to expiration during breathing
pneumotaxic center
sends stimulatory impulses to the respiratory area that activate and prolong inspiration and inhibit expiration
apneustic area
What are the cranial nerves that originate from the pons?
- Trigeminal nerve-5
- Abducens nerve-6
- Facial nerve-7
- Vestibulocochlear nerve-8
- vestibular branch
What are the aspects of the mesencephalon/midbrain?
- contains the cerebral aqueduct, corpora quadrigemina, and cerebral peduncles
- cerebral peduncles serve as a motor relay station for fibers passing from the cerebrum to the spinal cord, cerebellum, and pons. Also contains sensory fibers that pass from the spinal cord to the thalamus.
- Integrates visual and auditory reflexes.
- Monitors certain righting reflexes concerned with maintaining normal posture relative to the eyes and head
- contains red nucleus
- contains RAS
What are the visual and auditory reflexes that the mesencephalon integrates?
- Those concerned with objects seen that are approaching the body and that require muscular response to avoid them
- Turning the head to achieve the greatest benefit from an auditory stimulus
two pairs of sensory nerves (auditory and visual) nuclei
corpora quadrigemina
nerve fiber bundles
cerebral peduncles
blood vessels, subconscious control of upper limb position and muscle tone
red nucleus
helps maintain consciousness
RAS (reticular activating system)
What are the cranial nerves that originate from the midbrain?
- Oculomotor nerve-3
2. Trochlear nerve-4
The diencephalon consists of:
- Thalamus
2. Hypothalamus
composes 80% of the diencephalon’s “gateway to the cerebral cortex”
thalamus
The thalamus consists of:
- intermediate mass
2. thalamic nuclei
projection of gray matter extending into the ventricle
intermediate mass
each side is made of this
thalamic nuclei
What are the aspects of thalamic nuclei?
- Major relay station to the cerebral hemispheres for all types of sensory information, plays a part in the wakefulness or alerting mechanism
- ventral group
- medial group
- anterior group
- lateral group
- posterior group
vague awareness of less critical sensory sensations–pain, temperature, touch
ventral group
conscious awareness of emotions
medial group
part of the limbic system concerned with emotion and motivation
anterior group
helps produce complex reflex movements–especially outward expression of rage and fear
lateral group
visual and auditory information
posterior group
What are the structures associated with the hypothalamus?
- optic chiasma
- infundibulum
- pituitary gland
- mammillary bodies
crossover area for optic tracts (eye nerves)
optic chiasma
connects the hypothalamus to the pituitary gland
infundibulum
functions considered with endocrine systems
pituitary gland
relay station for olfactory neurons and olfactory reflexes, 2 rounded structures behind the infundibulum, control reflex movements for chewing, licking, and swallowing
mammillary bodies
What are the functions of the hypothalamus?
- it is the main visceral control center
- it is important in overall body homeostasis
- it links the nervous and endocrine systems
- temperature regulation
- pituitary functions
- regulation of water balance
- food intake
- regulation of gastric secretions
- emotions
- maintains the waking state and sleep patterns; exhibits properties of a self-sustained oscillator and acts as a pacemaker to drive many biological rhythms
- contains thirst center; certain cells in the hypothalamus are stimulated when the extracellular fluid volume is reduced. The stimulated cells produce the sensation of thirst
- mind-over-body phenomenon
What are the aspects of temperature regulation in the hypothalamus?
- heat loss–sweating, decreased muscle tone, dilation of skin blood vessels
- heat gain–skin vessels constrict, shivering, cessation of sweating
What are the pituitary functions of the hypothalamus?
produces Pituitary Regulating Factors which stimulate or inhibit pituitary production and/or release hormones in the anterior pituitary, nine chemicals have been found
What are the aspects of the hypothalamus regulating water balance?
it monitors blood osmotic pressure, produces ADH (antidiuretic hormone) and stimulates release of ADH from the pituitary to regulate tonicity of body fluids
What are the aspects of the food intake of the hypothalamus?
the hunger or feeding center is stimulated by an empty stomach which leads to eating that stimulates the satiety center and inhibits the feeding center
What are the aspects of the hypothalamus regulating gastric secretions?
increased hypothalamic stimulation results in increased gastric juice production, emotion may trigger release of gastric juices when there is no food present, which may lead to ulcer formation
What are the aspects of emotion in the hypothalamus?
expression (somatic patterns) of reactions of rage, pain, pleasure, anger, and sexual arousal, subconscious skeletal muscle control; ANS response–increased blood pressure, sweating, etc.
The hypothalamus is:
one of the last CNS areas to mature and because it controls temperature, premature babies have trouble controlling loss of body heat
What are the aspects of the cerebellum?
- Second largest part of the brain
- Externally consists of gray matter; internally consists of white (myelinated) matter
- Folia
- Covered in a layer of neural cortex
- Vermis
- Arbor vitae
cerebellar folds
folia
bands of cortex
vermis
white matter of cerebellum
arbor vitae
List the functions of the cerebellum:
- Operates at the conscious and subconscious level–continually compares higher brain intentions with body performance and makes corrections
- Coordinates muscular activity, integrates muscular movement, and predicts when to stop movements
- Coordinates reflexes that serve to maintain posture and equilibrium. The sensory impulses involved in these reflexes come from recepters, called proprioceptors, that are found in muscles, tendons, and from special sense organs such as the eyes and ears. The inner ear sends information to the cerebellum concerning equilibrium, and it in turn coordinates balance.
- Damage to the cerebellum results in tremors, loss of muscle tone, loss of equilibrium, inaccurate movements of voluntary muscles, and reeling walk.
What are the aspects of the cerebrum?
- It is our conscious mind.
- It is the largest part of the brain comprising 83% of the total brain.
- It is divided into lobes.
- It consists of two cerebral hemispheres connected by the corpus callosum.
- The surface of the cerebrum has ridges called gyri separated by grooves.
What are the lobes in the cerebrum?
- Frontal lobes
- Parietal lobes
- Temporal lobes
- Occipital lobes
- Island of Reil (Insula)
located deep within the brain and is covered by parts of the frontal, parietal, and temporal lobes. It is separated from these lobes by a circular sulcus. It is the area for the sense of taste.
Island of Reil (Insula)
Surface of the cerebrum:
- Precentral gyrus
- Postcentral gyrus
- Front and behind central
- sulcus
Shallow grooves are called:
sulcus
deep grooves are called:
fissure
What are the grooves/sulci of the cerebrum?
- Longitudinal fissure
- Transverse fissure
- Central sulcus
- Lateral sulcus
- Insula
separates the two hemispheres
longitudinal fissure
separates cerebral hemispheres from the cerebellum
transverse fissure
separates frontal from parietal lobe
central sulcus
outlines temporal lobe
lateral sulcus
island of cortex buried deep within the lateral sulcus; area for sense of taste
insula
3 regions of the cerebral hemisphere:
- Superficial cortex of gray matter
- internal white matter
- Basal nuclei
islands of gray matter deep in the white matter
basal nuclei
consists of neuron cell bodies, dendrites, unmyelinated axons–no fiber tracts
cerebral cortex (gray matter)
What are the aspects of cerebral white matter?
- Communication between cerebral areas and between cerebral cortex and lower CNS centers.
- Consists of myelinated fibers bundled into large tracts.
What are the bundles of myelinated fiber in cerebral white matter?
- Association fibers
- Commissures
- Projection fibers
What are the aspects of association fibers?
- Connect different parts of the same hemisphere
- arcuate fibers
- longitudinal fasciculi
- run horizontally
short, connect adjacent gyri
arcuate fibers
long, are bundled into tracts and connect different lobes
longitudinal fasciculi
What are the aspects of commissures?
- Connect the two hemispheres
- Ex.: corpus collosum deep within the longitudinal fissure
- runs horizontally
What are the aspects of projection fibers?
- Fibers entering the cerebral hemisphere from lower brain or cord centers and fibers leaving cortex to travel to lower centers.
- All projection fibers must pass through the diencephalon.
- Tie the cortex to the rest of the nervous system and to receptors and effectors of the body.
What are the aspects of basal nuclei?
- deep in the white matter of cerebrum are subcortical nuclei
- Control activities at a subconscious level
- May play a role in regulating attention and in cognition
- Important in starting, stopping, and monitoring movements executed by cortex; Ex.: arm swinging, walking, also intensity
- inhibit antagonistic or unneccessary movements
- Disorders of basal nuclei result in either too much or too little movement as in Huntington’s disease and Parkinson’s disease
What are the aspects of the limbic system?
- It is a functional brain system with networks of neurons that work together but span relatively large distance.
- It is located on the medial aspect to each cerebral hemisphere and diencephalons.
- Fornix
- System integrates and responds to a wide variety of environmental stimuli like odors
- output relayed by hypothalamus
- interacts with the prefrontal lobes so there is a relationship between our feelings and our thoughts, i.e. we react emotionally to things we consciously understand to be happening and are consciously aware of emotional richness of our lives
linnks the limbic system regions together
fornix
Communication between the cerebral cortex and limbic system explains:
why emotions sometimes override logic and why reason can stop us from expressing our emotions inappropriately
General characteristics of cerebral function:
- The two sides are not equal in function–areas are unequal and upside down (as in face and hand regions of the brain)
- Each hemisphere is concerned with sensory and motor function of opposite side of body
- Three functional areas.
- No functional area acts alone.
What are the three functional areas of cerebral function?
- Motor areas–voluntary
- Sensory areas
- Association areas–integration
What are the parts of the motor areas in cerebral function?
- Primary (somatic) motor cortex
- Premotor cortex
- Frontal eye field
What are the aspects of the primary motor cortex?
- Located in the precentral gyrus of frontal lobe of each hemisphere
- Pyramidal cells allow for voluntary movements of skeletal muscles. Long axons which project to spinal cord from large voluntary motor tracts called pyramidal or corticospinal tracts.
- Most neurons in these gyri control muscles in body areas having the most precise motor control.
- More area is given to those body parts where skilled or complex movement is required; ex. face, tongue, hands
- Current research indicates that a given muscle is controlled by multiple spots on the cortex and individual cortical motor neurons actually send impulses to more than one muscle; i.e. individual motor neurons control muscles that work together in a synergistic way–kicking a soccer ball
What are the aspects of the premotor cortex?
- anterior to precentral gyrus in frontal lobe
- controls learned motor skills such as writing, playing musical instrument
- coordinates eye and head movements
- memory bank of skilled activities
What is an aspect of the frontal eye field?
controls voluntary movements of the eyes
Damage to the primary motor cortex:
paralyses the body muscles controlled by those areas–right hemisphere affects left side of the body. Only voluntary control is lost.
Damage to the premotor cortex:
loss of motor skills programmed in that region; ex. ability to type
What are the parts of the sensory areas in cerebral function?
- Primary somatic sensory area
- Visual areas
- Auditory area
- Olfactory area
- Gustatory area
What are the aspects of the primary somatic sensory area?
- Found in the postcentral gyrus of the parietal lobe.
- Interprets most of the skin sensations–heat, cold, touch, pressure, and some pain
- Receives information from the general sensory receptors located in the skin and from proprioceptors in skeletal muscles
- Amount of sensory cortex devoted to a body region is dependent on the area’s sensitivity–i.e. face and fingertrips are the most sensitive in humans
- Responsible for comprehending what we touch
What are the aspects of the visual areas?
- occipital lobe
- receives impulses from the eyes and interprets shape, colour, and movement
- primary and association areas
- Damage to primary visual area results in blindness, but damage to visual association area can see but not comprehend what they are looking at
What are the aspects of the auditory area?
- Primary and association areas
- Temporal lobe
- receives impulses from the cochlea of the inner ear
- interprets the basic characteristics of sound such as pitch and rhythm
- memories of sounds heard in the past stored here
What are the aspects of the olfactory area?
- temporal lobe
2. interprets sensations of smell
What are the aspects of the gustatory area?
- interprets sensations of taste
2. parietal lobe
Areas from which specific responses or sensations cannot be elicited when they are stimulated. These areas are related to memory, reasoning, verbalising, judgment, and emotional feelings.
Integrative/association areas
List the parts of the association areas:
- Prefrontal area
- General interpretative area (Wernick’s area or Temporal Association Area)
- Broca’s Speech area
- Occipital association area
- Parietal association area