Lecture 32- The Brain II Flashcards
What does the diencephalon consist of?
Thalamus and hypothalamus
Thalamus
Mediates sensation, motor activities,cortical arousal, learning and memory
acts as a relay station to conduct sensory impulses to the primary sensory areas of the cerebral cortex and transmits motor information from the cerebellum and basal nuclei to the primary motor area of the cerebral cortex
Hypothalamus
Control centre of the body regulating autonomic nervous system activity
initiates physical responses to emotions, and regulates body temperature, food intake, water balance, thirst, sleep-wake cycles, and endocrine function.
It is the integration centre of the autonomic nervous system.
Regulates pituitary gland and produces oxytocin and anti diuretic hormone
What does brain stem consist of?
Midbrain, pons and medulla oblongata
Midbrain structures
cerebral peduncles, which contain pyramidal (corticospinal) motor tracts that descend toward the spinal cord.
Also within the midbrain are the corpora quadrigemina, which control visual and auditory startle behaviours.
Pons
contains fibre pathways between the brain and spinal cord, as well as giving rise to some cranial nerves, and contains some important nuclei, one that helps control breathing
Medulla oblongata
the location of the medullary pyramids, which act as crossover points for corticospinal motor tracts, resulting in the contralateral control of voluntary movements.
It also houses neurons controlling vital functions such as cardiac and respiratory rate.
Cerebellum
Second largest area of the brain
Adjusts motor output,ensuring coordination and balance
processes inputs from several structures and coordinates skeletal muscle contraction to produce smooth movement.
may also play a role in thinking, language, and emotion.
What does the cerebellum consist of?
Anterior and posterior lobes coordinate body movements, and the flocculonodular lobes adjust posture to maintain balance.
Three paired fibre tracts, the cerebellar peduncles, communicate between the cerebellum and the brain stem.
Grey matter is located in outer cortex (folia) and in deeper nuclei. White matter tracts are called arbor vitae
Limbic system
involved with emotions and is extensively connected throughout the brain, allowing it to integrate and respond to a wide variety of stimuli.
Reticular activating system
extends through the brain stem and keeps the cortex alert while suppressing familiar, repetitive, or weak sensory inputs. 99% of sensory input is not relayed to consciousness.
Ignores repeated and irrelevant things
Broca’s area and wernickes area
ability to both speak and understand language is produced in these areas
Memory
Storage and retrieval of info
Declarative memory (two stages)
Fact based
Two stages:
Short term memory- allows the memorization of a few units of information for a short period of time.
Long term memory- allows the memorization of potentially limitless amounts of information
for very long periods.
How can declarative memory be affected?
emotional state (best if alert, motivated, excited or surprised), rehearsal, association of new information with old, or the automatic formation of memory while concentrating on something else.
What is the result of damaged hippocampus or surrounding temporal lobe structures?
only slight memory loss.
Bilateral destruction causes widespread amnesia.
Consciousness
clinically defined on a continuum that measures behaviour in response to stimuli and ranges through several stages: alertness, drowsiness or lethargy, stupor, and coma.
Syncopy (fainting)
brief loss of consciousness, most often due to inadequate cerebral blood flow caused by low blood pressure or sudden, severe emotional stress.
Coma
unconsciousness for an extended period.
Oxygen consumption is lower than during sleep.
Sleep
state of partial unconsciousness from which a person can be aroused
Two major sleep types
non-rapid eye movement (NREM)
rapid eye movement (REM).
non rapid eye movement
is restorative
Rapid eye movement
allows the brain to analyse events or eliminate meaningless information.
Dreaming occurs and skeletal muscles are inhibited during REM sleep.
Meninges
Three connective tissue membranes that cover and protect CNS
Dura mater (menix)
most durable, outermost covering that extends inward in certain areas to limit movement of the brain within the cranium.
Arachnoid mater (menix)
the middle meninx that forms a loose brain covering.
Pia mater (menix)
innermost layer that clings tightly to the brain.
Blood brain barrier
mechanism that helps maintain a protective environment for the brain.
contains exceptionally impermeable tight junctions keep brain separated from many bloodborne substances.
Three layers blood brain barrier is made up of…
Continuous endothelium of capillary walls.
Thick basal laminate around capillaries.
Feet of Astrocytes surrounding neurons
What can pass through blood brain barrier?
Nutrients
essential amino acids
some electrolytes
Alcohol
Nicotine
Anaesthetics
What can’t pass through blood brain barrier?
Metabolic wastes
Proteins
Toxins
Most drugs
Where is blood brain barrier absent?
some areas, such as the vomiting centre and the hypothalamus
these brain areas need to monitor chemical composition and temperature of blood.
Cerebrospinal fluid
fluid found within the ventricles of the brain and surrounding the brain and spinal cord.
CSF gives buoyancy to the brain, protects the brain and spinal cord from impact damage, and is a delivery medium for nutrients and chemical signals.
Ventricles
lined with ependymal cells and are filled with cerebrospinal fluid.
The ventricles of the brain are connected to one another and to the central canal of the spinal cord
Four ventricles in the brain
paired lateral ventricles deep within each cerebral hemisphere
a third ventricle within the diencephalon
a fourth ventricle at the cerebellum.
Ependymal cells are responsible for keeping CSF circulating.
Arachnoid granulation villi
pockets of the arachnoid membrane that extend into the dura mater sinuses, such as the superior sagittal sinus.
This is where CSF can be reabsorbed into venous blood to re-join the circulatory system.
