BSNL 114 LECTURE 16 - ETSUYA

brain

develops a neural tube with several vesicular structures that gives rise to several regions

telencephalon

has cerebrum and lateral ventricles

diencephalon

has thalamus, hypothalamus, epithalamus and 3rd ventricle

mesencephalon

or mid brain and its aqueduct

Metencephalon

has pons, cerebrellum, and upper part of the 4th ventricle

Myelencephalon

has medulla oblongata and lower 4th ventricle

brain stem

continuous with the spinal cord and consists of the medulla oblongata, pons, and midbrain

Cerebellum

posterior part of the brain that coordinates muscle movements and maintains balance

Cerebrum (telencephalon)

supported on diencephalon and brain stem

2 important anatomical structures that protect the brain

cranium & meninges

cranium

bony part of brain

meninges

fibrous tissue

3 layers make up the meninges

dura mater, arachnoid mater, pia mater

dura mater

outer periosteal layer & inner meninges layer

periosteal and meningeal

two layers of dura mater

falx celebri

large, sickle-shaped, separates the cerebral hemispheres

tentorium cerebelli

2nd largest, crescent-shaped, separates cerebrum (occipital lobes) from cerebellum (arrow #5)

falx cerebelli

seperates the two hemispheres of the cerebellum. it lies inferior to the tentorium cerebelli, separating cerebellar hemispheres (arrow #7)

diaphragm sellae

smallest infolding covering pituitary gland & sella turcica

arachnoid

middle layer of meninges; weblike appearance that attaches it to deepest layer

arachnoid trabeculae

filaments between the arachnoid and pia mater within the subarachnoid space

superior sagittal sinus

subdural space

space between dura mater and arachnoid mater

subarachnoid space

skin of scalp

arachnoid mater

pia mater

the delicate innermost membrane enveloping the brain and spinal cord.

leptomeninges

The pia mater and arachnoid together

blood-brain barrier

complex system that separates the circulating blood from ECF of the brain. It is essential to prevent harmful substances from reaching the brain

Cerebral Spinal Fluid (CSF)

clear, colourless fluid that circulates within the brain and spinal cord, serving several important functions in the CNS

Circulation of CSF

CSF from the lateral ventricles → interventricular foramina → third ventricle → cerebral aqueduct → fourth ventricle → subarachnoid space or central canal.

mechanical protection of CSF

functions as shock-absorbing medium protecting brain and spina cord

chemical protection in CSF

provides optimal ionic composition for neural signalling

circulation in CSF

helps in exchange of nutrients and waste products between the blood and adjacent nervous tissue

temperature regulation in CSF

helps in maintaining a stable temperature

brain stem

between spinal cord and diencephalon

medulla oblongata

most inferior part of the brain stem; regulates breathing, heart rate, & blood pressure

the 'olives'

oval-shaped structures located on the anterior surface of the medulla, lateral to the pyramids

nucleus ambiguus

involved in swallowing (deglutition) & vocalization

dorsal/ventral respiratory group

regulates breathing

solitary nucleus

receives and processes sensory information from cardiovascular, respiratory, and gastrointestinal systems

hypoglossal nucleus

controls movement of tongue and speech

inferior olivary nucleus

associated with motor coordination & fine-tuning of movements

vestibulocochlear nerve

receives sensory input & sends motor output to cochlea of the inner ear for hearing

glossopharyngeal nerve

relays sensory & motor impulses related to taste, swallowing & deglutition

vagus nerves

processes input/output of pharynx, larynx & thoracic/abdominal viscera

accessory nerves

controls swallowing via vagus nerves

hypoglossal nerves

controls tongue movement; speech

pons

center structure of the brain stem, located between the midbrain and the medulla oblongata

pontine nuclei

serves as relay striations between cerebral cortex & cerebellum in regards to motor coordination

trigeminal nerves

regulates sensory input from head & face, governs chewing

abducens nerves

controls eyeball movement, particularly abduction (outward gaze)

facial nerves

regulates facial movements, saliva, tears

vestibulocochlear nerves

the vestibular and cochlear nuclei in the pons are involved in balancing and hearing

midbrain

or mesencephalon extends from pons to diencephalon. the pons is the center structure of the brain stem, located between the midbrain and the medulla oblongata

tectum of midbrain

superior and inferior colliculi

tegmentum of midbrain

involved in movement and arousal

cranial nerves

12 pairs of nerves that carry messages to and from the brain

oculomotor nucleus in the midbrain

controls eye movements & pupillary constriction

trochlear nucleus

controls superior oblique eye muscles

Edinger-Westphal nucleus

part of oculomotor complex controlling ciliary muscle for accommodation of the lens & pupil constriction

cerebral peduncles

located on the ventral surface of midbrain. has corticospinal tract (voluntary movements) & corticobulbar tracts (motor control of face & head)

reticular formation (RF)

complex network of nuclei & pathways located in the brainstem, extending from the medulla through the pons & midbrain. it plays a crucial role in various physiological functions & maintaining overall brain arousal

Reticular Activating System (RAS)

transmits sensory axons to the cerebral cortex directly and through the thalamus

Ralph nuclei

regulates mood, sleep, and pain perception

locus coeruleus

involved in attention, arousal, and stress responses

Pontine reticular formation

regulates REM sleep and arousal

medullary reticular formation

controls autonomic functions

Cerebrum

ability to read, write, speak; complex analysis etc.

cerebral sulci

the grooves between the cerebral gyri on the surface of the cerebrum

interlobar sulci of cerebrum

grooves that separate the various lobes of the cerebrum

cerebral fissures

grooves that separate parts of the brain

longitudinal cerebral fissure

separates cerebrum into right & left cerebral hemispheres

corpus callosum

broad band of white matter containing axons that extend between the cerebral hemispheres

Lobes of the cerebrum

frontal, parietal, temporal, occipital

Precentral cerebral gyrus

primary motor cortex of the cerebrum is situated anterior to the central sulcus

postcentral gyrus

the strip of parietal cortex, just behind the central sulcus, that receives somatosensory information from the entire body

lateral cerebral sulcus

separates the frontal lobe from the temporal lobe

parieto-occipital sulcus

separates parietal and occipital lobes

white matter

myelinated axons

Association tracts of white matter

conducts nerve impulses between cerebral gryri in the same hemisphere

commissural tracts of white matter

conducts nerve impulses one cerebral gyri to corresponding gyri in the other cerebral hemisphere.

projection tracts

conduct nerve impulses from cerebrum to lower parts of the CNS or from lower pars of the CNS to the cerebrum

limbic system

a rung of structures that encircles the upper part of the brainstem & corpus callosum inside of the cerebrum & floor of diencephalon

limbic lobes

a rim of cerebral cortex on medial surface of each hemisphere. includes cingulate gyrus & parahippocampal gyrus

dentate gyrus

lies between the hippocampus and parahippocampal gyrus

amygdala

lies close to caudate nucleus - responsible for emotions

septal nuclei

located inferior ro corpus callosum

mammillary bodies

lies close to the midline near cerebral peduncles. associated with recollective memory

olfactory bulbs

rests on the cribriform plate. related to smell (olfaction)

cerebral cortex

specific types of sensory, motor, & integrative signals are processed in certain regions of the cerebral cortex.

sensory areas of cerebral cortex

Primary somatosensory, Primary visual, Primary auditory, primary olfactory, primary gustatory

motor areas of cerebral cortex

voluntary muscle movements

primary motor cortex

located in the frontal lobe; is the key motor control center responsible for initiating and coordinating movements

premotor cortex

located immediately anterior to the primary motor cortex, responsible for movements such as typing

integrative areas of the cortex

higher cognitive functions; association areas, prefrontal cortex, wernickle's area, broca's area

association areas of cerebral cortex

integrate diverse information

prefrontal cortex

part of frontal lobe responsible for thinking, planning, and language

Wernickle's area

language comprehension

broca's area

speech production