Unit 1: Brain

Glucose and brain

There is no glucose stored in the brain, but there must be a constant supply entering the brain

What are the first symptoms of hypoglycemia (low blood sugar)

Light headedness, dizziness, irritability, headache

The brain gets its blood supply from carrying glucose and oxygen from the….

Bilateral common carotid arteries and bilateral vertebral arteries

Blood returns to the lungs from the brain via

Bilateral internal jugular veins

BBB

prevents passage of many substances from blood into brain tissue

BBB are mostly composed of

Astrocytes which protect the brain from harmful substances

-also makes it challenging to make drugs for CNS disorders bc its difficlt to cross the BBB

Creatine, urea, and most ions cross BLANK from blood to brain

Slowly

Some substances, such as proteins and antibiotics, do BLANK cross the BBB at all

NOT

Lipid soluble substances, such as oxygen, carbon dioxide, alcohol, and most anesthetic agents cross BLANK to brain tissue

EASILY

Dura Mater

-superficial layer of dense irregular CT

-surrounded by a layer of fat and CT between the Dural mater and the internal wall of the vertebral canal called the epidural space

Arachnoid Mater

-the middle layer

-avascular (no blood supply)

-space between arachnoid mater and dural mater called the subdural space

Pia Mater

-innermost layer made of thin, transparent layer of CT that adheres to the brain and spinal cord

-contains many BV that supply oxygen and nutrients to the brain and spinal cord

-BV are sheathed by pia mater as they pentetrate the brain from the surface inward

Space between the arachnoid mater and pia mater is called

Subarachnoid space

Falx Cerebri

Separates the left and right hemispheres

Falx cerebelli

Separates the left and right hemispheres of the cerebellum

Tentorium Cerebelli

separates the cerebrum and cerebellum

CSF

-clear colorless liquid that protects the CNS against harmful chemicals and physical damage. Also carries oxygen, glucose, and other needed chemicals

-produced by choroid plexuses found in the ventricles of the brain

Choroid Plexuses

A network of capillaries and BV inside the ventricles that produce CSF

-Ventricles: cavities within the brain that contain large amounts of CSF

Lateral Ventricle

Surrounded by the genu of the corpus callosum

Third ventricle

Inferior to the corpus callosum

Fourth ventricle

between the pons and cerebellum

Cerebral aqueduct

CSF filled channel thru the midbrain of the brainstem that connects the 3rd and 4th ventricles to each other

The Brainstem: Medulla Oblongata

Most inferior part of the brain. Contains the ascending sensory and descending motor tracts

-contains the cardiovascular center controlling rate and force of heartbeat as well as diameter of blood vessels

-the medulla also contains the medullary rhythmic area of respiratory center controlling the rhythm and rate of breathing

-controls reflexes such as vomiting, coughing, and sneezingD3

Decussation of the pyramid’s

Pyramids cross within the medulla taking most of the motor axons with it

-most skeletal muscles are controlled by the contralateral part of the cerebral cortex

Cranial nerve emerging from Medulla: Vestibulocochlear (VII) cochlear branch

Sensory and motor associated with hearing (cochlear branches)

Cranial nerve emerging from medulla: Glossopharyngeal (CN IX)

Sensory and motor control swallowing, taste, salivation

cranial nerve emerging from medulla: Vagus (CNX)

sensory and motor associated with voice production, digestive secretions, taste, and slowing of heart rate

Cranial nerve emerging from medulla: Accessory nerve (CN XI)

motor: swallowing and shoulder shrugging (spinal portion)

Cranil nerve emerging from medulla: Hypoglossal nerve (CN XII)

Motor: tounge movement and swallowing

Pons

Directly superior to medulla and anterior to cerebellum

-helps control breathing with the pneumotaxic and apneustic areas

Cranial nerves emerging from pons: Trigeminal (CN V)

Sensory and motor, sensory from the head and face, motor from chewing (mastication)

Cranial nerves emerging from pons: Abudecens (CN VI)

Motor eyeball movement

Cranial nerves emerging from the pons: Facial VII

motor and sensory associated with sensory for taste and motor for saliva secretion, tears, and facial expression

Cranial nerves emerging from the pons: vestibulochochlear CN VIII

vestibular branch: sensory and motor associated with balance and equilibrium

Cerebral Peduncles

anterior part of the midbrain containing axons of the sensory and motor tracts

Tectum

Superior part of the midbrain divided into corpora quadrigemina

-superior colliculi: 2 superior elevations that are reflex centers controlling movements of the eyes, head, and neck in response to visual stimuli

-inferior colliculi: 2 inferior elevations that are reflex centers for movements of the head and trunk in response to auditory stimuli

Cerebral Aqueduct

CSF filled channel between the tectum and the cerebral peduncles that connects the third and fourth ventricles to each other

Cranial nerves emerging from midbrain: CN III Oculomotor

motor movements of ipsilateral eyeball, constriction of the pupil, changes in lens shape

Cranial nerves emerging from midbrain: CN IV trochlear

Motor movements of ipsilateral eyeball

Structures of the cerebellum

-cerebellar hemispheres on the left and right

-vermis: the raised structure along the median line

-Arbor vitae: highly branched, internal white matter

Roles of the cerebellum

-monitors intentions for movement

-monitors actual movement

-compares the command signals

-sends out corrective signals

-Summary: important in learning and performing coordinated, highly skilled movements

-Function: compares intended movements with what is actually happening to coordinate and smooth out complex, skilled movements. Also regulates balance and posture

Diencephalon

-extends from brainstem to cerebrum

-includes the thalamus, hypothalamus, epithalamus, and subthalamus

Thalamus

Relays sensory input to the cerebral cortex, provides crude perception of touch, pressure, pain, temperature. Also contributes to emotions, memory, cognition and awareness

Hypothalamus

-inferior to subthalamus

-contains mamillary bodies, infundibulum, and median eminence (encircles the infundibulum)

-controls and integrates the autonomic nervous system and pituitary gland

-regulates emotional and behavioral patterns

-body temp, eating, and drinking behavior

-maintains waking state and established sleeping patterns

Subthalamus

Just posterior to the hypothalamus

-Help control body movement

Epithalamus

-superior and posterior to the thalamus

-contains pineal gland (endocrine) which secretes melatonin (thought to promote sleepiness)

Cerebrum

-on top of the diencephalon

-contains the cerebral cortex (the outer layer of gray matter of the cerebrum..made up of sulci, gyri, and fissures)

-divided into bilateral hemispheres

-Each hemisphere is divided into lobes

Frontal lobe

Anterior-most lobe

-chiefly concerned with voluntary motor functions, motivation, foresight, planning, memory, mood, emotion, social judgement, aggression

-precentral gyrus: the posterior most gyrus of frontal lobe.

a. the somato-motor center of the cerebral cortex

b. voluntary motor impulses begin here

c. located anterior to the central sulcus

Parietal Lobe

Divided from the frontal lobe by central sulcus

-concerned with sensory reception and integration of somatosensory, taste, and some visual information

-Postcentral gyrus: the anterior most gyrus of the parietal lobe

a. the somatosensory center of the cerebral cortex

b. all nerve impulses from perceived somatic sensations have their CNS destination here

c. located posterior to the central sulcus

Somatic motor pathways

Control of body movements involves several regions of the brain

a. cerebral cortex: precise, discrete muscular movements

b. Basal ganglia: establish a normal level of muscle tone, integrate semi voluntary, automatic movements

c. cerebellum: assist cortex and basal ganglia in making body movements smooth and coordinated by maintaining balance and posture

-the primary motor area of the brain is known as the precentral gyrus

Direct motor pathways

Propagate motor command impulses from brain to skeletal muscles

-AKA pyramidal pathways because they travel thru the pyramids

Indirect motor pathways are AKA

extrapyramidal

Upper motor neurons

Neurons that within the brain and spinal cord gray matter (second and third order neurons)

-travel down the spinal cord and synapse with an interneuron which then synpses with a lower motor neuron.

-If there is a lesion of a lower motor neurons, the result is ipsilateral flaccid paralysis.

-If there is a lesion of an upper motor neuron, the result is contralateral spastic paralysis.

Lower Motor neurons

from the anterior horn of the spinal cord to the skeletal muscles. Also, from the motor nuclei of a cranial nerve to its effector.

Occipital lobe

The posterior most lobe. Separated from the parietal lobe at the parieto-occipital sulcus

-the principal visual center of the brain

Temporal Lobe

-Lateral, horizontal lobe

-divided from the parietal lobe by the lateral sulcus

-concerned with hearing, smell, learning, memory, visual recognition,