BIOLOGY 161 LAB – BRAIN

AND VENTRICLES

Scott.lehbauer@lethbridgecollege.ab.ca

Brain Structures

BRAIN STRUCTURESHypothalamus – found below the

thalamus it caps the brain stem and forms the walls of the 3rd ventricle. It is the main visceral control center and vital in overall body homeostasis functions including:

1. Autonomic Control Center2. Center for Emotional Response3. Body Temperature Regulation4. Regulation of food Intake5. Regulation of water balance6. Regulation of sleep-wake

cycles7. Control of Endocrine Function

Hypothalamus

BRAIN STRUCTURESPituitary Gland – sits

securely in the sella turcica of the sphenoid bone. It is shaped like a pea at the end of a stalk.

It is a major endocrine organ secreting at least 9 hormones including growth hormone, thyroid stimulating hormone and follicle stimulating hormone to name a few. Pituitary Gland

BRAIN STRUCTURES

Corpus Callosum – is the largest commissure which by definition connect the two hemispheres of the brain. It lies superior to the lateral ventricles.

it allows the two hemispheres to coordinated function

Corpus Callosum

BRAIN STRUCTURESPons – “bridge” is

the bulge in the brainstem between the midbrain and the medulla oblongata.

Is chiefly composed of conduction fibers which complete the pathway between the higher brain centers and the spinal cord.

Pons

BRAIN STRUCTURESMedulla Oblongata –

the most inferior part of the brain stem. It blends into the spinal cord at the base.

Plays a crucial role in the autonomic reflex center. Important visceral motor nuclei include

1. Cardiovascular center2. Respiratory centers3. Additional centers that

control Vomiting, hiccupping, swallowing, coughing and sneezing.

Medulla Oblongata

BRAIN STRUCTURES

Cerebellum – “Small Brain” accounts for about 11% of total brain mass. Located dorsal to the medulla and pons.

Processes information from the cerebral motor cortex and visual and equilibrium pathways, and “instructs” motor centers which result in proper balance, posture, smooth coordinated skeletal muscle movements.

Cerebellum

BRAIN STRUCTURESThalamus – “inner room”

is a deep well hidden brain region. It contains a large number of nuclei.

Each nuclei receives and deciphers information from the cerebral cortex and other areas “relay station”. The thalamus plays an integral in mediating sensation, motor activities, cortical arousal, learning and memory.

Thalamus

BRAIN STRUCTURES

Midbrain – a conduction pathway between the higher and lower brain centers. Contains the corpora quadrigemina

Midbrain

BRAIN STRUCTURESCorpora quadrigemina –

“quadruplets” which is 4 raised dome-like protrusions on the dorsal midbrain surface.

1. Visual reflex center – coordinates head and eye movements to follow moving objects.

2. Auditory Reflex center – reflexive response to sharp sounds that cause you to turn your head towards and startling sound “startle reflex”

CorporaQuadrigemina

BRAIN STRUCTURES

Cerebrum – gray matter localizes and interprets sensory inputs.

1. Controls voluntary and skilled skeletal muscle activity.

2. Functions in intellectual and emotional processing

3. Important in initiation of skeletal muscle movements

Cerebrum

CEREBRAL LOBESFrontal Lobe

Temporal Lobe

Cerebellum

Parietal Lobe

Occipital Lobe

BRAIN STRUCTURES - VENTRICLES

Are continuous spaces which reside inside the tissue of the brain

They are continuous with the central canal of the spinal cord.

They are full of Cerebral Spinal Fluid

Brain Ventricles

BRAIN STRUCTURES - CSFCSF (Cerebral Spinal Fluid) – is

found in and around the brain and spinal cord.

It forms and liquid cushion and gives buoyancy around the CNS. The CSF reduces the weight of the brain by 97% and prevents the brain from crushing itself.

It also protects the CNS from trauma and helps nourish the brain.

BRAIN STRUCTURES - CSFChoroid Plexus –

these structures hang from the roof of the ventricles and produce CSF.

Arachnoid Villi – knob like projections which protrude through the dura mater into the superior sagittal sinus. CSF is absorbed into the venous blood of the dural sinus here.

ChoroidPlexus

ArachnoidGranulations

BRAIN STRUCTURES - VENTRICLES

1st and 2nd Ventricles

“lateral ventricles” are deep within either cerebral hemisphere.

Are large C-shaped ventricles

Foramen of Munroe –

“interventricular foramen” which attaches the lateral ventricles to the narrow 3rd ventricle

1st and 2nd Ventricles

BRAIN STRUCTURES - VENTRICLES

3rd Ventricle Thin medial ventricle

Aqueduct of Sylvius

“cerebral aqueduct” connects the 3rd and

forth ventricle3rd Ventricle

Aqueduct of Sylvius

BRAIN STRUCTURES - VENTRICLES

4th Ventricle – lies in dorsal to the pons

and superior medulla. It is continuous with the central canal of the spinal cord.

Central Canal of Spinal Cord -

Continues down the spinal cord from the ventricles of the brain.

Central Canal

4th Ventricle

HYDROCEPHALUS “Water on the brain” is a condition

where the CSF cannot be drained or reabsorbed.

CSF accumulates and exerts pressure on the brain

HYDROCEPHALUS Hydrocephalus is

treated by inserting a shunt into the ventricles to drain the excess fluid into a vein in the neck or abdomen.

BRAIN STRUCTURES - MENINGES

Meninges – “membrane” are three connective tissue membranes that lie just outside the CNS (Brain and Spinal Cord). Their functions include;

1. Cover and protect the CNS2. Protect blood vessels and enclose

the venous sinuses3. Contain CSF 4. Form partitions in the skull

BRAIN STRUCTURES - MENINGES

BRAIN STRUCTURES - MENINGES

Dura Mater – “tough mother” is the

strongest layer. Two layered sheet of

fibrous connective tissue.

Arachnoid - Forms a loose brain

covering. Separated from the dura

matter by a serous cavity “Subdural space”

The “subdural space” is filled with fluid

Dura MaterSuperior Sagittal

Sinus

Arachnoid

BRAIN STRUCTURES - MENINGES

Subarachnoid Space Web-like extensions span

this space and attach the arachnoid to the pia matter.

This space is filled with CSF and large blood vessels

Pia Mater “gentle mother” is

composed of delicate connective tissue and is full of tiny blood vessels.

This is the only layer that clings tightly to the brain following every contour.

MENINGITIS Meningitis is the

inflammation of the protective membranes covering the central nervous system (meninges)

Meningitis may develop in response to a number of causes, most prominently bacteria, viruses and other infectious agents, but also physical injury, cancer, or certain drugs Brain with Meningitis

DuraMater

SPINA BIFIDA “forked spine” results from the incomplete

formation of the vertebral arches is a developmental birth defect

involving the neural tube: incomplete closure of the embryonic neural tube results in an incompletely formed spinal cord.

the vertebrae overlying the open portion of the spinal cord do not fully form and remain un fused and open

This allows the abnormal portion of the spinal cord to stick out through the opening in the bones

3 Types1. Spina bifida occulta – not severe results in

a small tuft of hair on the back and has no neurological ramifications.

2. Spina bifida meningocele – more severe, a sac-like cyst protrudes from the child’s spine. The cyst contains CSF and Meninges.

3. Spina bifida myelomeningocele – similar to above only the cyst contains neural structures. The more neurological structures the cyst contains the more neurological impairment.

SPINA BIFIDA There is no

treatment for the neurological defects caused by spina bifida.

Doctors will perform surgery to close the vertebral column to prevent further damage and infection.

An infant with Spina Bifida