Lecture 4 - The Brain

What is the brain protected by?

- Cranial bones
- Cranial meninges

What is the function of the meninges?

- To protect and support the brain
- Prevent the spread of infection
- Hold the cerebrospinal fluid

Name the three cranial meninges

1. Dura mater
2. Arachnoid mater
3. Pia mater

Describe the function of the dura mater

Helps hold the brain in place
Outermost layer

Describe the arachnoid mater

Middle layer
Spider web like appearance

Describe the pia mater

Innermost layer
Thin and transparent
Lies directly on the surface of the brain

Name the space in between the pia mater and the arachnoid mater where the cerebrospinal fluid circulates

Subarachnoid space

How does blood flow to and from in the brain?

To the brain via blood vessels that branch from the cerebral arterial circle at the base of the brain
Return blood from the head to the heart via veins

What can a lack of oxygen to the brain result in?

Weakening, permanent damage or death of brain cells

What % of the body's oxygen supply is used by the brain?

20%

What can glucose deficiency cause?

- Mental confusion
- Dizziness
- Convulsions
- Unconsciousness

Describe the function of the blood brain barrier

- Protects brain cells from harmful substances and pathogens
- Serves as a selective barrier to prevent passage of many substances from the blood into the brain
- May prevent entry of drugs as therapy for brain cancer or other CNS disorders

What cannot reach the CSF?

Metabolic waste - urea, creatinine
Toxins

What is pumped into the CSF?

- Nutrients
- Some amino acids
- Electrolytes

What can an injury to the brain due to trauma, inflammation or toxins cause?

Breakdown of the blood brain barrier permitting the passage of normally restricted substances into the brain tissue

What is the cerebrospinal fluid formed by?

Filtration from networks of capillaries called choroid plexuses located in the ventricle walls

What do the ependymal cells form and control?

- Form a blood-CSF barrier
- Controlling substances passing from the blood to CSF

State the function of the cerebrospinal fluid

- Provided mechanical and chemical protection
- Circulates essential nutrients

Describe the cerebrospinal fluid flow

Label the diagram

Describe the cerebrum

- Largest part of brain 83%
- Longitudinal fissure split into left and right cerebral hemispheres
- Each cerebral hemisphere divided into lobes
- Surface is grey matter, deeper is white matter
- Surface is convoluted to increase surface area
- Conscious brain
- Gyri and sulci - big sulci distinguishes between different lobes

Name the four lobes of the cerebrum

1. Frontal
2. Parietal
3. Occipital
4. Temporal

Describe the frontal lobe

- Largest lobe
- Found at the front of the brain
- Separated from the parietal lobe by central sulcus
- Separated from the temporal lobe by the lateral sulcus
- Includes the primary motor cortex, premotor cortex, primary olfactory cortex and Broca's area

What is the function of the frontal lobe?

The 'mind' with higher order functioning and memory and control of voluntary movements

Describe the parietal lobe

- Separated from the occipital lobe by the parietal-occipital lobe
- Main somatic sensory area
- Taste sensation
- Includes Wernicke's area

What is the function of the parietal lobe?

Integrated sensations necessary to cary out complex maths, reading, writing and visual skills

What is the hypothalamus responsible for?

- Controls the sleep-wake cycle
- Maintains body temperature at 37C
- Monitors satiation, hunger and thirst
- Regulated the autonomic nervous system
- Influences emotions and sexual activity
- Controls hormonal output of pituitary gland

What does the pineal gland do?

Regulates body clock through release of melatonin

Why are the basal ganglia important?

- Coordinate muscle movement and posture
- Suppress unwanted movements
- Control muscle tone

Describe the limbic system

- Positioned deep in the brain
- Series of nuclei that affect emotion, memory and the learning process
- Includes cerebrum, brainstem and diencephalon