The Brain

Question 1

Human Brain size

• weight
• 2 directional terms

Answer 1

-Weight; 1.35-1.4kg
Directional terms: Rostral (toward nose)
-Caudal (toward tail)

Question 2

4 major regions of human brain

Answer 2

1. Cerebrum
2. Diencephalon
3. Brainstem (midbrain, pons, medulla oblongata)
4. Cerebellum

Question 3

Organisation of Neural Tissue areas in brain (2)

Answer 3

1. Gray Matter
   
   • houses motor neuron & interneuron cell bodies, dendrites, telodendria, unmyelinated axons
   • forms cortex which overs surface of most of adult brain
   • forms discrete internal clusters called cerebral nuclei
2. White matter:
   
   • made up of myelinated axons
   • lies deep to gray matter of the cortex

Question 4

Support & Protection of brain

• 4 roles of Cranial meninges
• 3 layers

Answer 4

• Cranial Meninges are CT layers that;
  
  • separate soft tissue of brain from bones of cranium
  • enclose & protect blood vessels that supply brain
  • contain & circulate cerebrospinal fluid
  • form some of veins that drain blood from brain

Layers; dura mater, arachnoid mater, pia mater

Question 5

Cranial meninges; layers (3)

Answer 5

1. Dura Mater
   - External tough dense irregular CT
   - 2 layers of fibrous layers which separate to form large blood fills spaces (DURAL VENOUS SINUSES - is where deoxygenated blood leaves) connects to jugular vein to drain blood from the head
2. Arachnoid Mater
   - spider web structure - collagen & elastic fibres
   - subarachnoid space between AM and PM
   - potential space between AM & DM = subdural space where subdural hematomas form
3. Pia Mater
   - innermost cranial meningeal layer
   - Thin areolar tissue, highly vascularised and adheres to the brain
   - directly in contact w/ brain -> follows grooves

Question 6

Brain Ventricles

Answer 6

-Ventricles = cavities or expansions w/in brain that are continuous w/ one another & central canal of spinal cord
-all contain cerebral spinal fluid
Are 4 ventricles;
-2 lateral ventricles, one in each hemispheres of cerebrum (separated by thin septum pellucidum)
-third ventricle in diencephalon
-fourth ventricle b/w pons and cerebellum

Question 7

Cranial Dural Septa

Answer 7

-Dural mater creates divisions w/in brain -> creates different divisions

Question 8

Cerebrospinal Fluid

• what it is
• 3 functions

Answer 8

-is a clear, colourless liquid that circulates in the ventricles & subarachnoid space
FUNCTIONS
-Buoyancy: takes 95% of brain’s weight (brain floats in CSF)
-Protection: provides liquid cushion from sudden movements
-Environmental stability: transports nutrients & removes waste from brain (involved in homeostatic properties)

Question 9

Blood-Brain Barrier

• what it does
• cells that contribute to BBB
• 3 locations where it is missing or reduced & why

Answer 9

-strictly regulates what substances can enter the interstitial fluids of brain
-Capillary endothelial cells and astrocyte perivascular feet contribute to BBB
Missing or reduced in 3 locations;
-Choroid plexus
-Hypothalamus
-pineal gland

• Choroid plexus - must be permeable to produce CSF
• other 2 = produce hormones that must have ready access to bloodstream

Question 10

Cerebrum

-what it does

Answer 10

• is location of conscious thought processes & origin of intellectual functions
• large no. of neurons that needed for complex analytical & integrative functions
• left & right hemispheres
• largest part of brain

Question 11

Cerebrum

• what formed from
• outer layer & internal layer (what matter)
• cerebral nuclei
• gyri and sulci and fissures

Answer 11

• Formed from telencephalon
• outer layer = cerebral cortex & is gray matter
  
  • internal layer = white matter
• cerebral nuclei = deep to white matter are discrete regions of gray matter
• surface of cerebrum folds into elevated ridges called gyri (contours of brain)
• Adjacent gyri separated by shallow sulci or deeper grooves called fissures

Question 12

Cerebral Hemispheres

• how many & how separated
• Corpus callosum

Answer 12

• cerebrum composed of 2 halves (left & right cerebral hemispheres)
  
  • divided by a longitudinal fissure along midsaggital plane
• hemispheres separated from each other except at few locations where bundles of axons called tracts form white matter regions that allow comm. b/w them
• Corpus Callosum: largest tract & main tract that connects the two hemispheres

Question 13

Lobes of Cerebrum (5 distinct lobes)

Answer 13

1. Frontal lobe: concentration, communication & personality
2. Parietal lobe: sensor, texture and shape
3. Temporal lobe: hearing and smell
4. Occipital lobe: processing visual information and visual memories
5. Insula: memory and taste

Question 14

Frontal lobe (Cerebrum)

• location
• boundaries
• precentral gyrus
• what involved in

Answer 14

• Located deep to frontal bone
• ends posteriorly at central sulcus - inferior border marked by lateral sulcus
• Precentral gyrus is mass of nervous tissue in frontal lobe immediately anterior to central sulcus
• involved w/ voluntary motor function, conc., verbal comm, decision making, planning & personality

Question 15

Parietal Lobe (Cerebrum)

• Where it is
• boundaries
• what involved with

Answer 15

• Forms superoposterior part of each hemisphere (underlies parietal bone)
• Terminates anteriorly at central sulcus, laterally at lateral sulcus & posteriorly at parietao-occipital sulcus
• postcentral gyrus is mass of nervous tissue in parietal lobe immediately posterior to central sulcus

*involved w/ general sensory functions

Question 16

Temporal lobe (Cerebrum)

• where located
• what involved in

Answer 16

• Located inferior to lateral sulcus underlying temporal bone
• Involved w/ hearing and smell

Question 17

Occipital lobe (Cerebrum)

• where located
• what it does

Answer 17

• Located in posterior region of each hemisphere underlying occipital bone
• Processes incoming visual information
• Stores visual memories

Question 18

Insula (Cerebrum)

• where located
• what involved in

Answer 18

• located deep to lateral sulcus

- involved in memory & interpretation of taste

Question 19

Functional areas of cerebrum (3 areas)

-what they do

Answer 19

1. Motor areas: control voluntary motor functions
2. Sensory areas: provide conscious awareness of sensation
3. Association areas: integrate and store information

Question 20

Motor Areas (3)

Answer 20

1. Primary Motor Cortex (somatic motor area)
   - controls voluntary skeletal muscle activity; located within precentral gyrus (anterior to central sulcus)
2. Motor speech area (Broca’s area)
   - controls muscular movements necessary for vocalization
3. Frontal eye field
   - controls and regulates eye movements and binocular vision

Question 21

Diencephalon - 3 components

-what they do

Answer 21

-Components include;
Epithalamus: pineal gland involved in circadian rhythms
Thalamus: filters background info before relaying it to cerebrum
Hypothalamus: controls ANS & endocrine system; regulates body temp, emotional behaviour, food intake, water intake & sleep

Question 22

Functions of Hypothalamus (7)

Answer 22

• Master control of ANS
• Master control of endocrine system
• Regulation of body temp
• Control of emotional behaviour
• control of food intake
• control of water intake
• regulation of sleep-wake (circardian) rhythms

Question 23

Brainstem

-what it does

Answer 23

• connects forebrain & cerebellum to spinal cord
• is bidirectional passageway for all tracts extending between cerebrum & spinal cord
• Contains many autonomic centers and refex centers
• houses nuclei of many of cranial nerves

Question 24

Brainstem: 3 regions

Answer 24

1. Mesencephaon: mid brain
2. Pons: Sensory & motor tracts connect brain to spinal cord
3. Medulla Oblongata: vital autonomic nuclei for regulating functions relating to;
   
   • cardiac centre (heart rate)
   • vasomotor centre (blood pressure)
   • respiratory centre (respiratory rate)
   • others (coughing, sneezing, swallowing, gagging)

Question 25

Cerebellum -folia

Answer 25

- 2nd largest part of brain - has complex, highly convoluted surface covered by layer of cerebellar cortex w/ folds called folia - left and right cerebellar hemispheres - each hemisphere = 2 lobes (anterior & posterior - separated by primary fissure)

Question 26

Cerebellum - 3 regions

Answer 26

1. An outer gray matter layer of cortex 2. Internal region of white matter, called arbor vitae 3. Cerebellar nuclei in deepest layer

Question 27

Cerebellar Functions - 3

Answer 27

- Coordinates and fine-tunes skeletal muscle movements and ensures that skeletal muscle contraction follows correct pattern leading to smooth, coordinated movement - stores memories of previously learned movement patterns - receives proprioceptive info from muscles and joints - uses this info to regulate body's position

Question 28

Limbic system - structure - what it affects

Answer 28

- structures of limbic system form a ring around diencephalon - composed of multiple cerebral and diencephalic structures that collectively process and experience emotions - affects memory formation through integration of past memories of physical sensations w/ emotional states

Question 29

Cranial nerves

Answer 29

- 12 pairs - numbered w/ roman numerals by their position (beginning w/ most anteriorly placed nerve) - names generally related to function