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Topic 15: The Brain

� How does the brain develop?

� What are the subdivisions of the brain?

� What structures are derived from each?

� Gross anatomy of the brain

� What are the structures that make up the brain?

� What trends in brain evolution do we see?

� What are some important human brain

pathways?

How does the brain develop?

� Neural tube formation

� What is involved?

� Evagination to subdivide

� _________________

� _________________

� _________________

Liem et al. Fig 14-15, 14-20

How does the

brain develop?

� Further subdivision:

� Prosencephalon

� _________________

� _________________

� Mesencephalon

� Rhombencephalon

� _________________

� _________________

� Differential growth

� Species specific

� Human example

Liem et al. Fig 14-1

Brain Gross Anatomy

� Shark brain

� Remains elongate

� Each ~cephalon develops into specific structures

Liem et al. Fig 14-2

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Human Brain Gross Anatomy

� Mammalian Brain

� Saggital section

Liem et al. Fig 14-11

� More spherical

� Growth of cerebrum

� Growth of cerebellum

Human Brain Gross AnatomyRegion Structures Inputs Functions

Telencephalon • Cerebral hemispheres

• Olfactory bulb• Lateral ventricles• Hypocampus

• Olfactory • Sensory cortex• Motor cortex• Visual cortex• Auditory cortex• Spatial memory

Diencephalon • Epiphysis• Thalamus• Hypothalamus• 3rd ventricle

• Circadian rhythm• Appetite• Hormonal control• Relay info

Mesencephalon • Superior colliculus• Inferior colliculus• Optic lobe• Optic ventricle

• Optic / retina

• Eye movement• Reaching movement

Metencephalon • Cerebellum• Cerebellarventricle

• Pons

• Hearing• Lateral line

• Language• Emotion• Motor control• Equilibrium/coordination

Myelencephalon • Medulla oblongata• 4th ventricle

• Taste• Skin receptors

• Respiration• Heart rate• Blood pressure

Human Brain Gross Anatomy

� Brain coverings

� Dura mater

� Arachnoid

� Subarachnoid space

� Pia mater

� Blood-brain barrier

� Cerebrospinal fluid

� Secreted by ____________

from capillaries

� Circulates in brain ventricles

� Moves to _______________

space

� Removed by arachnoid villi

back to circulationLiem et al. Fig 14-3

What might cerebrospinal fluid be for?

Human Brain Gross Anatomy

� Circulation of cerebrospinal fluid

� _____________ & _____________� Extensions of dura mater

� Medulla oblogata is continuous with spinal cord

Liem et al. Fig 14-3

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Brain Evolution

� Olfactory bulb

� Cerebrum

� Optic lobe

� Cerebellum

� What do relative sizes of structures tell us?

� _______________

� _________________

� ___________________

Liem et al. Fig 14-4, 14-9

Shark

Frog

Alligator

Pigeon

Rabbit

Brain Evolution

Liem et al. Focus 14-2

Log Body Weight

Log Brain Weight

� Line of best fit

� Line of equal weight

� Brain weight ∝ # __________ ∝ Complexity of

behavior

� What does this tell us about the various taxa?

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Human Brain & Neural Pathways

� ___________ lobe

� Motor cortex

� Broca’s area

� Speech

� __________ lobe

� Auditory cortex

� ___________ lobe

� Sensory cortex

� ___________ lobe

� Visual cortex

Liem et al. Fig 14-15

How do sensory inputs

move to the brain?

� Ascending sensory pathways

� Generally three neurons� Receptor

� Primary sensory neuron

� 2nd order interneuron to thalamus

� 3rd order neuron to sensory

cortex

� _______________

� Tactile receptors in hands

� Sensory neuron ascends to cuneate nucleus ipsilaterally

� 2nd order neuron to thalamus

contralaterally

Liem et al. Fig 14-13

How do motor instructions

move from the brain?

� Descending motor

pathways

� _______________ tract

� Motor Cortex

� To nuclei of cranial nerves

� Muscles

� _______________ tract

� Motor Cortex

� To spinal cord

� Muscles

Liem et al. Fig 14-20

How is information moved within the brain?

� Cortical integration

� Association areas are between sensory and motor cortex

� Interneurons connect association areas of the brain

� _______________ fibers

� Long association fibers

� _______________ fibers

� Corpus callosum

Liem et al. Fig 14-20

Cortical

Integration

� Coordination

between right and left

� Ipsilateral

connections

� Contralateral

connections

Liem et al. Fig 14-16