Lecture 1: Evolutionary History of the Brain Flashcards
How does the brain use sensory input to guide movement?
Input from sense organs -> brain -> output to muscles
What are the two main functions of the brain?
- Use sensory input to guide movement
- Use sensory input to regulare internal organs
How does the brain use sensory input to regulate internal organs?
Input from sense organs -> brain -> output to internal organs
What is the cortex?
Covers the surface of the brain
What are gyrus?
Bumps/ peaks in the cortex
What are sulcus?
Dips in the cortex
What are the names of the four lobes?
- Frontal lobe
- Parietal lobe
- Occipital lobe
- Temporal lobe
What are the names of the two gyrus?
- Precentral gyrus
- Postcentral gyrus
What is the name of the sulcus?
Central sulcus
What are the three parts the brain can be divided into?
- Forebrain
- Midbrain
- Hindbrain
What is the function of the forebrain?
Uses current sensory input and past experience to make (and communicate) decisions
What is the function of the midbrain?
Uses current sensory input to direct movement
What is the function of the hindbrain?
Maintains the current state; control mouth
What are the two systems in which the brain uses to send messages to the body?
- Nervous system
- Vascular system
What is the nervous system?
- Uses electrical signals to send messages rapidly
however communication is costly - The network structure determines which cells receive the messages
What is the vascular system?
- Uses chemical signals (hormones) so send messages slowly but cheap
- Membrane receptors determine which cells receive the message
Where did the brain come from?
- Sensory and communication systems in humans are similar to those in other animals
- Structure of the human brain is similar to that of other brains
- Theory of evolution helps us understand similarities (and differences)
When was the Earth Birth: Prokaryotic cells (no nucleus)?
3.5 to 2 billion years ago
What are prokaryotic cells?
- membrane regulates contents, produces energy and has sensors
- cytoplasm contains molecules needed for cell to work
- flagella regulate movement
- DNA regulates protein production and allows inheritance
When was the Oceons Rus: Eukaryotic cells (with nucleus)?
2 billion years ago
What are eukaryotic cells?
- DNA packaged inside central nucleus
- mitochondria produce energy
- cell membrane performsphagocytosis and secretion
- microtubule network **allows complex structure
- cilia and microvilli provide specialised sensing areas
What was Metazoa - first animals?
635 million years ago
What is metazoa?
Cells stick together after division
→ multicellularity
- differentiated tissue (specialisation)
- digestive chamber
- intercellular signalling
- sensory cells, e.g. photoreceptors
What was bilateria?
555 million years ago
What is bilateria?
- complete digestive tract with separate mouth and anus
- front end had concentration of visual, olfactory and taste sensors
- muscle
When was Cambrian Explosion: Chordates?
535 million years ago
What is Cambrian Explosion: Chordates?
- notochord and tail for movement
- neural tube for communication along body
When were vertebrates?
525 million years ago
What are vertebrates?
- bone cranium and vertebrae
- first group with tri-partite brain
When were jawed fish?
430 million years ago
What are jawed fish?
- teeth → more energy
- eye muscles for movement
- three semi-circular canals (input for stabilisation)
- cerebellum—to control stabilisation and gaze
When were mammals?
225 million years ago
What are mammals?
- differentiated teeth → more efficient digestion (but need fine motor control)
- sensory innovations: vibrissae (whiskers), improved hearing
- extended parental care → more learning
When were primates?
60 million years ago
What are primates?
- opposable thumbs for grasping
- binocular vision for focusing
- trichromatic vision for colour
When was Homo?
2 million years ago
What is Homo?
Rapid expansion of brain size in Homo erectus, but unclear why
- “expensive tissue” hypothesisbetter food → smaller gut → bigger brain?
- “social brain” hypothesiscomplex social relationships → bigger brain?
- “mating mind” hypothesisbigger brain → more attractive?
Why is there great variation in the sizes of different brain regions?
- Brain tissue has high running costs: 2% of body weight but 20% of energy
- Natural selection will favour enlargement of brain region only if it enhances survival or reproduction
- Thus brain evolution depends on an animal’s anatomy and ecology
What does the size of different brain regions tell us?
The abilities of animals
e.g. teleost fishes vs mammals - what should each be good at?
What is the size of cortical area related to?
The importance of information it processes
What is the importance of insight from other species?
Shared ancestry means that studying other animals can help us understand how our brains work
