Unit 4: The Brain s1

Unit 4: The Brain

• The human central nervous system forms around 2 weeks after conception.
• At birth, the average human brain weighs 350 grams. By the end of the first year, it weighs 1000 grams, close to the adult weight of 1200-1400 grams.
• The brain and spinal cord initially form as folds around a fluid-filled canal.
• Brain development stages occur around 2-3 weeks.
• The developing nervous system requires neuron production and alteration.
• Neuroscientists identify these processes as: proliferation, migration, differentiation, myelination, and synaptogenesis;
• Proliferation: New cell production.
• Migration: Neuron movement to its final location in the brain.
• Differentiation: Axon and dendrite formation, giving neurons distinctive shapes.
• Myelination: Glia create insulating fatty sheaths to accelerate transmission in vertebrate axons.
• Synaptogenesis: Synapse formation.
• The brain and spinal cord comprise the central nervous system; they are the main organs of the nervous system.
• Conscious experiences arise from neural activity in the brain.
• Brain-scanning techniques offer a view into the working brain.
• Brain imaging techniques allow study of internal brain workings without opening the skull.
• Key brain-scanning techniques include EEG, PET, fMRI, and TMS.
• The brain and spinal cord have multiple protective layers called meninges.
• The outermost layer is the dura mater, a tough membrane.
• Inside the dura mater is the arachnoid membrane, a web-like tissue.
• The subarachnoid space contains cerebrospinal fluid and blood vessels.
• The innermost layer is the delicate pia mater, adhering to brain surfaces.
• The central core ("old brain") controls basic functions like eating, sleeping, and common to all vertebrates.
• The hindbrain includes the medulla (responsible for breathing and heartbeat), pons (motor information transmitter/coordinator), and cerebellum (body coordination).
• The pons is also involved in regulating sleep.
• The reticular formation is composed of networks influencing arousal and sleep stages.

Parts of the Brain

• Thalamus: Primarily relays sensory information.
• Hypothalamus: Maintains homeostasis and regulates survival behaviors (eating, drinking, sexual behavior).
• Cerebellum: Responsible for coordination and balance.
• Brainstem: (includes midbrain, medulla, and pons) controls largely unconscious functions like heartbeat and breathing.
• Cerebral Cortex: The "new brain", responsible for complex processing.
• Corpus Callosum: Connects the two cerebral hemispheres.
• Amygdala: Involved in processing emotions.
• Hippocampus: Involved in memory.
• Pituitary Gland: Regulates other endocrine glands.

Development of the Brain

• The brain develops in three initial swellings (cephalon) that later form five divisions.
• These divisions are telencephalon (cerebral hemispheres), diencephalon, mesencephalon (midbrain), metencephalon, and myelencephalon (medulla).