Option A.2 The Human Brain

Development of the Brain Occurs at the anterior portion of the neural tube Process is called cephalization Brain and spinal cord make up the central nervous system Nerves that branch from CNS make up the Peripheral nervous system (PNS) PNS divided into two parts Autonomic NS (involuntary) Somatic (voluntary)

Sympathetic VS. Parasympathetic NS Controlled response Sympathetic (fight or flight) Parasympathetic (rest and digest) Heart rate Speeds up Supplies more blood flow to body muscles to prepare for increased muscle contraction Slows down Returns heart rate to normal after stressful situation to allow body to rest and recover Breathing Increases O2 supply to meet increased demands of contracting muscles Returns breathing to normal after a stressful situation Iris Dilates pupil (circular muscle) More light available for optimal vision Constricts pupil (radial muscle) Constricts pupil back to normal based on availability of light Digestion (blood flow to gut, saliva production, production of gastric juices Decreases Less energy is used for digestion so more is available to meet the increased need for muscle contraction Increases More energy used for digestion to replace the stored energy lost in order to be prepared for future needs

Human Brain Structures

Human Brain Structures & Functions Medulla oblongata Controls breathing and heart rate Regulates digestion Controls vomiting reflex Cerebellum Controls movement and balance Hypothalamus Coordinates actions of the endocrine & nervous system Produces some of the hormones stored in the pituitary Controls the release of pituitary hormones Maintains homeostasis Temperature regulation Blood glucose levels Blood solute concentration (osmoregulation) Pituitary gland (anterior & posterior) Stores & releases hormones when stimulated by Hypothalamus Cerebral hemispheres Control higher-level functions such as learning, emotions, problem solving and personality

Cerebral Cortex Largest structure in the brain More highly developed in humans than other animals Divided into two hemispheres Contains extensive folding (to fit) Higher order functioning Learning Memory Speech Emotions

Humunculus Model of the body in which the size of each part corresponds to the proportion of somatosensory cortex and motor cortex

Cerebral Cortex

Cerebral Hemispheres Left Cerebral Hemisphere (right-hand controlled) Right Cerebral Hemisphere (left-hand controlled) Involved in scientific and mathematical skill (reasoning and analytical) Receives visual information from sensory receptors on the right side of the body Controls muscle contractions on the right side of the body Involved in creative and imagination (artistic and musical) Receives visual information form sensory receptors on the left side of the body Controls muscle contractions on the left side of the body

Specific Areas of Brain Functions Brain region Specific functions Visual cortex Interpret visual stimuli Flips image input to upright visuals Plays a role in producing images of memories & imagination Broca’s area Language Language comprehension Possible role in body gesture-word relationship Wernicke’s area Speech Understanding the spoken language Nucleus accumbens Reward pathway Dopamine release

Pupil Reflex Controlled by medulla oblongata Circular muscle contract iris Radial muscle constrict iris Allows proper amount of light into the eye so as not to harm the eye

Pupil reflex and Brain Death Bright light shone into each eye If pupils do no constrict at once it is an indication of damage to the medulla oblongata

Energy and the Brain Brain metabolism requires large energy inputs Has large numbers of neurons so it requires lots of oxygen Adult human brains use 20% if basal metabolism, this number is even higher in infants and small children

Methods of research Animal experimentation Lesions Surgical procedures Drug use Lesions Physiological loss of functioning Functional magnetic resonance imaging (fMRI) Measure amount of blood flow to the brain Can be compared to a normal brain Autopsy Can be compared in patient prior to death or normal patients