The Human Brain: Structure and Function PDF

The Human Brain: Structure and Function The human brain comprises 3 regions: the forebrain, the midbrain, and the hindbrain. This presentation will explore the structure and function of these regions, highlighting the unique characteristics that make the human brain a marvel of biological engineerin...

The Human Brain: Structure and Function The human brain comprises 3 regions: the forebrain, the midbrain, and the hindbrain. This presentation will explore the structure and function of these regions, highlighting the unique characteristics that make the human brain a marvel of biological engineering. by Anika Khanna Evolutionary Trends in Brain Development Forebrain Size Brain-to-Body Ratio In comparing birds and mammals with other groups that Second, birds and mammals have much larger brains diverged from a common ancestor earlier in evolution two relative to body size than other groups. These differences trends are evident. First, the forebrain of birds and mammals reflect the greater capacity of birds and mammals for occupies a larger fraction of the brain than it does in other cognition and higherorder reasoning. vertebrates. The Cerebrum: The Largest Part of the Brain Structure Grey and White Matter The cerebrum is the largest part of the brain. It is split In preserved brains, the outermost layer of the into 2 hemispheres by a longitudinal fissure and divided cerebrum has a grey color, hence the name "grey into 4 lobes: frontal, temporal, parietal and occipital. matter". Grey matter is formed by neurons and their unmyelinated fibers, white matter below the grey matter of the cortex is formed from myelinated axons. The Cerebral Cortex: The Brain's Outer Layer Structure Function The cerebral cortex is the The cerebral cortex is vital for outer layer of cerebrum. Its perception, voluntary surface is very convoluted movement and learning. It resulting in a large surface consists of associative, motor area which is necessary to and sensory cortex. contain over 10 billion nerve cells. Associative Cortex Comprises 75% of the surface area of the cerebral cortex. It is the site of mental activities such as planning, conceptualization, contemplation and associative memory. It is linked to intellectual activities and personality. Humans have the highest proportion of associative cortex in animal kingdom. Motor and Sensory Cortex Motor Cortex Sensory Cortex The motor cortex is a narrow band of nerve tissue in front of The sensory cortex lies in a band behind the motor cortex. It central fissure that controls the voluntary movement of the receives input from sense organs (eyes, nose, tongue, or skeletal muscles. Body parts involved in many subtle ears) or messages of touch and temperature from anywhere movements (fingers, tongue, lips) have a larger proportion in the body. of the brain devoted to their control. Impulses from motor nerves affect muscles on the side of the body opposite to the side of the brain from which the impulse travels. For example, a stroke on one side of the brain affects operation of the opposite side of the body. In the somatosensory cortex and motor cortex, neurons are arranged according to the part of the body that generates the sensory input or receives the motor commands. The cortical surface area devoted to each body part is not proportional to the size of the part. Instead, surface area correlates with the extent of neuronal control needed (for the motor cortex) or with the number of sensory neurons that extend axons to that part (for the somatosensory cortex). Corpus Callosum and Thalamus Corpus Callosum Thalamus The corpus callosum is a bundle of The thalamus is located below the nerves allowing communication cerebrum. It is the main input between both hemispheres. Each center for sensory information hemisphere of the cortex receives (receiving sensations of touch, information from the opposite side pain, heat, cold) going to the of the body. cerebrum. Hypothalamus and Pituitary Gland Hypothalamus Located below the thalamus, it acts as the main control center for the autonomic nervous system, therefore 1 initiating the fight or flight response. It is involved in maintaining body temp., hormone concentration, the intake of food and water, the response to pain & reproductive behavior. Pituitary Gland 2 Attached to the hypothalamus, the pituitary gland produces hormones that have an effect on many other endocrine glands. The Midbrain: A Sensory Integration Center Function Structure The midbrain receives and It is a short segment of the integrates several types of brainstem involved in sight sensory information and and hearing. sends it to specific regions of the forebrain. The Hindbrain: Cerebellum and Brain Stem Cerebellum Largest section of the hindbrain, controls limb movements, balance, and muscle 1 tone. Brain Stem 2 Consists of the medulla, pons, and midbrain, connecting the forebrain to the spinal cord. Pons 3 Acts as a relay station and participates in regulating breathing. Medulla Oblongata 4 Controls involuntary muscle actions and coordinates the autonomic nervous system. The Brain Stem: Pons and Medulla Oblongata Pons Medulla Oblongata "Pons" means bridge, a relay station that passes information The medulla oblongata also acts as the coordinating center between the peripheral nervous system and the brain. It for the autonomic nervous system. It controls involuntary participates in some of the activities under the medulla's muscle action such as breathing, diameter of blood vessels control such as regulating the breathing centers in the digestion and heart rate. medulla.