Unit 1D: The Central Nervous System Protective Tissues • The CNS consists of the brain and spinal cord • The CNS is surrounded by layers of protective tissue known as the meninges. – Swelling of the meninges due to bacterial or viral infection is known as meningitis. CSF and the Ventricles • The brain has a series of internal chambers that make and distribute CSF. They are known as the ventricles. • CSF is made from blood in the ventricles and resembles blood plasma • The CSF: – Supports weight of brain (makes it neutrally buoyant) – Cushions it (protects from injury) – Maintains chemical balance • If there is a blockage to the draining of the CSF, brain damage can result Spinal cord • Long cable of axons that connects the brain to the peripheral nervous system. • Runs down the inside of the vertebral column • Size: – As thick as your pinkie finger – Only 2/3 the length of the vertebral column (17-18in) • Function – Carries information through motor neurons from brain to muscles and glands – Carries information through sensory neurons from sense organs to brain – Creates some reflexes Spinal Nerves (PNS) • Nerves branch off of the spinal cord at each vertebral joint. • These nerves follow blood vessels and carry sensory and motor neuron axons • The extent of damage from injury can be determined by location of injury Hindbrain • The hindbrain is responsible for lifesaving functions common to all vertebrates. • Major areas: – Cerebellum • Receives visual, auditory, vestibular and somatosensory information and coordinates it. • Works to make muscle movement smooth and coordinated. Hindbrain (cont) – Pons • Involved in sleep, respiration, swallowing, bladder control, hearing, equilibrium, taste, eye movement, facial expressions, facial sensation, and posture • Also controls switch from inhalation to exhalation • Damage to this area can lead to “locked-in syndrome” – Aware and awake but unable to communicate! Hindbrain (cont) – Medulla • Regulates vital functions such as breathing, heart rate, blood pressure, etc. • It is the brain’s connection to the spinal cord. Midbrain • Functions: – primary processing of auditory and visual information (before it is passed to thalamus and cortex) • In lower vertebrates, these are the only processing areas. – Motor functions – Species-typical behaviors – Sleep/arousal Forebrain • Thalamus – Major relay center of information coming into the brain from the senses – Regulates states of sleeping and wakefulness Forebrain • Hypothalamus – rests below the thalamus and above the pituitary – It is the link between the autonomic nervous system and the endocrine system – It is responsible for maintaining homeostasis • hunger, thirst, body temp, sleep Forebrain • Basal Ganglia – Involved in movement selection and initiation – Allows muscles to relax in motion Forebrain • Amygdala – Responsible for fear, aggression, emotion • Hippocampus – Responsible for formation of longterm memories Forebrain • Cerebrum: – Largest part of human brain (most evolved) – Where conscious “thinking” takes place • Cerebral Cortex – Outer 3mm of cerebrum (surface area = 2.5ft2) – Highly convoluted (2/3 of area is in folds) – Mostly made of cell bodies of neurons (grey matter) • The rest of the cerebrum is made of the myelinated axons of these neurons and the fat makes this area look white - “white matter” Regions of the Cortex • In all cases: – the “primary cortex” area for a sense receives input directly from sense organs • Damage causes loss of sense – The “association areas” get input from primary cortex areas and process it. Also where memories tied to those senses are stored. • Damage causes loss of understanding – With the exception of taste and smell, the cortex receives information from the contralateral side of the body Regions of the Cortex • Visual Cortex and Association Area – Sight • Auditory Cortex and Association Area – Sound • Motor Cortex and Prefrontal Cortex (Motor Assoc. Area) – Controls movement and planning for movement – Specific areas control specific body parts. Regions of the Cortex • Somatosensory Cortex and Association Area – Strip that transects the cerebrum is divided into areas that respond to specific body parts (touch, feel, etc.) – The more input and processing required for a region, the more area it is given – Tongue/mouth and thumb/hand get most Regions of the Cortex • The Cerebral Cortex is often divided in lobes based upon the bones on top of the areas: – Frontal lobe • Higher thinking, morality, decision making – Parietal Lobe • Integrates sensory info and determines spatial sense and navigation – Temporal Lobe • Auditory and visual processing, speech and long-term memory – Occipital Lobe • Vision and dreams Regions of the Cortex Some tasks are shared equally by the hemispheres, and some tasks are lateralized. Each hemisphere has a majority of responsibility for the following: • Left: – – – – – – – Sequence Analysis Details Talking Understanding Reading Writing • Right – Synthesis – Perceiving shape and size – Read maps – Building objects – Creativity The Corpus Callosum bridges the gap between the two hemispheres.