The Central Nervous System SBI4U

The Central Nervous System Consists of the brain and the spinal cord. These organs are protected by: 1) skull and vertebrae 2) cerebrospinal fluid cushions the brain and spinal cord 3) meninges are protective membranes that surround the CNS

The Spinal Cord Contains interneurons that link the sensory and motor pathways. These neurons carry information to and from the brain. The spinal cord contains 31 segments, each of which has a pair of spinal nerves. The spinal cord contains white matter (bundles of myelinated axons of sensory and motor neurons), and grey matter (unmyelinated interneurons and the dendrites of motor neurons).

Cerebrospinal fluid = surrounds CNS (brain and spinal cord); acts as a sock absorber and transport medium (nutrients, chemicals, removal of wastes, etc) is a connection between CNS and endocrine system

The Brain The human brain contains three distinct areas: the forebrain, the midbrain, and the hindbrain. is protected by the skull and meninges (a protective three layer thick membrane that surrounds the brain and spinal cord) meninges controls which chemicals can ultimately reach the brain

The meninges (membrane) covers the surface of the cerebrum The most common symptoms of meningitis are headache and neck stiffness associated with fever Meningitis is diagnosed using a technique called lumbar puncture

The meninges is composed of 3 membranes; the dura mater, the tough outer membrane that adheres to the skull The arachnoid, the weblike middle layer that reabsorbs cerebrospinal fluid; And the pia mater, the innermost layer that contains many blood vessels and closely covers the brain and spinal cord

Which region is responsible for vision? Which is responsible for hearing?

Sections of the Brain Forebrain: reason, intellect, memory, language, and personality information on right side does not = info on left generally on right (visual patterns or spatial awareness) generally on left (verbal skills) hemispheres are joined by a bundle of nerves called corpus collosum = allows communication between hemispheres

SectionsFunction Olfactory lobes  (x2) process information about smell Cerebrum  2 hemisphere; largest and most developed  coordinates sensory info & motor actions  largest and most developed  divided into four (4) lobes (see below) Cerebral Cortex  surface of cerebrum  made of grey matter  highly folded (deep folds = fissures)

Why is the frontal lobe called frontal?

cerebrum is composed of 2 hemispheres What forms the largest part of the brain?

The grey matter of the human cortex is less than 5 mm thick, but in mass makes up more than 80% of the brain.

The central fissure extends from the top of each cerebral hemisphere to the lateral fissure

Midbrain: located directly below cerebral cortex relay center for eye and ear reflexes SectionsFunction Thalamus  integrative center connecting many different parts of the brain together Hypothalamus  master control center of automatic nervous system (ANS)  integrates the ANS and endocrine system Hippocampus  short term memory Basal Ganglia  many parts; responsible for crude motor movements  injury leads to rigidity, Parkinson’s and Huntington’s disease  mediates emotional feelings  mediates between forebrain & hindbrain

The Hindbrain: SectionsFunction Medulla Oblongata  joins spinal cord to cerebellum  controls involuntary muscle action  coordinating centre for the ANS  e.g breathing, heart rate, blood vessel activity, swallowing, vomiting, digestion…) Pons “bridges”  acts as relay station by sending nerve messages between the cerebellum and medulla Cerebellum  controls limb movements, balance and muscle tone  e.g. walking, hand-eye coordination, etc)

Cerebellum What does convoluted mean? Damage to the cerebellum can lead to: loss of coordination of motor movement

brain stem basic attention, arousal, and consciousness

The frontal lobe: higher intellect, foresight and judgment, primary motor area and motor area for speech

The parietal lobe: touch, temperature, and taste, and association areas for emotions, reading, and interpreting speech

Temporal: smell, hearing and auditory association areas

Occipital: vision and visual association areas

The corpus callosum contains nerve fibers that connect the right and left sides of the brain

The corpus callosum is white because it consists of myelinated nerve fibres. Sheep

The medulla oblongata controls heart and breathing rates and vasomotion (the dilation and constriction of blood vessels) to ensure blood is distributed more to active tissues than inactive ones. sheep

The pons is an important relay center for sensory and motor nerve fibers connecting the medulla oblongata and the cerebellum The pons also stimulates exhalation during prolonged inhalation of breath-holding.

The hypothalamus is an important center for the homeostatic regulation of several activities. It produces the hormones oxytocin and antidiuretic hormone secreted by the posterior pituitary gland. Other functions include the regulation of body temperature, water retention, appetitie, digestive secretions, sexual activity, and emotions such as fear and rage.

A physician makes an incision completely through the corpus callosum. How might this affect the patient? The right and left sides of the brain will not be able to communicate. “the left hand does not know what the right hand is doing” Has been considered as a treatment for severe cases of epilepsy

Phineas P. Gage (July 9?, 1823–May 21, 1860) was a railroad construction foreman now remembered for his incredible survival of an accident which drove a large iron rod through his head, destroying one or both of his frontal lobes.

Magnetic resonance imaging Magnetic resonance imaging (MRI), or Nuclear magnetic resonance imaging (NMRI)