Transcript Brain Notes
4 major parts of the brain • 1) Cerebral Hemispheres • 2) Diencephalon • 3) Brain Stem • 4) Cerebellum • Contains 100 billion neurons!!!! How is the brain protected • Meninges – A connective membrane covering the CNS. There are 3 layers • 1. Dura Mater (tough mother) – outermost layer. Tough, dense irregular connective tissue that helps protect. • 2. Arachnoid Mater (spider mother) – middle layer. An arrangement of collagen and elastic fibers (resembles a spiders web). • 3. Pia Mater (gentle mother) – inner layer. A layer of collagen and elastic fibers that adheres to the surface of the spinal cord and brain. Contains numerous blood vessels. Diseases of the meninges • Meningitis: Inflammation of the meninges caused by a bacteria or virus • Encephalitis: brain swelling caused by an increase in cerebral spinal fluid • In the news this weekend….a warning for pregnant women traveling to Mexico and the Carribean • Zika virus (transferred from mosquitos) – microcephaly Cerebrum • Gives us the ability to read, write, speak, make calculations, compose music, remember the past, plan for the future, create. • During embryonic development, there is a rapid increase in brain size. The gray matter enlarges much faster than the underlying white matter. As a result, the cerebral cortex rolls and folds so it may fit into the cranial cavity. The folds are called Gyri. The deep grooves between the folds are fissures, the shallow grooves (on the surface of the cortex) are sulci. Cerebrum • The cerebrum is divided into 2 hemispheres. The longitudinal fissure separates the left from the right hemisphere. The corpus callosum connect the hemispheres internally. • It has 4 lobes • Frontal - concentration & problem solving • Parietal - speech, motor, sensations • Temporal - interprets & remembers visual and auditory patterns • Occipital - visual area How do the left & right hemispheres work? • The Left side of the brain controls the Right side of the body • The Right side of the brain controls the Left side of the body. • Dominant Hemisphere: 90% Left (Language, Speech, Reading, Writing, and Analytical skills) Cerebellum • Located posterior to the medulla and pons and below the cerebrum • It regulates posture and balance and is essential for all skilled motor activities (ex. Catching a baseball, dancing). • Ataxia (a – without, taxia – order) – a condition that disrupts muscle coordination. Can be caused by trauma or disease. People who consume too much alcohol show signs of ataxia because alcohol inhibits activity of the cerebellum. Alcohol overdose also suppresses the medullary rhythmicity area and may result in death. Brain Stem • Consists of 3 regions • Medulla oblongata • Pons • midbrain Medulla Oblongata • A continuation of the spinal cord • Regulates the rate and force of the heartbeat, the diameter of blood vessels and the basic rhythm of breathing. • Also controls: swallowing, vomiting, coughing, hiccupping and sneezing. • A hard blow to the medulla can be fatal • Cardiovascular center located here Pons • It is a part of the brain stem • Above the medulla and anterior to the cerebellum • A bridge that connects parts of the brain with one another through bundles of axons. Midbrain • Connects the pons to the diencephalon • Anterior part of the midbrain consists of a pair of large tracts called cerebral peduncles. They conduct nerve impulses from the cerebrum to the spinal cord, medulla and pons. Also contains axons of sensory neurons from the medulla to the thalamus. • Loss of neurons in this area is associated with Parkinson’s disease Diencephalon • Located above the brain stem • Made up of the thalamus (motor functions, autonomic activities and the maintenance of consciousness and relays nerve impulses between different areas of the cerebrum), hypothalamus (see next slide), and pineal gland (secretes the hormone melatonin which promotes sleepiness and contributes to the setting of the body’s biological clock). Hypothalamus • Regulates contraction of smooth (movement of food through GI tract and contraction of urinary bladder) and cardiac muscle (heart rate) and secretions of glands • Controls pituitary gland and production of hormones. Is the connection between the nervous and endocrine system. • Works with the limbic system (forebrain – “emotional brain” emotion and behavior) regulates feelings of rage, aggression, pain, pleasure and behavioral patterns related to sexual arousal. Hypothalamus • Regulates eating behavior and contains thirst center • Controls body temperature • Regulation of circadian rhythms and states of consciousness – patterns of awakening and sleep the occur on a circadian (daily) schedule • See page 249 Focus on Wellness • Caffeine • Found naturally in over 60 plants • In coffee, tea, cola, over the counter drugs and in chocolate • Average coffee drinker drinks 3 cups/day • A moderate amount is only 2 cups/day • Causes: increases heart beat….beats faster and harder, muscle twitches, anxiety, increased blood pressure, irregular heart beat, difficulty sleeping Spinal Cord • In adult it is from 42 – 45 cm • Extends from the medulla oblongata to the second lumbar vertebra • Spinal tap – long needle inserted into the subarachnoid space. • Into the lowest portion of the spinal cord….relatively safe • Used to withdraw cerebrospinal fluid for diagnostic purposes, introduce antibiotics or anesthetics and treatment for diseases such as meningitis Spinal Nerves • 31 pairs of spinal nerves • Plexus – a network of spinal nerves the divide into branches • Cervical plexus – supplies the skin and muscles of the head, neck, upper shoulders and diaphragm • Brachial plexus – nerve supply for the upper limbs, neck and shoulder muscles • Lumbar plexus – abdominal wall, external genitals and part of the lower limbs • Sacral plexus – buttocks and lower limbs, sciatic nerve Brain • Memory – the process by which information acquired through learning is stored and retrieved • Brain waves – electrical signals • EEG – electroencephalogram – records brain waves to study brain function. Used to diagnose brain disorders like epilepsy, tumors, trauma, and degenerative diseases Aging • The brain grows rapidly during the first few years of life. From early adulthood onward, brain mass declines. Although the number of neurons present does not decrease very much, the number of synaptic contacts declines. As a result, the processing of information diminishes. Conduction velocity decreases, voluntary motor movements slow down, and reflex times increase. Common Disorders • Spinal Cord Injury – due to trauma from auto accidents, falls, contact sports, diving, or acts of violence. Most common sites of injury are in the cervical, lower thoracic, and upper lumbar regions. • Diplegia – (di – 2) paralysis of both upper limbs or both lower limbs • Paraplegia – paralysis of both lower limbs • Quadriplegia – paralysis of all four limbs Common Disorders • Shingles – caused by the herpes zoster virus that also causes chickenpox. If the virus is reactivated, it may leave the ganglion and travel down sensory axons to the skin. The result is pain, discoloration of the skin, and a characteristic line of blisters. • ALS – Lou Gehrig’s disease Common Disorders • Polio – can cause death from respiratory or heart failure, causes paralysis. Even though polio vaccines have virtually eradicated polio in the US, outbreaks of polio continue throughout the world. Due to international travel, polio could easily be reintroduced into North America if individuals are not vaccinated appropriately. • Parkinson Disease – A progressive disorder of the CNS that affects the neurons that extend from the substantia nigra where the neurotransmitter dopamine is released. Involuntary tremors are a common symptom. Medical Terms • Analgesia – pain relief • Anesthesia – loss of sensation • Epidural block – injection of an anesthetic drug into the epidural space, between the dura mater and vertebral column, to cause a temporary loss of sensation (ex. During child birth)